Ebook Noninvasive mechanical ventilation and difficult weaning in critical care: Part 2

Use of Noninvasive Mechanical
Ventilation in Lung Transplantation

27

Ana Hernandez Voth, Pedro Benavides Mañas,
and Javier Sayas Catalán

Abbreviations
CF
COPD
CPAP
ETI
FEV1
ICU
ILD
LT
NIV

27.1

Cystic fibrosis
Chronic obstructive pulmonary disease
Continuous positive airway pressure
Endotracheal intubation
Flow expiratory volume in the first second
Intensive care unit
Interstitial lung disease
Lung transplantation
Noninvasive mechanical ventilation

Introduction

Lung transplantation (LT) is a consolidated therapeutic strategy in cases of end-stage
pulmonary diseases such as chronic obstructive pulmonary disease (COPD), diffuse
interstitial diseases, or vascular diseases. Noninvasive mechanical ventilation (NIV)
is one of the ventilatory support techniques that has achieved greater use in recent
years, becoming available at most hospitals and being successfully implemented in
intensive care units (ICUs), intermediate care units, and recovery units. In this chapter, the role of NIV in the management of lung transplant patients in the pretransplant
period, in the early postoperative period, and with LT complications, or to carry out
diagnostic and therapeutic techniques in transplant patients, is reviewed.

A. Hernandez Voth, MD (*) • P. Benavides Mañas, MD • J. Sayas Catalan, MD
Pulmonology Service, Hospital Universitario 12 de Octubre, Madrid, Spain
e-mail: ; ;
© Springer International Publishing Switzerland 2016
A.M. Esquinas (ed.), Noninvasive Mechanical Ventilation and Difficult Weaning
in Critical Care: Key Topics and Practical Approaches,
DOI 10.1007/978-3-319-04259-6_27

213


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A. Hernandez Voth et al.

Discussion and Analysis

27.2.1 NIV in LT Indication Diseases
Many candidates for LT have a chronic domiciliary NIV indication as part of their
underlying lung disease treatment. There is evidence of NIV benefit as a bridge to
LT in two obstructive pathologies: COPD and cystic fibrosis (CF).
COPD exacerbation is a situation where the use of NIV has a higher degree of
evidence, particularly in severe exacerbations that develop respiratory acidosis.
These exacerbations are frequent in patients with COPD on the waiting list for LT,
and NIV can decrease mortality in up to 50 % cases of COPD exacerbation with
respiratory acidosis when compared with standard treatment [1]. This impact on survival is much higher than that obtained from any of pharmacological treatments used
in COPD exacerbations, and it has a high degree of evidence to be recommended.
NIV usefulness in stable COPD is more controversial. In patients with chronic
hypercapnic respiratory failure, several studies with contradictory results have been
published. Some of them show a slight increase in survival of patients with COPD
with hypercapnic respiratory insufficiency, whereas others have not found any differences in terms of exacerbations or survival. Nevertheless, although there is no
conclusive scientific evidence about its usefulness in stable COPD, it is one of the
main indications of chronic domiciliary NIV in Europe.
Regarding the use of NIV in COPD as bridge to LT, an improvement in a pulmonary function parameter (an increase of 0.20 ± 0.18 l (liters) in FEV1) has been
described, along with a small increase in survival while on the waiting list for LT
[2]. However, these are limited data because of the absence of a control group and
the presence of important selection bias in their results. Functional improvement
has been achieved in very severe COPD by using NIV prior to an oncologic thoracic
surgery, which can be extrapolated to very severe COPD patients on the waiting list
for LT.
NIV in CF patients has shown short-term improvement in oxygen saturation and in
pCO2 levels, as well as a decrease in the work of breathing, alveolar ventilation and
exercise tolerance improvement, and pulmonary function stabilization during rehabilitation [3, 4]. When these patients have a severe exacerbation that requires ventilatory support, invasive mechanical ventilation has a bad prognosis associated with
infectious complications from frequent bronchial colonization, as ventilator-associated
pneumonia. As a bridge to LT, NIV in CF can reduce mortality from this cause.

27.2.2 NIV in the LT Early Postoperative Period

Generally, after thoracic surgery there are strong effects on respiratory function that
relate to postoperative prolonged mechanical ventilation requirements. In the particular case of LT, there are also other associated factors: the usual myopathy that
terminal respiratory insufficiency patients present, functional alterations due to
clamshell incision in bilateral LT, and postoperative diaphragm involvement due to
phrenic nerve damage.


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NIV use has been considered in the LT early postoperative period with three
major objectives: to facilitate early extubation, to prevent reintubation due to postsurgery ventilatory failure, and to treat ventilatory failure once it is established [5].

27.2.2.1 NIV as a Tool in Early Extubation
Early extubation is of particular interest in immunosuppressed patients to avoid
infectious consequences of prolonged mechanical ventilation, but also to avoid airway complications. Prolonged mechanical ventilation can lead to barotrauma on the
sutures associated with air leakage, modifying pulmonary defense mechanisms and
leading to bronchial anastomosis infection.
Consequences of reintubation due to postsurgical ventilatory failure may result
in a remarkable increase of mortality.
Hypoxemia, hypercapnia and muscle fatigue due to an increase in breathing
work are the most common causes of failed extubation. Furthermore, at the time
of extubation, there is a loss of the intrathoracic positive pressure maintained so
far. This induces hemodynamic changes, increasing venous return to the right
ventricle, left cardiac septum displacement, and a possible increase in pulmonary
artery pressure and pulmonary capillary wedge pressure. All these events can
result in the development of interstitial pulmonary edema and in a higher expiratory work. Pressure support associated with some degree of positive end-expiratory pressure can offset these effects, even applying ventilation in the noninvasive

mode.
NIV can represent a helpful tool in extubation of patients who do not succeed a
T-tube trial. Thus, early weaning protocols have been developed in LT including
epidural analgesia, early seating position, intensive physiotherapy, and NIV [6].
In our experience, we have reviewed retrospectively NIV use in the early postoperative period of 54 lung transplant patients for three consecutive years. Postextubation NIV was indicated in case of high levels of pCO2 during a T-piece trial
or after extubation, ventilatory mechanisms alterations, or moderate respiratory
acidosis. A major indication for LT was COPD (48 %), and the other indications
were interstitial lung disease (ILD) (26 %), pulmonary arterial hypertension
(11 %), CF (7 %), and others (6 %). Three patients had chronic domiciliary NIV as
a bridge to LT (two had COPD, the other one had ILD). Fourteen patients (26 %)
constituted a NIV group having five endotracheal reintubations (three of them
ended in tracheostomy), whereas in the non-NIV group there were three endotracheal reintubations (all of them ended in tracheostomy). There were no complications observed in the NIV group related to NIV, as well as fewer hours of
endotracheal intubation (ETI) and shorter length of stay in the ICU compared with
non-NIV group (Table 27.1).
In our study, NIV was a useful tool in the LT early postoperative period, and it
was associated with absence of airway complications, less ETI time, and shorter
length of stay on the ICU.
Another circumstance that frequently motivates a prolonged time spent on invasive mechanical ventilation and prolonged ICU length of stay is postsurgical phrenic
paralysis. In these cases, NIV use can reduce time spent on invasive mechanical
ventilation and, hence, length of stay on the ICU.


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Table 27.1 Variables analyzed in the early postoperative period in lung transplant patients.
Hospital Universitario 12 de Octubre
Variable
Arterial blood gases (early postoperative period)

[pH/PCO2 (mean)]
Time spent in endotracheal intubation (mean)
Length of stay (mean)

Non-NIV group
(N = 39)
7.36/45.9

NIV group
(N = 14)
7.33/49.5

53.52 h
10.53 days

43.68 h
7.10 days

NIV noninvasive mechanical ventilation, ICU intensive care unit, PCO2 carbon dioxide partial
pressure in blood

27.2.2.2 NIV as Prevention of Post-extubation Ventilatory Failure
Reintubation due to ventilatory failure is associated with high mortality, mainly
because of its association with infectious events, which increases prophylactic use
of NIV in patients at risk of reintubation. We do not provide concrete evidence in
LT, but there are several studies on intubated patients at risk of post-extubation ventilatory failure in comparable circumstances to lung transplant patients’ conditions
that have shown a decrease in post-extubation ventilatory failure rate in patients
using NIV after extubation, trying to maintain NIV as long as possible in the first
24 h, compared with patients who received standard treatment [7].
Along with this, early use of NIV could be considered in lung transplant patients

who do not pass a T-piece trial or have hypercapnia during this trial, looking for a
protective effect on further development of ventilatory failure.

27.2.2.3 NIV as a Treatment of Ventilatory Failure
In post-extubation ventilatory failure, the use of NIV seems attractive as a way to
avoid the need for reintubation. However, in this case, there are dissenting opinions
about its safety and usefulness. Once ventilatory failure is established, NIV may not
be as useful as we think; it can even have a deleterious effect on survival because it
may delay a needed intubation, increasing the overall mortality. However, in some
studies performed in ventilatory failure in the postoperative period in thoracic surgery, NIV allowed a reduction in the rate of respiratory complications and its associated mortality in a relevant way.

27.2.3 NIV in LT Complications That Present Ventilatory Failure
A major cause of readmission to the ICU in the late postoperative period of LT is
respiratory failure. This might be due to many circumstances, most commonly
infection, cardiogenic acute pulmonary edema, drug side effects, and acute rejection. These situations with higher ventilatory requirements are often worsened by
different circumstances related to LT: myopathy due to steroid use and ventilatory
mechanics alterations due to surgery. Thus, it is known that lung transplant patients
who require invasive mechanical ventilation have a worse prognosis than patients
admitted to the ICU due to diseases not derived from surgery [8].


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Moreover, NIV has demonstrated its usefulness in treating patients with hypoxemic respiratory failure of different etiologies, reducing the need for ETI and
thereby decreasing infectious complications from it (nosocomial pneumonia and
septic shock) and decreasing global mortality [9].

Along with the evidence that NIV is safe and may be beneficial in hypoxemic
failure, this technique also has utility in ventilatory failure management in immunosuppressed patients. In these patients, when ventilatory failure requires ETI, mortality increases significantly, but NIV use enables to reduce reintubation rate and
mortality, compared with reintubated patients. Particularly in lung transplant
patients it has demonstrated an improvement in physiological parameters (arterial
blood gases analysis, breathing rate, etc.) after introducing NIV as acute respiratory
failure treatment. However, these results derive from a descriptive study without a
control group, so we can only conclude that the NIV option is safe and may be beneficial to these patients [10].

27.2.4 NIV in Diagnostic and Therapeutic Techniques in Lung
Transplant Patients
Frequently, lung transplant patients require performance of diagnostic or therapeutic techniques in the airway, particularly bronchoscopy. Bronchoscopy can reduce
tracheal lumen in 10–15 % of patients and increases work of breathing, generating
a relevant hypoxemia. Procedures like bronchoalveolar lavage can cause a greater
decline of oxygenation, and aspiration of bronchial secretions during bronchoscopy performance may produce a pressure drop at the end of expiration that facilitates alveolar collapse. Frequently, these techniques should be performed in
patients with severe hypoxemia, making it necessary to assure adequate oxygenation. NIV use can allow the performance of these procedures, avoiding the need
for intubation and invasive ventilation. Bronchoscopy performance has been
described under continuous positive airway pressure (CPAP), a particularly useful
nonmechanical CPAP system designed by Boussignac, or the “helmet,” but there
are no randomized studies that compare bronchoscopy performance under NIV
versus ETI. In general, it is described that NIV can significantly improve oxygenation during bronchoscopy performance in patients with refractory hypoxemia
compared with conventional oxygen therapy. Nevertheless, it may present some
disadvantages, particularly in hemodynamically unstable patients, severely acidotic patients (pH < 7.20), or patients with no possibility of airway isolation with
bronchoaspiration or gastric distension as associated complications.

Conclusion

NIV is a useful tool in lung transplant patients, where avoiding intubation is crucial. It can also improve work of breathing, gas exchange, oxygenation, and exercise tolerance. Its applications include all the range of complications that may be
present in the pretransplant and post-transplant period (early and late ones).

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In addition, NIV presents obvious advantages over invasive mechanical ventilation, especially related to the lack of infectious complications associated with
the latter. It also allows patient feeding, talking, and expectorating, can be used
intermittently, and its withdrawal or its restart is easy. However, its use is not free
of risk, as with the delay of a necessary intubation, and may have implications in
prognosis, which is why it is recommended that it be used under close surveillance and with skilled staff trained in its application.

Key Major Recommendations

• NIV use in diseases that may require LT is clear. Numerous candidates for
LT have an indication of chronic domiciliary NIV as part of the underlying
disease treatment. There is evidence of NIV’s benefit as a transition aid to
LT in two obstructive pathologies: COPD and CF.
• NIV use in the early postoperative period after LT has three major objectives: to facilitate early extubation, to prevent reintubation due to postsurgery ventilatory failure, and to treat ventilatory failure once it is
established. In our experience, NIV can decrease the number of reintubations and length of stay in the ICU compared with patients in whom NIV
has not been used during their stay on the ICU.
• NIV is safe and may be beneficial in hypoxemic failure. It is very useful in
ventilatory failure management of immunosuppressed patients. Particularly
in lung transplant patients, an improvement of physiological parameters
(arterial blood gases, breathing rate, etc.) has been observed after introduction of NIV as acute respiratory failure treatment in the late postoperative
period.
• NIV can significantly improve oxygenation during diagnostic and therapeutic procedures in lung transplant patients, including bronchoscopy performance in patients with refractory hypoxemia to isolated oxygen
therapy.

References
1. Rabe KF, et al. Global strategy for the diagnosis, management, and prevention of chronic
obstructive pulmonary disease: GOLD executive summary. Am J Respir Crit Care Med.

2007;176(6):532–55.
2. Wiebel M, et al. Noninvasive self-ventilation–successful transition aid in the waiting period
before lung transplantation? Med Klin (Munich). 1995;90(1 Suppl 1):32–4.
3. Fauroux B, et al. Long-term noninvasive ventilation in patients with cystic fibrosis. Respiration.
2008;76(2):168–74.
4. Serra A, et al. Non-invasive proportional assist and pressure support ventilation in patients
with cystic fibrosis and chronic respiratory failure. Thorax. 2002;57(1):50–4.
5. Feltracco P, et al. Noninvasive ventilation in postoperative care of lung transplant recipients.
Transplant Proc. 2009;41(4):1339–44.


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6. Rocca GD, et al. Is very early extubation after lung transplantation feasible? J Cardiothorac
Vasc Anesth. 2003;17(1):29–35.
7. Ferrer M, et al. Noninvasive ventilation during persistent weaning failure: a randomized controlled trial. Am J Respir Crit Care Med. 2003;168(1):70–6.
8. Hadjiliadis D, et al. Outcome of lung transplant patients admitted to the medical ICU. Chest.
2004;125(3):1040–5.
9. Ferrer M, et al. Noninvasive ventilation in severe hypoxemic respiratory failure: a randomized
clinical trial. Am J Respir Crit Care Med. 2003;168(12):1438–44.
10. Rocco M, et al. Non-invasive pressure support ventilation in patients with acute respiratory
failure after bilateral lung transplantation. Intensive Care Med. 2001;27(10):1622–6.


Noninvasive Mechanical Ventilation
in Postoperative Spinal Surgery

28

Eren Fatma Akcil, Ozlem Korkmaz Dilmen,
and Yusuf Tunali

28.1

Introduction

Noninvasive mechanical ventilation (NIMV) is widely used in the treatment of acute
respiratory failure (ARF), and it is particularly effective in the treatment of acute exacerbation of chronic obstructive pulmonary disease (COPD) and cardiogenic pulmonary edema [1]. Acute postoperative respiratory failure is another of the application
areas of NIMV [2]. Postoperative pulmonary complications (PPCs) are critical in the
postoperative period because they increase hospital length of stay (LOS), morbidity,
and mortality [2, 3]. Atelectasis, pneumonia, bronchospasm, pleural effusion, pulmonary edema, pulmonary embolism, and pneumothorax are the clinical forms of PPC
that occur most often. Many cases of postoperative ARF are short and can be treated
successfully with supplemental oxygen, reversal of neuromuscular blocking agents,
bronchodilators, deep-breathing exercises, and chest physiotherapy if no intubation or
mechanical ventilation is required. Postoperative reintubation and invasive mechanical ventilation themselves are also suggested as relating to PPCs. Therefore, because
it is a noninvasive method, NIMV can be properly used in postoperative ARF [4].

28.2

Discussion

The efficacy of NIMV has been demonstrated in postoperative ARF, including cardiac, thoracic, thoracoabdominal, and abdominal surgery [1–5]. Various complications may develop following spinal surgery; the most common are cardiac

E.F. Akcil, MD (*) • O.K. Dilmen, MD • Y. Tunali, MD
Department of Anaesthesiology and Intensive Care Medicine, Istanbul University Cerrahpasa
School of Medicine, Istanbul, Turkey

e-mail: ; ;
© Springer International Publishing Switzerland 2016
A.M. Esquinas (ed.), Noninvasive Mechanical Ventilation and Difficult Weaning
in Critical Care: Key Topics and Practical Approaches,
DOI 10.1007/978-3-319-04259-6_28

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complications (3 %), pulmonary complications (1.2 %), and pneumonia (1.2 %).
Postoperative complications were reported to increase mortality; advanced age (>65),
comorbidities, and complexity of surgical interventions are contributing factors [6, 7].
It is obvious that scoliosis, trauma, and oncological spinal surgical interventions are
more invasive interventions than degenerative disc disease surgery, with higher perioperative morbidity and mortality rates. Moreover, in posterior lumbar fusion operations, mortality is lower than with anterior and thoracic approaches [6]. It has been
demonstrated that diabetes mellitus (particularly insulin-dependent), obesity, COPD,
and steroid use increase complications in lumbar stenosis surgery [7]. Thoracic disk
surgery is particularly associated with pulmonary complications (6.9 %) [8]. In those
undergoing anterior/anterolateral decompression and fusion, all complications and
pulmonary complications were reported to be greater than in those undergoing posterior/posterolateral decompression and only disc decompression with fusion.
Although we report high mortality and morbidity rates in scoliosis surgery, surgical interventions are needed to improve the quality of life of these patients and for
the correction of the vital functions. Irreversibly affected respiratory and cardiac
functions may complicate both anesthesia and surgery. Spinal deformity progression may cause deteriorated respiratory functions. Secondary scoliosis may develop
in children with muscular dystrophies and myopathies, and, hence, spinal fusion
surgery is required. There is alveolar hypoventilation and hypercapnia susceptibility
due to respiratory muscle weakness, and inability to cough in scoliosis accompanied by neuromuscular diseases.
Postoperative pulmonary function is seen to deteriorate further than preoperative

function. In a case series including eight patients, early pre- and postoperative
NIMV applications are effective in protecting the respiratory functions in these children with restrictive respiratory failure [9]. Pre- and postoperative biphasic positive
airway pressure was performed in children with forced vital capacity (FVC) ≤ 1 L,
those undergoing scoliosis surgery, and in a case of desaturation due to hypoventilation during the night, and no difference between preoperative and postoperative
respiratory functions was observed [9]. When NIMV is used in chronic respiratory
failure due to scoliosis, it may improve arterial oxygenation, increase the quality of
life, and reduce the hospital LOS. Following scoliosis surgery, acute respiratory
failure may develop, particularly in patients with poor respiratory functions in the
preoperative period. Atelectasis, depressant effects of opioids, and pain are the contributing factors to the risk of postoperative respiratory failure in these patients [10].
It is established that the application of mechanically assisted cough and nasal intermittent positive pressure ventilation before and after surgery ensures that extubation
will performed successfully and invasive mechanical ventilation will not be required
in patients undergoing scoliosis surgery with FVC values of < 40 % before the surgery [11]. In a study of 73 patients undergoing scoliosis surgery, NIMV was applied
in 28 patients in the perioperative period, and PPC developed less often in this group
than in those who did not undergo NIMV [12].
In the pulmonary function tests of the children with muscular dystrophy, assuming that the vital capacity decreases by 3–10 % per year and surgery is contraindicated without opening tracheostomy in cases with FVC values of below 40 %,
perioperative NIMV application and early surgery seem to be advantageous [13].


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Respiratory function tests guide us in determining the need of ventilator postoperatively and PPC progression in these patients. The use of short-acting anesthetic
drugs, methods reducing blood loss, and effective pain control may reduce postoperative ventilator requirements [14].
Conclusion

Spinal surgery particularly surgery for scoliosis could be complicated by respiratory
failure in the perioperative period, and NIMV is essential for its management.

Key Recommendations

• Respiratory function tests should be evaluated in the preoperative period of
thoracic spinal and scoliosis surgery.
• Short-acting anesthetic drugs should be preferred.
• Postoperative pain management is essential for recovery.

References
1. Garcia-Delgado M, Navarrete I, Garcia-Palma MJ, et al. Postoperative respiratory failure after
cardiac surgery: use of noninvasive ventilation. J Cardiothorac Vasc Anesth. 2012;26:443–7.
2. Pelosi P, Jaber S. Noninvasive respiratory support in the perioperative period. Curr Opin
Anaesthesiol. 2010;23:233–8.
3. Chiumello D, Chevallard G, Gregoretti C. Non-invasive ventilation in postoperative patients:
a systematic review. Intensive Care Med. 2011;37:918–29.
4. Jaber S, Chanques G, Jung B. Postoperative noninvasive ventilation. Anesthesiology.
2010;112:453–61.
5. Albala MZ, Ferrignio M. Short term noninvasive ventilation in the postanesthesia care unit: a
case series. J Clin Anesth. 2005;17:636–9.
6. Pumberger M, Chiu YL, Ma Y, et al. Perioperative mortality after lumbar spinal fusion surgery: an analysis of epidemiology and risk factors. Eur Spine J. 2012;21:1633–9.
7. Deyo RA, Hickam D, Duckard JP, et al. Complications after surgery for lumbar stenosis in a
veteran population. Spine. 2013;38:1695–702.
8. Jain A, Menga EN, Hassanzadeh H, et al. Thoracic disc disorders with myelopathy. Spine.
2014;39:1233–8.
9. Gill I, Eagle M, Mehta JS, et al. Correction of neuromuscular scoliosis in patients with preexisting respiratory failure. Spine. 2006;31:2478–83.
10. Doherty MJ, Millner PA, Latham M, et al. Non-invasive ventilation in the treatment of ventilatory failure following corrective spinal surgery. Anaesthesia. 2001;56:235–47.
11. Bach JR, Sabharwal S. High pulmonary risk scoliosis surgery: role of noninvasive ventilation
and related techniques. J Spinal Disord Tech. 2005;18:527–30.
12. Chong HS, Padua MRA, Kim JS, et al. Usefulness of noninvasive positive-pressure ventilation
during surgery of flaccid neuromuscular scoliosis. J Spinal Disord Tech. 2015. doi:10.1097

BSD.0000000000000234.
13. Mills B, Bach JR, Zhao C, et al. Posterior spinal fusion in children with flaccid neuromuscular
scoliosis: the role of noninvasive positive pressure ventilatory support. J Pediatr Orthop.
2013;33:488–93.
14. Almenrader N, Patel D. Spinal fusion surgery in children with non-idiopathic scoliosis: is there
a need for routine postoperative ventilation? Br J Anaesth. 2006;97(6):851–7.


Noninvasive Ventilation Following
Abdominal Surgery

29

Alastair J. Morgan and Alastair J. Glossop

Abbreviations
CPAP
GI
ICU
MV
NIV
NPPV
PF
PPC
PRF
RCT

Continuous positive airway pressure
Gastrointestinal
Intensive care unit

Mechanical ventilation
Noninvasive ventilation
Noninvasive positive-pressure ventilation
PaO2/FiO2 ratio
Postoperative pulmonary complications
Postoperative respiratory failure
Randomized controlled trial

29.1

Introduction

Patients undergoing abdominal surgery are at risk of developing postoperative
respiratory failure (PRF) and postoperative pulmonary complications (PPCs),
including hypoxemia, atelectasis, bronchospasm, pleural effusions, aspiration

Authors’ Disclosures Alastair Glossop has previously received a scholarship awarded by the
National Institute for Health and Clinical Excellence (NICE) but received no financial incentive.
A.J. Morgan, BSc, MRCP(Ed), FRCA, FFICM • A.J. Glossop, MRCP, FRCA, DICM,
FFICM (*)
Department of Critical Care, Sheffield Teaching Hospitals NHS Foundation Trust,
Herries Road, Sheffield S5 7AU, UK
e-mail:
© Springer International Publishing Switzerland 2016
A.M. Esquinas (ed.), Noninvasive Mechanical Ventilation and Difficult Weaning
in Critical Care: Key Topics and Practical Approaches,
DOI 10.1007/978-3-319-04259-6_29

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pneumonitis, sputum plugging, lobar collapse, pneumonia, and the requirement for
mechanical ventilation (MV). The incidences of PRF and PPCs are 0.2–3.4 and
7.2–40 %, respectively, following elective abdominal surgery, with even higher
rates following emergency surgery and in patients older than 80 years [1]. Depending
on patient characteristics and demographics, associated mortality can exceed 25 %,
with substantial associated increases in health-care costs [1–3].
Endotracheal reintubation is required in 8–10 % of patients secondary to PRF
following major abdominal surgery. Although often a necessary supportive intervention, endotracheal intubation is an independent predictor of hospital mortality,
prolonged intensive care, and hospital stay [1–5]. Noninvasive ventilation (NIV)
has been used as both a prophylactic and therapeutic treatment option in patients
with PRF after major abdominal surgery and may potentially reduce the significant
morbidity and mortality associated with reintubation. Early studies examining the
use of NIV in this patient group were inconclusive or produced conflicting results
[6, 7], but there is now growing evidence and enthusiasm for using NIV postoperatively to reduce the risk of complications following major surgery. This chapter
reviews the evidence for the use of NIV in open abdominal visceral surgery, thoracoabdominal surgery, vascular surgery, and transplant surgery.

29.2

Etiology of Respiratory Complications
following Abdominal Surgery

Pulmonary function deteriorates in all patients following major abdominal surgery,
with a reduction in lung volumes and the development of alveolar collapse and atelectasis in 80–90 % of patients. Atelectasis leads to hypoxemia via ventilation perfusion mismatching. Its development significantly increases the risk of PRF and PPCs
and may trigger an inflammatory reaction promoting bacterial growth in the lungs
and bacterial translocation into the bloodstream. The main disruptions to normal

respiratory function are maximal in the first hours following surgery and generally
regress after 1–2 weeks.

29.3

NIV Following Abdominal Surgery

The use of NIV following major surgery is well established as both a prophylactic
and therapeutic treatment modality. Although oxygen therapy may be effective in
attenuating postoperative hypoxemia, it is only a symptomatic approach that does
not reverse the underlying pathophysiological process. There is evidence to suggest that lung expansion therapy using incentive spirometry and deep-breathing
exercises reduces PPCs after abdominal surgery [8]. Compared with standard positive pressure respiratory therapy, the application of continuous NIV is associated
with an increase in functional residual capacity and reduced atelectasis and left
ventricular afterload, with a subsequent increase in cardiac output and arterial
oxygenation.


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Studies comparing NIV with standard therapy have generally provided positive
results supporting the use of NIV postoperatively, but they are limited by small
sample sizes, with a large variation in the modality of NIV, technical implementation, and timing of application seen between studies. The small sample sizes in
these studies has meant that atelectasis and PaO2/FiO2 (PF) ratio are commonly
assessed, which may not translate into clinically relevant end points such as reintubation and mortality rates. Although reductions in rates of PPCs and reintubation
have been demonstrated in the literature, there is currently limited evidence regarding the impact of NIV on mortality.
A landmark multicenter, prospective, randomized control trial (RCT) of 209

patients published in 2005 by Squadrone et al. [9] demonstrated a significant reduction in reintubation, pneumonia, and sepsis rates following early hood continuous
positive airway pressure (CPAP) in hypoxemic patients after elective major abdominal surgery. ICU length of stay was lower in the CPAP group, but there was no difference in hospital length of stay or in-hospital mortality between groups. In a
prospective observational study involving 72 patients with severe PRF after abdominal surgery, reintubation was avoided in 67 % of patients treated with NIV [10].
A large meta-analysis of 654 patients pooled from nine studies of NIV use
following abdominal surgery demonstrated that NIV use was associated with a
significantly lower rate of PPCs, including atelectasis, when compared with standard medical therapy [11]. The pooled estimate of two studies using intubation as
an endpoint showed a beneficial effect of CPAP (risk reduction 0.85; 95 % confidence interval (CI) 0.34–0.97). Two of the studies included in the analysis assessed
the effect of postoperative CPAP on mortality following abdominal surgery; however, the number of deaths was too small to allow meaningful analysis. The studies included in this meta-analysis displayed marked heterogeneity, differing in
both application and duration of CPAP use, and only included preoperatively
healthy patients in five studies and may therefore underestimate the beneficial
effects of NIV.
CPAP may be of particular benefit for patients who cannot participate with
incentive spirometry or deep-breathing exercises. In patients with obstructive airways disease, CPAP decreases work of breathing by counterbalancing the inspiratory threshold load imposed by intrinsic positive-end expiratory pressure (PEEP).
Noninvasive positive pressure ventilation (NPPV) may be considered in patients in
whom hypercarbia coexists with hypoxemia, when there is a history of chronic
obstructive pulmonary disease, or in patients who are experiencing an increased
respiratory workload.
The optimum amount of PEEP and duration of NIV, particularly as a prophylactic treatment, remains controversial, with a lack of supporting evidence and trials in
which a benefit for NIV has not been evident [7, 12]. Some authors have suggested
that immediate application of NIV post extubation may be more beneficial in
recruiting alveoli than delayed or intermittent NIV, although current practice varies
widely and is often dictated by local preferences and protocols or the need to balance
continued alveolar recruitment with patient comfort, nursing availability, and
workload.


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Upper gastrointestinal (GI) surgery in which a surgical anastomosis has been
formed has historically been considered a contraindication to NIV because of the
theoretical risk of NIV causing increased gastric luminal pressures and subsequent
disruption of the surgical anastomosis. In a prospective cohort study, 1,067 patients
undergoing a gastrojejunostomy as part of a gastric bypass procedure were assessed
[13], and no correlation was found between anastomotic leaks and use of CPAP. In
a retrospective review involving 91 patients receiving CPAP after laparoscopic
Roux-en-Y gastric bypass surgery, the incidence of anastomotic leakage was zero
[14]. Additionally, transmural gastric pressures have not been demonstrated to
increase following the application of CPAP after laparoscopic Roux-en-Y gastric
bypass [15]. Despite the lack of RCT data in this area, it would appear that NIV
usage is not associated with an increased risk of anastomotic failure and is safe to
use following upper GI surgery, although caution should be exercised to avoid high
airway pressures (>25 cmH2O). It would also seem prudent in NPPV use to limit the
maximum Pressure support ventilation (PSV) level to 8 cmH2O to prevent generation of excessively high pressures during inspiration.

29.4

NIV Following Thoracoabdominal Surgery

Esophageal surgery results in diaphragmatic disruption and a restrictive syndrome resulting in atelectasis, hypoxemia, and a high incidence of PPCs, and the
presence of a transposed gastric conduit may further compromise respiratory
function postoperatively. Maintenance of adequate postoperative oxygenation is
of importance in preventing impaired oxygen delivery and subsequent ischemia
of the gastric conduit, which are the main risk factors predisposing to anastomotic leakage.
Michelet et al. [16] compared the efficacy of NIV with conventional treatment in
72 patients who developed post-esophagectomy respiratory failure. This casecontrolled study, in which 36 patients were matched to 36 historical controls, demonstrated a reduction in reintubation, frequency of acute respiratory distress
syndrome, anastomotic leakage, and intensive care unit (ICU) length of stay in
patients treated with NIV compared with controls. No reduction in either hospital
mortality or length of stay was seen. In an RCT including 70 patients undergoing

thoracoabdominal gastroesophageal resection, Fagevik Olsén et al. [4] compared
standard therapy with prophylactic CPAP in the immediate postoperative period.
Significantly fewer patients in the CPAP group required reintubation and prolonged
MV. Clinical outcomes of ICU and hospital length of stay and 30-day mortality
were similar between groups.
In this group of patients with a propensity for developing PRF, who are often of
an increased age with multiple comorbidities, NIV support presents an attractive
option in the postoperative period to maintain adequate oxygenation and reduce the
complications associated with MV. The use of NIV does not appear to be associated
with anastomotic failure and NIV may be safely used following esophageal
surgery.


29

Noninvasive Ventilation Following Abdominal Surgery

29.5

229

NIV Following Vascular Surgery

Repair of a thoracic or abdominal aortic aneurysm is high-risk surgical procedure,
with the risk of developing PRF as high as 60 % in some patient groups and MV
being required in about 8 % of these patients [17, 18]. Mortality rates increase fourfold if a patient requires reintubation following the development of PRF. Therefore,
prevention of respiratory complications in this group of high-risk patients may have
a significant impact on patient morbidity and mortality.
Several studies have examined the use of NIV following abdominal surgery and
included vascular patients, but only two examined NIV use following vascular surgery alone. Böhner et al. [19] applied continuous nasal CPAP for at least 12 h in 99

patients post extubation following laparotomy for vascular surgery. Supplemental
oxygen to maintain arterial oxygen saturations greater than 95 % was used in the
control group of 105 patients. Severe hypoxemia occurred significantly less frequently in the NIV group (5 % vs 16 %; p = 0.01), and nonstatistically significant
trends toward reductions in the incidence of pneumonia and reintubation were also
seen. In a prospective randomized trial of 50 patients, Kindgen-Milles et al. [20]
compared the application of continuous nasal CPAP at 10 cmH2O for a mean of 23 h
with standard therapy following thoracoabdominal aortic aneurysm repair. Nasal
CPAP was associated with significantly fewer pulmonary complications (PF ratio
<100 mmHg, atelectasis, pneumonia, reintubation); a nonsignificant reduction in
mean ICU stay and a significant reduction in mean hospital length of stay (p = 0.048,
8 ± 1 vs 12 ± 2 days) were also seen.
The use of NIV prophylactically following major vascular surgery has thus been
demonstrated in large RCTs to be beneficial in terms of preventing complications
that result in significant morbidity and burden on health-care resources. Although
there is no mortality data to support its use in this patient group, NIV use should be
strongly considered following major vascular surgery.

29.6

NIV Following Solid Organ Transplantation

Postoperative pulmonary complications following solid organ transplantation contribute substantially to morbidity and mortality in this group of patients.
Approximately 5 % of patients undergoing renal, hepatic, cardiac, or pulmonary
transplantation develop postoperative pneumonia. The concurrent use of immunosuppressive therapy to prevent transplant rejection increases the morbidity and mortality associated with pulmonary infection. In patients with PRF, the need to
reintubate is the major factor associated with the development of nosocomial
pneumonia.
Although the use of NIV to prevent intubation and MV is well established in
immunocompromised patients with acute respiratory failure, there is only one randomized trial of postoperative NIV use in patients following intra-abdominal organ
transplantation. Antonelli et al. [21] concluded from an RCT of 40 patients that NIV
compared with supplemental oxygen alone significantly improves PF ratios and

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reduces rates of reintubation, fatal complications, and overall ICU mortality in
organ transplant recipients (lung, liver, and kidney) with hypoxemic PRF. Hospital
mortality rate did not differ between the groups. A subgroup analysis of the patients
undergoing only liver transplantation did not show a significant difference in reintubation and mortality rate, a finding supported by a subgroup analysis of an observational study by Jaber et al. [10].

29.7

Conclusions and Recommendations

Although few studies have examined different techniques to treat or prevent pulmonary complications and large RCTs in this area are lacking, early NIV is an attractive treatment option following major abdominal surgery because it may provide
ongoing respiratory support without the risks of endotracheal intubation and
MV. When NIV is effective in avoiding reintubation, the morbidity and mortality
associated with MV are reduced. NIV may also reduce ICU length of stay, which
has substantial associated cost benefits.
There is good evidence to support the early use of NIV (CPAP) in high-risk
patients with PRF or PPCs following elective major abdominal surgery, and its use
is recommended in this group to reduce reintubation risk. The use of a risk stratification score may assist in identifying the specific patient population for whom NIV
may be of most benefit and directing resources toward patients with the most need
[1]. When used as prophylaxis, based on limited current evidence, NIV should be
applied immediately post extubation and used continuously as tolerated by the
patient. Future research should focus on determining the optimal NIV regimen in
terms of modality, timing, and duration and also address the impact of NIV on mortality in high-risk patients.
The use of NIV after gastrointestinal surgery involving formation of an anastomosis is more controversial, although the available literature suggests that NIV is
safe to use in patients with respiratory failure following esophageal, gastric, and

bariatric surgery as it may reduce reintubation rates without increasing risk of anastomotic dehiscence. Further work is needed in this area to clarify the mode of delivery, timing, and duration of NIV that is most beneficial in this patient group.
The use of NIV as prophylaxis following major vascular surgery has been shown
to reduce the risks of hypoxia, respiratory failure, and need for reintubation, which
are all major causes of postoperative morbidity. Although evidence of mortality
benefit in this patient group is lacking, the use of NIV to prevent such complications
is recommended. There is a paucity of evidence for the use of NIV following transplant surgery, although the available evidence suggests that NIV use may be beneficial in patients who develop respiratory failure postoperatively to prevent the need
for reintubation and the attendant infective risks.
Overall, it is evident that the use of NIV in patients following major abdominal
surgery is beneficial, and although there is little data pertaining to mortality benefit,
there is evidence in all patient groups of reductions in major causes of postoperative
morbidity and complications, which has important implications for patient safety


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231

and use of health-care resources. Debate continues as to whether NIV is best used
as prophylaxis or treatment in postoperative patients and also whether CPAP or
NPPV is the optimal mode of delivery to reduce postoperative complications. Future
research should focus on mortality as an endpoint, given that the morbidity benefits
are already well demonstrated, and also debate the optimum mode, timing, and
delivery of NIV in high-risk surgical patients.

References
1. Canet J, Gallert L, Gomar C, et al. Prediction of postoperative pulmonary complications in a
population-based surgical cohort. Anesthesiology. 2010;113:1338–50.
2. Arozullah AM, Daley J, Henderson WG, et al. Multifactorial risk index for predicting postoperative respiratory failure in men after major non cardiac surgery. The National Veterans

Administration Surgical Quality Improvement Program. Ann Surg. 2000;232:242–53.
3. Johnson RG, Arozullah AM, Neumayer L, et al. Multivariable predictors of postoperative
respiratory failure after general and vascular surgery: results from the patient safety in surgery
study. J Am Coll Surg. 2007;204:1188–98.
4. Fagevik Olsén M, Wennberg E, Johnsson E, et al. Randomized clinical study of the prevention
of pulmonary complications after thoracoabdominal resection by two different breathing techniques. Br J Surg. 2002;89:1228–34.
5. Lawrence VA, Hilsenbeck SG, Mulrow CD, et al. Incidence and hospital stay for cardiac and
pulmonary complications after abdominal surgery. J Gen Intern Med. 1995;10:671–8.
6. Stock M, Downs J, Gauer P, et al. Prevention of postoperative pulmonary complications with
CPAP, incentive spirometry, and conservative therapy. Chest. 1985;87:151–7.
7. Carlsson C, Sonden B, Thylen U. Can postoperative continuous airway pressure (CPAP) prevent pulmonary complications after abdominal surgery? Intensive Care Med. 1981;7:225–9.
8. Lawrence VA, Cornell JE, Smetana GW, et al. Strategies to reduce post-operative pulmonary
complications after non-cardiothoracic surgery: systematic review for the American College of
Physicians. Ann Intern Med. 2006;144:595–608.
9. Squadrone V, Coha M, Cerutti E, et al. Continuous positive airway pressure for treatment of
post-operative hypoxaemia: a randomized controlled trial. JAMA. 2005;293:589–95.
10. Jaber S, Delay J, Sebbane M, et al. Outcomes of patients with acute respiratory failure after abdominal surgery treated with non-invasive positive-pressure ventilation. Chest. 2005;128:2688–95.
11. Ferrerya GP, Baussano I, Squadrone V, et al. Continuous positive airway pressure for treatment
of respiratory complications after abdominal surgery: a systematic review and meta-analysis.
Ann Surg. 2008;247:617–26.
12. Denehy L, Carroll S, Ntoumenopoulos G, et al. A randomized controlled trial comparing periodic mask CPAP with physiotherapy after abdominal surgery. Physiother Res Int. 2001;6:
236–50.
13. Huerta S, DeShields S, Shpiner R, et al. Safety and efficacy of post-operative continuous positive airway pressure to prevent pulmonary complications after Roux-en-Y gastric bypass.
J Gastrointest Surg. 2002;6:354–8.
14. Ramirez A, Labor PF, Szomstein S, et al. Continuous positive airway pressure in immediate
postoperative period after laparoscopic Roux-en-Y gastric bypass: is it safe? Surg Obes Relat
Dis. 2009;5:544–6.
15. Weingarten TN, Kendrick M, Swain JM, et al. Effects of CPAP on gastric pouch pressure after
bariatric surgery. Obes Surg. 2011;21:1900–5.
16. Michelet P, D’Journo XB, Seinaye F, et al. Non-invasive ventilation for treatment of postoperative respiratory failure after oesophagectomy. Br J Surg. 2009;96:54–60.

17. Money SR, Rice K, Crockett D, et al. Risk of respiratory failure after repair of thoracoabdominal aortic aneurysms. Am J Surg. 1994;168:152–5.


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18. Svensson LG, Hess KR, Coselli JS, et al. A prospective study of respiratory failure after highrisk surgery on the thoracoabdominal aorta. J Vasc Surg. 1991;14:271–82.
19. Böhner H, Kindgen-Milles D, Grust A, et al. Prophylactic nasal continuous positive airway
pressure after major vascular surgery: results of prospective randomised trial. Langenbecks
Arch Surg. 2002;387:21–6.
20. Kindgen-Milles D, Muller E, Buhl R, et al. Nasal-continuous positive airway pressure reduces
pulmonary morbidity and length of hospital stay following thoraco-abdominal surgery. Chest.
2005;128:821–8.
21. Antonelli M, Conti G, Bufi M, et al. Noninvasive ventilation for treatment of acute respiratory
failure in patients undergoing solid organ transplantation. A randomized trial. JAMA.
2000;283:235–41.


Noninvasive Mechanical Ventilation
in Postoperative Bariatric Surgery

30

Michele Carron and Anna Toniolo

30.1

Introduction

Obesity has increased worldwide during the past few decades [1, 2]. Anesthesiologists
must provide care for an increasing number of obese patients in their clinical practice.
Anesthesiologists should consider that the specific respiratory problems associated
with obesity may increase the risk of postoperative respiratory complications.
Anesthesia, surgery, and postoperative pain further diminish respiratory function, predisposing the obese patient to hypoxemia and acute respiratory failure (ARF) [1, 2].
Noninvasive ventilation (NIV) may be an important tool for managing obese
patients after surgery. NIV may reduce the risk of ARF, reintubation, duration of
intensive care and hospital stays, morbidity, and mortality in postoperative patients
[3]. Major issues surrounding preoperative and postoperative respiratory changes
and postoperative application of NIV in obese patient are discussed in this
chapter.

30.2

Discussion and Analysis

30.2.1 Definition of Obesity
Obesity is a metabolic disease involving an excessive amount of adipose tissue
[1, 2]. The amount of fat tissue increases proportionally with the total body weight
in obese patients. Body mass index (BMI) is a measure of relative weight based

M. Carron, MD (*) • A. Toniolo, MD
Department of Medicine, Anesthesiology and Intensive Care, University of Padova,
Via C. Battisti, 267, 35121 Padova, Italy
e-mail: ;
© Springer International Publishing Switzerland 2016
A.M. Esquinas (ed.), Noninvasive Mechanical Ventilation and Difficult Weaning
in Critical Care: Key Topics and Practical Approaches,
DOI 10.1007/978-3-319-04259-6_30

233


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M. Carron and A. Toniolo

on the mass and height of an individual. Obesity is defined by a BMI exceeding
30 kg/m2 [1, 2].
However, BMI is not the ideal measurement of obesity because it fails to convey
an accurate account of the distribution of fat [1]. Fat distribution is very important
[1, 2], and can be classified as either android or gynecoid [1]. Although the terms
android and gynecoid refer to the typical male (centripetal) and female (peripheral)
fat distributions, both distributions are observed in both genders [1]. The android
type is of greater pathophysiological significance. Android fat distribution describes
a physique in which weight is carried on the trunk with a high intraperitoneal fat
content. By contrast, gynecoid fat describes a physique in which more weight is
carried on the arms, legs, and buttocks, and abdominal fat is predominantly extraperitoneal. Compared with the gynecoid fat distribution, the android distribution is
more frequently associated with obstructive sleep apnea (OSA) and respiratory
changes [1].

30.2.2 Upper Airway Changes in Obese Patients
Obese patients are predisposed to upper airway obstruction and respiratory failure
[1, 2]. Patency of the upper airway is maintained by the pharyngeal dilator muscles
during inspiration, although lung inflation may also contribute to patency [1, 2].
Postoperative muscle weakness and upper airway or pharyngeal dysfunction following anesthesia may predispose patients to upper airway obstruction, particularly
patients with OSA [1–3]. Fat deposition can promote airway collapse and narrowing of the upper airway. Magnetic resonance imaging studies indicate superficial fat
deposition at the neck and a greater amount of fat deposition in the lateral pharyngeal wall, including pharyngeal structures, such as the tongue, uvula, tonsils, tonsillar pillars, and aryepiglottic folds [1]. These findings are particularly evident in the
android obesity pattern.

30.2.3 Changes in Respiratory Function in Obese Patients
Obesity, particularly severe obesity, affects pulmonary function [1–5]. The accumulation of fat tissue in the chest wall, abdominal cavity, and intrathoracic space
decreases compliance and diminishes lung volume. Cephalic displacement of the
diaphragm increases abdominal content and pulmonary blood volume, further
reducing compliance and lung volume [1–5].
Resting tidal volume normalized to total body weight or lean body weight is
reduced by 50 % or 20 %, respectively, in comparison with that of patients with
normal weights [1, 2]. In addition, the respiratory rate may be 40 % higher in obese
patients than in nonobese subjects [1, 2]. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), functional residual capacity (FRC), expiratory reserve
volume (ERV), total lung capacity (TLC), and maximal voluntary ventilation are
reduced, particularly among morbidly obese patients [2]. Because both FEV1 and


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FVC decrease, the FEV1 to FVC ratio often remains unchanged [1, 2]. TLC, FRC,
and ERV decline exponentially as BMI increases [1, 2]. FRC is usually reduced as
a consequence of reduced ERV, with residual volume remaining within normal limit
[1]. FVC is reduced by 10–15 % in some obese patients and by 25–50 % in morbidly obese patients [2].
Mechanical pulmonary function is further altered by physiological changes that
are present in the obese state [1, 2]. Increased lean body weight and fat tissue
increases oxygen consumption and carbon dioxide production to satisfy metabolic
requirements. These changes increase minute ventilation [1, 2]. Oxygen consumption is increased at rest by approximately 25 % in obese subjects [1, 2]. Despite
increased production of carbon dioxide, normocapnia is usually maintained by the
increased minute ventilation [1, 2]. Patients with chronic obstructive pulmonary
disease (COPD) or obesity hypoventilation syndrome are generally hypercapnic [1,

2]. Increased upper airway resistance, restrictive pulmonary pathophysiology,
increased minute ventilation, oxygen consumption, carbon dioxide production, and
respiratory muscle dysfunction due to increased cytokine levels and fatty infiltration
significantly increase the effort required to breathe [1, 2]. Normocapnic, morbidly
obese subjects exhibit increased breathing effort at rest by about 30–70 %. In severe
obesity, effort required may increase up to 280 % of normal, leading to a 10-fold
increase in the energy cost of breathing [1, 2].
Altered pulmonary function in obese patients affects pulmonary gas exchange,
especially among those with BMIs that exceed 40 kg/m2 [1, 2]. Morbidly obese
patients may have reduced partial arterial oxygen concentrations (PaO2), increased
partial arterial carbon dioxide concentrations (PaCO2), and increased alveolar-toarterial oxygen partial pressure differences. The increased shunt fraction and the
ventilation-perfusion mismatch result in hypoxemia [1, 2].

30.2.4 Postoperative Changes in Respiratory Function
and Impact on Postoperative Outcome
Anesthesia, surgery, and postoperative pain further reduce respiratory function
[1, 2]. Airway resistance and respiratory system elastance increase up to 60 % and
50 %, respectively, whereas the FRC decreases by about 60 % [4, 5]. Reduced lung
volume, modified breathing patterns, diaphragm dysfunction, and postoperative
pain favor low tidal volume ventilation. These changes collectively promote alveolar hypoventilation, hypoxemia, hypercapnia, and increased atelectasis, which predispose the patient to pneumonia [1–3, 6].
The Nationwide Inpatient Sample database documents 304,515 patients as
receiving bariatric surgery between 2006 and 2008, with an overall ARF rate of
1.35 %. The greatest rate of ARF (4.10 %) was observed after open gastric bypass
surgery. The ARF rate was lower after laparoscopic surgery compared with that
after open surgery (0.94 % vs 3.87 %, p < 0.01) or after nongastric bypass versus
gastric bypass (0.82 % vs 1.54 %, p < 0.01) [7]. Age, BMI, ASA =American Society
of Anesthesiologists physical status, metabolic syndrome, and additional


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M. Carron and A. Toniolo

comorbidities are associated with an increased risk of postoperative respiratory
complications (i.e., pneumonia, atelectasis, respiratory failure, adult respiratory distress syndrome) [1–3]. Despite a relatively low incidence, postoperative ARF may
represent a life-threatening event. A retrospective analysis of a large prospective
database from 1996 to 2006, including 13,871 bariatric surgical procedures, showed
that ARF was the fourth cause of mortality (11.8 %) [8].

30.2.5 Noninvasive Ventilation Techniques and Device
Continuous positive airway pressure (CPAP) and non-invasive positive pressure
ventilation (NPPV) have been proposed for use during the postoperative period in
obese patients [2, 3].
CPAP is a method that delivers constant positive airway pressure noninvasively
during both inspiration and expiration [3]. When CPAP is applied with positive
inspiratory ventilatory support (PSV), it is referred to as positive end-expiratory
pressure (PEEP) [3]. CPAP decreases upper airway obstruction and prevents airway
and alveolar collapse. This action reduces atelectasis and increases FRC by recruiting and stabilizing previously collapsed lung tissue, reducing ventilation/perfusion
mismatch and shunt fraction with improved gas exchange [2, 3]. CPAP counteracts
the effect of increased abdominal pressure on the diaphragm and decreases the work
of breathing, counterbalancing the inspiratory threshold load imposed by intrinsic
PEEP in some patients (i.e., COPD patients) [2, 3]. Furthermore, CPAP reduces left
ventricular afterload and increases cardiac output [2, 3].
NPPV refers to PSV with or without PEEP and BiPAP (bi-level positive airway
pressure) [3]. BiPAP is a technique that delivers two positive airway pressures [3].
In fact, BiPAP includes PSV plus PEEP and CPAP, in which the later delivers only
one positive airway pressure. In comparison to that achieved with CPAP, PSV above
PEEP achieves improved muscle unloading and relief from dyspnea during NIV [3].
PSV plus PEEP increases the alveolar ventilation obtained with CPAP alone [2, 3].
It is difficult to establish a standard recommendation for all obese patients. An

individual titration should be performed to find the best NIV setting to reduce dyspnea, unload respiratory muscles, increase oxygenation, and counteract the effect of
increased abdominal pressure on the diaphragm in obese patients after surgery [2, 3].
Patient selection and monitoring are crucial for reducing NIV failure [6]. NIV should
never be initiated in uncooperative and/or hemodynamically unstable patients [6].
Such patients need prompt tracheal intubation to allow conventional ventilation;
delayed ventilation is associated with increased morbidity and mortality [6].
During NIV, gas is delivered to the airway via an interface (nasal or facial mask or
helmet) [2, 6]. The appropriate selection and adequate management of a device are
crucial for minimizing the risk of complications and failure during NIV [2, 6]. It is
important to choose an interface that fits properly and minimizes air leaks and to allow
the patient to become familiar with the equipment in the first few minutes of NIV [2,
6]. In patients who feel claustrophobic, the use of different sizes or types of masks or
helmets may enhance patient comfort [2, 6]. To date, there is no evidence supporting


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Noninvasive Mechanical Ventilation in Postoperative Bariatric Surgery

237

the use of a specific patient interface device in obese patients [2, 6]. However, the use
of a helmet may improve patient comfort and compliance. Helmets are better tolerated
than masks, resulting in longer use and lower NIV failure rates [6].
Prevention and management of gastric insufflation may be achieved by placing a
nasogastric tube for intermittent air and fluid aspiration prior to NIV [2, 6]. Antacid
prophylaxis should be considered for reducing gastric content and vomiting after
gastric insufflation to avoid serious complications (i.e., pulmonary aspiration, pneumonia, and possibly death) [2, 6].

30.2.6 Rationale for Postoperative NIV in Obese Patients

Postoperative NIV can be used in a prophylactic or curative manner during bariatric
surgery. Prophylactic use involves treating postoperative changes in respiratory
function to prevent postoperative ARF. Curative use occurs after ARF develops and
is aimed toward alleviating respiratory failure and avoiding tracheal intubation,
which is associated with increased morbidity and mortality [3].

30.2.6.1 Postoperative Prophylactic Use of NIV in Obese Patients
Gaszynski et al. [9] compared postoperative Boussignac CPAP delivered through a
facial mask with traditional oxygen delivery via nasal catheter in 19 morbidly obese
patients after open Roux-en-Y gastric bypass [9]. CPAP improved blood oxygenation compared with that achieved with standard treatment (PaO2 81.0 ± 16.0 vs.
65.9 ± 4.9 mmHg, p < 0.05) without influencing carbon dioxide clearance [9].
Neligan et al. [10] compared the effect of Boussignac CPAP (CPAP System;
Vitaid; Toronto, CA) on lung function to that of supplemental oxygen alone after
extubation of 40 morbidly obese patients with known OSA who received laparoscopic bariatric surgery [10]. FEV1, FVC, and peak expiratory flow were increased
by 35 % after administering CPAP immediately after extubation for the duration of
stay in the PACU (post-anesthesia care unit) and by 22 % after CPAP was applied
for at least 8 h overnight [10].
El-Solh et al. [11] evaluated NIV immediately after extubation of 62 consecutive
severely obese patients. NIV was delivered by the BiPAP mode (BiPAP S/T-D
Ventilatory Support System; Respironics Inc.; Murrysville, PA, USA) through a nasal
mask [11]. Compared with conventional therapy, BiPAP resulted in a 16 % absolute
risk reduction in the rate of respiratory failure [11]. There were significant differences
in the lengths of intensive care unit (ICU) and hospital stays between the two groups
[11]. Subgroup analysis of hypercapnic patients showed a reduced number of hospital
mortalities in the NIV group compared with that of the control group [11].
Joris et al. [12] investigated the effect of BiPAP (BiPAP System; Respironics Inc.;
Murrysville, PA, USA) delivered through a nasal mask on postoperative pulmonary
function in 33 morbidly obese patients after gastroplasty. Patients were assigned to
one of three types of ventilatory support during the first 24 h postoperatively: oxygen
via face mask, BiPAP 8/4, or BiPAP 12/4 [12]. Patients in the two BiPAP groups used

the mask at least 2 h out of every 3 h during the first 24 h postoperatively [12]. The


238

M. Carron and A. Toniolo

use of BiPAP 12/4, but not 8/4, allowed significant reduction in the magnitude of
pulmonary dysfunction after gastroplasty [12]. FVC and FEV1 were more than 50 %
greater in the BiPAP 12/4 group compared with those in the control group during 3
days of follow-up observation [12]. The peak expiratory flow rate was also increased
in the BiPAP 12/4 group (p = 0.10) [12]. Improved pulmonary function was associated with a significant increase in oxygenation in both BiPAP groups [12].
Zoremba et al. [13] prospectively studied 60 obese patients undergoing minor
peripheral surgery. Half were randomly assigned to receive short-term NPPV
(PSV + PEEP; Dräger AG; Lübeck, Germany) through full face masks during their
PACU stays; the others received supplemental oxygen via Venturi masks [13].
Pulmonary function in the NPPV group was significantly better than that in the
control group (p < 0.0001) [13]. Blood gas levels and the alveolar to arterial oxygen
partial pressure difference were also improved (p < 0.03) [13]. These effects persisted for at least 24 h after surgery (p < 0.05) [13] (Fig. 30.1).

30.2.6.2 Postoperative Curative Use of NIV in Obese Patients
No data are available in the literature regarding the role of NIV for postoperative
treatment of ARF in obese patients.
In a study of 72 nonobese patients with ARF after abdominal surgery who
were treated with NPPV (PSV + PEEP; Servo-Ventilator 300; Siemens; Elema,
Sweden; or Evita 4; Dräger Medical; Lübeck, Germany) via face mask, Jaber
et al. [14] found that 67 % of patients avoided intubation [14]. Within the first
NPPV observation period, a significant benefit was observed only in the NPPV
group, with increased PaO2/FiO2 (+36 ± 29), decreased respiratory rate (from
28.2 ± 3.4 to 23.1 ± 3.8 breaths/min), reduced length of ICU stay, and reduced

mortality rate [14].

a

b

Fig. 30.1 Postoperative use of NIV in obese patients. (a) Prophylactic use of CPAP in an obese
patient after laparoscopic sleeve gastrectomy through a CPAP mask with integral Venturi flow
driver and adjustable PEEP valve (Ventumask; StarMed; Mirandola, Italy). (b) Therapeutic use of
NPPV (PSV + PEEP) in an obese patient with respiratory failure after gastric bypass surgery delivered by a helmet for NIV (CaStar R; StarMed; Mirandola, Italy). Written informed consent was
obtained from patients


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Noninvasive Mechanical Ventilation in Postoperative Bariatric Surgery

239

One meta-analysis showed that NIV reduced reintubation rates (odds ratio (OR)
0.24), incidence of pneumonia (OR 0.27), and ICU length of stay (0.44 days) when
applied after major surgery [15]. There was insufficient evidence to suggest that
NIV improves ICU survival, but an increased hospital survival was observed when
NIV was used after surgery (OR 4.54) [15].
Conclusion

Obese patients present preoperative changes in respiratory function. Anesthesia
and surgery can profoundly impair respiratory function, increasing the risk of
postoperative respiratory complications and ARF. Evidence supports early
administration of NIV as a prophylactic and as a therapeutic tool after surgery in

obese patients for improving respiratory function and gas exchange. Selection of
the correct interface (face or nasal mask vs helmet) and the type of NIV (CPAP
vs NPPV) together with proper monitoring of the patient during NIV is fundamental for increasing the likelihood of success of NIV.

Key Major Recommendations

• Obese patients have a restrictive pattern, which includes reduced lung volume and compromised respiratory system compliance. Obese patients may
be hypoxemic with increased at-rest consumption of oxygen. Carbon dioxide is usually close to normal.
• Anesthesia, surgery, and postoperative pain further reduce lung volumes,
altering respiratory mechanics and gas exchange.
• Early administration of NIV should be considered as a prophylactic and
therapeutic tool in obese patients after surgery to improve respiratory function and gas exchange and to avoid respiratory failure.
• CPAP essentially decreases upper airway obstruction and increases oxygenation by recruiting and stabilizing previously collapsed lung tissue,
increasing lung volumes. NPPV unloads respiratory muscles, relieves dyspnea, and reduces the work required for breathing.

Conflict of Interest Disclosure The authors have no interests to disclose.

References
1. Adams JP, Murphy PG. Obesity in anaesthesia and intensive care. Br J Anaesth.
2000;85:91–108.
2. Pelosi P, Gregoretti C. Perioperative management of obese patients. Best Pract Res Clin
Anaesthesiol. 2010;24:211–25.
3. Jaber S, Chanques G, Jung B. Postoperative noninvasive ventilation. Anesthesiology.
2010;112:453–61.