use higher PEEP for SBT in obese patients

With the high prevalence of obesity, intensivists are increasingly challenged in liberating these patients from mechanical ventilation. The dominant physiologic consequences of obesity on the respiratory system include reduced lung compliance, dependent airway closure, and reduced chest wall (including abdomen) compliance. Of particular importance is dependent airway closure, which increases the work of breathing and worsens gas exchange. Expiratory flow limitation and auto-PEEP are often sufficiently severe to cause failure during SBTs. Raising PEEP levels well above those conventionally used, especially combined with upright posture, reduces work of breathing dramatically. This can convert a failed SBT to a successful one, facilitating extubation (to noninvasive ventilation with expiratory positive airway pressure). The choice of 12 cm H2O is a somewhat arbitrary but reasonable level based on physiologic studies of patients with obesity.

Nothing in this case suggests that nutrition or chest physiotherapy will lead to a successful SBT on subsequent days. In fact, the same physiology of auto-PEEP will continue to plague SBTs conducted at low PEEP in this patient and with time may be compounded by weakness or other complications of bed rest. Tracheostomy is unnecessary at this point in the ICU course and risks procedural complications. Sedatives are generally ineffective in facilitating liberation from mechanical ventilation and in this patient would fail to address the underlying physiologic impediments to successful SBT.1234

Footnotes

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  2. Behazin N, Jones SB, Cohen RI, et al. Respiratory restriction and elevated pleural and esophageal pressures in morbid obesity. J Appl Physiol (1985). 2010;108(1):212-218. PubMed ↩

  3. Lemyze M, Mallat J, Duhamel A, et al. Effects of sitting position and applied positive end-expiratory pressure on respiratory mechanics of critically ill obese patients receiving mechanical ventilation. Crit Care Med. 2013;41(11):2592-2599. PubMed ↩

  4. Teggia Droghi M, De Santis Santiago RR, Pinciroli R, et al. High positive end-expiratory pressure allows extubation of an obese patient. Am J Respir Crit Care Med. 2018;198(4):524-525. PubMed ↩