Weaning patients with obesity from ventilatory support

Abstract

Purpose of reviewObesity prevalence is increasing in most countries in the world. In the United States, 42% of the population is obese (body mass index (BMI) > 30) and 9.2% is obese class III (BMI > 40). One of the greatest challenges in critically ill patients with obesity is the optimization of mechanical ventilation. The goal of this review is to describe respiratory physiologic changes in patients with obesity and discuss possible mechanical ventilation strategies to improve respiratory function. Recent findingsIndividualized mechanical ventilation based on respiratory physiology after a decremental positive endexpiratory pressure (PEEP) trial improves oxygenation and respiratory mechanics. In a recent study, mortality of patients with respiratory failure and obesity was reduced by about 50% when mechanical ventilation was associated with the use of esophageal manometry and electrical impedance tomography (EIT). SummaryObesity greatly alters the respiratory system mechanics causing atelectasis and prolonged duration of mechanical ventilation. At present, novel strategies to ventilate patients with obesity based on individual respiratory physiology showed to be superior to those based on standard universal tables of mechanical ventilation. Esophageal manometry and EIT are essential tools to systematically assess respiratory system mechanics, safely adjust relatively high levels of PEEP, and improve chances for successful weaning.

Unsuccessful and Successful Clinical Trials in Acute Respiratory Distress Syndrome: Addressing Physiology-Based Gaps

“…Compliance is a property that describes lung distensibility and is calculated as the change in lung volume divided by the change in pressure. Lung compliance of the respiratory system is calculated as the VT divided by the transpulmonary pressure, the pressure across the lung (or alveolar pressure minus pleural pressure) ( Kacmarek et al, 2021 ). Atelectatic areas of the lungs can be expanded by a brief application of high transpulmonary pressure, followed by a PEEP level that maintains open the new re-aerated region ( Suárez-Sipmann et al, 2007 ).…”

“…Pleural pressure is estimated via esophageal manometry employing the measurement of esophageal pressure at the end of expiration, as a surrogate estimate of pleural pressure. It differs among patients with hypoxemic acute respiratory failure, suggesting that lung and chest wall mechanics contribute to respiratory system mechanics, as measured by the mechanical ventilator ( Kacmarek et al, 2021 ). In general, the transpulmonary end-expiratory pressure is equal to zero: the more negative the transpulmonary pressure, the greater the collapse caused by a reduction in lung compliance.…”

“…The optimal ventilation strategy for ARDS still remains to be refined. For example, the physiological meaning of the end-expiratory transpulmonary pressure could be very useful in managing patients with increased chest wall stiffness or to set optimal PEEP during ventilation and weaning in morbidly obese patients ( Kacmarek et al, 2021 ).…”

Analysis of risk factors of prolonged mechanical ventilation in patients with severe burn injury

“…BMI was not statistically significant in this study. [25][26][27] We believe that patients with severe burns are in a high metabolic state and lose weight significantly quickly, a dynamic process with no reference value.…”

How Medical Conditions Affect the Weaning of Mechanical Ventilation

“…Obese patients, with a body mass index (BMI) > 30, have specific problems during MV. The large weight on the rib cage can cause alveolar collapse in some conditions and gravity can influence pulmonary mechanics [48]. In a study of obese patients with ARF, mortality was reduced by 50% when the choice of PEEP was guided with an esophageal catheter (EsoC) and electrical impedance tomography (EIT) [49].…”