Characteristics of ventilation in obesity

Abstract

There is an increasing trend in the prevalence of obesity in intensive care units (ICU). Obesity is associated with an increase in abdominal pressure that markedly affects respiratory mechanics and is associated with a reduction in functional residual capacity, the leading cause of atelectasis formation during anesthesia. Obese patients are prone to respiratory complications related to ventilation, especially acute respiratory distress syndrome (ARDS). Ventilation of obese patients in the ICU has to take into account these pathophysiological characteristics. Preoxygenation using pressure support ventilation with a positive end-expiratory pressure (PEEP) between 5 and 10 cmH₂O is recommended, followed by lung protective mechanical ventilation using low tidal volume, calculated on ideal rather than actual body weight (6 ml/kg), and high PEEP (10 cmH₂O), provided the absence of severe hemodynamic alteration. The use of recruitment maneuvers (like applying a pressure of 40 cmH₂O during 40 seconds) should be considered in these patients prone to atelectasis formation. Mechanical ventilation can be performed using either volume-or pressurecontrolled mode, according to the each center specific expertise. Prone position should be considered in obese patients with ARDS, allowing significant improvement in the PaO₂/ FiO₂ ratio. Finally, despite high resource utilization, the prognosis of obese patients receiving mechanical ventilation seems to be similar to that of non-obese patients.