Wednesday, February 24, 2016

PEEP in the Morbidly Obese

Resultado de imagen de Pulm CCM
PulmCCM - February 17, 2016 - By Jon-Emile Kenny
A recent study of applied respiratory physiology in the mechanically-ventilated, obese patient was published. The ubiquitous focus on lung protective ventilation with “low” [physiological] lung volumes, and low plateau pressure may leave the obese patient susceptible to untoward respiratory embarrassment. Excess abdominal and chest wall weight affect each of the following: reduction in lung volume, increased expiratory flow limitation, increased gas-trapping andaugmentation of auto-PEEP. Cephalad displacement of the diaphragm from increased intra-abdominal pressure may explain why obese patients have been found to have a negative transpulmonary pressure [Ptp = alveolar pressure minus pleural pressure]. Note that a negative Ptp designates a pleural pressure greater than alveolar pressure which suggests lung volume loss [collapse]. Because the pressure within the alveolus at end-expiration [or inspiration for that matter] reflects the elastance of both the lungs, and chest wall, it is possible that PEEP – in the obese – is ‘under-dosed.’