prone positioning - MOA

Q: 42 years old male is admitted to ICU with severe acute pancreatitis and developed severe ARDS. Prone positioning for 18 hours a day was initiated, while transfer to higher level of care can be arranged for the ECMO. 

Prone position ___________  the ventral alveolar overinflation? (select one)

A) decreases

B) increases

Answer: A

Prone positioning improves oxygenation via two mechanisms.

1. As patient lies prone on his chest, it decreases the ventral alveolar overinflation, and simultaneously dorsal alveolar collapse. This leads to the reduction in the difference between the dorsal and ventral transpulmonary pressure (Ptp). This makes ventilation more homogeneous in lung fields. This reduced alveolar distension limits ventilator-associated lung injury from overdistention and cyclic atelectasis.

2. Prone ventilation also opens alveoli that usually collapsed in the supine position. This also improves oxygenation. Fortunately, with the application of positive end expiratory pressure (PEEP), most patients sustain dorsal alveoli open during supine periods of prone positioning.

#ventilators

#pulmonary

References:

1. Douglas WW, Rehder K, Beynen FM, et al. Improved oxygenation in patients with acute respiratory failure: the prone position. Am Rev Respir Dis 1977; 115:559.

2. Lai-Fook SJ, Rodarte JR. Pleural pressure distribution and its relationship to lung volume and interstitial pressure. J Appl Physiol (1985) 1991; 70:967.

3. Cornejo RA, Díaz JC, Tobar EA, et al. Effects of prone positioning on lung protection in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med 2013; 188:440.