Paradoxical Positioning: Does “Head Up” Always Improve Mechanics and Lung Protection?* : Critical Care Medicine

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Inclining the head of the bed, a default clinical practice, is a form of chest wall “unloading” that predictably increases PL and lung volumes in all patients. Increased PL in the upright position tends to recruit additional lung units while further distending those that are already open. The net result may either improve or deteriorate lung and system compliances, as well as their associated airway pressures, depending on whether recruitment or overdistension predominates. (View Highlight)

In the advanced stages of ARDS, increased PL associated with upright positioning may fail to recruit additional lung units, resulting instead in end-tidal overdistension of the baby lung and decreased Crs. Loading the chest wall in this scenario, or decreasing bed angulation, could force volume reduction of open lung units, thereby placing them in a more favorable region of their individual pressure-volume curves and leading to paradoxical improvement in compliance of both the lungs and respiratory system (View Highlight)
Whether supine or prone, body inclination should thus be considered a modifiable determinant of PL in this population, similar to Vt and PEEP (View Highlight)
while chest wall loading may be effective for modifying PL even when sustained over hours (e.g., by abdominal binding, weighting, or by pressure-regulated mechanical devices), its effects on the regional distribution of ventilation and pulmonary blood flow, its optimal duration, and its ultimate clinical value or adverse consequences remain largely undefined. (View Highlight)