Changes in the body position of patients receiving mechanical ventilation in intensive care unit are frequent. Contrary to healthy humans, little data has explored the physiological impact of position on respiratory mechanics. The objective of present paper is to review the available data on the effect of changing body position on respiratory mechanics in ICU patients receiving mechanical ventilation. Supine position (lying flat) or lateral position do not seem beneficial for critically ill patients in terms of respiratory mechanics. The sitting position (with thorax angulation >30° from the horizontal plane) is associated with improvement of functional residual capacity (FRC), oxygenation and reduction of work of breathing. There is a critical angle of inclination in the seated position above which the increase in abdominal pressure contributes to increase chest wall elastance and offset the increase in FRC. The impact of prone position on respiratory mechanics is complex, but the increase in chest wall elastance is a central mechanism. To sum up, both sitting and prone positions provides beneficial impact on respiratory mechanics of mechanically ventilated patients as compared to supine position.
Keywords: Body position, respiratory mechanics, mechanical ventilation, lung volume
..."Effects of prone position on lung volumes and respiratory mechanics in ARDS
As
prone position is an intervention that has been shown to improve
survival (1,18) its effect on respiratory mechanics might be implicated
in the patient outcome. We will see that these effects are complex and
it is not so clear we can capture a scenario that would explain the
better survival observed in trials from the change in respiratory
mechanics in prone."
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