Fig. 1

Concept of postural lung recruitment. Theoretical explanations of the postural recruitment maneuver in an anesthetized child 6 years of age. The maneuver consists of sequential changes in body position from supine to both lateral positions and back to supine again, keeping ventilatory settings constant. The gradient of trans-pulmonary pressures (Ptp) differs between body positions due to the elliptical shape of the chest with the gravity-dependent thoracic dimension being larger in lateral than in the supine position (yellow arrows). Thus, the lower half of the lungs is predisposed to collapse while the upper half is usually aerated and “open” during the entire respiratory cycle (red dotted line). In the left lateral position (LL), the entire right upper lung has the chance to open up at a low plateau pressures even under standard ventilator settings (gray lung). Once open, this right lung can maintain its “open lung” condition when turned to the right lateral positioning (RL) provided sufficient PEEP is applied. Notice the larger vertical distance in the lateral position required a higher PEEP to counteract the potential decrease in Ptp in the dependent lung. Now, the left lung is being recruited as it is placed in the uppermost gravity non-dependent position. At the end of the postural recruitment maneuver both lungs are free from atelectasis although the patient has returned to the baseline supine position