Recruitment maneuvers in acute respiratory distress syndrome

Abstract

The rationale for the use of recruitment maneuvers (RMs) in acute respiratory distress syndrome (ARDS) is to promote alveolar recruitment, leading to an increased end-expiratory lung volume and thus decreased ventilator-induced lung injury (VILI). RMs consists of a transient increase in transpulmonary pressure that can re-open previously collapsed alveoli. RMs represents a physiological response to lung aggression in different conditions by re-opening the collapsed part of the lung and decreasing lung oedema. This process can be accomplished through a variety of methods. The RM that has probably been used most commonly is sustained inflation, but recruitment can be achieved by a prolonged sigh, leading to a lesser increase in transpulmonary pressure for a longer period of time. This extended sigh seems to be more efficient, with less haemodynamic compromise. Knowledge of physiological determinants is crucial to selecting good levels of pressure and time required to perform an efficient and well-tolerated RM. Identifying ARDS patients who may benefit from RMs is a major issue, depending essentially on the amount of recruitable lung involved. In any case, however, RMs should be done at the early phase of ARDS.

Keywords: Recruitment maneuvers (RMs); acute respiratory distress syndrome (ARDS); lung oedema; mechanical ventilation.

Figure 1

CT scan of a characteristic patient. (A) In ZEEP shows an important loss of aeration in the left lung and slight diffuse loss of aeration in the right lung. PaO₂/FiO₂ =171 mmHg; (B) acquired with a positive end expiratory pressure of 11 cmH₂O showing no change in left lung and an increase in lung aeration of the right lung. PaO₂/FiO₂ =171 mmHg; (C) acquired at the end of recruitment maneuver (RM) between 35 and 40s. All the lungs were reopened. PaO₂/FiO₂ =342 mmHg; (D) 10 minutes after RM with the same PEEP of 11 cmH₂O. The effect of RM was maintained. PaO₂/FiO₂ =335 mmHg. The level of PEEP used was unable to open the lung but enough to keep the lung open. ZEEP, zero end expiratory pressure; PEEP, positive end-expiratory pressure.

Figure 2

Schematic representations of three different RMs. In the upper part is represented a SI with a high transpulmonary pressure for a short period of time. In the middle an extended sigh (eSigh) in pressure control mode. A stepwise increased in PEEP with the same driving pressure. These maneuvers have been described for 2 to 4 minutes. In the lower part is represented an eSigh realized in volume control ventilation for 5 to 10 minutes reaching in a high plateau pressure.