Abstract
Mechanical ventilation is indispensable for the survival of patients with acute lung injury and acute respiratory distress syndrome. However, excessive tidal volumes and inadequate lung recruitment may contribute to mortality by causing ventilator-induced lung injury. This bench-to-bedside review presents the scientific rationale for using adjuncts to mechanical ventilation aimed at optimizing lung recruitment and preventing the deleterious consequences of reduced tidal volume. To enhance CO2 elimination when tidal volume is reduced, the following are possible: first, ventilator respiratory frequency can be increased without necessarily generating intrinsic positive end-expiratory pressure; second, instrumental dead space can be reduced by replacing the heat and moisture exchanger with a conventional humidifier; and third, expiratory washout can be used for replacing the CO2-laden gas present at end expiration in the instrumental dead space by a fresh gas (this method is still experimental). For optimizing lung recruitment and preventing lung derecruitment there are the following possibilities: first, recruitment manoeuvres may be performed in the most hypoxaemic patients before implementing the preset positive end-expiratory pressure or after episodes of accidental lung derecruitment; second, the patient can be turned to the prone position; third, closed-circuit endotracheal suctioning is to be preferred to open endotracheal suctioning.
Highlights
Mechanical ventilation is indispensable for the survival of patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS)
Optimizing lung recruitment with positive end-expiratory pressure (PEEP) may require a recruitment manoeuvre [14] and the prevention of endotracheal suctioning-induced lung derecruitment [15]. This bench-to-bedside review presents the scientific rationale supporting the clinical use of adjuncts to mechanical ventilation aimed at optimizing lung recruitment and preventing the deleterious consequences of reduced tidal volume
Clinical use of adjuncts to mechanical ventilation allows optimization of alveolar recruitment resulting from PEEP and prevention of deleterious consequences of reduced tidal volume
Summary
Mechanical ventilation is indispensable for the survival of patients with acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Prone positioning induces a more uniform distribution of gas and tissue along the sternovertebral and cephalocaudal axis by reducing the gas/tissue ratio of the parasternal and cephalic lung regions [54,55] It reduces regional ventilation-to-perfusion mismatch, prevents the free expansion of anterior parts of the chest wall, promotes PEEPinduced alveolar recruitment [56], facilitates the drainage of bronchial secretions and potentiates the beneficial effect of recruitment manoeuvres [57], all factors that contribute to improving arterial oxygenation in most patients with early acute respiratory failure [55] and may reduce ventilatorinduced lung overinflation.
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