Pulmonary and Ventilatory Effects of Bed Verticalization in Patients With Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is defined using the clinical criteria of bilateral pulmonary opacities on a chest radiograph, arterial hypoxemia (partial pressure of arterial oxygen \[PaO2\] to fraction of inspired oxygen \[FiO2\] ratio ≤ 300 mmHg with positive end-expiratory pressure \[PEEP\] ≥ 5 cmH2O) within one week of a clinical insult or new or worsening respiratory symptoms, and the exclusion of cardiac failure as the primary cause. ARDS is a fatal condition for intensive care unit (ICU) patients with a mortality between 30 and 40%, and a frequently under-recognized challenge for clinicians. Patients with severe symptoms may retain sequelae that have recently been reported in the literature. These sequelae may include chronic respiratory failure, disabling neuro-muscular disorders, and post-traumatic stress disorder identical to that observed in soldiers returning from war. The management of a patient with ARDS requires first of all an optimization of oxygenation, which relies primarily on mechanical ventilation, whether invasive or non-invasive (for less severe patients). Since the ARDS network study published in 2000 in the New England Journal of Medicine, it has been internationally accepted that tidal volumes must be reduced in order to limit the risk of alveolar over-distension and ventilator-induced lung injury (VILI). A tidal volume of approximately 6 mL.kg-1 ideal body weight (IBW) should be applied. Routine neuromuscular blockade of the most severe patients (PaO2/FiO2 \< 120 mmHg) is usually the rule, although it is increasingly being questioned. Comprehensive ventilatory management is based on the concepts of baby lung and open lung, introduced respectively by Gattinoni and Lachmann. According to these concepts, it must be considered that the lung volume available for mechanical ventilation is very small compared to the healthy lung for a given patient (baby lung) and that the reduction in tidal volume must be associated with the use of