Controversies involving hypercapnic acidosis in acute respiratory distress syndrome.

Acute respiratory distress syndrome is characterized by a diffuse inflammatory reaction of lung parenchyma induced by a direct insult to the alveolar epithelium (pulmonary acute respiratory distress syndrome) or an indirect lesion through the vascular endothelium (extrapulmonary acute respiratory distress syndrome). The main therapeutic strategy for acute respiratory distress syndrome is the ventilatory support. However, mechanical ventilation can worsen lung injury. In this context, a protective ventilatory strategy with low tidal volume has been proposed. The use of low tidal volume reduced the mortality rate of acute respiratory distress syndrome patients, but result in hypercapnic acidosis. The current article presents a review of literature on the effects of permissive hypercapnia in acute respiratory distress syndrome. To that end, we carried out a systematic review of scientific literature based on established criteria for documental analysis including clinical and experimental articles, using as data bases MedLine, LILACS, SciELO, PubMed, Cochrane. Hypercapnic acidosis has been considered by some authors as a modulator of the inflammatory process of acute respiratory distress syndrome. However, clinical and experimental studies on the effects of hypercapnic acidosis have shown controversial results. Therefore it is important to better elucidate the role of hypercapnic acidosis in acute respiratory distress syndrome.