Permissive hypercapnia: role in protective lung ventilatory strategies

Purpose of reviewHypercapina is a central component of current proctective ventilatory stratergies. This review aims to present and interpret data from recent clinical and experimental studies relating to hypercapma ond its role is protective ventilatory stratergies.Recent findingsIncreasing clinical evidence supports the use of premissive hypercapina particularly in acute lung injury acute respiratory distress syndrome, status asthmaticus and neonatal respiratory distress syndrome, status asthmaticus and neonatal respratory failure. However there are no clinical data examining the contribution of hypercapina per se to protective ventilatory strategies. Recent experimental studies provide further support for the concept of theraputic hypercapenia whereby deliberately evaluated PaCO2 may attenuates experimentalacute lung injury because of adverse ventilatory stratergies mesentic schemia reperfusion and pulmonary endotoxin instillation. Hypercapnic acidosis attenuates the activation of nuclear factor kappa B, a key regulator of the expression of multiple genes involved in the inflammatory response. The physiologic effects of hypercapnia, both beneficial and potentially deleterious are increasingly well understood. In addition, reports suggests that humans can tolerate extreme levels of hypercapina for relatively prolonged periods without adverse effects.SummaryThe potential for hypercapnia to contribute to the benificial effects of protective lung ventilatory stratergies is clear from experimental studies. However, the optimal ventilatory stratergy and the percise contribution of hypercapnia to this strategy and the percise contribution of hypercapnia to this strategy remain nuclear. A clearer understanding of its effcects and mechanisms of action is central to determining the safey and therapeutic utility of hypercapina in protective lung ventilatory stratergies.