Gerard Curley , John G Laffey and Edward Abraham. Critical Care 2010, 14:220doi:10.1186/cc8926. Published: 30 April 2010
Abstract (provisional)
Carbon dioxide is a waste product of aerobic cellular respiration in all aerobic life forms. PaCO2 represents the balance between the CO2 produced and that eliminated.
Hypocapnia remains a common – and generally underappreciated – component of many disease states, including early asthma, high altitude pulmonary edema, and acute lung injury. Induction of hypocapnia remains a common, if controversial, practice in both adults and children with acute brain injury. In contrast, hypercapnia has traditionally been avoided in order to keep parameters normal. More recently, advances in our understanding of the role of excessive tidal volume has prompted clinicians to use ventilation strategies that result in hypercapnia. Consequently, hypercapnia has become increasingly prevalent in the critically ill. Hypercapnia may play a beneficial role in the pathogenesis of inflammation and tissue injury, but may hinder the host response to sepsis and reduce repair. In contrast, hypocapnia may be a pathogenic entity in the setting of critical illness. This paper reviews the current clinical status of low and high PaCO2 in the critically ill, discusses the insights gained to date from studies of CO2, identifies key concerns regarding hypo- and hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.
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