This article is part of a series on Ventilator strategy, edited by John J Marini.

Review

Bench-to-bedside review: Permissive hypercapnia

Donall O' Croinin¹, Martina Ni Chonghaile², Brendan Higgins³ and John G Laffey⁴

¹Clinical Research Fellow, Department of Physiology, University College Dublin, Dublin

²Clinical Research Fellow, Department of Anaesthesia, University College Hospital, and Department of Anaesthesia, Clinical Sciences Institute, National University of Ireland, Galway, Ireland

³Postdoctoral Research Fellow, Department of Anaesthesia, Clinical Sciences Institute, National University of Ireland, Galway, Ireland

⁴Clinical Lecturer, Department of Anaesthesia, University College Hospital, and Department of Anaesthesia, Clinical Sciences Institute, National University of Ireland, Galway, Ireland

author email corresponding author email

Critical Care 2005, 9:51-59doi:10.1186/cc2918

Published:	5 August 2004

Abstract

Current protective lung ventilation strategies commonly involve hypercapnia. This approach has resulted in an increase in the clinical acceptability of elevated carbon dioxide tension, with hypoventilation and hypercapnia 'permitted' in order to avoid the deleterious effects of high lung stretch. Advances in our understanding of the biology of hypercapnia have prompted consideration of the potential for hypercapnia to play an active role in the pathogenesis of inflammation and tissue injury. In fact, hypercapnia may protect against lung and systemic organ injury independently of ventilator strategy. However, there are no clinical data evaluating the direct effects of hypercapnia per se in acute lung injury. This article reviews the current clinical status of permissive hypercapnia, discusses insights gained to date from basic scientific studies of hypercapnia and acidosis, identifies key unresolved concerns regarding hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.