Friday April 7, 2006
The Bohr Effect and Permissive Hypercapnia
One of the physiologic basis of permissive hypercapnia is to increase unload of oxygen to tissues under decrease PH, call Bohr Effect. The Bohr Effect is an adaptation to release oxygen to the starved tissues in conditions where respiratory carbon dioxide lowers blood pH. When blood pH decreases, the ability of hemoglobin to bind to oxygen decreases, classically said "shifting of oxygen dissociation curve to the right", although the SaO2 may be relatively low. This leads many experts to ask the question - is permissive hypoxemia really bad? 2
In depth, there are many other implications of permissive hypercapnia including suppressive effects on inflammatory mechanisms that may contribute to lung protection with therapeutic hypercapnia. Read informative article implications for permissive and therapeutic hypercapnia (D.A. Kregenow and E.R. Swenson, Division of Pulmonary and Critical Care Medicine, University of Washington, Seattle, WA, USA - Reference: Eur Respir J 2002; 20:6-11)
Reference:
1. Respiratory Function of Hemoglobin - Volume 338:239-248, January 22, 1998
2. Permissive Hypoxemia: Is It Time To Change Our Approach? Abdelsalam Chest.2006; 129: 210-211
