HOW FAR CAN WE GO WITH PERMISSIVE HYPERCAPNIA - A CASE PRESENTATION AND SOME BIASED COMMENTS WITH EMPHASIS ON MAINTAINING NORMAL HEMOGLOBINLEVEL

The respiratory management strategy of small tidal volume with permiss ive hypercapnia has been adopted to avoid further aggravation of lung injury due to high airway pressure with some impressive success (1). N o consensus, however, has been established in terms of the rate of inc rease in PaCO2 and its upper limit. Recently, our colleague in the int ensive care unit experienced a severe case of ARDS successfully treate d with the above strategy despite of the fact that during the course o f treatment, the highest PaCO2 reached 177 mmHg and the lowest pH, 7.0 3 (2). The fact that PaCO2 may reach a very high level in the clinical setting and the well-known role of haemoglobin (Hb) in buffering CO2 led us to study effects of different Hb levels on pH and haemodynamic changes in response to acute CO2 loading in the blood. We will summari ze the case report first with permission of authors (the case report w as published in Japanese) (2) and then discuss the studies conducted i n our animal laboratory.