Severe postoperative hypoxaemia during sleep may increase the risk of postoperative cardiovascular complications. We hypothesized that the severity of hypoxic episodes after surgery are related to the presence of preoperative sleep-disordered breathing (SDB). We tested this hypothesis in a multicentre study designed to elucidate the major risk factors for development of postoperative nocturnal desaturations. We performed overnight oximetry before operation and for one night between the second and fourth day after operation in 80 patients undergoing major surgery. We calculated oximetry variables such as oxygen desaturation index (ODI), defined as the number of oxygen desaturations exceeding 4% below baseline, percentage time spent at SpO2 < 90% (CT90, %) and lowest SpO2 value. After operation, although the change in ODI was not significant (P = 0.34), deterioration in CT90 and lowest SpO2 values were significant (P = 0.036 and P = 0.007, respectively). Multivariate analysis of possible risk factors for postoperative desaturations revealed that preoperative hypoxaemia and apnoea witnessed by others were highly correlated with postoperative hypoxaemia.

No abstract

The respiratory management strategy of small tidal volume with permissive hypercapnia has been adopted to avoid further aggravation of lung injury due to high airway pressure with some impressive success (1). No consensus, however, has been established in terms of the rate of increase in PaCO? and its upper limit. Recently, our colleague in the intensive care unit experienced a severe case of ARDS successfully treated with the above strategy despite of the fact that during the course of treatment, the highest PaC02 reached 177 mmHg and the lowest pH, 7.03 (2). The fact that PaCO, may reach a very high level in the clinical setting and the well-known role of haemoglobin (Hb) in buffering CO, led us to study effects of different Hb levels on pH and haemodynamic changes in response to acute CO, loading in the blood. We will summarize the case report first with permission of authors (the case report was published in Japanese) (2) and then discuss the studies conducted in our animal laboratory.

No abstract

The influence of expiratory time on the arterial to end-tidal carbon dioxide tension