Depression of sighing in the first three postoperative days with epidural morphine analgesia

We have studied the effect of spontaneous sighs on maintaining arterial oxygenation in patients receiving epidural morphine for analgesia after upper abdominal surgery. Sixteen patients scheduled for elective gastrectomy were monitored continuously with pulse oximetry and respiratory inductive plethysmography (RIP) during one night preoperatively and for 60 h postoperatively with repeate arterial blood gas analysis. An average of 3.1±1.2 (±SD) sighs were observed per hour preoperatively during sleep while postoperative sighs were significantly depressed to an average less than one per hour throughout the 60 h of the monitoring period (P<0.05). Although postoperative Pao₂ values were significantly lower than preoperative values, there was no correlation between the decreases in Pao₂ values and number of sighs. Thus, it is unlikely that the long-term absence of spontaneous sighs observed may serve as a contributing factor for the long-lasting hypoxemia in the postoperative period.