[Effect of different pre-oxygenation procedures on arterial oxygen status]

There are different opinions regarding efficiency, duration, and techniques of preoxygenation. It was the aim of our study to systematically investigate the effectiveness of different preoxygenation methods by means of arterial blood gas parameters (paO2, SaO2, and CaO2). METHODS. After receiving informed consent, 80 patients undergoing coronary bypass grafting (NY-HA II-III, ASA III-IV, mean age 57 years) were randomized in eight groups, each with a different preoxygenation technique (Table 1). During normocapnic preoxygenation (Table 2), the following parameters were compared: duration of preoxygenation (3 vs. 5 min), manner of holding the face mask (tightly fitting vs. one digit away from mouth and nose), and oxygen flow (6 vs. 10 l/min) via anesthesia circuit system. Arterial blood gases were analyzed with a Corning 170 pH/blood gas analyzer and a Corning 2500 CO-oximeter. For statistical analysis Student's t-test was used. P less than or equal to 0.01 was considered to be significant (*). RESULTS. As Fig. 1 shows, the different preoxygenation techniques affected paO2 values differently: oxygen flow had a greater influence than duration of preoxygenation. Most important was the manner of holding the face mask. With a tightly fitting mask, preoxygenation was more effective than with the face mask one digit away from mouth and nose, independent of preoxygenation time and oxygen flow (Table 3). The SaO2 (Fig. 2) increased in the same manner with the different preoxygenation techniques from 94.0% to 97.5% (Table 3); CaO2 (Fig. 3) was influenced in a similar way (16.7 ml/dl to 17.4 ml/dl).(ABSTRACT TRUNCATED AT 250 WORDS)