The effect of selective drainage positions on oxygen saturation in obese patients after upper abdominal surgery.

The obese patients undergoing upper abdominal surgery are at particularly high risk to develop postoperative pulmonary complications, and hypoxemia is one of the most common ones reported. During the initial postoperative period, they are often advised to maintain a semi-sitting position to optimize oxygenation. Although chest physical therapy usually avoids a Trendelenburg position, no published data indicate this position as being able to induce desaturation in obese patients following upper abdominal surgery. We studied fifteen adult obese patients without cardiopulmonary disease undergoing upper abdominal surgery. All patients were tested for 5 minutes during the first 3 postoperative days in each of 3 positions: semi-sitting, bed-flat lateral decubitus, and 15 degrees of Trendelenburg lateral decubitus positions. A statistically significant difference in oxygen saturation related to position was found only on the first postoperative day between semi-sitting and bed-flat lateral decubitus positions. The difference in mean SaO2 value between these 2 positions, however, was only 0.88%; and no significant correlation between the magnitude of obesity and the mean SaO2 difference was found. Although arterial oxygen saturation demonstrated statistically significant daily improvement during the first 3 postoperative days, the mean SaO2 values for any 2 consecutive days differed by less than 0.78%. Thus, in obese patients following upper abdominal surgery, 15 degrees of Trendelenburg lateral decubitus and bed-flat lateral decubitus positions do not induce clinically significant desaturation and can be used if necessary and appropriate. In obese patients with borderline oxygenation, supplemental oxygen used postoperatively can maintain adequate oxygenation and allow aggressive positioning.

[The function of 100% O2 suction key in Bennett 7200 microprocessor ventilator].

Tracheal suctioning of a patient on a ventilator may induce hypoxemia. Bennett 7200 microprocessor ventilator has an "100% O2 suction" key which is claimed to provide 100% oxygen for two minutes and switch back automatically when this function is set. Four 7200 ventilators were tested to verify this function. We found that the mean lag time varied from 20.1 seconds to 103.3 seconds and the mean recovery time varied from 33.0 seconds to 134.6 seconds according to the difference of initial tidal volume, ventilator rate and fractional inspired oxygen setting. When the ventilator was on "100% O2 suction", the delivered tidal volume was less than the preset tidal volume. In order to hyper-oxygenate and hyper-inflate the patient to prevent suction-induced hypoxemia, those finding should be taken into consideration when the clinicians apply this function in clinical situation.