[A case of ventilation disorder and poor oxygenation after changing position from prone to supine].

A 68-year-old obese woman (BMI 35) underwent posterior lumbar interbody fusion in prone position. Immediately after changing position postoperatively from prone to supine, severe ventilation disorder and poor oxygenation occured. Chest X-ray showed severe atelectasis. Poor oxygenation was suspected to be the result of the atelectasis by the pressure of massive abdominal fatty tissue to the diaphragm. Ventilation disorder was suspected of the bronchospasm associated with inadequate anesthesia. We ventilated her manually with a bag in Fowler position for twenty minutes, and then mechanically by pressure controlled ventilation. She recovered gradually. It is concluded that in obese patients undergoing operation in prone position, changing position should be done very carefully during adequate anesthesia, understanding respiratory physiology in positioning and considering the effect of the abdominal fatty tissue to the diaphragm.