Postural hypoxemia in quadriplegic patients

Quadriplegic patients frequently undergo unusual positional changes, including head-down tilt. To determine if hypoxemia develops in this position and whether it is related to the duration of quadriplegia, five patients were studied within 1 year of injury (group A) and five after 1 year from injury (group B). Arterial blood gases were obtained in the seated and 45-degree head-down position. Group A patients had a decrease in arterial partial pressure of oxygen in the head-down position (p 0.4). This study demonstrated that quadriplegic patients have positional hypoxemia early in their course. This probably results from relative hypoventilation of the upper lung fields caused by flaccid paralysis of the intercostal muscles. The positional hypoxemia disappears with time, presumably because of the change from flaccid to spastic paralysis of the intercostal muscles.