[Effect of surgical positioning and spinal anesthesia on lung function]

Various surgical positions, e.g., lithotomy, prone, or head-down positions influence respiratory mechanics. The aim of the present paper was to investigate whether particular surgical positions (lithotomy, lithotomy with head-down tilt, prone, prone with a roller placed under the abdomen) as well as spinal anaesthesia in lithotomy position impair the pulmonary function to a greater extent than supine position and whether they have to be considered as increasing the perioperative risk in elderly patients and patients with ventilatory disorders.

In two separate experimental series, we examined a) the influence of the surgical positions on the pulmonary function in 45 subjects (25 without and 20 with ventilatory disorders) and b) the effects of spinal anaesthesia in 25 urologic patients (9 without and 16 with ventilatory disorders). Static and dynamic lung function parameters were determined. Under spinal anaesthesia, the arterial O2 saturation and the end-expiratory partial pressure of CO2 were measured additionally.

The most pronounced lung function decrease occurred with the transition from seated to supine position. Lithotomy and prone positions impaired the respiratory function only slightly. In elderly persons and in patients with ventilatory disorders, the spirometric changes tended to be stronger than in young persons, but were not considered to increase the perioperative pulmonary risk. A combination of lithotomy position and spinal anaesthesia did likewise not remarkably impair the respiratory function.

Lithotomy and prone positions as well as spinal anaesthesia are not considered to be an additional risk factor for pulmonary function.