The effects of rapid changes of altitude on patients undergoing pneumotherapy.

That flying involves at least a theoretical hazard to individuals with closed pneumothorax has long been known. Many observers have made references to the simple application of Boyle’s law, concerning the reciprocal relationship of volume and pressure of gases. In 1942 Lovelace and Hinshaw2 reported a roentgenographic demonstration of the effect of altitude on a series of patients, utilizing a low-pressure chamber rather than an airplane. Their pictures demonstrate definite enlargement of pneumothorax space, in rough proportion to decreased barometric pressure (simulated increase of altitude). They conclude, in part, that “it would appear to be extremely important to determine whether or not the calculated expansion of pneumothorax during flight actually occurs or whether expansion is restrained and relative positive pressure develops.” In an effort to settle this point and with the broader object of arriving at a rational basis for decision as to which patients undergoing pneumotherapy could fly with safety and which could not, a series of experiments was carried out. (The generic term “pneumotherapy” includes patients with unilateral or bilateral pneumothorax, pneumoperitoneum, and combinations of these procedures with other forms of collapse therapy). The initial study consisted in reading intrapleural and intraperitoneal pressures at the top and bottom of a 25 story elevator shaft-a vertical distance of 294 feet, before and after refills. The theoretical difference in pressure, as customarily recorded in cm. of water on the manometer of a pneumothorax apparatus, would be approximately 10 cm. This was checked by recording the pressure in a liter bottle connected to a water manometer, and found to be correct. An anaeroid barometer rose approximately 0.25 inches (Hg.) during the descent. Patient A, an otherwise healthy young woman who had been receiving pneumoperitoneum for approximately two and a half years for moderately advanced bilateral tuberculosis, then entered the elevator on the top floor to receive a routine weekly refill. Her intraperitoneal pressure was +12±13. Before the administration of air the elevator was taken to the ground floor, where the manometer reading was +11+12. (It should theoretically have been +2+3). After receiving 700 cc. of air, the pressure rose to +16+17. On returning to the top floor, it was found that instead of the theoretical rise in pressure of 10 cm., the manometer still showed +16+17 cm. The experiment was repeated with patient B, likewise a young woman, clinically well, who had been receiving left pneumothorax for six months for a minimal lesion. The initial pressure on the 26th floor was 0-4, and it was unaltered by the descent to the first floor. At this point a routine weekly refill of 400 cc., with the patient still lying comfortably in the prone