High altitude pulmonary oedema--response to exercise and cold on systemic and pulmonary vascular beds.

Fourteen subjects who were acclimatised to a height of 7000 feet (average duration 3 ± months) were investigated. Five were normal subjects (Group I) and 9 were those who developed high altitude pulmonary oedema (Group 2). At the National Institute of Heart Diseases, Rawalpindi, clinical examination, chest X-ray, electrocardiogram, haematological tests, thyroid functions, echocardiography and lung function tests were normal. During exercise testing the blood pressure response was exaggerated in Group 2 compared to Group 1 (P <0.01). Cardiac catheterisation revealed no significant difference in the intracardiac pressures in the resting state in the two groups (P = NS). With cold pressor test the pulmonary pressure and aortic pressure rose significantly in Group 2 as compared to Group 1 (P < 0.01). It is suggested, therefore, that pulmohary and systemic vascular beds are hyper-responsive to cold in the susceptible subjects (Group 2). This phenomenon may be further aggravated by exertion, hypoxia, and other undetermined factors in producing pulmonary oedema (JPMA 38: 211, 1988).