ABSTRACT
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 pulmonary 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