The Safety of Trekking at High Altitude After Coronary Bypass Surgery-Reply

In Reply.—  Dr Hultgren raises some interesting points. However, I stand by our original contention that a patient who has had coronary bypass surgery would undergo some risk by trekking to an altitude of 5760 m (19 008 ft).There is overwhelming evidence of severe arterial hypoxemia at this great altitude irrespective of whether the trekker is well-acclimatized. For example, when a group of physiologists lived at a similar altitude of 5800 m (19 140 ft) for several months during the Himalayan Scientific and Mountaineering Expedition of 1960 to 1961, the mean arterial oxygen saturation was only 67% at rest and fell further during exercise.¹ The calculated resting arterial oxygen partial pressure (PO₂) was only 36 mm Hg. Such a low arterial PO₂ must cause severe tissue hypoxia.Although the 51-year-old patient had a coronary artery bypass with apparently excellent results, it is unreasonable to assume that