A simulation study to compare physiological responses to hypoxia and exercise between anaemic subjects and healthy controls

Military flying is a complex task and requires high level of physical fitness of aviators. Various aviation stressors such as acceleratory force, hypoxia, cold weather conditions and decompression sickness place enormous stress on human physiological systems of the aviators. Individuals with Hb <13 g/dL (males) are being placed in the lower medical category which makes them unfit to fly. The present study was undertaken to assess the implication of low haemoglobin (Hb) on exercise capacity and hypoxia tolerance. Twenty-five individuals with anaemia and 15 healthy controls participated in the study. The participants were subjected to normobaric hypoxia (NH) equivalent to an altitude of 15,000 feet. Different physiological parameters such as heart rate (HR), systolic and diastolic blood pressure (SBP and DBP), respiratory rate (fR) and arterial oxygen saturation (SpO2) were measured during NH. Participants also performed maximal aerobic capacity (VO2 max) and maximal anaerobic capacity test in bicycle ergometer. HR, SBP, DBP and fR in anaemic subjects were higher than healthy controls during NH, whereas SpO2 in anaemic subjects was lower as compared to healthy controls. Anaemic individuals had a lower VO2 max than their healthy counterparts. Critical power and anaerobic work capacity were lower in anaemic subjects than healthy controls. There is a deterioration in exercise capacity and hypoxia tolerance in individuals with low Hb levels. Adequate precaution should be exercised for permitting military aviators to fly with low Hb level.