Altitude-related cough

Abstract

Altitude-related cough is a troublesome condition of uncertain aetiology that affects many visitors to high altitude. The traditionally held belief that it was due solely to the inspiration of cold, dry air was refuted by observations and experiments in long duration hypobaric chamber studies. It is likely that altitude-related cough is a symptom of a number of possible perturbations in the cough reflex arc that may exist independently or together. These include loss of water from the respiratory tract; respiratory tract infections and sub-clinical high altitude pulmonary oedema. The published work on altitude-related cough is reviewed and possible aetiologies for the condition are discussed.

Figure 1

Nocturnal cough frequency in 10 subjects during a trek to Mount Everest Base Camp, Nepal (5300 m), including 3 climbers in whom recordings were made at 7000 m on Mount Everest. Recordings were only possible in 3 subjects at between 4 and 5000 m due to logistical problems. The circled data point represents a climber in whom the recorder suffered battery failure after only 1 hour. Data plotted from [6].

Figure 2

Nocturnal cough frequency in the eight subjects taking part in Operation Everest III. R5000m: Return to 5000 m, RSL: Return to Sea Level. Data plotted from [8].

Figure 3

Sample HCVR plot from subject at sea level and after 2 and 8 days at 5800m. Data from [13]. CVR is quantified by the slope S and the end-tidal PCO₂ for a ventilation of 15 l/min.

Figure 4

Number of coughs in excess of baseline (Cough); respiratory water loss (RWE) and respiratory heat loss (RHE) in 7 subjects with exercise-induced cough during a 19 minute period after 4 minutes of hyperpnoea with cold air at -16°C or warm, dry air at 38.7°C. Both the cold air and the warm dry air had a water content of 0 g m^-3. From [60].