Characteristics of the respiratory mechanical and muscle function of competitive breath-hold divers

Competitive breath-hold divers (BHD) employ glossopharyngeal insufflation (GI) to increase intrapulmonary oxygen stores and prevent the lungs from dangerous compressions at great depths. Glossopharyngeal insufflation is associated with inflation of the lungs beyond total lung capacity (TLC). It is currently unknown whether GI transiently over-distends the lungs or adversely affects lung elastic properties in the long-term. Resting lung function, ventilatory drive, muscle strength, and lung compliance were measured in eight BHD who performed GI since 5.5 (range 2–6) years on average, eight scuba divers, and eight control subjects. In five BHD subsequent measures of static lung compliance (Cstat) were obtained after 1 and 3 min following GI. Breath-hold divers had higher than predicted ventilatory flows and volumes and did not differ from control groups with regard to gas transfer, inspiratory muscle strength, and lung compliance. A blunted response to CO₂ was obtained in BHD as compared to control groups. Upon GI there was an increase in mean vital capacity (VC_GI) by 1.75 ± 0.85 (SD) L compared to baseline (p < 0.001). In five BHD Cstat raised from 3.7 (range 2.9–6.8) L/kPa at baseline to 8.1 (range 3.4–21.2) L/kPa after maximal GI and thereafter gradually decreased to 5.6 (range 3.3–8.1) L/kPa after 1 min and 4.2 (range 2.7–6.6) L/kPa after 3 min (p < 0.01). We conclude that in experienced BHD there is a transient alteration in lung elastic recoil. Resting lung function did not reveal a pattern indicative of altered lung ventilatory or muscle function.