Evidence of respiratory system remodeling in a competitive freediver: a competitive advantage?

Introduction: Glossopharyngeal insuffl ation (GI) is commonly employed by freedivers to increase oxygen stores for depth and duration events. Lung barotrauma has been associated with GI, which raises the possibility that use of this technique results in lung damage and physiological impairment. Paradoxically, these alterations in the respiratory system may be performance enhancing. We sought to characterize the nature of any changes in the respiratory system that may be associated with GI, using physiological measurement and imaging. Methods: The research data from a healthy competitive freediver who practised regular GI training was reviewed. Lung function was sequentially measured, including volumes achieved with a maximal GI manoeuvre. Non-contrast computed tomography (CT) of the thorax taken at baseline and following GI on a single occasion were segmented for 3D analysis of lung tissue. Results: Lung function was measured over a period of eight years (from age 25 to 33 years) on four occasions. There was progressive baseline lung hyperinflation with a total >800 mL increase in baseline VC, FRC and TLC. There was no evidence of gas trapping as RV remained unchanged, and TLCO was preserved. The subject was adept at GI; however, there was an observed limit to maximal absolute volume achieved above traditional TLC despite ongoing GI raining. Rendered 3D images of lung tissue demonstrated significant lung hyperinflation following GI, with intercostal bulging of lung tissue, mediastinal distortion and flattening of the diaphragm. A pneumomediastinum was evident on the GI scan. Conclusion: We present a healthy freediving subject with progressively increasing baseline lung volumes associated with repeated performance of an intervention used to enhance athletic performance. However, the upper limit of TLC with GI was stable. The repeated use of GI over time in this case appears to have altered respiratory system mechanics without any functionally important macroscopic lung damage, at least as evidenced by CT scans and measures of gas exchange.