Influence of lung volume, glossopharyngeal inhalation and PET O2 and PET CO2 on apnea performance in trained breath-hold divers

Breath-hold divers train and compete in maximal apnea performance. Glossopharyngeal inhalation (GI) is commonly used to increase lung volume above vital capacity (VC) prior to apnea. We investigated the hypothesis that this practice would increase apnea performance and relaxed airway pressure. Seven well-trained breath-hold divers performed maximal bouts of apnea at three different lung volumes (85% VC, VC and VC + GI) both at rest (dry static apnea) and during underwater swimming (dynamic apnea). Heart rate, apnea time and end tidal PCO2 and PO2 (PET CO2 and PET O2) were recorded. In addition, relaxed airway pressure was measured after GI. Maximal GI increased lung volume by 1.59±0.57 l above VC and increased relaxed airway pressure to from 3.5±0.5 to 8.7±1.7 kPa. Dry static apnea time was higher at VC + GI (346±46 s) than at VC (309±38 s, P<0.05) and 85% VC (297±48 s, P<0.01). Likewise, dynamic apnea time was higher at VC + GI (97±27 s) than at VC (78±14 s, P<0.05) and 85% VC (71±17 s, P<0.05). PET O2 values reached 3.5±0.6 kPa at the end of dry static apnea bouts and this was not different from dynamic apnea when taking hydrostatic pressure at swimming depth into account (3.7±0.6 kPa, P=0.48). In conclusion, GI increases lung volume, relaxed airway pressure and apnea performance in well-trained breath-hold divers.