Glossopharyngeal insufflation causes lung injury in trained breath-hold divers.
Chung SC, Seccombe LM, Jenkins CR, Frater CJ, Ridley LJ, Peters MJ.
Department of Thoracic Medicine, Concord Repatriation General Hospital, Concord, Sydney, New South Wales, Australia.
Abstract
ABSTRACT Background and objective: Glossopharyngeal insufflation (GI) is a technique practised by competitive breath-hold divers to enhance their performance. Using the oropharyngeal musculature, air is pumped into the lungs to increase the lung volume above physiological TLC. Experienced breath-hold divers can increase their lung volumes by up to 3 L. Although the potential for lung injury is evident, there is limited information available. The aim of this study was to examine whether there is any evidence of lung injury following GI, independent of diving. Methods: Six male, competitive breath-hold divers were studied. CT of the thorax was performed during breath-holding at supramaximal lung volumes following GI (CT(GI)), and subsequently at baseline TLC (CT(TLC)). CT scans were performed a minimum of 3 days apart. Images were analysed for evidence of pneumomediastinum or pneumothorax by investigators who were blinded to the procedure. Results: None of the subjects showed symptoms or signs of pneumomediastinum. However, in five of six subjects a pneumomediastinum was detected during the CT(GI). In three subjects a pneumomediastinum was detected on the CT(GI), but had resolved by the time of the CT(TLC). In two subjects a pneumomediastinum was seen on both the CT(GI) and the CT(TLC), and these were larger on the day that a maximal GI manoeuvre had been performed. The single subject, in whom a pneumomediastinum was not detected, was demonstrated separately to not be proficient at GI. Conclusions: Barotrauma was observed in breath-hold divers who increased their lung volumes by GI. The long-term effects of this barotrauma are uncertain and longitudinal studies are required to assess cumulative lung damage.
Well, in short, in five out of six divers, pneumomediastinum (which means that air is present in the mediastinum, which is the central compartment of the thoracic cavity) was observed. My interpretation is that a possible cause of the pneumomediastinum could be that there was an alveolar rupture caused by the GI/packing, allowing air to escape into the mediastinum. Rupture in some other part(s) of the airways besides the alveoli is also a possibility.
The authors of the study writes: "The single subject, in whom a pneumomediastinum was not detected, was demonstrated separately to not be proficient at GI". It could mean that this diver was unable to pack his/her lungs to such an extent that alveolar rupture occurred. This would be in accordance with what is known about lung volumes, airway pressures, and risks for pulmonary barotrauma/volutrauma.
Furthermore, the authors state "The long-term effects of this barotrauma are uncertain and longitudinal studies are required to assess cumulative lung damage". This means that even though the divers did not experience any acute symptoms, it can not be excluded that there could be long-term damage to the lungs from e.g. repetitive pneumomedistinum. Overinflation of the lungs by GI above the TLC is a relatively new practice (at least within a larger population), and therefore not much is known about the long-term risks with this practice.
I pulled this from the web, not my words.
Don Paul
