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1Department of Anesthesia and Critical Care and 2Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston; 3Physiology Program, Department of Environmental Health, Harvard School of Public Health, and Department of Medicine, Harvard Medical School, Boston, Massachusetts; 4Centre for Environmental Physiology, Department of Physiology and Pharmacology Karolinska Institutet, Stockholm, Sweden; and Departments of 5Radiology and of 6Anesthesiology, Perioperative, and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
Submitted 5 July 2006 ; accepted in final form 7 October 2006
Throughout life, most mammals breathe between maximal and minimal lung volumes determined by respiratory mechanics and muscle strength. In contrast, competitive breath-hold divers exceed these limits when they employ glossopharyngeal insufflation (GI) before a dive to increase lung gas volume (providing additional oxygen and intrapulmonary gas to prevent dangerous chest compression at depths recently greater than 100 m) and glossopharyngeal exsufflation (GE) during descent to draw air from compressed lungs into the pharynx for middle ear pressure equalization. To explore the mechanical effects of these maneuvers on the respiratory system, we measured lung volumes by helium dilution with spirometry and computed tomography and estimated transpulmonary pressures using an esophageal balloon after GI and GE in four competitive breath-hold divers. Maximal lung volume was increased after GI by 0.13–2.84 liters, resulting in volumes 1.5–7.9 SD above predicted values. The amount of gas in the lungs after GI increased by 0.59–4.16 liters, largely due to elevated intrapulmonary pressures of 52–109 cmH2O. The transpulmonary pressures increased after GI to values ranging from 43 to 80 cmH2O, 1.6–2.9 times the expected values at total lung capacity. After GE, lung volumes were reduced by 0.09–0.44 liters, and the corresponding transpulmonary pressures decreased to –15 to –31 cmH2O, suggesting closure of intrapulmonary airways. We conclude that the lungs of some healthy individuals are able to withstand repeated inflation to transpulmonary pressures far greater than those to which they would normally be exposed.
esophageal balloon; barotrauma; pneumomediastinum; chest wall; elastic recoil pressure
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