Lung Perfusion And Chest Wall Configuration Is Altered By Glossopharyngeal Breathing
Authors: L. M. Seccombe, S. C. S. Chung, C. R. Jenkins, C. J. Frater, D. W. J. Mackey, M. A. Pearson, L. Emmett, M. J. Peters
DOI / Source: 10.1183/09031936.00163209
Date: 08 December 2009
Reading level: Intermediate
Why This Matters for Freedivers
Packing can create lung regions that are “full of air but not getting blood.” That means some of the extra air you worked hard to pack may contribute less to oxygen delivery than you’d expect, while still adding the cardiovascular stress that can cause dizziness or fainting. It’s a good reminder that packing changes not just lung volume, but how the lungs and circulation behave together.
Synopsis
Freedivers use glossopharyngeal breathing (often called “lung packing”) to push lung volume above normal total lung capacity. The basic idea is simple: more gas in the lungs can mean more oxygen stored and more “volume buffer” as the chest compresses with depth. But packing also increases pressure inside the chest and stretches the lungs into shapes they don’t normally reach. This study looked at a question most freedivers never consider: when you hyperinflate the lungs like that, does blood still flow through the expanded areas normally?
Six competitive male breath-hold divers took part. The researchers measured how much extra volume each diver could add with packing, then did detailed imaging in a controlled, supine (lying down) position: a CT scan to see how the chest and lungs physically changed, and a perfusion scan (using a tracer that lodges in the lung circulation) to map where blood was actually flowing.
Most divers increased their exhaled vital capacity by around 20% (about 1.4 liters). The CT scans showed that this extra volume was not just “compressed air.” About two-thirds of the increase came from real expansion of the thorax: the rib cage expanded, the diaphragm shifted downward, lung tissue bulged between ribs, and the mediastinum (the central area where the heart and major vessels sit) shifted. In other words, packing physically rearranged the inside of the chest.
The perfusion imaging revealed the most important result: areas of the lung that became most expanded were also the areas where blood flow dropped substantially — in some places approaching absent. In plain terms, packing created patches of lung that were well aerated but poorly perfused. That matters because oxygen transfer depends on both air reaching the alveoli and blood reaching the capillaries. If you inflate regions that lose perfusion, you can end up with “dead-space-like” areas: air is there, but it contributes less to oxygen delivery.
Interestingly, one diver who wasn’t proficient at packing did not show these changes — his lung shape and perfusion stayed essentially the same. The authors also mention practical problems they observed during testing, including a syncope episode in one subject during attempts at maximal packing, reinforcing that this maneuver can have real immediate physiological consequences.
The takeaway is not that packing is always useless, but that it can come with a hidden trade-off: part of the extra air may sit in regions that receive less blood flow, so the oxygen benefit may be smaller than expected while the mechanical and circulatory stress remains. Body position and how “extreme” the packing is likely influence how strong these effects become.
Abstract
Glossopharyngeal insufflation is used by competitive breath-hold divers to increase lung gas content above baseline total lung capacity (TLC) in order improve performance. Whilst glossopharyngeal insufflation is known to induce hypotension and tachycardia, little is known about the effects on the pulmonary circulation and structural integrity of the thorax. Six male breath-hold divers were studied. Exhaled lung volumes were measured before and after glossopharyngeal insufflation. On two study days, subjects were studied in the supine position at baseline TLC and after maximal glossopharyngeal insufflation above TLC. Tc 99m labelled macro-aggregated albumin was injected and a computed tomography (CT) scan of the thorax was performed during breath-hold. Single photon emission CT images determined flow and regional deposition. Registered CT images determined change in the volume of the thorax. CT and perfusion comparisons were possible in four subjects. Lung perfusion was markedly diminished in areas of expanded lung. 69% of the increase in expired lung volume was via thoracic expansion with a caudal displacement of the diaphragm. One subject who was not proficient at glossopharyngeal insufflation had no change in CT appearance or lung perfusion. We have demonstrated areas of hyperexpanded, under perfused lung created by glossopharyngeal insufflation above TLC.