Cardiac Magnetic Resonance Imaging during Pulmonary Hyperinflation in Apnea Divers
Authors: Tonci Batinic, Wolfgang Utz, Toni Breskovic, Jens Jordan, Jeanette Schulz-Menger, Stipan Jankovic, Zeljko Dujic, Jens Tank
DOI / Source: 10.1249/MSS.0b013e31821ff294
Date: 2011
Reading level: Intermediate
Why This Matters for Freedivers
Lung packing can meaningfully change your circulation even before you start the dive. This paper shows that packing can reduce how much blood the heart fills with and how much it pumps, which helps explain why some divers feel dizzy or even faint after packing—especially if they do it aggressively or while standing.
Synopsis
Many competitive freedivers “lung pack” (glossopharyngeal insufflation) to squeeze extra air into the lungs after a full inhale. It can help with equalisation and performance, but divers have long reported a downside: sudden light-headedness and low blood pressure. This study used cardiac MRI—one of the most accurate ways to measure heart chamber volumes—to see exactly what packing does to the heart during a breath-hold.
Eleven trained apnea divers were scanned in three conditions: (1) at a relaxed baseline lung volume, (2) during a maximal inhale breath-hold (total lung capacity), and (3) during a breath-hold after submaximal packing (a controlled amount of packing for safety). The key finding was that simply holding at full lungs already shrinks how much blood returns to the heart: both the left and right ventricles filled with much less blood than at baseline, and cardiac output dropped by about a third. When the divers added packing on top, cardiac output fell further—again in both ventricles.
Importantly, the heart’s pumping “strength” (ejection fraction) only dropped modestly. That suggests the main problem isn’t that the heart suddenly becomes weak—it’s that the heart has less blood available to pump because high chest pressure and overinflated lungs reduce venous return and distort heart geometry. Over the next minutes of the breath-hold, there was a small partial recovery in filling and cardiac output, but the initial drop was the big effect.
In plain terms: packing makes the chest a tighter, higher-pressure space, and the heart can’t fill normally. That’s the mechanical reason packing can trigger dizziness, low blood pressure, and in some divers even fainting—especially if they push packing hard.
Abstract
Purpose: Apnea divers hyperinflate the lung by taking a deep breath followed by glossopharyngeal insufflation. The maneuver can lead to symptomatic arterial hypotension. We tested the hypotheses that glossopharyngeal insufflation interferes with cardiac function further reducing cardiac output (CO) using cardiac magnetic resonance imaging (MRI) to fully sample both cardiac chambers.
Methods: Eleven dive athletes (10 men, 1 woman) underwent cardiac MRI during breath holding at functional residual capacity (baseline), at total lung capacity (apnea), and with submaximal glossopharyngeal insufflation. Lung volumes were estimated from anatomic images. Short-axis cine MR images were acquired to study biventricular function. Dynamic changes were followed by long-axis cine MRI.
Results: Left and right ventricular end-diastolic volumes decreased during apnea with and without glossopharyngeal insufflation. CO decreased during apnea decreasing further with glossopharyngeal insufflation. Heart rate increased with apnea and with glossopharyngeal insufflation. Ejection fraction moderately decreased. With continued apnea with and without glossopharyngeal insufflation, end-diastolic volume and CO increased over time by a similar but small amount.
Conclusions: Submaximal glossopharyngeal insufflation decreased CO further albeit by a small amount compared to maximal inspiratory apnea. The response was not associated with severe biventricular dysfunction.