The Key Roles of Negative Pressure Breathing and Exercise in the Development of Interstitial Pulmonary Edema in Professional Male SCUBA Divers

Olivier Castagna,Romain Chopard,Emmanuel Gempp,Pierre Louge,François Xavier Brocq,Adrien Maurin,Anne-Virginie Desruelle,Bruno Schmid,Valentin Crunel,David Hunter Maciver,Jacques Regnard

doi:10.1186/s40798-017-0116-x

Abstract

BackgroundImmersion pulmonary edema is potentially a catastrophic condition; however, the pathophysiological mechanisms are ill-defined. This study assessed the individual and combined effects of exertion and negative pressure breathing on the cardiovascular system during the development of pulmonary edema in SCUBA divers.MethodsSixteen male professional SCUBA divers performed four SCUBA dives in a freshwater pool at 1 m depth while breathing air at either a positive or negative pressure both at rest or with exercise. Echocardiography and lung ultrasound were used to assess the cardiovascular changes and lung comet score (a measure of interstitial pulmonary edema).ResultsThe ultrasound lung comet score was 0 following both the dives at rest regardless of breathing pressure. Following exercise, the mean comet score rose to 4.2 with positive pressure breathing and increased to 15.1 with negative pressure breathing. The development of interstitial pulmonary edema was significantly related to inferior vena cava diameter, right atrial area, tricuspid annular plane systolic excursion, right ventricular fractional area change, and pulmonary artery pressure. Exercise combined with negative pressure breathing induced the greatest changes in these cardiovascular indices and lung comet score.ConclusionsA diver using negative pressure breathing while exercising is at greatest risk of developing interstitial pulmonary edema. The development of immersion pulmonary edema is closely related to hemodynamic changes in the right but not the left ventricle. Our findings have important implications for divers and understanding the mechanisms of pulmonary edema in other clinical settings.

Highlights

Immersion pulmonary edema is potentially a catastrophic condition; the pathophysiological mechanisms are ill-defined
Exercise tidal volume was almost three times the static value while the breathing rate almost doubled with exercise
Our study showed that immersion at rest causes modest increases in right heart preload, pulmonary artery pressures, and an imbalance in right and left ventricular physiology but without the development of interstitial pulmonary edema

Summary

Introduction

Immersion pulmonary edema is potentially a catastrophic condition; the pathophysiological mechanisms are ill-defined. This study assessed the individual and combined effects of exertion and negative pressure breathing on the cardiovascular system during the development of pulmonary edema in SCUBA divers. Immersion pulmonary edema (IPE) is accompanied by the onset of dyspnea while diving or swimming. IPE may be accompanied by cough, hemoptysis, and severe hypoxemia and can result in death [1,2,3]. The main predisposing factors to IPE [5] are cold water [3, 6] and exertion [7, 8]. IPE symptoms can vary in severity [10], and the accumulation of interstitial pulmonary edema without overt symptoms is common after normal diving without significant exertional effort [11]. The rise in transmural pulmonary capillary pressure causes transudation initially into the interstitial tissues, [13] as evidenced by the appearance of ultrasound “lung comet tails,” [14] before reaching the alveolar air spaces [15]

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