Pulmonary oedema induced by strenuous swimming: a field study

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Abstract

The purpose of the study was to document the incidence and recurrence rate of pulmonary oedema induced by strenuous swimming (SIPO), and to study the changes in relevant physiological parameters. Thirty-five young men were repeatedly examined over a 2-month period after a swimming time trial in the open sea. A tentative diagnosis of SIPO was made when the swimmer reported shortness of breath accompanied by cough. Twenty-nine events of SIPO were diagnosed in 21 individuals (60% incidence). Oxygen saturation was significantly reduced in SIPO. Mean forced vital capacity (FVC) and FEV1 were significantly lower in the severe SIPO group. Also, mean FVC and mid-expiratory flows (FEF25–75%) obtained 12 months earlier during screening for the programme were lower in individuals who later had SIPO. The ratios of post-swim FVC and FEV1 values to the corresponding selection examination values were lower in the severe SIPO group. Thus volumes decreased in the SIPO group, besides being lower at the start. Shortness of breath and coughing following strenuous swimming were related to hypoxaemia and reduction in lung volumes, suggesting pulmonary oedema. SIPO was a common and often recurrent phenomenon. Lower initial lung volumes and flows might predict future susceptibility to SIPO.

Introduction

We previously reported a series of swimmers who suffered from pulmonary oedema and haemoptysis during a single swimming time trial over 2.4 km in the open sea in the spring of 1994 (Weiler-Ravell et al., 1995). Eight of the 30 otherwise healthy young males who participated in that trial developed the syndrome. The sea was calm and the measured water temperature was 23°C. In that particular event, overhydration was suggested to be an important contributing factor. However, two of the swimmers had recurrent episodes and other new cases were diagnosed, all associated with strenuous swimming albeit without water over-load.

Three other reports describe pulmonary oedema during immersion. Wilmshurst et al. (1989) reported on 11 divers with no demonstrable cardiac abnormality who suffered from pulmonary oedema. All events occurred during immersion in cold water, at a temperature below 12°C, and were not associated with heavy exercise. The patients all had an abnormal cold pressor test with increased vascular resistance. During a follow-up period of 1–16 years, seven of the 12 developed hypertension. Pons et al. (1995) reported four cases of pulmonary oedema during scuba diving or swimming. Some of the events occurred at a water temperature of 18–20°C. Cardiac evaluation was normal and no pathological hypertensive response was found in the cold pressor test. Hampson and Dunford (1997) described six individuals who had acute pulmonary oedema associated with diving. Five cases occurred in cold water and one in Cozumel, Mexico in 27°C water. One of the patients had a prior history of hypertension and mitral valve prolapse. In all cases, cardiac evaluation following recovery from the acute episode was normal. A recent personal communication (KC Walters, MD, US Navy) describes the occurrence of pulmonary oedema, induced by strenuous swimming among Special Forces (SEAL) trainees who regularly swim 1.6–8.8 km.

The purpose of the present study was to learn about the incidence and recurrence rate of strenuous swimming-induced pulmonary oedema (SIPO) in a cohort of healthy, fit trainees and to identify changes in relevant physiological parameters that might contribute to our understanding of this phenomenon.

Section snippets

Subjects

Thirty-five young men aged 18–19 years, who were on a fitness-training programme, were examined after a swimming time trial in the open sea, on five occasions over a 2-month period (mid January–mid March). The subjects were all healthy at the time of the trial, and had no history of respiratory diseases. None of the study participants was or had been a habitual smoker, although some smoked occasionally (2–3 cigarettes daily) for 1–2 years. The water temperature during the study period ranged

Incidence of SIPO

During the study period, we encountered 29 events of SIPO in 21 individuals — 60% of the group. Twenty-one episodes were categorised as ‘mild’ and the remaining eight as ‘severe’. The recurrence rate was significantly higher after ‘severe’ SIPO events (P<0.002, χ2). Of the eight severe SIPO events, six (75%) occurred after a previous mild or severe event. Of the 21 mild events, three (14%) were the recurrence of a previous event. In most cases, symptoms appeared during the first swim to 2.4 km

Discussion

Stress failure of the pulmonary capillaries was suggested and later described by West et al. as an explanation for exercise induced pulmonary oedema in thoroughbred racehorses (West et al., 1991, West et al., 1993, West and Mathieu-Costello, 1992). Pulmonary oedema induced by swimming or diving might be related to the same pathophysiological concept. The principal forces that might cause failure of the pulmonary capillary in the alveolar wall are the transmural pulmonary capillary hydrostatic

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