RESUMEN
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 FEV(1) were significantly lower in the severe SIPO group. Also, mean FVC and mid-expiratory flows (FEF(25-75%)) obtained 12 months earlier during screening for the programme were lower in individuals who later had SIPO. The ratios of post-swim FVC and FEV(1) 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.
Asunto(s)
Edema Pulmonar/etiología , Natación/fisiología , Adolescente , Adulto , Estudios de Cohortes , Volumen Espiratorio Forzado/fisiología , Humanos , Pulmón/fisiología , Masculino , Consumo de Oxígeno/fisiología , Edema Pulmonar/epidemiología , Edema Pulmonar/metabolismo , Recurrencia , Pruebas de Función Respiratoria , Encuestas y CuestionariosRESUMEN
A wet suit may not provide adequate thermal protection when diving in moderately cold water (17-18 degrees C), and any resultant mild hypothermia may impair performance during prolonged diving. We studied heat exchange during a dive to a depth of 5 m in sea water (17-18.5 degrees C) in divers wearing a full wet suit and using closed-circuit oxygen breathing apparatus. Eight fin swimmers dived for 3.1 h and six underwater scooter (UWS) divers propelled themselves through the water for 3.7 h. The measurements taken throughout the dive were the oxygen pressure in the cylinder and skin and rectal temperatures (Tre). Each subject also completed a cold score questionnaire. The Tre decreased continuously in all subjects. Oxygen consumption in the fin divers (1.40 l.min-1) was higher than that of the UWS divers (1.05 l.min-1). The mean total insulation was 0.087 degree C.m2.W-1 in both groups. Mean body insulation was 37% of the total insulation (suit insulation was 63%). The reduction in Tre over the 1st hour was related to subcutaneous fat thickness. There was a correlation between cold score and Tre at the end of 1 h, but not after that. A full wet suit does not appear to provide adequate thermal protection when diving in moderately cold water.
Asunto(s)
Altitud , Temperatura Corporal/fisiología , Buceo/fisiología , Consumo de Oxígeno/fisiología , Recto/fisiología , Temperatura , Humanos , MasculinoRESUMEN
We evaluated CO2 retention in 24 Navy construction divers breathing air at 1 atm abs (101.3 kPa) and 40% O2 (40/60) nitrox at 4 atm abs (Po2 of 162.1 kPa) inside a pressure chamber. The divers sat immersed to the sternal notch and exercised against pneumatically loaded pedals at a Vo2 of approximately 1.3 liter/min. The mean end-tidal CO2 tension (PET(CO2)2) at 1 atm abs (45.7 +/- 5.0 SD torr) was significantly higher than that of non-divers and diving trainees (40 +/- 5.0) but did not increase significantly at depth (47.1 +/- 6.3). The ranking of CO2 retention was not maintained at depth. Unpredictable upward and downward shifts of up to 10 torr occurred in some divers. The PET(CO2) of six of the divers at pressure was greater than 50 torr, which based on animal studies markedly increases the risk of central nervous system oxygen toxicity. We translated their values into individual depth limits with 40/60 nitrox: three with 50 < PET(CO2) < 55 torr were forbidden to dive beyond 25 m and three with values > 55 torr were restricted to 20 m. We propose that whenever possible, PET(CO2) during exercise at pressure be measured in potential nitrox users and that the above PO2 limits be enforced on moderate and extreme CO2 retainers, respectively.
Asunto(s)
Dióxido de Carbono/metabolismo , Buceo/fisiología , Ejercicio Físico/fisiología , Adulto , Humanos , Masculino , Persona de Mediana Edad , Nitrógeno/administración & dosificación , Nitrógeno/metabolismo , Oxígeno/administración & dosificación , Oxígeno/metabolismo , Presión Parcial , Volumen de Ventilación Pulmonar/fisiologíaRESUMEN
A central hypoventilatory state developed in a 6-month-old boy with environmentally induced hyperthermia. The condition subsided within 24 hours of mechanical ventilation. Hypoxic and hypercapneic challenges performed 2 weeks later showed complete resolution of the respiratory chemoreceptor dysfunction. The damage to the CNS caused by accidental hyperthermia in general, and more specifically to the respiratory center, and its possible etiologic role in the pathophysiology of sudden infant death syndrome are discussed.