RESUMEN
BACKGROUND: Exposure to repeated high +Gz loads and the methods to prevent loss of consciousness cause unique stresses on the cardiovascular system. The purpose of this study was to determine if the +Gz environment is associated with an increased occurrence of valvular regurgitation in pilots of high performance aircraft. METHODS: There were 247 subjects who were divided into pilot (n = 46) and non-pilot (n = 201) groups. Pilots were defined as those individuals who had flown at least 1000 h in high performance aircraft. The echocardiographic data of these subjects were examined retrospectively. RESULTS: We found a statistically significant association between pulmonic insufficiency and exposure to high +Gz stress in pilots vs. non-pilots (chi2 = 13.09, p = 0.0002). In addition, there was a greater incidence of tricuspid regurgitation (chi2 = 4.97, p = 0.025) and concurrent pulmonic insufficiency and tricuspid regurgitation (chi2 = 14.1, p = 0.0002) in the pilot group. CONCLUSIONS: There is a direct relationship between repetitive exposure to a +Gz environment and pulmonic insufficiency, tricuspid regurgitation, or concurrent pulmonic insufficiency and tricuspid regurgitation. This may be secondary to the transient increase in right ventricular pressure due to acceleration forces or straining maneuvers utilized to prevent or postpone +Gz induced loss of consciousness (G-LOC).
Asunto(s)
Medicina Aeroespacial , Hipergravedad/efectos adversos , Enfermedades Profesionales/etiología , Exposición Profesional/efectos adversos , Insuficiencia de la Válvula Pulmonar/etiología , Insuficiencia de la Válvula Tricúspide/etiología , Medidas contra la Ingravidez , Adulto , Femenino , Humanos , Incidencia , Masculino , Enfermedades Profesionales/diagnóstico por imagen , Enfermedades Profesionales/fisiopatología , Prevalencia , Insuficiencia de la Válvula Pulmonar/diagnóstico por imagen , Insuficiencia de la Válvula Pulmonar/fisiopatología , Estudios Retrospectivos , Factores de Riesgo , Índice de Severidad de la Enfermedad , Insuficiencia de la Válvula Tricúspide/diagnóstico por imagen , Insuficiencia de la Válvula Tricúspide/fisiopatología , Ultrasonografía , Inconsciencia/prevención & control , Maniobra de Valsalva , Presión VentricularRESUMEN
An episode of nonsustained ventricular tachycardia was recorded from a crew member during the second month aboard the MIR space station. Although asymptomatic, this cardiac event increases the concern that serious cardiac dysrhythmias may be a limiting factor during long-duration spaceflight.
Asunto(s)
Electrocardiografía Ambulatoria , Vuelo Espacial , Taquicardia Ventricular/etiología , Adulto , Complejos Cardíacos Prematuros/diagnóstico , Complejos Cardíacos Prematuros/etiología , Humanos , Masculino , Taquicardia Supraventricular/diagnóstico , Taquicardia Supraventricular/etiología , Taquicardia Ventricular/diagnósticoRESUMEN
The centrifuge proposed for the Space Station will most likely be used, in part, for countermeasure studies. At present, there is a paucity of information concerning the duration and frequency of acceleration necessary to counteract the atrophy process associated with microgravity. The present study was designed to investigate intermittent acceleration during non-weight bearing of the soleus muscle and its resultant effects on muscular atrophy. Each day rats were removed from hindlimbs suspension and accelerated to 1.2 g for four 15-min periods evenly spaced over a 12-h interval. The soleus muscle experienced non-weight bearing the remaining 23 h each day. This paradigm, when repeated for 7 days, did not completely maintain the mass of soleus muscle, which was 84% of control. Interestingly, the identical protocol utilizing ground support in lieu of acceleration successfully maintained the soleus muscle mass. The failure of the centrifugation protocol to adequately maintain soleus muscle mass might be due to an undefined stress placed on the animals inherent in centrifugation itself. This stress may also explain the transient decline in food intake of the intermittent acceleration group on the 2nd and 3rd days of treatment. Also, these data support the concept that the frequency of exposure, as opposed to the duration of exposure, to weight bearing during hindlimb unweighting seems to be the more important determinant of maintaining postural muscle mass.
Asunto(s)
Atrofia Muscular/prevención & control , Ingravidez/efectos adversos , Aceleración , Animales , Centrifugación , Modelos Animales de Enfermedad , Femenino , Atrofia Muscular/etiología , Atrofia Muscular/patología , Tamaño de los Órganos , Ratas , Ratas Endogámicas , Vuelo EspacialRESUMEN
Mechanical acceleration is a countermeasure that may be employed to prevent atrophy of slow-twitch muscle during non-weight bearing. In the present study, daily centrifugation of rats for different durations (1 or 2 h) and at different gravitational intensities (1.5 or 2.6 G) was used to test whether mechanical acceleration could ameliorate the atrophy of the soleus muscle induced by non-weight bearing (tail-traction model). The soleus muscle atrophied 32% during 7 days of non-weight bearing without countermeasures. Centrifugation treatment did not completely prevent atrophy relative to precontrol wet weight of the soleus muscle. Non-weight-bearing groups receiving 2-h daily treatments of 1, 1.5, or 2.6 G had 48, 56, and 65%, respectively, of the atrophy observed in the non-weight-bearing-only group compared with the precontrol group. No evidence was obtained that centrifugation at 2.6 G was more effective than exposure to 1 or 1.5 G as a countermeasure to non-weight-bearing-induced atrophy of the soleus muscle.