RESUMO
Orthostatic tachycardia (POTS) can occur after space flights. We determined orthostatic heart rate responses in 18 cosmonauts before and 3-5 days after long-term space missions. Cosmonauts undergoing a cardiovascular training program in space experienced only moderate POTS after their return to earth. Cardiovascular countermeasures may have attenuated POTS. Another possible interpretation is that cardiovascular deconditioning is not sufficient to elicit full blown POTS in the absence of additional genetic or environmental factors.
Assuntos
Exercício Físico/fisiologia , Frequência Cardíaca/fisiologia , Síndrome da Taquicardia Postural Ortostática/fisiopatologia , Voo Espacial , Ausência de Peso/efeitos adversos , Adulto , Descondicionamento Cardiovascular/fisiologia , Humanos , Masculino , Síndrome da Taquicardia Postural Ortostática/prevenção & controleRESUMO
PURPOSE: The environmental conditions in space, particularly exposure to cosmic radiation, coupled with decreased mobility, altered glucose metabolism, and hemodynamic changes may promote cardiovascular disease Therefore, we assessed early vascular aging markers and hemodynamics using a novel oscillometric blood pressure device. METHODOLOGY: In eight cosmonauts (46.5 â± â5.3 âyrs, 77.6 â± â8.2 âkg, 176 â± â6.2 âcm, 7 men/1woman), we determined heart rate, peripheral blood pressure, central blood pressure, and pulse wave velocity in the supine position using an oscillometric brachial device coupled with transfer function analysis. We obtained measurements at baseline (65-90 days before flight) and four days (R+4) and eight days (R+8) after return from six months mission onboard the International Space Station. RESULTS: Compared to baseline, heart rate increased significantly on R+4 (58.6 â± â6.4 vs. 70.3 â± â5.2 bpm) but did not differ on R+8. Central systolic blood pressure increased from 112.5 â± â13.5 on baseline to 125.6 â± â18.5 on R+4 and 121.6 â± â9.5 âmmHg, albeit showing no statistical significance compared to baseline (p â= â0.243/0.295). Peripheral diastolic and systolic as well as central diastolic blood pressure measurements followed this trend. Pulse wave velocity increased non-significantly from baseline (6.7 â± â0.8 âm/s) to R+4 (7.2 â± â0.8 âm/s, p â= â0.499) and stayed elevated on R+8 (7.1 â± â0.5 âm/s, p â= â0.614). CONCLUSION: The important finding of our study is that six months in a near-earth orbit do not lead to clinically significant changes in early vascular ageing biomarkers. However, these findings cannot be extrapolated to the conditions encountered in deep space. Non-invasive testing of vascular biomarkers may have utility in detecting vascular risks during space travel at an early stage.
RESUMO
Impaired autonomic control represents a cardiovascular risk factor during long-term spaceflight. Little has been reported on blood pressure (BP), heart rate (HR), and heart rate variability (HRV) during and after prolonged spaceflight. We tested the hypothesis that cardiovascular control remains stable during prolonged spaceflight. Electrocardiography, photoplethysmography, and respiratory frequency (RF) were assessed in eight male cosmonauts (age 41-50 yr, body-mass index of 22-28 kg/m2) during long-term missions (flight lengths of 162-196 days). Recordings were made 60 and 30 days before the flight, every 4 wk during flight, and on days 3 and 6 postflight during spontaneous and controlled respiration. Orthostatic testing was performed pre- and postflight. RF and BP decreased during spaceflight (P < 0.05). Mean HR and HRV in the low- and high-frequency bands did not change during spaceflight. However, the individual responses were different and correlated with preflight values. Pulse-wave transit time decreased during spaceflight (P < 0.05). HRV reached during controlled respiration (6 breaths/min) decreased in six and increased in one cosmonaut during flight. The most pronounced changes in HR, BP, and HRV occurred after landing. The decreases in BP and RF combined with stable HR and HRV during flight suggest functional adaptation rather than pathological changes. Pulse-wave transit time shortening in our study is surprising and may reflect cardiac output redistribution in space. The decrease in HRV during controlled respiration (6 breaths/min) indicates reduced parasympathetic reserve, which may contribute to postflight disturbances.
Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Pressão Sanguínea , Sistema Cardiovascular/inervação , Frequência Cardíaca , Mecânica Respiratória , Sistema Respiratório/inervação , Voo Espacial , Ausência de Peso/efeitos adversos , Adulto , Eletrocardiografia , Europa (Continente) , Humanos , Hipotensão Ortostática/etiologia , Hipotensão Ortostática/fisiopatologia , Cooperação Internacional , Masculino , Pessoa de Meia-Idade , Fotopletismografia , Postura , Testes de Função Respiratória , Fatores de Tempo , Estados UnidosRESUMO
In the past decade, there has been a resurgence in the field of unobtrusive cardiomechanical assessment, through advancing methods for measuring and interpreting ballistocardiogram (BCG) and seismocardiogram (SCG) signals. Novel instrumentation solutions have enabled BCG and SCG measurement outside of clinical settings, in the home, in the field, and even in microgravity. Customized signal processing algorithms have led to reduced measurement noise, clinically relevant feature extraction, and signal modeling. Finally, human subjects physiology studies have been conducted using these novel instruments and signal processing tools with promising results. This paper reviews the recent advances in these areas of modern BCG and SCG research.