ABSTRACT
Abstract Background: Arterial compliance reduction has been associated with aging and hypertension in supine position. However, the dynamic effects of orthostatism on aortic distensibility has not been defined. Objective: We sought to determine the orthostatic influence and the interference of age, blood pressure (BP) and heart rate (HR) on the great arteries during gravitational stress. Methods: Ninety-three healthy volunteers (age 42 ± 16 years). Carotid-femoral pulse wave velocity (PWV) assumed as aortic stiffness was assessed in supine position (basal phase), during tilt test (TT) (orthostatic phase) and after return to supine position (recovery phase). Simultaneously with PWV acquisition, measures of BP and HR rate were recorded. Results: PWV during TT increased significantly compared to the basal and recovery phases (11.7 ± 2.5 m/s vs. 10.1 ± 2.3 m/s and 9.5 ± 2.0 m/s). Systolic BP (r = 0.55, r = 0.46 and r = 0.39) and age (r = 0.59, r = 0.63 and r = 0.39) correlated with PWV in all phases. The significance level for all tests was established as α = 0.05. Conclusion: We conclude that there is a permanent increase in PWV during orthostatic position that was returned to basal level at the recovery phase. This dynamic pattern of PWV response, during postural changes, can be explained by an increase in hydrostatic pressure at the level of abdominal aorta which with smaller radius and an increased elastic modulus, propagates the pulse in a faster way. Considering that it could increase central pulse reflection during the orthostatic position, we speculate that this mechanism may play a role in the overall adaptation of humans to gravitational stress.
Resumo Fundamento: A redução da complacência arterial tem sido associada ao envelhecimento e à hipertensão na postura supina. Entretanto, os efeitos dinâmicos do ortostatismo na distensibilidade aórtica não foram definidos. Objetivo: Determinar a influência ortostática e a interferência da idade, pressão arterial (PA) e frequência cardíaca (FC) sobre as grandes artérias durante o estresse gravitacional. Métodos: Noventa e três voluntários saudáveis (idade de 42 ± 16 anos). A velocidade da onda de pulso carotídeo-femoral (VOP), assumida como rigidez aórtica, foi avaliada na posição supina (fase basal) durante o teste de inclinação (TT) (fase ortostática) e após o retorno à posição supina (fase de recuperação). Simultaneamente à aquisição da PWV, registrou-se as medidas de PA e FC. Resultados: A VOP durante o TT aumentou significativamente em comparação com as fases basal e de recuperação (11,7 ± 2,5 m/s vs. 10,1 ± 2,3 m/se 9,5 ± 2,0 m/s). PA sistólica (r = 0,55, r = 0,46 e r = 0,39) e idade (r = 0,59, r = 0,63 e r = 0,39) correlacionaram-se com a VOP em todas as fases. O nível de significância para todos os testes foi estabelecido como = 0,05. Conclusão: Observou-se um aumento permanente da VOP durante a postura ortostática, que retornou ao nível basal na fase de recuperação. Esse padrão dinâmico de resposta da VOP, durante as alterações posturais, pode ser explicado pelo aumento da pressão hidrostática no nível da aorta abdominal que, com raio menor e aumento do módulo de elasticidade, propaga o pulso de maneira mais rápida. Considerando-se que poderia aumentar a reflexão do pulso central durante a posição ortostática, podemos especular que esse mecanismo pode desempenhar um papel na adaptação global do humano ao estresse gravitacional.
Subject(s)
Humans , Male , Female , Adolescent , Adult , Middle Aged , Aged , Young Adult , Arteries/physiology , Baroreflex/physiology , Vascular Stiffness/physiology , Pulse Wave Analysis , Heart Rate/physiology , Hypotension, Orthostatic , Posture , Stress, Physiological , Blood Flow Velocity , Adaptation, Physiological , Cardiovascular Physiological Phenomena , Body Mass Index , GravitationABSTRACT
A 15-year-old female patient presented with orthostatic erythema in the limbs for half a year. Skin examination revealed that diffuse reticular erythema appeared in the limbs after standing with her arms hanging down for 30 seconds, while the erythema disappeared and skin color returned to normal after raising her arms or lying flat for 30 seconds. The rash in the limbs was reproduced by inflating a sphygmomanometer cuff to 60 mmHg for 2 minutes with the limbs in the horizontal position. Antinuclear antibodies were positive at a titer of 1 ∶1 000. Histopathological examination showed dilated small vessels in the superficial dermis without obvious inflammatory cell infiltration. The patient was diagnosed with gravitational erythema.
ABSTRACT
La gravedad fue establecida como el factor determinante de las diferencias en la distribución de la ventilación y la perfusión pulmonares por John West, concepto que continúa exponiéndose hoy en día como principio básico de la fisiología pulmonar. Las imágenes diagnósticas modernas permiten demostrar que la gravedad no es el factor determinante de estas diferencias, hecho que genera grandes interrogantes sobre los conceptos que, entre muchos otros, sustentan la ventilación mecánica, los modos ventilatorios y la ventilación unipulmonar en decúbito lateral durante la cirugía de tórax. El presente artículo reflexiona sobre los recientes hallazgos de los estudios sobre perfusión y ventilación que cuestionan el paradigma de la gravedad como su determinante fundamental, y sobre sus implicaciones clínicas.
Gravity was established as the determinant factor regarding differences in the distribution of ventilation and perfusion in the lung by John West, concept that continue to be exposed, up to day, as a basic principle of the lung physiology. The modern diagnostic images permit to demonstrate that gravity is not the determinant factor of these differences, a fact that generate big questions about concepts, among many others, support mechanical ventila-tions, ventilatory modes and one lung ventilation in lateral position during thoracic surgery. This article reflects on the recent findings of perfusion and ventilation studies that question the paradigm of gravity as its main determinant, and their clinical implications.
Subject(s)
HumansABSTRACT
Colorectal endoscopic submucosal dissection (ESD) still remains a technically difficult procedure. The maintenance of tissue tension and good submucosal exposure during dissection is one of the most important factors for an effective and safe dissection. Although various traction methods have been developed, traction by gravity is one of the most useful method for colorectal ESD. Traction using adjunctive devices can thus be reserved for extremely difficult cases or for endoscopists in their learning periods for colorectal ESD.
Subject(s)
Colorectal Neoplasms , Gravitation , Learning , TractionABSTRACT
Objective The effects of flight factors on dog and rats are observed to acumulate the elementary data and experiences for space biology research and development of life support systems.It will be the first basic step for manned space flight in future.Methods Female dogs,Xiao-Bao and Shan-Shan were on board of two Model T-7A(S2)rockets separately.Duration of flight was about 25 min and height about 70 km.Four physiological parameters:electrocardiogram,blood pressure,breath and skin temperature were recorded.Results Both of two dogs returned safely and healthy.The physiological parameters of Xiao-Bao were successfully recorded on the first rocket.On the second one,partial data of Shan-Shan were interfered by the strong vibration during the separation of rocket body and cone.The obvious changes of heart rate,ECG and blood pressure were recorded for Xio-Bao to be affected by the effects of hyper-gravity and microgravity factors.These changes were normal,temporal and reversible physiological stress responses.Conclusion The dog can tolerate the action of variable factors during the T-7A(S2)flight and no pathological after-effects were observed.