Contribuição do retorno venoso para o aumento da ventilação pulmonar durante o início do exercício físico
Arquivos
Data
2023
Autores
Campos, Larissa de Freitas 
Orientadores
Silva, Bruno Moreira
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Diversas doenças cardiorrenais evoluem com hiperativação do sistema renina-angiotensina-aldosterona, o que gera múltiplas consequências, incluindo aumento do volume de plasma no sangue. O aumento da volemia pode provocar grande deslocamento de sangue dos membros inferiores para o coração no início do exercício, pelo efeito da bomba muscular. Nesta situação, é possível que o retorno venoso contribua para gerar resposta ventilatória excessiva ao exercício em pacientes com doenças cardiorrenais e, consequentemente, pode estar envolvido na geração da sensação de dispneia. O racional por trás desta hipótese é baseado em experimentos sob condições controladas em modelos animais descerebrados ou anestesiados. Muitos estudos foram feitos em humanos na tentativa de fazer a translação dos achados em modelos animais, no entanto, o papel do aumento do retorno venoso para a regulação da resposta ventilatória ao início do exercício físico em humanos ainda permanece incerto. Portanto, tal lacuna foi alvo de investigação deste trabalho. Nossa hipótese foi que atenuação do retorno venoso reduziria a resposta ventilatória ao início do exercício físico. Para testá-la, 20 adultos jovens e saudáveis realizaram exercício físico em bicicleta ergométrica, contra baixa resistência, com e sem manipulação do retorno venoso por meio de insuflação de manguitos posicionados nas coxas. Mensuramos a ventilação pulmonar por sensores acoplados a uma máscara oronasal, além de múltiplas variáveis cardiovasculares para caracterizar a manipulação do retorno venoso e variáveis perceptuais, como, por exemplo, o relato verbal acerca do nível de vontade para inspirar e de percepção de esforço. A manipulação experimental do nosso protocolo para atenuar o retorno venoso funcionou, visto que o volume sistólico foi menor na condição em que os manguitos foram insuflados. Porém, a resposta ventilatória ao início do exercício foi semelhante entre as condições. Percebemos que a insuflação dos manguitos nas coxas dos participantes provocou aumento na percepção de esforço para realizar o exercício, provavelmente pelos manguitos atrapalharem a execução da pedalada. Sabendo que a percepção de esforço é indicadora do comando motor central e que este gera aumento da ventilação, nós normalizamos a resposta ventilatória ao exercício pelo valor de percepção de esforço reportado pelos voluntários. Após normalizarmos os dados, a análise indicou que a atenuação do retorno venoso gerou menor resposta ventilatória. Portanto, os resultados permitiram sugerir que a resposta ventilatória ao início do exercício depende do aumento do retorno venoso, quando é levada em conta a resposta ventilatória ajustada pelo nível de percepção de esforço observado durante o exercício.
Several cardiorenal diseases evolve with hyperactivation of the renin-angiotensin-aldosterone system, which generates multiple consequences, including increased plasma volume in the blood. Increased blood volume can cause large displacement of blood from the limbs for the heart at the beginning of the exercise, by the effect of the muscular pump. Maybe in this situation, the venous return contributes to generate excessive ventilatory response to exercise in patients with cardio-renal diseases and, consequently, may be involved in the generation of feeling of dyspnea. The rationale behind this hypothesis is based on experiments under controlled conditions in decerebrate or anesthetized animal models. A lot of studies were done in humans in an attempt to translate the findings into animal models. However, so far, the role of increased venous return in response regulation ventilation at the beginning of physical exercise in humans remains uncertain. Therefore, this gap was the subject of investigation of this project. Our hypothesis was that attenuation of venous return would reduce the ventilatory response to the beginning of physical exercise. To test the project hypothesis, young and healthy adults exercised on an ergometric bicycle, against low resistance, with and without manipulation of the venous return through cuff inflation positioned on the thighs. We measured lung ventilation by sensors attached to an oronasal mask, in addition to multiple cardiovascular variables to characterize the manipulation of venous return and perceptual variables, such as, for example, the verbal report about the level of will to inhale and perceived exertion. The experimental manipulation of our protocol to attenuate the venous return worked, as the systolic volume was lower in the condition in which the cuffs were inflated. However, the ventilatory response at the beginning of the exercise was similar between conditions. We noticed that the inflation of the cuffs on the thighs of the participants caused an increase in the perceived exertion to perform the exercise, probably due to the cuffs getting in the way of pedaling. Knowing that the perceived exertion is an indicator of the central motor command and that this generates an increase in ventilation, we normalized the ventilatory response to exercise by the value of perceived exertion reported by the volunteers. After normalizing the data, an analysis indicated that the attenuation of venous return generated a lower ventilatory response. Therefore, the results allow us to suggest that the ventilatory response at the beginning of the exercise depends on the increase in venous return, when the ventilatory response adjusted by the level of perceived exertion observed during exercise is taken into account.
Several cardiorenal diseases evolve with hyperactivation of the renin-angiotensin-aldosterone system, which generates multiple consequences, including increased plasma volume in the blood. Increased blood volume can cause large displacement of blood from the limbs for the heart at the beginning of the exercise, by the effect of the muscular pump. Maybe in this situation, the venous return contributes to generate excessive ventilatory response to exercise in patients with cardio-renal diseases and, consequently, may be involved in the generation of feeling of dyspnea. The rationale behind this hypothesis is based on experiments under controlled conditions in decerebrate or anesthetized animal models. A lot of studies were done in humans in an attempt to translate the findings into animal models. However, so far, the role of increased venous return in response regulation ventilation at the beginning of physical exercise in humans remains uncertain. Therefore, this gap was the subject of investigation of this project. Our hypothesis was that attenuation of venous return would reduce the ventilatory response to the beginning of physical exercise. To test the project hypothesis, young and healthy adults exercised on an ergometric bicycle, against low resistance, with and without manipulation of the venous return through cuff inflation positioned on the thighs. We measured lung ventilation by sensors attached to an oronasal mask, in addition to multiple cardiovascular variables to characterize the manipulation of venous return and perceptual variables, such as, for example, the verbal report about the level of will to inhale and perceived exertion. The experimental manipulation of our protocol to attenuate the venous return worked, as the systolic volume was lower in the condition in which the cuffs were inflated. However, the ventilatory response at the beginning of the exercise was similar between conditions. We noticed that the inflation of the cuffs on the thighs of the participants caused an increase in the perceived exertion to perform the exercise, probably due to the cuffs getting in the way of pedaling. Knowing that the perceived exertion is an indicator of the central motor command and that this generates an increase in ventilation, we normalized the ventilatory response to exercise by the value of perceived exertion reported by the volunteers. After normalizing the data, an analysis indicated that the attenuation of venous return generated a lower ventilatory response. Therefore, the results allow us to suggest that the ventilatory response at the beginning of the exercise depends on the increase in venous return, when the ventilatory response adjusted by the level of perceived exertion observed during exercise is taken into account.