Associations between 6-min walk distance and cardiopulmonary parameter in non-obese older adults: An observational study

Background

The 6-min walk test (6MWT) has established itself as a classical field-test for assessing exercise capacity across diverse populations, including older adults. Despite its widespread use, the specific contribution of cardiopulmonary factors to the 6-min walk distance (6MWD) remains relatively unexplored.

Objective

The primary objective of this investigation was to examine any potential associations between 6MWD and various cardiopulmonary parameters in older adults.

Methods

Ninety-two non-obese older adults (66.9 ± 4.1 years) were recruited for this study. Real-time assessments of cardiohemodynamic parameters were conducted using impedance cardiography, while cardiopulmonary parameters were evaluated using a gas analyzer during the administration of the 6MWT.

Results

Our findings revealed mild-to-strong positive correlations between 6MWD and several cardiohemodynamic parameters, including left cardiac work index, heart rate, cardiac output, and cardiac index, as well as cardiopulmonary parameters such as oxygen consumption ($\dot{\dot{V}}{O}_2$), carbon dioxide consumption ($\dot{\dot{V}}{\text{CO}}_2$), minute ventilation, oxygen pulse, tidal volume, respiratory exchange ratio (RER), and breath frequency at the end of walking task (p < 0.05). Additionally, a negative moderate association was observed between 6MWD and systemic vascular resistance index (SVRi), while no significant correlation was found between stroke volume and 6MWD. Furthermore, a combination of SVRi, $\dot{\dot{V}}{O}_2$, $\dot{\dot{V}}{\text{CO}}_2$, and RER appeared to predict 6MWD with reasonable accuracy (R² = 0.567, p < 0.001).

Conclusions

Our investigation highlights a robust association between cardiopulmonary parameters and 6MWD among non-obese older adults. These results also emphasize the potential impact of systemic vascular health on submaximal exercise capacity evaluation within the community-dwelling older adults.