Relación de la saturación de O2 en la prueba de los seis minutos marcha con la masa muscular y la fuerza de contracción del cuádriceps en hombres con EPOC

Abstract

Hypothesis

Among the causes of muscle dysfunction in COPD, mention has been made of decreased oxygen delivery during exercise. Saturation levels during the 6 minutes walking test could be associated to muscle mass and function.

Population, material and methods

A group of 75 males patients, 48 (68.6%) males with COPD in different GOLD stages and 28 (74%) with chronic bronchitis (CB) were studied. Tests performed were spirometry, body mass composition analysis, 6 minutes walking test (6MWT), recording of mean hemoglobin saturation and greater or less than 4%, quadriceps voluntary contraction strength test (QMVC). Work performed (Ww) was determined by the Chuang equation and muscle mass by the Janssen Equation.

Results

No statistical differences were found in age, body mass index (BMI), free fat mass index (FFMI), muscle mass index (MMI) and QMVC, 6MWT and Ww between the COPD and CB groups. Desaturation ≥ 4% was more frequent in the COPD group (p < 0.01) and was related with a limitation in the distance walked (p = 0.025). The mean SpO₂ after 6MWT of ≤ 89% differentiates the COPD from the CB population (p = 0.002). We found no relationship between the different levels of SpO₂ after the walk test and muscle mass parameters (MMI, FFMI).

There was a statistical difference between patients with a mean SpO₂ after the walk test ≤ 90% and the distance reached (p = 0.04). When the mean SpO₂ was ≤ 89%, there was a decrease in the WW (p = 0.032). When the mean SpO2 was ≤ 88% we found a decrease in the QMVC (p = 0.05).

Conclusions

After the 6MWT, SpO₂ is more frequent, this having no relationship with the GOLD stage and is only related with the distance reached. Mean SpO₂ after the 6MWT is more sensitive since it is related to performance parameters in the first place, then with muscle strength, and later with quadriceps contraction strength. We found no relationship between the desaturation parameters studied and the muscle mass measurements.