The six-minute walk test (6MWT) is widely used in evaluating diffuse interstitial lung disease (ILD) and pulmonary hypertension (PH). However, their physiological determining factors have not been well defined.
ObjectiveTo evaluate the physiological changes that occur in ILD and PH during the 6MWT, and compare them with the cardiopulmonary exercise test (CPET).
Material and MethodsThirteen patients with ILD and 14 with PH were studied using the 6MWT and CPET on an ergometer cycle. The respiratory variables were recorded by means of telemetry during the 6MWT.
ResultsOxygen consumption (VO2), respiratory and heart rate reached a plateau from minute 3 of the 6MWT in both diseases. The VO2 did not differ from the peak value in the CPET (14±2 and 15±2ml/kg/min, respectively, in ILD; 16±6 and 16±6ml/kg/min, in PH). The arterial oxygen saturation decreased in both diseases, although it was more marked in ILD (−12±5%, P<.01). The ventilatory equivalent for CO2 (VE/VCO2) in PH during the 6MWT was strongly associated with functional class (FC) (85±14 in FC III-IV, 44±6 in FC I-II; P<.001).
ConclusionsThe 6MWT in ILD and PH behaves like a maximal effort test, with similar VO2 to the CPET, demonstrating a limit in oxygen transport capacity. Monitoring using telemetry during the 6MWT may be useful for the clinical evaluation of patients with ILD or PH.
La prueba de marcha de 6 minutos (PM6M) es ampliamente utilizada en la evaluación de la enfermedad pulmonar intersticial difusa (EPID) y en la hipertensión pulmonar (HP). Sin embargo, sus determinantes fisiológicos no han sido bien caracterizados.
ObjetivoEvaluar los cambios fisiológicos que ocurren durante la PM6M en la EPID y en la HP y compararlos con la prueba de esfuerzo cardiopulmonar (PECP).
Material y métodosSe estudiaron 13 pacientes con EPID y 14 con HP mediante PM6M y PECP en cicloergómetro. Durante la PM6M se registraron las variables respiratorias mediante telemetría.
ResultadosEl consumo de oxígeno (VO2), la ventilación y la frecuencia cardiaca mostraron una meseta desde el minuto 3 de la PM6M en ambas patologías. El valor de VO2 no difirió del valor pico en la PECP (14±2 y 15±2ml/kg/min, respectivamente, en la EPID; 16±6 y 16±6 ml/kg/min, en la HP). En ambas patologías, disminuyó la saturación arterial de oxígeno, aunque más marcadamente en la EPID (−12±5%, p<0,01). En la HP, el equivalente ventilatorio de CO2 (VE/VCO2) durante la PM6M estaba fuertemente relacionado con la clase funcional (CF) (85±14 en CF III-IV, 44±6 en CF I-II; p<0,001).
ConclusionesEn la EPID y en la HP la PM6M se comporta como una prueba de esfuerzo máxima, con valores de VO2 similares a la PECP, poniendo de manifiesto limitación de la capacidad de transporte de oxígeno. La monitorización mediante telemetría durante la PM6M puede ser útil para la evaluación clínica de los pacientes con EPID o con HP.
Isabel Blanco is the beneficiary of a grant for training researchers from the Spanish Society of Pneumology and Thoracic Surgery (SEPAR, 2006)
Claudio Villaquirán is the beneficiary of a joint grant for research granted by the SEPAR and the Latin-American Chest Association (ALAT, 2005)
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