Validation of a New Modified 6-Minute Walk Test (6MWT)

Background: Patients suffering from congenital heart disease often may not follow classical standardized cardiopulmonary exercise test (CPET) on a treadmill or bicycle due to insufficiency or mental or physical disability.

Method: We developed a new CPET for these patients based on a 6MWT allowing individual speed combined with a mobile telemetric spiroergometry. In addition to 6MWT distance and Borg dyspnea index, oxygen uptake (VO₂/kg), CO₂ production as well as heart rate (HR), breathing frequency (BF) and -minute volume (VE), pulse oxymetry, and ECG could be recorded.

Results: In a pilot study, we strained 26 healthy volunteers both by regular treadmill CPET (DGPK protocol) and our modified 6MWT in random order on 2 subsequent days. The setup was validated by 28 patients recruited from our GUCH outpatient clinic.

	No.	Gender	Age [years]	Height [cm]	Weight [kg]
Volunteers	26	12 males, 14 females	24.3 ± 4.4	175 ± 8	70.69 ± 12.1
Patients	28	14 males, 14 females	23.1 ± 7.4	171 ± 12	66.5 ± 16.4

Biometrical data: (mean ± SD). Statistically there were no biometrical differences.

Test data: (mean ± SD). AT = anaerobic threshold, max = maximum.

	VO2/kg/minAT [mL/kg/min]	VO2/kg/min-max [mL/kg/min]	O2/HR-AT [mL]	OUES	HR-AT [/min]	BFAT [/min]	VEAT [L/min]
Treadmill	24.4 ± 7.2	41.2 ± 11.1	12.1 ± 3.8	2.89 ± 0.96	137.2 ± 22.0	25.3 ± 6.7	40.5 ± 15.1
6MWT	23.2 ± 6.9	32.1 ± 10.3	11.3 ± 3.7	2.94 ± 1.17	141.9 ± 24.6	32.0 ± 9.3	44.8 ± 16.1
r	0.67	0.74	0.74	0.81	0.52	0.53	0.54

In linear regression analysis, best correlation was found for oxygen uptake efficiency slope (OUES), oxygen uptake (VO₂/kg/min) at anaerobic threshold and maximum.

Conclusion: Although our modified 6MWT is a test at submaximal effort at anaerobic threshold, it correlates well to classical treadmill test enabling CPET even in physically or mentally handicapped patients, and may serve as substitute for 'classical' treadmill test.

Publication History

Article published online:
28 January 2023