Should oxyhaemoglobin saturation be monitored continuously during the 6-minute walk test?

Area of Science:

• Pulmonary Medicine
• Cardiopulmonary Exercise Testing

Background:

• Current guidelines for the 6-minute walk test (6MWT) do not mandate continuous monitoring of oxyhaemoglobin saturation (SpO2).
• The clinical significance of comparing nadir SpO2 with end-6MWT SpO2 in patients with chronic respiratory disease remains unclear.

Purpose of the Study:

• To investigate whether the nadir SpO2 differs from the end-6MWT SpO2 in patients with chronic respiratory disease.
• To determine the proportion of subjects experiencing significant desaturation based on each measurement.
• To evaluate the impact of resting during the 6MWT on the difference between nadir and end SpO2.

Main Methods:

• 86 patients with chronic respiratory disease (29 COPD, 57 ILD) underwent the 6MWT.
• Continuous SpO2 monitoring was performed using a pulse oximeter throughout the test.
• Statistical analysis compared nadir SpO2 and end-6MWT SpO2, and assessed the effect of resting.

Main Results:

• Nadir SpO2 was slightly lower than end-6MWT SpO2 (median 87% vs. 88%, p < 0.001), with individual differences up to 10%.
• Patients who rested during the test (n=14) showed a greater likelihood of a significant difference between nadir and end SpO2 (p=0.04).
• End-6MWT SpO2 failed to accurately identify desaturation in 21% of subjects.

Conclusions:

• While nadir and end SpO2 are generally similar in patients with chronic respiratory disease during the 6MWT, end-test values may not be a reliable indicator of the lowest SpO2.
• Continuous SpO2 monitoring during the 6MWT is recommended, particularly for patients who may rest during the test.
• Clinicians should consider continuous SpO2 monitoring to accurately assess desaturation during the 6MWT.