Clinical relevance of decreased oxygen saturation during 6-min walk test in preoperative physiologic assessment for lung cancer surgery.

OBJECTIVE: The Japanese Association for Chest Surgery (JACS) has released guidelines on preoperative physiologic assessment for lung cancer surgery. However, cardiopulmonary exercise testing (CPET), which is recommended for patients with poor pulmonary function, is available only in limited institutions. We investigated the possibility of 6-min walk test (6MWT) as a substitute of maximum oxygen consumption test (VO(2)max) on preoperative physiologic assessment for lung cancer surgery.
METHODS: The relationship between VO(2)max and 6MWT was retrospectively analyzed in 51 subjects other than lung cancer patients. Following the preliminary analysis, we modified the risk assessment in the JACS guidelines by substituting 6MWT for VO(2)max, and patients who underwent lung cancer surgery were retrospectively assessed using the modified assessment.
RESULTS: Analysis of the correlation between VO(2)max and 6MWT revealed VO(2)max to be significantly correlated to minimum SpO(2) (SpO(2)min) and maximum decrease in SpO(2) (ΔSpO(2)) during 6MWT. Receiver operating characteristic analysis revealed that SpO(2)min and ΔSpO(2) were predictable for a VO(2)max of 15 mL/kg/min, which is the borderline between the average- and increased-risk groups in the JACS guidelines. A total of 1,066 patients were assigned to the average- or increased-risk group according to the modified JACS guidelines using the criteria of SpO(2)min < 91 % and ΔSpO(2) > 4 %. The increased-risk group was significantly inferior to the average-risk group in Home Oxygen Therapy induction rate, cardiopulmonary-related 30- and 90-day mortality (p < 0.001).
CONCLUSIONS: In clinical practice, decreased saturation during 6MWT may be simple and substitutive for CPET in risk assessment for lung cancer surgery using the JACS guidelines.