期刊
ERJ OPEN RESEARCH
卷 7, 期 1, 页码 -出版社
EUROPEAN RESPIRATORY SOC JOURNALS LTD
DOI: 10.1183/23120541.00435-2020
关键词
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资金
- MITACS Accelerate programme
Multiple breath nitrogen washout (MBNW) quantifies ventilation heterogeneity using two distinct protocols: controlled breathing and free breathing. While functional residual capacity (FRC) was comparable between the two protocols, indices of ventilation heterogeneity differed, with poor between-session repeatability for Scond and S-acin derived from free breathing. Differences in S-acin were related to differences in breathing patterns rather than FRC, indicating implications for the clinical implementation of MBNW.
Multiple breath nitrogen washout (MBNW) quantifies ventilation heterogeneity. Two distinct protocols are currently used for MBNW testing: controlled breathing, with targeted tidal volume (V-T) and respiratory rate (RR); and free breathing, with no constraints on breathing pattern. Indices derived from the two protocols (functional residual capacity (FRC), lung clearance index (LCI), S-cond, S-acin) have not been directly compared in adults. We aimed to determine whether MBNW indices are comparable between protocols, to identify factors underlying any between-protocol differences and to determine the between-session variabilities of each protocol. We performed MBNW testing by both protocols in 27 healthy adult volunteers, applying the currently proposed correction for V-T to S-cond and S-acin derived from free breathing. To establish between-session variability, we repeated testing in 15 volunteers within 3 months. While FRC was comparable between controlled versus free breathing (3.17 (0.98) versus 3.18 (0.94) L, p=0.88), indices of ventilation heterogeneity derived from the two protocols were not, with poor correlation for Scond (r=0.18, p=0.36) and significant bias for Sacin (0.057 (0.021) L-1 versus 0.085 (0.038) L-1, p=0.0004). Between-protocol differences in S-acin were related to differences in the breathing pattern, i.e. V-T (p=0.004) and RR (p=0.01), rather than FRC. FRC and LCI showed good between-session repeatability, but S-cond and S-acin from free breathing showed poor repeatability with wide limits of agreement. These findings have implications for the ongoing clinical implementation of MBNW, as they demonstrate that S-cond and S-acin from free breathing, despite V-T correction, are not equivalent to the controlled breathing protocol. The poor between-session repeatability of Scond during free breathing may limit its clinical utility.
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