PT  - JOURNAL ARTICLE
AU  - Eleanor Herring
AU  - Nigel Clayton
TI  - Effect of sample volume size on single-breath transfer factor for the lung
DP  - 2011 Sep 01
TA  - European Respiratory Journal
PG  - p1221
VI  - 38
IP  - Suppl 55
4099  - http://erj.ersjournals.com/content/38/Suppl_55/p1221.short
4100  - http://erj.ersjournals.com/content/38/Suppl_55/p1221.full
SO  - Eur Respir J2011 Sep 01; 38
AB  - Background: ATS/ERS 2005 guidelines advise a standardised protocol for measuring Transfer factor for the lung (TLCO) via a single breath-hold method. The volume of exhaled gas sampled limits the test in subjects with a vital capacity (VC) under 1.0L. A measure of TLCO in this group would be clinically useful. This study aimed to see how reducing sample volume (Vsamp) influenced TLCO.Methods: We randomly reviewed 125 (87 males, mean age 49-±8.8 years (± sd)) reproducible TLCO tests from our database. Five subgroups (n=25) were included: 1) healthy 2) restrictive lung function, and 3) mild 4) moderate 5) severe obstructive lung disease. For each patient two real-time gas traces were analysed. Washout volume was maintained, whilst the Vsamp was varied to give TLCO readings for Vsamp of 0.2L, 0.4L, 0.6L and 0.8L and 1.0L. The repeatability of TLCO at each Vsamp was investigated with repeatability coefficient. TLCO at each Vsamp was compared to the TLCO at 1.0L Vsamp and the difference illustrated using Bland & Altman plots.Results: Repeatability was not affected by changing Vsamp in any of the subgroups (repeatability coefficient: 0.42-0.64). Mean TLCO increased as little as 3-5% with increasing Vsamp, with the largest difference between a 0.2L and 1.0L Vsamp. However the imprecision of the mean (limits of agreement up to 0.65mmol/min/kPa) indicated a fall in TLCO equal to 15% was possible.Conclusion: In this study changing Vsamp does not compromise repeatability. A clinically significant variation in TLCO of up to 15% is possible with a reduced Vsamp. Further study is needed to confirm this observation and investigate the effect of changing Vsamp on transfer coefficient and alveolar volume.