P12 A comparison of lung volumes measured with the MiniBox+ versus conventional plethysmography: a case for thinking outside the box?

Introduction Body plethysmography is the gold standard assessment for lung volumes. However, numerous barriers exist to making a reliable measurement and implementing practically in clinical settings. Alternative approaches to measuring total lung capacity (TLC), thoracic gas volume (TGV) and residual volume (RV) are therefore needed.Research question: Do the MiniBox+-derived lung volume measurements agree with conventional body plethysmography results?Methods Between dates May 2024 and January 2025, 33 consecutive patients and 16 healthy controls had lung volumes assessed using the Platinum Elite™ body plethysmograph (MedGraphics) and Minibox+ (PulmOne) as part of a local service improvement project. Lung volumes measurements were made with both pieces of equipment, in accordance with ARTP standards for acceptability and reproducibility. 1 The order of lung volumes measures with each method was alternated to reduced bias related to training effect. Agreement in TLC, TGV, RV and vital capacity (VC) between the two methods was assessed using Bland-Altman plots. After testing for normality, tests of difference were performed, with statistical significance accepted at a level of p<0.05.Results In MiniBox+ versus Platinum Elite™ body plethysmography, volumes were measured significantly higher for MiniBox+ for TGV [3.3 L (2.57–3.84) vs 2.77 L (2.33–3.21), p<0.0001)], TLC [5.57 L (4.74–6.11) vs 5.26 L (4.5–5.81), p<0.0001] and VC [3.49 L (2.79–3.98) vs 3.29 L (2.6–3.8), p<0.0001). RV was not significantly different between MiniBox+ and Platinum Elite™ body plethysmograph groups [2.04 L (1.59–2.4) vs 1.93 L (1.47–2.16), p=0.106). There were no significant differences in attempts to achieve reproducibility in MiniBox+ versus Platinum Elite™ groups [4 (3–5) vs 5 (4–5), p = 0.176)]. Bland-Altman analysis showed the highest bias for TGV (-0.5251) when compared to TLC (-0.316), RV (-0.109) and VC (-0.1066). See figure 1 for Bland-Altman analysis graphs.Conclusion MiniBox offers an alternative to conventional plethysmography that can be performed with acceptable and reproducible standards. There is a bias in favour of larger TLC and TGV values with the MiniBox versus conventional plethysmography.Abstract P12 Figure 1Reference Sylvester, et al. ARTP statement on pulmonary function testing. BMJ Open Respiratory Research 2020.