Abstract
BackgroundBronchoscopic lung volume reduction techniques are minor invasive treatment modalities for severely hyperinflated emphysema patients. The severity of static lung hyperinflation determines eligibility and success rate for these treatments. However, it is not exactly known what parameter should be used to optimally reflect hyperinflation. Commonly used parameters are residual volume (RV) and the RV/Total lung capacity (TLC) ratio. Other parameters reflecting hyperinflation are Inspiratory Capacity/TLC and forced vital capacity.ObjectivesTo define which of these function parameters is the most optimal reflection of hyperinflationin in relation to patient-related outcomes.MethodsIn a retrospective cohort study, data from measurements during baseline visits of eight studies were pooled. Primary outcomes were RV/TLC ratio and RV as percentage of predicted (RV%pred), both measured by bodyplethysmography, compared to the patient-related outcome variables: 6-min walk distance (6MWD), the St. George’s Respiratory Questionnaire (SGRQ), and the modified Medical Research Council (mMRC).ResultsTwo hundred seventy-four COPD patients (mean age 59 years; 66% female), FEV1 0.74 ± 0.28 L, RV 4.94 ± 1.06 L, 6MWD of 339 ± 95 m, were included in the analysis. Significant correlations (all p < 0.01) were found between RV%pred and 6MWD (r = − 0.358), SGRQ (r = 0.184), and mMRC (r = 0.228). Also, there was a significant correlation between RV/TLC ratio and 6MWD (r = − 0.563), SGRQ (r = 0.289) and mMRC (r = 0.354). Linear regression analyses showed that RV/TLC ratio was a better predictor of patient outcomes than RV%pred.ConclusionThis study demonstrates that both RV/TLC ratio and RV%pred are relevant indicators of hyperinflation in patients with severe emphysema in relation to patient-related outcomes. RV/TLC ratio is more strongly related to the patient-related outcomes than RV%pred.
Highlights
Chronic obstructive pulmonary disease (COPD) is a progressive and incurable disease
The results of this study show that residual volume (RV)/Total lung capacity (TLC) ratio and RV as percentage of predicted (RV%pred) both provide relevant information about the impact of hyperinflation on the patients quality of life and exercise tolerance, with RV to total lung capacity (RV/TLC) ratio being the best predictor of the variation in outcomes
The correlation of RV/TLC to patient-related outcomes is stronger than the correlation between RV%pred and patient-related outcomes
Summary
Chronic obstructive pulmonary disease (COPD) is a progressive and incurable disease This is initially reflected by a reduced forced expiratory volume in 1 s (FEV1) as well as a reduced F EV1/forced vital capacity (FVC) ratio [1, 2]. Over time, this will lead to a further decrease in expiratory flow and increase in lung static hyperinflation [3]. The severity of static lung hyperinflation determines eligibility and success rate for these treatments It is not exactly known what parameter should be used to optimally reflect hyperinflation. RV/TLC ratio is more strongly related to the patient-related outcomes than RV%pred
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