The measurement of lung volumes using body plethysmography and helium dilution methods in COPD patients: a correlation and diagnosis analysis

Abstract

Chronic obstructive pulmonary disease (COPD) is a chronic airway disease characterized by persistent airflow limitation. Moreover, lung hyperinflation evaluated by lung volumes is also the key pathophysiologic process during COPD progression. Nevertheless, there is still no preferred method to evaluate lung volumes. For this study, we recruited 170 patients with stable COPD to assess lung volumes stratified by airflow limitation severity. Lung volumes including residual volume (RV) and total lung capacity (TLC) were determined by both body plethysmography and helium dilution methods. The discrepancies between these two methods were recorded as ΔRV%pred, ΔTLC%pred, and ΔRV/TLC. We found that ΔRV%pred, ΔTLC%pred, and ΔRV/TLC increased significantly with the severity of COPD. The differences of lung capacity between these two methods were negatively correlated with FEV1%pred, and diffusing capacity for carbon monoxide (DLCO%pred). Moreover, the receiver operating characteristic (ROC) for ΔTLC%pred to distinguish severe COPD from non-severe COPD had an area under curve (AUC) of 0.886. The differences of lung volume parameters measured by body plethysmography and helium dilution methods were associated with airflow limitation and can effectively differentiate COPD severity, which may be a supportive method to assess the lung function of stable COPD patients.

Multiple breath washout testing in adults with pulmonary disease and healthy controls – can fewer measurements eventually be more?

“…Computed tomography may be affected by postural lung volume changes [ 28 ] and incomplete inspiration while Helium dilution may result in underestimation due to gas trapping [ 29 ]. Interestingly, gas trapping independently predicts patients with a larger difference of plethysmography and computed tomography derived total lung capacity [ 30 ] and inter-modal differences even were postulated as a diagnostic tool differentiating COPD severity [ 31 ].…”

Comparing a new device to measure lung volumes with three traditional methods in individuals with different lung conditions

“…Other studies which included restrictive patients and healthy subjects had reported a concordance up to 0.81. 21,27 Among subjects with COPD, we found poor agreement (CCC=0.60) between BP and cabin-less plethysmography, with an underestimation of TLC by cabin-less plethysmography. Despite this, in the lung bullae group, which was challenging because of the presence of unventilated air spaces, agreement between BP and cabin-less plethysmography was better (CCC=0.85), demonstrating a reasonable measurement of intrathoracic gas, but one that is affected by airflow obstruction.…”

“…[28][29][30][31][32] The agreement between BP and DLCO sb was poor in the presence of lung bullae and airflow obstruction (CCC=0.47 and CCC=0.18, respectively), consistent with other studies, finding that gas dilution method by a single breath, only measures correctly well ventilated lung volume. 19,27,[33][34][35][36][37] In a previous study including measurement of lung volumes with different methods 34 , a systematic overestimation of TLC with BP was observed, when All rights reserved. No reuse allowed without permission.…”

Lung Hyperinflation in Chronic Obstructive Pulmonary Disease: Clinical and Therapeutic Relevance

“…Therefore, the diagnosis of static hyperinflation requires the demonstration that FRC, determined by plethysmography, is greater than its upper limit of normal (ULN) 7 . Its evaluation by dilution procedures is not recommended as they underestimate the lung volumes proportionally to the severity of the airflow limitation 8 . Due to the inverse relationship between body mass and FRC in patients with COPD, its evaluation is also not recommended with reference equations that include weight or body surface area 9,10 .…”