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Abstract
Objective: The lung clearance index (LCI), an index of ventilation homogeneity derived from the multiple breath wash out (MBW) of an inert gas, is a lung function test to monitor pulmonary disease. The aim of this study was to investigate whether LCI measurements are suitable for the daily routine in patients with COPD in comparison to young and healthy controls. Methods: MBW measurements were performed successfully in 23 patients (out of 42) patients with COPD (FEV1 %, 40.41 ± 14.65). As controls we selected 30 healthy and young volunteers. All subjects used the EasyOne ProLab™ (ndd, Switzerland). Results: 18 patients were not able to finish measurements successfully because of significant leaks, cough and irregular breathing (GOLD I n=1 (5.6%); GOLD II n=6 (33.3%); GOLD III n=5 (27.7%); GOLD IV n=6 (33.3%). The mean LCI was significantly higher in COPD patients as compared to young and healthy volunteers (12.55 ± 3.50 vs 7.00 ± 1.02, p<0.05). Although LCI correlated with FEV1 %of predicted (r²=-0.540, p<0.01) and Rtot (% pred.) (r²=0.504, p<0.01) the method failed to discriminate between GOLD II-IV classes. LCI correlated with the volume of trapped gas in elderly patients with COPD and young and healthy controls [FRC (% pred.) (r²=0.191, p<0.01), ITGV (% pred.) (r²=0.478, p<0.01), and RV (% pred.) (r²=0.462, p<0.01)]. Moreover, the results did not correlate with the 6-MWT, a validated clinical outcome parameter. Conclusions: Although measurement of LCI was capable to detect inhomogeneous ventilation (airway obstruction and hyperinflation), this method did not discriminate between GOLD II-IV and did not correlate with 6-MWT. More than 43% of the patients with COPD did not complete the study because of difficulties with the method. Nevertheless, the LCI might be a tool to gain insight into lung pathophysiology in younger patients e.g. children. Our preliminary study encourages further investigations for the future.
Highlights
Chronic obstructive pulmonary disease (COPD) is a progressive lung disease caused by chronic smoke inhalation and characterized by persistent airflow obstruction to the lungs that is not fully reversible [1]
Our present study aimed to evaluate the feasibility of multiple breath wash out (MBW) for clinical routine
Several studies describe the use of lung clearance index (LCI) measurements to characterize lung disease, most studies were performed in children as the LCI measurement is non-invasive and does not need active respiratory maneuvers
Summary
Chronic obstructive pulmonary disease (COPD) is a progressive lung disease caused by chronic smoke inhalation and characterized by persistent airflow obstruction to the lungs that is not fully reversible [1]. We asked whether LCI correlates with already well proven clinical outcome parameters for COPD SGRQ, number of exacerbations and 6-MWT. This method has been developed as a noninvasive tool to obtain insight into ventilation homogeneity [8]. The lung clearance index (LCI) is calculated from the washout measurements and represents the multiple of the functional residual capacity (FRC) that is necessary to obtain an end tidal concentration of the tracer gas of 1/40 of the initial concentration (LCI=cumulative expired volume/ FRC) [10]. Studies in infants or children with cystic fibrosis (CF) revealed that MBW and LCI measurements are feasible and able to detect lung disease in an early stage [11,12,13,14,15]. Whereas a recent study showed that LCI is increased in patients with COPD [17], Received April 29, 2016; Accepted June 13, 2016; Published June 17, 2016
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