Respiratory Oscillometry and Functional Performance in Different COPD Phenotypes

Abstract

Purpose: Chronic obstructive pulmonary disease (COPD) phenotypes may introduce different characteristics that need to be known to improve treatment. Respiratory oscillometry provides a detailed analysis and may offer insight into the pathophysiology of COPD. In this paper, we used this method to evaluate the differences in respiratory mechanics of COPD phenotypes.

Patients and methods: This study investigated a sample of 83 volunteers, being divided into control group (CG = 20), emphysema (n = 23), CB (n = 20) and asthma-COPD overlap syndrome (ACOS, n = 20). These analyses were performed before and after bronchodilator (BD) use. Functional capacity was evaluated using the Glittre‑ADL test, handgrip strength and respiratory pressures.

Results: Initially it was observed that oscillometry provided a detailed description of the COPD phenotypes, which was consistent with the involved pathophysiology. A correlation between oscillometry and functional capacity was observed (r=-0.541; p = 0.0001), particularly in the emphysema phenotype (r = -0.496, p = 0.031). BD response was different among the studied phenotypes. This resulted in an accurate discrimination of ACOS from CB [area under the receiver operating curve (AUC) = 0.84] and emphysema (AUC = 0.82).

Conclusion: These results offer evidence that oscillatory indices may enhance the comprehension and identification of COPD phenotypes, thereby potentially improving the support provided to these patients.

Keywords: Glittre-ADL test; asthma-COPD overlap; bronchodilator response; chronic bronchitis; emphysema; forced oscillation technique; handgrip analysis; respiratory impedance.

Figure 1

Resistive oscillometric parameters in patients classified according to the studied phenotypes. (A) R4, resistance at 4Hz; (B) R12, resistance at 12Hz; (C) R4-R20, resistance difference between 4 and 20Hz; ACOS, asthma COPD overlapping syndrome; The top and the bottom of the box plot represent the 25th- to 75th-percentile values while the circle represents the mean value, and the bar across the box represents the 50th-percentile value; ns, not significant; *p <0.05; **p <0.01; ***p<0.005; ****p<0.001.

Figure 2

Reactive oscillometric parameters in patients classified according to the studied phenotypes. (A) fr, resonance frequency; (B) Cdyn, dynamic complacency; (C) Ax, area under the reactance curve; (D) Z4, respiratory impedance module; (E) Xm, mean reactance; ACOS, asthma COPD overlapping syndrome; The top and the bottom of the box plot represent the 25th- to 75th-percentile values while the circle represents the mean value, and the bar across the box represents the 50th-percentile value; ns, not significant; *p <0.05; **p <0.01; ****p<0.001.

Figure 3

Predicted and measured handgrip values in the studied COPD phenotypes evaluated in the dominant (A) and non-dominant hands (B). ACOS, asthma COPD overlapping syndrome; The top and the bottom of the box plot represent the 25th- to 75th-percentile values while the circle represents the mean value, and the bar across the box represents the 50th-percentile value; ns, not significant; *p <0.05; **p <0.01; ***p<0.005; ****p<0.001.

Figure 4

Predicted and measured maximum inspiratory pressure (MIP, (A) and maximum expiratory pressure (MEP, (B) values in the studied COPD phenotypes. ACOS, asthma COPD overlapping syndrome; ns, not significant; the top and the bottom of the box plot represent the 25th- to 75th-percentile values while the circle represents the mean value, and the bar across the box represents the 50th-percentile value; * p <0.05; ** p <0.01; **** p<0.001.

Figure 5

Predicted and measured values of Glittre-ADL test in the studied COPD phenotypes. ACOS, asthma COPD overlapping syndrome; the top and the bottom of the box plot represent the 25th- to 75th-percentile values while the circle represents the mean value, and the bar across the box represents the 50th-percentile value; ns, not significant; ***p<0.005; ****p<0.001.

Figure 6

Analysis of receiver operator characteristic (ROC) for the best parameter observed in the discrimination of ACOS from emphysema (A) and chronic bronchitis. (B) AUC, the area under the ROC curve; ^Δvariations of R4-R20 due to the use of bronchodilator; R4-R20, resistance at 4Hz minus at 20Hz.