Original Paper Respiration 1992;59:81-88
Department of Pulmonary Diseases, University Hospital, Maastricht, The Netherlands
Analysis of Respiratory Impedance Characteristics in Chronic Bronchitis
Key Words
Abstract
Impedance Resistance Reactance Chronic bronchitis Reversibility
Impedance measurements of the respiratory system were performed by means of the technique of forced oscillations to study the mechanical characteristics of the respiratory system in 33 patients with chronic bronchitis without spiromctric evidence of airway obstruction (FEV, ^70% predicted). In 23 patients (69.7%) impedance was found to be abnormal. Inhalation of a (T-adrencrgic drug (tcrbutaline) resulted in acute reversibility of these findings. In the 10 pa tients (30.3%) with a normal baseline respiratory impedance, isocapnic hyper ventilation with cold air resulted in impedance characteristics similar to the ab normalities spontaneously occurring in the other group. These changes were found to be completely reversible after the inhalation of terbutaline. On the basis of these findings we conclude that impedance measurements of the respi ratory system by means of the technique of forced oscillations allow the deter mination of mechanical airway abnormalities in patients with chronic bronchi tis.
Introduction
Chronic bronchitis is a commonly encountered disease entity in clinical practice. Chronic bronchitis is usually de fined in clinical terms according to the criteria provided by the American Thoracic Society1. The condition occurs predominantly in cigarette smokers but may be found in non-smokers as well. Airflow obstruction is thought by some to be a complication in chronic bronchitis. Fletcher and Peto [2] reported that clinically significant airflow ob struction docs not develop in most non-smokers and many smokers, but Campbell et al. [3] have reported that the rate of decline of the FEV, was greater in patients with chronic bronchitis than in normal subjects. From a study on the long-term prognosis of patients with severe or less severe chronic airflow obstruction. Postma and Sluiter [4]
Received: February 11. 1991 Accepted: December Ift. 1991
concluded that smoking cessation and an early therapy di rected at the reversible part of airflow obstruction may be able to prevent deterioration. A number of authors have reported on lung function findings in patients with chronic bronchitis and in asymptomatic cigarette smokers with normal FEV,. Woolcock ct al. [51 demonstrated frequency dependence of compliance in subjects with biopsy evi dence of small airway disease and with normal airway re sistance and maximal expiratory flow rate. Ingram and O’Cain [6] demonstrated small airway changes reflected by frequency dependence of compliance even in appar ently healthy cigarette smokers. Frequency-dependent behaviour of the respiratory sys tem can also be analysed by means of the technique of forced oscillations. This technique, introduced by Dubois et al. [7], enables the characterization of the mechanical
G J. Wesseling Department of Pulmonary Diseases University Hospital. PO Box 1918 NL-6201 BX Maastricht (The Netherlands)
© I992S. Karger AG. Basel 0025-793 l.‘92/0592- f„ FD
F/M years ni kg litres % k P a T '-s kpa•11•s kPal's Hz kPa T ' s
7/3 46.9 1.66 66.8 2.98 97.1 0.314 -0.022 0.347 9.92 0.0016
Group B (n = 23) SD
mean
SD
0.83 12.2 0.071 0.029 0.073 2.01 0.0019
7/16 53.3 1.67 81.3 2.70 90.4 0.370 -0.086 0.319 17.13 -0.0026
0.51 18.7 0.094 0.057 0.075 4.10 0.0024
p values A vs. B
n.s. * *** *** *** ***
Group A (n = 10), patients with normal baseline impedance values and group B (n = 23). patients with abnormal baseline impedance values. Levels of significance: n.s. = not significant, * p ¿0.05, ***0.001 < p ^ 0 .0 1 .
Results
All 33 patients completed the study. Anthropometric and baseline spirometric and impedance data are summa rized in table 1. Six patients of group A and 11 patients of group B were current smokers. Ten patients (group A) had normal baseline impedance values. Twenty-three (7 female) had either a resonant frequency ^ 16 Hz or fre quency dependence of resistance < 0 or both and were considered abnormal (group B). Differences in all imped ance parameters were highly significant between the two groups (table 1). In table 2 the results of the correlation analysis between FEV, and the various impedance parameters arc summa rized. Correlation coefficients between FEV, and FEV, as a percentage of predicted and R ^ ,, Rrs(78), Xrs(8), f,, and FD ranged from 0.026 to 0.374 and did not reach a level of significance. Impedance data of the 10 patients in group A before and after cold air provocation and subsequent in halation of terbutaline are presented in figure 1. After cold air challenge, R rs(8) increased significantly (p
Department of Pulmonary Diseases, University Hospital, Maastricht, The Netherlands
Analysis of Respiratory Impedance Characteristics in Chronic Bronchitis
Key Words
Abstract
Impedance Resistance Reactance Chronic bronchitis Reversibility
Impedance measurements of the respiratory system were performed by means of the technique of forced oscillations to study the mechanical characteristics of the respiratory system in 33 patients with chronic bronchitis without spiromctric evidence of airway obstruction (FEV, ^70% predicted). In 23 patients (69.7%) impedance was found to be abnormal. Inhalation of a (T-adrencrgic drug (tcrbutaline) resulted in acute reversibility of these findings. In the 10 pa tients (30.3%) with a normal baseline respiratory impedance, isocapnic hyper ventilation with cold air resulted in impedance characteristics similar to the ab normalities spontaneously occurring in the other group. These changes were found to be completely reversible after the inhalation of terbutaline. On the basis of these findings we conclude that impedance measurements of the respi ratory system by means of the technique of forced oscillations allow the deter mination of mechanical airway abnormalities in patients with chronic bronchi tis.
Introduction
Chronic bronchitis is a commonly encountered disease entity in clinical practice. Chronic bronchitis is usually de fined in clinical terms according to the criteria provided by the American Thoracic Society1. The condition occurs predominantly in cigarette smokers but may be found in non-smokers as well. Airflow obstruction is thought by some to be a complication in chronic bronchitis. Fletcher and Peto [2] reported that clinically significant airflow ob struction docs not develop in most non-smokers and many smokers, but Campbell et al. [3] have reported that the rate of decline of the FEV, was greater in patients with chronic bronchitis than in normal subjects. From a study on the long-term prognosis of patients with severe or less severe chronic airflow obstruction. Postma and Sluiter [4]
Received: February 11. 1991 Accepted: December Ift. 1991
concluded that smoking cessation and an early therapy di rected at the reversible part of airflow obstruction may be able to prevent deterioration. A number of authors have reported on lung function findings in patients with chronic bronchitis and in asymptomatic cigarette smokers with normal FEV,. Woolcock ct al. [51 demonstrated frequency dependence of compliance in subjects with biopsy evi dence of small airway disease and with normal airway re sistance and maximal expiratory flow rate. Ingram and O’Cain [6] demonstrated small airway changes reflected by frequency dependence of compliance even in appar ently healthy cigarette smokers. Frequency-dependent behaviour of the respiratory sys tem can also be analysed by means of the technique of forced oscillations. This technique, introduced by Dubois et al. [7], enables the characterization of the mechanical
G J. Wesseling Department of Pulmonary Diseases University Hospital. PO Box 1918 NL-6201 BX Maastricht (The Netherlands)
© I992S. Karger AG. Basel 0025-793 l.‘92/0592- f„ FD
F/M years ni kg litres % k P a T '-s kpa•11•s kPal's Hz kPa T ' s
7/3 46.9 1.66 66.8 2.98 97.1 0.314 -0.022 0.347 9.92 0.0016
Group B (n = 23) SD
mean
SD
0.83 12.2 0.071 0.029 0.073 2.01 0.0019
7/16 53.3 1.67 81.3 2.70 90.4 0.370 -0.086 0.319 17.13 -0.0026
0.51 18.7 0.094 0.057 0.075 4.10 0.0024
p values A vs. B
n.s. * *** *** *** ***
Group A (n = 10), patients with normal baseline impedance values and group B (n = 23). patients with abnormal baseline impedance values. Levels of significance: n.s. = not significant, * p ¿0.05, ***0.001 < p ^ 0 .0 1 .
Results
All 33 patients completed the study. Anthropometric and baseline spirometric and impedance data are summa rized in table 1. Six patients of group A and 11 patients of group B were current smokers. Ten patients (group A) had normal baseline impedance values. Twenty-three (7 female) had either a resonant frequency ^ 16 Hz or fre quency dependence of resistance < 0 or both and were considered abnormal (group B). Differences in all imped ance parameters were highly significant between the two groups (table 1). In table 2 the results of the correlation analysis between FEV, and the various impedance parameters arc summa rized. Correlation coefficients between FEV, and FEV, as a percentage of predicted and R ^ ,, Rrs(78), Xrs(8), f,, and FD ranged from 0.026 to 0.374 and did not reach a level of significance. Impedance data of the 10 patients in group A before and after cold air provocation and subsequent in halation of terbutaline are presented in figure 1. After cold air challenge, R rs(8) increased significantly (p
