Flow dependence and repeatability of interrupter resistance in lower airways and nose.

The interrupter technique, the simplest method for measuring airflow resistance (R(int)) is particularly valuable under field conditions. We investigate whether during tidal breathing, variations in the flow at which interruption occurs contribute to variability of results. Using a portable device with mouthpiece, sets of 10 measurements of R(int) (R(int,mo)) were made in inspiration and expiration at 0.05 l s(-1) intervals from 0.1 up to 0.9 l s(-1) flow in 22 normal adults, 11 children (5-9 years) and 12 COPD patients. R(int) was also measured via nasal-mask in normal adults (R(int,na)). Intra-subject coefficient of variation was obtained at each flow and flow-dependence of R(int) was assessed. In normal subjects, R(int)-flow relationships were consistent, with a narrow range of absolute values. R(int,na), but not R(int,mo), rose with increasing flow, especially >0.4 l s(-1). Repeatability was poor at flows <0.3 l s(-1) but improved with increasing flow and was better in inspiration than expiration. In children, repeatability was better than in adults and R(int,mo) was not flow dependent at < or =0.4 l s(-1). By contrast, in COPD patients repeatability was less good and R(int,mo) increased with increasing flows. R(int,mo) and R(int,na) should be measured at fixed inspiratory flows. The best signal-to-noise ratios were obtained at 0.4 l s(-1) for R(int) in normal adults and COPD patients and at 0.3 l s(-1) in children.

Comparison of oral and depot intra-muscular steroids in assessing steroid-responsiveness in COPD.

Non-compliance or euphoria may limit the usefulness of prednisolone tablets in assessing steroid-responsiveness in chronic obstructive pulmonary disease (COPD). Depot intra-muscular methyl-prednisolone (imMP), producing a plateau steroid effect over two weeks, may be more reliable. Following two weeks of placebo, twenty-seven COPD patients (mean FEV 1 43% predicted) participated in a two-week randomised, double-blind, placebo-controlled, parallel-design trial taking either 120 mg imMP with placebo tablets or placebo injection with prednisolone 30 mg daily. After each period, post-bronchodilator FEV 1, forced vital capacity (FVC), inspiratory capacity (IC) and six-minute walking distance (6MWD) were assessed and patients completed both quality-of-life scores (St. George's 30 and Short Form 36) and mood scores (Hospital Anxiety and Depression scores and Altman's Self-rating Mania Scale). There were no significant changes in 6MWD, quality of life or mood scores after either type of steroids and no change in lung function after imMP. By contrast, there were small mean improvements in lung function on oral prednisolone (mean FEV 1, FVC and IC increased by 100, 320 and 150 ml, respectively). Only the improvement in FVC was significantly greater after prednisolone compared with imMP. Single depot intra-muscular injections of steroids have no advantage over oral daily prednisolone in testing steroid-responsiveness in COPD patients.