Assessment of reversibility of airflow obstruction.

Abstract

The application of the forced oscillation technique to assess reversibility of airflow obstruction was compared with that of indices of forced expiration and plethysmographic airway resistance (Raw). In 125 patients with airflow obstruction, we measured total respiratory resistance (Rrs) and reactance (Xrs), Raw and specific airway conductance (sGaw), maximal flow-volume curves and forced expiratory volume in 1 s (FEV1), before and 30 min after 2 x 20 micrograms salbutamol by MDI. Salbutamol induced significant change in mean value of all measured indices. The changes in impedance data consisted of decrease in mean value and of negative frequency dependence of Rrs, an increase in Xrs with slight decrease of its positive frequency dependence. Multivariate analysis of differences between pre- and postbronchodilator values showed that the single indices with the greatest sensitivity to detect the effect of salbutamol were, in decreasing order, (1) in relative change (% baseline value): Raw, Rrs at 6 Hz (Rrs6), forced vital capacity (FVC), FEV1, and (2) in absolute change: FVC, sGaw or Raw, Rrs6, FEV1, maximal expiratory flow (MEF50). The effect of salbutamol was described best in (1) by a combination of Raw and FVC and in (2) by sGaw and FVC. For individual detection of bronchodilator effect, threshold values were calculated from mean reproducibility of the three baseline values of the various indices, attempting to estimate whether response to a bronchodilator is statistically significant. The greatest number of significant responses were observed for Raw, sGaw, FEV1, and FVC in that succession, Rrs6 being markedly less sensitive. This discrepancy is due to the lack of Rrs6 response to bronchodilators in patients with severe airway obstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of lung function methods for assessing dose–response effects of salbutamol

“…Previous studies assessing bronchodilatation have shown that the greatest percentage change is observed using sGaw, leading to the conclusion that this is the most sensitive method [13][14][15][16]. However, these studies have limitations.…”

“…First, variability has not always been taken into consideration when assessing the physiological changes caused by a drug [14,15]. Second, the majority of the studies have only used one drug dose (usually a standard clinical dose) [13][14][15]. Consequently, the utility of spirometry, plethysmography and IOS to detect small changes while taking into account method variation, which is critical when assessing the full dose-response curve, is not known.…”

Superiority of "triple" therapy with salmeterol/fluticasone propionate and tiotropium bromide versus individual components in moderate to severe COPD

“…We used the sensitive pulmonary function measurement of specific airway conductance as the primary end point to compare the different treatment regimens. [18][19][20][21] Pulmonary function measurements of spirometry and lung volumes were also performed, and symptom scores were evaluated.…”

Cholinergic bronchomotor tone and airway caliber in tetraplegic patients

“…11 Additionally, during plethysmography 'responders' achieved an improvement in sGaw equal to or greater than 40%. 17 Those with less than these thresholds were classified as 'nonresponders'.…”

“…Secondarily, we hoped to clarify the effect of baclofen on the airway tone of these subjects. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33], studied during the same time period. All participants were screened for a history of pulmonary disease or respiratory symptoms, recent respiratory viral or bacterial infection, and asthma or seasonal allergy.…”