Effect of bronchodilation (BD) on expiratory flow limitation (EFL) during quiet breathing (QB) assessed by forced oscillation
R. L. Dellaca, A. Aliverti, N. Stevenson, A. Lo Mauro, A. Pedotti, P. M. A. Calverley (Milan, Italy; Liverpool, United Kingdom)
Source: Annual Congress 2002 - Lung mechanics: from laboratory to bedside
Session: Lung mechanics: from laboratory to bedside
Session type: Oral Presentation
Number: 191
Disease area: Airway diseases
Abstract Bronchodilator drugs produce limited improvements in FEV1 but greater changes in end expiratory lung volumes (EELV) in COPD. Assessing this involves patient co-operation and the presence of tidal EFL cannot be determined. We have found that within-breath total respiratory reactance (Xrs) measured by forced oscillation technique during QB is much more negative during expiration than during inspiration only if EFL is present. This approach is reliable compared to Mead and Whittenberger technique, is non-invasive, and does not modify lung volume history or bronchomotor tone. To evaluate the effect of BD on tidal EFL we studied 8 COPD patients during QB before and 45 mins after 5mg nebulised salbutamol. We applied forced oscillations at 5Hz and measured mean inspiratory and expiratory input Xrs and resistance (Xins, Rins, Xexp and Rexp respectively, cmH2O/l*s). BD produced a small increase in FEV1 (table, mean±] SEM) and a greater fall in EELV (-360±]104 ml, p<0.01) as measured by opto-electronic plethysmography. There were significant increases in Xins and Xexp and a reduction of the difference between them and also in Rins. Rexp was not significantly different. Using the Xexp method, EFL disappeared after BD in 3 of 4 patients who showed this initially. This novel approach provides a powerful tool to non-invasively assess lung mechanics in COPD and evaluate the effect of treatment.
FEV1 (%) Xins Xexp Rins Rexp Before BD 54.3±]6.86 -1.92±]0.34 -4.31±]0.81 4.79±]0.84 5.31±]0.98 After BD 62.0±]6.78 -1.14±]0.16 -2.67±]0.47 3.15±]0.32 4.28±]0.51 Changes 8.1 <0.01 0.78 <0.05 1.65 <0.05 -1.64 <0.05 -1.03
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R. L. Dellaca, A. Aliverti, N. Stevenson, A. Lo Mauro, A. Pedotti, P. M. A. Calverley (Milan, Italy; Liverpool, United Kingdom). Effect of bronchodilation (BD) on expiratory flow limitation (EFL) during quiet breathing (QB) assessed by forced oscillation. Eur Respir J 2002; 20: Suppl. 38, 191
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