Respiratory mechanics in ventilated COPD patients: forced oscillation versus occlusion techniques

The respiratory mechanics of artificially ventilated chronic obstructive pulmonary disease (COPD) patients were investigated by means of the forced oscillation (FOT) and the end-inspiratory airway occlusion (AOT) techniques. FOT was applied to measure respiratory resistance (Rrs) and reactance (Xrs) from 0.25-16 Hz. Maximum (Rmax) and minimum (Rmin) resistances, static elastance (Est) and time constant (T) were computed by AOT. FOT and AOT data were interpreted with models featuring airway wall shunt, tissue viscoelasticity and parallel inhomogeneity. Rrs* and Xrs*, predicted from the AOT data, were computed and compared with Rrs and Xrs measured by FOT. Rrs and Xrs (hPa x s x L(-1)) decreased from 31.2+/-10.3 to 5.9+/-4.6 and increased from -20.3+/-7.1 to -8.0+/-4.4 from 0.25-16 Hz, respectively. Central resistance (Rc) and peripheral resistance (Rp) (in hPa x s x L(-1)), and shunt elastance (Esh) and tissue elastance (Et) (in hPa x L(-1)) were 4.4+/-5.4, 28.4+/-153, 723+/-393 and 31.8+/-10.1, respectively. Rmin, Rmax and Est were 18.4+/-5.9, 28.4+/-12.8 and 18.1+/-4.2 respectively, and T=0.76+/-0.25 s. The frequency dependence of predicted Rrs* and Xrs* differed markedly from that of measured Rrs and Xrs. The use of different models to interpret the measured data suggests that both airway and tissue properties determined the frequency dependence of respiratory resistance and respiratory reactance in ventilated chronic obstructive pulmonary disease patients at the investigated frequencies (0.25-16 Hz).

This article has been cited by other articles:

				F. Petak, W. Habre, B. Babik, J. Tolnai, and Z. Hantos Crackle-sound recording to monitor airway closure and recruitment in ventilated pigs. Eur. Respir. J., April 1, 2006; 27(4): 808 - 816. [Abstract] [Full Text] [PDF]

				E. Oostveen, D. MacLeod, H. Lorino, R. Farre, Z. Hantos, K. Desager, and F. Marchal The forced oscillation technique in clinical practice: methodology, recommendations and future developments Eur. Respir. J., December 1, 2003; 22(6): 1026 - 1041. [Abstract] [Full Text] [PDF]

				B. Babik, F. Petak, T. Asztalos, Z.I. Deak, G. Bogats, and Z. Hantos Components of respiratory resistance monitored in mechanically ventilated patients Eur. Respir. J., December 1, 2002; 20(6): 1538 - 1544. [Abstract] [Full Text] [PDF]

				R. FARRE, M. MANCINI, M. ROTGER, M. FERRER, J. ROCA, and D. NAVAJAS Oscillatory Resistance Measured during Noninvasive Proportional Assist Ventilation Am. J. Respir. Crit. Care Med., September 1, 2001; 164(5): 790 - 794. [Abstract] [Full Text] [PDF]

				D. W. Kaczka, E. P. Ingenito, S. C. Body, S. E. Duffy, S. J. Mentzer, M. M. DeCamp, and K. R. Lutchen Inspiratory lung impedance in COPD: effects of PEEP and immediate impact of lung volume reduction surgery J Appl Physiol, May 1, 2001; 90(5): 1833 - 1841. [Abstract] [Full Text] [PDF]