RT Journal Article
SR Electronic
T1 A simplified method for monitoring respiratory impedance during continuous positive airway pressure
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 185
OP 191
DO 10.1183/09031936.00.15118500
VO 15
IS 1
A1 D Navajas
A1 C Duvivier
A1 R Farre
A1 R Peslin
YR 2000
UL http://erj.ersjournals.com/content/15/1/185.abstract
AB The forced oscillation technique is useful in detecting changes in upper airway obstruction in patients with sleep apnoea undergoing continuous positive airway pressure (CPAP) ventilation. The aim of this study was to implement and evaluate a method for estimating respiratory impedance (Zrs) from the pressure and flow recorded at the inlet of the CPAP tubing. The method is based on correcting impedance measured at the inlet of the CPAP tubing (Zi) for the effect of the tubing and the exhalation port. The method was evaluated in mechanical analogues and in a healthy subject. Sinusoidal oscillation of 5, 10 and 20 Hz were superimposed on CPAP (5-15 cmH2O). At 5 Hz, the changes in airflow obstruction were substantially underestimated by Zi. Furthermore, Zi exhibited a negative dependence on Zrs at 20 Hz. The assessment of Zrs was greatly improved after correcting Zi for the effects of the CPAP tubing and the exhalation port. Zrs was well estimated at low frequencies, reaching very high values during total occlusion (>60 cmH2O x s x L(-1) at 5-10 Hz). These results indicate that changes in airflow obstruction can be detected using the forced oscillation technique from pressure and flow recorded on the continuous positive airway pressure device. This facilitates the clinical application of the forced oscillation technique for monitoring upper airway patency during sleep.