Airway dynamics in COPD patients by within-breath impedance tracking: effects of continuous positive airway pressure

[摘要] Tracking of the within-breath changes of respiratory mechanics using the forced oscillation technique may provide outcomes that characterise the dynamic behaviour of the airways during normal breathing.We measured respiratory resistance (Rrs) and reactance (Xrs) at 8xe2x80x85Hz in 55 chronic obstructive pulmonary disease (COPD) patients and 20 healthy controls; and evaluated Rrs and Xrs as functions of gas flow (Vxe2x80xb2) and volume (V) during normal breathing cycles. In 12 COPD patients; additional measurements were made at continuous positive airway pressure (CPAP) levels of 4; 8; 14 and 20xe2x80x85hPa.The Rrs and Xrs versus Vxe2x80xb2 and V relationships displayed a variety of loop patterns; allowing characterisation of physiological and pathological processes. The main outcomes emerging from the within-breath analysis were the Xrs versus V loop area (AXV) quantifying expiratory flow limitation; and the tidal change in Xrs during inspiration (xcex94XI) reflecting alteration in lung inhomogeneity in COPD. With increasing CPAP; AXV and xcex94XI approached the normal ranges; although with a large variability between individuals; whereas mean Rrs remained unchanged.Within-breath tracking of Rrs and Xrs allows an improved assessment of expiratory flow limitation and functional inhomogeneity in COPD; thereby it may help identify the physiological phenotypes of COPD and determine the optimal level of respiratory support.

[学科分类] 呼吸医学