Tracking of airway and tissue mechanics during TLC maneuvers in mice

• Published in: Journal of applied physiology (1985) Vol. 95; no. 4; pp. 1695 - 1705
• Main Authors: Hantos, Zoltan, Collins, Rachel A, Turner, Debra J, Janosi, Tibor Z, Sly, Peter D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Am Physiological Soc 01.10.2003; American Physiological Society
• Subjects: Airway Resistance; Animals; Biological and medical sciences; Female; Fundamental and applied biological sciences. Psychology; Lung Compliance; Lungs; Mice; Mice, Inbred BALB C; Models, Biological; Physiology - methods; Pulmonary Ventilation; Respiratory system; Rodents; Tissues; Total Lung Capacity; Total lung capacity; volume dependence; Rodentia; Respiratory system; Respiratory tract; Elastance; Tissue; Vertebrata; Mammalia; Mouse; forced oscillations; Forced oscillation; Dependence; tissue elastance; airway resistance
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/japplphysiol.00104.2003

1 Department of Medical Informatics and Engineering, University of Szeged, H-6720 Szeged, Hungary; and 2 Telethon Institute for Child Health Research and Centre for Child Health Research, University of Western Australia, Perth 6008, Australia Submitted 1 February 2003 ; accepted in final form 27 May 2003 A tracking impedance estimation technique was developed to follow the changes in total respiratory impedance (Zrs) during slow total lung capacity maneuvers in six anesthetized and mechanically ventilated BALB/c mice. Zrs was measured with the wave-tube technique and pseudorandom forced oscillations at nine frequencies between 4 and 38 Hz during inflation from a transrespiratory pressure of 0-20 cmH 2 O and subsequent deflation, each lasting for 20 s. Zrs was averaged for 0.125 s and fitted by a model featuring airway resistance (Raw) and inertance, and tissue damping and elastance ( H ). Lower airway conductance (Glaw) was linearly related to volume above functional residual capacity (V) between 0 and 75-95% maximum V, with a mean slope of dGlaw/dV = 13.6 ± 4.6 cmH 2 O -1 · s -1 . The interdependence of Raw and H was characterized by two distinct and closely linear relationships for the low- and high-volume regions, separated at 40% maximum V. Comparison of Raw with the highest-frequency resistance of the total respiratory system revealed a marked volume-dependent contribution of tissue resistance to total respiratory system resistance, resulting in the overestimation of Raw by 19 ± 8 and 163 ± 40% at functional residual capacity and total lung capacity, respectively, whereas the lowest frequency reactance was proportional to H ; these findings indicate that single-frequency resistance values may become inappropriate as surrogates of Raw when tissue impedance is changing. airway resistance; tissue elastance; forced oscillations; volume dependence; total lung capacity Address for reprint requests and other correspondence: Z. Hantos, Dept. of Medical Informatics, Univ. of Szeged, Korányi fasor 9, H-6720 Szeged, Hungary (E-mail: hantos{at}dmi.u-szeged.hu ).