Volume dependence of respiratory impedance in infants

Petak, F., Hayden, M.J., Hantos, Z. and Sly, P.D. (1997) Volume dependence of respiratory impedance in infants. American Journal of Respiratory and Critical Care Medicine, 156 4: 1172-1177.

Author Petak, F.
Hayden, M.J.
Hantos, Z.
Sly, P.D.
Title Volume dependence of respiratory impedance in infants
Journal name American Journal of Respiratory and Critical Care Medicine   Check publisher's open access policy
ISSN 1073-449X
Publication date 1997-10
Sub-type Article (original research)
Volume 156
Issue 4
Start page 1172
End page 1177
Total pages 6
Place of publication New York, NY, United States
Publisher American Thoracic Society
Language eng
Formatted abstract
We previously studied low-frequency respiratory impedance (Zrs) data at an elevated lung volume to separate airway and tissue mechanical properties in normal infants (Am.). Respir. Crit. Care Med. 1996; 154:161-166). The aim of the present study was to determine the volume dependence of the airway and tissue mechanics by extending Zrs measurements to lower lung volumes. Zrs spectra between 0.5 and 21 Hz were measured in supine sleeping infants (n = 8; 7 to 26 mo of age) at mean transrespiratory pressures (Ptrmean) of 20, 10, and 0 cm H2O, during periods of apnea induced by inflating the infants' lungs to a pressure of 20 cm H2O through a face mask. At each inflation pressure, a model containing airway resistance (Raw) and inertance (law) and tissue damping (G) and elastance (H) was fitted to Zrs data. At FRC, the values of Raw, law, G, and H were 20.6 ± 4.9 (SD) cm H2O · s/L, 0.037 ± 0.014 cm H2O · s2/L, 39.6 ± 10.3 cm H2O/L, and 147 ± 35 cm H2O/L, respectively. Increase of Ptrmean caused a monotonous decrease in Raw (42 ± 7% of the value at FRC), while law remained constant. The tissue parameters were minimal at a Ptrmean of 10 cm H2O (68 ± 10% and 78 ± 6% in G and H, respectively) and significantly higher at both 0 and 20 cm H2O. Although Zrs measurements can be made in most infants at lung volumes as low as FRC, an inflation pressure of 20 cm H2O pro-vides a higher success rate and is therefore a more suitable condition for general use.
Keyword End expiratory pressure
Lung tissue mechanics
Chest wall
Pulmonary impedance
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Medicine Publications
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Created: Wed, 17 Nov 2010, 11:41:49 EST