Premium
Machinal properties of the upper airway wall in children and their influence on respiratory impedance measurements
Author(s) -
Marchal F.,
Hauouzi P.,
Peslin R.,
Duvivier C.,
Gallina C.
Publication year - 1992
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.1950130108
Subject(s) - medicine , respiratory system , airway , anesthesia
The upper airway wall impedance (Zuaw) may be responsible for a large artifact in the measurement of respiratory system impedance (Zrs) in children. In 17 normal children aged 3.5‐13 years Zuaw and Zrs were estimated by varying transrespiratory pressure directly at the mouth (conventional method:Z1) and around the subject's head (head generator method: Z2) from 4 to 32Hz. Zrs and Zuaw were calculated from Z1 = Zrs · Zuaw/(zrs + Zuaw) and Z2 = Zrs (1 =Zp/Zuaw), where Zp is the impedance of the pneumotachograph. From the real and imaginary part of Z1, Z2, Zrs, and Zuaw, the corresponding resistance, inertance, compliance and resonant frequency were calculated assuming simple REC models. No significant difference was found between the mean ± SE of parameters derived from Zrs (respectively, 6.8 ± 0.4 cmH 2 O·L −1 ·s, o.034 ± 0.001 cmH 2 O·L −1 · s 2 , 10.4 ± 0.8 m. cmH 2 O·L −1 , 9.1 ± 0.3Hz) and Z2 (6.8 ± 0.4 cmH 2 O·L −1 · s, 0.038 ± 0.002 cmH 2 O·L −1 · s 2 , 10.7 ± 0.7 ml. cmH 2 O−1, 8.7 ± 0.4 Hz). All but the compliance, derived from Z1 were significantly different ( p <0.01) from those derived from Zrs (5.3 ± 0.3 cmH 2 O·L −1 · s, 0.008 ± 0.001 cmH 2 O·L −1 · s 2 , 11.9 ± 1.2 ml. cmH 2 O−1, and 20.3 ± 1.6 Hz). Respiratory resistance and compliance correlated significantly with height (r= −0.56 and 0.86, respectively), in contrast to upper airway wall resistance (Ruaw) and compliance (Cuaw). Ruaw (8.6 ± 0.8 cmH 2 O·L −1 ·s), Cuaw (1.2 ± 0.2 m· cmH 2 O−1), and upper airway wall inertance (0.030 ± 0.004 cmH 2 O·L −1 · s 2 ) were close to those obtained by direct measurements in adults. The mechanical properties of the upper airway wall are responsible for a significant error in the measurement of Zrs by the conventional method in normal children. Most of the artifact may be corrected for by applying pressure around the child's head. © 1992 Wiley‐Liss, Inc.