Airway and tissue resistance in wheezy infants: effects of albuterol.
We partitioned total respiratory system resistance into airway (Raw) and tissue (Rti) resistance in 16 sedated infants (age 15 to 88 wk) with a history of wheezing disorders before and after inhalation of albuterol. Using systems identification methods, airway (Raw-z) and tissue resistance (Rti-z) were extracted from measurements of respiratory system transfer impedance (Ztr[omega]) over a wide frequency range (typically, 4 < f < 140 Hz). Baseline Raw-z (80.6 +/- 31.5 cm H(2)O/L/s) was significantly (p < 0.01) reduced after albuterol inhalation (60.6 +/- 22.2 cm H(2)O/L/s) but pre- and postalbuterol Rti-z were not significantly different (2.3 +/- 1.7 and 2.7 +/- 2.4 cm H(2)O/L/s, respectively). Raw-z was compared with airway resistance measured with whole-body plethysmography (Raw-p) in 10 of the 16 infants. Raw-z and Raw-p were significantly different in baseline as well as postalbuterol conditions (86.4 +/- 36.9 versus 19.0 +/- 7.0, and 60.6 +/- 22.0 versus 22.5 +/- 14.7, respectively) and they were not correlated. There was no significant difference between Raw-p under baseline and postalbuterol conditions. We conclude that airway resistance estimated from Ztr measurements comprises the major portion of total resistance (approximately 97%) in infants with wheezing disorders in baseline as well as post-beta agonist inhalation, and it is significantly reduced by albuterol inhalation.
Jackson
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AC
Biomedical Engineering Department, Boston University, Boston, Massachusetts, USA.
Tennhoff
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W
Kraemer
R
R
Frey
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U
D000280:Administration, Inhalation; D000403:Airway Resistance / Q000187:drug effects*; D000420:Albuterol / Q000008:administration & dosage* / Q000009:adverse effects; D001993:Bronchodilator Agents / Q000008:administration & dosage* / Q000009:adverse effects; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D015656:Respiratory Mechanics / Q000187:drug effects*; D012135:Respiratory Sounds / Q000187:drug effects*; D016896:Treatment Outcome
D001993:Bronchodilator Agents; D000420:Albuterol