Beschreibung:
<jats:title>Abstract</jats:title><jats:p>In 16 healthy and 16 asymptomatic asthmatic children (age range 5–8 yr; 8 girls, 24 boys) we studied the influence of breathing frequency on the results and the diagnostic value of body plethysmographic measurements. Airway resistance (R<jats:sub>aw</jats:sub>), specific airway resistance (SR<jats:sub>aw</jats:sub>), and thoracic gas volume (TGV) were measured during breathing (or breathing efforts against a closed shutter) at 0.4, 1, and 2 Hz. SR<jats:sub>aw</jats:sub> was computed by a simplified procedure directly from flow at the mouth vs. box volume‐curves. The diagnostic value of each parameter was assessed as the percentage of correctly classified healthy and asthmatic subjects by means of discriminant analysis. When frequency was increased from 0.4 to 1 and 2 Hz mean TGV rose by 5 and 14% in healthy children and by 11 and 21% in asthmatic children, respectively. From 0.4 to 1 Hz mean R<jats:sub>aw</jats:sub> decreased by 16% (<jats:italic>P</jats:italic> = 0.002) in healthy children and by 25% (<jats:italic>P</jats:italic> = 0.0004) in asthmatic children. The differences in R<jats:sub>aw</jats:sub> between both groups decreased with frequency (3.5, 1.8, and 1.5 cm H<jats:sub>2</jats:sub>O·L<jats:sup>−1</jats:sup>·s at 0.4, 1, and 2 Hz, respectively) and those of TGV increased (0.13, 0.21, and 0.23 L). SR<jats:sub>aw</jats:sub> showed similar frequency characteristics as R<jats:sub>aw</jats:sub>. As intra‐group variability changed in parallel with the differences the diagnostic value of the parameters remained constant with frequency. Simplified SR<jats:sub>aw</jats:sub> alone and TGV combined with R<jats:sub>aw</jats:sub> exhibited no differences in their diagnostic values (81–84% correctly classified). Our results indicate that in young healthy and asthmatic children the diagnostic value of TGV, Raw, and SRaw is not influenced by breathing frequencies (0.4–2 Hz) and that in these children the simplified computation of SR<jats:sub>aw</jats:sub> can be used without loss of information. Pediatr Pulmonol 1990; 8:23‐28.</jats:p>