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The opening interrupter technique for respiratory resistance measurements in children
Monique Oswald-Mammosser1, Anne Charloux, Irina Enache
1Service de Physiologie et d'Explorations Fonctionnelles, Pôle de Pathologie Thoracique, Hôpitaux Universitaires de Strasbourg, Strasbourg, France. monique.oswald@chru-strasbourg.fr
Insights
The opening interrupter resistance (Rint1) and linear back-extrapolation (Rint2) may underestimate airway obstruction in children. Plethysmography (Raw) is a more reliable measure for detecting obstruction and bronchodilator response.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Diagnostic Techniques
Background:
- Interrupter resistance (Rint) is estimated using mouth pressure during occlusion.
- Rint techniques (opening Rint1, linear back-extrapolation Rint2) are compared to plethysmography (Raw) as a gold standard.
- Accurate measurement of airway resistance is crucial for diagnosing and managing pediatric respiratory conditions.
Purpose of the Study:
- To compare the accuracy of Rint1 and Rint2 with Raw in measuring airway resistance in children.
- To evaluate the effectiveness of Rint methods in detecting airway obstruction and bronchodilator response.
- To identify potential limitations of Rint techniques in pediatric populations.
Main Methods:
- The study included 32 asthmatic children and 11 with cystic fibrosis (aged 5-18 years).
- Participants were categorized into non-obstructed (NObs) and obstructed (Obs) groups based on spirometry.
- Three resistance measurements (Rint1, Rint2, Raw) were performed, with some assessed post-bronchodilator (BD).
Main Results:
- Raw was significantly lower than Rint1 and Rint2 (P < 0.001).
- Only Raw showed a significant difference between Obs and NObs groups (P < 0.05).
- Rint1 and Rint2 differences from Raw correlated with FEV1/VC and height, and Rint1-Raw correlated with height.
Conclusions:
- Rint1 and Rint2 may underestimate airway obstruction in children, potentially failing to detect severe cases.
- Rint1 likely includes a tissue component, particularly in younger children.
- While not differing at baseline, Rint1 detected bronchodilation in some obstructed children, suggesting potential utility post-BD.
Background And Objective:
The interrupter resistance (Rint) can be calculated from various estimates of alveolar pressure based on mouth pressure during occlusion. We compared Rint, as measured by the opening interrupter technique (Rint1), and the linear back-extrapolation method (Rint2), with the 'gold standard' airway resistance measured by plethysmography (Raw).
Methods:
The study included 32 asthmatic children and 11 children with cystic fibrosis, aged 5 to 18 years, who were categorized into non-obstructed (NObs) (n = 27) and obstructed (Obs) (n = 16) groups. Spirometry and the three different resistance measurements were performed on all children. Rint1 and Raw were assessed after a bronchodilator (BD) test in 16 and nine children, respectively, in the Obs group.
Results:
Raw (0.48 ± 0.20 kPa.s/L) was lower than Rint1 (1.04 ± 0.34 kPa.s/L) and Rint2 (0.63 ± 0.18 kPa.s/L) (P < 0.001). Raw, but neither Rint1 nor Rint2, was significantly higher in the Obs group than in the NObs group (0.57 ± 0.23 vs 0.42 ± 0.16 kPa.s/L, P < 0.05). The differences Rint1-Raw and Rint2-Raw were correlated with FEV(1) /VC (P < 0.01 and P < 0.001), and Rint1-Raw was correlated with height (P < 0.001). After BD significant changes in Rint1 and Raw were observed in 5/9 and 7/9 children, respectively.
Conclusions:
Rint2, as well as Rint1, may be underestimated in the most Obs children and may therefore fail to detect severe obstruction. Rint1 is likely to include a non-negligible contribution from the tissue component, especially in the youngest children. Although not different between Obs and NObs children at baseline, Rint1 did detect bronchodilation in some Obs children.
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