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Measurement of ventilatory system resistance in infants and young children
F Marchal1, P Haouzi, C Gallina
1Laboratoire d'Explorations Fonctionnelles Pédiatriques, Hôpital d'Enfants, Vandoeuvre-lès-Nancy, France.
Insights
This study measured infant respiratory mechanics using airway occlusion, finding that respiratory system resistance (Rrs) relates to height and the time constant (tau rs) increases with age.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Infant Lung Function
Background:
- Understanding infant respiratory mechanics is crucial for diagnosing and managing lung diseases.
- Previous studies have used various methods to assess lung function in infants, but data on the ventilatory system's time constant and resistance is still evolving.
Purpose of the Study:
- To investigate the mechanics of the ventilatory system in sleeping infants and young children.
- To determine the relationship between ventilatory system resistance, compliance, and height.
- To analyze the changes in the ventilatory system's time constant during early infancy.
Main Methods:
- Utilized the 'single breath' method involving end-inspiratory airway occlusion during passive expiration.
- Calculated ventilatory system resistance (Rrs) from the ratio of the ventilatory system time constant (tau rs) to compliance.
- Assessed ventilatory system compliance by correlating it with the slope of the quasi-static pressure-volume curve.
Main Results:
- Ventilatory system compliance showed a strong correlation with the quasi-static pressure-volume curve (r = 0.97).
- An allometric relationship was established between respiratory system resistance (Rrs) and height (Ht), aligning with prior research (r = -0.82).
- The ventilatory system time constant (tau rs) demonstrated a significant increase during the first months of life (P < 0.01).
Conclusions:
- The 'single breath' method effectively characterizes infant respiratory mechanics.
- Respiratory system resistance in infants follows an allometric pattern with height.
- Ventilatory system time constant increases significantly in early infancy, indicating developmental changes in lung function.
Abstract:
The mechanics of the ventilatory system were studied in 29 sleeping infants and young children by the analysis of a passive expiration following an end-inspiratory airway occlusion ('single breath' method). The ventilatory system time constant (tau rs) to compliance ratio yielded the value of ventilatory system resistance (Rrs). The calculated ventilatory system compliance correlated well with the slope of the quasi static pressure-volume curve (r = 0.97). The allometric relationship between Rrs and height (Rrs = 81.9.10(3).Ht (cm)-1.76, r = -0.82) is in agreement with forced oscillation measurements during the first year of life (Wohl et al., 1969). tau rs was found to increase significantly over the first months of life (P less than 0.01).