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Peak inspiratory flows in children with cystic fibrosis
L M Gauld1, K Briggs, P Robinson
1Department of Respiratory Medicine, Royal Children's Hospital, Flemington Road, Parkville, Victoria, Australia. gauldl@cryptic.rch.unimelb.edu.au
Insights
In children with cystic fibrosis lung disease, peak inspiratory flow is generally adequate for dry powder inhalers. However, reduced forced vital capacity may indicate lower peak inspiratory flow, suggesting metered dose inhalers may be more suitable.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Cystic Fibrosis Research
Background:
- Cystic fibrosis (CF) significantly impacts lung function, potentially affecting inspiratory flow rates.
- Accurate assessment of inspiratory flow is crucial for effective medication delivery via inhalers in children with CF.
Purpose of the Study:
- To evaluate if inspiratory flow is reduced in children with moderately severe cystic fibrosis lung disease.
- To determine if peak inspiratory flow can be predicted using parameters like height, expiratory flow, or body mass index.
Main Methods:
- Prospective enrollment of children aged >5 years with CF and forced expiratory volume in 1 second <60% predicted.
- Measurement of height, weight, peak inspiratory flow, forced expiratory volume in 1 second, and forced vital capacity.
- Application of linear and logistic regression analyses to assess relationships between variables.
Main Results:
- All studied children demonstrated peak inspiratory flow >0.5 L/s, sufficient for dry powder inhaler activation.
- Significant correlations were found between peak inspiratory flow and forced vital capacity (R2=0.50), particularly in boys (R2=0.65).
- Peak inspiratory flow did not correlate with height, age, weight, body mass index, or predicted expiratory flow values.
Conclusions:
- Children with significant CF lung disease typically maintain adequate peak inspiratory flow for dry powder inhalers.
- A forced vital capacity <2.5 L may predict a peak inspiratory flow <2.0 L/s, indicating a potential need for metered dose inhalers with spacers.
- Further research is recommended to explore the relationship between expiratory flow and peak inspiratory flow against internal resistance.
Objective:
To show that in children with moderately severe cystic fibrosis lung disease: (i). inspiratory flow may be reduced; and (ii). peak inspiratory flow may be predicted from height, expiratory flow analysis or body mass index.
Methods:
All children attending the Royal Children's Hospital, Melbourne, between May and July, 2001 who had cystic fibrosis, were aged > 5 years, were able to perform spirometry reproducibly and who had a forced expiratory volume in 1 s < 60% predicted were prospectively enrolled. Height, weight, peak inspiratory flow, forced expiratory volume in 1 s and forced vital capacity were recorded. Linear regression analysis was performed.
Results:
The age range was 9.4-19.9 years. Sixteen boys and 11 girls were studied. All children had a peak inspiratory flow > 0.5 L/s. There was a significant relationship between peak inspiratory flow and forced vital capacity (R2 = 0.50) especially in boys (R2 = 0.65). In boys, peak inspiratory flow was significantly related to forced expiratory volume in 1 s (R2 = 0.47). There was no relationship between peak inspiratory flow and predicted values of expiratory flow, age, height, weight or body mass index. Logistic regression was used to predict the probability that peak inspiratory flow was < 2.0 L/s for a given forced vital capacity. If the forced vital capacity is > 2.5 L, peak inspiratory flow is likely to be > 2.0 L/s.
Conclusions:
In children with significant cystic fibrosis lung disease, peak inspiratory flow is likely to be > 0.5 L/s, which is required to activate dry powder inhalers. If the forced vital capacity is < 2.5 L, the peak inspiratory flow may be < 2.0 L/s, and a metered dose inhaler and spacer should be considered. Further studies that investigate the relationship between expiratory flow and peak inspiratory flow against an internal resistance are needed.