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The influence of breathhold on peak expiratory flow in normal and asthmatic children
I Matsumoto1, S Walker, P D Sly
1Division of Clinical Sciences, Institute for Child Health Research, Perth, Western Australia.
Insights
Breathholding at total lung capacity (TLC) reduces expiratory flow in children. This effect, seen in both healthy and asthmatic children, highlights the impact of airway viscoelasticity on lung function measurements.
Area of Science:
- Pulmonary Physiology
- Pediatric Respiratory Medicine
Background:
- Breathholding at total lung capacity (TLC) previously showed a 10% reduction in peak expiratory flow (PEF) in adults.
- This reduction was linked to airway wall viscoelasticity and increased airway compliance (Caw).
Purpose of the Study:
- To investigate the effect of breathholding at TLC on expiratory flows in children.
- To compare this effect between asthmatic and healthy children.
- To assess the impact of bronchodilation on breathhold-induced flow changes.
Main Methods:
- 15 asthmatic and 14 healthy children (10-15 years) performed maximal expiratory flows (MEF) with and without a 5-second breathhold at TLC.
- The protocol was repeated after inhaling 800 micrograms of salbutamol.
- Measurements included PEF, forced expiratory volume in one second (FEV1), and maximal expiratory flow at 50% vital capacity (V'50).
Main Results:
- Breathholding at TLC significantly decreased PEF in both asthmatic (5.8%) and healthy children (10.3%).
- Salbutamol administration reduced this PEF fall, making it non-significant in healthy children.
- Similar patterns of decreased flow were observed for FEV1 and V'50.
Conclusions:
- Breathholding at TLC dissipates airway viscoelastic energy, increasing compliance and decreasing maximal expiratory flows in children.
- The findings underscore the importance of standardizing the forced vital capacity maneuver to minimize variability in expiratory flow measurements.
- Asthmatic children showed a similar, though less pronounced, effect compared to healthy children.
Abstract:
We have previously demonstrated a 10% reduction in peak expiratory flow (PEF) in healthy adults following a breathhold at total lung capacity (TLC). This fall was attributed to dissipation of airway wall viscoelasticity, increasing airway wall compliance (Caw). To investigate this phenomenon in children and to determine whether the effect of breathhold would be greater in asthmatics than in normal children, 15 asthmatics and 14 normal children (aged 10-15 yrs) performed maximal post expirations (MFE) with and without a 5 s breathhold at TLC. The entire study was repeated following the inhalation of salbutamol (800 micrograms) to relax the airway smooth muscle (and to increase Caw). Breathhold at TLC resulted in a significant decrease in PEF both in the asthmatics (group mean fall 5.8%; p < 0.01) and normal children (group mean fall 10.3%; p < 0.05). Salbutamol diminished this fall, becoming nonsignificant in the normal children. Similar patterns were also seen in forced expiratory volume in one second (FEV1) and in maximal expiratory flow at 50% vital capacity (V'50). These data are consistent with the proposal that breathhold at total lung capacity dissipated viscoelastic energy (increasing airway compliance) and decreased maximal expiratory flows both in normal and asthmatic children. They also demonstrate the need to standardize the forced vital capacity manoeuvre to decrease the variability in the flows recorded during the subsequent forced expiration.