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Methacholine responsiveness using the raised volume forced expiration technique in infants
M J Hayden1, S G Devadason, P D Sly
1Department of Respiratory Medicine, Princess Margaret Hospital, Perth, Western Australia.
Summary
The raised volume forced expiration technique (RVFET) effectively detects methacholine-induced bronchoconstriction in infants. This newer method shows good agreement with the traditional tidal volume squeeze technique for assessing infant lung function.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Infant lung function assessment traditionally uses the tidal volume "squeeze" technique.
- The raised volume forced expiration technique (RVFET) offers assessment over an extended volume range.
Purpose of the Study:
- To compare methacholine responsiveness using RVFET and the tidal volume technique in infants.
- To evaluate the ability of RVFET to detect methacholine-induced bronchoconstriction.
Main Methods:
- 11 infants underwent methacholine challenge testing.
- Lung function measured using maximal expiratory flow at functional residual capacity (V.max,FRC) via tidal volume technique.
- Lung function also measured using forced expiratory volume in time (FEV(t)) via RVFET.
- Provocative concentrations (PC) for a 40% fall in V.max,FRC and 15-20% fall in FEV(t) were calculated.
Main Results:
- No significant differences were found in provocative concentrations between the two methods, though RVFET required slightly lower concentrations.
- Good agreement was observed between V.max,FRC and FEV(t) measurements.
- Bronchoconstriction was not attenuated by the forced inspiration in the RVFET maneuver.
Conclusions:
- The raised volume forced expiration technique (RVFET) is capable of detecting methacholine-induced bronchoconstriction in infants.
- RVFET demonstrates good agreement with the tidal volume technique for assessing infant airway responsiveness.