Repeatability of lung function tests during methacholine challenge in wheezy infants
- Christophe Delacourt,
- Marie-Rose Benoist,
- Serge Waernessyckle,
- Patrick Rufin,
- Jean-Jacques Brouard,
- Jacques de Blic,
- Pierre Scheinmann
- Laboratoire d’Explorations Fonctionnelles Respiratoires, Service de Pneumologie et Allergologie Pédiatriques, Hôpital des Enfants Malades, 149 rue de Sèvres, 75015 Paris, France
- Dr C Delacourt.
- Received 28 November 1997
- Revision requested 19 January 1998
- Revised 29 May 1998
- Accepted 5 June 1998
Abstract
BACKGROUND The repeatability of lung function tests and methacholine inhalation tests was evaluated in recurrently wheezy infants over a one month period using the rapid thoracic compression technique.
METHODS Eighty one wheezy, symptom free infants had pairs of methacholine challenge tests performed one month apart. Maximal flow at functional residual capacity (V˙maxfrc) and transcutaneous oxygen tension (Ptco 2) were measured at baseline and after methacholine inhalation. Provocative doses of methacholine causing a 15% fall in Ptco 2(PD15Ptco 2) or a 30% fall inV˙maxfrc (PD30V˙maxfrc) were determined.
RESULTS Large changes in V˙maxfrcwere measured from T1 to T2 with a mean difference between measurements (T2—T1) of 7 (113) ml/s and a 95% range for a single determination forV˙maxfrc of 160 ml/s. The mean (SD) difference between pairs of PD30V˙maxfrc measurements was 0.33 (1.89) doubling doses with a 95% range for a single determination of 2.7 doubling doses. Repeatability of PD15Ptco 2 was similar. A change of 3.7 doubling doses of methacholine measured on successive occasions represents a significant change.
CONCLUSIONS Baseline V˙maxfrcvalues are highly variable in wheezy, symptom free infants. Using either V˙maxfrc or Ptco 2 as the outcome measure for methacholine challenges provided similar repeatability. A change of more than 3.7 doubling doses of methacholine is required for clinical significance.
