Reduced vital capacity after methacholine challenge in early childhood--is it due to trapped air or loss of motivation.
In a previous study we assessed the feasibility of measuring bronchial-reactivity (BHR) in young asthmatic children by the determination of PC(20)-FEV(1) along with clinical end-of-test criteria during a methacholine challenge test (MCT). The end-point was associated with a significant reduction in both flow and vital capacity values. The findings could be due to the children's loss of motivation, which may preclude use of this test. Alternatively, if it reflects air trapping during airway obstruction, it might reinforce its applicability in preschool age children.


OBJECTIVE
To elucidate the mechanism of low vital capacity at PC(20)-FEV(1) in preschool age children.


METHODS
Twenty-eight children (3.3-6.9 years) with recurrent respiratory symptoms.


METHODS
An MCT was carried out using tripling doses (0.06-13.9 mg/ml) delivered by a dosimeter. Spirometry was measured at baseline and after each inhalation in duplicate sets. Whole body plethysmography was measured at baseline and at end-of-test (defined by clinical criteria) according to the recommendations for older populations.


RESULTS
Plethysmography was reliably performed by 20 children before and after MCT. At baseline, lung function was within the healthy range. At end-of-test (PC(20)-FEV(1)=4.02+/-3.47 mg/ml), the spirometry parameters and specific conductance values were markedly reduced in correlation with a significant increase in residual volume and resistance.


CONCLUSIONS
The study shows that diminished vital capacity is due to the increase in FRC at end-of-test. Our findings support the use of PC(20)-FEV(1) during BHR in young children and suggest that lung volume measurement by a plethysmograph may be feasible in early childhood. Larger studies should be performed to establish the clinical applicability of PC20-FEV1 determination in the preschool age.
Vilozni
Daphna
D
Pediatric Pulmonary Unit, Meyer Children's Hospital, Rambam Medical Center, Haifa, Israel. avi_vil@bezeqint.net
Hakim
Fahed
F
Adler
Adi
A
Livnat
Galit
G
Bar-Yishay
Ephraim
E
Bentur
Lea
L
D001249:Asthma / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D016535:Bronchial Hyperreactivity / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000523:psychology; D016085:Bronchoconstrictor Agents; D002648:Child; D002675:Child, Preschool; D005541:Forced Expiratory Volume / Q000187:drug effects; D005652:Functional Residual Capacity / Q000187:drug effects; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008176:Lung Volume Measurements; D016210:Methacholine Chloride; D009042:Motivation; D010993:Plethysmography, Whole Body / Q000379:methods; D013147:Spirometry / Q000379:methods; D014797:Vital Capacity / Q000187:drug effects / Q000502:physiology
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride