[Pulmonary gas transfer in pediatrics (carbon monoxide and dioxide)].
In pediatrics, measurements of gaseous transfer in steady-state (SS) are easily applied. Nevertheless, interpretation of results is uncertain because predicted values depend on numerous metabolic and ventilatory parameters. In healthy subjects, the only invariant parameter of reference, beside the blood gas, is the CO uptake (VCO) when normalized by the reject of CO2 (VCO2). Theoretically, a deficit of VCO/VCO2 (VCOSpecifique = SpVCO) should not be observed on a young asthmatic in remission. Such a deficit should be due to either a circulatory impairment of the "gas-exchanging organ" or an alveolary ventilation failure. However, the respiratory equivalent for CO2 (V/VCO2) increases in case of hyperventilation. When not observed at rest, hyperventilation can occur at exercise, that can again induce a non specific bronchitic hyperreactivity.


OBJECTIVE
To define links: 1) between the spirometry of the young asthmatic and the value of ERCO2 and CO tests; 2) between a circulatory anomaly and the value of SpVCO.


METHODS
The asthmatic adolescents aged between 10 and 20 were separated from infants (age < 10) and classified in three degrees of spirometrical alteration according to the maximum expiratory flow when 25% of the forced vital capacity remains in the lung (V25) and the residual volume (RV); 48 adolescents were examined at rest and 17 were exercising on a cyclo-ergometer. Two adolescents with circulatory anomaly, one by idiopathic pulmonary hemosiderosis (IPH), the other by agenesia of the left lung were examined at rest and exercise.


RESULTS
In asthmatics at rest the three degrees of spirometric alteration differed from one another in ERCO2 and classical CO tests; SpVCO alone was not altered at rest or during exercise. However the deficit of SpVCO, confirmed during the exercise, was significant in HPI.


CONCLUSIONS
Simple and quick simultaneous measurements of (FICO-FECO) and FECO2 allows one to detect hyperventilation of young asthmatic subjects at rest and during exercise, or can confirm a circulatory anomaly.
Bréant
J
J
Service d'insuffisance respiratoire, La Musse, Evreux, France.
Vascaut
L
L
Fleury
M F
MF
D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D002245:Carbon Dioxide / Q000378:metabolism*; D002248:Carbon Monoxide / Q000378:metabolism*; D002648:Child; D002675:Child, Preschool; D005080:Exercise Test; D005260:Female; D006801:Humans; D007223:Infant; D008168:Lung / Q000502:physiology* / Q000503:physiopathology*; D008297:Male; D008448:Maximal Expiratory Flow Rate; D012016:Reference Values; D012146:Rest; D013147:Spirometry / Q000379:methods
D002245:Carbon Dioxide; D002248:Carbon Monoxide