ABSTRACT
Background: Hyperventilation syndrome (HVS) may be associated with asthma. In the absence of a gold standard diagnosis for children, its impact on asthma has been rarely assessed.
Objective: to assess the impact of HVS, diagnosed by a positive hyperventilation test (HVT), on the symptoms and lung function of children with asthma and determine the diagnostic value of the Nijmegen questionnaire in comparison to a HVT.
Methods: Data from asthmatic children followed in the department of Pediatric Pulmonology of Necker Hospital and explored for HVS were retrospectively analyzed. HVS was diagnosed by a positive HVT. Asthma symptoms and lung function were assessed in children with or without a positive HVT. The sensitivity and specificity of the Nijmegen questionnaire were determined relative to the positivity of a HVT.
Results: Data from 112 asthmatic children, median age 13.9 years [11.6–16], were analyzed. Twenty-eight children (25%) had mild or moderate asthma and 84 (75%) severe asthma. The HVT was performed on 108 children and was negative for 34 (31.5%) and positive for 74 (68.5%). The number of asthma exacerbations in the past 12 months, ACT score, and lung function did not differ between children with a positive HVT and a negative HVT. The Nijmegen questionnaire was administered to 103 children. With a threshold of 23, its sensitivity was 56.3% and specificity 56.3%.
Conclusion: The symptoms and lung function of adolescents with asthma are not affected by the presence of HVS. The sensitivity and specificity of the Nijmegen questionnaire are low.
Keywords: hyperventilation syndrome, hyperventilation test, severe asthma, children
INTRODUCTION
Hyperventilation syndrome (HVS) is characterized by a set of respiratory and extra-respiratory symptoms secondary to inappropriate hyperventilation in relation to metabolic demand, leading to acute or chronic symptoms 1–3. These symptoms, varied and non-specific, can most often be partially or totally reproduced by voluntary hyperventilation 4–6. However, there are no established diagnostic criteria. HVS is most often confirmed using the Nijmegen questionnaire, for which the positivity threshold is often considered to be 23 7–12. Positivity thresholds ranging from 17 to 25 have also been used to diagnose HVS6,10,13. The Nijmegen questionnaire has not been validated on children.
A number of authors have suggested that a positive hyperventilation test (HVT) could be the gold standard for the diagnosis of HVS6,7,14. The HVT makes it possible to reproduce the symptoms of hyperventilation by voluntary hyperventilation and evaluate the evolution of exhaled capnia according to the phase of the test14–16. It combines the evaluation of objective criteria: baseline PETCO2 (partial pressure of CO2 at the end of expiration before hyperventilation), time to return to baseline PETCO2, low PETCO2 (partial pressure of CO2 at the end of expiration after hyperventilation) and subjective criteria (reproduction of symptoms). However, the criteria for HVT positivity are not standardized 14,16–21. They most often consist of the reproduction of at least two symptoms of hyperventilation associated with a delay in the normalization of PETCO2 or a severe drop in PETCO2 after hyperventilation14,18,21. The specificity of the HVT was estimated to be between 60 and 66% in a study in which the gold standard for the diagnosis of HVS was a placebo test of hyperventilation with the administration of CO2 concomitantly with hyperventilation 22. The sensitivity of the HVT has been shown to be 91.8% and the specificity 90.7% for adults with severe asthma 6. The value of the HVT is a subject of debate because HVS can be isocapnic, and some consider that only the regression of symptoms after respiratory recovery make it possible to diagnose HVS 11. Nevertheless, the HVT allows the reproducible and objective evaluation of HVS by combining clinical and paraclinical criteria. HVS can be associated with asthma or be a differential diagnosis of asthma 1,2,4. The prevalence of HVS is estimated to be between 5 and 26% among asthmatic children9,23. The validity and reproducibility of the Nijmegen questionnaire has not yet been fully established in this population.
Few studies have focused on HVS in asthmatic children. In a study of 760 adolescents, 120 of whom (15.8%) had asthma, the Nijmegen score was positive for 47 of the 760 adolescents (6.2%), of whom 31 (25.8%) were asthmatic 9. In another study of 203 children with asthma, the Nijmegen score was positive in 5% of cases, the asthma was controlled for 63% of the children, and 70% had non-severe asthma. None of these studies investigated the impact of HVS on asthma symptoms23. Finally, the diagnostic value of the Nijmegen questionnaire relative to the HVT has been little studied.
The objectives of this study were to evaluate: i) the impact of HVS on the asthma symptoms and lung function of asthmatic children diagnosed with a positive HVT and ii) the diagnostic value of the Nijmegen questionnaire compared to the HVT for the diagnosis of HVS in asthmatic children.