General characteristics of the included children
In total, 112 children were included (see flow chart in Figure 1). The characteristics of the selected children are summarized in Table 1. The population consisted of 59 girls (57.3%) and 53 boys (42.7%), with a median age of 13.9 years [11.6 -16]. Among them, 84 children (75%) had severe asthma (GINA 4 to 5) and 28 (25%) non-severe asthma (GINA 1 to 3).
The reason for carrying out the HVT was the presence of symptoms suggestive of HVS for 53 children (47.3%), the persistence of asthma symptoms despite good compliance with treatment for 21 (18.8%), and the systematic search for HVS in the context of the exploration of difficult-to-treat asthma for 38 (33.9%). The Nijmegen questionnaire was performed for 103 children (92%) and the median Nijmegen score was 23 [15-29].
Among the 112 children, 108 underwent a HVT (96.4%), for which the results are presented in Table 1.
The HVT was negative for 34 patients (31.5%) and positive for 74 (68.5%). The characteristics of children with a positive HVT and those with a negative HVT are presented in Table 2. The baseline PCO2 at the start of the HVT was lower for children with a positive HVT than those with a negative test (35 mmHg [34-37] vs. 36 mmHg [35 -38], p < 0.01). The PCO2attained after the hyperventilation phase was also lower for children with a positive HVT than those with a negative test (18 mmHg [17-20] vs 22.5 mmHg [19-26.5], p < 0.01). Finally, the time to return to baseline PCO2 was longer for children with a positive HVT than those with a negative test (5 min [4-7] versus 1.5 min [1-2.1], p < 0.01). Symptoms reproduced during the HVT are presented in Figure 2. The most frequently reproduced symptoms among children with a positive HVT were dizziness for 58 children (78%), headaches for 49 (66%), and palpitations for 33 (45%).
Girls had a positive HVT more frequently than boys (59 girls (57.3%) vs 53 boys (42.7%), p = 0.03). Children with a positive HVT were older than those with a negative HVT (14.2 years [12.6-16.8] vs 12.7 years [9.3-14.7], p < 0.01). The frequency of perennial allergic rhinitis was higher among children with a positive HVT than those with a negative test (35 [47.3%] vs 14 [41.2%], p = 0.04). Children with a positive HVT had more IgE-mediated food allergies than those with a negative test (26 [35.1%] vs 2 [5.9%], p < 0.01).