Between January and December 2018, children practicing football, track and field, and indoor sports (fencing, judo, handball, basketball and volleyball), who were admitted as outpatients for routine health checks to the Department of Pediatrics of Filantropia Municipal Hospital Craiova (Craiova, Romania) were enrolled in a prospective study. The study included children aged >6 years (mean age, 11.7 years) who were enrolled in the Department of Sports Medicine as athletes mainly practicing one of the aforementioned sports and who had the ability to perform the technical maneuvers (spirometry and FeNO measurements) required. The exclusion criteria were acute febrile illness and/or acute respiratory illness, pulmonary chronic diseases (other than asthma) and cardiovascular chronic diseases. The smokers, the subjects who performed intense physical exercise or those who ingested foods rich in dietary nitrate during the same day were also rejected.

The bronchial inflammation of the patients was assessed using the Niox Vero exhaled nitric oxide analyzer (Aerocrine AB) based on the general accepted guidelines (6), and the results were compared taking into account the personal history of asthma, the type of sport and the spirometry results. FeNO results >35 parts per billion (ppb) suggested high bronchial inflammation. The spirometry evaluation was considered abnormal (suggesting asthma) if the peak expiratory flow (PEF) and the forced expiratory volume per one second (FEV1) were <80% of the predicted values, and the FEV1/FVC ratio was <85%. The bronchodilator test was considered positive if a 12% or 200 ml increase was noted in either FEV1 or forced vital capacity (FVC), respectively.

Demographic and clinical data were initially regrouped using Microsoft Excel (Microsoft Corporation). This program was used to describe the findings in terms of percentages and group definitions. The statistical analysis was performed using SPSS version 20 (IBM Corp.). Group comparisons were performed using the non-parametric Mann-Whitney U or Kruskal-Wallis H test, followed by Dunn's procedure and Bonferroni adjustment, where appropriate, with P<0.05 considered to indicate a statistically significant difference.

The 404 patients included in the present study originated mostly from urban areas. Overall, 59.65% (241 cases) were boys, as the main sport in the Craiova region is football and boys are prevalent in this field (Table I).

The asthma prevalence in the study group was 3.96% (16 children; Fig. 1). Asthmatic patients were diagnosed with the mild form of the disease and the physical exercise was not a trigger for asthma exacerbation.

After anamnesis and clinical examination, FeNO measurements followed by pulmonary function testing (spirometry: Pre- and post-bronchodilator).

In terms of spirometric evaluation, 33 children showed signs suggesting asthma (PEF and FEV1/FVC baseline levels <80% of predicted values and/or reversibility after use of a bronchodilatator via Ventolin inhaler). Only 10 of these cases were previously diagnosed as asthma.

The biochemical detection of exhaled nitric oxide (FeNO) was performed before the spirometry and the results are based on molecular proportion as ppb. The patients already diagnosed with asthma had slightly elevated FeNO levels compared with the rest of the study group. The Mann-Whitney U test was performed to determine if there were any differences in FeNO values between children with asthma and children without asthma. Distribution values for these groups were not similar, as assessed by visual inspection. FeNO values for the asthma group (mean rank, 178.78) and non-asthma group (mean rank, 202.48) were not statistically significantly different (U=2724.5; z=-0.80; P=0.407; Table II).

The majority of the patients came from urban areas (mostly Craiova), as in our previous studies (15-17). There was no statistical difference with regard to living area or sex in the patient cohort. A total of 4 patients (3 already diagnosed with asthma) had very high levels of exhaled nitric oxide (>100 ppb).

The next step was to evaluate the FeNO values in various types of sports. The average and standard deviation measurements are presented in Fig. 2. The average values ranged from 21 ppb for track and field athletes to 38 ppb for fencing. It was noted that the children practicing football and track and field had slightly decreased FeNO levels, but the number of patients was too small to obtain statistical significance among groups. The outdoor (football, and track and field) and indoor (fencing, judo, handball, basketball and volleyball) sports were then compared. Children enrolled in indoor sports showed elevated levels of exhaled nitric oxide; thus, it can be concluded that they have a higher level of bronchial inflammation compared with those children who participate in outdoor sports. The Mann-Whitney U test was also performed to determine if there were any differences in FeNO values between children playing indoor sports and those playing outdoor sports. Distributions of FeNO values for these groups were similar, as assessed by visual inspection. Median FeNO level was statistically significantly higher for indoor sports (median value, 19) than for outdoor sports (median value, 12) (U=26811.5; z=5.516; P<0.0005; Table II).

The next stage of the study compared the children at risk from asthma (the 23 cases without a diagnosis but with positive spirometry results) with the asthma group and with the children without a history or spirometry suggesting asthma.

Unexpectedly, the children at risk of asthma had even higher values of FeNO compared with the asthma group. FeNO levels had similar distributions for all groups, as assessed by visual inspection of a boxplot chart. The Kruskal-Wallis H test was performed to determine if there were differences in FeNO values between the four groups of participants (asthma group with either positive or negative spirometry, and the no asthma group with either positive or negative spirometry). Median FeNO levels were not statistically significantly different between groups [χ²(3), 5.446; P=0.142; Table II].