Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting.

This study describes the feasibility, repeatability, and interrater reliability of the measurement of airway resistance by the interrupter technique (Rint) in children 2-5 yrs of age, and examines whether reversibility to bronchodilator can be demonstrated in wheezy children. The mean of six Rint values was taken as a measurement. If subjects could complete one measurement and then a second 15 min after bronchodilator, baseline testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy children was measured after bronchodilator. Fifty-six per cent of 2-3-yr-olds (n=79), 81% of 3-4-yr-olds (n=104) and 95% of 4-5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% completed reversibility testing. Baseline measurements were 0.47-2.56 kPa x L(-1) x s. Repeatabilities (2 SD of the mean differences between measurements) at 30 s in the three age bands were 0.21, 0.17 and 0.15 kPa x L(-1) x s and 0.19 kPa x L(-1) x s after placebo. Using 0.21 kPa x L(-1) x s as the threshold for reversibility, reversibility was demonstrated in most wheezy children. Interrater reliability was 0.15 kPa x L(-1) x s. Preschool children can undertake measurements of airway resistance by the interrupter technique in ambulatory settings and reversibility to bronchodilator in wheezy children can be demonstrated. This technique promises to be a useful clinical and research tool.     

Applicability of interrupter resistance measurements for evaluation of exercise-induced bronchoconstriction in children

The interrupter technique is a noninvasive method for measuring air-flow resistance during tidal breathing. This method requires minimal cooperation, and is therefore promising for use in uncooperative children. The aim of this study was to evaluate applicability interrupter resistance (Rint) measurements in the assessment of exercise-induced bronchoconstriction (EIB). Fifty children aged 5-12 years with mild to moderate asthma were tested by exercise challenge, consisting of free outdoor running for 6 min at 80-90% of maximal predicted heart rate for age. Rint, forced expiratory volume in 1 sec (FEV1), and peak expiratory flow (PEF) were measured before and 10 min after exercise. EIB was defined as a fall of 10% or more in FEV1 after exercise. The repeatability of Rint was assessed, and its response to exercise challenge was compared with current standardized methods. The mean intermeasurement coefficient of variation was 4.6% (SD, +/- 3.0%), and the repeatability coefficient was 0.056 kPa/l/sec. Eighteen (36%) of the 50 children had EIB after exercise challenge test. The area under the receiver-operating characteristic (ROC) curve was 0.953 (95% confidence interval, 0.853-0.992; P < 0.001), and the optimal Rint cutoff value was 15.2%, producing a sensitivity of 88.9% and a specificity of 96.9%. The positive and negative predictive values were 94.1% and 93.9%, respectively. The kappa value between FEV1 and Rint was 0.83. The repeatability of Rint measurements was good, and the results of exercise challenge tests using Rint measurements have excellent agreement with the current standardized methods to detect EIB. Considering that only minimal comprehension and coordination are needed without forced breathing technique, the Rint measurement can provide a useful alternative for assessment of EIB in children unable to perform reliable spirometry.     

Exercised-induced asthma in soccer players ages from 8 to 13 years

The purpose of this study was the detection of exercise induced asthma in soccer players aged 8-13 years. Thirty boys, 8-13 years old participated in the study. They were coming from an athletic team of north of Thessaloniki. The study included clinical examination, administration of a respiratory health questionnaire and the exercise -- free running -- test with spirometric measurements. Spirometric measurements were performed by using a microspirometer, before exercise and 2, 5, 10, 15 and 30 min after a 6 min free running exercise (80 - 90 % max heart rate). The highest forced expiratory volume in one second (FEV (1)) value before exercise was compared with the lowest of post exercise values. The results showed a decline in FEV (1) > 15 % in 12 out of 30 children. Particularly, decline in FEV (1) was present in 1 (11 %) out of 9 children with free personal medical history but positive family history for asthma, in 3 (25 %) out of 12 children with allergies, and in 8 (89 %) out of 9 children with asthma. Symptoms were reported by 9 of 12 children with fall in FEV (1) > 15 %, during the 6 min exercise test, who had no symptoms during the soccer games. Identification of EIA by exercise challenge test in young athletes is a useful component for the diagnosis of bronchial hyperresponsiveness. Similar studies should be performed on older and younger athletes who participate in different sports and games.     

Measurements of interrupter resistance: reference values for children 3-13 yrs of age.

The interrupter technique is a convenient and sensitive technique for studying airway function in subjects who cannot actively participate in (forced) ventilatory function tests. Reference values for preschool children exist but are lacking for children >7 yrs. Reference values were obtained for expiratory interrupter resistance (R(int,e)) in 208 healthy Dutch Caucasian children 3-13 yrs of age. A curvilinear relationship between R(int,e) and height was observed, similar to published airways resistance data measured by plethysmography. No significant differences in cross-sectional trend or level of R(int,e) were observed according to sex. It was found that Z-scores could be used to express individual R(int,e) values and to describe intra- and interindividual differences based on the reference equation: 10logR(int,e)=0.645-0.00668x standing height (cm) kPa x L(-1) x s(-1) and residual SD (0.093 kPa x L(-1) x s(-1)). Expiratory interrupter resistance provides a tool for clinical and epidemiological assessment of airway function in a large age range.     

How should airways resistance be measured in young children: mask or mouthpiece?

The reproducibility and acceptability of airways resistance measurements using the interrupter technique (MicroRint) obtained using a mouthpiece were compared with those using a face mask. Fifty children aged 4-7 yrs performed four sets of six Rint measurements; two using a mouthpiece and two using a face mask with integral mouthpiece. Complete data were obtained from 45 (90%) children using the mouthpiece and 43 (86%) children using the mask. The two methods were equally repeatable with comparable intraclass correlation coefficients (ICC) and coefficients of variation. Mean Rint values obtained using the mouthpiece were significantly lower than those using the face mask ((mean+/-SD) mouthpiece=0.81+/-0.18 kPa x L(-1) x s, mask=0.88+/-0.24 kPa x L(-1) x s p=0.0002). Although the mean paired differences between the two methods were small (0.07 kPa x L(-1) x s), the ICC and limits of agreement confirmed that the two methods could not be used interchangeably. Sixty-seven per cent of children preferred the face mask but this was more time-consuming (p = 0.03). Children did not produce more repeatable results using their preferred method, nor did they improve with practice. Repeatable airway resistance measurements using the interrupter technique can be obtained from young children using either a mouthpiece or a face mask, but there are significant clinical and statistical differences between the results obtained.     

Exercise challenge test in 3- to 6-year-old asthmatic children

RATIONALE: The exercise challenge test (ECT) is a common tool to assess exercise-induced asthma (EIA) in school-aged children. EIA has not been explored in the early childhood setting. OBJECTIVE: To assess the existence of EIA in children in this age group. MEASUREMENTS AND MAIN RESULTS: A 6-min, controlled, free-run test was performed in 55 children (age range, 3 to 6 years old) who were classified into the following groups: 30 children in whom asthma had been previously diagnosed (group A); and 25 children with prolonged coughing (group B). Spirometry measurements were obtained before the run, and at 1, 2, 3, 5, 10, and 20 min after the run. A positive finding of EIA was defined as a 13% decrease from baseline FEV(1) or baseline forced expiratory volume in the first 0.5 s (FEV(0.5)). The actual duration of each run was age-related (mean [+/- SD] duration, 4.8 +/- 0.8 min). The nadir in indexes occurred after a mean time of 2.98 +/- 1.31 min. A positive EIA finding determined by FEV(1) was present in 15 children, and by FEV(0.5) in 34 children. Twenty-six children were from group A, but only 8 children were from group B. Wheezing and/or prolonged expiration were associated with a positive test result in 31 of 34 children. Coughing was frequent in children with both negative and positive ECT findings. CONCLUSION: The present study documents for the first time the presence of EIA in response to a free-run test in early childhood. Our findings suggest that a free-run test for the presence of EIA is suitable, but that the running duration is limited by age. The duration of airflow limitation after exercise is significantly earlier and shorter in young children with asthma compared with older children. FEV(0.5) is a better index than the traditional FEV(1) for describing positive ECT results in young children. The association of wheezing and/or prolonged expiration may help in defining EIA in early childhood in the absence of a spirometer.     

Airway resistance and atopy in preschool children with wheeze and cough.

The extent to which the measurement of airways resistance by the interrupter technique (Rint) distinguishes preschool children with previous wheeze from those with no respiratory symptoms and helps to classify subjects with persistent cough, was investigated. Rint was measured before and after salbutamol treatment in 82 children with recurrent wheeze, 58 with isolated cough and 48 with no symptoms (control subjects). Their mean age (range) was 3.7 yrs (2-<5 yrs). Median baseline Rint was higher (p<0.0001) in wheezers than in either coughers or control subjects (1.16, 0.94 and 0.88 kPa x L(-1) x s(-1) respectively); coughers did not differ significantly from control subjects (p=0.14). The median ratios of baseline to post-salbutamol measurements (bronchodilator response (BDR)) in the groups differed significantly (1.40, 1.27 and 1.07, p< or =0.01 for all), suggesting that coughers occupy an intermediate position. A BDR ratio of >1.22 had a specificity and sensitivity for wheeze of 80% and 76% respectively. Twenty-eight coughers had a BDR ratio >1.22. Wheezers' immunoglobulin E was inversely related to baseline Rint. It is concluded that measurements of airway resistance by the interrupter technique are useful for classifying preschool children with respiratory symptoms and could be used to monitor the effect of interventions. The relation between atopy and airways resistance suggests that they have separate roles in preschool wheezing. Coughers with a high bronchodilator response could represent "cough-variant" asthma in children who have baseline airway resistance by the interrupter technique measurements similar to control subjects. Whether these children develop classical asthma will only be known at follow-up later in childhood.     

Pre/postbronchodilator interrupter resistance values in healthy young children

The interrupter technique estimates flow resistance. It entails occlusion of the airways during tidal breathing while flow and mouth pressure are recorded. This noninvasive technique is easy to use in young children. The aim of the present study was to measure inspiratory and expiratory interrupter resistance (Rint(insp), Rint(exp)) before and after bronchodilator administration in young healthy white children. We designed a multicenter study using a standardized procedure for Rint measurements. Centers in five French cities studied 91 children (48 boys and 43 girls; height, 92 to 129 cm; mean age 5.3 +/- 1.4 years). Mean values were not significantly different for Rint(insp) and Rint(exp) (0.78 +/- 0.21 versus 0.78 +/- 0.20 KPa x L(-1) x second). However, the difference between Rint(insp) and Rint(exp) decreased significantly with age and being positive before 5 years and negative later on (p < 0.02). Rint(insp) and Rint(exp) decreased significantly with height (Rint(insp) [KPa x L(-1) x second] = 2.289 - 1.37. 10(-2) x H [cm], Rint(exp) [KPa. L(-1) x second] = 2.021 - 1.12.10(-2) x H [cm]; p < 0.001). Bronchodilator (salbutamol) administration significantly decreased Rint(insp) and Rint(exp) (p < 0.001). Bronchodilator-induced changes (% of predicted values) in mean Rint(insp) and mean Rint(exp) were -15% (95% confidence interval, -46 to +15%) and -12% (95% confidence interval, -46 to +22%), respectively. Sex did not affect pre- or postbronchodilator values. Data from the present study may prove useful for testing lung function in young children with respiratory disorders who failed to cooperate with forced expiratory maneuvers.     

Airway resistance by the interrupter technique: Which algorithm for measuring pressure?

Airway resistance using the interrupter technique (Rint) can be measured using commercial devices which employ different algorithms for estimating pressure change. We aim to describe differences in Rint due to algorithm. We compared Rint and change in Rint after bronchodilator, using four algorithms to estimate pressure change following interruption: 1) two-point back-extrapolation to interruption from points 70 msec and 30 msec from interruption, and similarly 2) to 15 msec from interruption, 3) at two-thirds from interruption, and 4) near end-interruption. Flow was measured immediately before interruption. Our subjects were 39 asymptomatic children 2-5 years old with previous intermittent wheeze. Rint differed significantly with algorithm. Geometric mean Rint (95% confidence interval (CI)) for algorithms 1-4 were 1.21 kPa x l(-1) x sec (1.18-1.24 kPa x l(-1) x sec), 1.31 kPa x l(-1) x sec (1.28-1.34 kPa x l(-1) x sec), 1.57 kPa x l(-1) x sec (1.54-1.61 kPa x l(-1) x sec) and 1.71 kPa x l(-1) x sec (1.67-1.75 kPa x l(-1) x sec), respectively. Measurement of change in R(int) following bronchodilator (BDR) did not differ on average with algorithm. Geometric means (95% CI) for BDR measurements for algorithms 1-4 were 29.9% (26.0-34.0%), 30.4% (26.4-34.5%), 32.9% (28.8-37.1%), and 31.7% (27.6-35.8%), respectively. However, measurement of change in individuals could differ by up to 40%, depending on algorithm. In conclusion, there are significant differences in Rint, depending on algorithm used to estimate pressure change. Measurement of change in Rint is unaffected on average, although in individuals there could be significant differences. Each laboratory should state its method and use the same algorithm for longitudinal and group data.     

Using baseline respiratory function data to optimize cycle exercise test duration

BACKGROUND: It is often difficult to select an appropriate workload increment for progressive cycle exercise tests in order to achieve optimal test duration (8-12 min). We hypothesize that baseline respiratory function can be systematically used to select appropriate workload increment to optimize test duration in patients referred to the clinical laboratory. METHODOLOGY: One hundred and eighty consecutive exercise tests (with increments of 15 W/min) were retrospectively assessed. Using regression analysis, an equation was generated that predicts the work rate increment that would provide exercise duration of 8-12 min. The validity of this equation was tested prospectively in 231 consecutive tests performed with the calculated workload increment rounded to the nearest 5 watts (W). RESULTS: The best regression equation was: workload increment (W/min)=1.94 x FEV1 (L) + 0.63 x TLCO (mmol/min per kPa) - 0.07 x age + 1.94 x gender (male=1, female=0) + 4.12 (r=0.85, P < 0.0001). Using this equation allowed selection of the most appropriate workload increment in 79% of tests and reduced the number of tests of non-optimal duration from 72% (for a fixed increment of 15 W/min) to 38%. CONCLUSIONS: Utilization of this regression equation allows standardization in the selection of workload increment, and reduces the number of cycle exercise tests of inadequate duration.     

Exercise-induced bronchoconstriction depends on exercise load

Exercise-induced bronchoconstriction (EIB) is often used as a measure of bronchial hyperresponsiveness and employed in epidemiological studies. Different tests are used, including free running tests with poor standardization of exercise load. The present study aimed to assess the role of exercise load in relationship to level of EIB. METHODS: 20 asthmatic children, 9-17 years old with a history of EIB, underwent two treadmill test with 85% and 95% exercise load. The children ran with increasing speed for the first 2 min until reaching a heart rate of 85% or 95% of calculated maximum (220-age) and maintained this speed for the last 4 min. Lung function was measured before running, and 0, 3, 6, 10 and 15 min after the run. Borg scale for perceived exertion was employed for children's self-evaluation of exercise load. RESULTS: Peak heart rate, mean Borg score during 85% exercise load was 178.7/13.6 and during 95% was 194.3/18.2 (P<0.001). Maximum fall in FEV1 after 85% exercise load was 8.84% vs. 25.11% after 95% (P<0.001). Nine subjects (40%) fell > or = 10% in FEV1 after 85% exercise load vs. 20 subjects (100%) after 95% exercise load. EIB from the 95% exercise load test had markedly higher correlation with serum ECP (r=0.77, P<0.001). CONCLUSION: Exercise load is essential for the interpretation of EIB, and strict standardization of exercise tests should be undertaken. The EIB from the high exercise load tests seemed better correlated to inflammatory activity than the low exercise load test.     

Field exercise vs laboratory eucapnic voluntary hyperventilation to identify airway hyperresponsiveness in elite cold weather athletes

STUDY OBJECTIVE: For the 2002 Winter Olympic Games, athletes were required to submit objective evidence of asthma or exercise-induced bronchoconstriction (EIB) for approval to inhale a beta(2)-agonist. Eucapnic voluntary hyperventilation (EVH) was recommended as a laboratory challenge that would identify airway hyperresponsiveness (AHR) consistent with EIB. The objective was to compare the change in FEV(1) provoked by EVH with that provoked by exercise in cold weather athletes. DESIGN: Spirometry was measured before and for 15 min after challenges. The two challenges were performed in random order at least 24 h apart. SETTING: EVH was performed in the laboratory at 19 degrees C, and exercise took place in the field in the cold (2 degrees C, 45% relative humidity). PARTICIPANTS: Thirty-eight athletes (25 female subjects; median age, 16 years). INTERVENTIONS: For the EVH, athletes inhaled dry air containing 5% carbon dioxide for 6 min at a target ventilation equivalent to 30 times baseline FEV(1). Exercise was performed by cross-country skiing, ice skating, or running for 6 to 8 min. MEASUREMENTS AND RESULTS: AHR consistent with EIB was defined as >or= 10% fall in FEV(1) from baseline after challenge. Eleven athletes were exercise positive (EX+) [FEV(1) fall, 20.5 +/- 7.3%], and 17 athletes were EVH positive (FEV(1) fall, 14.5 +/- 4.5%) [mean +/- SD]. Of 19 subjects with AHR, 58% were identified by exercise and 89% were identified by EVH. EVH identified 9 of 11 subjects who were EX+ and a further 8 subjects with potential for EIB. The average ventilation during EVH was 28 times FEV(1). CONCLUSION: Performing EVH for 6 min in the laboratory had a greater chance of identifying AHR in these athletes compared with 6 to 8 min of field exercise in the cold. The EVH test will be useful to evaluate elite summer sports athletes whose widely different forms of exercise provide an "equipment" challenge to any laboratory.     

The effects of surgically treated pulmonary stenosis on lung growth and cardiopulmonary function in children during rest and exercise.

The effects of high pulmonary blood flow and pressure on pulmonary development are well understood, but the effect of low pulmonary flow/pressure is not. Pulmonary stenosis (PS) was therefore used as a model to determine its effect on lung development, which was assessed noninvasively by carbon monoxide transfer at rest and during exercise. One hundred and six control children (55 males, 8-16 yrs) and 11 children with isolated valvar or subvalvar PS surgically corrected > or =10 yrs prior to the study without residual stenosis/regurgitation were evaluated. Measurements of effective pulmonary blood flow, stroke volume, arteriovenous oxygen difference (AVO), transfer factor and transfer constant, alveolar ventilation and anaerobic threshold were performed using a mass spectrometer. Data from the normal children allowed calculation of z-scores for the study group matched for age, sex, pubertal stage and surface area. PS children at rest had a significantly lower forced expired volume in one second, cardiac frequency and transfer constant with a raised oxygen consumption and AVO which persisted on exercise. During exercise, the cardiac frequency was 12 beats x min(-1) slower and AVO 0.017 L greater than controls (p<0.05). A persistently mildly raised effective functional residual capacity (0.2 L x m(-2)) during exercise led to a reduced transfer constant (0.35 mmol x min(-1) x kPa(-1) x L(-1)), although the percentage rise (28%) from rest to peak exercise was normal. The percentage fall in stroke volume from the penultimate exercise stage to peak exercise stage was greater in PS children (24%, 95% confidence interval 11-37) than control children (2.4, -2-10, p<0.005). In conclusion, although the effects are small, pulmonary stenosis does affect cardiopulmonary function after surgery. This needs to be considered when contemplating the timing of treatment.     

Food-dependent exercise-induced anaphylaxis occurred only in a warm but not in a cold environment

Food-dependent exercise-induced anaphylaxis (FDEIA) is a type of exercise-induced anaphylaxis associated with postprandial exercise. We describe a 19-year-old man with FDEIA. Our patient complained of urticaria, angioedema, dizziness and hypotension associated with exercise after ingestion of walnut-containing foods in a warm environment. Skin prick test and prick to prick test were positive for walnut antigen. The attack didn't occur by free running outside for 10 min 2 h after taking walnuts, and the temperature was about -2℃. Food-exercise test was done again in a warm environment based on prior history. Anaphylaxis was developed after exercise for 10 min in a warm environment after taking walnuts. Some environmental factors such as high temperature and high humidity or cold temperature may influence exercise-induced anaphylaxis. In our case, the cofactor was a warm environment: the challenge test done in a cold environment was negative, but positive in a warm environment. Physicians should be aware that the challenge test of FDEIA can show different results depending on temperature.     

Can bronchodilator response predict bronchial response to methacholine in preschool coughers?

The aim of the present study was to determine the relationship between bronchodilator response, assessed by interrupter resistance (Rint), and bronchial reactivity in preschool children with chronic cough. Thirty-eight children coughers (median age 5.0 years, range 2.8-6.4) were tested. Bronchodilator response was recorded within 4 months before methacholine challenge. Response to the latter was assessed using transcutaneous partial pressure of oxygen and Rint. Children were considered responders if a 20% fall in transcutaneous partial pressure of oxygen occurred during the bronchial challenge. Bronchodilator response was not different between responders (n = 24) and nonresponders (n = 14) [median (range) -0.11 (-0.44-0.09) vs. -0.08 (-0.21-0.10) kPa L(-1) sec; respectively]. However, none of the nonresponders had a bronchodilator response larger than -0.21 kPa L(-1) sec, this cutoff had a 100% positive and a 44% negative predictive value to predict a positive methacholine challenge. The relationship between bronchodilator response and bronchial methacholine responsiveness reached the limit of significance (P = 0.048). Furthermore, the magnitude of the bronchodilator response was correlated to the level of methacholine-induced level of bronchoconstriction (P = 0.01), and to the postchallenge bronchodilation (P = 0.04), all values expressed as % predicted. Moreover, the postbronchodilator Rint value obtained with preceding methacholine challenge was lower than the postbronchodilator value without preceding methacholine challenge in 71.4% (10/14) of the nonresponders and in only 33.3% (8/24) of the responders. Conclusions in preschool coughers bronchodilator response, assessed by the interrupter technique, was correlated to the bronchial responsiveness to methacholine. Non responders had a bronchodilator response not larger than -0.21 kPa L(-1) sec.     

Pulmonary function tests in preschool children with cystic fibrosis

Pulmonary function tests have rarely been assessed in preschool children with cystic fibrosis (CF). The objective of this multicenter study was to compare pulmonary function in 39 preschool children with CF (height, 90-130 cm; 16 homozygous Delta F508) and in 79 healthy control children. Functional residual capacity (helium dilution technique) and expiratory interrupter resistance (Rint(exp)) (interrupter technique) were measured. As compared with control children, children with CF had significantly higher Rint(exp), expressed as absolute values and as Z-scores (1.05 +/- 0.36 versus 0.80 +/- 0.20 kPa.L(-1). second, p < 0.0001; and 1.31 +/- 1.72 versus 0.19 +/- 0.97, p < 0.0001), and significantly lower specific expiratory interrupter conductance (1.29 +/- 0.34 versus 1.63 +/- 0.43 kPa(-1). second, p < 0.0001). The effect of the bronchodilator salbutamol on Rint(exp) was not significantly different between children with CF and control children. Rint(exp) Z-scores were significantly higher in children with CF who were exposed to passive smoke (n = 8) (p < 0.03). Children with CF and with a history of respiratory symptoms (n = 31) had significantly higher functional residual capacity Z-scores (p < 0.02) and lower specific expiratory interrupter conductance Z-scores (p < 0.04). Genotype did not influence the data. We conclude that Rint(exp) and functional residual capacity measurements may help to follow young children with CF who are unable to perform reproducible forced expiratory maneuvers.     

Pulmonary function tests in preschool children with asthma

Pulmonary function tests are seldom performed in preschool children with asthma. The aim of this multicenter study was to compare pulmonary function in 74 preschool children with asthma (height of 90-130 cm) and 84 healthy control subjects. Functional residual capacity (helium dilution technique) and expiratory interrupter resistance (interrupter technique) were measured. As compared with control children, children with asthma had a significantly higher resistance (0.77 +/- 0.20 vs. 0.92 +/- 0.22 kPa. L-1. second, p < 0.001) and significantly lower specific expiratory interrupter conductance (p < 0.005) values. Resistance values were significantly higher in children with asthma with than without symptoms on exertion (p < 0.05). The effect of bronchodilator administration, expressed as the percentage of baseline and predicted resistance values, was significantly greater in children with asthma than in control subjects (-18.6 +/- 13.6% vs. -11.2 +/- 15.2%, p 相似文献   

Mild to moderate asthmatics and free running.

We analyzed the bronchial response to free running in 48 mild to moderate extrinsic asthmatics and 36 nonasthmatics and also studied the relation between the methacholine hyperresponsiveness (expressed as PC20) and the changes in peak flow (PEF) post-exercise in an asthmatic group. The highest bronchial response to exercise was observed in asthmatic patients 10 min after free running (17.93 +/- 13.37%) and was significantly different from the nonasthmatics (U = 156; p > 0.00001). The correlation study disclosed a high correlation (r > or = 0.6) between the PC20 values (expressed as logarithmic transformation) and the exercise response (percent drop in the PEF measured 10 and 15 min post-exercise) in asthmatic subjects. With receiver operator characteristic (ROC) curves we obtained, as an ideal point, a percentage change in PEF (PEFR) of 8% or more measured 10 min post-exercise which reached 79.1% sensitivity and 89.7% specificity. We think that this exercise challenge can be used for detection of airway hyperresponsiveness in mild to moderate asthmatics.     

Exhaled nitric oxide decreases during exercise in non‐asthmatic children

Introduction: Exhaled nitric oxide (FE_NO) measurements are recommended to be performed before spirometry and exercise challenge tests because forced breathing might influence FE_NO values. Information on the effect of exercise on FE_NO is lacking in non‐asthmatic children. Aim: To investigate the effect on FE_NO of a standardized exercise challenge test on a treadmill in non‐asthmatic children with and without allergic rhinoconjunctivitis (AR) symptoms. Methods: From the case‐control study ‘Asthma and allergy among school children in Nordland’, 330 non‐asthmatic pupils age 8–16 years were enrolled. FE_NO was measured at baseline and at 1 min and 30 min after exercise challenge test by the single breath technique with EcoMedics Exhalazer® (Eco Physics, Duernten, Switzerland). Results: Pair‐wise comparison of FE_NO from baseline demonstrated a highly significant reduction in FE_NO post‐exercise for all children at 1 min (27.4%) and at 30 min (16.1%) (P < 0.001). The AR group had a significantly higher decline in FE_NO value at 1 min post‐exercise compared to the non‐AR group, 4.2 parts per billion (ppb) vs 2.6 ppb (P < 0.001). Decline in FE_NO immediately post‐exercise was more significant if baseline FE_NO was ≥ 20 ppb; mean reduction 9.9 (95% CI: 8.7–11.4) ppb. Conclusion: FE_NO is reduced by 27.4% immediately after a standardized treadmill exercise test in non‐asthmatic children. Pupils reporting AR symptoms demonstrate a larger decline in FE_NO value at 1 min post‐exercise compared to pupils without AR symptoms. These findings confirm that children should refrain from physical activity before FE_NO measurement. Please cite this paper as: Evjenth B, Hansen TE and Holt J. Exhaled nitric oxide decreases during exercise in non‐asthmatic children. Clin Respir J 2013; 7: 121–127.     

A comparison of two challenge tests for identifying exercise-induced bronchospasm in figure skaters

OBJECTIVES: Studies documenting the increased incidence of exercise-induced bronchospasm (EIB) in figure skaters have employed a method that incorporates on-ice exercise with rink-side spirometry. The literature suggests that bronchial provocation challenge testing is better than exercise testing for identifying EIB. To test this hypothesis in figure skaters, a unique athletic population that trains and competes in cold air, we compared these two methods in the same individuals. PATIENTS/METHODS: Two challenge tests were performed on a group of competitive figure skaters (n = 29, 26 female subjects; mean+/-SD age = 12.3+/-3.5 years): (1) rink-side (temperature = 14 degrees C, humidity = 60%) spirometry before and 1, 5, 10, and 15 min after 5 min of intense skating; and (2) eucapnic voluntary hyperventilation (EVH), breathing 5% CO2, 21% O2, balance N2 at a rate of 60% of maximum voluntary ventilation (not to exceed 70 L/min) for 5 min (temperature = 18 degrees C, humidity = 50%), with an identical pretest and posttest spirometry schedule. EIB was defined as at least one of the following: a > or =10% decline in Fev1; a > or = 20% decline in maximum midexpiratory flow rate; or a > or = 25% decline in peak expiratory flow rate. RESULTS: Sixteen of 29 skaters (55%) developed EIB: 9 were positive by on-ice testing; 12 were positive by EVH testing; 5 were positive on both tests; on-ice testing missed 7 skaters with EIB; EVH testing missed 4 with EIB. CONCLUSION: In the group of figure skaters studied, EVH challenge testing was better at identifying EIB than on-ice exercise testing. However, these data suggest that evaluation for EIB in athletes who train and compete in the cold should include exercise testing in cold air along with a challenge test such as EVH to increase the yield of positive responders.