Manfred Modl

Atopy, lung function and bronchial responsiveness in symptom-free paediatric asthma patients

In adolescence, some paediatric asthma patients will become symptom-free and require no further treatment. There is little information on the atopic status, lung function and bronchial responsiveness of these patients. Symptom-free asthma patients (n=118) aged 7.7-19.2 yrs, were evaluated 1 year after termination of therapy. Bronchial asthma had previously been diagnosed on the basis of recurrent wheezing episodes. Atopic status was assessed by skin-prick testing. Baseline lung function was measured by spirometry, flow-volume curve and plethysmography. Bronchial responsiveness was assessed nonpharmacologically by cold dry air challenge. Eighty one patients had at least one positive skin test result, and the remaining 37 were defined as nonatopic. In atopic subjects, the prevalence of bronchial hyperresponsiveness was significantly higher than in nonatopic patients (41 out of 81 versus 7 out of 37; p=0.001). Atopic subjects showed a significantly lower maximal expiratory flow at 25% remaining vital capacity (p<0.05) and a higher residual volume (p<0.05) than nonatopic subjects. Nonatopic subjects were significantly younger than atopic patients (p<0.01). These symptom- and medication-free paediatric and adolescent asthma patients could, thus, be divided into two groups: 1) atopic subjects with a tendency towards bronchial hyperresponsiveness; and 2) nonatopic subjects with better lung function and normal bronchial responsiveness In view of the increased understanding of the epidemiology of early childhood wheezing, these findings support the concept of different pathogenic mechanisms underlying wheezing episodes in early childhood.

Reproducibility of forced expiratory flow and volume measurements in infants with bronchiolitis.

The end‐tidal rapid thoracoabdominal compression (ETRTC) technique is an established method for lung function testing in infancy. Previous work in healthy infants, however, has shown that measurements with the newly developed raised volume rapid thoracoabdominal compression (RVRTC) technique are more reproducible than those with the ETRTC technique. So far, reproducibility of the two techniques has not been compared in infants with acute airway disease. Twenty‐three infants with acute viral bronchiolitis underwent lung function assessment with both the ETRTC and the RVRTC technique. A series of 8–10 measurements with each technique was done in randomized order. Forced expired volumes at 0.5, 0.75, and 1 sec after chest compression (FEV0.5, FEV0.75, and FEV1.0) were measured with the RVRTC technique; maximum expiratory flow at functional residual capacity (V′maxFRC) was measured with the ETRTC technique. Group mean intrasubject coefficients of variation (CV) were 4.84% for FEV0.5, 5.01% for FEV0.75, 5.43% for FEV1.0, and 13.79% for V′maxFRC, respectively.

Comparing methods for assessing bronchial responsiveness in children: single step cold air challenge, multiple step cold air challenge, and histamine provocation

Cold air challenge (CACh) can be applied by either a single step (SSCACh) or a multiple step (MSCACh) protocol. The interrelationship of the responses of the different protocols has not yet been studied. Furthermore, there is contradictory information on the correlation of cold air challenge responses to the outcome of pharmacological provocations. A single and a multiple step cold air challenge and a histamine provocation were performed in random order on three consecutive days on 28 children and adolescents with bronchial asthma, who were currently symptom- and medication-free. Single step cold air challenge consisted of a 4 min isocapnic hyperventilation of dry, -10 degrees C air; the subjectss response was quantified by the induced change in forced expiratory volume in one second (FEV1). Multiple step cold air challenge consisted of a series of 3 min, cold dry air hyperventilation steps from 20 to 80% of maximal voluntary ventilation (MVV); response was expressed as the provocative dose causing a 10% fall in FEV1 (PD10). Histamine provocation consisted of a series of 2 min inhalations of stepwise increasing histamine concentrations from 0.03 to 8.0 mg.mL-1; response was expressed as the provocative concentration of histamine causing a 20% fall in FEV1 (PC20). Change in FEV1 (delta FEV1) (SSCACh) correlated closely with PD10 (MSCACh); scatter around the regression line was minimal. With one exception, both types of CACh identified the same subjects as hyper- and normoresponsive. delta FEV1 (SSCACh) correlated significantly to PC20 (histamine), but scatter around the regression line was substantial. The correlation of PD10 (MSCACh) to PC20 (histamine) failed to reach statistical significance. These results indicate that the stimulus applied and the bronchoconstrictor mechanism activated, and not the challenge protocol, determine the outcome of a cold air challenge. In clinical practice, a brief single step cold air challenge can substitute for a more time-consuming multiple step cold air challenge. As nonpharmacological challenges seem to measure a different type of bronchial responsiveness, neither a single step nor a multiple step cold air challenge can substitute for a pharmacological provocation.

Forced Expiratory Flow-Volume Measurements

In cooperative subjects, voluntary forced expiratory maneuvers are a generally accepted tool for the diagnosis and management of lung diseases.The development of special techniques rendered forced e