No abstract

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.

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.

We present a case of extralobar pulmonary sequestration between the left lower lobe and diaphragm with an unusual arterial blood supply and venous drainage. Angiography revealed a large systemic artery arising from the left subclavian artery. The venous return paralleled this anomalous artery and drained into the left subclavian vein. This case illustrates the wide anatomic variability of such complex bronchovascular anomalies. Careful preoperative evaluation of both the arterial supply and venous drainage is important to avoid intraoperative complications. Angiography provides clear definition of these abnormal vascular structures, which is essential for appropriate therapeutic management.

ABSTRACT. The passive, single-breath, flow-volume technique is a simple method for measuring the resistance (Rrs) and the compliance (Crs) of the respiratory system in infants. S o far, the potential influence of end inspiratory occlusion time on these measurements has not been investigated. We measured Rrs and Crs in 36 infants and toddlers with bronchiolitis; in each child, a spectrum of nine fixed occlusion times, ranging from 90 to 600 ms, was applied in random sequence. Increasing the duration of occlusions from 90 to 275 ms resulted in marked stepwise changes of measured Rrs and Crs; occlusions longer than 275 ms, however, produced highly reproducible measurements, as expressed 1 ) by minimal absolute differences between measured values at subsequent occlusion times and 2) by minimal percentage changes of measured values from one occlusion time to the next. There was no influence of age on the results; reproducible measurements were made in children as old a s 1.5 y. This suggests that, in infants with bronchiolitis, 1 ) occlusions between 300 and 450 ms might be ideal for obtaining reliable measurements, and 2) the age range for applying this method can be extended into the 2nd y of life. (Pediatv Res 33: 273-277, 1993) Abbreviations YE, expired volume VE, expiratory flow Pao, pressure measured a t airway opening Rrs, resistance of the respiratory system Crs, compliance of the respiratory system Trs, time constant of the respiratory system More than three decades ago, Comroe et al.(1) described a technique for measuring respiratory mechanics in animals by a sjngle passive deflation. Subsequently, McIlroy et al. (2) plotted VE against VE to obtain the time constant of this passive exhalation in anesthetized human subjects. , as well as LeSouef et al. (4,5), then adapted this "single-breath technique" for measuring passive respiratory mechanics in newborns and infants; in this age group, relaxation of the respiratory muscles is achieved by activating the Hering-Breuer reflex via an end-inspiratory occlusion of the airway. When the Pao reaches a plateau, muscle relaxation and pressure equilibration have occurred. The subsequent termination of the occlusion results in a passive exhalation, which is recorded in a flow-volume mode. From the linear portion of this plot, a Trs is calculated. Trs together with Pao allows for calculating the Rrs and Crs.This simple technique might develop into a routine method for assessing lung function in infants; as a prerequisite, however, several methodologic questions must be addressed. One problem that so far has not been sufficiently evaluated is the question of "optimum end-inspiratory occlusion time." Too-short occlusions do not result in complete muscle relaxation and pressure equilibration. As is evident from the lack of any linear portion of the expiratory flow-volume plot, too-long ones are disturbed by recommencing respiratory muscle activity.So far, most investigators have observed Pao visually and have released their manual occlusion when the tracing appeared f...