Sodium cromoglycate-induced changes in the dose-response curve of inhaled methacholine and histamine in asthmatic children

The effect of inhalation of 2 per cent solution of sodium cromoglycate compared to that of saline on the bronchial response to methacholine and histamine was studied in 30 asthmatic children. Seven of 17 children challenged with methacholine showed decreased sensitivity after pretreatment with sodium cromoglycate. In 4 of 13 children, sodium cromoglycate attenuated the response to inhaled histamine. We conclude that in some asthmatic children, sodium cromoglycate provides significant protection against these nonallergenic challenges. This may have some therapeutic implications in the management of these patients. Our findings raise the possibility that sodium cromoglycate might have an action on cholinergic or irritant receptor sites in addition to inhibition of mast cell degranulation.

Pulmonary function abnormalities in asymptomatic children after hydrocarbon pneumonitis

To assess the effect of hydrocarbon pneumonitis on the developing lung, we studied the pulmonary function of 17 asymptomatic children, 8 to 14 years after the initial insult. Fourteen of the 17 subjects (82%) had one or more pulmonary function abnormalities, the most frequent being a high volume of isoflow. Volume of isoflow, ratio residual volume to total lung capacity, slope of phase III, flow rates at 50% and 25% of vital capacity and 60% of the total lung capacity, one-second forced expiratory volume, and maximum midexpiratory flow rate differed significantly (P less than .05) from values in control groups. Closing volume and closing capacity were not significantly different. Residual abnormalities present in children after hydrocarbon pneumonitis can be explained on the basis of small airway obstruction and/or loss of elastic recoil. These children may be at risk for the development of chronic lung disease as adults when they are exposed to exogenous factors such as air pollution or smoking.

A respiratory jacket for ventilatory measurements in children

The properties of an air-filled polyurethane-coated nylon jacket for measuring volume parameters were determined on a model and in 13 subjects. There was a linear relationship between jacket pressure on a logarithmic scale and the lung volume change over an operating pressure range of 0.7-6 cmH2O. The magnitude of pressure change was frequency dependent. The magnitude of a calibration signal was reduced by superimposed tidal breathing. For the jacket tested, the calibration signal during tidal breathing was 87% of the calibration during apnea. With these properties established, a calibration technique was devised and tested on 13 infants. Corrected tidal volumes (VT) obtained with the jacket correlated well with those obtained with a pneumotachograph (r = 0.986). At the operating pressures used the jacket caused no significant change in functional residual capacity (FRC), VT, or frequency. The jacket is a reliable technique for measurement of VT and immediate changes in FRC in awake children.

Bronchial hyperreactivity to histamine and methacholine in asthmatic children after inhalation of SCH 1000 and chlorpheniramine maleate

Nine asthmatic patients with a mean age of 14 yr received bronchial challenges with histamine and methacholine. The challenges were repeated after inhalation of 80 microgram of SCH 1000 (ipratropium bromide) and 5 mg of chlorpheniramine maleate. The provocation doses which produced a 20% fall in forced expiratory volume in 1 sec (FEV1) and the slopes of the dose-response curves were analyzed. SCH 1000 prevented methacholine-induced bronchoconstriction and chlorpheniramine prevented methacholine-induced bronchoconstriction. There was no significant change in the dose-response curve of histamine after SCH 1000 or in the dose-response curve of methacholine after chlorpheniramine. The findings indicate that the mechanisms and receptor sites involved in bronchial provocation by histamine and methacholine are distinctly different. The histamine response is unlikely to be vagally mediated because histamine-induced bronchoconstriction was not prevented by SCH 1000. Both SCH 1000 and chlorpheniramine caused significant bronchodilatation, suggesting the presence of both histamine- and vagal-dependent bronchomotor tone.

The response to exercise in normal and asthmatic children

Twenty-five normal and 105 asthmatic children were exercised on a treadmill. Pulmonary function was assessed before and after exercise. The maximum fall from the resting value in normal subjects depended on the test used: PEFR 12.5%; FEV1 10%; MMEF 26%; V50 30%; V25 33%. Using these criteria, PEFR and FEV1 detected 99% of those asthmatic children who had a positive exercise response. The largest fall from the resting value was seen with the MMEF, but this test detected only 70% of the positive responders. The pre-exercise function did not affect the severity of the response but did have an effect on the incidence of exercise-induced bronchospasm.

Comparative study of histamine and exercise challenges in asthmatic children

Fifty asthmatic children were tested with both a standardized treadmill exercise and a histamine inhalation on 2 separate days. Ninety per cent had a positive response to histamine, whereas 74 per cent had demonstrable exercise-induced bronchoconstriction. There was a close relationship between responsiveness to histamine and exercise, because all patients who responded to histamine had exercise-induced bronchoconstriction. Eight children (16 per cent) responded to histamine only. Although prechallenge pulmonary function has an effect on the incidence of exercise-induced bronchoconstriction, it does not appear to influence the responsiveness to histamine. Therefore, when provocation testing is being done for the purpose of diagnosing asthma, histamine is preferable to exercise.

Pulmonary function abnormalities in symptom-free children after bronchiolitis

Twenty-three children less than 18 months old who had clinical and radiological evidence of bronchiolitis and remained symptom-free thereafter were studied to determine pulmonary function ten years later. Abnormal Pao2, Viso V and RV/TLC ratio were found in the majority of subjects, and 31.3% had abnormalities in all three tests; four and one-half percent had exercise-induced bronchospasm. These changes indicate a residual parenchymal or airways lesion following bronchiolitis.