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Background: Asthma is characterized in part by small airways dysfunction. Peak expiratory flow (PEF) measurement has been suggested by all international guidelines as an important tool in asthma management. The correlation between PEF and FEV(1) but not with forced expired flow at 50% of vital capacity (FEF(50)) is well-established.Study Objective: To determine the value of PEF measurement as a predictor of small airways status as expressed by FEF(50).Design: Analysis of the association between PEF and FEF(50) in single and multiple determinations.Patients: One hundred eleven asthmatic children (mean age, 11.8 years), grouped in the following way according to FEV(1) values: within normal range (n = 46); mildly reduced FEV(1) (n = 44); and moderately/severely reduced FEV(1) (n = 21).Results: Overall, FEF(50) and PEF were significantly correlated (r = 0.49; p < 0.0001). However, in 41.6% of the patients, the actual FEF(50) differed by > 20% from the calculated FEF(50). PEF has a high specificity (82.4%) but a poor sensitivity (51.7%) to detect FEF(50) status. PEF was better able to reflect abnormal FEF(50) in the patients with more severe asthma and to reflect normal FEF(50) values in the healthier patients. In patients with multiple measurements (n = 40), the correlation between FEF(50) and PEF was significantly better than that derived from a single determination (multiple measurements r = 0.77; single measurement, r = 0.49).Conclusions: Although PEF is an important tool in the management of asthmatic patients, it does not yield a complete picture because it is not sensitive in detecting small airways function. It is best used at home along with regular spirometry measurements at the clinic. PEF may serve as a better index of changes in small airways function once an individual regression is determined. [ABSTRACT FROM AUTHOR]

Abstract. Partial expiratory flow-volume maneuvers have been performed on nine occasions on six infants with a variety of pulmonary problems using a new technique for thoracic compression. The infants were placed within an inflatable bag that was, itself, within a canvas bag. By sudden controlled inflation of the inner bag at end inspiration, partial expiratory flow-volume curves were generated and recorded by means of a face mask and pneumotachograph. By comparing these flow results with those airway resistance and lung volume measurements obtained from the infants in whole body plethysmography and by noting the effect of inhaling a helium/ oxygen gas mixture, it was possible to partition the airway obstruction between large and small airways. The presence of small airway obstruction was noted in the absence of changes in airway resistance or lung volume in several instances. A complete evaluation of airway function should include this test of forced expiration for greater understanding and treatment of lung disease in infancy. [ABSTRACT FROM AUTHOR]

To compare the refractory period that follows exercise and isocapnic hyperventilation, 10 asthmatic children performed two pairs of challenge tests in random order at least six hours apart. In pair A a hyperventilation challenge was followed by an exercise challenge and in pair B the order was reversed. Both pairs of tests were done while the children were breathing cold dry air. Tests were matched in terms of work load, ventilation, and end tidal carbon dioxide tension (PCO2). The mean percentage fall in FEV1 (delta FEV1) after the first challenge (hyperventilation) of pair A and the first challenge (exercise) of pair B were the same (30% (SEM 2%)) and 30% (4%) respectively). The mean delta FEV1 of the exercise test following hyperventilation in pair A and of hyperventilation following exercise in pair B was 22% (4%) and 18% (4%) respectively. Both these latter results were significantly lower than the respective delta FEV1 when the challenge was the first test of the pair. Although the mean refractoriness index (reduction in induced asthma in the second test of each pair compared with the first test) was greater when exercise was the first challenge, the difference was not significant. [ABSTRACT FROM AUTHOR]

To evaluate the effect of negative ionisation of inspired air on bronchial reactivity, 11 asthmatic children were challenged twice by exercise and 10 were challenged twice by histamine inhalation. The children breathed negatively ionised air (4 X 10(5) - 10 X 10(5) ions/cm3) or control room air in random order in a double-blind fashion. All challenges were matched in terms of basal lung function and the exercise tests were matched in terms of ventilation and respiratory heat loss. Exercise-induced asthma was significantly attenuated by exposure to negatively ionised air, the mean postexercise fall in one-second forced expiratory volume (FEV1) being 29% (SE 5%) of the initial value after the control and 21% (3%) after the ionised air test (p less than 0.02). Ten of the 11 subjects developed less exercise-induced asthma while breathing ionised air. Although the median dose of histamine (cumulative breath units) which caused a constant fall in FEV1 for each individual was higher with the ionised air challenge than with the control challenge the difference was not significant. Five of the 10 subjects were less sensitive to histamine and the other five more sensitive when breathing ionised air. It is concluded that negative ionisation of inspired air can modulate the bronchial response to exercise but the effect on the response to histamine is much more variable. [ABSTRACT FROM AUTHOR]

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Thirteen asthmatic children aged 9-14 years participated in a double blind randomised trial to compare the effectiveness and duration of action of 2 formulations of sodium cromoglycate; one a 20 mg capsule of powdered sodium cromoglycate delivered by turbo inhaler (spinhaler), and the other 1 mg of aerosolised sodium cromoglycate delivered by pressurised cannister inhaler (aerosol). The children performed exercise tests on each of 3 days in a 10 day period--15 minutes, 2 hours, and 6 hours after inhalation of powder, aerosol, or a placebo. Two patients were not protected from exercise induced asthma by either formulation of sodium cromoglycate. Among the remaining patients both formulations gave good protection from exercise induced asthma 15 minutes after inhalation, and the effect of both wore off steadily over the next 6 hours. The spinhaler gave appreciably better protection than the aerosol at 15 minutes after inhalation, and was the only formulation to provide good protection at 2 hours and 6 hours. The more limited effectiveness of the aerosol may be explained by the lower dose of sodium cromoglycate and the more complicated inhalation technique required. [ABSTRACT FROM AUTHOR]

A previously healthy two year old boy had an adenoviral infection at the age of 13 months and developed hyperlucency of the left lung, chronic respiratory distress, and failure to thrive. Bronchodilators and steroid treatment had no effect. Radionuclide lung scans using an intravenous bolus of xenon-133 both before and after treatment showed substantially reduced function on the hyperlucent side and modestly reduced function on the other side. Fibreoptic bronchoscopy showed no structural abnormalities. Partial forced expiratory flow volume (PEFV) curves, generated from end inspiration by rapid compression of the chest wall with an inflatable jacket, were obtained from the total respiratory system and from each lung separately by inflating a Fogarty catheter in the contralateral mainstem bronchus. Expiratory flow rates and volumes during both tidal breathing and PEFV manoeuvres were considerably decreased in the hyperlucent lung. PEFV curves from the "healthy" right lung and from the total respiratory system were similar in shape and showed a moderately obstructive pattern. The right lung ventilated about four times as much as the left when measured by bronchospirometry and about three times as much when measured by the radionuclide technique. The lung scans appeared to reflect adequately the functional abnormality in this infant with the Swyer-James syndrome. [ABSTRACT FROM AUTHOR]

Lung function was measured in 28 infants with cystic fibrosis and repeated in 17 of the infants during the first year of life. Thoracic gas volume (TGV) and specific airway conductance (sGaw) were measured plethysmographically and maximum forced expiratory flow at functional residual capacity (VmaxFRC) was derived from the partial expiratory flow-volume curve. At the time of the initial evaluation respiratory function was correlated with the clinical condition of the infants but not with age. There was a good correlation between sGaw and VmaxFRC when both were expressed as percentages of the predicted normal values. On the basis of the normal range for sGaw the infants were divided into two groups. Group A (n = 9), who had normal sGaw, were younger and had a lower clinical score and normal VmaxFRC and TGV values. Group B (n = 19), who had low sGaw, had increased TGV and decreased VmaxFRC. There was no correlation with age for any measure of lung function for the population as a whole. Repeat testing was undertaken at intervals in 17 representative infants. In most of these infants the relation between sGaw and VmaxFRC was maintained; there was no evidence that VmaxFRC was affected before sGaw. There was no functional evidence that the earliest changes in cystic fibrosis occur in small airways, as reflected by changes in VmaxFRC in infancy. [ABSTRACT FROM PUBLISHER]

Objective: To assess the effect of lowering altitude to that of the lowest place on earth (Dead Sea) on arterial oxygenation and exercise performance in patients with hypoxemia and end-stage lung disease.Design: A cohort of 10 patients.Setting: Pulmonary function laboratories in Jerusalem, Israel, and at the Dead Sea.Patients: 10 patients with end-stage lung disease who were receiving long-term oxygen therapy. The 4 males and 6 females were 12 to 77 years old. Four patients had chronic obstructive pulmonary disease; 2 had cystic fibrosis; 3 had pulmonary fibrosis; and 1 had pulmonary hypertension (thromboembolic). Mean forced vital capacity was 1.54 L (54% of predicted value) and mean forced expiratory volume in 1 second was 0.85 L (35% of predicted value).Measurements: Spirometry, blood gas analysis, progressive exercise testing, and sleep oximetry were done in Jerusalem (altitude, 800 m above sea level; barometric pressure, 696 mm Hg); the same measurements were done 6 days after arrival at the Dead Sea (altitude, 402 m below sea level; barometric pressure, 800 mm Hg) and then 7 to 14 days later in Jerusalem.Results: Arterial oxygenation increased from a median partial pressure of arterial oxygen of 51.6 mm Hg in Jerusalem to 67.0 mm Hg at the Dead Sea, an increase of 15.2 mm Hg (95% CI of paired difference, 4.1 to 20.4 mm Hg; P = 0.001). Partial pressure of arterial carbon dioxide increased from a median of 43.2 to 45.9 mm Hg, an increase of 2.7 mm Hg (CI, 0.5 to 6.4 mm Hg; P = 0.004), with a borderline significant change in the alveolar-arterial gradient. Arterial oxygen saturation increased from a median of 87.7% to 92.8%, a change of 4.8% (CI, 1.9% to 9.8%; P = 0.003). Exercise performance also improved as maximum oxygen uptake increased from a median of 827 mL/min to 1056 mL/min, an increase of 203 mL/min (CI, 54 to 388 mL/min; P = 0.006). Sleep oximetry also improved as median arterial oxygen saturation measured during sleep increased from 85% to 90%, a change of 5% (CI, 2% to 7%; P = 0.005), and percentage of sleep time with an oxygen saturation rate of 90% or more increased from a median of 24% to 73%, a change of 49% (CI, 20% to 87%; P = 0.02). No change in spirometry was noted. All patients felt less dyspneic and reported improved functional capacity with reduced need for oxygen.Conclusion: Descent to low altitude can improve arterial oxygenation, exercise performance, and sleep oximetry and consequently the quality of life in patients with hypoxemia and advanced lung disease. [ABSTRACT FROM AUTHOR]