Biomedical subjects

E Bar-Yishay

Publications and source records attributed to E Bar-Yishay.

60 records · Page 4Linked to original sources

PubMed1982

Refractory period after exercise-induced asthma unexplained by respiratory heat loss.

Fifteen asthmatic children and young adults each exercised for 6 min by cycling on a cycle ergometer while breathing either cold (4.1 degrees C +/- 0.5 SEM) and dry (2.05 mg/L +/- 0.05) air or warm (37.2 degrees C +/- 0.3) fully saturated air. Each subject performed 4 tests arranged in pairs. Test pair A consisted of cold dry exercise followed by another cold dry exercise and test pair B consisted of a warm humid exercise followed by a cold dry exercise. Ventilation, heart rate, and gas exchange were closely matched in all 4 tests in each subject with a mean oxygen consumption of 34.8 +/- 0.8 ml/min/kg. In test pair A, all subjects were rendered refractory by the first cold dry exercise as manifested by a significant attenuation of their exercise-induced asthma (EIA) after the second cold dry test (per cent decrease in FEV1, delta FEV1 = 16 +/- 4 compared with 38 +/- 4). In 3 subjects, the warm humid exercise did not cause EIA and did not render them refractory to the second cold dry exercise. The 12 remaining subjects exhibited a refractory period similar to that shown in test pair A. They did not develop EIA after the warm humid test (delta FEV1 = 1 +/- 2), but after the subsequent cold dry exercise the per cent decrease in FEV1 was 19 +/- 3, similar to that in the second of the 2 cold dry exercise tests. These experiments suggest that in the majority of subjects exercise per se appears to be the cause for refractoriness and not airway cooling or bronchoconstriction.

Adolescent↗

PubMed1982

Does the pattern of ventilation determine the degree of lung damage following intensive care of the newborn?

Lung function tests were performed on 14 infants 22 to 67 wk following mechanical ventilation of 6 h to 51 days and on 5 infants of comparable age who had been treated with continuous positive airway pressure (CPAP). Airway resistance increased (P less than 0.01) and specific airway conductance decreased (P less than 0.001) in the ventilated infants compared with the CPAP-treated group who were normal. The airway resistance and specific airway conductance were normal in two ventilated infants and in one CPAP-treated infant who were studied earlier in the neonatal period. There were no significant differences in thoracic gas volume between groups of ventilated and nonventilated babies studied initially or at follow-up. There was no relationship between lung damage and the following: peak inspiratory pressure, the duration of high pressure ventilation, the level of CPAP or its duration, or the duration of greater than 60% oxygen administration. The degree of lung damage was not related to the maximum ventilatory frequency used, but there was a significant correlation with the duration of rapid frequency ventilation. This study supports the view that barotrauma is a major cause of lung disease following neonatal intensive care.

Airway Resistance↗

PubMed1980

Prediction of maximal expiratory flow in excised human lungs.

The predictions of the wave-speed theory of flow limitations were tested against measured values of maximal expiratory flow (Vmax) in nine normal excised human lungs. We obtained static pressure-volume curves and deflation pressure-area (PA) curves of the first three to four airway generations. The pressure drop from the alveolus to the flow-limitation site was assumed to consist of a peripheral frictional loss (estimated from a catheter upstream from the flow-limitation site) and a convective acceleration pressure drop. Predicted Vmax was determined graphically by finding the lowest flow for which the Bernoulli PA curve was tangent to one of the bronchial PA curves. At the point of tangency, local flow speed equals local wave speed. At low lung volumes a point of tangency with the PA curves of the first few generations did not exist, and the flow-limitation site was assumed to be the minimal bronchial area at zero transpulmonary pressure. There was good agreement between measured and predicted Vmax. Measured Vmax was not different from Vmax predicted from normal living man. The wave-speed theory predicted flow over much of the vital capacity, but other mechanisms may limit flow at low lung volumes.

Adolescent↗

PubMedDate not supplied

Flow-pressure looping during plethysmography in wheezy infants.

Marked looping of the expiratory portion of the flow-pressure relationship was noted in some infants during measurements of airway resistance in a whole-body plethysmograph while the respired air was maintained at body temperature and humidity. An investigation of 13 infants who had varying degrees of airway obstruction showed that there was a negative correlation (r = 0.72) between the severity of the looping and specific airway conductance (SGaw). An even stronger correlation (r = 0.85) was found between the tangent of the angle of phase lag between flow and pressure (theta) and the forced expiratory time constant (t) obtained from the partial forced expiratory flow-volume curve. Such a relationship would be predicted from a model in which the lung behaved as a simple electrical resistance-capacitance network during expiration. It is suggested that the looping is the result of small airway closure during expiration in wheezy infants, with a consequent rise in resistance and prolongation of the time constant of the lung.

Airway Resistance↗

PubMedDate not supplied

The functional response of infants with persistent wheezing to nebulized beclomethasone dipropionate.

Lung function was measured in nine infants, ages 15-36 weeks, who had persistent wheezing, apparently following acute bronchiolitis, before and after 2 weeks of treatment with either inhaled nebulized beclomethasone dipropionate (BDP) or placebo in a randomized, double blind, crossover trial. The effect of nebulized albuterol (Salbutamol) was measured before and after the steroid treatment. Thoracic gas volume (TGV) and specific airway conductance (SGaw) were determined using a whole body plethysmograph, and forced expiratory flow at resting lung volume (VmaxFRC) was determined with a thoracoabdominal compression jacket. All infants had marked airways obstruction before treatment with mean +/- SE VmaxFRC of 24 +/- 4% predicted and SGaw of 37 +/- 5% predicted. Two weeks of placebo treatment had no significant effect on lung function, but after 2 weeks of BDP inhalation there was a significant rise in SGaw to 61 +/- 7% (P less than 0.005). VmaxFRC increased to 42 +/- 13% but the difference did not reach significance. Respiratory rate and clinical score for retractions and wheezing also fell significantly with BDP therapy (P less than 0.01 and P less than 0.001 respectively). Albuterol had no effect on lung function either before or during steroid therapy. Steroids may have a role in the management of persistent wheezing following bronchiolitis.

Administration, Intranasal↗

PubMedDate not supplied

Lung function in infancy and childhood following neonatal intensive care.

Pulmonary function studies were performed in 11 neonatal intensive care survivors both during infancy and later in childhood. Lung function was compared with the respiratory support given in the neonatal period. The mean +/- SE thoracic gas volume was 96 +/- 4% predicted in infancy and rose to 122 +/- 8% predicted during childhood (P less than 0.005). The specific airway conductance (SGaw) in infancy was 57 +/- 7% predicted and rose to 90 +/- 8% predicted in childhood (P less than 0.0025). Abnormalities in SGaw were found only in ventilated infants, and there was a negative logarithmic correlation between the treatment score in the neonatal period and the SGaw in both infancy and childhood. The data indicate a long-term improvement in airway conductance of moderately affected infants with the development of mild hyperinflation in childhood possibly resulting from residual small airway abnormalities despite a symptomless clinical course. The residual abnormalities in prematurely born infants were in proportion to the intensity of treatment required in the neonatal period.

Child↗