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Biomedical subjects

E Bar-Yishay

Publications and source records attributed to E Bar-Yishay.

At least 55 records · Page 3Linked to original sources
PubMed1987

Functional residual capacity in healthy preschool children lying supine.

Functional residual capacity (FRC) was measured by the closed-circuit helium dilution method in 41 supine healthy children 1 month to 8 yr of age. In 20 children, the measurement was carried out while they were awake, and in the others, who were less cooperative, testing was done during ketamine anesthesia before elective surgery. There was no significant difference in the FRC values between these groups, and they were subsequently analyzed as a single group. For males and females separately and combined, FRC correlated significantly with height, age, and weight, both with linear and nonlinear regression analyses. No significant difference between the sexes was found. The best correlation of FRC was with height; the linear equation being FRC (ml) = -457.3 + 8.8 X height (cm) (r2 = 0.662), and the nonlinear equation being FRC (ml) = 0.0052 X [height (cm)]2.44 (r2 = 0.827).

Child↗
PubMed1986

Effect of heart weight on distribution of lung surface pressures in vertical dogs.

In head-up dogs the vertical gradient of transpulmonary pressure (VGTP) disappears after pneumothorax develops. Our laboratory recently confirmed that the heart moves downward and posteriorly with pneumothorax. To study the extent to which the heart is supported by the lungs, we used a linear elasticity model and finite-element analysis. The lung and heart were assumed to be symmetric along a vertical axis. Reported values of the elastic properties of lung and heart were assigned. The model was generated first without the heart, using the lung alone. The heart was then added to the model. Finally, heart weight was doubled. Adding the heart caused the VGTP to increase; doubling the heart weight further increased the VGTP. These increases were more pronounced at higher lung volumes. Lung inflation was accompanied by an upward displacement of the heart. Inclusion of the heart caused increased inhomogeneities in regional volume distribution. The effect of heart weight may in part explain why the VGTP in the head-up dog is greater than that predicted by lung density.

Animals↗
PubMed1986

Airway resistance measurements throughout the respiratory cycle in infants.

Using a constant-volume infant whole-body plethysmograph containing a heated rebreathing bag, we have been able to measure airway resistance (Raw) throughout the respiratory cycle using a computer-based technique. Data from the plethysmograph transducers are sampled at 60 Hz for the calculations and Raw is calculated at each point sampled during the breath, with appropriate corrections for absolute lung volume. It was found that in most cases Raw varied less with respect to tidal volume than to tidal flow. Various patterns of Raw change in relation to tidal volume were found. These included an elevated but relatively constant resistance, a progressively rising expiratory resistance, and in 3 infants with laryngomalacia, a progressively rising inspiratory resistance. It was also found that the dynamic performance of the rebreathing bag was such that considerable errors would occur if apparatus resistance was assumed to be constant and so the actual apparatus resistance at each point was subtracted from the total resistance to give Raw. In conclusion, Raw is not constant throughout the respiratory cycle in infants and the pattern of change conveys additional information.

Airway Resistance↗
PubMed1986

Can thoracic gas volume be measured in infants with airways obstruction?

Thoracic gas volume (Vtg) was measured in a whole-body, infant plethysmograph in 46 infants with recurrent wheezing after bronchiolitis, 25 infants with cystic fibrosis, and 6 infants without overt lung disease during the first 13 months of life. When related to weight or length, 56.5% of the bronchiolitic infants had low Vtg values, which were more than 2 SD below their predicted normal. The Vtg of the other groups was normal or above. The bronchiolitic infants with Vtg values in the normal range had more severe airways obstruction and it is probable that their Vtg values were also underestimated. Investigation of possible sources of technical or experimental error failed to reveal any explanation for the low Vtg in the bronchiolitic infants. In 5 infants, Vtg determined plethysmographically was correlated linearly to functional residual capacity determined by helium dilution, although Vtg values were greater in all. The administration of albuterol or treatment with steroids failed to make significant changes in Vtg in the bronchiolitic infants. It is suggested that there is a physiologic basis for the presumed underestimation of Vtg in wheezy infants after bronchiolitis, either because of uneven alveolar pressure changes within the chest leading to the effective exclusion of a portion of the lung volume or because there are some alveolar units with very low compliance that change little in volume during respiratory efforts against an occlusion. These results call into question the validity of the plethysmographic measurement of Vtg or airway resistance in these infants. If the error in Vtg is due to uneven alveolar pressure changes, it is suggested that the calculated specific airway conductance is probably correct.

Airway Obstruction↗
PubMed1986

Nemaline myopathy as a cause of sleep hypoventilation.

Two siblings, a 14.5-year-old boy and his 11.5-year-old sister, with congenital nemaline myopathy presented with severe respiratory failure and, in the case of the older patient, with cor pulmonale and systemic hypertension. The children were treated initially by continuous mechanical ventilation, but after a few weeks they only required ventilation at night. At the start of treatment, both were found to have a decreased ventilatory response to CO2 which apparently improved during 4 to 5 years of follow-up treatment. It has not been possible to wean them from nocturnal mechanical ventilation, but during the daytime they attend school and function almost normally. It is postulated that respiratory failure in nemaline myopathy may not be related to the severity of the muscle weakness but may result from a disturbance of the feedback required for normal control of breathing.

Adolescent↗
PubMed1985

Influence of the heart on the vertical gradient of transpulmonary pressure in dogs.

Estimations were made of the vertical gradient of transpulmonary pressure (VGTP) from measurements of esophageal pressure in nine head-up dogs at functional residual capacity (FRC) when alive, when dead, and after total bilateral pneumothorax. The VGTP of 0.4 cmH2O/cm height in the alive state was abolished by pneumothorax, and roentgenograms showed that the heart moved in a caudal-dorsal direction. There was a small but significant increase in the VGTP on going from FRC to near total lung capacity (TLC) in alive head-up dogs. In eight dead head-up dogs heart weight was increased by replacing various amounts of heart blood with Hg. The VGTP was significantly increased from 0.28 to 0.51 cmH2O/cm height. The fractional increase in the VGTP was similar to the fractional increase in heart weight. In five dogs extrapolation to zero heart weight gave an average VGTP of 0.14 cmH2O/cm height. We conclude that the lungs help support the heart in the head-up dog and that the VGTP is in part determined by the pressure distribution required for this support.

Animals↗
PubMed1984

Relation between efficacy of sodium cromoglycate and baseline lung function in exercise- and hyperventilation-induced asthma.

The protective effect of sodium cromoglycate (SCG) against exercise- and hyperventilation-induced asthma with respect to basal lung function was investigated in young asthmatics. The subjects performed standardized exercise or isocapnic hyperventilation challenge tests breathing cold dry air; in each case the effect of SCG was compared with that of a placebo in a double-blind fashion. With exercise as the challenge in 24 subjects, there was a strong positive correlation between the protective effect of SCG and the basal level of lung function. Using hyperventilation as the challenge in 11 subjects, there was no such correlation, but excluding two known placebo responders, there was a negative correlation between the protective effect of SCG and basal lung function. There findings suggest that exercise and hyperventilation operate differently in inducing asthma.

Adolescent↗
PubMed1983

Duration of action of sodium cromoglycate on exercise induced asthma: comparison of 2 formulations.

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.

Adolescent↗
PubMed1983

Refractory period following induced asthma: contributions of exercise and isocapnic hyperventilation.

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.

Adolescent↗
PubMed1983

Effect of negative ionisation of inspired air on the response of asthmatic children to exercise and inhaled histamine.

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.

Adolescent↗
PubMed1983

Heterogeneity in the response of asthmatic patients to pre-exercise treatment with cromolyn sodium.

The protective effect of pre-exercise treatment with cromolyn sodium (CS) on exercise-induced asthma (EIA) was investigated. Ten children and young adults each exercised for 6 min by cycling on a cycle ergometer while breathing cold dry air. Each subject performed 2 tests in which ventilation, heart rate, and gas exchange were closely matched; 15 min prior to each test, the patient inhaled either placebo or CS powder in a double-blind, randomized fashion. All subjects were found to be protected by CS, as manifested by a postexercise fall in FEV1 of 14 +/- 4% SE compared with the control postexercise fall of 39 +/- 5%. All 10 subjects had participated in a previous study (7), and we found that the 3 subjects who were not rendered refractory to EIA by a prior warm humid exercise test were only minimally protected by CS, whereas the 7 other patients who were rendered refractory to EIA, even by warm humid exercise, were greatly protected by CS. This finding suggests that there exists a consistent heterogeneity in the response of asthmatic patients to exercise, possibly related to the individual site of receptors or of airway hyperreactivity.

Adolescent↗
PubMed1983

Refractory period after hyperventilation-induced asthma.

Nine young asthmatic subjects undertook isocapnic hyperventilation while breathing air under different conditions. Each subject undertook 2 pairs of tests. Pair A consisted of 2 hyperventilation challenges performed while breathing cold (2.8 +/- 1.4 degrees C) dry (2.3 +/- 0.05 mg H2O/L) air. Pair B consisted of an initial warm (38.0 +/- 0.9 degrees C) saturated air challenge followed by a cold dry challenge. Tests were closely matched in terms of ventilation and respiratory heat loss in the cold dry tests. The subjects were rendered refractory by the first cold dry hyperventilation challenge, the fall in forced expiratory volume in one second (FEV1) after hyperventilation in the first test (delta FEV1 = 39 +/- 5%) being significantly greater than that after the second challenge of Pair A (delta FEV1 = 21 +/- 5%, p less than 0.005). In test Pair B, the warm humid hyperventilation challenge neither caused significant asthma (delta FEV1 6 +/- 3%) nor rendered the subjects refractory to the subsequent cold dry test (delta FEV1 38 +/- 4%). Because in a previous study it was shown that exercise while breathing warm humid air could induce a refractory period without itself causing asthma, we conclude that hyperventilation-induced asthma is not the same as exercise-induced asthma in most subjects.

Adolescent↗
PubMed1983

Flow-volume curves in infants with lung disease.

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.

Airway Resistance↗
PubMed1982

Differences between swimming and running as stimuli for exercise-induced asthma.

Thirteen children each exercised for 6 min by running on a treadmill and by tethered swimming, breathing air at room temperature and either 8% or 99% relative humidity continuously. Ventilation, gas exchange and heart rate were closely matched in all four tests in each child, with a mean oxygen consumption of 32.3 +/- 1.7 ml x min-1 x kg-1. The post-exercise fall in FEV1 expressed as a percentage of the baseline FEV1 (delta FEV1) was significantly greater after running compared with swimming breathing either humid or dry air. The delta FEV1 was also related to respiratory heat loss (RHL) calculated from measurements of inspired and expired gas temperature and humidity. At a standardised RHL, the difference between running and swimming was highly significant [delta FEV1 (%) +/- SE = 39 +/- 5 and 28 +/- 4 respectively, p less than 0.01]. These experiments suggest that the type of exercise influences the severity of exercise-induced asthma even under conditions of the same metabolic stress and respiratory heat loss.

Adolescent↗
PubMed1982

Lack of response to bronchodilator of airway obstruction after mechanical ventilation in the newborn.

Thoracic gas volume (TGV) and specific airway conductance (SGaw) were measured in 6 infants, 21-42 weeks of age, who had been mechanically ventilated during the neonatal period. SGaw was significantly decreased while TGV was normal. Administration of a nebulized beta 2-sympathomimetic stimulant did not improve lung function. It is concluded that inhalation of beta 2 stimulant drugs is not effective in improving airway obstruction in infants with postventilation-elevated airway resistance and that this is likely to be of structural origin.

Albuterol↗