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Biomedical subjects

S Godfrey

Publications and source records attributed to S Godfrey.

At least 163 records · Page 9Linked to original sources
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

Cardiac output measured by transthoracic impedance cardiography at rest, during exercise and at various lung volumes.

1. Cardiac output measured by transthoracic impedance cardiography has been compared with simultaneous measurements made by the indirect Fick CO2 rebreathing method in nine adults and 14 children. All were healthy normal volunteers. Sixty-six comparisons were made at rest and during steady exercise at work loads up to 100 W. 2. Impedance measurements of cardiac output were consistently higher than indirect Fick measurements of cardiac output, but after application of a correction factor related to packed cell volume there was close correlation between the results obtained by the two methods (r = 0.94). 3. The mean coefficient of variation of impedance measurements of cardiac output was 13% at rest and 5% during steady-state exercise. 4. Changes of lung volume due to breath holding or resulting from addition of an expiratory resistance did not affect the measurement of cardiac output by impedance. 5. Transthoracic impedance cardiography is a rapid, non-invasive technique for measurement of cardiac output. It requires very little active co-operation from the subject. The method would probably give reliable results for patients with respiratory illnesses such as acute asthma or bronchiolitis, during which changes of lung volume may be expected to occur.

Adult↗
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↗
PubMed1982

Determinants of forced expiratory flows in newborn infants.

Maximal flows at functional residual capacity (VmaxFRC) from partial expiratory flow-volume (PEFV) curves (achieved with rapid compression of the chest) were obtained on 11 healthy newborn babies. Mean VmaxFRC, size corrected by dividing absolute values by measured thoracic gas volume, was 1.90 TGV's/s. Specific upstream conductances were high, and the cross-sectional area of the flow-limiting segment was estimated to be approximately 0.30 cm2 in the three infants on whom recoil pressures at FRC were also measured. The cross-sectional area of the major bronchi in the neonate is approximately 0.26-0.30 cm2. PEFV curves were convex to the volume axis. Many of the neonates increased their flows while breathing a helium-oxygen gas mixture. These results suggest 1) size-corrected flows are higher in the neonate than in older children or adults; 2) the site of the flow-limiting segment at FRC during maximal expiratory maneuvers is in large proximal airways, similar to the adult; and 3) the relationship of airway size to parenchymal size may be similar in neonates and adults or, in fact, airways may be larger, relative to parenchyma, in neonates. These physiological data do not support the hypothesis, based on pathological studies, that peripheral airways are disproportionately smaller (when compared with central airways) in infants than in adults.

Airway Resistance↗
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↗
PubMed1981

Do exercise- and antigen-induced asthma utilize the same pathways? Antigen provocation in patients rendered refractory to exercise-induced asthma.

Twelve asthmatics (ages 8 to 33 yr) with proven exercise-induced asthma (EIA) and allergen-induced asthma (AIA) were investigated in an attempt to elucidate the pathways through which each type of attack develops. All patients were rendered refractory to EIA by repeated exercise at short intervals and were then immediately challenged by inhalation with an allergen known to evoke AIA. After an average of three runs all subjects were rendered refractory to EIA (post-exercise fall in FEV1 of 7 +/- 8% SEM compared with the control postexercise fall of 32 +/- 14%). In this refractory state six patients failed to respond to antigen challenge (6 +/- 4% SEM fall in FEV1 compared with the 30 +/- 3% fall in control study, p less than 0.001), suggesting a common pathway for EIA and AIA, such as the exhaustion of stored chemical mediators. Six other patients developed attacks of AIA while refractory to EIA, which were at least as severe as those in their control study (34 +/- 7% SEM fall in FEV1 compared with 29 +/- 3%). The fact that AIA could develop while EIA was blocked in this group requires an alternate pathway or mechanism for their AIA. The only significant difference between the AIA "blocked" and AIA "nonblocked" groups was a lower baseline level of lung function in all tests in the nonblocked group.

Adolescent↗
PubMed1981

Suppressor T-lymphocyte activity in wheezy children with and without treatment by hyposensitization.

The suppressor cell activity of peripheral blood lymphocytes was investigated in wheezy children by determining the ability of concanavalin A induced suppressor cells to inhibit a mitogen provoked proliferative response. The activity was compared with that of eighteen healthy controls. Of ten infants aged from 5 months to 4 1/2 years, with recurrent wheezy bronchitis, three had much reduced suppressor cell activity (2 s.d. or more below that of controls). Of twelve asthmatic children aged from 4 1/2 to 12 years, seven had much reduced suppressor cell activity. The remaining five asthmatic children with normal suppressor cell activity had all received hyposensitization therapy. We speculate that immune hyposensitization therapy might act by stimulating lymphocyte suppressor activity.

Aminophylline↗
PubMed1981

Relationship between the chest radiograph, regional lung function studies, exercise tolerance, and clinical condition in cystic fibrosis.

This study evaluated the accuracy of the interpretation of the chest film in delineating localised abnormalities of ventilation and perfusion, as well as the overall severity of airways obstruction, exercise tolerance, and clinical condition in children with cystic fibrosis. Radiographic findings in various regions of the chest film were compared with the functional values obtained with regional lung function tests which evaluated the arrival and disappearance of boluses of radioactive nitrogen given by inhalation and infusion. While the more severely affected areas on the chest radiograph were found to correlate with similar regions on the lung function tests, as did overall scores, errors occurred in some cases if the x-ray film alone was used as a judge of regional physiological derangement. In addition the degree of airways obstruction, the exercise tolerance on a cycle ergometer, and clinical grading, each correlated significantly with the radiographic score. We conclude that the chest radiograph is a good indicator of the overall severity of the lung disease and that it correlates well with exercise tolerance and clinical condition in cystic fibrosis.

Adolescent↗
PubMed1981

Relationship of exercise-induced asthma to clinical asthma in childhood.

Thirty-three asthmatics were followed up for a mean of 8 1/2 years in prospective study in order to observe the clinical course of the disease. The severity of asthma was graded according to the treatment each required to keep him in reasonable health. Regular exercise tests were performed so that a comparison could be made between the degree of exercise-induced asthma and the severity of the disease. In this group of severe perennial childhood asthmatics profound exercise-induced asthma was found to exist throughout the entire clinical spectrum of the disease with no appreciable difference until the patient became symptom-free. Exercise-induced asthma then disappeared only to return if clinical asthma recurred. This study showed that exercise-induced asthma is a sensitive indicator of clinical asthma but has no prognostic significance in the symptom-free patient.

Asthma↗
PubMed1981

Cardiovascular response during severe acute asthma and its treatment in children.

Heart rate, blood pressure, pulsus paradoxus, and cardiac output measured by means of transthoracic electrical impedance cardiography have been recorded in 29 children mean age 10 years +/- 2 SD during status asthmaticus. Changes were recorded over the first two hours of treatment during which all patients received oxygen, intravenous fluid, and hydrocortisone, and were randomly assigned to receive aminophylline, salbutamol, or both. Admission values showed significant correlation of pulsus paradoxus with PaCO2 (r = 0.66). Pulsus paradoxus was greater than 20 mmHg for all patients with PaCO2 above 5.5 kPa. Mean stroke volume and cardiac output were 89% and 131% of the resting convalescent values in the same children. Stroke volume cardiac output and heart rate did not correlate with peak expiratory flow rate or blood gas measurements. Aminophylline and salbutamol together were associated with significantly greater increase in PEF than aminophylline alone (P less than 0.05). Nebulised salbutamol was just as effective as intravenous salbutamol. Heart rate and systolic blood pressure declined significantly after nebulised salbutamol and aminophylline, but not after intravenous salbutamol and aminophylline. Stroke volume and cardiac output did not change significantly in any treatment group.

Acute Disease↗
PubMed1980

The relative merits of cromolyn sodium and high-dose theophylline therapy in childhood asthma.

The use of cromolyn sodium (SCG) and high-dose theophylline (HDT) in the treatment of chronic perennial asthma in children is reviewed. It is noted that the regimens are only suitable for children with persistent symptoms uncontrolled by simpler forms of treatment. The methods of administration and dosage based on pharmacologic data are considered, and the potential importance of long-acting theophylline and nebulized cromolyn preparations is noted. Short-term studies have confirmed the efficacy of both drugs, and a comparative study showed little difference between them. Long-term studies of SCG have demonstrated its value to some 66% of children without serious side effects. No formal long-term studies have been carried out on HDT. Side effects from theophylline can often be eliminated by careful control of blood levels. From published evidence, neither SCG nor HDT is effective in steroid-dependent asthmatic children, and they contribute little, if anything, to management in such cases. The difference in cost of the drugs is small when all factors are considered, and either regimen is justified by the saving in medical expenses when used for carefully selected patients.

Asthma↗