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Biomedical subjects

A S Rebuck

Publications and source records attributed to A S Rebuck.

At least 145 records · Page 8Linked to original sources
PubMed1976

Ventilatory response to carbon dioxide in young athletes: a family study.

Ventilatory response to carbon dioxide (deltaVE/deltaPCO2) was measured in 23 teenage swimmers chosen by their coach for their potential for future athletic success. Siblings and parents of these swimmers were also studied. We found a strong relation between siblings' de;taVE/DELTAPCO2, whether or not they were swimmers (r=0.71, P less than 0.01). A weaker relationship was found between mother's and children's deltaVE/DELTAPCO2 (r==0.39, P less than 0.01). No association was found between swimming training and deltaVE/deltaPCO2. One swimmer 12 years of age had an extremely low deltaVE/PCO2 (0.42 liter per min per mm Hg) She was the only swimmer among these 23 potential champions to achieve international success in endurance events in the 2 years after the study. We concluded that family factors are important determinants of a subject's deltaVE/PCO2 and suggest that measurement of this aspect of chemical drive to breathing in young athletes may help identify those most likely to succeed in endurance events.

Adolescent↗
PubMed1976

Ear oximetry: accuracy and practicability in the assessment of arterial oxygenation.

The accuracy of three ear oximeters (Waters XP-350, Waters 0-1100, Hewlett-Packard 47201A) was evaluated on 52 subjects during acute progressive and steady-state hypoxia. Ear oximeter readings were compared with measured arterial saturation (SAO2) in arterial or "arterialized" capillary blood samples. Hewlett-Packard (HP) 47201A ear oximeter readings most closely approximated measured Sao2 (y=0.99x - 1.52, r=0.97), although both the HP 47201A and Waters 0-1100 oximeters provided similarly accurate estimates of SAO2 once the characteristics of the individual oximeters were known (standard error of estimate; 2.52 and 2.98 per cent SAO2, respectively). The HP 47201A ear oximeter was relatively insensitive to changes in ear-piece position and differences in skin pigmentation, and offered the added advantages of comfort, simplicity of operation, and stability of characteristics.

Arteries↗
PubMed1976

Pulmonary gas exchange in acute mountain sickness.

The severity of acute mountain sickness (AMS) was investigated in healthy volunteers, airlifted to high altitude (5,360 m). Blood gases were measured at 2,990 m and 5,360 m. Symptoms of AMS were found in all subjects, but ranged from malaise to vomiting with intractable headache. The clinical severity of AMS was directly related to the arterial PCO2 and inversely to pH, but unrelated to the PO2 on arrival at high altitude. However, PO2 fell and was lowest 48 h after arrival at high altitude in those subjects with the most severe AMS. These were the only subjects to show an increase in the alveolar-arterial PO2 difference and in the venous admixture ratio during the first 48 h. These abnormalities in gas exchange, which developed in the subjects with the most marked cerebral symptoms, suggest that the manifestations of cerebral and pulmonary dysfunction at altitude develop simultaneously, a finding that suggests coexisting cerebral and pulmonary edema.

Acute Disease↗
PubMed1975

Pulsus paradoxus in asthmatic children.

Pulsus paradoxus is a useful physical sign in the assessment of the severity of asthma in adults. Whether this is also true for asthmatic children was determined by measuring respiratory fluctuations in systolic blood pressure during attacks of asthma in 24 children. A decrease in systolic pressure during inspiration exceeding 15 mm Hg was found only when the 1-second forced expiratory volume was less tha 60 percent of the predicted value. There was a highly significant (P smaller than 0.001) correlation between the degree of pulsus paradoxus and the severity of airway obstruction. In nonasthmatic children the systolic pressure was found to fluctuate by as much as 7 mm Hg during the respiratory cycle. It is concluded that, as in adults, the presence of pulsus paradoxus (larger than or equal to 15 mm Hg) in children indicates that their asthma is very severe.

Adolescent↗
PubMed1975

The effect of disodium cromoglycate (DSCG) on the levels of albumin and the immunoglobulins IgA, IgG, IgM and IgE in sputum.

Sputum samples from control subjects with cardiac disease and from patients with asthma were assayed for albumin content and immunoglobulins IgA, IgG, IgM and IgE. The asthmatics were divided into three groups: one group had received disodium cromoglycate (DSCG) for at least 48 hr prior to sampling, another group was sampled daily after commencing DSCG therapy and the third group were not taking DSCG. Albumin and immunoglobulins accounted for approximately 8% of the total sputum proteins in each of the four groups of subjects. There was no significant difference in the mean sputum levels of albumin or the immunoglobulins, when expressed as a percentage of total sputum proteins, between the subjects in each group. However, the ratios of IgA/albumin and IgA/IgG in the asthmatic group receiving DSCG were significantly lower than the corresponding ratios in sputa from both asthmatics and control subjects with cardiac disease. The sputum IgE levels tended to be higher in the asthmatics than in the control group, but DSCG therapy had little effect upon sputum IgE levels.

Albumins↗
PubMed1975

Ventilatory effects of hypoxia and their dependence on PCO2.

In 11 healthy subjects the effect of progressive hypoxia on pulmonary ventilation at various alveolar carbon dioxide pressures was studied. A rebreathing technique was used to produce hypoxia, CO2 was held constant and oxygen saturation was taken as the independent variable. We found a linear relationship between ventilation and falls in oxygen saturation when Pco2 was held at the resting mixed venous, end-tidal, or any intermediate level. Within this range of Pco2, a family of ventilation-So2 response curves was obtained for each subject. The effect of altering the isocapnic level was to change the slope and position of the ventilation-So2 response curve, the amount by which the slope changed being related to the slope for that subject at their mixed venous Pco2.

Adult↗
PubMed1975

Effect of resistive loading on ventilatory response to hypoxia.

Ventilatory responses to hypoxia, with and without an inspiratory resistive load, were measured in eight normal subjects, using a rebreathing technique. During the studies, the end-tidal P-CO2 was kept constant at mixed venous level (Pv-CO2) by drawing expired gas through a variable CO2-absorbing bypass. The initial bag O2 concentration was 24% and rebreathing was continued until the O2 concentration in the bag fell to 6% or the subject's arterial oxygen saturation (Sa-O2), monitored continuously by ear oximetry, fell to 70%. Studies with and without the load were performed in a formally randomized order for each subject. Linear regressions for rise in ventilation against fall in Sa-O2 were calculated. The range of unloaded responses was 0.78-3.59 1/min per 1% fall in Sa-O2 and loaded responses 0.37-1.68 1/min per 1% fall in Sa-O2. In each subject, the slope of the response curve during loading fell by an almost constant fraction of the unloaded response, such that the ratio of loaded to unloaded slope in all subjects ranged from 0.41 to 0.48. However, the extrapolated intercept of the response curve on the Sa-O2 axis did not alter significantly indicating that the P-CO2 did not alter between experiments. These results suggest that the change in ventilatory response to hypoxia during inspiratory resistive loading is related to the mechanical load applied, with the loaded slope being directly proportional to the unloaded one.

Adult↗
PubMed1975

Effect of elastic loading on ventilatory response to hypoxia in conscious man.

Ventilatory responses to isocapnic hypoxia, with and without an inspiratory elastic load (12.1 cmH2O/l), were measured in seven healthy subjects using a rebreathing technique. During each experiment, the end-tidal PCO2 was held constant using a variable-speed pump to draw gas from the rebreathing bag through a CO2 absorbing bypass. Studies with and without the load were performed in a formally randomized order for each subject. Linear regressions for rise in ventilation against fall in SaO2 were calculated. The range of unloaded responses was 0.74-1.38 1/min per 1% fall in SaO2 and loaded responses 0.71-1.56 1/min per 1% fall in SaO2. Elastic loading did not significantly alter the ventilatory response to progressive hypoxia (P greater than 0.2). In all subjects there was, however, a change in breathing pattern during loading, whereby increments in ventilation were attained by smaller tidal volumes and higher frequencies than in the control experiments. These results support the hypothesis previously proposed in our studies of resistive loading during progressive hypoxia, that a similar control pathway appears to be involved in response to the application of loads to breathing, whether ventilation is stimulated by hypoxia or hypercapnia.

Adult↗
PubMed1974

Symposium on allergic lung disease. I. The clinical picture of asthma.

Life-threatening asthma may be judged to be present in patients who, in the presence of a low FEV(1) are too dyspneic to speak, have altered consciousness or unequivocal cyanosis. Other physical signs which indicate airway obstruction of grave severity are pulsus paradoxus, gross thoracic overinflation and electrocardiographic evidence of pulmonary hypertension. A rise in the arterial CO(2) tension, the presence of pneumothorax or pneumomediastinum, and an FEV(1) less than 1 litre and vital capacity less than 0.5 litre, failing to increase immediately after inhalation of a bronchodilator, are also features which demand urgent and intensive therapy.Corticosteroids in large doses should be administered whenever a life-threatening situation is recognized. Systemic steroids should be stopped only when the danger phase, as indicated by the criteria given above, has been reversed. At all stages of therapy regular inhalations of a sympathomimetic bronchodilator should be maintained. Oral steroid therapy should be continued until maximum ventilatory function has been attained; only then should dose reduction be attempted.

Adrenal Cortex Hormones↗