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Biomedical subjects

S Godfrey

Publications and source records attributed to S Godfrey.

At least 307 records · Page 17Linked to original sources
PubMed1969

The effect of CO2 on ventilation and breath-holding during exercise and while breathing through an added resistance.

1. Ventilation was measured while subjects were made to rebreathe from a bag containing CO(2) and O(2) in order to expose them to a steadily rising CO(2) tension (P(CO2)). The object of the experiments was to determine the effect of a variety of stimuli upon the increase in ventilation and fall in breath-holding time which occurs in response to the rising P(CO2).2. Steady-state exercise at 200 kg.m/min resulted in a small fall in the slope of the ventilation-CO(2) response curve (S(V)) and a small, though not statistically significant, fall in the P(CO2) at which ventilation would be zero by extrapolation (B(V)). There was a marked fall in the slope of the breath-holding-CO(2) response curve (S(BH)) and an increase in the P(CO2) at which breath-holding time became zero by extrapolation (B(BH)).3. These results have been interpreted with the aid of a model of the control of breath-holding and it is suggested that there is no change in CO(2) sensitivity on exercise, either during rebreathing or breath-holding.4. An increase in the resistance to breathing caused a marked reduction in S(V) and B(V), but no change in the breath-holding-CO(2) response curve. These findings suggest that the flattening of the ventilation-CO(2) response curve is mechanical in origin and acute airway obstruction produces no change in CO(2) sensitivity.5. On the basis of these results, we suggest that more information about CO(2) sensitivity can be obtained by a combination of ventilation and breath-holding-CO(2) response curves.

Apnea↗
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↗