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Biomedical subjects

P R Fletcher

Publications and source records attributed to P R Fletcher.

At least 37 records · Page 2Linked to original sources
PubMed1986

Frequency dependence of dead space during high-frequency ventilation in dogs.

A rotary valve ventilator, designed to allow the direct measurement of expired gas volume and composition, was used to maintain gas exchange in anesthetized, paralyzed, mongrel dogs at ventilatory frequencies up to 20 Hz. A total of eleven studies were carried out on four animals. Determinations of the minute ventilation required to maintain a normal steady-state PCO2, together with the FECO2 and arterial PO2, PCO2, and pH, were made at a number of frequencies. The results so obtained were used to calculate the Bohr (physiological) dead space. Dead space remained approximately constant at close to the value measured during spontaneous ventilation for each individual dog in the range of ventilatory frequencies from below 1 to around 5 Hz, but decreased with increasing frequency above 5 Hz. The calculated physiological dead space at 15 Hz was about half of the value at normal respiratory frequencies. These findings in dogs, obtained using a ventilator system which allows very accurate determinations of expired gas volume and content, are consistent with published results for this species from other laboratories. They contrast with our earlier findings in rabbits that dead space remains constant with increasing frequency, suggesting that the effects of high-frequency ventilation on CO2 transport are species-dependent.

Animals↗
PubMed1982

A new ventilator for physiologic studies during high-frequency ventilation.

Research in the field of high frequency ventilation (HFV) has been hampered by the difficulty of collecting and analyzing expired gas, uncontaminated by gas of inspiratory composition, at ventilatory frequencies in the relevant range. A new mechanical ventilator is described, which has been designed to facilitate studies on the respiratory physiology of small animals during HFV. Ventilation is controlled by a single rotary valve, which alternately switches the airway to an approximately constant-flow gas source during inspiration, and to gas measurement and analysis apparatus during expiration, which takes place passively. Theoretical and experimental studies, using the techniques of mechanical and mathematical modelling, are used to measure the performance of the ventilator and to demonstrate that it allows the quantitative collection of expired gas during ventilation at rates up to at least 20 Hz. The advantages and limitations of this approach are discussed.

Animals↗
PubMed1982

Constancy of physiological dead space during high-frequency ventilation.

A ventilator, specially designed to allow the direct measurement of expired gas volume and composition, was used to maintain gas exchange in anesthetized, paralyzed, New Zealand White rabbits at ventilatory frequencies up to 22 Hz. A total of eleven studies were carried out on seven animals. Determinations of the minute ventilation required to maintain a normal steady-state PCO2, together with the FECO2 and arterial PO2, PCO2, and pH, were made at a number of frequencies. The results so obtained were used to calculate the physiological dead space. It was found that this value remained remarkably constant for each individual rabbit over a range of ventilatory frequencies from 1 to 22 Hz. Our findings in rabbits are in contrast to those of other workers (in dogs) that adequate gas exchange can be maintained at high ventilatory frequencies with the use of tidal volumes much smaller than the volume of anatomical dead space.

Animals↗
PubMed1978

Acute hiatal hernia with oesophageal perforation following Heller's operation.

The unusual complication of acute hiatal hernia with oesophageal rupture following transthoracic oesophagomyotomy is described in 2 cases. Inadvertent disruption and widening of the oesophageal hiatus at the time of surgery coupled with increased intragastric and intra-abdominal pressure were the probable causes. The hiatus should be carefully inspected on completion of the myotomy and anatomical restoration performed if necessary in order to avoid this complication. Urgent surgical intervention, gastric fundal serosal patch repair and intravenous alimentation proved successful in the management of these patients.

Acute Disease↗