Biomedical subjects

P R Douglas

Publications and source records attributed to P R Douglas.

4 recordsLinked to original sources

PubMed1990

Partial cholecystectomy.

An alternative to cholecystostomy and standard cholecystectomy for 'difficult' gall bladders has been described previously. The procedure, partial cholecystectomy, involves leaving in situ part or all of the wall of the gall bladder which lies directly in relation to the liver and/or structures in the porta hepatis. Eleven such procedures have been performed over a 5 year period, and the common indication in all was severe inflammation or fibrosis in the region of Calot's triangle. One patient developed a self-limiting postoperative bile leak. One patient has formed bile duct stones and appears to have oriental cholangiohepatitis. In the remainder of the patients, there has been no recurrence of biliary tract symptoms. The procedure is definitive and safe, and may usually be performed when cholecystostomy would have been undertaken.

Aged↗

PubMed1984

Liquid ventilation: effects on pulmonary function in distressed meconium-stained lambs.

Seven lambs (0.93 term gestation) were delivered by cesarean section with evidence of meconium in the amniotic fluid, meconium staining, and respiratory distress. The initial arterial blood gas and acid-base status indicated severe hypoxemia and acidosis. Three of these lambs developed pneumothoraces and died on control gas ventilation with positive end expiratory pressure. During the control period (90 min) with ventilatory support, there were no significant alterations in mean arterial oxygen tension (PaO2) and alveolar-arterial oxygen gradient (A-aDO2). The initial hypercarbia and acidosis were effectively controlled and corrected using mechanical ventilation and bicarbonate infusion. Fifteen min after the onset of fluorocarbon ventilation mean PaO2 significantly increased and A-aDo2 decreased. After 90 min of fluorocarbon ventilation, lambs were returned to gas ventilation. During this recovery period, PaO2 and A-aDo2 remained significantly improved compared with control gas values. Dynamic lung compliance increased, alveolar and peak tracheal pressure decreased and inspiratory elastic work of breathing decreased during liquid ventilation.

Animals↗

PubMed1983

The effects of liquid ventilation on cardiopulmonary function in preterm lambs.

The effects of fluorocarbon ventilation on cardiopulmonary function were studied in 8 preterm lambs, 132-136 days gestation. After mechanical ventilation with 100% oxygen (control period), the lambs were ventilated with fluorocarbon (PIO2 = 622 torr). The liquid was then removed from their lungs and gas ventilation resumed (recovery period). During normothermic liquid breathing the alveolar-arterial O2 gradient (A-a DO2) decreased (P less than 0.01) from control by 154 torr and remained decreased (P less than 0.05) by 85 torr during recovery. Dynamic lung compliance (CL) increased 50% (P less than 0.05); PaO2 increased 50% (P less than 0.05); and PaCO2 decreased 29% (P less than 0.01) as compared to control values. The change in A-a DO2 and PaO2 before and after liquid ventilation was correlated (r = 0.79 and P less than 0.01) with control CL. There was a gradual decrease (P less than 0.01) in mean arterial pressure from 62 +/- 5.4 torr (control) to 53,1 +/- 9,3 torr (recovery); however, there were no significant alterations in mean central venous pressure, heart rate, or mean electrical axis.

Animals↗

PubMed1978

Coding of information about tactile stimuli by neurones of the cuneate nucleus.

1. The responses of cuneate neurones to controlled tactile stimulation of the foot pads were examined in unanaesthetized, decerebrate cats. The neurones were divided into three functional classes; one sensitive to steady tactile stimuli, and two dynamically sensitive classes which could be readily differentiated by their responsiveness to cutaneous vibration. Each class appeared to receive an exclusive input from only one of the three known groups of tactile receptors associated with the foot pads, namely the Pacinian corpuscles, the Merkel endings and the intradermal, encapsulated endings known as Krause or Meissner corpuscles. 2. Cuneate neurones responsive to steady indentation of the skin displayed approximately linear or sigmoidal stimulus-response relations over indentation ranges up to approximately 1.5--2 mm. Response variability at a fixed stimulus intensity was relatively low and showed little systematic change over the full range of the stimulus-response curves. 3. One class of dynamically sensitive cuneate neurones responded to cutaneous vibration over a range of approximately 5-80 Hz with maximal responsiveness around 30 Hz. The other class, the Pacinian neurones, responded over a range of approximately 80- greater than 600 Hz with maximal responsiveness at 200-400 Hz. The thresholds and combined band width of vibratory sensitivity of these populations were comparable with known subjective thresholds and range of cutaneous vibratory sensibility. 4. Responses of cuneate neurones were phase-locked to the vibratory stimulus suggesting that information about vibration frequency could be coded by the patterns of impulse activity. Quantitative measures indicated that maximal phase-locking occurred in responses to vibration frequencies of 10-50 Hz with a progressive decline at higher frequencies. Above 400 Hz, impulse activity occurred almost randomly throughout the vibratory stimulus cycle and therefore carried little further signal of vibratory frequency. The decline, with increasing frequency, in the ability of cuneate neurones to signal information about vibratory frequency parallels the known subjective capacities for frequency discrimination. 5. A switch-over occurred at approximately 80 Hz in the population of cuneate neurones able to provide the more reliable signal of vibratory frequency; above 80 Hz, the Pacinian neurones; below 80 Hz, the neurones receiving intradermal, rapidly adapting receptor input from the pads. 6. The observed properties of cuneate neurones are compatible with a role in signalling information which could contribute to subjective tactile abilities.

Action Potentials↗