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Biomedical subjects

M K Sykes

Publications and source records attributed to M K Sykes.

At least 19 recordsLinked to original sources
PubMed1992

Effect of ventilation with positive end-expiratory pressure on the development of lung damage in experimental acid aspiration pneumonia in the rabbit.

Sixteen anaesthetized rabbits were subjected to tracheostomy and lung damage produced by the instillation of 4.5 ml/kg hydrochloric acid (pH 1.5) into the trachea. Half of the animals were ventilated with a positive end-expiratory pressure (PEEP) of 3 cmH2O and half with a PEEP of 10 cmH2O for 5 h, the mean airway pressure being kept at 12 cmH2O by adjustment of the end-inspiratory pause time. Pressure-volume curves were recorded every hour. Although the arterial PO2 values and compliance above the inflection point on the pressure-volume curve were greater in the group submitted to 10 cmH2O PEEP, there were no significant differences between the groups in terms of survival and histological findings.

Animals↗
PubMed1992

In vitro performance test system for pulse oximeters.

An in vitro system was developed capable of testing the accuracy and reproducibility of pulse oximeter readings. The pulse oximeter probe receives signals through a pulsating blood cuvette. The development of the design of the cuvette is described. Using the final design (or 'model finger'), a comparison is made between readings from a Datex Satlite pulse oximeter (SpO2) and saturation values obtained by use of a multi-wavelength bench oximeter (SaO2). Linear regression analysis of the data gives SpO2 = 0.88 SaO2 + 11.2 (r = 0.979, p < 0.001).

Fingers↗
PubMed1992

Response of 10 pulse oximeters to an in vitro test system.

Pulse oximeters are often used in situations in which severe hypoxaemia may occur. We have developed an in vitro system to test the accuracy of pulse oximeter calibration. The probe of 10 different oximeters was attached to a model finger in an in vitro blood circuit, and pulse oximeter readings (SpO2) were compared with multi-wavelength in vitro oximeter readings (SO2) over a range of SO2 values from 50 to 100%. The oximeters tested varied widely in their accuracy and linearity. We conclude that the system can test the accuracy, reproducibility and linearity of response of pulse oximeter readings at low oxyhaemoglobin saturations.

Calibration↗
PubMed1992

An evaluation of the Brüel and Kjaer monitor 1304.

A laboratory evaluation was performed on the Brüel and Kjaer multigas monitor 1304, incorporating a pulse oximeter. The instrument was tested for accuracy, stability, response and delay times, frequency response and the effects of water vapour, alcohol, cyclopropane and sevoflurane. The instrument's performance was found to be within or very close to the manufacturer's specifications for accuracy, stability and response and delay times. It was unaffected by water vapour and alcohol and the effect of cyclopropane on the vapour channel was lower than has been reported for other analysers. The response to sevoflurane was of the same order as that of the other vapours. A 90% response to square wave changes of gas composition was maintained up to 60 breaths.min-1 for CO2, O2, and N2O and up to 40 breaths.min-1 for the vapours when the nafion sampling tube was used.

Anesthesia, Inhalation↗
PubMed1991

Tracheal tube resistance and airway and alveolar pressures during mechanical ventilation in the neonate.

The relationship between peak airway pressure, alveolar pressure and respiratory frequency was calculated for the range of compliances and airway resistances which might be encountered during mechanical ventilation of a 3-kg neonate. The pressure/flow relationships of 2.5, 3.0, 3.5 and 4-mm tracheal tubes were determined at a series of flows from 0.5 to 4 litres/minute. Peak airway and alveolar pressures were then measured at various frequencies and inspiratory:expiratory ratios with the tubes incorporated in a model lung. Large differences between peak airway and alveolar pressures developed when frequency was increased or inspiratory time decreased; the differences were greatest with the smaller tubes. Shortening expiratory time by increasing the frequency or altering the inspiratory:expiratory ratio resulted in increased end-expiratory pressure because of incomplete emptying of the lung.

Airway Resistance↗
PubMed1979

Preservation of the hypoxic pulmonary vasoconstrictor mechanism during methoxyflurane anaesthesia in the dog.

The effect of methoxyflurane on the hypoxic pulmonary vasoconstrictor response in the dog lung was assessed by measuring the redistribution of pulmonary blood flow in response to two levels of unilateral alveolar hypoxia. Methoxyflurane 0.5% had no significant effect on the redistribution of blood flow resulting from the unilateral administration of oxygen 7% or nitrogen and there were no significant differences in PaO2 between the measurements made during unilateral hypoxia with methoxyflurane and those made during unilateral hypoxia in the control periods.

Anesthesia, Inhalation↗
PubMed1979

Depression of hypoxic pulmonary vasoconstriction in the dog by dopamine and isoprenaline.

The effects of dopamine and isoprenaline on the pulmonary vasoconstrictor response to alveolar hypoxia were assessed by measuring the redistribution of blood flow between the lungs in response to unilateral hypoxia. Dose rates of dopamine 25 micrograms kg-1 min-1 and isoprenaline 0.25 micrograms kg-1 min-1 (which produced equal increments in thecontractile force of the heart in dogs) produced a similar degree of depression of they hypoxic vasoconstrictor response, whereas dopamine 2.5 micrograms kg-1 min-1 had little effect on the response PaO2 during unilateral hypoxia was inversely related to the blood flow through the hypoxic lung.

Animals↗
PubMed1979

Effects of heparin and protamine on left ventricular performance in the dog.

The effects of protamine on left ventricular (LV) function were measured under conditions of controlled heart rate and proximal aortic pressure in eight anaesthetized, heparinised dogs. Protamine 3 mg.kg-1 produced a 21% decrease in LV dP/dt max, a 43% decrease in cardiac output, a 47% decrease in stroke work and decreases in systolic and diastolic pressures (-16%, -19% respectively). Protamine 6 mg.kg-1 resulted in a 17% decrease in LV dP/dt max, a 26% decrease in cardiac output, a 50% decrease in LV stroke work and 25 and 30% decreases in systolic and diastolic pressures. These results show that an impairment of LV function plays an important part in the circulatory depression produced by protamine.

Animals↗
PubMed1979

The nature and incidence of complications of peripheral arterial puncture.

Follow-up of the sites of 839 peripheral arterial punctures has confirmed the technique as safe and free from major sequelae. Minor complications, mainly bruising and tenderness, occurred at 39% of sites; this incidence is much less than that previously reported following short-term arterial cannulation. At only 2% of sites was there any significant pain or tenderness. There was a small incidence of pulse diminution particularly at the radial site but no case of arterial occlusion. The use of a smaller needle (23 s.w.g.) significantly reduced the overall incidence of complications.

Arteries↗
PubMed1979

Effect of orciprenaline on hypoxic pulmonary vasoconstriction in dogs.

The effect of orciprenaline on hypoxic pulmonary vasoconstriction and arterial oxygen tension (PaO2) was studied in 8 dogs by measuring the redistribution of blood flow in response to unilateral alveolar hypoxia. The distribution of blood flow was recorded continuously by measuring the radioactivity of the mixed expired gas from each lung during the continuous intravenous infusion of xenon-133. The hypoxic vasoconstrictor response was significantly depressed by an infusion of 1.0 micrograms/kg/min of orciprenaline but not by a dose of 0.1 micrograms/kg/min. PaO2 during unilateral hypoxia was significantly lower during the infusion of the high dose of orciprenaline than it was in the control periods before or after the infusion. A bolus dose of 0.5 mg significantly increased blood flow to a lung with established hypoxic vasoconstriction and also caused a significant reduction in PaO2. Since these effects were produced in the absence of airway pressure or pulmonary vascular pressure changes, it is concluded that orciprenaline may depress the hypoxic pulmonary vasoconstrictor response in dogs.

Animals↗
PubMed1978

Preservation of the pulmonary vasoconstrictor response to alveolar hypoxia during the administration of halothane to dogs.

The action of halothane on the pulmonary vasoconstrictor response to unilateral alveolar hypoxia was studied in two groups of dogs. In the first group the redistribution of blood flow between the two lungs was studied with a radioactive isotope method, which provided intermittent measurements, whilst in the second group the distribution of blood flow was observed continuously. In both groups there was no significant alteration of the hypoxic vasoconstrictor response with inspired halothane concentrations varying from 0.5 to 1.5%.

Animals↗