Biomedical subjects

D J Gavaghan

Publications and source records attributed to D J Gavaghan.

22 records · Page 2Linked to original sources

PubMed1996

Effects and interactions of myocardial ischaemia and alterations in circulating blood volume on canine left ventricular diastolic function.

We have determined the effects of alterations in preload on ischaemia-induced diastolic dysfunction in anaesthetized beagles instrumented to measure left ventricular pressure and regional dimensions. Low-flow regional ischaemia decreased peak lengthening rates in ischaemic (mean -26 (SEM 6) mm s-1, P < 0.01) and non-ischaemic (-8.6 (3.4) mm s-1, P < 0.05) myocardium. Peak lengthening rates and the time constant of iso-volumic relaxation (tau) were not affected by alterations in preload. Absolute values of tau failed to distinguish between ischaemia and control. The ischaemia-induced decrease in peak negative dP/dt was preload dependent and caused mainly by a concomitant decrease in peak left ventricular pressure. We conclude that indices derived from segmental lengthening are sensitive to ischaemia and insensitive to preload, in contrast with indices derived from left ventricular pressure. It remains to be determined if monitoring of early segmental lengthening will improve detection and assessment of perioperative myocardial ischaemia.

Animals↗

PubMed1995

A mathematical evaluation of the alveolar amplitude response technique.

The underlying mathematical model of the forcing sinewave alveolar amplitude response technique (AART) for measuring lung volume and perfusion is investigated. Making use of numerical techniques, we are able to to evaluate the effects of several assumptions which are implicit in the original technique introduced by Zwart et al., J. Appl. Physiol. 41: 419-429, 1976, and development by several other workers. In particular we are able to show that AART is appropriate for gases of a wider range of solubilities than originally suggested, allowing it to be used with agents, such as nitrous oxide, which are more clinically acceptable. In addition, we are able to show that the effects of recirculation times are likely to be very small using figures for standard man. A least squares parameter recovery technique proves to be very robust to simulated measurement errors and is used to quantify the effects of the modelling assumptions.

Humans↗

PubMed1994

Measurement of dead-space in a model lung using an oscillating inspired argon signal.

In a model lung, airways dead-space can be accurately measured using a forced inspired oscillating argon signal, which varies sinusoidally about a mean concentration of 6% v/v with an amplitude of +/- 4% v/v. With sinusoid forcing periods longer than 120 seconds, and at a breathing rate of 13.4 breaths minute-1, the mean airways dead-space can be measured with a standard error of less than 5%. Sinusoid forcing periods shorter than 120 s provided inaccurate estimates of dead-space and so should not be used with this technique.

Argon↗

PubMed1990

Oral morphine in cancer pain: influences on morphine and metabolite concentration.

One hundred fifty-one patients with chronic cancer pain were studied during chronic treatment with oral morphine. Plasma concentrations of morphine and metabolites (M3G and M6G) were measured. The ratio of plasma morphine to metabolites was not affected by dose. Generalized linear interactive modeling analysis using morphine dose, age, sex, renal and hepatic dysfunction, and concomitant medication as explanatory variables accounted for 70% of the variance in plasma concentrations of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). Increasing morphine dose was a significant factor for increased plasma concentrations of morphine, M3G, and M6G. Other significant factors were: age greater than 70 years (increased M3G and M6G plasma concentrations), plasma creatinine greater than 150 mumol/L (increased M3G and M6G plasma concentrations), male sex (decreased morphine and M6G plasma concentrations), raised creatinine plus coadministration of tricyclic antidepressants (increased M3G plasma concentrations), ranitidine (increased morphine plasma concentrations), and raised creatinine plus coadministration of ranitidine (increased M6G plasma concentrations).

Adult↗