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Biomedical subjects

A L Morris

Publications and source records attributed to A L Morris.

68 records · Page 4Linked to original sources
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Comparison of haemodynamic responses to positive-end-expiratory ventilation and pericardial effusion in dogs.

1. The haemodynamic responses to progressive increments in positive end-expiratory pressure ventilation (PEEP) were assessed in dogs in the presence and absence of pericardial effusion (2.2 ml saline/kg). 2. Increasing levels of PEEP (3, 4, 8, 16 cm H2O) were associated with increases in right atrial, left atrial, pericardial and pulmonary artery diastolic pressure; increases in pulmonary vascular resistance; decreases in aortic blood pressure; and decreases in cardiac index or stroke index. 3. Pericardial effusion that was associated with an increase in pericardial pressure of 3 mmHg was not associated with significant changes in aortic blood pressure or stroke index. In contrast 8 cm PEEP was associated with significant decreases in both these haemodynamic variables yet pericardial pressure increased only 2.2 mmHg. 4. For these levels of PEEP and pericardial effusion, the same haemodynamic response to PEEP was observed regardless of the presence or the absence of pericardial effusion. 5. Similar changes in aortic blood pressure and stroke index despite different pericardial pressures is reflected by significantly different intercepts in the linear model relating these haemodynamic variables to pericardial pressure in the presence and absence of pericardial effusion. 6. The results suggest that these haemodynamic consequences of PEEP are primarily a function of pulmonary hyperinflation and are less dependent on increases in extracardiac pressure per se.

Animals↗
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Coronary angiography and bypass surgery in Manitoba and the United States: a first comparison.

OBJECTIVE: To compare the appropriateness of use of coronary angiography (CA) and bypass surgery (CABS) in the early 1980s in one Canadian hospital and several American hospitals using explicit case-based criteria. Procedure rates were much lower in Canada during this period. SUBJECTS: Canadian subjects, 502 Manitoba residents undergoing CA at one hospital in 1981-82 were tracked forward to determine whether and when they underwent CABS. CA comparisons were made with 351 Canadian patients aged 55 years or older; 1677 American CA patients aged 65 years or older and were drawn in 1981 from three hospitals. Two hundred and forty-five patients undergoing CABS within 12 months of CA made up the Canadian sample. American CABS patients were sampled from three hospitals during 1979-82. Manitoba patients assigned to medical treatment after CA were also appraised. METHODS: Criteria were derived by an American panel of clinicians following a Delphi process; indications were rated appropriate, equivocal and inappropriate. A trained abstractor reviewed charts and assigned ratings. Results of exercise electrocardiograms were not available in the Manitoba data set, hence sensitivity analyses were performed to determine how differing proportions of positive exercise electrocardiograms might affect the Manitoba results. RESULTS: Even assuming only 50% of treadmill tests were positive in the Manitoba sample, the proportion of inappropriate CA was lower in Manitoba than for the American hospitals: 9% versus 15 to 18%. For CABS, only one of the three comparison American hospitals approached the Manitoba hospital level of appropriateness. CONCLUSIONS: In the early 1980s, there was more appropriate use of CA and CABS in a Manitoba hospital compared with several American hospitals. Many Canadian patients undergoing CA and treated medically met American indications for appropriate use of CABS. Whether this represents underprovision of necessary care remains uncertain.

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