Biomedical subjects

K M McRae

Publications and source records attributed to K M McRae.

5 recordsLinked to original sources

PubMed2000

Pulmonary transplantation.

Anesthetic technique for pulmonary transplantation varies with recipient's underlying lung disease, procedure performed and regional practice. The pulmonary allograft is vulnerable to mechanical and biochemical injury throughout the harvesting, preservation and engraftment procedures. Mechanisms of allograft injury are reviewed, with suggestions for incorporation of strategies to minimize injury into clinical practice. Particular emphasis is placed on the use of nitric oxide for treatment of reperfusion injury.

Journal Article↗

PubMed1995

Volumetric capnography in children. Influence of growth on the alveolar plateau slope.

BACKGROUND: Lung growth in children is associated with dramatic increases in the number and surface area of alveolated airways. Modelling studies have shown the slope of the alveolar plateau (phase III) is sensitive to the total cross-sectional area of these airways. Therefore, the influence of age and body size on the phase III slope of the volumetric capnogram was investigated. METHODS: Phase III slope (alveolar dcCO2/dv) and airway deadspace (VDaw) were derived from repeated single-breath carbon dioxide expirograms collected on 44 healthy mechanically ventilated children (aged 5 months-18 yr) undergoing minor surgery. Ventilatory support was standardized (VT = 8.5 and 12.5 ml/kg, f = 8-15 breaths/min, inspiratory time = 1 s, end-tidal partial pressure of carbon dioxide = 30-45 mmHg), and measurements were recorded by computerized integration of output from a heated pneumotachometer and mainstream infrared carbon dioxide analyzer inserted between the endotracheal tube and anesthesia circuit. Experimental data were compared to simulated breath data generated from a numeric pediatric lung model. RESULTS: An increased VDaw, a smaller VDaw/VT, and flatter phase III slope were found at the larger tidal volume (P < 0.01). Strong relationships were seen at VT = 12.5 ml/kg between airway deadspace and age (R2 = 0.77), weight (R2 = 0.93), height (R2 = 0.78), and body surface area (R2 = 0.89). The normalized phase III slopes of infants were markedly steeper than that of adolescents and were reduced at both tidal volumes with increasing age, weight, height, and body surface area. Phase III slopes and VDaw generated from modelled carbon dioxide washout simulations closely matched the experimental data collected in children. CONCLUSIONS: Morphometric increases in the alveolated airway cross-section with lung growth is associated with a decrease of the phase III slope. During adolescence, normalized phase III slopes approximate those of healthy adults. The change in slope with lung growth may reflect a decrease in diffusional resistance for carbon dioxide transport within the alveolated airway resulting in diminished acinar carbon dioxide gradients.

Adolescent↗

PubMed1991

Simple developmental speech delay: a follow-up study.

The authors followed 38 children with delayed speech development approximately two to four years after initial diagnosis, assessing and comparing their subsequent speech and language, and over-all development. Nearly all of the children had appropriate language levels for their general development. Just over half had less articulation competence than expected for their age, but this was not related to language achievement or age. It appears that the prognosis for future language development is favourable for these children. The results suggest that articulation might be a developmentally related process with a good prognosis, but further follow-up is necessary to determine ultimate competence of children in whom this is delayed.

Articulation Disorders↗

PubMed1989

A randomized comparison of total extracorporeal CO2 removal with conventional mechanical ventilation in experimental hyaline membrane disease.

Apnoeic oxygenation (AO) combined with extracorporeal CO2 removal (ECCO2R), using venovenous perfusion across a membrane area of 0.1 m2 has been shown to be feasible in six healthy anaesthetized rabbits. In a further twelve rabbits, ECCO2R has been randomly compared with conventional mechanical ventilation (CMV) following saline lavage to induce respiratory failure. Blood gases were maintained for up to 6 h within the same range (PaO2 = 8-20 kPa, PaCO2 = 4-6 kPa) in two groups of six by varying airway pressures and the oxygen fraction delivered either to the membrane lung (ECCO2R group) or to the ventilator (CMV group). The influence of single hourly sustained inflations (SI) on oxygenation was studied. ECCO2R subjects remained stable and survived. CMV subjects deteriorated and had 80% mortality. Hyaline membranes were absent from ECCO2R subjects and present in all CMV subjects. The response to SI suggests that a lung volume recruitment is maintained during AO for up to 1 h but is ineffective during CMV.

Animals↗

PubMed1989

Haemolysis during in vitro CO2 removal from human blood using a membrane lung.

Haemolysis of human blood has been examined in vitro as a function of pH in the range 7.2-8.0. The hydrogen ion concentration of freshly donated blood from 11 donors was manipulated in 42 experiments, entirely by altering the carbon dioxide fraction of air with which the blood was equilibrated using a membrane lung. In contrast to the known alkalaemic haemolysis which occurs in canine blood, we observed no correlation between plasma haemoglobin concentrations and blood pH. We conclude that alkalaemic haemolysis is unlikely to complicate the clinical application of extracorporeal carbon dioxide removal in the management of acute respiratory failure.

Acid-Base Equilibrium↗