Biomedical subjects

S A Conrad

Publications and source records attributed to S A Conrad.

40 records · Page 3Linked to original sources

PubMedDate not supplied

Arteriovenous extracorporeal carbon dioxide removal: a mathematical model and experimental evaluation.

To explore the feasibility and operating limits of arteriovenous extracorporeal CO2 removal (AVCO2R) for support of acute respiratory failure, the authors developed a mathematical model to simulate (AVCO2R), evaluate the effects of several parameters used in its application, and predict the feasibility and necessary conditions for total CO2 removal. The mathematical model incorporated compartments representing blood, pulmonary alveoli, pulmonary capillaries, peripheral tissues and capillaries, and an extracorporeal gas exchange device. The model was validated against an animal model of extracorporeal CO2 removal. This model consisted of anesthetized and mechanically ventilated piglets. An extracorporeal CO2 removal device was placed by cannulation of a femoral artery and vein. Dynamic and steady state measurements of CO2 transfer were made and compared with simulations using the mathematical model. There was good agreement between experimental and simulated data, validating the mathematical model under a variety of conditions. The mathematical model was used to determine operating parameters for total CO2 removal. Relationships between extracorporeal blood flow, device diffusing capacity, and device gas sweep flow were established for CO2 removal at various levels of CO2 production. These simulations indicate that it is possible to achieve total CO2 removal using an extracorporeal shunt fraction of 10%-15% of cardiac output, a device diffusing capacity of 0.5 ml x min(-1) x torr(-1) (kg body weight)(-1), and a gas:blood flow of 5 or greater.

Animals↗

PubMedDate not supplied

Extracorporeal life support 1997.

Data from the annual international Extracorporeal Life Support Organization (ELSO) Registry Report for 1997 are presented. Over 17,000 patients treated with extracorporeal life support as submitted to the ELSO Registry are reported. Seventy-five percent (over 13,000) patients were cases of neonatal respiratory failure, with an 80% overall survival. The number of neonatal respiratory cases reported to the Registry has been decreasing for 5 years, whereas the number of pediatric respiratory, cardiac, and adult respiratory cases has been increasing. Cumulative survival in these categories is 53%, 42%, and 47% respectively. Survival in pediatric and adult respiratory failure cases supported with extracorporeal life support continues to improve. A description of the re-engineering of the ELSO registry, to include redesigning of the database structure and elements, electronic submission and validation of data, and Internet based submission and retrieval of data, is also provided.

Adult↗

PubMedDate not supplied

Effects of gas leak around endotracheal tubes on indirect calorimetry measurement.

The use of uncuffed endotracheal tubes (ETT) in pediatric patients raises concern over the accuracy of indirect calorimetry measurement in the presence of a gas leak around an ETT. We examined the effects of ETT gas leak on respiratory gas measurements in a dog model. Mongrel dogs (n = 12) were sedated, paralyzed, intubated, and placed on mechanical ventilation. Leak was achieved by adjusting cuff volume. Oxygen consumption (VO2), CO2 production (VCO2), respiratory exchange ratio (RER), and resting energy expenditure (REE) were measured at each leak pressure (Pleak). Peak inspiratory pressure (PIP), Pleak, inspiratory and expiratory tidal volume (VTinsp, VTexp), VE, end tidal CO2 (ETCO2), and blood gases were recorded at each leak pressure. VO2, VCO, and REE decreased significantly with increasing gas leak. There was a linear relationship between VO2, VCO2, and REE with both TVratio (VTexp/VTinsp) and Pdiff (PIP-Pleak). Multiple regression equations based on TVratio and Pdiff were obtained which allowed correction of the measurement error in VO2, VCO2, and REE, with correlation coefficients (R2) of 0.71, 0.75, and 0.73, respectively. ETT gas leak affects measurements of VO2, VCO2, and REE, but not RER. Measurements made with TVratio greater than 0.80 required no correction. Measurements made with TVratio greater than 0.45 could be corrected to actual values in our model with regression equations based on TVratio and Pdiff. We conclude that indirect calorimetry measurements can be useful in the presence of tracheal gas leak around an ETT.

Animals↗

PubMedDate not supplied

Tracking nutrition trends, 1989-1994: an update on Canadians' attitudes, knowledge and reported actions.

The National Institute of Nutrition tracks changes in Canadians' attitudes, understanding and reported actions related to nutrition issues--particularly fat cholesterol and fibre. Personal interviews were conducted in 1994 with a national sample of 1,953 adults, and the results were compared with data obtained in 1989. The number of people claiming that nutrition is of considerable importance in choosing their food has increased from 59% to 66%. More Canadians are now concerned about fat (82% vs 71%) and "chemicals" in foods (76% vs 68%) and more are planning to further reduce fat or increase fibre intake. Forty-three percent report having excellent or very good eating habits. The apparent use of food labels, lower fat/low--cholesterol products, and bran/high-fibre foods has grown in five years. Although awareness of nutrition terms has increased, understanding has changed little. The challenge is to build on consumer interest to reduce barriers to healthy eating through education and a supportive marketplace.

Adolescent↗