A conscious baboon model for evaluation of hemodynamics in altered gravity

A model was developed for evaluation of cardiovascular parameters in conscious baboons exposed to altered gravitational environments. Baboons were trained to sit quietly in a confinement chair of unique design which allowed a range of normal physical activity. They were then instrumented with high-fidelity blood pressure transducers in the aorta and left ventricle, electromagnetic flow probes encircling the proximal ascending aorta, left and right atrial fluid catheters, left ventricular sonomicrometer crystals in a 3-axis configuration, and a hydraulic occluder cuff encircling the inferior vena cava. Catheters and transducer wires were exteriorized at the midscapular region of the back. Viability of percutaneous exit sites was enhanced by use of velour cuffs on the transducer wires, providing a scaffold for wound healing. Pressure transducers and flow probes were calibrated and balanced during postoperative cardiac catheterization procedures. This instrumentation allowed measurement of beat-to-beat stroke volume and cardiac output not reliant on thermodilution techniques. Postoperative longevity was from 1 to 10 months. Instrumentation failure included endocardial trapping of ventricular pressure transducers, corrosion of ventricular sonomicrometer crystals, and catheter tip thrombosis. Acquisition of high quality data was possible with this model in several different environments of altered gravitational stress, allowing characterization of aortic flow and ventricular performance.