Effect of increased intra-aortic balloon pressure on catheter volume: relationship to changing altitudes.

OBJECTIVE: To evaluate the effect of intra-aortic balloon membrane response under increasing intracatheter pressure by indexing these data to associated barometric pressures that occur with changes in altitude. DESIGN: A static compliance test was performed to assess the effect of internal pressure on intra-aortic balloon compliance (simulating helium gas within the intra-aortic balloon affected by barometric pressure). Testing consisted of incrementally increasing pressure within eight percutaneous intra-aortic balloons from four leading manufacturers. SETTING: The University of Utah Department of Mechanical Engineering Laboratory. PATIENTS: No patients were involved. This study was a bench test lab study. INTERVENTIONS: No patient interventions were utilized. RESULTS: Results for all trials showed a curvilinear relationship between intracatheter pressure and balloon volume. Clinically significant balloon expansion data were obtained, with manufacturer variation observed at moderate-to-high pressures. CONCLUSIONS: Based on the results of this study, recommendations for operation of intra-aortic balloon pumps during altitude ascent and descent are proposed, from which individual institutional protocols may be developed.

Spinal cord localization and characterization of the neurons which give rise to the accessory phrenic nerve in the adult rat.

This study describes the spinal cord location and morphology of the neurons which give rise to the accessory phrenic nerve in the rat. The results indicate that the cell bodies of the accessory phrenic nerve are a caudal extension of the phrenic nucleus. These cell bodies are located from cervical spinal cord levels C5 to upper C6 and comprise approximately 11% of the total phrenic motoneuron pool. The substantial phrenic contribution indicates the importance of the accessory phrenic nerve in both experimental and clinical manipulations of diaphragm innervation.