Didactic prototype demonstrates the effect of intracranial pressure on cerebral perfusion pressure/Prototipo didatico demonstra o efeito da pressao intracraniana sobre a pressao de perfusao cerebral

• Published in: Revista de medicina (São Paulo, Brazil) Vol. 101; no. 6
• Main Authors: Cassani, Marcus Roberto Magalhaes, Guilarducci, Victor Toledo, Hohl, Rodrigo, Mourao-Junior, Carlos Alberto, Nagato, Akinori Cardozo
• Format: Journal Article
• Language: Portuguese
• Published: Universidade de Sao Paulo. Departamento Cientifico da Faculdade de Medicina 01.11.2022
• ISSN: 0034-8554
• DOI: 10.11606/issn.1679-9836.v101i6e-196560

Cerebral perfusion pressure (CPP) results from the difference between mean arterial pressure and intracranial pressure (ICP). The comprehension of the biophysical principles that explain how ICP influences CPP dynamics requires abstraction and can be explained by analogy using low-cost prototypes. Objective: To come up with a didactic prototype developed with recyclable materials that shows the influence of ICP on CPP. Method: A prototype was built with a 200 ml PET bottle, overpassed by a 06 cm latex ball (standard: 5:150 cm), simulating respectively, the skull and a single cerebral vessel. A 10 ml syringe was connected to the PET in order to reduce the volume of the system and increase the pressure inside it. A latex bulb, containing an unidirectional valve, was connected to the latex ball through a double-lumen tube, in which, one of the branches was used to direct an airflow to the latex ball. To demonstrate the pressure variation inside the PET ([DELTA]PI) and inside the latex ball ([DELTA]P2), two aneroid manometers (M1 and M2, respectively), connected with latex hoses, were used. All connections have been sealed with silicone. Results: The syringe plunger compression reduced the system volume and increased [DELTA]P1 = 30mmHg, resulting in a collapsed ball and increased resistance to the air flow (with an increase of [DELTA]P2 = 30 mmHg in M2) when the bulb was pressed. The perceived handgrip effort to compress the bulb was higher when [DELTA]PI was increased. The prototype allowed a direct intuitive comparison between the PET/skull and the ball/blood vessel, and it was also possible to see how the elevation of the ICP plays an important role in the CPP. Conclusion: Prototypes with low-cost materials are intuitive and easily accessible tools that can be used to didactically illustrate the fundamental biophysical influence of ICP on CPP in humans.