Cushing Reflex - History - Experimental Setup and Results

Experimental Setup and Results

Cushing began experimenting once he obtained approval from Kocher. His experimental setup was a modified version of Leonard Hill's model to similarly test the effects of brain pressure on sinus pressure, cerebrospinal fluid pressure, arterial and venous blood pressure. Like Hill, Cushing used dogs for his experiments. To begin, Cushing monitorred the caliber and color of cortical vessels by fitting a glass window into the skull of the dog. Intracranial pressure was raised by filling an intracranial, soft, rubber bag with mercury. Cushing recorded the intracranial pressure along with blood pressure, pulse rate, and respiratory rate simultaneously. This three part effect is commonly referred to as Cushing's triad. In later experiments performed by Mosso, intrcranial pressure was induced by injecting physiological saline into the subarachnoid space rather than increasing mercury content of an intracranial bag.

This research clearly displayed the cause and effect relationship between intracranial pressure and cerebral compression. Cushing noted this relationship in his subsequent publications. He also noted that there must exist a specific regulatory mechanism that increased blood pressure to a high enough point such that it did not create anemic conditions. Cushing's publications contain his observations and no statistical analysis. The sample size of the experiment is also not known.