Hyperventilation

Hyperventilation: instruct the patient to breathe rapidly in and out of their mouth for 40-60 seconds. Alkalosis and changes in ionized calcium may improve conduction through an affected segment of 8th cranial nerve due to vestibular schwannoma (https://collections.lib.utah.edu/details?id=1213447) or neurovascular compression, usually causing an excitatory (ipsilesional) nystagmus. When a chronic vestibular imbalance has been compensated for by central mechanisms, hyperventilation can cause a transient decompensation and bring out nystagmus with an ipsilesional slow phase. Hyperventilation can enhance/produce downbeat nystagmus in cerebellar disease (https://collections.lib.utah.edu/details?id=1427580&q=hyperventilation&fd=title_t%2Cdescription_t%2Csubject_t&facet_setname_s=ehsl_novel_gold)