Oral mucosal blood flow following dry ice stimulation in humans

The aim of the current pilot study was to establish a procedure that would allow the investigation of microcirculatory changes in the oral cavity. The authors studied the effects of painful stimulation using dry ice (CO₂). To investigate potential regional differences in the change of blood flow, recordings were made for the tongue and at the mucosa of the hard palate, lip, and oral vestibule. The authors investigated 26 patients divided into groups of younger subjects (10 men, 3 women; age range 21-31 y) and older patients (2 men, 11 women; age range 54-74 y). Mucosal blood flow (mBF) was obtained at the hard palate, at the tip of the tongue, on the midline of the oral vestibule, and at the lip. Measurements were made during rest and for 2 minutes after application of dry ice for a 10-second duration, using a pencil-shaped apparatus. Blood pressure, heart rate, cutaneous blood flow, transcutaneous partial pressure of carbon dioxiode (PCO₂) and partial pressure of oxygen (PO₂) were recorded. Mucosal blood flow increased at all sites in response to application of dry ice (p <0.001), with peak flow at 0.5 minute to 1.5 minutes after onset of stimulation. During the 1.5 minutes to 2 minutes, blood flow decreased at all measurement sites with a tendency to return to baseline. Heart rate, blood pressure, pCO₂, pO₂, and cutaneous blood flow did not show significant changes. Overall, responses in older patients showed more variance when compared with younger patients. Stimulation by dry ice appears to be an effective, noninvasive, and tolerable means to investigate mucosal blood flow at different mucosal sites. Preliminary data indicate different levels of responsiveness to painful cold stimulation at different sites on the oral and perioral mucosa; particularly, mucosal blood flow response at the tongue was least pronounced. Therefore, assessment of stimulated mucosal blood flow appears to be a promising tool to investigate the pathophysiology of a number of neurologic symptoms, eg, the burning mouth syndrome.