Research Paper Clinical Autonomic Research 2000, 10:317-321 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 re- gional 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 di- vided 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 pres- sure 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 mea- surement 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 pa- tients 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 dif- ferent 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 pro- nounced. Therefore, assessment of stimulated mucosal blood flow appears to be a promising tool to investigate the patho- physiology of a number of neurologic symptoms, eg, the burn- ing mouth syndrome. Key words: nociception, irritation, mucosal blood flow, laser Doppler, oral cavity, aging. Oral mucosal blood flow following dry ice stimulation in humans Josef G. Heckmann, M.D., 1 Max J. Hilz, M.D., Ph.D., 1 Thomas Hummel, M.D., Ph.D., 2 Michael Popp, M.D., 3 Harald Marthol, M.D., 1 Bernhard Neund6rfer, M.D., Ph.D., 1 and Siegfried M. Heckmann M.D., Ph.D. 3 1Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany; 2Department of Otorhinolaryngology, University of Dresden Medical School, Dresden, Germany; 3Department of Prosthodontics, University of Erlangen-Nuremberg, Erlangen, Germany Address correspondence and reprint requests to J.G. Heckmann, M.D., Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany. Tel: 49-9131-853-3001; Fax: 49-9131-853-4436 E-Mail: Josef.heckmann@neuro.med.unierlangen ReceivedJanuary 3, 2000; accepted as revisedJuly 26, 2000 Blood supply of the tongue comes through the lingual ar- tery, a branch of the external carotid artery [1]. Sensory afferents run with the lingual nerve, a branch of the man- dibular nerve. Gustatory sensitivity is mediated by the facial, glossopharyngeal, and vagal nerves [2]. The mucosa of the tongue is highly vascularized [3,4]. Changes in blood flow may be assessed by means of laser Doppler flowmetry. This technique was developed to assess blood flow in the retina, gut mesentery, renal cortex, and cerebral cortex, or on the skin [5,6]. Numerous publications already have established that it is possible to record blood flow changes from intraoral sites [3,6-14]. However, little is known about the microcirculation of the lingual rnucosa during rest or in response to stimulation. There are few reports regarding mucosal blood flow (mBF); these reports investigated the effects of tooth brushing, application of sodium lauryl sulfate, or facial cooling [4,15,16]. There is speculation that microcirculation is impaired in a number of diseases, such as glossodynia, glossitis, the Melkerson- Rosenthal syndrome, pandysautonomy, diabetic microangi- opathy, sleep-apnea syndrome, or liver cirrhosis; further- more, pharmacologic treatment may alter intraoral blood flow, eg, treatment with tricyclic antidepressants [2,17-21 ]. The aim of the current pilot study was to establish a procedure that would allow the investigation of microcir- culatory changes in the oral cavity. Therefore, we studied effects of painful stimulation using dry ice (CO2). To in- vestigate potential regional differences in the change of blood flow, recordings were made on the tongue and at the mucosa of the hard palate, the lip, and the oral vestibule. Patients and methods Patients We investigated a total of 26 patients divided into groups of younger patients (10 men, 3 women; age range 21-31 y; mean age 25.6 y) and older patients (2 men, 11 women; age range 54-74 y; mean age 64.7 y). All patients were in good health. The selection of the older group was intentional; patients with mucosal disorders are predominantly elder women [18]. The patients provided informed consent for 0959-9851 9 2000 LippincottWilliams & Wilkins 317