Nordberg P, Hermansson T, Backman A, Svensson L, Jonsson M, Hollenberg J, Ringh M, Dillenbeck E, Forsberg S
Background: Experimental and clinical data indicate that mild hypothermia is neuroprotective after a period of global cerebral hypoxia-ischemia. Trans nasal evaporative cooling (RhinoChill™) is safe and effective in unconscious patients but it has never been properly tested on patients who are conscious and awake (waking patients). The aim of this study is to study if trans nasal evaporative cooling is safe, tolerable and effective in healthy, awake volunteers without providing any sedative medication.
Methods: This was a prospective, single centre study where nine healthy volunteers underwent trans nasal evaporative cooling for up to 60 minutes. Cooling began with a low flow of oxygen at a rate of 10-20 litres/min and was gradually increased to 40 litres/min. Continuous hemodynamic monitoring was performed and temperatures (forehead, tympanic, esophageal and rectal) were assessed every 10 minutes. Visual analogue scales (VAS) were used to evaluate pain and discomfort during cooling.
Results: During cooling there was a significant increase in median heart rate (70 to 81 beats /minutes, p=0.009), median systolic-(140 to 163 mmHg, p=0.001) and diastolic blood pressure (77 to 93, p=0.01) and respiratory rate (14 to 18 breaths/ minute, p=0.04) as compared to before cooling. The volunteers cooled for more than 45 minutes (n=6), experienced a significant decrease in tympanic (37.1 to 36.2, p=0.04) and forehead temperature (36.5 to 35.0, p=0.04), but not in rectal and esophageal temperatures. All of the nine participants experienced discomfort (VAS 7/10) and pain (VAS 6/10) during cooling. In one case cooling was interrupted due to mild periorbital emphysema.
Conclusion: Trans nasal evaporative cooling in awake and healthy volunteers is safe and may be tolerable. Cooling was associated with modest but significant lowering of tympanic- and forehead temperatures. The volunteers experienced pain and discomfort, and a significant increase in heart rate, blood pressure and respiratory rate was seen.
