Feasibility and Safety of Transnasal High Flow Air to Reduce Core Body Temperature in Febrile Neurocritical Care Patients: A Pilot Study

A Commentary to this article is available

A Commentary to this article is available

A Commentary to this article is available



Fever is an important determinant of prognosis following acute brain injury. Current non-pharmacologic techniques to reduce fever are limited and induce a shivering response. We investigated the safety and efficacy of a novel transnasal unidirectional high flow air device in reducing core body temperature in the neurocritical care unit (NCCU) setting.


This pilot study included seven consecutive patients in the NCCU who were febrile (> 37.5 °C) for > 24 h despite standard non-pharmacologic and first-line antipyretic agents. Medical grade high flow air was delivered transnasally using a standard continuous positive airway pressure machine with a positive pressure of 20 cmH2O for 2 h. Core esophageal and tympanic temperature were continuously monitored.


Mean age was 40 ± 14 yo, and 72% (5/7 patients) were men. Five patients had intracerebral or intraventricular hemorrhage, one subject had transverse myelitis, and the remaining patient had anoxic brain injury due to a cardiac arrest. After 2 h of cooling, core temperature was significantly lower than the baseline pre-cooling temperature (37.3 ± 0.5 °C vs. 38.4 ± 0.6 °C; p < 0.002). Mean transnasal airflow rate was 57.5 ± 6.5 liters per minute. Five of the seven subjects were normothermic at the end of the 2-h period. One subject with severe hyperthermia (39.7 °C) and the other with multiple interruptions to therapy due to technical reasons did not cool. The core temperature within 30 min of cessation of airflow increased and was similar to the pre-cooling baseline temperature (38.3 ± 0.4 °C vs. 38.4 ± 0.6 °C, p = NS). Rate of core cooling was 0.6 ± 0.15 °C per hour at this flow rate. No shivering response was observed. No protocol-related adverse events occurred.


High flow transnasal air in a unidirectional fashion lowers core body temperature in febrile patients in the NCCU setting. No adverse events were seen, and the process showed no signs of shivering or any other serious side effects during short-term exposure. This pilot study should inform further investigation.

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Neurocritical care unit


Ear, nose and throat


Continuous positive airway pressure


Liters per minute


Systolic blood pressure


Diastolic blood pressure




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Funding was provided by Key Technologies Inc.

Author information




WZ analyzed the data and wrote the manuscript. DS collected the data. FRA analyzed the data and reviewed the manuscript. HT analyzed the data and wrote the manuscript. RGG supervised the project, analyzed the data and reviewed the manuscript.

Corresponding author

Correspondence to Wendy C. Ziai.

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Conflict of interest

Harikrishna Tandri is the founder of CoolTech Inc, which is developing a transnasal device for hypothermia. Other authors declare that they have no conflict of interest.

Ethical Approval/Informed Consent

This study was approved by the Johns Hopkins University Institutional Review Board (IRB00086134).

Human and Animal Rights

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

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Informed consent was obtained from all individual participants included in the study.

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Ziai, W.C., Shah, D., Assis, F.R. et al. Feasibility and Safety of Transnasal High Flow Air to Reduce Core Body Temperature in Febrile Neurocritical Care Patients: A Pilot Study. Neurocrit Care 31, 280–287 (2019). https://doi.org/10.1007/s12028-019-00702-x

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  • Fever
  • Neurocritical Care
  • Normothermia
  • Neuroprotection
  • Transnasal evaporative cooling