Thinking Out-of-the-Box: A Non-Standard Application of Standard Pulse-Oximetry and Standard Near-Infrared Spectroscopy in a COVID-19 Patient.

PURPOSE: Purpose of this report is to describe the feasibility of lingual pulse oximetry and lingual near-infrared spectroscopy (NIRS) in a COVID-19 patient to assess lingual tissue viability after several days of mechanical ventilation in the prone position.

MATERIALS & METHODS: In a COVID-19 ICU-patient, the tongue became grotesquely swollen, hardened and protruding from the oral cavity after 20 h of mechanical ventilation uninterrupted in the prone position. To assess the doubtful viability of the tongue, pulse-oximetric hemoglobin O2 -saturation (SpO2 ; Nellcor, OxiMax MAX-NI, Covidien, MA, USA) and NIRS-based, regional tissue O2 -saturation measurements (rSO2 ; SenSmart, Nonin, MN, USA) were performed at the tongue.

RESULTS: At the tongue, regular pulse-oximetric waveforms with a pulse-oximetric hemoglobin O2 -saturation (SpO2 ) of 88% were recorded, i.e. only slightly lower than the SpO2 reading at the extremities at that time (90%). Lingual NIRS-based rSO2 measurements yielded stable tissue rSO2 -values of 76-78%, i.e. values expected also in other adequately perfused and oxygenated (muscle-) tissues.

CONCLUSION: Despite the alarming, clinical finding of a grotesquely swollen, rubber-hard tongue and clinical concerns on the adequacy of the tongue perfusion and oxygenation, our measurements of both arterial pulsatility (SpO2 ) and NIRS-based tissue oxygenation (rSO2 ) suggested adequate perfusion and oxygenation of the tongue, rendering non-vitality of the tongue, e.g. by lingual venous thrombosis, unlikely. To our knowledge, this is the first clinical report of lingual rSO2 measurement.