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Available online 6 May 2022
Use of the ROX index in the assessment of success of high-flow oxygen therapy in secondary hypoxemia to type 2 coronavirus
Utilización del índice de ROX en la valoración del éxito de oxigenoterapia de alto flujo en la hipoxemia secundaria a coronavirus tipo 2
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A. González-Castroa, A. Fajardo Campoverdeb,
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drauriopiotr@gmail.com

Corresponding author.
, A. Roncalli Rochac, Grupo LATAM de ventilación mecánica (WeVent)
a Servicio de Medicina Intensiva, Hospital Universitario Marqués de Valdecilla, Santander, Spain
b Servicio de Medicina Interna – Unidad de Paciente Crítico, Viña del Mar, Chile
c Hospital Escola Helvio Auto Maceió, Maceió, Brazil
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Dear Editor:

High-flow nasal cannula (HFNC) provide high-flow oxygen—up to 60 L/min—with FiO2 between 0.21 and 1. The potential benefits would be: improved respiratory pattern with a lower respiratory rate (RR).

One variable suggested to assess success or failure is the ROX index (ROXI) that combines oxygenation (SpO2/FiO2 ratio) and respiratory effort (RE). Its validity in the management of COVID-19-related pneumonia has a high sensitivity to predict failed therapies,1 and is associated with a high mortality rate (45.4%).2

Regarding the denominator (RE) in the assessment of the ROXI, the retrograde, transcriptional, and hematogenous neuronal dissemination have been reported as possible access routes used by SARS-CoV-2 to enter the central nervous system. As a matter of fact, respiratory and cardiovascular vital centers of the brainstem are potential targets for SARS-CoV-2.3 Sensitivity changes to peripheral chemoreceptors of carotid bodies invaded by SARS-CoV-2 can lead to a disproportionate ventilatory response at hypoxia level. Hyperexcitability can be developed in some cases and desensitization in others. Therefore, changes to the RE during the use of HFNC may not be associated directly with respiratory effort.4

During atypical acute respiratory distress syndrome (ARDS) due to SARS-CoV-2, patients often show a relatively well-preserved pulmonary mechanism that is not consistent with the severity of hypoxemia. To this point, several mechanisms converge: dysregulated pulmonary perfusion and hypoxic vasoconstriction, “infectious toxic encephalopathy” (central hypoxia), and damage to the carotid body5 that could also be a route of infection into the nervous system.

We believe that we should be cautious when using the ROX index only as a predictor of success or failure in these patients.

Funding

None reported.

Conflicts of interest

None whatsoever.

References
[1]
L. Suliman, T. Abdelgawad, N. Farrag, H. Abdelwahab.
Validity of ROX index in prediction of risk of intubation in patients with COVID-19 pneumonia.
Adv Respir Med, 89 (2021), pp. 1-7
[2]
A. Chandel, S. Patolia, A.W. Brown, A.C. Collins, D. Sahjwani, V. Khangoora, et al.
High-flow nasal cannula in COVID-19: outcomes of application and examination of the ROX index to predict success.
Respir Care, 66 (2020), pp. 909-919
[3]
Y. Li, W. Bai, T. Hashikawa.
The neuroinvasive potential of SARS-CoV2 may play a role in the respiratory failure of COVID-19 patients.
J Med Virol, 92 (2020), pp. 552-555
[4]
B. Machado, J. Paton.
Relevance of carotid bodies in COVID-19: a hypothetical viewpoint.
Auton Neurosci, 233 (2021),
[5]
B. Lambermont, E. Davenne, F. Maclot, P. Delvenne.
SARS-CoV-2 in carotid body.
Intensive Care Med, 47 (2021), pp. 342-343

Please cite this article as: González-Castro A, Fajardo Campoverde A, Roncalli Rocha A, Grupo LATAM de ventilación mecánica (WeVent). Utilización del índice de ROX en la valoración del éxito de oxigenoterapia de alto flujo en la hipoxemia secundaria a coronavirus tipo 2. Med Intensiva. 2022. https://doi.org/10.1016/j.medin.2021.07.001

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Medicina Intensiva (English Edition)

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