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REVIEW ARTICLE
Year : 2020  |  Volume : 23  |  Issue : 4  |  Page : 201-205

Rational supplemental oxygen therapy in COVID-19


Department of Pulmonology and Respiratory Medicine, Faculty of Medicine, Persahabatan Hospital, Universitas Indonesia, Jakarta, Indonesia

Date of Submission06-Jun-2020
Date of Decision01-Aug-2020
Date of Acceptance25-Aug-2020
Date of Web Publication23-Feb-2021

Correspondence Address:
Dr. Mia Elhidsi
Jalan Persahabatan Raya No. 1, Rawamangun, Jakarta, 13230
Indonesia
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DOI: 10.4103/smj.smj_64_20

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  Abstract 


Background: Hypoxemia often occurs in Coronavirus disease 2019 (COVID-19) patients. This condition requires adequate oxygen therapy to achieve oxygen saturation target. Objective: This review aims to explain the rational oxygen therapy in COVID-19. Materials and Methods: A literature search for studies on COVID-19 was performed using PubMed and Science Direct database. About 46 articles were identified. Twenty-five articles were considered suitable for review. The bibliographies of included studies were also searched for additional references. Results: Oxygen therapy involves conventional devices such as nasal cannulas, simple masks, reservoir masks, and venturi to advanced devices such as high-flow nasal cannulas. Initial therapy is given based on holistic assessment of the patient, followed by close monitoring. In emergency situations, airway management is required, and resuscitation is carried out with a saturation target of ≥94% while in stable patients, the SpO2 target is >90% in nonpregnant and ≥92%–95% in pregnant patients. Oxygen escalation might be needed during therapy without delaying intubation. Besides its intricate management algorithm, the rational management of oxygen therapy in COVID-19 also requires caution on the issue of each aerosol-generating device and transmission risk, especially for health-care workers. Conclusions: Rational management of oxygen therapy includes the provision of initial therapy, followed by proper monitoring and escalation without delaying intubation and also the considerations of the health-care workers' protection and the risk of transmission.

Keywords: COVID-19, oxygen, therapy


How to cite this article:
Elhidsi M, Rasmin M, Prasenohadi, Aniwidyaningsih W, Desianti GA, Alatas MF, Soehardiman D. Rational supplemental oxygen therapy in COVID-19. Sahel Med J 2020;23:201-5

How to cite this URL:
Elhidsi M, Rasmin M, Prasenohadi, Aniwidyaningsih W, Desianti GA, Alatas MF, Soehardiman D. Rational supplemental oxygen therapy in COVID-19. Sahel Med J [serial online] 2020 [cited 2021 Mar 6];23:201-5. Available from: https://www.smjonline.org/text.asp?2020/23/4/201/310029




  Introduction Top


Coronavirus disease 2019 (COVID-19) is a disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection, which primarily attacks the respiratory system. Clinical manifestations vary from asymptomatic to severe pneumonia, which can cause death. The most common early symptoms are fever and dry cough. Shortness of breath occurs in about 30%–60% of cases, the average occurs on days 5–8, and acute respiratory distress syndrome can occur above day 10.[1],[2],[3] Hypoxemia mostly occurs within the first 10 days of hospital admission and even more likely in patients >60 years of age.[4] In patients with moderate-severe disease levels, oxygen therapy is a necessary initial treatment. Supplemental oxygen therapy is the first-line therapy to improve patient oxygenation and prevent patients from the need for intubation and intensive care. This therapy needs to be performed rational with close monitoring without delaying intubation. Issues regarding aerosols and the risk of transmission during the use of oxygen therapy are among the most important concerns during its administration.


  Materials and Methods Top


A systematic search was conducted in the electronic bibliographic databases of PubMed and Science Direct. The key words and strategy used in PubMed were: (((COVID-19[Title]) OR (SARS-CoV-2[Title])) OR (respiratory failure[Title]) AND ((y_1[Filter]) AND (ffrft[Filter]) AND (clinicaltrial[Filter] OR meta-analysis[Filter] OR randomizedcontrolledtrial [Filter] OR review[Filter] OR systematicreview[Filter]))) AND ((((((((((oxygen therapy[Title]) OR (supplemental oxygen[Title])) OR (respiratory support[Title])) OR (ventilatory support[Title])) OR (supplemental oxygen therapy[Title])) OR (high flow nasal cannula[Title])) OR (high flow nasal oxygen[Title])) OR (non-invasive ventilation[Title])) OR (NIV[Title])) OR (non-invasive mechanical ventilation[Title]) AND ((y_1[Filter]) AND (ffrft[Filter]) AND (clinicaltrial[Filter] OR meta-analysis[Filter] OR randomizedcontrolledtrial[Filter] OR review[Filter] OR systematicreview[Filter]) AND (fft[Filter]))). The key words and strategy used in Science Direct were: ((COVID-19) OR (“respiratory failure”)) AND ((“oxygen therapy”) OR (“nasal cannula”) OR (“oxygen mask”) OR (“non-invasive ventilation”) OR (“NIV”)). The search was limited to journal articles published in 2010–2020. About 46 articles were identified, and after the elimination of unrelated articles to the subject matter and double articles, 25 related articles were available for the review. The bibliographies of included articles were also searched for additional references. The discussion on the rational oxygen therapy was drawn from clinical experiences in Indonesia, webinar interactions with colleagues and expert opinions.

Initial oxygen therapy

In providing initial oxygen therapy, we need to assess the overall clinical condition of the patient, including the patient's oxygenation through pulse oximetry. Despite having a difference of about 4% compared to actual arterial saturation, oximetry saturation (SpO2) is still an important and practical tool in assessing patient oxygenation.[5]

In emergency situations, such as airway obstruction, apnea, central cyanosis, shock, coma or seizures, airway management are required, and resuscitation is carried out with a saturation target of ≥94%. Oxygen supplementation can begin using a nasal cannula at 5 L/min or a mask with a reservoir bag at 10–15 L/min, then titrate as necessary. After the patient is stable, the SpO2 target is >90% in nonpregnant adult patients and ≥92%–95% in pregnant patients.[6] In stable patients, oxygen can be directly given if SpO2 is <90%.[6],[7],[8]

Devices that can be used in supplemental oxygen therapy are nasal cannulas, simple masks, reservoir masks, and high flow nasal cannulas. The concentration of oxygen (fraction of inspired oxygen [FiO2]) given through the nasal cannula depends on the patient's breathing strength (patient's peak inspiratory flow). This tool can deliver a FiO2 of up to 45% with a flow of up to 5–6 L/min. However, a high flow of oxygen can cause nasal dryness, irritation, and discomfort, therefore humidification is often needed.[7],[9]

Simple masks can deliver a slightly higher oxygen concentration than nasal cannulas, at 40%–60% FiO2 with a flow of 5–10 L/min. However, the actual FiO2 depends on the patient's breathing effort. Venturi masks can deliver oxygen more accurately. The flow which enters through the mask is diluted in the air. Thus, the higher the flow, the more air is introduced. Due to its fixed oxygen concentration, this type of mask will give the same oxygen concentration regardless of airflow. FiO2 is delivered at 24%–60% with a flow of 2–15 L/min.

Another mask that is often used is a nonrebreather mask (NRM). This mask is connected to an oxygen reservoir accompanied with a valve to prevent the patient from breathing in expiratory air. Although NRM masks can deliver high FiO2 at around 80%–95% with a flow of 15 L/min, the FiO2 still depends on the patient's breathing pattern. A minimum flow of 8–10 L/min is required. A flow lower than that can cause the reservoir bag to collapse during inspiration.[7],[9],[10]

An advanced supplemental oxygen therapy device that is increasingly being used is the high-flow nasal cannula (HFNC). This tool can provide up to 100% oxygen that is humidified, warmed, and flows with a maximum current of 60 L/min. A high FiO2 can be continuously given.[11] HFNC can improve oxygenation, reduce pharyngeal dead space, improve work of breathing, produce positive nasopharyngeal and tracheal pressure, decrease room air entrainment, and improve mucociliary clearance.[12],[13]

In acute respiratory failure and patients with respiratory distress, the use of HFNC decreases the mortality rate[14],[15] and the intubation rate.[13],[16] HFNC, as the first therapy in COVID-19 patients who experience respiratory failure, shows a 15% intubation rate. Clinical improvement was found in the first 1–2 h of use.[17] The World Health Organization, the Society of Critical Care Medicine, the European Society of Intensive Care Medicine, the Australian and New Zealand Intensive Care Society, and the Chinese Medical Association recommend the use of HFNC in COVID-19 patients with acute respiratory failure.[6],[18],[19],[20]

We choose to set an initial flow of 20–40 L/min (with a range of 5–60 L/min) with a 100% FiO2. If the respiratory rate and oxygenation were not improved, the flow can be increased gradually up to 60 L/min, adjusting to the patient's comfort. The flow and FiO2 can be reduced once the patients are stable and the clinical condition improves, and adequate oxygenation is reached. The SpO2/FiO2 ratio (the ROX index) can help clinicians predict the failure of HFNC use in acute respiratory failure. ROX values of <2.85, <3.47, and <3.85 in the first 2, 6, and 12 h of HFNC use are predictors of HFNC failure. Even so, an overall clinical assessment would still be a better tool to evaluate the efficacy of the management.[21]

Oxygen escalation

Holistic assessment for the severity of their respiratory distress is essential. For patients with moderate-to-severe dyspnea with a respiratory frequency of 20–30 ×/min, a SpO2 of <94% of room air, and a PO2/FiO2 of <300, oxygen therapy can be initially given through a nasal cannula up to 6 L/min, then titrated to a venturi mask up to 60% if it is needed, then titrated to a NRM up to 15 L/min, and finally to HFNC. However, all these modalities can also be given as a first-line oxygen therapy [Figure 1]. The evaluation of the therapeutic response should be done at least every 30 min in the 1st h and then every hour. If conventional oxygen does not provide clinical improvement, HFNC can be given. It is important to closely monitor patients in the first 2 h, taking into account the possibility of “silent hypoxemia,” especially in older patients.[22] In silent hypoxemia, the patient does not experience significant respiratory distress but shows low SpO2[5] If there is no clinical improvement, consider noninvasive or invasive mechanical ventilation. In patients who present with or experience worsening in the form of severe respiratory distress, decreased awareness, hemodynamic instability, and multiple high-risk conditions (diabetes mellitus, hypertension, cardiovascular diseases, old age, malignancy, or chronic lung disease), immediately intubate the patient and admit them to intensive care except when facilities are not available, or the patient refuses.[7]
Figure 1: Oxygen therapy algorithm for COVID-19 patients. RR: Respiratory rate; SpO2: Oxygen saturation; PaO2: Partial pressure of oxygen; FiO2: Fraction of inspired oxygen; L: Liter; HFNC: High-flow nasal cannula; NIV: Noninvasive ventilation

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Aerosol generating and risk of transmission

All patients with suspected and COVID-19 confirmed should ideally be treated in a negative pressure room, especially patients who are given oxygen therapy.[7] All oxygen therapy devices ranging from nasal cannulas, masks, or HFNC can generate aerosols.[23] Raboud et al. reported that 65% of health-care workers infected by the SARS virus are those who manipulate oxygen masks of SARS-positive patients.[24] Health-care workers needs to use personal protective equipment, especially N95 masks and protective goggles. Of course, a complete set of personal protective equipment with gloves, gowns, and face shields will be better. Patients on oxygen therapy should also be given a surgical mask to reduce the spread of droplets.[6],[7],[8],[23]

Hui et al. conducted a study to determine the dispersion distance of exhaled air from several oxygen therapy devices using the human mannequin model [Table 1]. Even with a low flow of 1 L/min, nasal cannulas can disperse exhaled air to a 30 cm distance. With a 5 L/min flow, the distance reaches 42 cm. Nonrebreathing masks with a flow of 6–12 L/min disperse exhaled air as far as 60–100 cm. The dispersion distance is not affected by lung conditions, whereas in the use of venturi masks, the dispersion distance of exhaled air from normal lungs is further than that of damaged lungs.[25] With HFNC, despite the high flow, the dispersion of exhaled air obtained from the mannequin test appeared not to be significantly different from other conventional oxygen therapy devices.[26] The risk of transmission is also lower than NIV.[24] In a healthy person, coughing up exhaled air can disperse it to a distance of 290 cm, further from the current recommendations for the patient physical distancing.[27] Therefore, if not placed in a negative pressure room, patients should be placed in separate rooms and/or equipped with surgical masks.
Table 1: Maximum dispersion distance of exhaled air when using an oxygen therapy device

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  Conclusions Top


Supplemental oxygen therapy is a life-saving supportive therapy in hypoxemic COVID-19 patients. Rational management of oxygen therapy includes the provision of initial therapy, followed by proper monitoring and escalation without delaying intubation and also the considerations of the health-care workers' protection and the risk of transmission.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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