|Year : 2020 | Volume
| Issue : 5 | Page : 3-7
Oxygen delivery devices in Covid-19 patients: Review and recommendation
Avishek Roy, Abhishek Singh, Puneet Khanna
Department of Anesthesiology, Pain Medicine and Critical Care, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||26-Apr-2020|
|Date of Decision||14-Apr-2020|
|Date of Acceptance||25-May-2020|
|Date of Web Publication||13-Jul-2020|
Dr. Abhishek Singh
AB8, Eight Floor, Main Building, Ansari Nagar East, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has become a matter of concern all over the world. This virus caused acute respiratory distress syndrome(ARDS) in almost 67% of patients, with 71% of total patients requiring mechanical ventilation. Oxygen therapy is prudent for patients suffering fromSARS-CoV-2 at different stages of the disease. The choice of different oxygen delivery devices depends on the patient's status and its availability. In this review we will discuss the pros and cons of several oxygen delivery devices, as well as the safety precautions and personal protective equipments.
Keywords: Coronavirus pandemic, oxygen delivery devices, prevention of transmission
|How to cite this article:|
Roy A, Singh A, Khanna P. Oxygen delivery devices in Covid-19 patients: Review and recommendation. Bali J Anaesthesiol 2020;4, Suppl S1:3-7
|How to cite this URL:|
Roy A, Singh A, Khanna P. Oxygen delivery devices in Covid-19 patients: Review and recommendation. Bali J Anaesthesiol [serial online] 2020 [cited 2022 Aug 10];4, Suppl S1:3-7. Available from: https://www.bjoaonline.com/text.asp?2020/4/5/3/289550
| Introduction|| |
The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic has become a matter of concern for general public and health-care professionals. As per the WHO, until March 24, 2020, among 2,549,632 confirmed cases, this virus has led to the death of 175,825 patients. Among 72,314 confirmed SARS-CoV-2 patients in China, 81% had mild symptoms, nearly 14% develop severe symptoms such as dyspnea and hypoxia, 5% became critically ill, and 1%–3% required intubation. Among critically ill patients, this virus caused acute respiratory distress syndrome (ARDS) in almost 67% of patients, with 71% of total patients requiring mechanical ventilation with a 28-day mortality of 61.5%. Overall case fatality rate ranges between 2.3 and 7.2% among various countries.
Oxygen therapy is prudent for patients suffering from SARS-CoV-2 at different stages of the disease. Oxygen delivered through different devices creates different amounts of aerosols and pose the threat of nosocomial infection to health-care workers (HCW) and other patients. Although the exact definitions of droplets and aerosols are blurry, droplets can be considered to be larger, causing a direct person-to-person spread within close proximity, whereas aerosols are smaller suspended infective particles causing airborne spread., Larger aerosols of size ≥10 μm are generated from the larynx and upper airway during coughing, sneezing, and during aerosol-generating procedures (AGPs), such as intubation, bronchoscopy, bag-mask ventilation, and tracheotomy. Although the choice of different oxygen delivery devices depends on the patient's status and availability, their use has to be weighed against their aerosol-generating potential.
Here, we will discuss the pros and cons of different oxygen delivery devices. All of the above procedures require safety precautions, such as personal-protective equipment (PPE) for HCWs, negative pressure isolation rooms, proper donning, and doffing areas.
| Low Flow and Low-Performance Devices|| |
Nasal cannula and nasal catheters and Blow over devices
The nasal cannula and catheters provide low to a moderate fraction of inspired oxygen (FiO2) of 0.240.4 at oxygen flows of 1–6 L/min, as higher flows are associated with nasal crusting and irritation. The nasal cannula has the advantage that it can be used with a face mask/N95 mask. Blow over devices are made with the help of masks or paper drinking cups and are used for infants and small children. They provide FiO2 <0.3 at flows of at least 10 L/min.
All these devices produce aerosols. The nasal cannula can cause the aerosol spread of up to 0.42 m laterally and up to 1 m toward the end of the bed. While in quiet patients, flows of 1 L/min cause aerosol spread up to 0.3 m, the distance increases to 0.42 m in patients with respiratory distress requiring higher flows of 5 L/min. An aerosol spread can further increase to 0.8 m with coughing and sneezing.,
In mild-to-moderate symptomatic patients, nasal cannula and blow over oxygen can be used at flows of 4–6 L/min, with the patient's face covered with N95 or equivalent face mask along with other precautions applicable for AGPs.
Simple face mask and nebulizers
Simple Hudson facemask delivers FiO2 of 0.35–0.5 at flows of 5–8 L/min and is used for the moderate duration of oxygen therapy, for example, postanesthesia, after extubation in the intensive care unit. Nebulizers function and form droplets of different sizes to deliver the drugs. Depending on different manufacturers, nebulizers generate the droplets of varying sizes.
In normal quiet-breathing patients requiring 4 L/min of oxygen flows, a simple face mask may lead to the aerosol spread of up to 0.2 m. However, in sick patients requiring flows ≥10 L/min, the maximal aerosol spread can occur beyond 0.4 m., Simple face mask application can be difficult for disoriented patients and with N95 respirators. With the advent of this pandemic, nebulizers have to be used with caution., In human's lung simulation study, jet nebulization caused aerosol spread up to 0.45 m in normal healthy lungs, while in severely injured lungs, aerosol spread occurred beyond 0.8 m. Patients who require nebulizers mostly have asthma, or chronic obstructive pulmonary disease (COPD) as the underlying disease, and therefore, more likely to cough, which, combined with high flows of jet nebulizer produces a huge number of aerosols. Although debatable, nebulization with normal saline may act to heat the air-fluid interface of the airway and increase droplet size thus decreasing the distance covered.
Only in co-operative patients with mild-to-moderate respiratory distress, facemask can be used. Open nebulizers should be avoided; rather a metered-dose inhaler with spacer device or manual in-line nebulization should be used. Nebulization with normal saline may be used to increase droplet size and thus prevent distant spread of droplets.
| High Flow Devices, Reservoirs, and Noninvasive Ventilation|| |
Partial rebreathing mask, nonrebreathing mask, and venturi mask
All require higher flows of at least 10 L/min. Partial rebreathing mask having a reservoir bag leads to some air entrainment and can deliver FiO2 of 0.4–0.7 at 10–15 L/min flows. Nonrebreathing masks (NRMs) have an additional one-way valve that prevents room air entrainment and rebreathing of exhaled gases. It can deliver FiO2 above 0.8, provided there is a good mask fit, and airflow is more than three times of minute ventilation. Venturi masks (VM) blend oxygen and room air depending on the desired FiO2 but require moderate to high flows.
With a tight-fitting mask, the aerosol spread is only about 0.1 m for NRMs. VMs generate aerosol up to 0.4 m at desired FiO2 of 0.24 and up to 0.33 m at desired FiO2 of 0.4. Exhalation filters can be used to curtail the spread of aerosols in above methods.
Rebreathing masks can be used to provide moderate-to-high FiO2 for moderate duration, e.g., before intubation and postextubation. NRMs are the preferred mode for preoxygenation before intubation. VMs can be used to provide lower and fixed FiO2. Nasal cannula combined with NRM can be used to provide higher FiO2.
High-flow nasal cannula and OxyMask
High-flow nasal cannula (HFNC) provides heated humidified oxygen at flows from 10 L/min up to 50 L/min. At high flows, it provides positive pressure. It has been used in the conditions such as respiratory distress, preoxygenation, and apneic diffusion of oxygen in airway procedures, in both adult and pediatric age groups. A combination of HFNC and noninvasive ventilation (NIV) mask has shown to reduce re-intubation rates at day 7 postextubation in critically ill patients, as compared to high-flow nasal oxygen alone. Using HFNC interchangeably with NIV can also reduce the patient's discomfort as compared to using NIV alone. Although widely used in patients suffering from SARS-CoV-2 pneumonia, around 41% of patients with PaO2/FiO2(P/F) ratio ≤200 mmHg had failure with HFNC therapy and required either NIV or intubation. OxyMask is a specially designed mask used to provide higher FiO2, although initial studies showed its superior efficacy as compared to HFNC, this notion has been questioned, as flows above 20 L/min haven't shown to increase FiO2.
By increasing the flows from 10 L/min to 60 L/min, HFNC has shown to increase aerosol spread from 65 to 172 mm in the sagittal plane. It can also cause air leakage around the mask up to 620 mm. Some recommend avoiding the use of HFNC. Aerosol dispersion can be lessened using a surgical mask and asking patients to breathe through nose with mouth closed. In a human patient-simulator model, use of a surgical mask during normal cough reduced aerosol spread from 68 cm to 30 cm, and further reduction of diffusion distance was noted with the use of N95 mask.
HFNC can be used to provide oxygen, preferably in patients with acute respiratory failure with P/F ratio ≥200 mm Hg. It should be ensured that the nasal reservoir used with HFNC is snugly fit, and the patients are instructed to wear surgical/N95 masks and breathe nasally. OxyMask should be used at flows ≤20 L/min.
Both Continuous positive airway pressure (CPAP) and Bilevel positive airway pressure (BiPAP) have been used for the acute exacerbation of COPD (AECOPD) and acute congestive heart failure (ACHF). Patients with a P/F ratio of 100–200 mm Hg and sequential organ failure assessment score ≤2 should be treated with BiPAP therapy with some modifications. Those patients in whom HFNC therapy failed, NIV caused an increase in P/F ratio and a decrease in respiratory rate; thus, alleviating intubation. However, in severely symptomatic patients with viral pneumonia, its use is limited as it may only delay intubation and lead to mortality. Furthermore, the lack of properly fitting masks and accessories preclude the use of NIV in many settings.
CPAP of 5–10 cm H2O may lead to aerosol generation up to 332 mm depending on different manufacturers. NIV generates aerosols of more than 10 μm diameter, especially in patients with symptoms. With increasing inspiratory pressures, BiPAP leads to significant aerosol generation. At constant expiratory pressures of 4 cm H2O, increasing inspiratory pressures from 10 cm to 18 cm H2O increases aerosol spread from 0.65 m to 0.85 m. Whisper swivel adapter, a one-way valve to prevent rebreathing, further increases aerosol spread beyond 1 m. In comparison to oral/nasal masks, the use of a helmet for NIV can curtail the aerosol spread. Adequate precautions should be taken before applying NIV.
NIV can be used in the conditions such as cooperative patients with AECOPD or ACHF due to COVID infection, taking all precautions related to the airborne spread. Inspiratory pressures should be kept at a minimum level, preferably ≤10 cm H2O. Air leak should be minimized by the use of snuggle-fitting masks or helmet. Whisper swivel adapter and vented masks should be avoided. Breathing circuits should be used with exhalation port high-efficiency particulate (HEPA) filters. In addition to the above devices, chest physiotherapy and compression can lead to droplet generation of size ≥10 μm, and thus, should be avoided in the absence of adequate health precautions.
| Bag-Mask Ventilation, Supraglottic Devices, and Intubation|| |
Bag-mask ventilation (BMV) is done before intubation, especially in apneic patients. The use of supraglottic devices is still being advocated in difficult airway scenarios., Although there are no specific guidelines for intubation in SARS-CoV-2 patients, keeping a low threshold for intubation is advised. Intubation is generally advised in the following scenarios: rapid progression over hours, lack of improvement with noninvasive methods, hypercapnia, hemodynamic instability or multiorgan dysfunction, and altered neutrophil-lymphocyte ratio. As much as 1%–3% of total infected cases and 15% of total patients requiring some form of oxygen therapy were intubated.,
Bag and mask ventilation, as well as intubation, leads to the generation of significant amounts of aerosols. Intubation has the highest hazard ratio for aerosol spread to HCWs. Other intubation-associated procedures such as placement of nasogastric tube have a lesser chance of aerosol spread. Supraglottic devices should be preferred to BMV to provide positive pressure ventilation as they generate lesser aerosols as compared to BMV. Experienced personnel is less likely to spread aerosols during the airway management. Other modalities such as providing continuous suction rather than intermittent suction, administration of sedatives or paralytic agents to reduce cough in patients, have shown to reduce aerosol spread.
For lessening aerosol spread during intubation and mechanical ventilation, methods such as head-up position, rapid sequence induction, use nonrebreathing masks for preoxygenation, use of supraglottic devices instead of BMV for positive pressure ventilation, minimizing ventilator disconnections, use of in-line suction and nebulization, ensuring proper cuff seal, using two HEPA/heat moist exchanger filters, for example, one between Y-piece and patient end and another at the expiratory port, decreasing number of machine checks and change of suction tubing, should be advocated. During extubation, applying lignocaine jelly over the cuff of an endotracheal tube or covering a wet-gauge piece over the patient's mouth might decrease aerosol spread. Extubation should only be done only when the viral load has decreased, and the risk of aerosol spread is minimized. Flush of any kind should be avoided.
In the absence of NIV with closed circuit and NRMs, gentle bag and mask ventilation with low-tidal volume, using both thenar prominence to create a good seal and using two filters, can significantly reduce aerosol spread as well as recontamination.
| Conclusion|| |
Oxygen therapy is a major pillar in treating patients suffering from SARS-CoV-2 infection. The use of individual oxygen delivery methods should be tailored to individual patient needs, their availability. [Table 1] shows the maximum exhaled air dispersion distance through different oxygen administration and ventilatory support strategies. [Figure 1] throws some light on how to choose appropriate oxygen delivery devices depending on the patient's clinical condition. Although the aerosol-generating potential poses a threat to HCWs, their use is indispensable in low-resource setup where ICU beds and ventilators are limited in number. In selected patients, by reducing the work of breathing, these devices might alleviate the need for ventilators and possibly lead to lesser aerosol generation due to the reduction in flow requirements. Even in patients ARDS, prone positioning along with NIV/HFNC has been found useful.
Nonetheless, proper single patient negative pressure isolation room, along with the provision of adequate PPEs for HCWs and other methods of preventing viral spread, is of utmost importance.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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