|Year : 2020 | Volume
| Issue : 2 | Page : 57-59
High-flow nasal cannula: Can it be a saviour in the present COVID-19 pandemic?
Manikant Lodaya1, Sumalatha Radhakrishna Shetty2
1 Consultant Anaesthesiologist and Intensivist, Hubli, Karnataka, India
2 Department of Anaesthesiology and Critical Care, K S Hegde Medical Academy, Nitte DU, Mangaluru, Karnataka, India
|Date of Submission||11-Aug-2020|
|Date of Acceptance||13-Aug-2020|
|Date of Web Publication||30-Aug-2020|
Dr. Sumalatha Radhakrishna Shetty
#-5-514/2, Suraj, Kadri Mundan, Bejai, Mangaluru - 575 004, Karnataka
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Lodaya M, Shetty SR. High-flow nasal cannula: Can it be a saviour in the present COVID-19 pandemic?. Airway 2020;3:57-9
|How to cite this URL:|
Lodaya M, Shetty SR. High-flow nasal cannula: Can it be a saviour in the present COVID-19 pandemic?. Airway [serial online] 2020 [cited 2020 Oct 19];3:57-9. Available from: https://www.arwy.org/text.asp?2020/3/2/57/293967
High-flow nasal cannula (HFNC), initially used in paediatrics for newborn babies, has now become an integral part in the intensive care unit (ICU), particularly in the COVID-19 pandemic that is taking its toll both on the population and the healthcare system. The COVID-19 pandemic has also educated the masses about HFNC. It is probably appropriate to have an Editorial and a Review Article on HFNC at this juncture to analyse, evaluate and formulate guidelines for the use of HFNC. The article on HFNC in this issue covers the principles and the multitude of benefits in the use of HFNC.
HFNC components are a flow generator providing gas flow rates up to 60 l/min, an air–oxygen blender which regulates FIO2 from 21% to 100% and a humidifier which provides a saturated gas mixture at a temperature of 31°C to 37°C which is delivered through a heated tubing to minimise condensation interfaced with the patient via a wide-bore nasal prong. Even though it would be appropriate to call it a high-flow nasal oxygen system (as this would indicate that oxygen is being provided in high concentration), the term HFNC still continues as it was initially introduced.
HFNC provides remarkably high flow of blended air with minimal oxygen dilution and washes out air from the dead space., This cannot be achieved with the ordinary nasal cannula even with a flow in the range of 10 to 15 L/min or a non-rebreathing mask. HFNC often helps in avoiding tracheal intubation and mechanical ventilation, which in many cases would be beneficial to the patient. This could help in early recovery with lesser deleterious effects on the respiratory and cardiovascular systems, and a shorter ICU stay. Further evaluation of HFNC has revealed many other benefits with no major disadvantages.
The HFNC system provides warmed and humidified air to the patient, preventing airway inflammation. This function is performed by the humidifier and not the cannula per se in most of the conventional oxygen therapy (COT) devices apart from the classical venturi devices; high flows are not achieved and humidification occurs in the native respiratory tract through the normal physiologic process. Because of the high flows involved in HFNC, active humidification is necessary as the nose and upper respiratory tract would be unable to cope with such high flows of dry gases.
The high flow offered by this system creates some sort of positive end-expiratory pressure, particularly with the mouth closed. Though this is as small as about 3–4 cm H2O, it could still help to prevent the collapse of the alveoli though it would be too low to recruit collapsed alveoli.
The HFNC system is also lightweight and more acceptable to patients than noninvasive ventilation (NIV) with a tight-fitting mask. HFNC gives the patient the freedom to speak and eat while it removes the claustrophobia created by a tight-fitting mask interface during NIV.
HFNC is a simple setup and can be easily managed even by nursing staff. Even as we point out the advantages of HFNC, we need to be aware of the disadvantages of the same. The easy setting and its handiness might lead to unnecessary usage in patients without weighing the risks against the benefits. In addition, one of its advantages could turn into a disadvantage as intubation could be delayed because oxygenation would not be affected early. The delay in intubation could increase mortality as appropriate respiratory care may not be provided in time.
With new evidence coming up about COVID-19 management strategies, we are constantly trying to update ourselves in its management. Currently, the debate is on early versus late intubation and use of NIV versus invasive ventilation. HFNC has been added to the clinical management of COVID-19 patients as an additional line of treatment if hypoxia cannot be alleviated by COT.
This modality of treatment was earlier used for H1N1 infections, and it was observed that none of the medical staff got infected. COVID-19 is also a highly infective and an airborne viral disease. Concerns have been raised regarding aerosol generation during HFNC as the statement from the World Health Organisation recommends using airborne precautions during the treatment of COVID-19 patients. With a proper fitting nasal cannula, the aerosol generation is minimal, thus increasing its popularity. Even though some studies have shown low risk of aerosol spread, it is advisable to use HFNC in a negative pressure setting with the patient wearing a surgical mask. In addition, healthcare workers caring for such patients should wear personal protective equipment.
At present, HFNC for COVID-19 patients is advised with necessary precautions to avoid airborne spread in patients with mild-to-moderate conditions, avoiding intubation and related complications. With the minimal staff presence becoming mandatory in this highly infectious viral disease, the simplicity of this equipment makes it easy to handle.
The large amounts of oxygen that these systems utilise may impose a severe impediment on healthcare facilities, particularly if many patients are receiving HFNC therapy at the same time. Hospitals that are using oxygen concentrators may not be able to deliver such high flows if several HFNC units are in use simultaneously. In addition, the need to install the HFNC machine can impose an additional financial burden on our hospitals which are already working under the clinical stress of handling patients with the COVID-19 infection.
The authors have enumerated the different uses of HFNC and the role it can also play in the anaesthetic management of patients. The one use of HFNC that interests us is its ability to increase the time to desaturate when used for preoxygenation. This could play a major role in preventing desaturation particularly in physiologically compromised patients like the ones we see in this pandemic.,
HFNC has no significantly greater advantage over NIV on the physiological functions of the body such as carbon dioxide removal and reducing the work of breathing although few studies have shown some effect. Significant advantage of HFNC is seen in terms of the patient's ability to speak and eat without affecting oxygenation, and the fact that it causes less discomfort for the patient. However, it is imperative to realise that when a couple of HFNC units are used simultaneously in smaller hospitals like in our country, oxygen cylinders and tanks can be depleted quite rapidly.
It is very essential for the nasal cannulae to fit well within the nares for it to function properly. Any leak could negate the advantage of peak flow delivery and hence oxygenation. Loose-fitting nasal cannulae could also generate aerosols which in this COVID-19 pandemic can have deleterious effects on our healthcare workers. Just like we ensure a proper fit of an N95 mask, these patients require properly fitting nasal cannulae to avoid this aerosol generation.
Some patients can easily dislodge the cannulae from the nose, which could be missed unless they are monitored closely. In this pandemic, with lesser healthcare workers available, such an event might go unnoticed and to maintain oxygen saturation, they may keep on increasing the inspired oxygen concentration. There are no leak alarms in the HFNC as it is by design a leaky circuit, unlike NIV.
HFNC is a new modality of respiratory therapy, particularly so in the Indian context. The advantages and disadvantages are to be validated for routine use. The guidelines for its use in COVID-19, the advantage of delaying intubation and its ability to maintain safe oxygenation have made it a novel and much-desired mode of ventilation.
At present, we have the option of availing COT, NIV and HFNC; HFNC has been shown to be advantageous over COT, while it is comparable with NIV. While most of the conventional ventilators have NIV mode, HFNC must be set anew and can be a financial commitment in these difficult times. Prospective studies need to evaluate the risk–benefits of HFNC, and guidelines for its initiation, monitoring and weaning need to be created before this modality of treatment becomes established in respiratory care.
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