Author: CHOW Man Chun, HKECMED Nurse Consultant (Respiratory Care)
Acute hypoxemic respiratory failure is a common phenomenon for COVID-19 patients during the pandemic. It can cause respiratory muscle fatigue as well as the loss of airway cells that play a role in the physiological humidification of air, resulting in mucus plugs.
High Flow Nasal Oxygenation (HFNO) is an alternative modality to standard oxygen therapy which is the result of process to provide a system that could deliver both heated and humidified oxygen at high flows. It has a positive role in increasing ventilatory efficiency by a variety of mechanisms. It can constantly flush out carbon dioxide from the nasopharynx, which eliminates the dead space in proportion to flushed-out volume, increasing inspiratory fraction of oxygen (FiO2) (1-3). The effects of HFNO on positive end-expiratory pressure (PEEP) (4-7), which has the potential for application in ICU and perioperative settings as it prevents the cyclical opening and collapsing of alveoli. (8) The PEEP effect increases tidal volume and end-expiratory lung volume and decreases the respiratory rate and left ventricular afterload, while preserving minute ventilation. (9-11)
Easy set up and monitoring allow patients to stay in general unit for treatment. The connections of chamber kit set to sterile water and heated breathing tube to optiflow nasal cannula is the only set up for HFNO. There are three parameters in setting, i.e. Temperature (31℃, 34℃ & 37℃), Flow rate (10-60L/min) & Oxygen concentration% (21%-100%).
Usually, patients with respiratory failure required mechanical assisted ventilation, either invasive or non-invasive, to maintain oxygenation and adequate alveolar ventilation by reduction their work of breathing with pressure support.
There are reports that with the use of HFNO, reduction of intubation rate, reintubation rate and mortality rate when compare with face mask oxygen. (12-14) The need of mechanical ventilation support is also significantly reduced in recent studies on severe COVID-19 patients. (15-16) With the advantage of heating and humidification benefit, better patient comfort and tolerance of therapy leading to better therapeutic outcome. (13, 17)
Möller W, Celik G, Feng S, et al. Nasal high flow clears anatomical dead space in upper airway models. Journal of applied physiology (Bethesda, Md.: 1985). 2015;118(12):1525-1532. https://www.proquest.com/scholarly-journals/nasal-high-flow-clears-anatomical-dead-space/docview/1704351689/se-2.
Ritchie JE, Williams AB, Gerard C, Hockey H. Evaluation of a humidified nasal high-flow oxygen system, using oxygraphy, capnography and measurement of upper airway pressures. Anaesth Intensive Care. 2011;39(6):1103-10. https://www.proquest.com/scholarly-journals/evaluation-humidified-nasal-high-flow-oxygen/docview/905897792/se-2.
Masclans JR, Roca O. High-Flow Oxygen Therapy in Acute Respiratory Failure. Clin Pulm Med. 2012; 19(3):127-30.
Kilgour, E., Rankin, N., Ryan, S. et al. Mucociliary function deteriorates in the clinical range of inspired air temperature and humidity. Intensive Care Med 30, 1491–1494 (2004). https://doi.org/10.1007/s00134-004-2235-3
Chidekel A, Zhu Y, Wang J, Mosko J J, Rodriguez E, Shaffer T H. “The Effects of Gas Humidification with High-Flow Nasal Cannula on Cultured Human Airway Epithelial Cells”, Pulmonary Medicine, vol. 2012, Article ID 380686, 8 pages, 2012. https://doi.org/10.1155/2012/380686
Groves N, Tobin A. High flow nasal oxygen generates positive airway pressure in adult volunteers. Aust Crit Care. 2007; 20(4): 126-131 https://doi.org/10.1016/j.aucc.2007.08.001
Ritchie J E, Williams A B, Gerard C, et al. Evaluation of a humidified nasal high-flow oxygen system, using oxygraphy, capnography and measurement of upper airway pressures. Anaesthesia and intensive care, 2011, 39(6): 1103-1110.
Vargas M, Sutherasan Y, Gregoretti C, Pelosi P. “PEEP Role in ICU and Operating Room: From Pathophysiology to Clinical Practice”, The Scientific World Journal, vol. 2014, Article ID 852356, 8 pages, 2014.
Corley A, Caruana LR, Barnett AG, et al. Oxygen delivery through high-flow nasal cannula increase end-expiratory lung volume and reduce respiratory rate in post-cardiac surgical patients. Br J Anaesth. 2011; 107(6): 998-1044
Mündel T, Feng S, Tatkov S, Schneider H. Mechanisms of nasal high flow on ventilation during wakefulness and sleep. J Appl Physiol. 2013 Apr;114(8):1058-65.
Riera J, Pérez P, Cortés J, et al (2013) Effect of high-flow nasal cannula and body position on end-expiratory lung volume: A cohort study using electrical impedance tomography. Respir Care. Apr 2013, 58 (4) 589-596
Frat J-P, Thille AW, Mercat A, et al. High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N Engl J Med 2015;372:2185-96.
Maggiore SM, Idone FA, Vaschetto R, et al. Nasal high-flow versus Venturi mask oxygen therapy after extubation: effects on oxygenation, comfort, and clinical outcome. Am J Respir Crit Care Med 2014; 190: 282-8.
Hernández G, Vaquero C, González P, et al. Effect of postextubation high-flow nasal cannula vs conventional oxygen therapy on reintubation in low-risk patients: a randomized clinical trial. JAMA. 2016;315(13):1354-1361.
Patel M, Gangemi A, Marron R, et al. Retrospective analysis of high flow nasal therapy in COVID-19- related moderate-to-severe hypoxaemic respiratory failure. BMJ open resp res 2020;7:e000650. Doi:10.1136/ bmjresp-2020-000650
Ospina-Tascón GA, Calderón-Tapia LE, García AF, et al. Effect of High-Flow Oxygen Therapy vs Conventional Oxygen Therapy on Invasive Mechanical Ventilation and Clinical Recovery in Patients With Severe COVID-19: A Randomized Clinical Trial. JAMA. 2021;326(21):2161–2171. doi:10.1001/jama.2021.20714
Sztrymf, B., Messika, J., Bertrand, F. et al. Beneficial effects of humidified high flow nasal oxygen in critical care patients: a prospective pilot study. Intensive Care Med 37, 1780 (2011).