High flow oxygen therapy combines several physiologic effects: Improved oxygenation, reduced inspiratory effort and work of breathing, improved lung mechanics, increased end-expiratory lung volumes (EELV), probably due to the positive end-expiratory pressure (PEEP) effect, increased carbon dioxide (CO2) clearance by washout of anatomic dead space, and improved comfort (1, 2).
The PEEP effect and the decrease in in respiratory rate are flow-dependent and better with higher flow rates (3, 4, 5, 6). However, the decrease in PaCO2 and minute ventilation are achieved at 30 l/min and do not change at higher flows (3). Until now, settings for flow and temperature have been heterogeneous for adult patients and what they perceive as comfortable varies greatly. This suggests that the therapy might benefit from more personalized rather than standardized settings (7).
Initial settings and adjustments
Flow: While many of the targeted physiologic variables show the most benefit at higher flows, patient comfort and compliance to therapy are key factors that should not be ignored. The set flow should take into consideration the severity of the patient’s condition.
Although there is no standard way to set the flow, an approach now used frequently in clinical practice is to initiate with a minimum flow of 30 l/min, and monitor dyspnea and the respiratory rate. If there is no improvement, the flow can be titrated according to patient comfort. You can increase it in increments of 10 l/min up to 60 l/min, and monitor the patient’s clinical condition. Note that any discomfort is usually due to the velocity of gas rather than the flow itself, and may be eased by using a large-bore cannula.
Temperature: In order to optimize the humidification effect, the temperature should be set at 37°C.
Oxygen: Oxygen is adjusted to maintain SpO2 within target ranges of 92%-96% for most patients and 88%-92% for patients with chronic respiratory disease (8, 9).
This bedside tip is based on the example of high flow oxygen therapy with Hamilton Medical ventilators*, however the information applies to the use of high flow oxygen therapy in general.
* Not all features or ventilators are available in all markets.
- Mauri T, Turrini C, Eronia N, Grasselli G, Volta CA, et al. Physiologic Effects of High-Flow Nasal Cannula in Acute Hypoxemic Respiratory Failure. Am J Respir Crit Care Med. 2017 May 1;195(9):1207-1215 (abstract).
- Goligher EC, Slutsky AS. Not Just Oxygen? Mechanisms of Benefit from High-Flow Nasal Cannula in Hypoxemic Respiratory Failure. Am J Respir Crit Care Med. 2017 May 1;195(9):1128-1131.
- Mauri T, Alban L, Turrini C, Cambiaghi B, Carlesso E, Taccone P, et al. Optimum support by high-flow nasal cannula in acute hypoxemic respiratory failure: effects of increasing flow rates. Intensive Care Med. 2017 Jul 31 [Epub ahead of print] (abstract).
- Parke RL, Bloch A, McGuinness SP. Effect of Very-High-Flow Nasal Therapy on Airway Pressure and End-Expiratory Lung Impedance in Healthy Volunteers. Respir Care. 2015 Oct;60(10):1397-403.
- Pisani L, Fasano L, Corcione N, Comellini V, Musti MA, Brandao M, et al. Change in pulmonary mechanics and the effect on breathing pattern of high flow oxygen therapy in stable hypercapnic COPD. Thorax. 2017 Apr;72(4):373-375 (abstract).
- Luo JC, Lu MS, Zhao ZH, Jiang W, Xu B, Weng L, et al. Positive End-Expiratory Pressure Effect of 3 High-Flow Nasal Cannula Devices. Respir Care. 2017 Jul;62(7):888-895 (abstract).
- Mauri, T., Galazzi, A., Binda, F. et al. Impact of flow and temperature on patient comfort during respiratory support by high-flow nasal cannula. Crit Care 22, 120 (2018).
- O'Driscoll BR, Howard LS, Davison AG; British Thoracic Society. BTS guideline for emergency oxygen use in adult patients. Thorax 2008;63:vi1-68.
- Beasley R, Chien J, Douglas J, Eastlake L, Farah C, King G, et al. Thoracic Society of Australia and New Zealand oxygen guidelines for acute oxygen use in adults: 'Swimming between the flags'. Respirology 2015;20:1182-91.
- High flow oxygen therapy after extubation
- Post-extubation respiratory failure: Is high flow nasal oxygen sufficient to prevent reintubation?
- Can we predict failure of HFNC in patients with acute hypoxemic respiratory failure?
The content of this newsletter is for informational purposes only and is not intended to be a substitute for professional training or for standard treatment guidelines in your facility. Any recommendations made in this newsletter with respect to clinical practice or the use of specific products, technology or therapies represent the personal opinion of the author only, and may not be considered as official recommendations made by Hamilton Medical AG. Hamilton Medical AG provides no warranty with respect to the information contained in this newsletter and reliance on any part of this information is solely at your own risk.