High-flow oxygen therapy via HFNC has been gaining momentum as trusted and reliable therapy.

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The use of high-flow oxygen therapy has been gaining more and more momentum as trusted and reliable therapy for the treatment of hypoxemia, moderate hypercapnia, and increased work of breathing. Complications as a result of respiratory failure have the potential to produce very serious and life-threatening outcomes. As it stands, healthcare providers are limited to the devices that can be used to treat hypoxic and hypercarbic respiratory failure.

This review aims to help gain more awareness of the benefits of using high-flow oxygen therapy as it relates to those suffering from respiratory failure. We will explore high flow nasal cannula (HFNC) devices, how they work, the type of patients who may benefit, as well as the different clinical areas it may be used.  We will explore the prevalence of respiratory failure including how it’s determined, how often it occurs, and some of the history surrounding this. We will look at the clinical ramifications of using HFNC when treating respiratory failure including the effects on length of stay, readmission rates, and mortality and morbidity.

Healthcare costs have become a major concern in American healthcare systems and this article will seek to discuss the different financial outcomes that may result from using HFNC to treat patients suffering from respiratory failure. By improving our knowledge of respiratory failure as well as HFNC therapy and its place among common healthcare devices, the amount of costly and not do desirable outcomes may therefore be diminished.

Respiratory failure is defined as a syndrome in which the respiratory system fails at either oxygenation or elimination of carbon dioxide.1 The resulting complications—such as an increase in the work of breathing, increase in respiratory rate, and low oxygen levels, to name a few—may lead to very severe and life-threatening situations.

HFNC therapy delivers conditioned gas through a nasal cannula at flow rates meeting or exceeding the patient’s inspiratory demand, therefore delivering a constant or fixed FiO2. HFNC has become more widely accepted and utilized as one of the first-line therapies for the treatment of respiratory failure. However, the question remains as to whether HFNC therapy has become an adequate alternative to noninvasive ventilation (NIV).

Noninvasive ventilation has long been the standard when treating patients with acute respiratory failure. Although this may hold true in severe cases, patients in respiratory failure who are identified early may benefit greatly from HFNC therapy.  Some of the difficulties associated with NIV include the use of a tight-fitting mask, which may seem daunting to someone with Claustrophobia and can lead to skin breakdown, the delivery of dry air if not humidified, and the limited  ability to communicate, take medications or eat meals.  Spoletini et al2 further support this in a study comparing NIV to HFNC on post-extubation patients.  They found patients often struggle with mask discomfort ultimately limiting the amount of time the device can be used.2

When using HFNC, gas is delivered through nasal prongs, small bore or large bore instead of a mask. This may lead to improved patient compliance while being treated for acute respiratory failure. Patients are able to verbally communicate, as well as eat and take their medications while receiving the therapy. The gas being delivered is humidified and distributed at body temperature adding to the patient’s comfort by preventing the drying of nasal mucosa. Respiratory failure is often accompanied by a high spontaneous inspiratory flow demand, as well as a high oxygen requirement. By delivering conditioned gas at flow rates of up to 40-60 LPM and dialing in a set FiO2, HFNC will not only meet but often exceed the patient’s demand. This in turn will limit room air entrainment ensuring a steady FiO2 delivery and a reduced work of breathing. Studies have also shown that ventilatory efficiency is also improved by the flushing out of anatomical dead space in the upper airway.2 The upper airway may then act as an oxygen reservoir, ultimately leading to lowered respiratory rates with less work of breathing.3

Specific to COPD exacerbation, questions remain. For instance, will HFNC treat any existing hypercapneic component effectively? In addition, what is the recommended threshold for pCO2, at which point you would be safe utilizing an HFNC system? These are unanswered questions and neither the current literature nor textbooks put a stake in the ground on a pCO2 value. It is our opinion that HFNC are well proven for patients in hypoxic respiratory failure and in fact should always be applied over the routine nonrebreather, which does not treat the physics related to shortness of breath in some patients. In fact, it should be considered that every patient on a high FiO2 device (such as a nonrebreather) be seen by a respiratory care practitioner to determine what would best meet the patient’s needs. There are many instances in which our patients have done extremely well on an HFNC and yet, a similar patient may need NIV or intubation. Considering the gold standards of care, the choice of therapy comes down to: Will I be doing harm? This is not an easy question to answer.

Respiratory failure is a critical scenario in which decisions at one point in time will clearly determine the outcome at another point in time.  The evolution of the event can be fast, and decisions must be made quickly. Many of our colleagues are very comfortable with treating COPD exacerbation and congestive heart failure exacerbation with HFNC therapy and yet others immediately apply NIV. To make the choice between the two, it should stand that very close patient monitoring is needed to determine any need for escalation of care. Key findings from the literature include:

  • Gaunt and Halub (2015) discovered “preliminary evidence that early use of HFNC is beneficial in a medical and trauma ICU population, as it was associated with decreased ICU and post-ICU lengths of stay and reduced incidence of adverse events.” They further suggested that “HFNC should be considered early in the ICU as first-line oxygen therapy”.4
  • Nashimura (2016) indicated “HFNC decreases breathing frequency and work of breathing and reduces the need for respiratory support escalation.” They continued: “Some important issues remain to be resolved, such as definitive indications for HFNC and criteria for timing the starting and stopping of HFNC and for escalating treatment. Despite these issues, HFNC has emerged as an innovative and effective modality for early treatment of adults with respiratory failure with diverse underlying diseases.”5
  • Francois et al concluded that “Among obese cardiothoracic surgery subjects with or without respiratory failure, the use of continuous HFNC compared to intermittent NIV (8/4 cm H2O) did not result in a worse rate of treatment failure. Because high-flow nasal cannula presents some advantages, it may be used instead of NIV in obese patients after cardiothoracic surgery.”6

HFNC versus NIV is much like one ventilation mode versus another, in that the evidence has been hard to gather due to many uncontrollable variables, limited number of studies, and studies with a smaller number of subjects. Anecdotal evidence exists for many of us who have applied the therapy to a variety of patient presentations. If we stop and think about what is best for the patient, it may be that we choose an HFNC device. However, that assumes we have a moment to think about it. Often, when the patient is hypoxic, struggling, and grabbing the bedrails for each breath, we revert to what we “know” works, that being NIV.
Staff should be encouraged to read the literature, think of the scenarios, and think critically about the when they might consider using HFNC therapy on their patient in respiratory failure. RT


Michael Provencher, MPH, RRT, is the director of Pulmonary Medicine and Neurosciences at Wentworth-Douglass Hospital (Dover, NH). Nicholas Nuccio, BS, RRT, is a staff respiratory therapist Wentworth-Douglass Hospital. For more information, contact [email protected]


References

  1. http://emedicine.medscape.com/article/167981-overview accessed on August 5th, 2017.
  2. Spoletini G, Garpestad E, Hill NS.  High-Flow Nasal Oxygen or Noninvasive Ventilation for Postextubation Hypoxemia Flow vs Pressure? JAMA. 2016; 315(13):1340-1342.
  3. Maggiore SM, Idone FA, Vaschetto R, et al. Nasal High-Flow versus Venturi Mask Oxygen Therapy after Extubation. Am J Respir Crit Care  2014; 190(3):282-288.
  4. Gaunt K, Halub M, Spilman S. High Flow Nasal Cannula in a Mixed Adult ICU. Respiratory Care2015; 60(10): 1383–1389.
  5. Nishimura M. High Flow Nasal Cannula Oxygen Therapy in Adults; Physiological Benefits, Indication, Clinical Benefits and Adverse Effects. Respiratory Care 2016;61(4):529-541.
  6. François Stéphan, Laurence Bérard, Saida Rézaiguia-Delclaux, Priscilla Amaru. High-Flow Nasal Cannula Therapy Versus Intermittent Noninvasive Ventilation in Obese Subjects After Cardiothoracic Surgery Respiratory Care Sep 2017, 62 (9) 1193-1202.