A more comfortable, less expensive approach to high-flow oxygen delivery is likely to gain ground in adult ICUs over the next few years, buoyed by recent research showing somewhat better outcomes and no increased risks compared with current practice.
High-flow nasal cannulas (HFNCs), which are slightly larger than standard cannulas, deliver heated and humidified oxygen in greater volume and at higher pressure.
The cannulas have been on the market for about 15 years and have been most commonly used with infants and children, who tolerate them better than oxygen masks. But use of HFNCs in adults is likely to pick up following publication of 2 studies in June in the Journal of the American Medical Association (JAMA) and the New England Journal of Medicine (NEJM).
“This approach is probably going to change practice and seems to be changing it already,” said Gregory Schmidt, MD, professor of pulmonary, critical care, and occupational medicine at the University of Iowa Carver College of Medicine in Iowa City and director of critical care medicine.
How it works
HFNCs can deliver oxygen flow rates of 40 to 60 L/min (compared with up to 5 L/min for a standard cannula) and provide a level of pressure that reduces the work of breathing, while increasing the excretion of carbon dioxide.
Adoption for adult patients has been slow because noninvasive positive-pressure ventilation (NIPPV), delivered via a tight-fitting mask, has been the standard of care for hypoxemic patients who don't need endotracheal intubation but require pressure to help their breathing, and adults can typically handle wearing a mask even if they don't find it comfortable.
But HFNCs may provide a more comfortable option for some patients who aren't sick enough for intubation but aren't breathing well enough to get by with no help at all or a standard nasal cannula. Patients can talk, eat, and drink while receiving oxygen through HFNCs, and the humidification helps keep the nasal tissues from drying out or becoming irritated, as often happens with regular oxygen.
The JAMA study sought to measure how HFNCs compared with NIPPV masks for patient mortality and tolerability. It included 830 French patients who had undergone cardiothoracic surgery and had or were at risk for respiratory failure, requiring high-flow oxygen.
The patients were randomly assigned to receive oxygen through either HFNCs worn continuously or masks worn for at least 4 hours a day, 6 hours on average. The study found the 2 treatments equivalent in their effect on patients' health: There was no significant difference in mortality, and about 20% of the patients in both groups had to stop or switch to another method of oxygen delivery due to respiratory distress or inability to tolerate the treatment.
The NEJM study found slightly better outcomes with HFNCs than NIPPV or standard oxygen therapy delivered through a mask. Of the patients using HFNCs, 38% had to be intubated within 4 weeks, compared with 50% in the NIPPV group and 47% in the standard oxygen mask group. The high-flow nasal oxygen group also showed the most ventilator-free days and lowest 90-day mortality.
Putting it into practice
At University of Iowa Hospitals and Clinics, clinical experience has also found advantages to HFNCs. “We're seeing that some patients very quickly show improved respiratory rate and are more comfortable,” said Dr. Schmidt. “We see that, gosh, this stuff actually works. When people see that something works, they're inclined to use it, and this approach is simpler than the alternatives.”
Clinicians at the University of California San Francisco (UCSF) went so far as to test the cannulas on themselves and found a “big difference” in comfort compared with a mask. “You feel it, but it's not necessarily uncomfortable,” said Michael Matthay, MD, professor of medicine and anesthesia, a senior associate at the Cardiovascular Research Institute, and director of critical care medicine training at UCSF.
In an editorial accompanying the NEJM study, he advocated using HFNCs to treat patients without hypercapnia and with acute, severe hypoxemic respiratory failure in any hospital setting where patients can be carefully monitored.
“I think we'll see rapid growth” in adoption, Dr. Matthay said, adding that he sees no major side effects to be concerned about.
The technology may benefit several classes of patients, including those with pneumonia and acute heart failure, those who have had cardiac surgery or have recently come off a ventilator, and cancer patients with hypoxemia and dyspnea, according to Kenneth Nugent, MD, FACP, a professor of medicine at Texas Tech University Health Sciences Center in Lubbock.
HFNCs can particularly benefit patients on palliative care by making it easier for them to breathe and talk with loved ones. Many studies use dyspnea measures to evaluate the benefits of HFNCs, said Dr. Nugent, who last year co-authored a review article on HFNC in the American Journal of the Medical Sciences.
NIPPV is still the right choice for patients with hypercapnia, such as those with chronic obstructive pulmonary disease or severe asthma, according to Dr. Schmidt. “Because their primary problem is too much carbon dioxide rather than too little oxygen, an oxygen-based therapy is not necessarily a solution,” he said.
For mildly hypercapnic patients, especially those who aren't severely obese, it's possible that the slight increase in upper airway pressure associated with HFNCs could help at least a little, Dr. Nugent speculated. His review article called for more research in this area.
In addition to being more comfortable, HFNCs are considerably less expensive than NIPPV. At Texas Tech, the daily cost is at around $60, compared to about $1,200 for either mechanical ventilation or NIPPV, Dr. Nugent estimated. “Identifying patients who would benefit most with HFNC would definitely provide a clinical advantage and reduce costs,” he said.
Moreover, if ventilator days can be decreased, as the NEJM study indicated they might, HFNCs could reduce overall costs by cutting down the number of patients who are intubated, Dr. Matthay noted.
As with all oxygen therapies, patients on HFNCs should be closely monitored to make sure that oxygen levels increase and respiratory rate decreases, by tracking standard bedside parameters like respiratory rate, oxygen saturation, levels of distress and alertness, and synchronous movement of the chest wall and abdomen.
“It's important that once it is suspected that HFNC is not providing sufficient support, that either invasive or noninvasive mechanical ventilation should be initiated,” said Dr. Nugent.
Some investigators have expressed concern that HFNC use might delay intubation and potentially cause harm, but studies haven't found any such harm and have implemented effective strategies for making decisions about intubation, according to Dr. Nugent.
“Clinicians just need to remember that these patients may require intubation,” he said.