Three ways to wean patients off high-flow oxygen worked about equally well

When doctors take a critically ill patient off high-flow oxygen, there is no settled recipe for how to do it — whether to ease off the flow first, dial down the oxygen first, or reduce both together. A new randomised trial compared all three and found, in short, that it does not appear to matter much: all three strategies got patients off support at similar rates [s1]. A result showing "no difference" is easy to overlook, but here it is useful, because it frees clinicians from fussing over a choice the data say is roughly a wash.

High-flow nasal cannula (HFNC) delivers a warmed, humidified blend of air and oxygen through soft nasal prongs at rates far above ordinary oxygen tubing. It has become a mainstay of intensive care for patients in respiratory distress who are not on a ventilator. Weaning is the process of stepping that support back down as a patient recovers, and the two dials a clinician can turn are the flow rate and the fraction of inspired oxygen. Which to lower first, and how fast, has largely been a matter of local habit [s1].

What the trial did

The study, known as SLOWH, was a multicentre randomised controlled trial run from December 2022 to August 2024 [s1]. It enrolled adults aged 18 or older in the intensive care unit who had met the criteria for weaning after being placed on HFNC [s1]. Patients were randomly assigned — using a computer-generated sequence prepared by an independent statistician blinded to the researchers and participants — to one of three approaches: reducing the flow first, reducing the oxygen fraction first, or reducing both simultaneously [s1]. The primary outcome was the weaning success rate, defined as a successful switch to conventional oxygen therapy without needing HFNC again, without non-invasive ventilation, and without a breathing tube within 24 hours [s1].

What it found

Of 102 patients drawn from three tertiary-care hospitals, 15 were excluded, leaving 87 who completed the trial: 31 in the flow-first group (52% male), 26 in the oxygen-first group (77% male), and 30 in the simultaneous group (53% male) [s1]. Weaning succeeded in 94% of the flow-first group, 81% of the oxygen-first group, and 77% of the simultaneous group — numerically different but not statistically so, with a p-value of 0.15 [s1]. How long weaning took was also similar: median durations were 31.0 hours (interquartile range 29.0 to 45.8) with flow first, 29.5 hours (28.0 to 60.4) with oxygen first, and 29.5 hours (26.5 to 45.0) with both at once, with no significant difference between groups (p=0.87) [s1]. The authors' conclusion is straightforward: none of the three strategies beat the others on either success or speed [s1].

How to read it

The caveats come first, because they shape everything else. This was a small trial — 87 patients analysed across three arms means fewer than 31 people per group — and a study that size cannot reliably detect a modest advantage even if one exists [s1]. The 94%-versus-77% spread looks large to the eye, and it is entirely possible that a bigger trial would turn one of these strategies into a genuine winner; the honest statement is that this study could not tell them apart, not that they are proven identical. The single-region, three-hospital setting also limits how far the result travels.

With those limits in mind, the practical message still holds. For a decision clinicians make every day, a well-conducted randomised trial found no signal that the order of weaning changes whether a patient succeeds or how quickly, which supports letting bedside judgment and patient comfort guide the approach rather than a rigid protocol [s1]. Related coverage has looked at a trial of conservative versus liberal oxygen after cardiac arrest and how sepsis is recognised early.

What to watch

The obvious next step is a larger, multi-region trial powered to detect the kind of difference the raw numbers here hint at, ideally one that also tracks comfort, workload for nurses, and longer-term outcomes rather than the 24-hour mark alone. Until then, SLOWH offers reassurance that the exact weaning sequence is unlikely to be what decides a patient's recovery.

This article describes research and is not medical advice. Decisions about oxygen therapy in critical illness belong with the treating team.