Can an Ultrasound of the Breathing Muscle Tell When a Baby Is Ready to Come Off the Breathing Machine?

What a 2026 review of seven studies by Sousa and colleagues found about scanning the diaphragm of newborn babies before their breathing tube is removed, and why it is not yet ready to guide that decision

When a baby in intensive care is ready to come off a breathing machine, doctors cannot always tell whether the baby's main breathing muscle, the diaphragm, is strong enough to manage alone. A new review that combined seven studies of 255 newborn babies found that one ultrasound measurement, how much the diaphragm thickens with each breath, was lower on average in babies who later needed their breathing tube put back. The link was consistent across the studies, but it is not yet strong or reliable enough to decide when an individual baby's tube should come out.

Why taking out a breathing tube is a big decision

Many babies born early need help from a breathing machine, called a ventilator, in their first days or weeks. The machine pushes air through a thin tube placed in the baby's windpipe. Removing that tube is called extubation, and it is a moment every family in the neonatal intensive care unit (NICU) looks forward to. Sometimes, though, a baby tires or struggles in the hours or days afterwards and the tube has to go back in. Doctors call this extubation failure. It is common, it is nobody's fault, and teams plan for it, but everyone would like to get the timing right the first time.

The researchers behind the new review point out that deciding when a newborn is ready "remains largely subjective" [1]. In other words, it relies heavily on the experience and judgment of the care team.

How doctors have made this decision until now

Doctors have long faced a balancing act. Breathing machines save lives, but staying on one can itself cause harm, especially to premature babies, so experts recommend weaning babies off the ventilator as soon as it is safe [2]. On the other hand, needing the tube back matters too. In one study of 174 babies born before 28 weeks of pregnancy, about two in three (68%) managed without the tube; those who needed it back tended to need breathing support for longer and were more likely to die before going home, and the most useful clues were simply how early the baby was born and the level of carbon dioxide in the blood before extubation [3]. Another study of 194 very small babies found that almost half (91 babies) needed a tube put back at some point in their hospital stay, and that how many days doctors keep counting after extubation changes how often "failure" is recorded [4].

So teams have relied on a checklist of signs: Is the baby breathing well on their own? Are blood tests acceptable? Is the machine already giving only gentle support? These checks help, but they cannot see inside the chest. If you would like to read more about how doctors predict extubation failure and what it means for babies afterwards, In[Neo]Sight has a related article on predicting extubation failure and its consequences.

Why doctors started looking at the diaphragm

The diaphragm is a thin, dome-shaped muscle that sits under the lungs. Each time we breathe in, it tightens and pulls downward, a bit like a piston, drawing air into the lungs. In newborns, and especially in premature babies, this muscle is smaller, flatter and tires more easily, and long periods on a ventilator, infections and low oxygen can weaken it further [5]. As long ago as 1988, doctors examining the diaphragms of babies who had been on ventilators for a long time noticed that the muscle fibres looked shrunken, and wondered whether this made weaning harder [6]. Careful ultrasound measurements in healthy premature babies later showed that the diaphragm is only between about 1 and 2 millimetres thick and grows as the baby matures [7].

Ultrasound, the same safe, painless technology used to look at babies before birth, can show the diaphragm moving in real time at the bedside. In adults in intensive care, a weak-looking diaphragm on ultrasound was linked with a longer and harder time coming off the ventilator [8], and a large review of 88 adult studies found that how much the diaphragm thickens during a breath seemed to be the most accurate muscle test for predicting a successful wean [9]. In babies, doctors first tried scanning the lungs instead, with encouraging results [10][11]. When they turned to the diaphragm, the answers were mixed. A study of 43 premature babies in Mansoura, Egypt, found that babies whose diaphragm moved more did better [12], and studies in Rome and in Madina, Saudi Arabia, found that a diaphragm that shrank during ventilation was linked with needing the tube back [13][14]. But studies in Toronto, Canada, and Rishikesh, India, found no clear difference in diaphragm movement or thickening between babies who did well and babies who did not [15][16]. Families and doctors were left with a confusing picture.

What the researchers did

A team led from the University of Manitoba in Winnipeg, Canada, carried out what is called a systematic review and meta-analysis: they searched five medical databases and a register of clinical studies for every study on this question and then combined the results mathematically, so that many small studies could be read together as one larger picture [1]. They found seven studies, from Egypt (two studies), Canada, Italy, Saudi Arabia, India and Brazil, that together included 255 newborn babies on ventilators. Most were born early, many very early. One Brazilian study also included older babies up to 2 years old, so the reviewers used only the information on its 19 newborns [17][1]. Babies with birth defects, including problems of the diaphragm itself, and babies with nerve or muscle disorders were not included.

Across all seven studies, 90 of the 255 babies, roughly one in three, needed their breathing tube put back. The researchers compared three ultrasound measurements, taken before extubation, between babies who managed without the tube and babies who did not. The first was how thick the diaphragm is when relaxed. The second was how much it thickens when the baby breathes in, called the "thickening fraction", a little like a biceps muscle bulging when you bend your arm. The third was how far it moves down with each breath, called the "excursion".

What they found

Only one of the three measurements clearly differed. On average, babies who needed the tube back had a thickening fraction about 9.5 percentage points lower than babies who stayed off the ventilator [1]. In one of the included studies, for instance, the diaphragm thickened by about 31% with each breath on average in babies who stayed off the ventilator and by about 21% in those who needed the tube back. This result was remarkably consistent across the six studies that measured it, and the researchers rated their confidence in it as moderate.

The resting thickness and the downward movement did not differ clearly between the two groups. The studies disagreed with one another on these two measurements, and the researchers rated their confidence as very low. Part of the reason is size: in newborns, the diaphragm usually moves only about 2 to 4 millimetres with each breath, roughly six times less than in adults, and its resting thickness can be under one millimetre, so tiny measuring differences matter a great deal [1].

Why this is not yet a test for an individual baby

It is natural to hope that a quick scan could now tell parents and doctors whether a baby is ready. The researchers are clear that it cannot, for several reasons [1].

First, the review found an average difference between groups, but it did not identify a cut-off number that separates babies likely to succeed from babies likely to struggle. Readings from babies who did well and babies who did not overlapped a great deal.

Second, a lower thickening fraction does not necessarily mean a weak muscle. It can also mean the baby was simply taking gentler breaths at that moment, or that the ventilator was doing more of the work during the scan. Studies in adults show the same puzzle: thickening sometimes tracks breathing effort closely and sometimes reflects muscle strength poorly [18][19].

Third, the studies were small and done in different ways, at different times before extubation and with different machine settings. Several did not account for how early the babies were born or how sick they were, which could explain part of the difference. They also defined "failure" differently, counting anywhere from 2 to 7 days after extubation. And not every failure involves the diaphragm at all: in the Brazilian study, half of the babies who needed the tube back had a problem with the upper airway, the passage above the windpipe [17].

What this means for your baby

If your baby is on a ventilator, the decision about when to remove the breathing tube will still be based on how your baby is breathing, blood test results and how little help the machine is giving. Some units may perform a diaphragm or lung ultrasound as part of their assessment or research, and it is a painless, radiation-free scan. It is reasonable to ask what the scan showed and how the team is using it. A lower reading does not mean extubation will fail, and a higher reading does not guarantee success. If your baby does need the tube back, that is a common part of many premature babies' journeys and does not mean the team made a mistake.

What researchers are working on next

The review's authors call for larger studies across many hospitals that scan babies in the same way, at the same time before extubation (ideally 30 to 60 minutes before), with the ventilator settings recorded, and that define "failure" the same way, preferably as needing the tube back within 3 days [1]. Those studies should also account for how premature and how sick each baby is, so that researchers can test whether a reliable cut-off exists. Experts also note that more NICU doctors need training in diaphragm ultrasound, and that normal values for babies still need to be established [20].

The bottom line

This review brings together the scattered early evidence on diaphragm ultrasound. It shows that babies whose diaphragm thickens less with each breath are, on average, more likely to need their breathing tube put back [1]. That is a useful clue about how newborns breathe, but it is not yet a test that can decide when an individual baby's tube should come out. For now, your baby's care team will continue to rely on careful bedside judgment, with ultrasound as a promising tool that researchers are working to make dependable.

References

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