Bedside Ultrasound Reveals Reversible Diaphragm Weakness in Ventilated Infant, Guiding Recovery

When a one-month-old infant was taken off a ventilator after a week of fighting respiratory syncytial virus bronchiolitis and pneumonia, the medical team expected the hardest part to be over. Instead, the baby kept struggling to breathe. Chest walls sank inward with every breath, the abdomen pushed outward, and muscle tone dropped. What followed, described in a case report published in BMC Pediatrics, is a striking demonstration of how a simple bedside ultrasound can peer inside the breathing machinery of a tiny patient, pinpoint a hidden weakness, and steer a treatment plan that reversed the problem within days.

The case centers on a previously healthy infant who required seven days of invasive mechanical ventilation after the viral infection progressed to pneumonia. Once the breathing tube was removed and the child was switched to high-flow nasal cannula support, clinicians expected gradual improvement. It did not come. The infant showed persistent, moderate-to-severe increased work of breathing and needed six days of noninvasive ventilation. And when the positive pressure support was finally withdrawn, a new and puzzling set of signs emerged: a progressive pectus excavatum, the sunken chest deformity, along with retractions beneath and between the ribs, a protuberant abdomen, reduced lung expansion on chest radiography, and axial hypotonia.

To understand what happened, it helps to consider how the diaphragm works. This dome-shaped muscle separates the chest from the abdomen and performs roughly the majority of the work of quiet breathing. When it contracts, it flattens and descends, drawing air into the lungs and pushing abdominal contents downward. In newborns and young infants, the rib cage is unusually compliant, meaning the mechanical load on the diaphragm is high and the muscle must work harder to move the chest wall. Infants are therefore especially vulnerable when the diaphragm weakens, and the outward signs can mimic other problems, including airway obstruction, residual lung disease, or even a structural chest deformity.

That vulnerability is compounded by modern intensive care. Invasive mechanical ventilation, while lifesaving, can itself injure the diaphragm. Prolonged inactivity of the muscle, deep sedation that reduces spontaneous breathing effort, and systemic inflammation all contribute to what researchers call ventilator-induced diaphragmatic dysfunction. In infants, whose respiratory muscles are already biomechanically immature, the effect can be pronounced. The challenge for clinicians is that the resulting weakness is invisible on standard monitoring. Oxygen levels and carbon dioxide readings reflect the outcome of breathing, not the strength of the muscle doing the work.

This is where diaphragmatic ultrasonography has changed the game. Using a standard ultrasound probe placed on the chest wall or upper abdomen, clinicians can measure the thickness of the diaphragm at end-expiration and at peak inspiration, and calculate a diaphragmatic thickening fraction, the percentage increase in thickness during contraction. In this infant, the initial ultrasound revealed a diaphragm only 1.35 millimeters thick at rest, thickening by just 17 percent during inspiration. Both figures pointed clearly to diaphragmatic weakness rather than an inspiratory overload problem, a distinction that would prove decisive for treatment.

Armed with that objective measurement, the team made a choice that could easily have gone the other way. Rather than reintroducing positive pressure support, which might have further unloaded and weakened the muscle, they kept the infant on high-flow nasal cannula and launched an individualized physiotherapy program. The plan included sensorimotor stimulation to reactivate breathing patterns, abdominal muscle strengthening exercises, and an abdominal support band to stabilize the trunk and improve the mechanical efficiency of the diaphragm. The approach treated the diaphragm like any other deconditioned muscle: it needed graded, targeted exercise, not rest.

Seventy-two hours later, repeat ultrasound told a different story. The diaphragmatic thickening fraction had nearly doubled to 33 percent, and inspiratory thickness had risen to 1.60 millimeters. Alongside those numbers came visible clinical change: better coordination between chest and abdominal movement during breathing, regression of the sunken chest deformity, and improved lung aeration. The high-flow support was subsequently discontinued, and the infant was discharged with clinical improvement. The transient pectus excavatum, which had appeared as the diaphragm failed to generate the pressures needed to stabilize the compliant infant rib cage, resolved as the muscle recovered.

The authors of the report, a multidisciplinary team from Rios D’or Hospital and the Fernandes Figueira National Institute of Women’s, Children’s and Adolescents’ Health at Fiocruz in Rio de Janeiro, argue that the case illustrates three distinct contributions of bedside ultrasound in pediatric critical care. First, it enabled early identification of diaphragmatic dysfunction before the infant deteriorated further. Second, it allowed the team to differentiate weakness from inspiratory overload, two conditions that can look identical at the bedside but demand opposite treatments. Third, serial measurements helped avoid the unnecessary reintroduction of positive pressure support, which could have prolonged the very problem it appeared to solve.

The implications extend beyond a single patient. Diaphragmatic ultrasound is noninvasive, radiation-free, repeatable at the bedside, and increasingly validated in adult critical care, where thickening fraction thresholds are used to predict weaning outcomes. Its adoption in pediatrics has been slower, partly because normal values in infants are less established and because the technique requires training. But cases like this one suggest a practical pathway: instead of guessing whether a struggling infant after extubation has residual lung disease, airway issues, or muscle weakness, clinicians can measure the muscle directly and tailor rehabilitation accordingly. Serial assessments could also serve as an objective endpoint for physiotherapy programs, replacing subjective impressions with numbers that track recovery.

For now, the case stands as a vivid example of precision in pediatric intensive care, where a handheld probe and a few millimeters of muscle thickness changed the course of treatment. The infant’s diaphragm, weakened by a week of mechanical ventilation and immaturity of the respiratory system, rebounded within days once it was given the right support and the right exercises. The chest deformity vanished, the breathing pattern normalized, and the child went home. As more intensive care units adopt diaphragmatic ultrasonography as a routine monitoring tool, stories like this may shift from remarkable exceptions to expected standards of care, offering a way to see the invisible work of the body’s most important breathing muscle and to help it recover before small problems become large ones.

Subject of Research: Ultrasound-guided diagnosis and rehabilitation of ventilator-induced diaphragmatic dysfunction in an infant

Article Title: Ultrasound-guided management of reversible diaphragmatic dysfunction after extubation in an infant with transient pectus excavatum: a case report

Article References: da Silva, C. D. A., Valentim, M., Terra, M. A., da Fonseca Borges, A., de Pinho Silveira, D. A., Fernandes, P. V., Moore, D. C. B. C., & dos Santos Gomes Junior, S. C. (2026). Ultrasound-guided management of reversible diaphragmatic dysfunction after extubation in an infant with transient pectus excavatum: a case report. BMC Pediatrics. https://doi.org/10.1186/s12887-026-07610-y

Image Credits: AI Generated

DOI: 10.1186/s12887-026-07610-y

Keywords: diaphragmatic dysfunction, ultrasonography, mechanical ventilation, infants, pectus excavatum, respiratory muscles, physiotherapy, pediatric intensive care, ventilator weaning, RSV bronchiolitis, Ultrasound-guided, management