ARDS is a life-threatening form of acute lung injury in which the air sacs of the lungs become inflamed and filled with fluid, dramatically reducing the tissue available for gas exchange. The stiffness of the respiratory system, measured as elastance, reflects how much pressure is required to deliver a given volume of air. Crucially, this total elastance is the sum of two distinct components: the lung itself and the chest wall, which includes the rib cage, the diaphragm and the abdomen. Standard ventilator management in ARDS has historically treated the respiratory system as a single unit, adjusting tidal volumes and pressures according to predicted body weight and plateau pressure thresholds. This approach implicitly assumes that the contribution of the chest wall remains relatively uniform across patients, an assumption that severe obesity decisively violates.

In patients with severe obesity, the massive accumulation of adipose tissue around the thorax and abdomen, together with the upward displacement of the diaphragm by intra-abdominal fat, substantially increases chest wall elastance. The chest wall becomes stiffer and resists expansion more strongly, which means that a larger fraction of the pressure generated by the ventilator is consumed in deforming the chest wall rather than in aerating the lung. As a consequence, clinically measured pressures at the airway opening can appear alarmingly high even when the lung itself is only mildly injured, or conversely, the true stress borne by the lung parenchyma may be underestimated if the clinician assumes that all measured pressure reflects lung injury. This partitioning problem lies at the heart of the argument advanced by the Marseille team.

The physiological consequences of elevated chest wall elastance in obese patients with ARDS are far-reaching. Transpulmonary pressure, the pressure difference across the lung that actually determines lung stress and strain, cannot be directly measured at the airway. It must be inferred by subtracting an estimate of pleural pressure, typically obtained with an esophageal balloon catheter, from the airway pressure. When chest wall elastance is high, pleural pressure rises, and the airway pressure needed to achieve adequate oxygenation and alveolar recruitment increases accordingly. A ventilator strategy calibrated to airway pressures alone may therefore deliver insufficient tidal volumes and inadequate positive end-expiratory pressure to an obese patient whose lungs are, in fact, recruitable, leading to derecruitment, atelectasis and worsening hypoxemia.

The Marseille authors situate their commentary within an ongoing discussion prompted by a recent debate in the same journal on whether the esophageal balloon catheter should be deployed to personalize ventilation of ARDS. Esophageal manometry is not a new technique; it has been used in respiratory physiology for decades. Yet its adoption in routine intensive care remains limited, partly because of concerns about technical complexity, the expertise required for correct placement and interpretation, and the absence until recently of large randomized trials demonstrating outcome benefits. The correspondence by Barrau and colleagues underscores that in specific patient populations, severe obesity chief among them, the assumptions underlying conventional ventilator titration break down in ways that esophageal measurements can reveal.

Supporting evidence for the physiological argument comes from earlier work cited by the authors. A study by Behazin and colleagues published in the Journal of Applied Physiology demonstrated that morbid obesity is associated with respiratory restriction and elevated pleural and esophageal pressures, providing direct experimental confirmation that the chest wall, rather than the lung, accounts for much of the measured stiffness in this population. In parallel, a multicenter study by Coudroy and colleagues published in Anesthesiology investigated the prevalence of complete airway closure according to body mass index in patients with ARDS, documenting that higher body mass index is associated with a greater frequency of complete airway closure, a phenomenon that further complicates pressure interpretation and ventilator management at the bedside.

Complete airway closure deserves particular attention because it illustrates how obesity transforms the mechanical behavior of the respiratory system in ARDS. When the airways close completely at a certain lung volume, the pressure measured at the airway no longer communicates with the alveoli until the closing pressure is exceeded. In obese patients, the elevated pleural pressures generated by the heavy chest wall and abdomen can promote such closure, meaning that a substantial portion of each delivered breath may initially serve simply to reopen collapsed airway segments. Clinicians unaware of this mechanism may misinterpret high measured pressures as evidence of overdistension or severe lung injury and may inappropriately reduce ventilatory support, when in fact the underlying problem is the mechanical load imposed by the chest wall.

The clinical stakes of these considerations are considerable. Obesity is a rapidly growing condition worldwide, and patients with severe obesity constitute an increasing share of intensive care admissions, including admissions for ARDS triggered by pneumonia, sepsis and other causes. If ventilator protocols designed around average chest wall mechanics systematically misjudge the lung stress experienced by obese patients, then a large and expanding group of critically ill individuals may receive suboptimal care. Personalized ventilation guided by esophageal manometry offers a way to partition respiratory system elastance into its lung and chest wall components, allowing clinicians to titrate positive end-expiratory pressure and tidal volume according to transpulmonary pressures that reflect what the lung tissue itself is actually experiencing.

The correspondence does not claim that esophageal manometry is a panacea. Interpreting esophageal pressure requires attention to the position of the catheter, the effects of patient positioning and the influence of abdominal pressure, and measurements obtained in the supine, sedated and paralyzed patient differ from those in upright spontaneous breathing. Nevertheless, the authors’ central message is that ignoring chest wall elastance in severe obesity risks systematic error, whereas measuring it offers the possibility of tailoring ventilator settings to the individual patient’s physiology. In their view, the question is no longer whether chest wall mechanics matter in obese patients with ARDS, but whether the tools to measure them should be deployed more widely to translate that understanding into practice.

As the debate over personalized ventilation continues, the contribution from the Marseille intensive care team adds a clear physiological anchor. Severe obesity elevates chest wall elastance, redistributes the pressure generated by the ventilator away from the lung and toward the chest wall, and thereby distorts the conventional interpretation of airway pressures in ARDS. Whether esophageal balloon catheters become a routine part of ARDS management will depend on ongoing research, training and the accumulation of clinical evidence, but for patients with severe obesity the case for looking beyond the airway pressure gauge has rarely been more compelling.

Subject of Research: The effect of severe obesity on chest wall elastance and personalized mechanical ventilation in ARDS

Article Title: Severe obesity and chest wall elastance in ARDS

Article References: Barrau, D., Hraiech, S., & Guervilly, C. (2026). Severe obesity and chest wall elastance in ARDS. Intensive Care Medicine. https://doi.org/10.1007/s00134-026-08624-x

Image Credits: AI Generated

DOI: 10.1007/s00134-026-08624-x

Keywords: ARDS, severe obesity, chest wall elastance, mechanical ventilation, esophageal manometry, transpulmonary pressure, pleural pressure, airway closure, critical care, respiratory mechanics, positive end-expiratory pressure, intensive care medicine

Craniosynostosis, the premature fusion of one or more fibrous joints between the bones of the skull, affects roughly one in every 2,000 to 2,500 births in its typical forms. Because the skull must expand rapidly to accommodate a growing brain, early suture fusion forces the cranium to grow in compensatory directions, producing characteristic head shapes and, in some cases, raised intracranial pressure. Most cases are classified as primary, arising from genetic or developmental factors intrinsic to the suture itself. Secondary craniosynostosis, by contrast, is triggered by external or systemic influences, including metabolic bone disease, hyperthyroidism, or conditions that alter the biomechanical environment of the growing skull. The pattern reported in the new study appears to belong to this second category, but with features the authors say have not been documented together before.

The study population was narrowly and deliberately defined. The researchers reviewed charts of infants born at their institution between January 2020 and May 2025, including only those delivered at 22 to 28 weeks of gestation who went on to develop severe BPD and ultimately required a tracheostomy. Severe BPD is the most disabling form of chronic lung disease of prematurity, generally defined by a profound ongoing need for respiratory support well beyond the neonatal period. These infants spend months on mechanical ventilation, often at pressures far exceeding those used for typical neonatal care. Ten patients met all inclusion criteria, a small number that reflects both the rarity of this degree of respiratory morbidity and the single-center design of the review.

The most eye-catching quantitative result concerned head growth. Using standardized preterm growth charts and electronic growth chart calculators, the team tracked each infant’s head circumference percentile over time and found that the greatest four-week rise averaged 43 plus or minus 14 percentile points. That surge in head growth significantly outpaced concurrent changes in weight and length percentiles, a dissociation the authors report with a P value of 0.0023. In practical terms, these infants’ heads were growing dramatically faster than the rest of their bodies, the reverse of the growth faltering more commonly seen in chronic lung disease. The researchers also calculated a weighted mean sustained positive end-expiratory pressure of 10.6 centimeters of water across the cohort, a figure that quantifies the substantial ventilatory forces these infants’ chests and, potentially, their cranial circulation were exposed to for months.

Imaging told the rest of the story. Three-dimensional reconstructions of computed tomography scans of the head and maxillofacial region, presented in the published figures, revealed suture closure patterns described as atypical, alongside visible thickening of the calvarial bone, the dome of the skull. Calvarial thickening is not a feature of ordinary primary craniosynostosis and suggests an active bone-forming response rather than a simple failure of suture patency. The combination of rapid head circumference acceleration, abnormal suture fusion, and thickened skull bone led the authors to propose a novel phenotype of secondary craniosynostosis specific to this population of ventilator-dependent, tracheostomized infants with severe BPD.

The study was not the first to hint at this connection. The authors build on a 2023 report in the Journal of Craniofacial Surgery that described a similar phenotype of calvarial thickening and increased rates of premature calvarial suture closure in children with chronic lung disease. An earlier 2009 study had also associated rapid head growth in children following tracheostomy tube placement, suggesting that the airway intervention itself, or the underlying respiratory failure that necessitates it, may be linked to altered cranial growth dynamics. The new work sharpens the picture by focusing on a homogeneous group of extremely premature infants and by quantifying both the growth acceleration and the ventilatory pressures involved.

Why might prolonged high-pressure ventilation reshape a growing skull? The authors point to several plausible mechanisms that remain to be tested. Positive end-expiratory pressure, the pressure maintained in the airways at the end of each breath to keep the lungs open, is known from decades of neonatal physiology research to influence cerebral hemodynamics. Studies dating back to the late 1980s documented changes in cerebral blood flow velocity when positive end-expiratory pressure was adjusted in preterm infants, and more recent work has shown that ventilation mode changes can affect cerebral oxygen saturation. Sustained elevations in intracranial venous pressure or altered pulsatile forces transmitted through the dura could, in theory, alter the mechanical signaling environment of cranial sutures, which are exquisitely sensitive to tension and compression during development. Chronic hypoxia and the inflammatory milieu of severe BPD may add further systemic influences on osteoblast activity in the skull vault.

The clinical implications are potentially significant for both monitoring and intervention. Head circumference is routinely measured in neonatal follow-up care, but an accelerating head growth curve in a ventilator-dependent infant might currently be attributed to catch-up growth or, in some cases, mistaken for hydrocephalus. The new findings suggest that clinicians caring for infants with severe BPD on prolonged high-pressure support should consider cranial imaging when head growth accelerates disproportionately, since early identification of suture fusion can inform decisions about surgical release. Traditional management of single-suture craniosynostosis, as reviewed in the neurosurgical literature, ranges from observation to endoscopic strip craniectomy or open cranial vault remodeling, and the optimal approach for these medically fragile infants with thickened, abnormally remodeling skulls is entirely uncharted territory.

The authors are careful about the limits of their evidence. Ten patients from a single center, identified retrospectively, cannot establish causation, and the study lacked a comparison group of ventilated infants without severe BPD or of preterm infants managed with lower ventilatory pressures. The researchers explicitly call for prospective studies to define ventilatory exposure thresholds, clarify the underlying mechanisms, and determine the neurologic and surgical implications of this phenotype. Data availability is constrained by privacy protections inherent to such a small, reidentifiable cohort, though deidentified data may be shared upon reasonable request with institutional review board approval. The study protocol was approved by the Orlando Health Institutional Review Board, and the authors declare no competing interests.

Even with those caveats, the report opens an unexpected window onto how the environment of intensive care may leave structural marks on the developing body. The skull of an extremely premature infant is a dynamic, pliable structure whose sutures normally remain open for years to allow brain growth; the idea that months of positive-pressure breathing could accelerate bone deposition and suture fusion adds intensive care itself to the list of forces that sculpt cranial development. For the growing population of technology-dependent children who survive extreme prematurity, the findings underscore the need for long-term craniofacial surveillance and for research that treats the ventilator not merely as a life-sustaining tool but as a physiological exposure with consequences that may extend to the skeleton. As the authors conclude, only carefully designed prospective studies can determine whether this novel phenotype represents a true complication of modern neonatal intensive care and what it will mean for the neurodevelopmental and surgical futures of the children it affects.

Subject of Research: Atypical secondary craniosynostosis in ventilator-dependent premature infants with severe bronchopulmonary dysplasia

Article Title: Are premature infants with severe bronchopulmonary dysplasia at increased risk for atypical craniosynostosis?

Article References: Martin, S. G., Matrone, C., Stephens, M., Queliz Pena, T., Schreck, M., Guerrero, R. A., Zimmerman, A., Elbabaa, S. K., Jafrani, R., & Golden, B. (2026). Are premature infants with severe bronchopulmonary dysplasia at increased risk for atypical craniosynostosis?. Journal of Perinatology. https://doi.org/10.1038/s41372-026-02907-3

Image Credits: AI Generated

DOI: 10.1038/s41372-026-02907-3

Keywords: craniosynostosis, bronchopulmonary dysplasia, premature infants, mechanical ventilation, positive end-expiratory pressure, tracheostomy, head circumference, calvarial thickening, neonatology, craniofacial surgery, Journal of Perinatology, retrospective study