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Volumetric imaging of upper airways

Preemies’ narrowed upper airways may explain higher OSA risk

Volumetric imaging of upper airways

The airway structures of interest to the Children’s National research team included the nasopharynx (labeled red), oropharynx (labeled purple), hypopharynx (labeled green), adenoids (labeled yellow) and tonsils (labeled blue). The team displayed the volumetric imaging in three perpendicular planes and a three-dimensional model.
Credit: A. Smitthimedhin, et al, Clinical Imaging.

Infants born preterm have significantly lower nasopharyngeal and oropharyngeal volumes, compared with newborn peers carried to full term, and those lower airway volumes are independent of the infants’ gender, ethnicity or weight, according to a study published online Dec. 16, 2017 in Clinical Imaging.

According to the Centers for Disease Control and Prevention, 1 in 10 babies born in the United States is preterm, or born prior to the 37th gestational week. Premature birth leaves these children more susceptible to disordered breathing while sleeping, including obstructive sleep apnea (OSA), an ailment characterized by increased upper-airway resistance that narrows airways.

“In addition to finding some airway volumes were smaller in preterm infants, our results indicated both sets of newborns had similar hypopharyngeal volumes. This suggests that risk factors that lead to OSA are confined to the uppermost airway and do not appear to be explained by enlarged adenoids and tonsils,” says Anilawan Smitthimedhin, a Children’s National Health System radiology research fellow at the time the study was performed and lead author of the paper.

In order to diagnose OSA, clinicians now use bronchoscopy, but the method has limitations, including the need to insert a lighted instrument into the airway, which can affect pressure and resistance within the airway.

The Children’s National research team theorized that magnetic resonance imaging (MRI) could offer a non-invasive way to evaluate the upper airway, determine its anatomy and dynamic function, while shielding infants from radiation exposure that can accompany other imaging techniques.

They enrolled 96 infants who had undergone brain MRIs as part of an unrelated study about neonatal brain development. The newborns had a range of medical conditions, including suspected hypoxic ischemic encephalopathy, cardiac disease and seizures/movement disorders.

Forty-nine of the infants were born preterm; at the time of the MRI, their corrected mean gestational age was 38.4 weeks. Forty-seven of the newborns were born full term; they received MRIs at 1.7 weeks of age. The airway structures of interest included the nasopharynx (the upper part of the pharynx), oropharynx (located at the back of the mouth behind the oral cavity), hypopharynx (the entrance into the esophagus), adenoids and tonsils. The team displayed the volumetric imaging in three perpendicular planes and a three-dimensional model.

“Nasopharyngeal volume of full-term infants was 495.6 mm, compared with 221.1 mm in preterm infants. Oropharyngeal volume of full-term infants was 313.6 mm, compared with 179.3 mm in preterm infants,” Smitthimedhin says.

Aided by volumetric 3D data that more accurately measures airway and lymphoid tissue, the team proposes to study a larger group of infants to determine whether narrowing of the uppermost airways predisposes very young children to experiencing OSA later in life.

“Ultimately, our goal is to incorporate dedicated, dynamic MR imaging of the airway while children sleep, which would provide real-time, detailed information about the changes associated with sleep. This innovation holds the promise of leading to more accurate, non-invasive diagnosis of OSA in infants,” says Dorothy Bulas, M.D., chief of Diagnostic Imaging and Radiology at Children’s National.

Children’s National study co-authors include Radiologist Matthew Whitehead, M.D.; University of Maryland student Mahya Bigdeli; Pulmonologist Gustavo Nino Barrera, M.D.; Pulmonologist Geovanny Perez, M.D,; and Hansel Otero, who was at Children’s National when the research work was performed but now works at Children’s Hospital of Philadelphia.

child sleeping

Losing sleep: Severe obstructive sleep apnea

child sleeping

Researchers at Children’s National collected information on 250 children with severe obstructive sleep apnea – defined as at least 10 pauses in breathing in an hour during sleep – who were seen at Children’s National’s Pediatric Sleep Laboratory.

Obstructive sleep apnea (OSA) often starts with a snore that sounds harmless enough. But over time, explains Sasikumar Kilaikode, M.D., a pediatric pulmonary fellow in the Division of Pulmonary Care at Children’s National Health System, this condition can lead to serious health consequences. OSA, caused when the airway becomes periodically blocked during sleep, has a bevy of associated and often serious complications that can affect children, including heart problems and neurocognitive issues, such as learning disabilities.

“Many of the consequences of obstructive sleep apnea are preventable if patients get timely diagnosis and treatment,” Dr. Kilaikode says. “But we haven’t been sure how timely these interventions happen for some of our patients.”

Researchers have reported that conditions such as asthma and probably OSA tend to disproportionally affect children from disadvantaged backgrounds and that the severity of this condition tends to be greater in minority groups. However, Dr. Kilaikode explains, there have been insufficient data about how the most severe form of this condition affects inner city residents, a population that tends to have relatively higher numbers of disadvantaged, minority children – particularly the timeliness of diagnosis and treatment for this group.

To investigate, Dr. Kilaikode, his mentor Gustavo Nino Barrera, M.D., and colleagues collected information on 250 children with severe OSA – defined as at least 10 pauses in breathing in an hour during sleep – who were seen at Children’s National’s Pediatric Sleep Laboratory. This facility performs sleep studies on children during which their oxygen levels, breathing patterns, movements and brain activity are monitored while they snooze in a hospital bed overnight.

Besides their sleep study data, the researchers also collected information about:

  • Risk factors for OSA (such as enlarged tonsils or adenoids, craniofacial abnormalities, asthma, prematurity or obesity)
  • Demographics
  • Duration of symptoms before diagnosis by the overnight sleep study

The vast majority of the 250 children enrolled in the study were African American, reflective of the demographics of the hospital’s service area. The team was surprised to learn that the time to diagnosis for African American study participants was much longer than the time to diagnosis for the non-Latino white study participants.

The team presented these results at the American Thoracic Society 2017 International Conference in Washington, D.C.

“The longer patients take to get diagnosed and treated,” Dr. Kilaikode notes, “the more likely the serious consequences of OSA become permanent.”

He adds that it’s unclear why it took so long for some patients to be diagnosed – the team’s current research efforts are focused on this question. Some of their theories are that families and schools might be unaware of this condition and its symptoms; some families might have limited access to the health care system; probable lack of screening by primary care providers; or problems with health insurance might preclude timely or adequate care.

In the future, he and other members of the Children’s pulmonary team would like to focus OSA education and outreach efforts on people that this study suggests have the greatest need: Minority and low-income families. The first step, Dr. Kilaikode says, is helping families recognize symptoms early.

Symptoms of obstructive sleep apnea include:

  • Snoring
  • Choking, gasping or prolonged pauses in breaths during sleep
  • Daytime fatigue and/or sleepiness
  • Learning problems or difficulty concentrating at school