Obese, snoring mini pigs show how air flows through the throat during sleep apnea

January 19, 2021

With a small snout, a short and curled tail, and a big, round stomach, mini pigs are the epitome of cute--and sometimes, they snore. Now, researchers think these snoring pigs can be used to study obstructive sleep apnea. A study appearing January 19 in the journal Heliyon found that obese Yucatan mini pigs do have naturally occurring sleep apnea and that MRI scans taken while they're in sedated sleep can be used to gain new insights into what happens in the airways during sleep apnea episodes via computational flow dynamic (CFD) analysis.

"These are very fat pigs," says first author Zi-Jun Liu, a research professor and principal investigator in the Department of Orthodontics at the University of Washington.

Because sleep apnea--a common obstruction of the airway that in humans causes someone to repeatedly wake up--currently has only a few cumbersome or invasive treatments, Liu and colleagues sought to better understand the mechanism behind the disease.

They looked at Yucatan mini pigs, two obese and three of normal weight, in part because they're comparable in both airway structure and size to humans. These pigs might be "mini," but they're still 100 pounds at normal weight. The obese pigs are even heavier. "To give some context, normal human body mass index (BMI) range around 25-28, with obesity reached at over 30-35. In pigs, normal BMIs range from 30 to 35, with obesity reached over 50," says Liu.

But even more importantly, obesity in mini pigs can actually cause them to get sleep apnea. In other animal models, like rats and rabbits, the researchers either have to make the animal gain weight to have sleep issues, which still wouldn't confirm sleep apnea in the animal, or they block the airway to make unnaturally occurring sleep apnea. "That's the most important finding," says Liu. "This naturally occurring sleep apnea in these Yucatan mini pigs was validated."

After sedating the subjects, Liu and colleagues observed multiple episodes of sleep apnea per hour in both obese pigs, while only one of the normal weight pigs displayed episodes. In natural sleep, only the obese mini pigs had sleep apnea episodes--and had as many as 35 per hour. While the researchers did not witness any episodes of snoring in the normal weight mini pigs, the obese pigs emitted a low, dinosaur-like snoring in both sedated and natural sleep.

Liu and colleagues also studied all five mini pigs in an MRI machine while they were in sedated sleep. Sleep apnea is known to be caused by anatomical restrictions of the nose and throat that cause stoppages of airflow, but the dynamics of how air flows through these passages and the mechanisms that cause the airflow to stop are not well understood. The researchers used the MRI scans they took to construct a 3D replica of the pigs' airways, finding that the obese pigs had significantly more narrowing in the throat and that there was a 25% increase in airflow velocity through these narrowest regions.

One of the researchers' hypotheses was that the sleep apnea was caused by what's known as "turbulence" in the airway. "You might be familiar with the term turbulence from when you ride an airplane. It's air that's circulated in just the local area, which of course on an airplane causes it to jump up and down," says Liu. In the airways of the pigs, turbulence formation could be caused by a combination of an abrupt change in the shape of the airflow pathway and high airflow velocity--and the researchers hypothesized that it might be the reason that air stops flowing in sleep apnea. The findings from the pigs, however, showed that was not the case: despite the narrowing of the pharynx and the increase in airflow velocity, the researchers didn't find any turbulence in the pigs' airways.

Liu says that conducting this research came with numerous challenges. It required monitoring 150-200 pound obese mini pigs, with all the bells and whistles of human sleep monitoring: devices to monitor the air flow dynamics, the chest and abdomen movements, the brain and muscle activity, oxygen saturation, and more needed to be hooked up to the pigs at all times to get proper data.

The researchers add that, while this research showed that mini pigs can provide a naturally occurring animal model to examine sleep apnea and gave a greater understanding to how sleep apnea affects the body, more must be done to find a long-term solution for and mechanisms behind this disease. "Despite our findings, the sleep apnea mechanism is still not quite understood," says Liu. "There are of course anatomic reasons, but the functional reasons behind it are still up for debate."
This work was supported by a grant from National Institute of Dental and Craniofacial Research (NIDCR) and the Morell Research Fund for the Summer Research Fellowship (SURF) from University of Washington School of Dentistry.

Heliyon, Liu et al.: "Airflow Dynamics in Obese Minipigs with Obstructive Sleep Apnea" https://www.cell.com/heliyon/fulltext/S2405-8440(20)32543-3

Heliyon (@HeliyonJournal), part of the Cell Press family, is an open access journal publishing scientifically accurate and valuable research across life, physical, social, and medical sciences journal. Visit https://www.cell.com/heliyon. To receive Cell Press media alerts, contact press@cell.com.

Cell Press

Related Science Articles from Brightsurf:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.

Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.

Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.

Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.

World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.

PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.

Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.

Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.

Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.

Read More: Science News and Science Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.