Better understanding of how the brain controls breathing and swallowing

Research published in the Journal of Physiology sheds new light on sudden infant death syndrome – a poorly understood condition also known as 'cot death'.

The research investigates the mechanisms that control the larynx during breathing. Abnormalities of these systems are implicated in SIDS.

The research team from Macquarie University identified two areas of the brain that work together to control breathing and swallowing to enable breathing without choking. They hope that by understanding how these two areas should work, they can identify what may be going wrong in SIDS babies.

"If irritants such as food or water 'go down the wrong way' and enter the airway, a powerful protective response is initiated in the brain to stop breathing and prevent foreign matter entering the lungs. Abnormalities in this reflex may underlie a number of threatening conditions, including SIDS," said Professor Paul Pilowski, lead author of the paper.

"The closing of the airway in adults is only a small compromise as breathing is only stopped temporarily. But for babies, the response has more radical implications, particularly if the arrest in breathing is long, as they can't take oxygen in or get rid of carbon dioxide," he said.

Pilowski notes that the time of breathing and swallowing is exquisitely coordinated. He says they suspect that coordination of the two may be what goes awry in SIDS. But, in order to be sure, they need to understand exactly how the brain organises its response in the first place.

"The protective reflex brings the vocal cords together and initiates coughing and swallowing. It is vital to everyone, but babies in particular have a tendency to regurgitate liquids after feeding, and saliva tends to pool in their throats. But it is also risky. Without breathing, oxygen levels can drop to dangerously low levels, heart rate slows and blood is re-routed to the brain, depriving and potentially damaging organs," he said.

To understand how the central nervous system controls breathing and swallowing, the team recreated the brain and body's response to a throat irritant using electrical stimulation of the nerve that normally carries the information from the larynx to the brain. Normal activation of these nerves tells the brain to initiate the reflex response.

"Until now, the centres in the brain that coordinate breathing and swallowing were poorly understood," Pilowsky said.

"But our research has finally teased apart the two mechanisms in the brain, demonstrating how they work together in the presence of an irritant."

By artificially generating a response and measuring the neurotransmitters that indicate how the different regions of the brain are talking to one another, the team hopes to have a better understanding of what is going on in the brain to disrupt the reflex and cause breathing to stop for long periods.

"The next step is to work out why these regions 'decide' whether breathing should be stopped. The eventual hope is to have the ability to manipulate these two systems separately to prevent the excessively long breathing arrest that may cause SIDS," concluded Professor Pilowsky.

(Source: Macquarie University: Journal of Physiology)