Rhythmic breathing adapts to external beat through 'brain...( CAMBRIDGE Mass Sept. 12 2007 The sa...)

CAMBRIDGE, Mass, Sept. 12, 2007 The same kind of learning that allows humans to get used to a subtle touch or persistent odor may also help human vital signs adapt to medical interventions such as mechanical ventilation.

The team, led by Chi-Sang Poon, a research scientist at the Harvard-MIT Division of Health Sciences and Technology (HST), suggests that this innate ability to adapt, called nonassociative learning, could be leveraged to design more effective and less costly artificial respirators.

In a study published on September 12 in the online, open-access journal PLoS ONE, Poon examined rats under mechanical ventilation to see how they applied different forms of nonassociative learning to adapt to the rhythm imposed by the respirator.

Existing designs of respirators do not consider the adaptive nature of breathing in their design. Some respirators ignore the patients natural rhythm and pump air in and out of the lungs on set intervals. Doctors often must sedate or paralyze patients to prevent them from fighting this unfamiliar rhythm. Other designs rely entirely on the patient to trigger the airflow. These systems, however, are costly and tend to be unreliable for weak patients such as newborns or those in critical care.

Poons experiment suggests, however, that if a doctor takes the patients natural breathing rhythm into account and sets the ventilators rhythm in that same range, the patient will adapt and synchronize with the ventilator. This new approach could minimize the need for induced sedation or paralysis.

We have intrinsic nonassociative learning capabilities, called habituation and desensitization, that make up for changes in the spontaneous rhythm due to artificial lung inflation, says Poon.

Nonassociative learning is a basic and familiar animal behavior. For instance, roses smell heady and intense at first, but minutes later they lose their affect due to habituation. The body learns to
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