Introduction:

Yawning is often present in patients subjected to a tilt table test. Previous studies have demonstrated that yawning stimulates the sympathetic nervous system, with its subsequent haemodynamic changes, mainly heart rate and blood pressure.

Objective:

To describe the haemodynamic effects of yawning on the autonomic nervous system, as well as to establish yawning as a protective mechanism of syncope, or a predictor of a positive haemodynamic response.

Methods:

A secondary source observational study conducted using a database of patients that were subjected to the tilt table test between August 2010 and December 2015, and yawned at least once during the test. Statistical analyses and paired tests were performed to determine correlations.

Results:

A total of 156 patients were included, the majority women, and a mean age of 40 years. Syncope was presented in 43 patients. The remaining 113 (72.4%) yawned with no syncope, and of these, 50 (44.2%) had yawned and had a positive response to the tilt-table test. Although there was an increase in the majority of haemodynamic variables, a significant decrease was observed in the heart rate. Yawning was observed as a protector of syncope in 67 patients, whilst it was a predictor of a positive haemodynamic response in 61 patients.

Conclusion:

Yawning is associated with activation of the sympathetic nervous system, with haemodynamic effects and on the autonomic nervous system. It could be established as a predictive sign of a mixed type or vasodepressor positive haemodynamic response, and in other cases as a protective mechanism against the appearance of a syncope.

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