Expiration-Inspiration Ratio
     

Overview :

The expiration-inspiration (E-I) ratio is used to assess the reflex increase in the heart rate that occurs at the end of inspiration and the reflex decrease in heart rate that follows at the end of expiration.

expiration-inspiration ratio =

= (sum of six longest R-R intervals occurring during 6 expirations) / (sum of the shortest R-R intervals occurring during 6 inspirations)

  References:

Stein JH, et al. Internal Medicine, 3rd edition. Little, Brown and Company. 1990. pages 1901-1902.