Testing for heart rate variation in diabetes: single or repeated deep breaths?

Heart rate variation during three periods of single deep breaths and three periods of repeated deep breathing at 6 breaths/min was compared in 14 normal and 40 diabetic subjects. There were no differences between the two methods in either normals or diabetics, but the coefficient of variation was significantly smaller using the repeated deep breaths method. When the 6 periods of breathing were analysed separately, no 'training' effect could be detected. The first breath of the repeated deep breaths consistently produced the largest heart rate variation in 29% of the normals and 17% of the diabetics. We conclude that there is no advantage in using the single deep breath method to assess cardiac parasympathetic function in diabetics over the currently used 6 repeated deep breaths/min.