Indirect evidence for respiratory influences capable of changing RR interval independently of baroreflex

Positive phase values between cardiac cycle durafion and systolic arterial pressure at respiralory rate are usually found in human subjects in supine position. Under the assumption that heart period lags behind systolic arterial pressure at negative phase values, positive phase values are traditionally interpreted as un indirect evidence of the presence of the feed-fomard arm from cardiac cycle duration io systolic arterial pressure). We propose to interpret the positive phase values between cardiac cycle length and vstoiic arterial pressure at respiratory frequency as an indirect evidence of influences capable of changing cardiac cycle duration independently of barareflex. This interpretation does not exclude the troditianal one but it stresses thut positive phase values can be observed even in presence of a negligible contribution of the feed-forward path.