Extraction of response waveforms of heartbeat and blood pressure to swallowing. Using mixed signal processing of time domain and respiratory phase domain.
BACKGROUND
Evaluating the accurate responses of the cardiovascular system to external stimuli is important for a deeper understanding of cardiovascular homeostasis. However, the responses should be distorted by the conventional time domain analysis when a frequency of the effect of external stimuli matches that of intrinsic fluctuations.


OBJECTIVE
The purpose of this study is to propose a mixed signal processing of time domain and respiratory phase domain to extract the response waveforms of heartbeat and blood pressure (BP) to external stimuli and to clarify the physiological mechanisms of swallowing effects on the cardiovascular system.


METHODS
Measurements were conducted on 12 healthy humans in the sitting and standing positions, with each subject requested to swallow every 30 s between expiration and inspiration. Waveforms of respiratory sinus arrhythmia (RSA) and respiratory-related BP variations were extracted as functions of the respiratory phase. Then, respiratory effects were subtracted from response waveforms with reference to the respiratory phase in the time domain.


RESULTS
As a result, swallowing induced tachycardia, which peaked within 3 s and recovered within 8 s. Tachycardia was greater in the sitting position than during standing. Furthermore, systolic BP and pulse pressure immediately decreased and diastolic BP increased coincident with the occurrence of tachycardia. Subsequently, systolic BP and pulse pressure recovered faster than the R-R interval.


CONCLUSIONS
We conclude that swallowing-induced tachycardia arises largely from the decrease of vagal activity and the baroreflex would yield fast oscillatory responses in recovery.
Takashi Numata, Graduate School of Frontier Science, The University of Tokyo #303, Building 4, RCAST, 4-6-1 Komaba, Meguro, Tokyo 153-8904, Japan, E-mail: numata@neuron.t.u-tokyo.ac.jp.
T
T
Numata
Y
Y
Ogawa
K
K
Kotani
Y
Y
Jimbo
D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D003679:Deglutition / Q000502:physiology*; D045853:Exhalation / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D012016:Reference Values; D065809:Respiratory Sinus Arrhythmia / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D014630:Vagus Nerve / Q000502:physiology
Heart rate variability; Hilbert transform; blood pressure variability; respiratory phase; swallowing