Response of heart rate variability and cardiorespiratory phase synchronization to routine bronchodilator test in patients with asthma.

Heart rate variability (HRV) and cardiorespiratory phase synchronization (CRPS) were employed to study the cardio- and respiratory interactions in patients with asthma receiving inhalation of beta2-agonist (Berotec 200 mcg) for routine bronchodilator test. Both time- and frequency-domain parameters were used to analyze the HRV. A weighted G-index was introduced to study the quality of the CRPS. The HRV parameters, in both the time and frequency domains, exhibited significant changes pointing to a sympathetic activation of the autonomic balance immediately after the inhalation. On the other hand, the CRPS index barely changed throughout the entire process. This indicates that inhalation of beta2-agonist does not alter the CRPS appreciably, and that the CRPS, in contrast to HRV, is relatively stable in response to the inhalation of beta2-agonist in patients with asthma.

"Altered Short-Term Dynamics of Cardio-Respiratory Interaction during Propofol-Induced Yawning".

"Cardiac and respiratory oscillations have been shown to interact with each other. This interaction could reflect autonomic nervous system functionality. Propofol-induced yawning during anesthesia induction seems to be associated with sympathetic activation. Presumptively, there is high linearity among interaction of different physiologic system behaviors. Recently, investigators used coherence analysis to quantify the existence and strength of linearity between system signals for study of cardio-respiratory interaction under different physiological conditions. In this investigation, we used a method of time-frequency coherence function to analyze ECG and respiration signals to investigate the linearity of cardio-respiratory dynamics in patients undergoing routine propofol induction procedures for elective surgery. In this prospective, observational clinical study, a total of 84 eligible patients were enrolled. The patients were categorized into yawning and no-yawning groups during propofol induction. During induction, both groups demonstrated significant reduction in high frequency coherence (coh-HF) with simultaneously significant increase in very low frequency coherence (coh-VLF) compared to the pre-induction period. As yawning occurred, the yawning group had more significant changes of cardio-respiratory coherences than the no-yawning group at coh-LF and coh-VLF bands. The yawning group also showed loss of linearity at high frequency band (coh-HF > 0.5) as compared with the pre-induction period, and also showed increases in linearity at low (coh-LF > 0.5) and very low (coh-VLF > 0.5) frequency bands compared with the no-yawning group. Propofol-induced yawning alters cardio-respiratory dynamics with changes of linearity between cardio-vascular and respiratory system behaviors."

Clinical assessment of propofol-induced yawning with heart rate variability: a pilot study.

STUDY OBJECTIVES: To investigate the proportion of propofol-induced yawning and sympathovagal balance during propofol-induced yawning. DESIGN: Prospective, observational, clinical study. SETTING: University hospital and 2400-bed tertiary medical center. PATIENTS: 546 ASA physical status I and II patients undergoing elective surgery with general anesthesia. INTERVENTIONS: Standard induction of anesthesia was performed with intravenous (IV) propofol two to four mg/kg (group P), or pretreatment with atropine 0.1 mg/kg (group AP) or with fentanyl 1 to 3 microg/kg (group FP) before propofol. Continuous standard electrocardiogram for heart rate variability (HRV) was performed in another 20 patients to investigate sympathovagal balance during propofol-induced yawning. MEASUREMENTS AND MAIN RESULTS: The proportions of yawning were 53.5% (207/386), 61.1% (55/90), and 0% (0/50) in the P, AP, and FP groups, respectively. Propofol-induced yawning could be dramatically decreased by pretreatment with IV fentanyl (P < 0.001, chi2 test). Significant increased ratio of low-frequency/high-frequency power was detected during HRV monitoring in 9 patients with yawning in comparison with 11 patients without yawning (P < 0.05, Wilcoxon signed-rank test). CONCLUSIONS: Pretreatment with fentanyl may inhibit propofol-induced yawning. Fluctuations in autonomic function have been noted during propofol-induced yawning.

Fentanyl-induced coughing and airway hyperresponsiveness.

BACKGROUND: The tussive effect of fentanyl, in sharp contrast to the antitussive effect that common opioids have, is not rarely seen in clinical anesthesia. Pretreatment with beta 2 agonist inhalation could dramatically suppress fentanyl-induced coughing. We hypothesized that airway hyperresponsiveness might exist in large proportion of the subjects who had experienced fentanyl-induced coughing during previous anesthesia. METHODS: We designed a case-controlled matching study to investigate the correlation between fentanyl-induced coughing and airway hyperresponsiveness. Twenty-six consecutive subjects (ASA I-III), who experienced fentanyl-induced coughing during anesthesia in our hospital from 1999 to 2000, were enrolled in this study as the fentanyl-cough group. In all the subjects baseline spirometry was first obtained. Airway responsiveness was evaluated with either PC20 of methacholine challenge test or bronchodilator test. After matching age and sex, another 26 subjects without history of fentanyl-induced coughing during previous anesthesia were also enrolled in the study as the control group. RESULTS: The proportion of airway hyperresponsiveness in fentanyl-cough group and control group was 30.77% and 19.23% respectively. After pairing of these two groups, McNemar test revealed no significant difference in the proportion of airway hyperresponsiveness between these two groups (P = 0.257). CONCLUSIONS: From the analysis of the present study, we cannot prove that there is a direct correlation between fentanyl-induced coughing and airway hyperresponsiveness.