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Biomedical subjects

C D Kuo

Publications and source records attributed to C D Kuo.

At least 19 recordsLinked to original sources
PubMed2001

A new 3-D display method for 12-lead ECG.

A new three-dimensional (3-D) 12-lead electrocardiogram (ECG) display method is presented which employs a 3-D rectangular coordinate system to display the 12-lead cardiac electric signals in two 3-D graphs. The 3-D graph consists of a temporal axis representing the time domain of the cardiac signals, a spatial axis representing the lead positions, and an amplitude axis representing the voltages of the cardiac signals. The six horizontal plane leads and the other six frontal plane leads were displayed in two 3-D graphs, respectively. The voltages of the cardiac signals were represented in rainbow-like colors. Cubic interpolation was employed to insert interconnecting points between neighboring leads on each plane and to smooth the surface of the 3-D ECG graphs. The 3-D ECG graphs of a normal subject, a patient with myocardial infarction, and a patient with left bundle branch block were presented in this paper. This new display method could not only be used as a complementary display method to the 12-lead ECG, but also provide physicians with an overall integral view about the spatial distribution of the cardiac signals.

Color↗
PubMed2000

Biphasic changes in autonomic nervous activity during pregnancy.

To understand the sequential response of the autonomic nervous system to pregnancy, we studied heart rate variability in 23 first trimester, 23 second trimester and 21 third trimester pregnant women. Twenty non-pregnant women were recruited as controls. Time and frequency domain measures of heart rate variability in three recumbent positions were compared. We found that normalized high-frequency power in the supine position increased significantly in the first trimester (42.2 (95% confidence interval (CI) 5.4) nu (normalized unit); P < 0.05) compared with non-pregnant controls (33.0 (6.0) nu), and then decreased progressively in the second (27.3 (6.7) nu) and third (21.8 (6.0) nu; P < 0.05) trimesters. The low-/high-frequency power ratio in the supine position decreased significantly in the first trimester (0.8 (0.3); P < 0.05) compared with that of non-pregnant controls (1.1 (0.3)) and increased progressively in the second (1.5 (0.4)) and third (2.1 (0.8); P < 0.05) trimesters. When the position was changed from the supine to the right lateral decubitus, the percentage change in normalized high-frequency power correlated significantly and negatively with normalized high-frequency power in the supine position in non-pregnant controls (r = -0.56, P = 0.01) and in pregnant women in the first (r = -0.44, P = 0.034), second (r = -0.68, P < 0.001) and third (r = -0.68, P < 0.001) trimesters. These results indicate that autonomic nervous activity shifted towards a lower sympathetic and higher vagal modulation in the first trimester, and changed towards a higher sympathetic and lower vagal modulation in the third trimester as gestational age increased. The balance between the haemodynamic changes of pregnancy and aortocaval compression caused by the enlarging gravid uterus may be responsible for the biphasic changes in autonomic nervous activity during pregnancy.

Adult↗
PubMed2000

Effect of different recumbent positions on spectral indices of autonomic modulation of the heart during the acute phase of myocardial infarction.

OBJECTIVE: To examine which recumbent position can lead to the highest vagal modulation in patients during the acute phase of myocardial infarction. DESIGN: Descriptive study. SETTING: Intensive care unit in a medical center. PATIENTS: A total of 52 patients admitted to the intensive care unit because of acute myocardial infarction (AMI), 41 patients with coronary artery disease (CAD), and 28 patients with patent coronary arteriogram. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Heart rate variability analysis was performed in patients with AMI, patients with CAD, and patent coronary controls in supine, left lateral decubitus, and right lateral decubitus positions in random order. In the right lateral decubitus position, the vagal modulation was the highest and the sympathetic modulation was the lowest among three recumbent positions in three groups of patients. When the position was changed from supine to right lateral decubitus, the increase in vagal modulation was greater in patients who had more severely depressed vagal modulation in the supine position and the rate of increase was the greatest in patients with AMI, followed by patients with CAD and patent coronary controls. Detailed analysis showed that the vagal enhancing and sympathetic suppression effect of the right lateral decubitus position applied to patients with Q wave myocardial infarctions. CONCLUSIONS: The right lateral decubitus position can lead to the highest vagal modulation and the lowest sympathetic modulation among three recumbent positions in patients with Q wave myocardial infarction. The right lateral decubitus position can be used as an effective vagal enhancer in patients with Q wave myocardial infarction but without severe bradycardia or atrioventricular block.

Aged↗
PubMed1999

Sequential changes in heart rate variability after coronary artery bypass grafting.

Heart rate variability (HRV) decreased soon after coronary artery bypass grafting and returned to the preoperative level within 2 months; however, HRV did not exceed the preoperative level, even 6 months after coronary artery bypass grafting. Although myocardial ischemia can be improved by coronary artery bypass grafting, HRV did not benefit from coronary artery bypass grafting within 6 months.

Adult↗
PubMed1999

Implementation of spectral width Doppler in pulsatile flow measurements.

In this paper, we present an automatic beam-vector (Doppler) angle and flow velocity measurement method and implement it in pulsatile flow measurements using a clinical Doppler ultrasound system. In current clinical Doppler ultrasound flow velocity measurements, the axis of the blood vessel needs to be set manually on the B-scan image to enable the estimation of the beam-vector angle and the beam-vector angle corrected flow velocity (the actual flow velocity). In this study, an annular array transducer was used to generate a conical-shaped and symmetrically focused ultrasound beam to measure the flow velocity vectors parallel and perpendicular to the ultrasound beam axis. The beam-vector angle and flow velocity is calculated from the mode frequency (f(d)) and the maximum Doppler frequency (f(max)) of the Doppler spectrum. We develop a spectrum normalization algorithm to enable the Doppler spectrum averaging using the spectra obtained within a single cardiac cycle. The Doppler spectrum averaging process reduces the noise level in the Doppler spectrum and also enables the calculation of the beam-vector angle and flow velocity for pulsatile flows to be measured. We have verified the measurement method in vivo over a wide range of angles, from 52 degrees to 80 degrees, and the standard deviations of the measured beam-vector angles and flow velocities in the carotid artery are lower than 2.2 degrees and 12 cm/s (about 13.3%), respectively.

Blood Flow Velocity↗
PubMed1999

Comparison of supine and upright positions on autonomic nervous activity in late pregnancy: the role of aortocaval compression.

In order to understand the effect of aortocaval compression on autonomic nervous activity, we compared the effects of supine and upright postures on measures of heart rate variability in late pregnancy. Thirty-two women in late pregnancy and 23 nonpregnant age-matched women were studied. Both time and frequency domain heart rate variability measures were compared between the supine and upright positions, and between pregnant women and controls. The pregnant women had smaller mean RR interval, standard deviation of RR intervals and normalised high-frequency power, and a larger low- to high-frequency power ratio than nonpregnant women in the supine position. When the position was changed from upright to supine in nonpregnant women, the percentage change in the mean RR interval and normalised high-frequency power were increased, whereas the percentage change in the coefficient of variation of RR interval and low- to high-frequency power ratio were decreased. In contrast, the percentage change in normalised high-frequency power was decreased and the percentage change in low- to high-frequency power ratio was increased in pregnant women when the position was changed from upright to supine. These results indicate that the vagal enhancing effect seen in normal subjects when changing position from upright to supine was reversed in women in late pregnancy. Aortocaval compression in the supine position in pregnant women might be responsible for this reversal in the autonomic response to lying down.

Adult↗
PubMed1999

Return of autonomic nervous activity after delivery: role of aortocaval compression.

We have compared measures of heart rate variability (HRV) in 15 women in late pregnancy before and 3 months after delivery and in 20 non-pregnant controls, to study the effect of aortocaval compression on autonomic nervous activity. Normalized high-frequency power was used as an index of vagal activity and the low-/high-frequency power ratio as index of sympathovagal balance. We found that the decrease in vagal activity and increase in sympathovagal balance before delivery returned to normal 3 months after delivery. Percentage changes in vagal activity and sympathovagal balance 3 months after delivery in the left lateral decubitus position were least among three recumbent positions. The relief of aortocaval compression as a result of delivery of the fetus may be the main cause of return of autonomic nervous activity 3 months after delivery. Postpartum hormonal changes may also contribute to return of autonomic nervous activity after delivery.

Adult↗
PubMed1998

Comparison of three recumbent positions on vagal and sympathetic modulation using spectral heart rate variability in patients with coronary artery disease.

Patients with coronary artery disease (CAD) have depressed vagal modulation. Because the mortality risk from acute myocardial infarction is lower in patients with higher vagal modulation, methods that can increase vagal modulation are desirable for patients with CAD. The right lateral decubitus position has been found, in young healthy subjects, to lead to the highest vagal modulation among 3 recumbent positions using spectral heart rate variability (HRV) analysis. This study investigated which recumbent position can give rise to the highest vagal modulation in patients with severe CAD. Twenty-seven patients scheduled for coronary artery bypass graft surgery and 17 patients with angiographically normal coronary arteries were studied. Spectral HRV analysis was performed in random order on these patients in 3 recumbent positions: namely, the supine, left lateral decubitus, and right lateral decubitus positions. Normalized high-frequency power was the highest, whereas normalized low-frequency power and low/high-frequency power ratio in the right lateral decubitus position were the lowest, among the 3 recumbent positions in both groups of patients. The lower the normalized high-frequency power in the supine or left lateral decubitus position, the higher the increase in the normalized high-frequency power when the position was changed from supine or left lateral decubitus to right lateral decubitus in patients with severe CAD. Right lateral decubitus position can lead to the highest vagal modulation and the lowest sympathetic modulation among the 3 recumbent positions in patients with severe CAD. Therefore, the right lateral decubitus position can be used as an effective physiologic vagal enhancer in patients with severe CAD.

Aged↗
PubMed1997

The effect of the lateral decubitus position on vagal tone.

The average person spends about one-third of their time in a recumbent position. However, little is known about the effect of recumbent posture on autonomic nervous activity. Manoeuvres which can increase vagal tone have been sought both in the normal subject and in patients with heart disease. We have studied the autonomic effect of various recumbent positions, namely the supine, left lateral decubitus and right lateral decubitus positions, in healthy subjects by using spectral heart rate variability analysis. Both time- and frequency-domain measures were calculated and compared between the three recumbent positions. The normalised high-frequency power was used as the index of cardiac vagal activity, the normalised low-frequency power as the index of cardiac sympathetic activity and the low-frequency power/high-frequency power ratio as the index of sympathovagal balance. The normalised high-frequency power is highest in the right lateral decubitus position, followed in decreasing order by left lateral decubitus and supine positions. The low-frequency power/high-frequency power ratio has the reversed trend as compared with that of the normalised high-frequency power. These results suggest that cardiac vagal activity is greatest when the right lateral decubitus position is adopted.

Adult↗
PubMed1997

The effect of position on autonomic nervous activity in late pregnancy.

We investigated the effect of three different recumbent positions on autonomic nervous activity in late pregnancy. Thirty pregnant and 24 nonpregnant aged-matched women were studied, and measures of heart rate variability in both time and frequency domains were compared using supine, right and left lateral decubitus positions. In the nonpregnant women, the normalised high-frequency power was greatest in the right lateral decubitus position. In the pregnant women, the normalised high-frequency power was lowest and the low/high-frequency power ratio was greatest in the supine position. Both the percentage decrease of normalised high-frequency power and the percentage increase of low/high-frequency power ratio in the supine and right lateral positions were greater than those in the left lateral position. For women in late pregnancy, the left lateral decubitus position may be beneficial because cardiac vagal activity is least suppressed and cardiac sympathetic activity is least enhanced. Aortocaval compression might be the mechanism underlying the change in cardiac autonomic nervous activity when supine and right lateral decubitus positions are assumed in late pregnancy.

Adult↗
PubMed1996

Perioperative plasma concentrations of tumor necrosis factor-alpha and interleukin-6 in infected patients.

OBJECTIVE: To characterize the sequential plasma concentrations of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) and their relationship with the clinical outcome in patients with intra-abdominal infection who underwent surgical intervention. DESIGN: A prospective, comparative study. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: Fifteen patients with surgically proved intra-abdominal infection were included as the infected group. The comparative noninfected group consisted of ten patients who underwent major abdominal surgery without infection. INTERVENTIONS: Blood samples were obtained from the indwelling arterial catheter before induction of general anesthesia, and 1, 1.5, 2, 3, 4, 6, and 24 hrs after skin incision. MEASUREMENTS AND MAIN RESULTS: Plasma cytokine concentrations were measured using radioimmunoassay. The hemodynamic and physiologic parameters were recorded for comparison with cytokine concentrations. In the noninfected group, the TNF-alpha concentration was very low throughout the observation period, and the IL-6 concentration increased 4 hrs after skin incision. The infected group had significantly higher TNF-alpha and IL-6 concentrations than the noninfected group. The TNF-alpha concentration increased from 129.2 +/- 46.4 to 1196.0 +/- 445.8 pg/mL and the IL-6 concentration increased from 54.2 +/- 24.3 to 560.3 +/- 187.5 pg/mL 2 hrs after skin incision in the infected group. The postoperative APACHE II score correlated significantly with both peak IL-6 (r2=.39) and peak TNF-alpha (r2=.32) concentrations. CONCLUSIONS: Both TNF-alpha and IL-6 concentrations increased significantly after surgical intervention in patients with intra-abdominal infection. The pulse increase in TNF-alpha concentration and the persistent increase in IL-6 concentration were related to the poor postoperative clinical condition in infected patients.

Adult↗
PubMed1993

The effects of high-fat and high-carbohydrate diet loads on gas exchange and ventilation in COPD patients and normal subjects.

Reducing the CO2 production (VCO2) is a plausible means to lower the ventilatory demand in the treatment of patients with COPD. The purpose of this study was to examine the effects of high-fat and high-carbohydrate (high-CHO) diet loads on gas exchange and ventilation in the COPD patients and normal subjects. The percentage of changes in the averaged values of VCO2, O2 consumption (VO2), respiratory quotient (RQ), minute ventilation (VE), and end-tidal CO2 (ETCO2) measured by a mass spectrometer for 5 min every 30 min after the diet were compared between diets and between study subjects. Compared with the high-fat diet, the high-CHO diet can lead to significantly higher levels of VCO2, VO2, RQ, and VE in the COPD patients 30 to 60 min after the diet, and the differences can last for about 1.5 h. The comparison between COPD patients and normal control subjects also showed that the high-CHO diet load can result in significantly higher levels of VCO2, VO2, and VE, and significantly lower level of ETCO2 in the COPD patients, whereas the high-fat diet cannot. In addition, enhanced thermic effect of food within 150 min (TEF150) occurred in the COPD patients as compared with that of normal controls, and the increase in TEF150 occurred only with the high-CHO diet. This study suggested that a high-fat diet is more beneficial to the COPD patient than a high-CHO diet, and that the gas exchange and energy utilization of the COPD patients following a high-CHO diet might be different from that of normal control subjects.

Adult↗
PubMed1993

Comparison of BiPAP nasal ventilation and ventilation via iron lung in severe stable COPD.

The effects of noninvasive ventilators on COPD remain controversial because of their obscure mechanisms. A randomized crossover study, using iron lung and positive pressure nasal ventilation (BiPAP) each for 40 min, was performed in 11 stable patients with severe COPD. Throughout the study, we monitored surface EMGdi, EMGst, ECG, SaO2, ETCO2, and the movements of RC and AB. Afterwards the data were replayed to calculate VT, RR, PR, VT/TI, iEMG, and phase angle. No statistically significant improvement was found in view of the above parameters. However, the percentage of iEMGst change after 40-min BiPAP ventilation, compared with the baseline, was much more significant in patients with FEV1 below 0.55 L than those with FEV1 above 0.55 L (n = 4:7, delta iEMGst -62.93 percent +/- 23.27 percent vs 32.45 percent +/- 42.79 percent, p = 0.0056). delta iEMGst correlated significantly with FEV1 during BiPAP ventilation (p < 0.05, r = 0.59). We conclude that the iEMGst during short-term BiPAP ventilation correlates with the severity of the disease.

Aged↗
PubMed1991

Aerosol, humidity and oxygenation.

Patients with artificial airways frequently need aerosol or humidity therapy. For this study, we used aerosols generated from a heated Puritan all-purpose nebulizer and humidity generated from a heated Bennett cascade humidifier to determine the effects of these therapies in spontaneously breathing neurosurgical patients with nasal endotracheal tubes and normal lungs. Crossover comparison of oxygenation status before and after aerosol or humidity therapy was done by analyzing P(A-a)O2 in these patients. We found that aerosols have a detrimental effect on the patient's oxygenation status, suggesting that humidity is preferable in maintaining adequate oxygenation in a patient with a normal lung plus artificial airway. The arterial pH and PaCO2 were not affected by aerosol therapy. Care should be exercised with regard to the adverse hypoxemic effect of bland aerosols when a large-reservoir jet nebulizer is used in an intubated patient who already has impaired cardiopulmonary function or borderline PaO2.

Aerosols↗
PubMed1990

Tissue oxygen extraction in patients with adult respiratory distress syndrome and multiple organ failure.

Multiple organ failure (MOF) associated with adult respiratory distress syndrome (ARDS) secondary to sepsis, trauma, etc., continues to be a syndrome with poor prognosis. It is generally accepted that tissue hypoxia is associated with the subsequent development of MOF. The purpose of this study was to find the relationship between the reduced tissue oxygen extraction and the severity of the syndrome. By correlating either the tissue oxygen extraction per unit volume of blood, CaO2-CvO2, or the oxygen extraction ratio, (CaO2-CvO2)/CaO2, with the intrapulmonary shunt, Qs/Qt, we found that there were significant inverse correlations between these two parameters of tissue oxygen extraction and the severity of the illness in patients with ARDS and MOF. The observed reduction in tissue extraction of oxygen may be related to the development of deranged metabolism in ARDS and MOF.

Adult↗
PubMed1989

Erythrocyte sedimentation realizable in terms of population dynamics.

A phenomenological theory is formulated in analogy to the theory of population dynamics to account for the observed erythrocyte sedimentation-time and velocity-time curves. The least square fitting of experimental data to the derived equations is quite satisfactory. Several parameters in the proposed equations can be used to characterize these two curves of erythrocyte sedimentation: the biotic potential or intrinsic rate of decrease of the lacuna population, r; the total distance settled by the interface between plasma and red cell column, K.delta h; the maximal settling velocity of the interface, Vmax; the time when Vmax occurs, tmv; and the final position of the interface, Hf.

Blood Sedimentation↗