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Biomedical subjects

B J Rubal

Publications and source records attributed to B J Rubal.

At least 37 records · Page 2Linked to original sources
PubMed1994

A comparison of noninvasive body temperature monitoring devices in the PACU.

Critical measurement of patient body temperature in the PACU is an important parameter in patient management. Failure to achieve minimal acceptable body temperature standards has been associated with physiological derangement, the application of additional therapy, and prolonged PACU stays. Newer methods to monitor temperature have been introduced into the PACU that have been touted to be adequate for detecting clinically significant changes in temperature. This study compares skin core temperature-corrected liquid crystal thermography, axillary electronic, and oral electronic thermistor readings with temperatures obtained by infrared tympanic membrane thermometry in 215 PACU patients. Regression analysis suggests that when compared with tympanic temperature, the oral method is more accurate and has greater precision than either the liquid crystal or axillary methods. That the incidence of hypothermia depends on the method chosen to assess body temperature is a significant nursing implication.

Adult↗
PubMed1994

Management of orthotopic heart transplant recipients at Brooke Army Medical Center.

Advances in heart transplantation and post-operative rejection therapy have given new hope to patients with end-stage congestive heart failure and cardiomyopathies. The growing numbers of pre- and post-transplant patients and the complexity of their care underscore the need for a multispecialty approach to patient management. This study examines the success of a multi-service program at Brooke Army Medical Center which offers pre- and post-transplant care to active duty, dependent, and retired military personnel.

Adult↗
PubMed1993

Tetralogy of Fallot in a 71-year-old patient with new onset hypoxemia.

This study reports the evaluation and successful surgical management of a 71 year-old female with known Tetralogy of Fallot and symptomatic hypoxemia. A hybrid (fluid-micromanometer) catheter system was employed to examine right heart pressure gradients. This case presents unique hemodynamics along with angiography and palliative surgical management.

Aged↗
PubMed1993

Subtle features of the hemodynamic response to amyl nitrite inhalation: new aspects of an old tool.

Although amyl nitrite inhalation (ANI) antedates all current short acting vasodilators as a clinically useful pharmacologic stressor, few clinicians are aware of the subtle hemodynamic actions of this agent. This study examined transients in left and right heart hemodynamics after ANI in seven men (ages 44 +/- 7 years) undergoing elective cardiac catheterization. High-fidelity central aortic (AoP), left ventricular (LVP), pulmonary artery (PAP), right ventricular (RVP), and right atrial (RAP) pressures were simultaneously recorded from left and right heart multisensor catheters. As expected, ANI caused an acute fall in Ao pressure (27%; p < 0.01) and reflex tachycardia (p < 0.001). Little change was noted in PAP, RVP, RAP, or LV end-diastolic pressures or the time constant of LV isovolumetric relaxation (tau). LV ejection time decreased 23 +/- 10 ms (p < 0.05) and RV ejection time did not change. Baroreflex sensitivity was similar during pressure fall and recovery (6.4 +/- 4.5 vs. 6.1 +/- 3.6 ms/mmHg), however hysteresis (p < 0.05) was noted. Aortic pressure waveforms also changed following ANI. Changes were determined to be in part a consequence of the attenuation and delay in arterial wave reflections. This study extends the understanding of the complex nature of the hemodynamic response associated with ANI.

Administration, Inhalation↗
PubMed1993

Changing presentation of coronary heart disease in an inpatient population within the U.S. military health care system.

This study examines the changing presentation of coronary heart disease (CHD) in an inpatient population at Brooke Army Medical Center. The specific objectives of the study were to examine the presentation of CHD in a population unbiased by diagnosis-related group (DRG) reimbursements and to assess the importance of unstable angina and prior history of disease in the presentation of CHD. One thousand fifteen discharges in 1985 and 1,304 discharges in 1990 with the diagnosis of CHD were reviewed by cardiologists for evidence of symptomatic heart disease at the time of hospitalization. Forty percent of these charts were accepted into this study. The presentation rates of CHD were 1% with sudden death, 26% with myocardial infarction, 64% with angina, and 9% with congestive heart failure (CHF). During the study period, stable angina, Q-wave infarctions, and the myocardial infarction case fatality rate decreased (p < 0.05) and CHF and non-Q wave infarcts increased (p < 0.001). However, unstable angina was the most common presentation of CHD, and differences (p < 0.05) were noted in the presentation of CHD in patients with and without a prior history of disease. This study demonstrates the significance of unstable angina and prior history of CHD in an environment free of bias from DRG reimbursements.

Adult↗
PubMed1993

Comparison of short-time Fourier, wavelet and time-domain analyses of intracardiac sounds.

Heart sounds provide clinicians with valuable diagnostic and prognostic information. They are repetitive in nature, but reflect complex mechano-acoustical events which have been inadequately described by traditional digital signal processing methods. In this study, left ventricular and aortic intravascular phonocardiograms were obtained from six patients by catheter-mounted piezoelectric transducers. Phonocardiograms (PCGs) were bandpass filtered (50-500 Hz), digitized at 4kHz and analyzed by three separate techniques: (1) Short-Time Fourier Transform (STFT), (2) Fast Wavelet Transform (FWT), and (3) a pulse-counting time-domain method based on an Order Statistic (OS) filter. The resulting time-frequency distributions were employed to examine intra-patient and inter-patient acoustic variability. Results suggest that STFT and FWT provide comparable temporal and frequency resolution of cardiac acoustical events. However, the time-varying and multicomponent nature of heart sounds was poorly characterized by the OS technique employed in this study. This study suggests that improved localization of acoustic events during the cardiac cycle may prove useful in the development of automated auscultation devices.

Adult↗
PubMed1991

Effects of respiration on size and function of the athletic heart.

This study compares the effects of quiet breathing on the heart structure and function of pentathlon athletes (n = 11) and a less-conditioned control group (n = 12). Two-dimensional echocardiography was employed to direct an M-mode beam through the heart to minimize measurement errors due to respiratory motion of the heart. Respiration was simultaneously recorded with M-mode echocardiograms from a minimum of five respiratory and an average of 25 cardiac cycles. Athletes had greater (p less than 0.01) end-diastolic transverse dimensions (10%), and interventricular septal and left ventricular posterior wall thicknesses (25%). During inspiration right ventricular internal end-diastolic dimensions increased (8 vs 12%) and left ventricular end-diastolic dimension (LVIDd) decreased (7 vs 8%) in athletes and controls, respectively. Although significant reciprocal changes in LVIDd (p less than 0.01) occurred during respiration, no respiratory change was noted in the transverse diameter of the heart, interventricular septal, posterior wall thickness, LV end-systolic volume or ejection fraction. Inspiration caused a 21% fall (p less than 0.01) in LV stroke volume in both groups. Eighty-four to 92% of the inspiratory decrease in LV stroke volume in the subjects studied could be attributed to ventricular interdependence; no significant interaction was found between level of conditioning and respiration.

Echocardiography↗
PubMed1990

Isolated aorta setup for hemodynamic studies.

A setup consisting of a high-performance hydraulic pump connected to the ascending part of an isolated aorta, including all major distal branches, each loaded with calibrated artificial resistors, was developed. The system was used to study total aortic compliance of the baboon as a function of mean aortic pressure (n = 5). The aorta loaded with the resistors was mounted in a custom-designed sink table, such that it was submersed in physiological saline maintained at 37 degrees C. Mean distending pressure in the entire aorta could be varied. The three-element Windkessel model was used to estimate total aortic compliance from pressure and flow waves generated by the pump. Total aortic compliance as a function of mean pressure was fitted with a logarithmic function: Ln(Compliance) = A + B * P. The value of A (+/- SE) was: 1.565 +/- 0.319 and B: -0.020 +/- 0.003 (P less than 0.001). The results were compared with previously published results (also using the same three-element Windkessel fit) obtained in three of the same animals in vivo. The in vivo data were A: 1.095 +/- 0.235 and B: B: -0.019 +/- 0.003. In vitro data had a significantly higher value of A than in vivo (P = 0.017), implying a significantly higher aortic compliance in vitro than in vivo. Occlusion of the proximal descending aorta was performed at a low distending pressure (55 mm Hg) to determine the proximal compliance. It was found (n = 4) that 46 +/- 11% (SD) of the total arterial compliance is to be attributed to the ascending and proximal descending aorta.

Animals↗
PubMed1989

Comparison of the frequency response characteristics of catheter-mounted piezoelectric and micromanometric phonotransducers.

This study compares the frequency response characteristics of catheter-mounted piezoelectric sound transducers with micromanometric transducers. The tip of a 8F catheter with two piezoelectric transducers and two micromanometers was inserted into a water-filled chamber that had a speaker fixed at one end. The speaker was driven by a power amplifier and sine wave generator. The outputs of the transducers were connected to a low-level amplifier. The piezoelectric transducer behaved as a tunable high-pass filter that could be modified by altering the input impedance of the low level amplifier; the frequency response characteristics were examined at five input impedances ranging from 0.96 to 11.8 megohms. The peak-to-peak outputs of the piezoelectric and pressure transducers were recorded at frequency ranges from DC to 1 kHz with a wide-band oscilloscope. The ratio of the outputs from the piezotransducer and micromanometer (Vph/Vpr) was plotted vs. frequency for each input impedance and analyzed to determine the piezotransducer's output resistance and equivalent capacitance; roll-off frequencies were then calculated. The equivalent capacitance of the piezo-element was determined to be 500-700 picofarads. Series capacitance acted with network resistance to produce a predictable frequency-dependent change in signal amplitude and phase angle. The inherent noise of the pressure transducer was found to be approximately 0.2 mm Hg, while the noise of the piezoelectric transducer was immeasurably low. The piezoelectric phonotransducers were superior to micromanometer transducers in their higher gain and lower noise, suggesting that these transducers may prove useful to physiologic and clinical studies for measuring intravascular sound.

Cardiac Catheterization↗
PubMed1989

Effects of pneumatic antishock garment inflation in normovolemic subjects.

This study examines the effects of inflation of pneumatic antishock garments (PASG) in 10 normovolemic men (mean age 44 +/- 6 yr) undergoing diagnostic catheterization. Seven subjects had normal heart function and no evidence of coronary artery disease (CAD); three patients had CAD. High-fidelity multisensor catheters were employed to simultaneously record right and left heart pressures before PASG inflation and after inflation to 40, 70, and 100 mmHg. A thermal dilution catheter was used to obtain pulmonary capillary wedge pressure and cardiac output. Counterpressure increases greater than or equal to 40 mmHg were associated with significant changes in left and right heart pressures. Right and left ventricular end-diastolic pressures increased 100% (P less than 0.01); mean pulmonary arterial and aortic pressures increased 77 and 25%, respectively (P less than 0.01); systemic vascular resistance increased 22% (P less than 0.05) and pulmonary vascular resistance did not change in normal subjects at maximum PASG inflation. Heart rate, cardiac output, and aortic and pulmonary arterial pulse pressures did not change during inflation in either group. Right and left ventricular end-diastolic pressures and pulmonary capillary wedge pressure were greater (P less than 0.05) in the CAD group compared with the normal subjects during PASG inflation. The data suggest that the primary mechanism whereby PASG inflation induces changes in central hemodynamics in normovolemic subjects is through an acute increase in left ventricular afterload. PASG changes in afterload and pulmonary capillary wedge pressure imply that these devices should be used with caution in patients with compromised cardiac function.

Adult↗
PubMed1989

Heart size and function of soldiers, athletes, and sedentary men.

This study compares the heart sizes and left ventricular masses of soldiers (n = 11) with age- and body size-matched groups of sedentary men (n = 10) and accomplished athletes (n = 11). Echocardiography revealed that active duty soldiers (A) who met minimal fitness standards and pentathletes (P) had greater average left ventricular (LV) end-diastolic volumes (A = 10%, NS; P = 28%, p less than 0.05), stroke volumes (A = 29%, NS; P = 44%, p less than 0.01), and LV masses (A = 22%, NS; P = 76%, p less than 0.01) than sedentary subjects. Athletes had an average LV wall thickness which was 23% (p less than 0.05) greater than that of soldiers and 32% (p less than 0.01) greater than that of sedentary men. The LV wall thickness to radius ratio (h/r) was similar between soldiers and sedentary men, but in athletes the h/r was greater (p less than 0.01) than in the less conditioned subjects. These data suggest that soldiers who meet minimal standards of fitness exhibit cardiac morphometric features consistent with endurance conditioning. However, the soldiers studied were significantly less (p less than 0.001) conditioned than the competitive athletes. These data suggest that improvements in aerobic and cardiac conditioning could be achieved through a greater emphasis on physical training.

Age Factors↗
PubMed1988

Aortic input impedance during Mueller maneuver: an evaluation of "effective length".

Aortic input impedance was calculated in seven subjects in the control state (normal reflection) and during the Mueller maneuver (increased reflection) to evaluate "effective arterial length" under altered physiological conditions. Regional foot-to-foot pulse wave velocities and pressure waveforms along the aorta were used to define an "apparent anatomic length" or distance to a dominant discrete site of reflection "seen" by the ejecting ventricle. Time of wave travel was taken to be one-half the interval from the foot of the incident wave to the midsystolic inflection point. Knowing the time of travel from the returning reflection and velocity, distances calculated to the "apparent anatomic length" were 35 +/- 2 and 34 +/- 2 during control and Mueller maneuver, respectively (P = NS). The frequency of the first minimum of the modulus (fmin) and the first zero crossing of the phase angle (f phi) were determined from the input impedance spectra. During baseline conditions, fmin (3.9 +/- 0.2 Hz) approximately equaled f phi (4.2 +/- 0.2 Hz), and the resulting "effective lengths" calculated using the quarter-wavelength formula were similar to the apparent anatomic length. These data suggested that the aortic region incorporating the renal arterial branches as a site of discrete reflection and that terminal load was not significantly frequency dependent. During Mueller maneuver, however, f min (3.3 +/- 0.2 Hz) and f phi (5.1 +/- 0.2 Hz) were significantly discordant, the terminal load became strongly frequency dependent, and effective length calculated from f min was dissimilar (P less than 0.05) from the unchanged apparent anatomic length.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Ventricular/vascular coupling and regional arterial dynamics in the chronically hypertensive baboon: correlation with cardiovascular structural adaptation.

Ventricular/vascular coupling dynamics and regional hemodynamics of five hypertensive baboons with concentric left ventricular (LV) hypertrophy (mean arterial pressure +/- SD, 148 +/- 16 mm Hg; LV mass/body weight ratio 3.42 +/- 0.8) were compared with five normotensive controls (mean arterial pressure 89 +/- 3 mm Hg; LV mass/body wt ratio 2.73 +/- 0.5) at different mean arterial pressures. Ventricular/vascular dynamics were assessed by aortic input impedance, pulsatile/total power ratio, effective arterial elastance and compliance from a three-element Windkessel "lumped" model of the circulation. Regional arterial dynamics were assessed by pulse-wave velocities and local reflection coefficients. Systemic arterial compliance was similarly decreased with elevated pressure in both groups but was significantly more reduced for the hypertensive group compared with control animals at control (0.49 +/- 0.16 vs. 0.96 +/- 0.09 ml/mm Hg; p less than 0.05) and acutely lowered arterial pressure (0.62 +/- 0.26 vs. 1.41 +/- 0.24 ml/mm Hg, respectively). Changes in compliance were paralleled by differences in effective arterial elastance derived from cineventriculographic pressure-volume ratios. Regional foot-foot and apparent phase pulse-wave velocities were significantly increased for distal aortic segments of the hypertensive animals during elevated pressures compared with controls (cff, 17.5 +/- 7.5 vs. 8.7 +/- 3.0 m/sec; p less than 0.05). Histology of the aorta revealed significant increases in collagen content (microgram/mg dry wt) from proximal to distal aortic segments (27 +/- 2 vs. 38 +/- 6; p less than 0.005) in hypertensive animals but not in controls (27 +/- 2 vs. 32 +/- 6; NS). With pharmacological normalization of systemic arterial pressures, hypertensive baboons developed aortic wave speeds similar to controls but manifested significantly reduced compliance compared with controls. In contrast, with acute elevations of pressure, systemic arterial aortic compliances were similar for both groups, but distal pulse-wave velocities were significantly increased for hypertensive animals compared with controls. We conclude that measures of ventricular/vascular coupling and arterial dynamics are determined by both the level of arterial pressure and the physical characteristics of the cardiovascular system in chronic systemic hypertension and pressure overload ventricular hypertrophy.

Adaptation, Physiological↗
PubMed1987

Nonhuman primate model for regional wave travel and reflections along aortas.

Arterial pulse transmission and wave reflections were studied in five mature anesthetized baboons (Papio anubis) using multisensor micromanometry. Simultaneous pressures were recorded from the left ventricle and every 10 cm along the aorta and its terminal branches, and flow velocity was measured in the aortic root. Aortic input impedance and regional foot-to-foot and apparent phase velocities were calculated. Aortography provided dimensional data for local reflection coefficients. Regional foot-to-foot wave speeds were somewhat lower than corresponding segments in humans. Proximal aortic pressure waveforms and characteristic impedance (110 +/- 29 dyn X s X cm-5) were not characteristic of middle-aged humans. Reflection coefficients at the terminal aortic bifurcation (0.06) at the level of the renal artery branches (0.09) were less than those found in humans. We conclude that the junction of the renal artery branches and the aorta in the baboon is closely matched and represents much less of a discrete reflection site than in humans. Although the baboon may be used to study pulse transmission characteristics in the baboon, this species is not a good model for the proximal systemic reflective characteristics of normal middle-aged humans.

Animals↗
PubMed1987

Effects of physical conditioning on the heart size and wall thickness of college women.

M-mode echocardiograms were obtained from 40 sedentary college women, 8 sprinters, 6 distance runners, 10 swimmers, 9 basketball players, 8 dancers, and 10 sedentary men (ages 19 to 31 yr). Treadmill stress tests were performed by all groups except the basketball players. The aerobic capacities of the athletes were 30 to 48% greater (P less than 0.05) than the sedentary subjects. The athletes exhibited trends toward higher than average left ventricular (LV) end-diastolic dimensions (7 to 25%), LV end-diastolic volumes (12 to 53%), stroke volume (13 to 52%), LV mass (11 to 42%), and left atrial dimensions (6 to 31%) when data were standardized for body surface area. A correlation (r = 0.323, P less than 0.05) was noted between LV mass index and maximal oxygen uptake when data were pooled. Ten sedentary women and ten age-matched sedentary men were endurance-conditioned by 10 wk of running. Both sexes increased maximal oxygen uptake approximately 20% (P less than 0.05) and exhibited similar changes in LV wall thickness, end-diastolic dimension, end-diastolic volume, and mass. These changes regressed within 10 wk after the termination of conditioning. This study suggests that women athletes exhibit cardiac morphologic features which resemble that reported for their male counterparts and that the cardiac response of sedentary men and women to modest levels of endurance conditioning is similar.

Adult↗