Continuous cardiac output monitoring by blood pressure analysis.
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Blood Pressure↗
Biomedical subjects
Jos R C Jansen
Publications and source records attributed to Jos R C Jansen.
Breath-to-breath analysis of abdominal and rib cage motion in surfactant-depleted piglets during high-frequency oscillatory ventilation.
OBJECTIVE: To assess the value of monitoring abdominal and rib cage tidal displacement as an indicator of optimal mean airway pressure (Paw) during high-frequency oscillatory ventilation (HFOV). DESIGN AND SETTING: Prospective observational study in a university research laboratory. ANIMALS: Eight piglets weighing 12.0+/-0.5 kg, surfactant depleted by lung lavage. INTERVENTIONS: Compliance of the respiratory system (C(rs)) was calculated from a quasistatic pressure volume loop. After initiation of HFOV lung volume was recruited by increasing Paw to 40 cmH(2)O. Then mean Paw was decreased in steps until PaO(2)/FIO(2) was below 100 mmHg. Proximal pressure amplitude remained constant. MEASUREMENTS AND RESULTS: Abdominal and rib cage tidal displacement was determined using respiratory inductive plethysmography. During HFOV there was maximum in tidal volume (Vt) in seven of eight piglets. At maximal mean Paw abdominal and rib cage displacement were in phase. Phase difference between abdominal and rib cage displacement increased to a maximum of 178+/-28 degrees at minimum mean Paw. A minimum in abdominal displacement and a maximum of Vt was found near the optimal mean Paw, defined as the lowest mean Paw where shunt fraction is below 0.1. CONCLUSIONS: During HFOV abdominal and rib cage displacement displayed mean Paw dependent asynchrony. Maximal Vt and minimal abdominal displacement coincided with optimal C(rs), oxygenation, and ventilation, suggesting potential clinical relevance of monitoring Vt and abdominal displacement during HFOV.
Abdomen↗
Beat-to-beat effects of intraaortic balloon pump timing on left ventricular performance in patients with low ejection fraction.
BACKGROUND: Intraaortic balloon counterpulsation (IABP) timing errors during arrhythmia may result in afterload increases which may negatively influence left ventricular (LV) ejection and LV mechanical dyssynchrony. The aim of our study was to determine beat-to-beat effects of properly timed IABP, premature IAB inflation, and late IAB deflation on LV performance and LV mechanical dyssynchrony in heart failure patients undergoing cardiac surgery. METHODS: In 15 patients, LV pressure-volume relations and LV dyssynchrony were measured by conductance volume catheter. Properly timed IABP was evaluated at a 1:1 assist ratio within a 10 seconds time-span. Premature IAB inflation and late IAB deflation were evaluated at a 1:4 assist ratio. RESULTS: Properly timed 1:1 IABP acutely decreased LV end-systolic volume by 6.1% (p < 0.0001) and LV end-systolic pressure by 17.5% (p < 0.0001) due to decreased aortic impedance. Stroke volume (SV) increased by 14% (p < 0.0001), which correlated markedly with a decrease of LV mechanical dyssynchrony (p < 0.0001). The largest SV increases occurred in patients with lowest contractile state. Premature IAB inflation decreased SV by 20% (p < 0.0001) due to abrupt increase of LV afterload during late ejection. Late IAB deflation increased SV and stroke work by 18% (p < 0.0001) and 16% (p < 0.01) respectively, due to increased afterload during early ejection and decreased afterload during late ejection. CONCLUSIONS: Left ventricular performance during IABP is causally related to changes in LV afterload, and the timing of these changes in relation to contraction or relaxation phases, to LV mechanical dyssynchrony and to contractile state.
Humans↗
Automatic intraaortic balloon pump timing using an intrabeat dicrotic notch prediction algorithm.
PURPOSE: The efficacy of intraaortic balloon counterpulsation (IABP) during arrhythmic episodes is questionable. A novel algorithm for intrabeat prediction of the dicrotic notch was used for real time IABP inflation timing control. DESCRIPTION: A windkessel model algorithm was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was predicted using a percentage of calculated peak flow. Automatic inflation timing was set at intrabeat predicted dicrotic notch and was combined with automatic IAB deflation. EVALUATION: Prophylactic IABP was applied in 27 patients with low ejection fraction (< 35%) undergoing cardiac surgery. Analysis of IABP at a 1:4 ratio revealed that IAB inflation occurred at a mean of 0.6 +/- 5 ms from the dicrotic notch. In all patients accurate automatic timing at a 1:1 assist ratio was performed. Seventeen patients had episodes of severe arrhythmia, the novel IABP inflation algorithm accurately assisted 318 of 320 arrhythmic beats at a 1:1 ratio. CONCLUSIONS: The novel real-time intrabeat IABP inflation timing algorithm performed accurately in all patients during both regular rhythms and severe arrhythmia, allowing fully automatic intrabeat IABP timing.
Aged↗
Regional lung volume during high-frequency oscillatory ventilation by electrical impedance tomography.
OBJECTIVE: To investigate the value of electrical impedance tomography for the assessment of regional lung mechanics during high-frequency oscillatory ventilation (HFOV). DESIGN: Prospective, interventional animal study. SETTING: University research laboratory. SUBJECTS: Eight pigs with lavage-induced lung injury. INTERVENTIONS: Electrical impedance tomography measurements were performed during a pressure-volume maneuver and during a recruitment-derecruitment maneuver on HFOV by stepwise variation of continuous distending pressure (CDP). MEASUREMENTS AND MAIN RESULTS: Lung volume was estimated by calibrated strain-gauge plethysmography; regional lung volume changes were assessed by electrical impedance tomography in various regions of interest. We found that inflation during the pressure-volume maneuver was distributed nonhomogeneously, whereas deflation was homogeneous. During HFOV, no major regional differences were found during either inflation or deflation. The upper inflection point on the deflation limb was at a slightly higher continuous distending pressure (26+/-3 cm H2O) than the minimal physiologic shunt fraction (at continuous distending pressure of 23+/-7), where there were hemodynamic signs of overdistension. Maximal compliance on the deflation limb (at continuous distending pressure of 13+/-3 cm H2O) agreed well with the minimal continuous distending pressure, where shunt fraction was just below 0.1 (14+/-2 cm H2O). CONCLUSIONS: HFOV has a homogenizing effect on lung volume distribution. Regional lung volume distribution can be assessed using electrical impedance tomography. However, thoracic fluid accumulation may complicate its interpretation.
Animals↗
Estimation of regional lung volume changes by electrical impedance pressures tomography during a pressure-volume maneuver.
OBJECTIVE: To assess the degree of linearity between lung volume and impedance change by electrical impedance tomography (EIT) in pigs with acute lung injury and to investigate regional impedance changes during a pressure-volume maneuver. DESIGN AND SETTING: Experimental animal study in a university research laboratory. PATIENTS AND PARTICIPANTS: Nine pigs with lung injury induced by lung lavage. INTERVENTIONS: The lungs were insufflated to four different lung volumes. Next the lungs were inflated in steps up to 40 cm H(2)O and then in steps deflated. MEASUREMENTS AND RESULTS: EIT measurements were performed. Impedance was highly linear with lung volume ( r(2)=0.97). From the pressure-volume maneuver regional pressure-impedance (P-I) curves were obtained in the upper half (ventral) and lower half (dorsal) of the thoracic cross-section. Excellent fit was found of the regional P-I curves with a predefined sigmoid equation ( r(2)=0.998). The P-I curves after lavage were markedly different than before lavage. The P-I curves recorded after lavage displayed a strong heterogeneity on the inflation limb: Lower corner pressure (traditionally lower inflection point) was significantly higher in the dorsal (28.3+/-4.1 cm H(2)O) than in the ventral region (17.5+/-4.3 cm H(2)O). The deflation limb displayed a more homogeneous pattern. Upper corner pressure and true inflection point, where the curve slope is maximal, in the dorsal region were only slightly higher than in the ventral region (1-2 cm H(2)O). CONCLUSIONS: EIT and automated curve fitting provide information on regional lung inflation and deflation which may be of clinical use for optimizing ventilator settings.
Airway Resistance↗
Oxygenation index, an indicator of optimal distending pressure during high-frequency oscillatory ventilation?
OBJECTIVE: To test the hypothesis that, during high-frequency oscillatory ventilation (HFOV) of pigs with acute lung injury, the oxygenation index (OI = Paw*FIO(2)*100/PaO(2)) is minimal at the lowest continuous distending pressure (Paw), where the physiological shunt fraction is below 0.1 (Paw(optimal)). DESIGN AND SETTING: Prospective, observational study in a university research laboratory. SUBJECTS: Eight Yorkshire pigs weighing 12.0+/-0.5 kg, with lung injury induced by lung lavage. INTERVENTIONS: After initiation of HFOV, the pigs were subjected to a stepwise increase of Paw to obtain under-inflation, optimal inflation and over-distension of the lungs (inflation) in series, followed by a similar decrease of Paw (deflation). MEASUREMENTS AND RESULTS: At each Paw level, the OI and physiological shunt fraction were determined. The OI reached a minimum of 6.2+/-1.4 at Paw 30+/-4 cmH(2)O during inflation and a minimum of 2.4+/-0.3 at Paw 13+/-2 cmH(2)O during deflation. Paw(optimal) was 32+/-6 cmH(2)O on the inflation limb and 14+/-2 cmH(2)O on the deflation limb. The difference between the Paw at minimal OI and Paw(optimal) was -1.9+/-4.2 cmH(2)O (NS) during inflation and -1.5+/-1.6 cmH(2)O (p<0.05) during deflation. In 15 out of the 16 comparisons, the difference in Paw was within one step (+/-3 cmH(2)O). CONCLUSION: The minimal OI is indicative for the Paw where oxygenation is optimal during HFOV in surfactant-depleted pigs.
Animals↗
Feasibility study of a fiber-optic system for invasive blood pressure measurements.
A comparative study was conducted to evaluate the feasibility of a fiber-optic sensor in invasive blood pressure measurements. Static and wide-bandwidth stimuli were offered to the fiber-optic, Millar, Baxter, and Sentron devices to measure static transfer function and transient response. Animal experiments focused on offset drift, dynamic accuracy, and electromagnetic sensitivity. Compared to the Millar, Sentron, and Baxter devices, the fiber-optic sensor had a near-identical static transfer function. Gain and offset errors were < 3.4% and < 0.25%, respectively. Hysteresis nonlinearity was < 0.1%. The dynamic accuracy of the fiber-optic system matched that of the Millar and Sentron systems. Time delay was < 1 msec. Maximum rate of change was > 30,000 mm Hg/sec and bandwidth was 0-150 Hz minimum. Offset drift was 0.6 +/- 0.03 mm Hg. Application of diathermy highlighted the fiber-optic sensor's excellent electromagnetic disturbance rejection. The fiber-optic system appears to be a reliable, high-fidelity pressure monitor in demanding clinical environments.
Animals↗
Attenuation of pressure swings along the endotracheal tube is indicative of optimal distending pressure during high-frequency oscillatory ventilation in a model of acute lung injury.
We tested the hypothesis that during high-frequency oscillatory ventilation, the oscillatory pressure ratio (OPR) is minimal at the optimal mean airway pressure (Paw). OPR is defined as the ratio of pressure swings at the distal end and the proximal opening of the endotracheal tube. Optimal Paw was assumed to be the lowest Paw at which the physiological shunt fraction was below 0.1. Acute lung injury was produced by saline lung lavage of pigs who were then subjected to a stepwise increase of Paw to impose underinflation, optimal inflation, and overdistention (inflation phase), followed by a stepwise decrease of Paw (deflation phase). OPR reached a minimum of 0.10 +/- 0.01 at Paw = 31 +/- 4 cm H(2)O during the inflation phase and a minimum of 0.04 +/- 0.01 at Paw = 18 +/- 1 cm H(2)O during the deflation phase. Optimal Paw was 31 +/- 4 cm H(2)O on the inflation limb and 14 +/- 2 cm H(2)O on the deflation limb. Paw at the minimal OPR was not significantly different from the optimal Paw during the inflation phase, and slightly but significantly higher (4.1 +/- 1.6 cm H(2)O) during the deflation phase. In conclusion, a consistent relationship was found between OPR and Paw, with a minimum in all animals. The minimal OPR coincides fairly well with the Paw where oxygenation is optimal.
Animals↗
Effect of positive pressure on venous return in volume-loaded cardiac surgical patients.
The hemodynamic effects of increases in airway pressure (Paw) are related in part to Paw-induced increases in right atrial pressure (Pra), the downstream pressure for venous return, thus decreasing the pressure gradient for venous return. However, numerous animal and clinical studies have shown that venous return is often sustained during ventilation with positive end-expiratory pressure (PEEP). Potentially, PEEP-induced diaphragmatic descent increases abdominal pressure (Pabd). We hypothesized that an increase in Paw induced by PEEP would minimally alter venous return because the associated increase in Pra would be partially offset by a concomitant increase in Pabd. Thus we studied the acute effects of graded increases of Paw on Pra, Pabd, and cardiac output by application of inspiratory-hold maneuvers in sedated and paralyzed humans. Forty-two patients were studied in the intensive care unit after coronary artery bypass surgery during hemodynamically stable, fluid-resuscitated conditions. Paw was progressively increased in steps of 2 to 4 cmH(2)O from 0 to 20 cmH(2)O in sequential 25-s inspiratory-hold maneuvers. Right ventricular (RV) cardiac output (CO(td)) and RV ejection fraction (EF(rv)) were measured at 5 s into the inspiratory-hold maneuver by the thermodilution technique. RV end-diastolic volume and stroke volume were calculated from EF(rv) and heart rate data, and Pra was measured from the pulmonary artery catheter. Pabd was estimated as bladder pressure. We found that, although increasing Paw progressively increased Pra, neither CO(td) nor RV end-diastolic volume changed. The ratio of change (Delta) in Paw to Delta Pra was 0.32 +/- 0.20. The ratio of Delta Pra to Delta CO(td) was 0.05 +/- 00.15 l x min(-1) x mmHg(-1). However, Pabd increased such that the ratio of Delta Pra to Delta Pabd was 0.73 +/- 0.36, meaning that most of the increase in Pra was reflected in increases in Pabd. We conclude that, in hemodynamically stable fluid-resuscitated postoperative surgical patients, inspiratory-hold maneuvers with increases in Paw of up to 20 cmH(2)O have minimal effects on cardiac output, primarily because of an in-phase-associated pressurization of the abdominal compartment associated with compression of the liver and squeezing of the lungs.
Abdomen↗
Performance of a real-time dicrotic notch detection and prediction algorithm in arrhythmic human aortic pressure signals.
A novel algorithm for real-time detection and prediction of the dicrotic notch from aortic pressure waves was evaluated in arrhythmic aortic pressure signals from heart failure patients. A simplified model of the arterial tree was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was detected at the first negative dip from the calculated flow, prediction of the notch was performed using a percentage of the decreasing flow. The performance of the real-time dicrotic notch detection algorithm (RTDND) was evaluated during severe arrhythmia from aortic pressure signals of 12 patients. The RTDND was able to detect the dicrotic notch in 98.1%. No false positive dicrotic notch identifications were observed. Prediction of the dicrotic notch was tested at 40%, 20%, and 0% of the decreasing calculated aortic flow. The mean time-delays to the notch were 68 +/- 14 ms, 55 +/- 12 ms, and 43 +/- 8 ms, respectively. Given these small variability, intra-beat prediction of the dicrotic notch may be used for real-time intra-aortic balloon counterpulsation inflation timing.
Aged↗