The Effects of Heart Rhythm Meditation on Vagal Tone and Well-being: A Mixed Methods Research Study.

Many studies have examined the effects of meditation practice focused on the normal breath on vagal tone with mixed results. Heart Rhythm Meditation (HRM) is a unique meditation form that engages in the deep slow full breath, and puts the focus of attention on the heart. This form of breathing likely stimulates the vagus nerve with greater intensity. The purpose of this study was (a) to examine how the practice of HRM affects vagal activity as measured by heart rate variability (HRV); and (b) to examine how it affects participants' well-being. 74 participants signed consent agreeing to: (a) take a six-week course to learn the practice of HRM; (b) engage in a daily practice for 10 weeks; (c) have their heart rate variability read through ECG technology and to take two validated well-being instruments at the beginning and end of the 10 weeks; and (d) participate in a focus group interview examining their perceptions of how the practice affected their well-being. 48 participants completed the study. Quantitative findings show the effect of the practice of HRM approached significance for multiple measures of HRV and vagal tone. An increase in well-being scores for those who did the meditation more than 10-minutes per day did meet statistical significance. Qualitative data indicate: (a) the positive effects of HRM on stress and well-being; (b) the development of a more expanded sense of self; and (c) an increased awareness of the interconnection of the body-heart-emotions and HRM's role in emotion regulation.

Treatment of relapsing multiple sclerosis - recommendations of the Croatian Neurological Society.

Untreated multiple sclerosis (MS) irretrievably leads to severe neurological impairment. In European health care systems, patient access to disease modifying therapies (DMT) is often confined to more advanced stages of the disease because of restrictions in reimbursement. A discrepancy in access to DMTs is evident between West and East European countries. In order to improve access to DMTs for people with MS (pwMS) living in Croatia, the Croatian Neurological Society issued new recommendations for the treatment of relapsing MS. The aim of this article is to present these recommendations. The recommendations for platform therapies are to start DMT as soon as the diagnosis is made. If poor prognostic criteria are present (≥9 T2 or FLAIR lesions on the initial brain and spinal cord magnetic resonance imaging [MRI] or ≥3 T1 lesions with postcontrast enhancement on the initial brain and spinal cord MRI or Expanded Disability Status Scale after treatment of the initial relapse ≥3), high-efficacy DMT should be initiated. If pwMS experience ≥1 relapse or ≥3 new T2 lesions while on platform therapies, they should be switched to high-efficacy DMT. Further efforts should be made to enable early and unrestricted access to high-efficacy DMT with a freedom of choice of an appropriate therapy for expert physicians and pwMS. The improvement of access to DMT achieved by the implementation of national treatment guidelines in Croatia can serve as an example to national neurological societies from other Eastern European countries to persuade payers to enable early and unrestricted treatment of pwMS.

Stress and Exposure Time on von Willebrand Factor Degradation.

Despite the prevailing use of the continuous flow left ventricular assist devices (cf-LVAD), acquired von Willebrand syndrome (AvWS) associated with cf-LVAD still remains a major complication. As AvWS is known to be dependent on shear stress (τ) and exposure time (texp ), this study examined the degradation of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in terms of τ and texp . Two custom apparatus, i.e., capillary-tubing-type degrader (CTD) and Taylor-Couette-type degrader (TCD) were developed for short-term (0.033 sec ≤ texp  ≤ 1.05 s) and long-term (10 s ≤ texp  ≤ 10 min) shear exposures of vWF, respectively. Flow conditions indexed by Reynolds number (Re) for CTD were 14 ≤ Re ≤ 288 with corresponding laminar stress level of 52 ≤  τ CTD  ≤ 1042 dyne/cm2 . Flow conditions for TCD were 100 ≤ Re ≤ 2500 with corresponding rotor speed of 180 ≤ o  ≤ 4000 RPM and laminar stress level of 50 ≤  τ TCD  ≤ 1114 dyne/cm2 . Due to transitional and turbulent flows in TCD at Re > 1117, total stress (i.e., τ total  = laminar + turbulent) was also calculated using a computational fluid dynamics (CFD) solver, Converge CFD (Converge Science Inc., Madison, WI, USA). Inhibition of ADAMTS13 with different concentration of EDTA (5 mM and 10 mM) was also performed to investigate the mechanism of cleavage in terms of mechanical and enzymatic aspects. Degradation of HMWM with CTD was negligible at all given testing conditions. Although no degradation of HMWM was observed with TCD at Re < 1117 ( τ total  = 1012 dyne/cm2 ), increase in degradation of HMWM was observed beyond Re of 1117 for all given exposure times. At Re ~ 2500 ( τ total  = 3070 dyne/cm2 ) with texp  = 60 s, a severe degradation of HMWM (90.7 ± 3.8%, abnormal) was observed, and almost complete degradation of HMWM (96.1 ± 1.9%, abnormal) was observed with texp  = 600 s. The inhibition studies with 5 mM EDTA at Re ~ 2500 showed that loss of HMWM was negligible (<10%, normal) for all given exposure times except for texp  = 10 min (39.5 ± 22.3%, borderline-abnormal). With 10 mM EDTA, no degradation of HMWM was observed (11.1 ± 4.4%, normal) even for texp  = 10 min. This study investigated the effect of shear stress and exposure time on the HMWM of vWF in laminar and turbulent flows. The inhibition study by EDTA confirms that degradation of HMWM is initiated by shear-induced unfolding followed by enzymatic cleavage at given conditions. Determination of magnitude of each mechanism needs further investigation. It is also important to note that the degradation of vWF is highly dependent on turbulence regardless of the time exposed within our testing conditions.

Development of the PSU Child Pump.

The Pennsylvania State University (PSU) Child Pump, a centrifugal continuous-flow ventricular assist device (cf-VAD), is being developed as a suitable long-term implantable device for pediatric heart failure patients between 10 and 35 kg, body surface area (BSA) of 0.5-1.2 m2, 1-11 years of age, and requiring a mean cardiac output of 1.0-3.5 L/min. In-vitro hydraulic and hemodynamic performances were evaluated on a custom mock circulatory loop with ovine blood. Normalized index of hemolysis (NIH) was evaluated under four conditions: 1) 8,300 rpm, 3.5 L/min, ΔP = 60 mm Hg, 2) 8,150 rpm, 5.1 L/min, ΔP = 20 mm Hg, 3) 8,400 rpm, 3.2 L/min, ΔP = 70 mm Hg, and 4) 9,850 rpm, 5.0 L/min, ΔP = 80 mm Hg, resulting in normalized index of hemolysis = 0.027 ± 0.013, 0.015 ± 0.006, 0.016 ± 0.008, and 0.026 ± 0.011 mg/dl, respectively. A mock fit study was conducted using a three-dimensional printed model of a 19 kg patient's thoracic cavity to compare the size of the PSU Child Pump to the HeartMate3 and the HVAD. Results indicate the PSU Child Pump will be a safer, appropriately sized device capable of providing the given patient cohort proper support while minimizing the risks of blood trauma as they wait for a transplant.

Kinetic and Dynamic Effects on Degradation of von Willebrand Factor.

The loss of high molecular weight multimers (HMWM) of von Willebrand factor (vWF) in aortic stenosis (AS) and continuous-flow left ventricular assist devices (cf-LVADs) is believed to be associated with high turbulent blood shear. The objective of this study is to understand the degradation mechanism of HMWM in terms of exposure time (kinetic) and flow regime (dynamics) within clinically relevant pathophysiologic conditions. A custom high-shear rotary device capable of creating fully controlled exposure times and flows was used. The system was set so that human platelet-poor plasma flowed through at 1.75 ml/sec, 0.76 ml/sec, or 0.38 ml/sec resulting in the exposure time ( texp ) of 22, 50, or 100 ms, respectively. The flow was characterized by the Reynolds number (Re). The device was run under laminar (Re = 1,500), transitional (Re = 3,000; Re = 3,500), and turbulent (Re = 4,500) conditions at a given texp followed by multimer analysis. No degradation was observed at laminar flow at all given texp . Degradation of HMWM at a given texp increases with the Re. Re ( p < 0.0001) and texp ( p = 0.0034) are significant factors in the degradation of HMWM. Interaction between Re and texp , however, is not always significant ( p = 0.73).

Miniaturized Fontan Circulation Assist Device: Chronic In Vivo Evaluation.

We have miniaturized and optimized our implantable rotary blood pump developed to provide long-term mechanical right heart support for patients who have failing Fontan circulation. The objective of this study was to evaluate the miniaturized Fontan circulation assist device (mini-FCAD) during 30-day sheep studies (n = 5). A complete right heart bypass was performed and all return flow was supported by the pump. Postoperatively, unfractionated heparin was given to maintain thromboelastography R times of 2× normal. The first two studies were terminated on day 0 and day 4 due to complications. In the final three studies, the animals remained healthy and were electively terminated at 30 ± 2 days. Pump flow was between 5 and 7 lpm, left atrial pressure remained normal, and inlet pressures were between 3 and 18 mm Hg with no incidents of suction. There was no evidence of hemolysis, end organ or pulmonary dysfunction, thromboembolic events, nor thermal damage to the surrounding tissue. Explanted devices from two studies were free of thrombi and in the third study there were unattached thrombi on the SVC inlet of the rotor. The mini-FCAD was successfully tested in vivo as a right heart replacement device demonstrating adequate circulatory support and normal physiologic pulmonary and venous pressures.

Chronic Ovine Studies Demonstrate Low Thromboembolic Risk in the Penn State Infant Ventricular Assist Device.

Mechanical circulatory support for children under 6 years of age remains a challenge. This article describes the preclinical status and the results of recent animal testing with the Penn State Infant Left Ventricular Assist Device (VAD). The objectives have been to 1) demonstrate acceptably low thromboembolic risk to support Food and Drug Administration approval, 2) challenge the device by using minimal to no anticoagulation in order to identify any design or manufacturing weaknesses, and 3) improve our understanding of device thrombogenicity in the ovine animal model, using multicomponent measurements of the coagulation system and renal ischemia quantification, in order to better correlate animal results with human results.The Infant VAD was implanted as a left VAD (LVAD) in 18-29 kg lambs. Twelve LVAD and five surgical sham animals were electively terminated after approximately 30 or 60 days. Anticoagulation was by unfractionated heparin targeting thromboelastography R times of 2x normal (n = 6) or 1x normal (n = 6) resulting in negligible heparin activity as measured by anti-Xa assay (<0.1 IU/ml). Platelet inhibitors were not used.There were no clinically evident strokes or evidence of end organ dysfunction in any of the 12 electively terminated LVAD studies. The degree of renal ischemic lesions in device animals was not significantly different than that found in five surgical sham studies, demonstrating minimal device thromboembolism.In summary, these results in a challenging animal test protocol support the conclusion that the Penn State Infant VAD has a low thromboembolic risk and may allow lower levels of anticoagulation.

Performance characterization of a rotary centrifugal left ventricular assist device with magnetic suspension.

The MiTiHeart (MiTiHeart Corporation, Gaithersburg, MD, USA) left ventricular assist device (LVAD), a third-generation blood pump, is being developed for destination therapy for adult heart failure patients of small to medium frame that are not being served by present pulsatile devices. The pump design is based on a novel, patented, hybrid passive/active magnetic bearing system with backup hydrodynamic thrust bearing and exhibits low power loss, low vibration, and low hemolysis. Performance of the titanium alloy prototype was evaluated in a series of in vitro tests with blood analogue to map out the performance envelop of the pump. The LVAD prototype was implanted in a calf animal model, and the in vivo pump performance was evaluated. The animal's native heart imparted a strong pulsatility to the flow rate. These tests confirmed the efficacy of the MiTiHeart LVAD design and confirmed that the pulsatility does not adversely affect the pump performance.

Energy equivalent pressure and total hemodynamic energy associated with the pressure-flow waveforms of a pediatric pulsatile ventricular assist device.

A pulsatile pediatric ventricular assist device (VAD) with a dynamic stroke volume of approximately 12 ml was tested to quantify the effect of flowrate and systolic duration on pulsatility as quantified by the energy equivalent pressure (EEP), defined as the hemodynamic energy per unit volume of fluid pumped. The VAD was tested on a mock circulatory loop, adjusted to maintain a systemic arterial pressure of approximately 90/60 mm Hg (systolic/diastolic) and a mean of 75 mm Hg. The EEP was calculated for each beat for 1 minute at both the proximal end of the pump outlet cannula and at the distal end (arterial EEP). Nominal mean flowrates were 0.50, 0.75, 1.00, and 1.25 l/min. Systolic duration was set at either 230 or 400 milliseconds. With a rapid systolic ejection (230 milliseconds), the arterial EEP ranged from 5.58% to 8.41% relative to the mean arterial pressure. The highest EEP occurred at the lowest flowrate. With a slower (400 milliseconds) systolic ejection, the arterial EEP ranged from 2.33% to 4.20%. Hemodynamic energy loss in the outlet cannula was also quantified by the differential EEP and shown to increase markedly as systolic duration was decreased, but was relatively insensitive to mean flowrate.

Effect of the diastolic and systolic duration on valve cavitation in a pediatric pulsatile ventricular assist device.

Minimization of cavitation is of high importance in the design of pulsatile ventricular assist devices because cavitation can cause blood and valve surface damage. Cavitation is associated with valve closure and has been previously correlated to high dP/dt, high valve closing velocity, and decreased pump filling. In this study, the effects of diastolic and systolic duration on the inlet and outlet valve cavitation were investigated. A low volume (280 ml) mock circulatory loop filled with room-temperature saline was used. A high-fidelity hydrophone was mounted into the inlet valve connector approximately 0.5 cm upstream from the inlet valve to quantify inlet valve cavitation. The inlet valve connector and hydrophone were placed symmetrically on the outlet side when measuring outlet valve cavitation. The RMS intensity of a 6-millisecond window pressure trace, bandpass filtered from 50 to 500 kHz, was used to quantify cavitation intensity. Approximately 80 beats were recorded at every test condition. High-speed video and an accelerometer were used to determine the position of the valves during closure. The cavitation intensity of the inlet valve was minimal when the onset of systole occurred at the moment when the pump just completed filling (RMS was approximately zero). The cavitation intensity increased when the onset of systole occurred before the pump was completely filled (valve partially opened), reaching a plateau of approximately 16 mm Hg when the valve was fully open. The cavitation intensity increased again when diastolic duration exceeded pump filling time by more than 30 milliseconds. The outlet valve cavitation intensity was very low (<4 mm Hg) regardless of the systolic duration, which can be attributed to the position of the hydrophone being on the opposite side of cavitation events. Although very small, the outlet cavitation intensities with respect to systolic duration show a trend similar to the inlet valve cavitation with respect to diastolic duration. Both inlet and outlet valve cavitation increased with increased peak regurgitant flow. An understanding of the relationship of the inlet and outlet valve cavitation to the diastolic and systolic duration can be used to determine the optimal operating conditions of the pulsatile pediatric pump.

Precise quantification of pressure flow waveforms of a pulsatile ventricular assist device.

Unreliable quantification of flow pulsatility has hampered many efforts to assess the importance of pulsatile perfusion. Generation of pulsatile flow depends upon an energy gradient. It is necessary to quantify pressure flow waveforms in terms of hemodynamic energy levels to make a valid comparison between perfusion modes during chronic support. The objective of this study was to quantify pressure flow waveforms in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) levels in an adult mock loop using a pulsatile ventricle assist system (VAD). A 70 cc Pierce-Donachy pneumatic pulsatile VAD was used with a Penn State adult mock loop. The pump flow rate was kept constant at 5 L/min with pump rates of 70 and 80 bpm and mean aortic pressures (MAP) of 80, 90, and 100 mm Hg, respectively. Pump flows were adjusted by varying the systolic pressure, systolic duration, and the diastolic vacuum of the pneumatic drive unit. The aortic pressure was adjusted by varying the systemic resistance of the mock loop EEP (mm Hg) = (integral of fpdf)/(integral of fdt) SHE (ergs/cm3) = 1,332 [((integral of fpdt)/(integral of fdt))--MAP] were calculated at each experimental stage. The difference between the EEP and the MAP is the extra energy generated by this device. This difference is approximately 10% in a normal human heart. The EEP levels were 88.3 +/- 0.9 mm Hg, 98.1 +/- 1.3 mm Hg, and 107.4 +/- 1.0 mm Hg with a pump rate of 70 bpm and an aortic pressure of 80 mm Hg, 90 mm Hg, and 100 mm Hg, respectively. Surplus hemodynamic energy in terms of ergs/cm3 was 11,039 +/- 1,236 ergs/cm3, 10,839 +/- 1,659 ergs/cm3, and 9,857 +/- 1,289 ergs/cm3, respectively. The percentage change from the mean aortic pressure to EEP was 10.4 +/- 1.2%, 9.0 +/- 1.4%, and 7.4 +/- 1.0% at the same experimental stages. Similar results were obtained when the pump rate was changed from 70 bpm to 80 bpm. The EEP and SHE formulas are adequate to quantify different levels of pulsatility for direct and meaningful comparisons. This particular pulsatile VAD system produces near physiologic hemodynamic energy levels at each experimental stage.

Chronic in vivo testing of the Penn State infant ventricular assist device.

The Penn State Infant Ventricular Assist Device (VAD) is a 12-14 ml stroke volume pneumatically actuated pump, with custom Björk-Shiley monostrut valves, developed under the National Heart, Lung, and Blood Institute Pediatric Circulatory Support program. In this report, we describe the seven most recent chronic animal studies of the Infant VAD in the juvenile ovine model, with a mean body weight of 23.5 ± 4.1 kg. The goal of 4-6 weeks survival was achieved in five of seven studies, with support duration ranging from 5 to 41 days; mean 26.1 days. Anticoagulation was accomplished using unfractionated heparin, and study animals were divided into two protocol groups: the first based on a target activated partial thromboplastin time of 1.5-2 times normal, and a second group using a target thromboelastography R-time of two times normal. The second group required significantly less heparin, which was verified by barely detectable heparin activity (anti-Xa). In both groups, there was no evidence of thromboembolism except in one animal with a chronic infection and fever. Device thrombi were minimal and were further reduced by introduction of the custom valve. These results are consistent with results of adult VAD testing in animals and are encouraging given the extremely low levels of anticoagulation in the second group.

A passively suspended Tesla pump left ventricular assist device.

The design and initial test results of a new passively suspended Tesla type left ventricular assist device blood pump are described. Computational fluid dynamics (CFD) analysis was used in the design of the pump. Overall size of the prototype device is 50 mm in diameter and 75 mm in length. The pump rotor has a density lower than that of blood and when spinning inside the stator in blood it creates a buoyant centering force that suspends the rotor in the radial direction. The axial magnetic force between the rotor and stator restrain the rotor in the axial direction. The pump is capable of pumping up to 10 L/min at a 70 mm Hg head rise at 8,000 revolutions per minute (RPM). The pump has demonstrated a normalized index of hemolysis level below 0.02 mg/dL for flows between 2 and 9.7 L/min. An inlet pressure sensor has also been incorporated into the inlet cannula wall and will be used for control purposes. One initial in vivo study showed an encouraging result. Further CFD modeling refinements are planned and endurance testing of the device.

Mechanical heart valve performance in a pulsatile pediatric ventricular assist device.

A pulsatile pediatric ventricular assist device with a dynamic stroke volume of 12 ml is currently under development at the Pennsylvania State University. A monoleaflet valve (Björk-Shiley Monostrut) and a bileaflet valve (CPHV, CarboMedics Prosthetic Heart Valve) were examined in this study. A high-speed video and data acquisition system was used to simultaneously record video images, pressure waveforms, and flow waveforms for an array of in vitro test conditions that varied heart rate and systolic duration. The CPHV in both the horizontal and vertical orientations have larger regurgitant volumes than the Monostrut valves at all operating conditions in both the inlet and outlet positions. However, the CPHV has higher stroke volumes and cardiac outputs than the Monostrut valve at higher heart rates and longer systolic durations. In addition, the hydrodynamic performance of the Monostrut valve is more sensitive to changes in operating conditions for the pulsatile pediatric ventricular assist device than the CPHV in both orientations. Additional testing is under way to identify the optimal operating conditions for each type of valve.

Comparison of four different pediatric 10F aortic cannulae during pulsatile versus nonpulsatile perfusion in a simulated neonatal model of cardiopulmonary bypass.

We compared four commercially available 10F pediatric aortic cannulae with different geometric designs (DLP-Long tip, DLP-Short tip, RMI-Long tip, and Surgimedics-Short tip) during pulsatile versus nonpulsatile perfusion in terms of pressure drops and surplus hemodynamic energy (SHE) levels in an in vitro neonatal model of cardiopulmonary bypass. The pseudo patient was subjected to seven pump flow rates at 100 ml/min increments in the 400-1,000 ml/min range. A total of 44 experiments (n = 22, nonpulsatile; n = 22, pulsatile) were performed at each of the seven flow rates. Surgimedics had significantly higher pressure drops than the other three cannulae at various flow rates during nonpulsatile and pulsatile perfusion, respectively. When the perfusion mode was changed from nonpulsatile to pulsatile flow, SHE levels at both precannula and postcannula sites increased seven to nine times at all flow rates in all four cannulae. Surgimedics generated a significant lower SHE level when compared with the other three cannulae at all flow rates at both precannula and postcannula sites. The results suggest that different geometries of aortic cannulae have a significant impact on pressure drops of the cannulae as well as hemodynamic energy generation and delivery. Pulsatile perfusion generates more "extra" hemodynamic energy when compared with the nonpulsatile perfusion mode with all four cannulae used in this study.

The effect of left ventricular function and drive pressures on the filling and ejection of a pulsatile pediatric ventricular assist device in an acute animal model.

Penn State is currently developing a 12-mL, pulsatile, pneumatically driven pediatric ventricular assist device intended to be used in infants. After extensive in vitro testing of the pump in a passive-filling, mock circulatory loop, an acute animal study was performed to obtain data with a contracting ventricle. The objectives were to determine the range of pneumatic pressures and time required to completely fill and empty the pediatric ventricular assist device under various physiologic conditions, simulate reductions in ventricular contractility and blood volume, and provide data for validation of the mock circulatory loop. A 15-kg goat was used. The cannulation was achieved via left thoracotomy from the left ventricle to the descending aorta. The pump rate and systolic duration were controlled manually to maintain complete filling and ejection. The mean ejection time ranged from 280 ms to 382 ms when the systolic pressure ranged from 350 mm Hg to 200 mm Hg. The mean filling time ranged from 352 ms to 490 ms, for the diastolic pressure range of -60 mm Hg to 0 mm Hg. Esmolol produced a decrease in left ventricular pressure, required longer pump filling time, and reduced LVAD flow.

Quantification of perfusion modes in terms of surplus hemodynamic energy levels in a simulated pediatric CPB model.

The objective of this investigation was to compare pulsatile versus nonpulsatile perfusion modes in terms of surplus hemodynamic energy (SHE) levels during cardiopulmonary bypass (CPB) in a simulated neonatal model. The extracorporeal circuit consisted of a Jostra HL-20 heart-lung machine (for both pulsatile and nonpulsatile modes of perfusion), a Capiox Baby RX hollow-fiber membrane oxygenator, a Capiox pediatric arterial filter, 5 feet of arterial tubing and 6 feet of venous tubing with a quarter-inch diameter. The circuit was primed with a lactated Ringers solution. The systemic resistance of a pseudo-patient (mean weight, 3 kg) was simulated by placing a clamp at the end of the arterial line. The pseudo-patient was subjected to five pump flow rates in the 400 to 800 ml/min range. During pulsatile perfusion, the pump rate was kept constant at 120 bpm. Pressure waveforms were recorded at the preoxygenator, postoxygenator, and preaortic cannula sites. SHE was calculated by use of the following formula {SHE (ergs/cm) = 1,332 [((integral fpdt) / (integral fdt)) - Mean Arterial Pressure]} (f = pump flow and p = pressure). A total of 60 experiments were performed (n = 6 for nonpulsatile and n = 6 for pulsatile) at each of the five flow rates. A linear mixed-effects model, which accounts for the correlation among repeated measurements, was fit to the data to assess differences in SHE between flows, pumps, and sites. The Tukey multiple comparison procedure was used to adjust p values for post hoc pairwise comparisons. With a pump flow rate of 400 ml/min, pulsatile flow generated significantly higher surplus hemodynamic energy levels at the preoxygenator site (23,421 +/- 2,068 ergs/cm vs. 4,154 +/- 331 ergs/cm, p < 0.0001), the postoxygenator site (18,784 +/- 1,557 ergs/cm vs. 3,383 +/- 317 ergs/cm, p < 0.0001), and the precannula site (6,324 +/- 772 ergs/cm vs. 1,320 +/- 91 ergs/cm, p < 0.0001), compared with the nonpulsatile group. Pulsatile flow produced higher SHE levels at all other pump flow rates. The Jostra HL-20 roller pump generated significantly higher SHE levels in the pulsatile mode when compared with the nonpulsatile mode at all five pump flow rates.

Comparison of hollow-fiber membrane oxygenators with different perfusion modes during normothermic and hypothermic CPB in a simulated neonatal model.

PURPOSE: The objectives of this investigation were (1) to compare two hollow-fiber membrane oxygenators (Capiox Baby RX versus Lilliput 1-D901) in terms of pressure drops and surplus hemodynamic energy (SHE) during normothermic and hypothermic cardiopulmonary bypass (CPB) in a simulated neonatal model; and (2) to evaluate pulsatile and non-pulsatile perfusion modes for each oxygenator in terms of SHE levels. METHODS: In a simulated patient, CPB was initiated at a constant pump flow rate of 500 mL/min. The circuit was primed with fresh bovine blood. After 5 min of normothermic CPB, the pseudo-patient was cooled down to 25 degrees C for 10 min followed by 30 min of hypothermic CPB. The pseudo-patient then underwent 10 min of rewarming and 5 min of normothermic CPB. At each experimental site (pre- and post-oxygenator and pre-aortic cannula), SHE was calculated using the following formula {SHE (ergs/cm3) = 1332 [((integralfpdt)/(integralfdt)) - mean arterial pressure]} (f = pump flow and p = pressure). A linear mixed-effects model that accounts for the correlation among repeated measurements was fit to the data to assess differences in SHE between oxygenators, pumps, and sites. Tukey's multiple comparison procedure was used to adjust p-values for post-hoc pairwise comparisons. RESULTS: The pressure drops in the Capiox group compared to the Lilliput group were significantly lower during hypothermic non-pulsatile (21.3 +/- 0.5 versus 50.7 +/- 0.9 mmHg, p < 0.001) and pulsatile (22 +/- 0.0 versus 53.3 +/- 0.5 mmHg, p < 0.001) perfusion, respectively. Surplus hemodynamic energy levels were significantly higher in the pulsatile group compared to the non-pulsatile group, with Capiox (1655 +/- 92 versus 10008 +/- 1370 ergs/cm3, p < 0.001) or Lilliput (1506 +/- 112 versus 7531 +/- 483 ergs/cm3, p < 0.001) oxygenators. During normothermic CPB, both oxygenators had patterns similar to those observed under hypothermic conditions. CONCLUSIONS: The Capiox oxygenator had a significantly lower pressure drop in both pulsatile and non-pulsatile perfusion modes. For each oxygenator, the SHE levels were significantly higher in the pulsatile mode.