Integrated Heat Exchanger Research Articles

Normothermic Rapid Volume Replacement in Vascular Catastrophes Using the Infuser 37

Twenty patients (Group 1) with a mean age of 38.5 +/- 16 years and an admission Trauma Score of 7.26 +/- 5.9, suffered 27 vascular injuries and were resuscitated with the Infuser 37 (IN-37) with an integral heat exchanger. Admission systolic BP averaged 46.47 mmHg (seven with absent vital signs). A mean of 7,030 ml of blood, 3,313 ml of colloid and 13,630 ml of crystalloid per patient was given in less than 24 hours, mostly through the IN-37. Twelve thoracotomies, nine laparotomies, and one extremity exploration were performed. Twelve patients, seven with a Trauma Score less than 3, died in less than 24 hours of exsanguination. The survival rate was 40% at 24 hours and 25% at 30 days. Six patients (Group 2) with a mean age of 70.33 +/- 8.3 years underwent operation for ruptured aortic aneurysm (5 pts), and elective aortic aneurysm (1 pt) with a 66% survival at 24 hours. Admission systolic blood pressure averaged 84 mmHg. A mean of 3,895 ml of blood, 1,900 ml of colloid and 7,733 ml of crystalloid per patient was administered in less than 24 hours, mostly through the IN-37. The IN-37 provides a safe and simple means of normothermic, rapid volume replacement in hemorrhagic shock. Its use in critically ill but potentially salvageable patients with vascular injuries and aortic aneurysm may avoid the consequences of prolonged hypoperfusion and hypothermia.

Clinical Trials of a New Low Prime Hollow Fiber Membrane Oxygenator

A new membrane oxygenator has been introduced by Travenol Laboratories with continued development carried out by Sarns Inc. The polypropylene hollow fibers are wound in a pattern perpendicular to the blood flow path and serve as the conduit for the ventilating gas. The membrane surface area is 1.8 M2. The device contains an integral stainless steel bellows heat exchanger and a temperature probe well built into the blood outlet. The oxygenator is held by a wire frame holder that can be mounted in any direction on the heart lung machine. A selection of various size collapsible PVC venous reservoir bags is available to meet individual patient needs. The venous inlet connector of the bag contains a temperature probe port and a connector for the cardiotomy drain line as well as a recirculation line that attaches to the oxygenator. Twenty consenting adult patients undergoing either CABG or valve replacement were perfused using this oxygenating system. The largest patient had a BSA of 2.3 M2 while the smallest was 1.48 M2. The mean patient size was 1.92 M2. For patients 2.0 M2 or larger, a one liter reservoir bag was employed requiring a total system prime of 2.0 liters. For the remaining patients, a 500 ml bag and 1.75 liters of prime were used. In all but one case, the prime consisted of 500 ml of HES and the balance, Lactated Ringers to which was added 500 units heparin per liter of total prime. The remaining case utilized four units of fresh frozen plasma as a substitute for the HES and for 500 ml of the Lactated Ringers. The blood gas results were very consistent and showed a very strong correlation between FiO2 setting, BSA, blood temperature and pO2. The PaCO2 was easily controlled to achieve alpha-stat by ventilating the oxygenator at the optimal ventilation rate. Results include an average PaO2 of 137 mmHg with a mean O2 transfer of 104 ml per minute and a maximum transfer of 244 ml per minute. There were no gas exchange nor acid-base problems. The heat exchanger performance was satisfactory. The mean elevation in plasma hemoglobin was 19 mg/dl. The average decrease in platelet count was 37% while the hemodilutional hematocrit decrease was 26%. These data indicate that the oxygenator's blood handling characteristics compare favorably to other membrane oxygenators.

Clinical Use of a New Membrane Oxygenator

A new oxygenator, developed by Shiley Laboratories, uses microporous polypropylene membrane material in a parallel plate design. The device has an integral heat exchanger and built-in temperature ports. The M-2000 oxygenator was used for routine cardiopulmonary bypass ( CPB) during open heart surgery on sixteen consenting adult patients. Mean age of the group was 56 years and the mean body surface area was 1.77m2. One patient had an atrial septal defect repaired, nine had coronary bypass, five had valve replacement and one, a valve replacement with coronary bypass. The average CPB time was 105 minutes. The circuit was primed with 2000 ml of balanced electrolyte solution and 500 ml of 6% hydroxyethyl starch in 0.9% saline to which 1500 units of heparin had been added. Average normothermic blood gas values were; PaO2=242 mm Hg, PaCO2=32.5 mmHg. During hypothermia the temperature corrected mean values were; PaO2=155 mm Hg and PaCO2=31 mm Hg. Hematological changes observed were hematocrit and hemoglobin concentrations decreased 33% due to dilution. Platelet counts decreased 46%. Plasma hemoglobin values increase a by 19.6 mg/dl. The M-2000 presented no problems to the investigators during this study. It exchanged gases in a satisfactory manner and is gentle in its blood handling properties.

Ventilation Technique for CPB Patients Less Than 10 Kilograms Employing a 1.6 m2 Hollow Fiber Membrane

The purpose of this study was to document the performance of a 1.6 m2 hollow fiber membrane blood oxygenator (HFMO) in a specific ventilation technique for a patient population averaging 6 kilograms and .34m2 BSA. Continuous monitoring was utilized to maintain actual Pa02 about 200 mmHg and Pv02 above 35 mmHg. HFMO expired gas pC02 was monitored to select the optimal 0 2/room air sweep rate to maintain actual PaC02 between 35 and 40 mmHg. Cardiopulmonary bypass (CPB) blood flow was initiated at 160 ml/min/kg and decreased to 100 ml/min/kg at 20°C. During warming, blood flow was increased to 175 ml/min/kg at 38°C. The hematocrit averaged 18% during cooling, low blood flow and/or exsanguination. Transfusion raised the average hematocrit to 29% at 38°C. HFMO average control parameters were: VO2 FiO2 VCO2 Sweep Ratio Temperature Cooling 97. 62 44. 35. 34°C 19. 33 4. .10 20°C Warming 65. 48 300. 1.2 20°C 170. 75 105. .63 38°C ml/min/M2 % ml/min/M2 Gas: Blood Flow The Terumo HFMO integral heat exchanger cooled these patients at an average rate of .16°C/min/kg, warming with a safe gradient yielded an average rate of .09°C/min/kg. The 1.6 m2 HFMO provides more than adequate heat, oxygen and carbon dioxide transfer for this patient population.

Clinical Evaluation of a Microporous Hollow-fiber Membrane Oxygenator with Large Gas Transfer Capability

A capillary tube membrane oxygenator composed of microporous hollow fibers has been evaluated in 400 cases of cardiac surgery. The available membrane area in this device is 5.4 M2. The priming volume of the oxygenator and an integral heat exchanger is 700 ml. The perfusions were conducted with moderate hypothermia and hemodilution. Arterial pO2 was controlled by appropriate adjustment of the FiO2. The pCO2 was controlled by changing the gas flow. The duration of perfusion was up to 476 minutes at blood flow rates of 2.0 to 6.7 L/min. Oxygen transfer was as high as 352 ml/min. The mean arterial pO2 was 281 mm Hg and the pCO2 38 mm Hg. Platelet count did not change significantly during perfusion. This device has proven to provide good gas exchange for nearly eight hours in this series. Two units developed small leaks of blood into the gas phase of the device. These leaks did not affect gas exchange. This oxygenator-heat exchanger unit has proven to be simple to prime, easy to operate, provide adequate gas exchange for all adults and safe for cardiac surgery.

Initial clinical experience with a low pressire drop membrane oxygenator for cardiopulmonary bypass in adult patients

The new Travenol oxygenator is composed of 80 parallel blood pathways. Microporous membrane separates the blood and gas compartments. The membrane surface area is 3 m 2, with a pore size of 0.01 microns. Venous blood drains directly from the patient through the oxygenator, then through an integral heat exchanger and into a reservoir, from which a single arterial pump returns the blood to the patient. The advantage of this configuration of membrane oxygenator is simplicity of setup and operation. A disadvantage that we have observed is an apparent variation in resistance to blood flow through the oxygenator during clinical perfusion. Construction changes in a later version of the oxygenator have reduced the resistance to flow through the blood pathway. This device has been used for 20 perfusions at moderate hypothermia (mean 31.8 °C) in patients up to 2.1 m 2 body surface area for up to 313 minutes. Blood flow was 2.1 to 5.6 liters/min, partial arterial oxygen pressure 100 to 394 torr, partial arterial carbon dioxide pressure 19 to 57 torr (mean 37 torr) and, arterial pH 7.29 to 7.56 (mean 7.41). Oxygen transfer was as high as 230 ml/min. This integral oxygenator-heat exchanger-reservoir is operated like a bubble oxygenator, with direct venous drainage through the device and a single pump, but it uses a membrane oxygenator for gas exchange to eliminate the detrimental effects of bubbles.

A new hollow fiber membrane oxygenator with an integral heat exchanger: a hematological evaluation in dogs.

A recently developed hollow fiber membrane oxygenator, made of microporous polypropylene (Capiox, Terumo, 1.6 m2) was tested to evaluate the hemocompatibility and the ease and safety of operation. Two types of this oxygenator were tested: one with and one without an integral heat exchanger. Each type was tested in 6 dogs during a partial bypass of 2 hours at a flow rate of 2 l/min. In addition, gas transfer measurements were carried out. The Terumo oxygenator preserved the blood cells and the platelet function very well. In addition, neither the Wu-Hoak index, a method to measure platelet aggregates, nor inspection of the oxygenator revealed platelet aggregates. Operation and debubbling procedure were easy and safe. The estimated rated blood flow for O2 was 1.5 l/min with a corresponding CO2 removal of 90 ml/min. The integral heat exchanger did not affect the results significantly. Our data show that this oxygenator is easy and safe to use. Clinical evaluation is recommended.

Early Clinical Experiences with Terumo’s New Hollow Fiber Membrane Oxygenator: Capiox II

Terumo’s Capiox II is a hollow fiber membrane oxygenator with an integrated heat exchanger. This device is available in 1.6 m2, 3.3 m2, 4.3 m2, and 5.4 m2 sizes. Our clinical experiences have been with the 3.3 m2, 4.3 m2, and 5.4 m2 sizes, in over 150 open-heart patients. The 3.3 m2 was sized to patients up to 60 kg. The 5.4 m2 was used in all patients >60 kg. Both normothermic and hypothermic (24°-30° bladder) perfusions were performed. The heat exchanger was efficient and demonstrated structural integrity. On bypass, patient vital signs, gas and blood flows, arterial and venous blood gases and blood chemistries were monitored. Arterial saturations were 100%. Venous saturations were at least 65%. No acid-base problems were encountered. Initially, 100% oxygen was used. Later a gas blender using O2 and compressed air was utilized. Our experience concludes that the Capiox II is a safe, efficient onepump membrane oxygenator with integral heat exchanger. It is easy to set up and recirculate, delivering satisfactory oxygen transfer rates with a blended gas to blood flow ratio (≤1:1).

Helical-flow CO2 laser

A CO2 laser based on a helical gas-flow design has been developed. The major features of this device are as follows: (1) an integral heat exchanger plasmatube with much lower gas flow rates than other convection-cooled lasers, (2) a multiply segmented plasmatube for high-voltage standoff, (3) coaxial beam and electric discharge with small diameter-to-length ratio resulting in high beam quality and high discharge stability, and, (4) a magnetically stabilized discharge position. Gain profile measurements show that the gain distribution highly favors low-order modes, as desired. Temperature profile measurements of the gas in the plasmatube verify the efficiency of the integral heat exchanger concept. Specific laser configurations based on this design concept, intended for industrial material-processing applications, and with output powers of 400–500 W/m, are described.

Laboratory and clinical evaluation of a membrane oxygenator with secondary flows in the blood channels.

AbstractA microporous membrane oxygenator which has transverse furrows on the membrane surface has been used in 50 clinical cardiopulmonary bypass procedures for coronary revascularization. The transverse furrows on the membrane, together with intermittent rapid pulsatile reversal of the blood flow in the blood film, produce secondary flows in the film and increase exposure of desaturated blood to the membrane. Venous drainage flows into a plastic reservoir, from which it is pumped through the oxygenator and integral heat exchanger into the aorta of the patient. Perfusions were carried out with hemodilution and moderate hypothermia. The oxygenator was ventilated with oxygen. In experimental perfusions using calves, the oxygen transfer was as high as 371 ml/min. During the clinical perfusions, arterial oxygen saturation was always 98% or higher. The mean arterial carbon dioxide tension was 41 mm Hg at a mean O2 flow of 1.4 L/min. The mean arterial pH was 7.40. The oxygenator puiser which created the secondary flows in the blood film was operated at a rate of between 90 and 255 pulses per minute. Pressure drop across the oxygenator averaged 18 mm Hg. Oxygen tension in the arterial blood could be regulated with the pulser rate, greater pulser rates being associated with larger oxygen transfer. Carbon dioxide transfer was best regulated by changes in gas flow rate. The oxygenator functioned well and was safe and reliable during these 50 perfusions.

A Single-Stage Ammonia/Water Absorption Cycle With Integrated Heat Exchange Components

Thermodynamic analysis of the single-stage ammonia/water cycle indicates the importance of close temperature approach in the counter-current heat exchanges of the cycle and of recovering useful heat from the vapor rectification process. A novel style of heat exchange equipment, constructed in a laboratory by photo-etching flow passages into stainless steel plates which are then diffusion-bonded together, is capable of both of these services. In air-conditioning applications, coefficients of performance of 0.75 to 0.85 (for sink temperatures of 50°C to 30°C) appear to be achievable.

Clinical Experience with the Shiley S-100 Disposable Blood Oxygenator

The Shiley S-100 oxygenator with an integral heat exchanger is described and data from 180 perfusions in adult patients analyzed. The oxygenator produces satisfactory pO2 and PCO2 values with a mean gas flow /blood flow ratio of0.87. The platelet counts following perfusion were reduced by only 40% of the pre-perfusion levels. The mean value of plasma free hemoglobin was 26.2 mg/100 ml/60 minutes of bypass. The performance of the heat exchanger was investigated in 44 patients. The mean cooling and rewarming times (from 36.5 to 29.6°C and from 29.6 to 37°C) were 0.9 and 2.2 minutes for each degree of temperature per m2 surface area respectively. There have been neither mechanical-hydraulic problems with this unit during perfusion nor oxygenator related morbidity or mortality in the entire series of patients.

A new bubble oxygenator (OCVC oxygenator): development and clinical application.

A new bubble oxygenator, designed for simple operation and clinical efficacy in intracardiac surgery, has been developed and clinically evaluated. This device is characterized by an oxygenating chamber with controllable blood-volume, integral heat exchanger and two-stage microfilter of gravity drainage system, an apparatus for creating and uniformly distributing oxygen bubbles, and construction materials of the device known to be minimally traumatic to the blood. Clinical experience in 132 infantile and pediatric open heart procedures has demonstrated its effectiveness as measured by embolic complications and simplicity in maintaining physiologic blood gas levels.

An oxygenator for cardiopulmonary bypass in the rat

A minature bubble oxygenator with integral heat exchange has been developed for high flow, normothermic, total cardiopulmonary bypass in rats: priming volume, 25 ml; flow rate, up to 260 ml/kg/min; survival after a 2-hr total bypass. It is thus possible to use rats for cardiothoracic surgical research and to make use of the many advantages of a standardized small-animal model, in particular for large-series work, in a field previously limited to large animals such as dogs, pigs, and calves.

A new disposable membrane oxygenator with integral heat exchange

A new disposable membrane oxygenator with integral heat exchange

Elective hypothermia during extracorporeal circulation with a new heat exchanging filming oxygenator: Indications and results

1. 1. Hypothermia has been used in conjunction with extracorporeal circulation in 172 consecutive cases. 2. 2. The last eighty-four procedures have been performed with a new disc oxygenator with an integral heat exchanger allowing for the election of more profound hypothermia. 3. 3. Mild hypothermia has the effect of lowering the postoperative morbidity following cardiopulmonary bypass, whereas, profound hypothermia with extracorporeal circulation has resulted in a decreased mortality from the surgical correction of the most complex intracardiac lesions.

A rotating disc blood oxygenator and integral heat exchanger of improved inherent efficiency

A rotating disc blood oxygenator and integral heat exchanger of improved inherent efficiency