Combination of extracorporeal membrane oxygenation and high-frequency oscillatory ventilation saved a child with severe ARDS after pulmonary resection

We report a case in which a 2-year-old girl who underwent a right middle and lower lung lobectomy for congenital cystic adenomatoid malformation suffered massive bleeding and developed acute respiratory distress syndrome (ARDS) during the operation. She was ventilated with a high level of F_IO₂ (0.75–1.0), PEEP (10–20 cmH₂O), and PIP (33–55 cmH₂O) to maintain SPO₂ (>90%). Following transfer to the ICU, continuous hemodialysis was introduced to reduce excessive blood volume. However, pulmonary oxygenation did not improve, and marked subcutaneous emphysema occurred on postoperative day 3 (POD 3). We introduced venovenous (V-V) extracorporeal membrane oxygenation (ECMO) to rest the lung, and V-V ECMO was changed to right and left atrial ECMO because of unsatisfactory oxygen support on POD 23. A CT scan showed almost the entire lung had collapsed, even though we had administered diuretics, steroids, nitric oxide, sivelestat, and surfactant for ARDS. We applied high-frequency oscillatory ventilation (HFOV) with a mean airway pressure of 20 cmH₂O, frequency of 9.2 Hz, and amplitude of 38 cmH₂O on POD 45. The collapsed lung was then gradually recruited, and pulmonary oxygenation improved (P/F ratio = 434). ECMO was successfully weaned on POD 88. The patient required a tracheostomy, but she was able to function without a ventilator on POD 142. Although HFOV has failed to show a mortality benefit in ARDS patients, the unique lung recruitment by HFOV can be a useful therapeutic option for severe ARDS patients in combination with sufficient lung rest produced by ECMO.     

Comparison of a New Miniaturized Extracorporeal Membrane Oxygenation System With Integrated Rotary Blood Pump to a Standard System in a Porcine Model of Acute Lung Injury

Extracorporeal membrane oxygenation (ECMO) is used for severe acute respiratory distress syndrome. However, available ECMO systems are large and not well designed for fast delivery, emergency implantation, and interhospital transfer. Therefore, a new miniaturized oxygenator with integrated rotary blood pump (ILIAS) was developed and compared with a standard ECMO system in a large animal model. Acute lung injury was induced with repeated pulmonary saline lavage in 14 pigs until PaO₂/FiO₂‐ratio was <100 mm Hg with a positive‐end‐expiratory‐pressure of 5 mbar. Pigs were assigned to the following three groups: group 1 (n = 4): control group with conventional ventilation; group 2 (n = 5): standard vv‐ECMO; group 3 (n = 5): vv‐ILIAS. Gas exchange, hemodynamics, hemolysis, and coagulation activation were examined over a period of 8 h. No device failed during the observation period. PaCO₂ decreased from 59.40 ± 4.14 mm Hg to 48.62 ± 4.50 mm Hg after 1 h in the ILIAS group compared with an improvement of PaCO2 from 48.86 ± 7.45 to 40.10 ± 6.02 in the conventional ECMO group (P = not significant [n.s.]). ARDS‐induced respiratory acidosis was controlled promptly with a pH of 7.2 ± 0.1 at baseline increasing to 7.4 ± 0.1 in both study groups after 60 min of ECMO support. Mean carbon dioxide transfer was comparable between the conventional ECMO and ILIAS (211.36 ± 78.39 mL/min vs. 219.99 ± 76.72 mL/min, P = n.s.). PaO₂/FiO₂ increased from 118.4 ± 15.5 mm Hg to 179.1 ± 72.4 mm Hg in the ILIAS group compared with an improvement of oxygenation from 107.1 ± 24.9 mm Hg to 179.0 ± 45.7 mm Hg in the standard ECMO group (P = n.s.). Mean oxygen transfer was calculated with 136.09 ± 30.25 mL/min for the ILIAS and 129.05 ± 36.28 mL/min for the standard ECMO. Hemodynamic instability or significant activation of the plasmatic coagulation was not observed. However, hemolysis was significantly higher in the ILIAS group compared with the conventional ECMO. As the ILIAS prototype provided excellent gas exchange with hemodynamic stability comparable with a standard ECMO system, we believe this study serves as a proof of concept. Further development and design modifications (optimized rotation speed and surface coating of rotor) are already done and another experiment is projected to reduce hemolysis and platelet consumption for clinical application.     

Technical Indicators to Evaluate the Degree of Large Clot Formation Inside the Membrane Fiber Bundle of an Oxygenator in an In Vitro Setup

The most common technical complication during ECMO is clot formation. A large clot inside a membrane oxygenator reduces effective membrane surface area and therefore gas transfer capabilities, and restricts blood flow through the device, resulting in an increased membrane oxygenator pressure drop (dpMO). The reasons for thrombotic events are manifold and highly patient specific. Thrombus formation inside the oxygenator during ECMO is usually unpredictable and remains an unsolved problem. Clot sizes and positions are well documented in literature for the Maquet Quadrox‐i Adult oxygenator based on CT data extracted from devices after patient treatment. Based on this data, the present study was designed to investigate the effects of large clots on purely technical parameters, for example, dpMO and gas transfer. Therefore, medical grade silicone was injected into the fiber bundle of the devices to replicate large clot positions and sizes. A total of six devices were tested in vitro with silicone clot volumes of 0, 30, 40, 50, 65, and 85 mL in accordance with ISO 7199. Gas transfer was measured by sampling blood pre and post device, as well as by sampling the exhaust gas at the devices’ outlet at blood flow rates of 0.5, 2.5, and 5.0 L/min. Pre and post device pressure was monitored to calculate the dpMO at the different blood flow rates. The dpMO was found to be a reliable parameter to indicate a large clot only in already advanced “clotting stages.” The CO₂ concentration in the exhaust gas, however, was found to be sensitive to even small clot sizes and at low blood flows. Exhaust gas CO₂ concentration can be monitored continuously and without any risks for the patient during ECMO therapy to provide additional information on the endurance of the oxygenator. This may help detect a clot formation and growth inside a membrane oxygenator during ECMO even if the increase in dpMO remains moderate.     

Akutes Lungenversagen und septische Kardiomyopathie

A 30-year-old patient was admitted to hospital with fever and respiratory insufficiency due to community acquired pneumonia. Within a few days the patient developed septic cardiomyopathy and severe acute respiratory distress syndrome (ARDS) which deteriorated under conventional mechanical ventilation. Peripheral venoarterial extracorporeal membrane oxygenation (va-ECMO) was initiated by the retrieval team of an ARDS/ECMO centre at a p_aO₂/F_IO₂ ratio of 73 mmHg and a left ventricular ejection fraction (EF) of 10?%. After 12 h va-ECMO was converted to veno-venoarterial ECMO (vva-ECMO) for improvement of pulmonary and systemic oxygenation. Left ventricular function improved (EF 45?%) 36 h after starting ECMO and the patient was weaned from vva-ECMO and converted to vv-ECMO. The patient was weaned successfully from vv-ECMO after 5 additional days and transferred back to the referring hospital for weaning from the ventilator.     

The effect of hyperoxia on inflammation and platelet responses in an ex vivo extracorporeal membrane oxygenation circuit

Use of extracorporeal membrane oxygenation (ECMO) is expanding, however, it is still associated with significant morbidity and mortality. Activation of inflammatory and innate immune responses and hemostatic alterations contribute to complications. Hyperoxia may play a role in exacerbating these responses. Nine ex vivo ECMO circuits were tested using fresh healthy human whole blood, with two oxygen levels: 21% inspired fraction of oxygen (FiO₂; mild hyperoxia; n = 5) and 100% FiO₂ (severe hyperoxia; n = 4). Serial blood samples were taken for analysis of platelet aggregometry, leukocyte activation, inflammatory, and oxidative stress markers. ECMO resulted in reduced adenosine diphosphate- (P < .05) and thrombin receptor activating peptide-induced (P < .05) platelet aggregation, as well as increasing levels of the neutrophil activation marker, neutrophil elastase (P = .013). Additionally, levels of the inflammatory chemokine interleukin-8 were elevated (P < .05) and the activity of superoxide dismutase, a marker of oxidative stress, was increased (P = .002). Hyperoxia did not augment these responses, with no significant differences detected between mild and severe hyperoxia. Our ex vivo model of ECMO revealed that the circuit itself triggers a pro-inflammatory and oxidative stress response, however, exposure to supra-physiologic oxygen does not amplify that response. Extended-duration studies and inclusion of an endothelial component could be beneficial in characterizing longer term changes.     

Non‐invasive Measurements of Energy Expenditure and Respiratory Quotient by Respiratory Mass Spectrometry in Children on Extracorporeal Membrane Oxygenation‐A Pilot Study

Extracorporeal membrane oxygenation (ECMO) provides temporary life‐saving support for pediatric patients with severe cardiac failure, but causes metabolic disturbances and altered nutritional requirements. However, few studies have addressed the optimal energy supply to meet the demand of these children, largely due to technical difficulties with their invasive nature. We have adapted respiratory mass spectrometry to continuously measure O₂ consumption and CO₂ production in the gas exchange across the ECMO oxygenator, as well as that across the ventilator. This study aimed to assess energy expenditure (EE) and respiratory quotient (RQ) in children on ECMO. Five children (aged 0.3 to 36 months, median 20) were studied between Day 1 and Day 6 on ECMO. EE and RQ were measured in sequential fashion at the child's native lungs and ECMO oxygenator using respiratory mass spectrometry. Measurements were collected at 4‐h intervals, with the means in 24 h representing the values of each day. Each child's caloric and protein intakes were recorded for each day. Between ECMO Days 1 and 6, there was a small but significant increase in EE from 40 to 46 kcal/kg/day (P = 0.03). In comparison, the caloric intake significantly increased by twice as much as EE from 30 to 61 kcal/kg/day (P = 0.017). As a result, RQ significantly increased from 0.6 to 1.0 (P < 0.0001). Protein intake significantly increased during ECMO Days 1 to 6 from 0.5 to 1.5 g/kg/day (P = 0.04). Respiratory mass spectrometry is feasible to provide a unique and safe technique to measure EE and RQ in patients on ECMO. Without this knowledge, inadequate feeding may occur. Further studies are warranted in a larger patient population to provide better information to guide clinical practice in this special group of critically ill children.     

New Generation Extracorporeal Membrane Oxygenation With MedTech Mag‐Lev,a Single‐Use,Magnetically Levitated,Centrifugal Blood Pump: Preclinical Evaluation in Calves

We have evaluated the feasibility of a newly developed single‐use, magnetically levitated centrifugal blood pump, MedTech Mag‐Lev, in a 3‐week extracorporeal membrane oxygenation (ECMO) study in calves against a Medtronic Bio‐Pump BPX‐80. A heparin‐ and silicone‐coated polypropylene membrane oxygenator MERA NHP Excelung NSH‐R was employed as an oxygenator. Six healthy male Holstein calves with body weights of about 100 kg were divided into two groups, four in the MedTech group and two in the Bio‐Pump group. Under general anesthesia, the blood pump and oxygenator were inserted extracorporeally between the main pulmonary artery and the descending aorta via a fifth left thoracotomy. Postoperatively, both the pump and oxygen flow rates were controlled at 3 L/min. Heparin was continuously infused to maintain the activated clotting time at 200–240 s. All the MedTech ECMO calves completed the study duration. However, the Bio‐Pump ECMO calves were terminated on postoperative days 7 and 10 because of severe hemolysis and thrombus formation. At the start of the MedTech ECMO, the pressure drop across the oxygenator was about 25 mm Hg with the pump operated at 2800 rpm and delivering 3 L/min flow. The PO₂ of the oxygenator outlet was higher than 400 mm Hg with the PCO₂ below 45 mm Hg. Hemolysis and thrombus were not seen in the MedTech ECMO circuits (plasma‐free hemoglobin [PFH] < 5 mg/dL), while severe hemolysis (PFH > 20 mg/dL) and large thrombus were observed in the Bio‐Pump ECMO circuits. Plasma leakage from the oxygenator did not occur in any ECMO circuits. Three‐week cardiopulmonary support was performed successfully with the MedTech ECMO without circuit exchanges. The MedTech Mag‐Lev could help extend the durability of ECMO circuits by the improved biocompatible performances.     

A pumpless artificial lung without systemic anticoagulation: The Nitric Oxide Surface Anticoagulation system

BackgroundArtificial lungs have the potential to serve as a bridge to transplantation or recovery for children with end-stage lung disease dependent on extracorporeal life support, but such devices currently require systemic anticoagulation. We describe our experience using the novel Nitric Oxide (NO) Surface Anticoagulation (NOSA) system—an NO-releasing circuit with NO in the sweep gas—with the Pediatric MLung—a low-resistance, pumpless artificial lung.MethodsNO flux testing: MLungs (n = 4) were tested using veno-venous extracorporeal life support in a sheep under anesthesia with blood flow set to 0.5 and 1 L/min and sweep gas blended with 100 ppm NO at 1, 2, and 4 L/min. NO and NO₂ were measured in the sweep and exhaust gas to calculate NO flux across the MLung membrane. Pumpless implants: Sheep (20–100 kg, n = 3) underwent thoracotomy and cannulation via the pulmonary artery (device inflow) and left atrium (device outflow) using cannulae and circuit components coated with an NO donor (diazeniumdiolated dibutylhexanediamine; DBHD-N₂O₂) and argatroban. Animals were connected to the MLung with 100 ppm NO in the sweep gas under anesthesia for 24 h with no systemic anticoagulation after cannulation.ResultsNO flux testing: NO flux averaged 3.4 ± 1.0 flux units (x10^?10 mol/cm²/min) (human vascular endothelium: 0.5–4 flux units). Pumpless implants: 3 sheep survived 24 h with patent circuits. MLung blood flow was 716 ± 227 mL/min. Outlet oxygen saturation was 98.3 ± 2.6%. Activated clotting time was 151±24 s. Platelet count declined from 334,333 ± 112,225 to 123,667 ± 7,637 over 24 h. Plasma free hemoglobin and leukocyte and platelet activation did not significantly change.ConclusionsThe NOSA system provides NO flux across a gas-exchange membrane of a pumpless artificial lung at a similar rate as native vascular endothelium and achieves effective local anticoagulation of an artificial lung circuit for 24 h.     

Lung-protective ventilation during Trendelenburg pneumoperitoneum surgery: A randomized clinical trial

Study objectiveTo assess the effects of a protective ventilation strategy during Trendelenburg pneumoperitoneum surgery on postoperative oxygenation.DesignsParallel-group, randomized trial.SettingOperating room of a university hospital, Italy.PatientsMorbidly obese patients undergoing Trendelenburg pneumoperitoneum gynaecological surgery.InterventionsParticipants were randomized to standard (SV: tidal volume = 10 ml/kg of predicted body weight, PEEP = 5 cmH₂O) or protective (PV: tidal volume = 6 ml/kg of predicted body weight, PEEP = 10 cmH₂O, recruitment maneuvers) ventilation during anesthesia.MeasurementsPrimary outcome was PaO₂/FiO₂ one hour after extubation. Secondary outcomes included day-1 PaO₂/FiO₂, day-2 respiratory function and intraoperative respiratory/lung mechanics, assessed through esophageal manometry, end-expiratory lung volume (EELV) measurement and pressure-volume curves.Main resultsSixty patients were analyzed (31 in SV group, 29 in PV group). Median [IqR] tidal volume was 350 ml [300–360] in PV group and 525 [500–575] in SV group. Median PaO₂/FiO₂ one hour after extubation was 280 mmHg [246–364] in PV group vs. 298 [250–343] in SV group (p = 0.64). Day-1 PaO₂/FiO_2, day-2 forced vital capacity, FEV-1 and Tiffenau Index were not different between groups (all p > 0.10). Intraoperatively, 59% of patients showed complete airway closure during pneumoperitoneum, without difference between groups: median airway opening pressure was 17 cmH₂O. In PV group, airway and transpulmonary driving pressure were lower (12 ± 5 cmH₂O vs. 17 ± 7, p < 0.001; 9 ± 4 vs. 13 ± 7, p < 0.001), PaCO₂ and respiratory rate were higher (48 ± 8 mmHg vs. 42 ± 12, p < 0.001; 23 ± 5 breaths/min vs. 16 ± 4, p < 0.001). Intraoperative EELV was similar between PV and SV group (1193 ± 258 ml vs. 1207 ± 368, p = 0.80); ratio of tidal volume to EELV was lower in PV group (0.45 ± 0.12 vs. 0.32 ± 0.09, p < 0.001).ConclusionsIn obese patients undergoing Trendelenburg pneumoperitoneum surgery, PV did not improve postoperative oxygenation nor day-2 respiratory function. PV was associated with intraoperative respiratory mechanics indicating less injurious ventilation. The high prevalence of complete airway closure may have affected study results.Trial registrationProspectively registered on http://clinicaltrials.gov NCT03157479 on May 17th, 2017.     

Experimental evaluation of the Travenol and Landé-Edwards membrane oxygenators for use in neonate perfusions

A compact, low-prime cardiopulmonary bypass circuit which employs a membrane oxygenator has recently been developed for use in neonatal perfusions. In order to assess the comparative performance of the Travenol and Landé-Edwards membrane oxygenators when used in this circuit, two groups of 6 puppies each weighing between 4 and 6 kg. underwent one hour of total bypass with each unit using a 50% blood–50% Normosol prime. The Landé-Edwards oxygenator required a thorough rinsing prior to use in order to perform effectively, while the Travenol membrane oxygenator could be used as packaged. Five of the 6 puppies in each group were long-term survivors. Adequate oxygenation, CO₂ exchange (pO₂ > 200 mm. Hg, pCO₂ < 40 mm. Hg), and tissue perfusion (mixed venous pO₂ > 25 mm. Hg) together with low hemolysis (plasma hemoglobin < 40 mg. per 100 ml.) were demonstrated in both groups. Serum electrolytes remained normal. Thus these results verified that total bypass using either type of membrane oxygenator was feasible, with satisfactory hemodynamic performance, adequate gas exchange, and long-term survival regardless of which membrane was selected. However, the relative ease of use (no rinse) and stability of the Travenol unit at low perfusion pressure (internal baffling prevents membrane collapse) suggest that it is the unit of choice for use in small infants.     

Extracorporeal membrane oxygenation for 2009 influenza A(H1N1) severe respiratory failure in Japan

Purpose

To evaluate procedures and outcomes of extracorporeal membrane oxygenation (ECMO) therapy applied to 2009 influenza A(H1N1) severe respiratory failure patients in Japan.

Methods

This observational study used database information about adults who received ECMO therapy for H1N1-related severe respiratory failure from April 1, 2010 to March 31, 2011.

Results

Fourteen patients from 12 facilities were enrolled. Anti-influenza drugs were used in all cases. Before the start of ECMO, the lowest PaO₂/FiO₂ was median (interquartile) of 50 (40–55) mmHg, the highest peak inspiratory pressure was 30 (29–35) cmH₂O, and mechanical ventilation had been applied for at least 7?days in 5 patients. None of the facilities had extensive experience with ECMO for respiratory failure (6 facilities, no previous experience; 5 facilities, one or two cases annually). The blood drainage cannula was smaller than 20?Fr. in 10 patients (71.4?%). The duration of ECMO was 8.5 (4.0–10.8) days. The duration of each circuit was only 4.0 (3.2–5.3) days, and the ECMO circuit had to be renewed 19 times (10 cases). Thirteen patients (92.9?%) developed adverse events associated with ECMO, such as oxygenator failure, massive bleeding, and disseminated intravascular coagulation. The survival rate was 35.7?% (5 patients).

Conclusion

ECMO therapy for H1N1-related severe respiratory failure in Japan has very poor outcomes, and most patients developed adverse events. However, this result does not refute the effectiveness of ECMO. One possible cause of these poor outcomes is the lack of satisfactory equipment, therapeutic guidelines, and systems for patient transfer to central facilities.     

The absorbing filter Oxiris in severe coronavirus disease 2019 patients: A case series

Hypercytokines cause acute respiratory distress syndrome (ARDS) in coronavirus disease 2019 (COVID-19) patients, which is the main reason for intensive care unit treatment and the leading cause of death in COVID-19 patients. Cytokine storm is a critical factor in the development of ARDS. This study evaluated the efficacy and safety of Oxiris filter in the treatment of COVID-19 patients. Five patients with COVID-19 who received continuous renal replacement therapy (CRRT) in Henan provincial people's hospital between January 23, 2019 and March 28, 2020, were enrolled in this study. Heart rate (HR), mean arterial pressure (MAP), oxygenation index (PaO₂/FiO₂), renal function, C-reactive protein (CRP), cytokines, procalcitonin (PCT), acute physiology and chronic health evaluation II (APACHE II), sequential organ failure score (SOFA), and prognosis were compared after CRRT. Five COVID-19 patients, three males and two females, aged 70.2 ± 19.6 years, were enrolled. After treatment, HR (101.4 ± 14.08 vs. 83.8 ± 6.22 bpm/min), CRP (183 ± 25.21 vs. 93.78 ± 70.81 mg/L), IL-6 (3234.49 (713.51, 16038.36) vs. 181.29 (82.24, 521.39) pg/mL), IL-8 (154.86 (63.97, 1476.1) vs. 67.19 (27.84, 85.57) pg/mL), and IL-10 (17.43 (9.14, 41.22) vs. 4.97 (2.39, 8.70) pg/mL), APACHE II (29 ± 4.92 vs. 18.4 ± 2.07), and SOFA (17.2 ± 1.92 vs. 11.2 ± 3.4) significantly decreased (P < .05), while MAP (75.8 ± 4.92 vs. 85.8 ± 6.18 mm Hg), and PaO₂/FiO₂ (101.2 ± 7.49 vs. 132.6 ± 26.15 mm Hg) significantly increased (P < .05). Among the five patients, negative conversion of nucleic acid test was found in three cases, while two cases died. No adverse events occurred during the treatment. Our study observed a reduced level of overexpressed cytokines, stabilization of hemodynamic status, and staged improvement of organ function during the treatment with Oxiris filter.     

Rapid Placement of Bicaval Dual-Lumen Catheter in a Swine Model of Venovenous ECMO

ABSTRACT

Background: Venovenous (VV) extracorporeal membrane oxygenation (ECMO) applied through a single site with a bicaval dual-lumen (BCDL) catheter is a growing method of treatment of acute respiratory failure, thus animal models for research purposes are needed. We describe a rapid technique for the placement of the BCDL catheter for single-site VV ECMO in swine. Design: Prior to the application of single-site VV ECMO model with common crossbred piglets, BCDL catheters were placed using anatomical landmarks. Transthoracic echocardiography (TTE) with color Doppler was used to determine catheter placement. Final determination of catheter placement was confirmed by necropsy. Arterial blood gas and hemodynamic parameters were recorded at baseline and then hourly. The values are mean ± SD. Results: Using anatomical landmarks by positioning the BCDL catheter tip approximately 6.5 cm distal to the tip of the manubrium, cannulation was easily accomplished in five piglets with no positional adjustments of the catheter required. Cannula placement was confirmed with both TTE color Doppler and necropsy. Respiratory support was achieved with baseline and hourly measurements of pH 7.45 ± 0.03, 7.44 ± 0.07, 7.46 ± 0.05, 7.47 ± 0.06 (p = NS); PO₂ 86 ± 30 mmHg, 98 ± 30 mmHg, 94 ± 40 mmHg, and 79 ± 30 mmHg (p = NS); and PCO₂ 43 ± 3 mmHg, 44 ± 8 mmHg, 38 ± 5 mmHg, and 40 ± 4 mmHg (p = NS). Conclusions: Using anatomical landmarks for the placement of the BCDL catheter was rapid and effective in a swine model of VV ECMO, resulting in improved time efficiency for research.     

Establishment of a novel miniature veno‐venous extracorporeal membrane oxygenation model in the rat

Recently, veno‐venous extracorporeal membrane oxygenation (V‐V ECMO) has been commonly used in the world to support patients with severe respiratory failure. However, V‐V ECMO is a new technology compared to veno‐arterial extracorporeal membrane oxygenation and cardiopulmonary bypass, and there are few reports of basic research. Although continuing research is desired, clinical research that standardizes conditions such as patients’ background characteristics is difficult. The purpose of this study was to establish a simple and stably maintainable miniature V‐V ECMO model to study the mechanisms of the biological reactions in circulation during V‐V ECMO. The V‐V ECMO system consisted of an original miniature membrane oxygenator, polyvinyl chloride tubing line, and roller pump. The priming volume of this system was only 8 mL. Polyethylene tubing was used to cannulate the right femoral vein as the venous return cannula for the V‐V ECMO system. A 16‐G cannula was passed through the right internal jugular vein and advanced into the right atrium as the conduit for venous uptake. The animals were divided into 2 groups: SHAM group and V‐V ECMO group. V‐V ECMO was initiated and maintained at 50‐60 mL/kg/min, and oxygen was added into the oxygenator during V‐V ECMO at a concentration of 100% (pump flow:oxygen = 1:10). Blood pressure was measured continuously, and blood cells were measured by blood collection. During V‐V ECMO, the blood pressure and hemodilution rate were maintained around 80 mm Hg and 20%, respectively. Hb was kept at >10 g/dL, and V‐V ECMO could be maintained without blood transfusion. It was possible to confirm oxygenation of and carbon dioxide removal from the blood. Likewise, the pH was adequately maintained. There were no problems with this miniature V‐V ECMO system, and extracorporeal circulation progressed safely. In this study, a novel miniature V‐V ECMO model was established in the rat. A miniature V‐V ECMO model appears to be very useful for studying the mechanisms of the biological reactions during V‐V ECMO and to perform basic studies of circulation assist devices.     

Boussignac CPAP in the Postoperative Period in Morbidly Obese Patients

Background In the postoperative period hypoventilation and hypoxia with hypercarbia may occur in morbidly obese patients due to the residual influence of general anesthesia drugs, postoperative atelectasis and postoperative pain. Non-Invasive Ventilation (NIV) is a method of improvement of respiratory efficiency in patients not requiring mechanical ventilation. The aim of the study was to compare NIV (Boussignac) CPAP and traditional oxygen delivery via nasal catheter in the postoperative acute care unit (PACU) in morbidly obese patients after open Roux-en-Y gastric bypass (RYGBP). Methods 19 morbidly obese patients scheduled for elective open RYGBP, were randomly divided into 2 groups: CPAP (10 patients) or control (nasal catheter – 9 patients). Patients consisted of: 8 male and 11 female, mean weight 127.76 ± 18.5 kg, height 173.41 ± 9.41 cm, BMI 42.43 ± 3.3 kg/m2, age 35.84 ± 9.05 years. In the PACU, capillary blood gas measurements were taken at 3 Time Points: T1 – 30 min, T2 – 4 hours and T3 – 8 hours after admission. Sample T0 was taken before surgery. For management of postoperative pain, patients received morphine 2 mg/h intravenously and tramadol 100 mg. Results Mean blood gas measurements of all postoperative time points were: pO₂ 81.0 ± 16.0 (range 78.1–85.7) mmHg vs 65.9 ± 4.9 (range 63.8–68.1) mmHg (P < 0.05); pCO₂ 40.6 ± 2.4 (range 39.4–41.8) mmHg vs 41.5 ± 4.0 (range 39.6–43.4) mmHg (P > 0.05), in the CPAP and control groups respectively. In every case, pulse-oxymetry oxygenation was >94%. Conclusion Boussignac CPAP improved blood oxygenation compared to passive oxygenation with a nasal catheter but had no influence on CO₂ elimination in non-CO₂ retaining morbidly obese patients.     

Evaluation of centrifugal blood pumps in term of hemodynamic performance using simulated neonatal and pediatric ECMO circuits

The objective of this translational study was to evaluate the FDA-approved PediMag, CentriMag, and RotaFlow centrifugal blood pumps in terms of hemodynamic performance using simulated neonatal and pediatric extracorporeal membrane oxygenation (ECMO) circuits with different sizes of arterial and venous cannulae. Cost of disposable pump heads was another important variable for this particular study. The experimental circuit was composed of one of the centrifugal pump heads, a polymethylpentene membrane oxygenator, neonatal and pediatric arterial/venous cannulae, and 1/4-inch ID tubing. Circuits were primed with lactated Ringer’s solution and packed human red blood cells (hematocrit 35%). Trials were conducted at 36°C using the three pump heads and different cannulae (arterial/venous cannulae: 8 Fr/18 Fr, 10 Fr/20 Fr, and 12 Fr/22 Fr) at various flow rates (200–2400 mL/min, 200 mL/min increments) and rotational speeds. Pseudo patient pressure was 60 mm Hg. Real-time pressure and flow data were recorded for analysis. The RotaFlow pump had a higher pressure head and flow range compared with the PediMag and CentriMag pumps at the same rotational speed and identical experimental settings (P < 0.001). The PediMag pump had lower flow output than others (P < 0.001). Small-caliber arterial cannulae and higher flow rates predictably created higher circuit pressures and pressure drops. There was no significant difference in hemodynamic energy delivered to the pseudo patient with each of the three pumps. The arterial cannula had the highest pressure drop and hemodynamic energy loss in the circuit when compared to the oxygenator and arterial tubing. The RotaFlow centrifugal pump had a significantly better hemodynamic performance when compared to the PediMag and CentriMag blood pumps at identical experimental conditions in simulated neonatal and pediatric ECMO settings. In addition, the cost of the RotaFlow pump head ($400) is 20 to 30-fold less than the other centrifugal pumps [CentriMag ($12 000) or PediMag ($8000)] that were evaluated in this translational study.     

Silicon Micropore‐Based Parallel Plate Membrane Oxygenator

Extracorporeal membrane oxygenation (ECMO) is a life support system that circulates the blood through an oxygenating system to temporarily (days to months) support heart or lung function during cardiopulmonary failure until organ recovery or replacement. Currently, the need for high levels of systemic anticoagulation and the risk for bleeding are main drawbacks of ECMO that can be addressed with a redesigned ECMO system. Our lab has developed an approach using microelectromechanical systems (MEMS) fabrication techniques to create novel gas exchange membranes consisting of a rigid silicon micropore membrane (SμM) support structure bonded to a thin film of gas‐permeable polydimethylsiloxane (PDMS). This study details the fabrication process to create silicon membranes with highly uniform micropores that have a high level of pattern fidelity. The oxygen transport across these membranes was tested in a simple water‐based bench‐top set‐up as well in a porcine in vivo model. It was determined that the mass transfer coefficient for the system using SµM‐PDMS membranes was 3.03 ± 0.42 mL O₂ min^?1 m^?2 cm Hg^?1 with pure water and 1.71 ± 1.03 mL O₂ min^?1 m^?2 cm Hg^?1 with blood. An analytic model to predict gas transport was developed using data from the bench‐top experiments and validated with in vivo testing. This was a proof of concept study showing adequate oxygen transport across a parallel plate SµM‐PDMS membrane when used as a membrane oxygenator. This work establishes the tools and the equipoise to develop future generations of silicon micropore membrane oxygenators.     

Extracorporeal membrane oxygenation for respiratory failure: Comparison of venovenous versus venoarterial bypass

Purpose  

This study compared the respiratory status before and during extracorporeal membrane oxygenation (ECMO) in patients receiving venovenous (VV) and venoarterial (VA) ECMO to evaluate the choice of ECMO in patients with respiratory failure.     

Helium Pneumoperitoneum Ameliorates Hypercarbia and Acidosis Associated with Carbon Dioxide Insufflation during Laparoscopic Gastric Bypass in Pigs

Background: In the morbidly obese patient undergoing laparoscopic gastric bypass (LGBP), insufflation with carbon dioxide to 20 mmHg for prolonged periods may induce significant hypercarbia and acidosis with attendant sequelae. We hypothesize that the use of helium as an insufflating agent results in less hypercarbia and acidosis. Methods: The study was performed between May and November 2002. A Paratrend 7 fiberoptic probe was placed via a carotid artery catheter in 5 adult Yorkshire swine as continuous pH and pCO₂ levels were measured. Animals were ventilated to a constant pCO₂, after which LGBP was performed. Blood gas values were measured during the procedure and for 1 hour after release of pneumoperitoneum. Helium was used for insufflation in 3 of the pigs and CO₂ in 2. Comparison of arterial pH and pCO₂ were made between groups. Results: Mean maximum pCO₂ for the control group (CO₂ insufflation) was 99.75 ± 22.98 mmHg, while for the experimental group (helium insufflation) was 52.86 ± 6.27mmHg (P=.036). Mean low pH for the groups were 7.10 ± .056 and 7.36 ± .015 (P =.004) respectively. Normalization of pCO₂ in the helium group occurred at a mean of 14.58 min (SD 13.3 min) after release of pneumoperitoneum, while in the control group levels did not normalize (mean final pCO₂= 71.5 mmHg). Conclusions: Helium pneumoperitoneum in LGBP is associated with less intraoperative hypercarbia and acidosis than is the use of CO₂. In addition, pCO₂ returns to normal more rapidly postoperatively with the use of helium insufflation. Study of helium insufflation in humans undergoing LGBP is needed to prove its benefits in the clinical setting.