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Biomedical subjects

O Rivera

Publications and source records attributed to O Rivera.

18 recordsLinked to original sources
PubMed2006

Validation of a noninvasive neonatal optical cerebral oximeter in veno-venous ECMO patients with a cephalad catheter.

INTRODUCTION: Cerebral Oximetry is an optical technique that allows for noninvasive and continuous monitoring of brain oxygenation by determining tissue oxygen saturation (SctO2). In conjunction with pulse oximetry, cerebral oximetry offers a promising method to estimate cerebral venous oxygen saturation (SvO2). OBJECTIVE: The aim of this study was to validate the cerebral oximetry measurements with the cerebral oxygen saturation measured from blood drawn in neonates on veno-venous ECMO with existing cephalad catheter with a prototype neonatal cerebral oximeter developed by CAS Medical Systems (Branford, CT, USA). STUDY DESIGN: After obtaining informed consent, neonates undergoing VV-ECMO with cephalad catheterization were monitored by the CAS cerebral oximeter. Cephalad blood samples were periodically obtained to validate the monitor's accuracy. RESULTS: Seventeen neonates were studied with 1718 h of cerebral oximetry data collected. Compared to the reference values, the bias+/-precision for cerebral oximetry SctO2 was 0.4+/-5.1% and derived SvO2 was 0.6+/-7.3%. CONCLUSION: We recommend the use of this noninvasive method as an alternative to blood draws for cerebral venous saturation measurements in neonates requiring extracorporeal life support.

Brain Chemistry↗
PubMed2000

A comparison of intratracheal pulmonary ventilation to conventional ventilation in a surfactant deficient animal model.

OBJECTIVE: To compare intratracheal pulmonary ventilation (ITPV) with conventional ventilation in a rabbit model of surfactant deficiency. DESIGN: A prospective randomized animal study. SETTING: The Children's National Medical Center Research Animal Facility in Washington, DC. SUBJECTS: Adult male New Zealand white rabbits (n = 20), weighing 1.4-4.2 kg. INTERVENTIONS: After anesthesia and catheter placement, rabbits were tracheotomized, paralyzed, and placed on the conventional ventilator. We determined pulmonary functions at baseline. We washed surfactant out of the lungs by using serial bronchoalveolar lavages. Pulmonary function studies were determined after completion of the bronchoalveolar lavages and were used as an indication of severity of lung injury. Animals were randomized into two groups: We placed ten animals on ITPV, using the ITPV reverse thruster catheter designed by Kolobow and a prototype ITPV ventilator designed at Children's National Medical Center; we placed ten animals on conventional ventilation using the Sechrist iv-100 ventilator. Arterial blood gases were drawn every 15 mins, and the ventilator settings were adjusted to the minimal level that would maintain arterial blood gases in the following ranges: pH 7.35-7.45, PaCO2 30-40 torr (3.995.33 kPa), PaO2 50-70 torr (6.66-9.33 kPa). Animals were ventilated with the randomized ventilation techniques for 4 hrs. MEASUREMENTS AND MAIN RESULTS: Peak inspiratory pressure, mean airway pressure, and positive end-expiratory pressure were measured at the distal end of the endotracheal tube. We recorded these variables plus respiratory rate at baseline and every 30 mins for a total of 4 hrs of ventilation. Lung compliance did not differ between groups at the postlavage study period (ITPV, 0.56+/-0.13 mL/cm H2O/kg; conventional 0.49+/-0.15 mL/cm H2O/kg). At the end of the 4 hr study period, peak inspiratory pressure (ITPV, 26.2+/-4.6 cm H2O; conventional, 32.4+/-5.04 cm H2O, p = .007) and positive end-expiratory pressure (ITPV, 3.9+/-1.96 cm H2O; conventional, 6.3+/-1.42 cm H2O, p = .005) were lower in the ITPV ventilation group. Peak inspiratory pressure was significantly lower in the ITPV group by 2 hrs into the study. CONCLUSION: In this model of surfactant deficiency lung injury, ventilation and oxygenation were achieved at significantly lower ventilator settings using ITPV compared with conventional ventilation. Long-term studies are needed to determine whether this reduction in ventilation is maintained, and if so, if lung injury is reduced.

Animals↗
PubMed2000

Effect of nitric oxide and high-frequency oscillatory ventilation in meconium aspiration syndrome.

OBJECTIVE: To test the hypothesis that inhaled nitric oxide, when combined with high-frequency oscillatory ventilation, is an effective therapeutic agent in meconium aspiration syndrome. DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at The Children's National Medical Center. SUBJECTS: Five newborn piglets, 1-2 wks old, weighing 3.6 +/- 0.2 kg. INTERVENTION: Animals were anesthetized, paralyzed, intubated, and ventilated. Catheters were placed in the femoral vein and artery and the pulmonary artery. After 1 hr of recovery, 10 mL/kg of 20% meconium in normal saline solution was insufflated into the lungs. Animals were ventilated with a SensorMedics oscillator to maintain arterial blood gases in a normal range (pH, 7.35-7.45; Paco2, 40-45 mm Hg [5.3-6.0 kPa]; Pao2, 70-90 mm Hg [9.3-12.0 kPa]). Ventilator settings were increased as needed until maximum settings as follows: Fio2, 1.00; proximal oscillatory pressure amplitude, 36 cm H2O; mean airway pressure, 25 cm H2O; frequency, 10 Hz. After a short period of stabilization, inhaled nitric oxide was administered. Concentrations of 40, 20, and 10 ppm were given and measurements were taken after each exposure to inhaled nitric oxide and after its discontinuation. To assure that there was no additive effect of inhaled nitric oxide, each dose was given for 20 mins followed by a 15-min normalization period at 0 ppm. MEASUREMENTS AND MAIN RESULTS: Physiologic measurements, ventilatory settings, arterial blood gases, and methemoglobin were recorded at each study period. Measurements were taken after each exposure to inhaled nitric oxide and after its discontinuation. Arterial saturation and partial pressure of arterial oxygen (Pao2) were significantly lower after meconium aspiration when compared with baseline. Administration of inhaled nitric oxide improved oxygenation without a significant decrease in pulmonary artery pressure. CONCLUSION: In this model of meconium aspiration syndrome, short-term exposure to inhaled nitric oxide when combined with high-frequency oscillatory ventilation improved oxygenation secondary to better distribution of inhaled nitric oxide. The increase in oxygenation may be secondary to improved ventilation perfusion mismatch, as the primary etiology of hypoxia in this model may be a combination of parenchymal lung disease and pulmonary hypertension.

Journal Article↗
PubMed1999

Nitrogen dioxide formation during inhaled nitric oxide therapy.

BACKGROUND: Nitrogen dioxide (NO2) is a toxic by-product of inhalation therapy with nitric oxide (NO). The rate of NO2 formation during NO therapy is controversial. METHODS: The formation of NO2 was studied under dynamic flows emulating a base case NO ventilator mixture containing 80 ppm NO in a 90% oxygen matrix. The difficulty in measuring NO2 concentrations below 2 ppm accurately was overcome by the use of tunable diode laser absorption spectroscopy. RESULTS: Using a second-order model, the rate constant, k, for NO2 formation was determined to be (1.19 +/- 0.11) x 10(-11) ppm-2s-1, which is in basic agreement with evaluated data from atmospheric literature. CONCLUSIONS: Inhaled NO can be delivered safely in a well-designed, continuous flow neonatal ventilatory circuit, and NO2 formation can be calculated reliably using the rate constant and circuit dwell time.

Administration, Inhalation↗
PubMed1998

Use of nitric oxide in meconium aspiration syndrome: lack of response.

PURPOSE: To test the hypothesis that inhaled nitric oxide (INO) may not be an effective therapeutic agent in meconium aspiration syndrome (MAS). DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at The Children's National Medical Center. SUBJECTS: Seven newborn pigs, 2-7 days old, weighing 2.8 +/- 0.17 kg were used for the study. MATERIALS AND METHODS: Animals were anaesthetized, paralysed, intubated and ventilated. Catheters were placed in the jugular vein, carotid artery, and pulmonary artery. After 1 h of recovery 10 ml/kg of 20% meconium in normal saline solution was insufflated into the lungs. Animals were ventilated to maintain ABGs in a normal range, i.e. pH = 7.35-7.45, PaCO2 = 40-45, and PaO2 = 70-90 torr. Ventilator settings were increased as needed until maximum settings of: FiO2 = 1.00, PIP = 40, IMV = 60. After 2 h of conventional ventilation or demonstration of significant lung disease by failure to maintain desired blood gases on maximum ventilator settings, INO was administered for 20 min in concentrations of 10, 20 and 40 ppm. To ensure that there was no additive effect of INO, a 15-min normalization period at 0 ppm was allowed between each dose of INO. Physiologic measurements, ventilatory settings, arterial blood gases, and methemoglobin were recorded at each study period. Measurements were taken after each exposure to INO and after its discontinuation. RESULTS: Arterial saturation (SaO2) and PaO2 were significantly lower ([81 +/- 18] and [54 +/- 14], respectively) and PAP was significantly higher [24 +/- 3] after MAS when compared with baseline. Administration of INO did not improve oxygenation nor decrease PAP at any of the study doses. CONCLUSION: In this model of MAS, short-term exposure to INO did not decrease PAP nor improve oxygenation. It may be postulated that poor distribution of INO caused by the obstructive nature of this disease may be responsible for the lack of response in this disease state, or that the primary etiology for hypoxia is parenchymal lung disease and not pulmonary hypertension.

Administration, Inhalation↗
PubMed1997

Reduced airway resistance and work of breathing during mechanical ventilation with an ultra-thin, two-stage polyurethane endotracheal tube (the Kolobow tube).

OBJECTIVES: To compare dynamic pulmonary function studies using the ultrathin walled Kolobow endotracheal tube, with conventional endotracheal tubes of similar external diameter on rabbits during mechanical ventilation. To test the hypothesis that the increased internal diameter of the Kolobow tube will result in decreased airway resistance and work of breathing. DESIGN: Controlled animal study. SETTING: Institutional animal research facility. SUBJECTS: Adult female Dutch Belted rabbits (n = 6), weighing 1.4 to 1.6 kg. INTERVENTIONS: The animals were initially intubated with a conventional endotracheal tube (2.5-mm internal diameter; 3.6-mm outer diameter); they were paralyzed and placed on a mechanical ventilator. Ventilatory settings were adjusted to obtain standard arterial blood gases: pH of 7.35 to 7.45; PaCO2 of 35 to 40 torr (4.7 to 5.3 kPa), and PaO2 of 90 to 100 torr (12.0 to 13.3 kPa). After the stabilization period, pulmonary function tests (PFTs) were measured (period 1), the conventional endotracheal tube was replaced with a Kolobow tube, and PFTs were measured again and recorded (period 2). While continuously monitoring tidal volume, the peak inspiratory pressure was decreased to match the tidal volume measured during ventilation with the conventional endotracheal tube. Once the desired tidal volume was reached, PFTs were recorded (period 3). Flows were unchanged during the experiment and the length of the endotracheal tubes was the same for both the conventional and the Kolobow tube. MEASUREMENTS AND MAIN RESULTS: Mean values of the airway resistance and work of breathing from periods 1 and 3 were compared using the Student's t-test. There was a 59% decrease in total airway resistance (p = .001) and 45% decrease in the work of breathing (p = .0006). CONCLUSIONS: The use of the ultrathin walled Kolobow endotracheal tube resulted in significant decreases in airway resistance and work of breathing, which has the potential for improving the ventilatory mechanics in very small premature newborns.

Airway Resistance↗
PubMed1997

Effect of nitric oxide in meconium aspiration syndrome after treatment with surfactant.

OBJECTIVE: To test the hypothesis that inhaled nitric oxide may be an effective therapeutic agent in meconium aspiration syndrome and may improve oxygenation after pretreatment with surfactant. DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at The Children's National Medical Center. SUBJECTS: Eight newborn pigs, 1 to 2 wks of age, 4.1 +/- 0.4 kg, were used for the study. INTERVENTIONS: Animals were anesthetized, paralyzed, intubated, and mechanically ventilated. Catheters were placed in the femoral vein and artery, and in the pulmonary artery. After 1 hr of recovery, 10 mL/kg of 20% meconium in normal saline solution was insufflated into the lungs. Animals were ventilated to maintain arterial blood gases in a normal range (i.e., pH of 7.35 to 7.45, Paco2 of 40 to 45 torr [5.3 to 6.0 kPa], and Pao2 of 70 to 90 torr [9.3 to 12.0 kPa]). Ventilatory settings were increased, as needed, until the following maximum settings were reached: FIO2 of 1.0; peak inspiratory pressure of 40 cm H2O; and intermittent mandatory ventilation of 60 breaths/min. After 2 hrs of conventional ventilation or demonstration of clinically important lung disease by failure to maintain desired blood gases on the maximum ventilatory settings, 4 mL/kg of beractant was given intratracheally. After a short period of stabilization following surfactant therapy, inhaled nitric oxide was administered. Concentrations of 40, 20, and 10 parts per million were given. To assure that there was no additive effect of inhaled nitric oxide, each dose was given for 20 mins, followed by a 15-min normalization period at 0 parts per million. MEASUREMENTS AND MAIN RESULTS: Physiologic measurements, ventilatory settings, arterial blood gases, and methemoglobin were recorded at each study period. Measurements were taken after each exposure to inhaled nitric oxide and after its discontinuation. Arterial oxygen saturation and Pao2 were significantly lower after meconium aspiration when compared with baseline values. After treatment with surfactant, administration of inhaled nitric oxide improved oxygenation without a significant decrease in pulmonary arterial pressure. CONCLUSIONS: In this model of meconium aspiration syndrome, short-term exposure to inhaled nitric oxide after treatment with surfactant improved oxygenation secondary to better distribution of inhaled nitric oxide. The increase in oxygenation may be secondary to an improved ventilation/perfusion mismatch, since the primary etiology of hypoxia in this model may be a combination of parenchymal lung disease and pulmonary hypertension.

Administration, Inhalation↗
PubMed1997

Use of intratracheal pulmonary ventilation versus conventional ventilation in meconium aspiration syndrome in a newborn pig model.

OBJECTIVE: To determine whether intratracheal pulmonary ventilation (ITPV) allows for effective oxygenation and ventilation at lower mean airway pressures and peak inspiratory pressures than conventional ventilation in a piglet model of meconium aspiration syndrome. DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at Children's National Medical Center, Washington, DC. SUBJECTS: Twenty newborn piglets, 2 to 7 days of age, weighing 1.8 to 2.8 kg. INTERVENTION: Animals were anesthetized, paralyzed, intubated, and ventilated. Femoral arterial and venous catheters were inserted; 5 mL/kg of 20% meconium in normal saline was instilled into the endotracheal tube. Animals were randomized to either ITPV or conventional ventilation, and settings were adjusted to maintain ideal blood gases, i.e., pH 7.35 to 7.45, PCO2 40 to 45 torr (5.3 to 6 kPa), PO2 80 to 100 torr (10.7 to 13.3 kPa), and SaO2 > or = 90%. Ventilatory settings were adjusted as needed to a maximum of: FIO2 1.0, peak inspiratory pressure 40 cm H2O, positive end-expiratory pressure 5 cm H2O, and respiratory rate 80 breaths/min. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases were taken every 30 mins for 4 hrs and ventilatory settings were adjusted to maintain optimal blood gases. Heart rate, mean arterial blood pressure, and arterial saturation were monitored continuously. The animals in the ITPV group had significantly lower peak inspiratory pressure at 1, 2, 3, and 4 hrs after meconium instillation (p < .018) and significantly lower mean airway pressure at 2, 3, and 4 hrs after meconium instillation (p < .03). The mean peak inspiratory pressure in the ITPV animals ranged from 17 +/- 2.7 cm H2O at baseline to 16.6 +/- 5.7 cm H2O at 4 hrs compared with 16.5 +/- 2.7 cm H2O at baseline to 31.8 +/- 9.1 cm H2O at 4 hrs in the conventionally ventilated animals (p < .04). The mean airway pressure ranged from 6.3 +/- 1.1 mm Hg at baseline to 6.8 +/- 2.5 mm Hg at 4 hrs in the ITPV group compared with 5.5 +/- 1.2 mm Hg at baseline to 10.7 +/- 3.4 mm Hg at 4 hrs in the conventional ventilation group (p < .03). The lungs of the ITPV animals were less hemorrhagic and had less pathologic evidence of injury than the lungs of the conventionally ventilated animals. CONCLUSIONS: These results indicate that ITPV can be used to effectively ventilate and oxygenate piglets with meconium aspiration syndrome at lower mean airway pressures and peak inspiratory pressures than conventional ventilation. This lower pressure causes less injury to the lungs of the animals.

Animals↗
PubMed1997

In-line pressures generated in small-bore central venous catheters during power injection of CT contrast media.

PURPOSE: To determine in-line pressures generated in small-bore central venous catheters during power injection of computed tomographic (CT) contrast media. MATERIALS AND METHODS: Five 3.0-7.0-F central venous catheters for pediatric patients were tested at full and half lengths in vitro. In-line pressures were measured during power injection of three contrast media. Rates of injection were increased in steps from 0.1 to 5.0 mL/sec or until a peak pressure of 100 psi (700 kPa) was achieved. The maximum tolerated flow rate was determined with reference to the manufacturer's suggested operating pressure limit for each catheter. RESULTS: At full length, the maximum tolerated flow rates were as follows: 2-3 mL/sec for the large lumen and 1-1.4 mL/sec for the small lumen of the 7.0-F double-lumen catheter; 0.2-0.4 and 0.8-1.2 mL/sec for the 3.0- and 4.0-F peripherally inserted central catheters, respectively; 0.7-1.2 mL/sec for the 6.6-F catheter; and only 0.2 mL/sec for the 4.2-F catheter, which ruptured during testing at higher flow rates. CONCLUSION: Flow rates were documented at which certain small-bore central venous catheters should tolerate power injection of CT contrast media with peak pressures remaining below the manufacturer's recommended operating pressure limits. These data may serve as a guide for clinical use.

Catheterization, Central Venous↗
PubMed1995

Improved oxygenation with reduced recirculation during venovenous extracorporeal membrane oxygenation: evaluation of a test catheter.

OBJECTIVE: To determine whether modifications of the original design of a double-lumen, venovenous, extracorporeal membrane oxygenation (ECMO) catheter would reduce recirculation and improve oxygenation during venovenous ECMO. DESIGN: Prospective, interventional study. SETTING: The animal research laboratory at The Children's National Medical Center. SUBJECTS: Six newborn lambs, 1 to 7 days old and weighing 4.7 +/- 0.9 kg. INTERVENTIONS: Animals were anesthetized, intubated and ventilated. The ductus arteriosus was ligated. Femoral artery and vein, cephalic jugular vein, and pulmonary artery catheters were placed. After systemic heparinization, the test catheter (with venous drainage holes moved away from the arterial return holes) was placed in the right internal jugular vein and advanced into the right atrium. The animal was placed on ECMO and stabilized, with the ventilator settings decreased to a peak inspiratory pressure of 15 cm H2O, peak positive end-expiratory pressure of 5 cm H2O, respiratory rate of 15 breaths/min, and an FIO2 of 0.21. ECMO flows were increased in 100-mL increments from 200 to 600 mL/min, with measurements taken 15 mins after each change. The test catheter was removed, the double-lumen, venovenous ECMO catheter was placed, and the studies were repeated. MEASUREMENTS AND MAIN RESULTS: Heart rate, mean arterial pressure, PaO2, jugular cerebral oxygen saturation, pulmonary artery oxygen saturation, mixed venous oxygen saturation, and postmembrane circuit pressures were measured at each study period. The test catheter improved oxygenation significantly, with higher systemic PaO2, higher pulmonary artery and cerebral oxygen saturations, and lower mixed venous oxygen saturations (indicating less recirculation). With the test catheter, PaO2 levels ranged from 62 +/- 6 torr (8.3 +/- 0.8 kPa) to 112 +/- 12 torr (14.9 +/- 1.6 kPa), compared with 46 +/- 4 torr (6.1 +/- 0.5 kPa) to 59 +/- 2 torr (7.9 +/- 0.3 kPa) for the double-lumen, venovenous ECMO catheter (p < or = .001). These findings indicate that at all flow rates studied, less recirculation occurred with the test catheter than with the double-lumen, venovenous ECMO catheter. CONCLUSIONS: These findings indicate that the redesign of the double-lumen, venovenous ECMO catheter, as outlined in this study, resulted in a significant reduction of recirculation, thereby resulting in a significant improvement in oxygenation while on venovenous ECMO. This newly designed catheter makes venovenous ECMO more effective, and represents a design that could be used for pediatric and/or adult ECMO.

Animals↗
PubMed1992

In vitro evaluation of the Mera Silox-S 0.5 and 0.8 m 2 silicone hollow-fibre membrane oxygenator for use in neonatal ECMO.

The Mera Silox-S is a silicone hollow-fibre membrane oxygenator made up of thousands of fibres in a clear polycarbonate housing. Being a silicone membrane it does not have the plasma leakage problem associated with conventional microporous hollow fibres when used in a long-term application. This device (Mera Senko Medical Instrument Co., Japan) is made in three sizes: 0.3, 0.5 and 0.8 m 2. The performance of the 0.5 m 2 and 0.8 m 2 Silox-S membrane oxygenators was tested in vitro using filtered ovine blood and a customized test circuit designed to provide a continuous source of de-oxygenated, CO 2-laden blood, according to the AAMI standard for oxygenator performance. The 0.8 m 2 membrane provided excellent oxygenation, with a transfer rate of 13.0-43.5 ml/min for blood flows of 200-800 ml/min. CO 2 transfer over the same range of flows measured 32.3-40.8 ml/min. Flow rates of 100-500 ml/min for the 0.5 m 2 membrane provided an oxygen transfer of 6.8-28.3 ml/min and would probably not be suited for the existing neonatal ECMO population. A matter of concern with both oxygenators was an increased pressure drop for blood flow through the devices. The delta P for the 0.5 m 2 for flows of 100-500 ml/min ranged from 155 +/- 7 mmHg to 516 +/- 6 mmHg. For the 0.8 m 2, delta P was 194 +/- 39 mmHg to 492 +/- 53 mmHg for flows of 200-800 ml/min. Overall, favourable results support further long-term evaluation for potential use in neonatal ECMO.

Evaluation Studies as Topic↗
PubMed1984

Use of the rebreathing method in the differential diagnosis of congenital heart disease and persistent fetal circulation.

The differential diagnosis of congenital heart disease from persistent fetal circulation is clinically difficult and cardiac catheterization is often needed. The development of a safe, new technique for use of the rebreathing method has allowed the determination of effective pulmonary blood flow, lung tissue volume, lung diffusion capacity and functional residual capacity in 7 critically ill, ventilator-dependent infants at the bedside. Analysis of the data revealed highly significant differences for lung tissue volume and diffusion capacity, a minimally significant difference for effective pulmonary blood flow and no difference for functional residual capacity between the groups. Use of this method allows not only attainment of clinically useful information but also permits better insight into the pathophysiology of the disease state.

Animals↗
PubMed1981

Measurement of tracheal airflow in newborns by a differential flow system.

The differential arrangement of two pneumotachographs in a gas blow-by system, upstream and downstream from the patient connection port, permits accurate measurement of the tracheal air flow without introduction of flowmeter dead-space. The method does not require but will accept a constant background gas flow rate and permits humidification and easy switching of the inhalant gases. The admissible background flow rates limiting measurement errors below 5% in the range of tidal volumes relevant for newborns for two sizes of commercially available pneumotachographs were found to be -3 L/min and 0-12 L/min, respectively. The lack of restrictions imposed on the properties of the background flow source makes the differential system especially suitable for measurement of ventilation and pulmonary mechanics in spontaneously breathing or mechanically ventilated newborn infants.

Airway Resistance↗
PubMed1980

Time-weighted averaging for nitrous oxide: an automated method.

An automated method of obtaining a time-weighted average of nitrous oxide levels in an operating room was compared with a standard method. The automated method consisted of electronic integration of the voltage output of a nitrous oxide analyzer using a multimeter-microprocessor. The standard method utilized a bag and pump to collect a room air sample, which was subsequently analyzed with a nitrous oxide analyzer. There was a high degree of correlation (r = 0.99) between the two methods. It is concluded that the automated method is an accurate alternative and offers institutions a simple, cost-effective method of monitoring and documenting results of pollution control programs in anesthetizing locations.

Autoanalysis↗
PubMedDate not supplied

Maximum blood flow rates for arterial cannulae used in neonatal ECMO.

The arterial cannulae used in neonatal ECMO cause hemolysis and red blood cell damage at elevated blood flows. Hemolysis in extracorporeal circuits has been found to occur with shear stress greater than 132 dynes/cm2, turbulence as measured by Reynold's number greater than 1,000, and velocity greater than 120 to 200 cm/sec. These parameters need to be considered when sizing the proper arterial cannula for a required flow rate. In-vitro measurements of the pressure drop across six arterial cannulae at varying flow rates were performed using human blood with a hematocrit of 43%. Shear stress, Reynold's number, velocity, and pressure drop were calculated for each catheter at flow rates from 50 to 1,000 cc/min. The maximum mean flow rate to maintain the shear stress, Reynold's number, velocity, and pressure drop within the accepted range, was determined for each cannula. Recommended maximum blood flow rates for each of the six cannulae are given. Internal diameter, length, and cannula geometry appear to be the factors most affecting the flow achievable without causing red blood cell damage and hemolysis. Ten French Biomedicus, 10 French Cook, and 10 French Elecath arterial cannulae appear best suited to deliver the range of blood flow rates used in neonatal ECMO.

Blood Flow Velocity↗