Cannula Flow Research Articles

Desenlaces clínicos en pacientes con diagnóstico de neumonía relacionada con SARS-CoV-2 manejados con cánula de alto flujo, una experiencia clínica. (Estudio CANALF)

IntroductionThe inclusion of non-invasive ventilatory support systems in the management of ARDS in adults during the current pandemic, has been a lifeline given the lack of resources in the current international health situation. Systems such as the high flow nasal cannula have proven not to be just a temporary ventilatory system while awaiting invasive mechanical ventilation, on the contrary it has been shown that the high flow nasal cannula is an effective therapy tool in ARDS. ObjectiveTo provide an easy guideline for the management of high-flow cannulas in hospitalized patients with severe pneumonia due to ATS criteria secondary to SARS COV2-COVID 19. Materials and methodsThis is a prospective, single-centre observational study, including 59 patients, all with a diagnosis of SARS-CoV-2-related pneumonia between January and April 2021. The patients were initially managed in an intermediate care unit with high nasal cannula flow (HFNC). ResultsWe were able to show that there is a statistically significant correlation between age > 65 years and respiratory rate ≥28 and mortality; likewise, between age > 50 years, NEWS > 6 and again a respiratory rate ≥28 with treatment failure. ConclusionsHFNC in respiratory failure related to coronavirus disease 2019 should become a viable management alternative, particularly in settings with limited access to intensive care unit resources, taking the indications into account and recognizing that a high percentage of patients who receive it can be successfully weaned without the need for invasive mechanical ventilation.

Optimization of Flow Dynamics During the HeartWare HVAD to HeartMate 3 Exchange: A Computational Study Assessing Differential Surgical Techniques

<h3>Purpose</h3> With the discontinuation of the HeartWare HVAD, patients who experience a device complication will require exchange to another pump. The HeartMate 3 (HM3) is now the only commercially available LVAD in the United States. The optimal surgical configuration for connecting the 10 mm HVAD outflow graft to the 14 mm HM3 outflow graft has yet to be defined. <h3>Methods</h3> A lumped-parameter computational fluid dynamic (CFD) model of the circulatory system, including HQ curves of the HM3 was created. The model was coupled with 3D CFD model, in which outflow cannula flow served as the boundary conditions for blood flow simulations in the aorta. In total, 4 variations of the outflow cannula were tested: 1) Anastomosis near the pump (long 10 mm); 2) Anastomosis near the aorta (long 14 mm); 3) Anastomosis 5 cm from the aorta (mid transition); 4) The entire cannula 14 mm (complete exchange). The flow patterns were characterized based on the results of 3D CFD simulations. <h3>Results</h3> Maximum velocity was highest in the configurations with longer sections of 10 mm graft (long 10 mm, 4.20 m/s; long 14 mm, 4.12 m/s, mid transition, 4.18 m/s; complete exchange, 2.27 m/s). This resulted in a 176% larger blood volume exposed to very high shear rate (SR) >5000 s⁻¹ for the long 10 mm vs the long 14 mm configuration (0.59 ml vs 0.21 ml) and a 805% increase compared to the complete exchange (0.065 ml). There was a 21% increase in right coronary flow (0.29 ml/s vs 0.24 ml/s) and a 22% increase in left coronary flow (1.41 ml/s vs 1.16 ml/s) with the long 10 mm compared to the 14 mm configuration. When the long 10 mm cannula was compared against complete exchange, the flow increase was 26% (0.29 ml/s vs 0.23 ml/s) for right coronary and 62% (1.41 ml/s vs 0.87 ml/s) for left coronary. <h3>Conclusion</h3> When planning for a HVAD to HM3 exchange, the location of the anastomosis and relative length of the 10 and 14 mm grafts has important implications related to shear rate and coronary blood flow which should be accounted for during surgery.

Right-sided heart reperfusion ("Berlin bridge technique") for right ventricle support during left ventricular assist device (LVAD) implantation.

Right-sided heart reperfusion ("Berlin bridge technique") for right ventricle support during left ventricular assist device (LVAD) implantation.

Long term left ventricular impairment after SARS-COV2 infection

Abstract Funding Acknowledgements Type of funding sources: None. Introduction The impact of acute infection by SARS-COV2 on the cardiovascular system has been previously reported in the literature, with a higher propensity in patients with more serious pattern of disease and pro-inflammatory status. Nevertheless, the long-term burden and sequels of COVID-19 on the cardiovascular system is still unknown. Purpose To evaluate the long-term impact of COVID-19 on left ventricular function in patients with severe clinical presentation requiring intensive care hospitalization. Methods This was a single-center observational, prospective study which included patients requiring admission to the Intensive Care Unit (ICU) due to COVID-19 infection from January to November 2020. All discharged patients were contacted to perform a clinical, electrocardiographic and echocardiographic evaluation and those who accepted were included on the protocol. Baseline and clinical characteristics were collected from clinical reports. For the global longitudinal strain (GLS) analysis all patients with significant wall motion abnormalities and valvular cardiopathy were excluded. Statistical analysis was performed with Mann-Whitney and a safety cut-off was established with ROC curve analysis. Results A total of 43 patients were included (mean age 64 ± 12, 67.4% males). During SARS-COV2 infection 49% presented with severe ARDS and 51% with moderate, 35% required invasive mechanical ventilation, 14% noninvasive mechanical ventilation and 52% with high nasal flow cannula. On the follow-up analysis, fatigue was the most reported in symptom (52% patients) and the majority did not present other signs or symptoms suggestive of heart failure, with the mean NT-proBNP of 49 ± 389 pg/dL. The standard ECG and echocardiogram did not show significant changes with a mean LVEF of 58 ± 7.8 and mean TAPSE of 21 ± 4. The strain analysis showed low value of GLS (mean GLS of -17.14 ± 2.36) for a reference cut-off of -18%, suggesting subclinical left ventricular dysfunction in this subset of patients with preserved ejection fraction. Maximum CPR values during ICU did not correlate either with the extent of disease evolvement in CT (p= NS) or ARDS severity (p= NS). Nevertheless, maximum CPR correlated significantly with GLS reduction (R = 0.44, p = 0.019). A CPR value higher than iger30mg/dL had 100% specificity for GLS reduction and a cut-off of 14gm/dL reported a sensitivity of 65% and specificity pf 75% for reduction in GLS. Conclusion In our study, we reported subclinical impairment in left ventricular function detected with global longitudinal strain after serious infection with SARS-COV2. The detected myocardial dysfunction was related with higher inflammatory as expressed by CPR values. Long-term monitoring of these patients should be undertaken in order to timely detect late complications. Abstract Figure.

Controlled Subretinal Injection Pressure Prevents Damage in Pigs

Introduction: Administration of retinal gene and stem cell therapy in patients with retinal degenerative diseases is in many cases dependent on a subretinal approach. It has been indicated that manual subretinal injection is associated with outer retinal damage, which may be explained by a high flow rate in the injection cannula. In the present porcine study, we evaluated flow-related retinal damage after controlled subretinal injection at different flow rates. Methods: The flow rate through a 41G cannula was estimated at different injection pressures (6–48 pounds per square inch [PSI]) in an in vitro setup. A linear correlation between the flow rate and injection pressure was found from 6 to 32 PSI. In full anesthesia, 12 pigs were vitrectomized and received a controlled subretinal injection of 300 μL balanced saline solution at injection pressures of 14, 24, and 32 PSI (four in each group). Prior to surgery and 2 and 4 weeks after surgery, the eyes were examined by multifocal electroretinogram (mfERG) and fundus photographs. At the end of follow-up, the eyes were enucleated for histology. Results: The in vitro flow study determined that the flow in a 41G cannula shifts from laminar to turbulent at 32 PSI and that the manual injection flow is turbulent. In the porcine study, we showed a significant difference in retinal pigment epithelium (RPE) damage between the three pressure groups (p = 0.0096). There was no significant difference in damage to the outer retina (p = 0.1526), but the high-pressure group (32 PSI) had the most outer retinal damage. The middle-pressure group (24 PSI) showed minimum retinal damage. There was no significant change in the mfERG ratios during follow-up. Discussion/Conclusion: This study indicates that an injection pressure at approximately 24 PSI might be safe for subretinal delivery. Retinal damage at low injection pressures may be explained by mechanical damage to the RPE due to prolonged needle time in the subretinal space, while retinal damage at high pressures can be related to high flow in the injection cannula. Controlled subretinal injection pressure of 24 PSI showed minimum mechanical- and flow-related damage to the porcine retina.

Optimizing high-flow nasal cannula flow settings in adult hypoxemic patients based on peak inspiratory flow during tidal breathing

BackgroundOptimal flow settings during high-flow nasal cannula (HFNC) therapy are unknown. We investigated the optimal flow settings during HFNC therapy based on breathing pattern and tidal inspiratory flows in patients with acute hypoxemic respiratory failure (AHRF).MethodsWe conducted a prospective clinical study in adult hypoxemic patients treated by HFNC with a fraction of inspired oxygen (FIO2) ≥ 0.4. Patient’s peak tidal inspiratory flow (PTIF) was measured and HFNC flows were set to match individual PTIF and then increased by 10 L/min every 5–10 min up to 60 L/min. FIO2 was titrated to maintain pulse oximetry (SpO2) of 90–97%. SpO2/FIO2, respiratory rate (RR), ROX index [(SpO2/FIO2)/RR], and patient comfort were recorded after 5–10 min on each setting. We also conducted an in vitro study to explore the relationship between the HFNC flows and the tracheal FIO2, peak inspiratory and expiratory pressures.ResultsForty-nine patients aged 58.0 (SD 14.1) years were enrolled. At enrollment, HFNC flow was set at 45 (38, 50) L/min, with an FIO2 at 0.62 (0.16) to obtain an SpO2/FIO2 of 160 (40). Mean PTIF was 34 (9) L/min. An increase in HFNC flows up to two times of the individual patient’s PTIF, incrementally improved oxygenation but the ROX index plateaued with HFNC flows of 1.34–1.67 times the individual PTIF. In the in vitro study, when the HFNC flow was set higher than PTIF, tracheal peak inspiratory and expiratory pressures increased as HFNC flow increased but the FIO2 did not change.ConclusionMean PTIF values in most patients with AHRF were between 30 and 40 L/min. We observed improvement in oxygenation with HFNC flows set above patient PTIF. Thus, a pragmatic approach to set optimal flows in patients with AHRF would be to initiate HFNC flow at 40 L/min and titrate the flow based on improvement in ROX index and patient tolerance.Trial registration: ClinicalTrials.gov (NCT03738345). Registered on November 13th, 2018. https://clinicaltrials.gov/ct2/show/NCT03738345?term=NCT03738345&draw=2&rank=1

The Effect of Parameter Variation on Spiral Flow Inducing Cannula Performances

Spiral flow-inducing cannula has been shown in previous research to exhibit a considerable effect on flow hemodynamic. However, there is still room for improvement. In this study, several design variations were tested to determine which variants were the best in terms of flow reduction. Computational Fluid Dynamics (CFD) software was used to simulate flow within a spiral flow-inducing cannula with several variations from chamber width and angle differences. The variants were compared against each other by using several flow parameters and a selection method was employed to determine which model was the best. It was found that a variant that has the widest chamber (14 mm) and biggest angle opening (70°) from the chamber to the cannula tube was the best in several parameters, and as such was chosen as the best variant. When compared with the standard straight cannula, the reduction in flow output was recorded to be 30% which is deemed significantly. In conclusion, spiral flow cannula recorded better hemodynamic effects with lower outflow velocity and wall shear stress value.

Effects of different high-flow nasal cannula flow rates on swallowing function

BackgroundHigh-flow nasal cannula therapy is used as a noninvasive treatment for people with acute respiratory disease. The aim of this study was to assess the impact of high-flow nasal cannula different flow rates on different characteristics of swallowing in healthy volunteers. MethodsA prospective cohort study where healthy adult volunteers were subject to high-flow nasal cannula at different flow rates (0, 10, 20, 30, 40, and 50 L/min, in random order). The 30-mL water swallow test, repetitive saliva swallowing test, and 0-100 mm visual analog scale assessed aspiration, swallow frequency and effort, respectively. FindingsThirty subjects (mean age 30 years) were enrolled. Nine subjects (30.0%) choked at 10, 40 and 50 L/min during the 30-mL water swallow test (p < 0.05). Swallowing effort was increased during flow rates ≥20 compared to 10 L/min (p < 0.05). Flow rates ≥20 L/min resulted in lower number of swallows during the repetitive saliva swallowing test compared to 0 and 10 L/min (p < 0.05). InterpretationHigh-flow nasal cannula flow rates above 40 L/min associated with choking (increased risk of aspiration), and was associated with decreased swallowing function in healthy volunteers. It may be important to assess swallowing function in patients with various clinical conditions and treated with high-flow nasal cannula, especially those at risk of aspiration pneumonia.

Reply: Will the new tool used for cerebral perfusion be able to "keep it simple" or not?

We appreciate the comments provided by the authors about the new AV Flow cannula (MedEurope Srl, Bologna, Italy), used for antegrade selective cerebral perfusion in arch surgery. They better clarify the positive features of this interesting device, including the possibility of guidewire introduction and suture of epiaortic vessels in the graft without having the bulk of the cannula.1 Nevertheless, a very important concept to observe in surgery is to standardize and simplify the procedure to reduce complications and achieve durable outcomes, especially in complex scenarios.

Immediate Physiological Responses to Inspiratory Flow Limited Events in Mild Obstructive Sleep Apnea.

Rationale: Inspiratory flow limitation (IFL), characterized by flattening of individual breaths on the airflow/time tracing, is a noninvasive indicator of elevated upper airway resistance. An IFL "event" in isolation has not been defined, nor has the ability to reproducibly identify event occurrence been tested. IFL events and their association with immediate physiological responses-as well as the impact of characteristics such as age, sex, sleep stage, sleepiness, and event duration on their association with such outcomes-have not been studied. Symptomatic patients with a normal to mildly abnormal apnea-hypopnea index who have predominant IFL on their polysomnography may benefit from treatment. Objectives: To test the reproducibility of identifying IFL events and their termination and to determine the frequency of the immediate physiological response to their occurrence, including desaturation, electroencephalography (EEG) arousal, and increased heart rate (HR). Methods: Fifty-eight patients with obstructive sleep apnea (OSA) underwent full diagnostic polysomnography. IFL events and their termination were identified manually using predefined rules from the unscored nasal cannula flow channel alone and were evaluated for responses such as EEG arousal, oxygen desaturation of ⩾3%, and HR increase. Results: Interscorer reliability was acceptable, with an average percent agreement for occurrence of 82% ± 3%. Of all IFL events, 24% (regardless of the definition) were not associated with an EEG arousal, an increase in HR, or O2 desaturation. Of all IFL events scored, 25% caused O2 desaturation, 40% were associated with an EEG arousal, and 55% were associated with an increase in HR; 67% caused either an EEG arousal and/or an increase in HR. Responses were observed to occur either in isolation or in combination. IFL events that terminated with at least two non-IFL breaths, one of which had a 200% increase in amplitude, were significantly associated with O2 desaturation, EEG arousal, and increase in HR compared with events that ended in one non-IFL breath. IFL events that had a >50% reduction in flow amplitude compared with baseline were significantly associated with O2 desaturation compared with events that had a 30% reduction or less. Conclusions: Most IFL events resulted in immediate physiological responses, and no single consequence reliably occurred after every event. We propose a framework that can incorporate the scoring of IFL events into assessing the diagnosis and severity of OSA and suggest that no single consequence be used to define IFL as a respiratory event. The relationship of IFL events to OSA outcomes remains to be tested.

Flow Dynamics and Mixing in Extracorporeal Support: A Study of the Return Cannula.

Cannulation strategies in medical treatment such as in extracorporeal life support along with the associated cannula position, orientation and design, affects the mixing and the mechanical shear stress appearing in the flow field. This in turn influences platelet activation state and blood cell destruction. In this study, a co-flowing confined jet similar to a return cannula flow configuration found in extracorporeal membrane oxygenation was investigated experimentally. Cannula diameters, flow rate ratios between the jet and the co-flow and cannula position were studied using Particle Image Velocimetry and Planar Laser Induced Fluorescence. The jet was turbulent for all but two cases, in which a transitional regime was observed. The mixing, governed by flow entrainment, shear layer induced vortices and a backflow along the vessel wall, was found to require 9–12 cannula diameters to reach a fully homogeneous mixture. This can be compared to the 22–30 cannula diameters needed to obtain a fully developed flow. Although not significantly affecting mixing characteristics, cannula position altered the development of the flow structures, and hence the shear stress characteristics.

Left Ventricular Assist Device Flow Pattern Analysis Using a Novel Model Incorporating Left Ventricular Pulsatility.

Our current understanding of flow through the circuit of left ventricular assist device (LVAD), left ventricle and ascending aorta remains incompletely understood. Computational fluid dynamics, which allow for analysis of flow in the cardiovascular system, have been used for this purpose, although current simulation models have failed to fully incorporate the interplay between the pulsatile left ventricle and continuous-flow generated by the LVAD. Flow-through the LVAD is dependent on the interaction between device and patient-specific factors with suboptimal flow patterns evoking increased risk of LVAD-related complications. Computational fluid dynamics can be used to analyze how different pump and patient factors affect flow patterns in the left ventricle and the aorta. Computational fluid dynamics simulations were carried out on a patient with a HeartMate II. Simulations were also conducted for theoretical scenarios substituting HeartWare HVAD, HeartMate 3 (HM3) in continuous mode and HM3 with Artificial Pulse. An anatomical model of the patient was reconstructed from computed tomography (CT) images, and the LVAD outflow was used as the inflow boundary condition. The LVAD outflow was calculated separately using a lumped-parameter-model of the systemic circulation, which was calibrated to the patient based on the patient-specific ventricular volume change reconstructed from 4 dimensional computed tomography and pulmonary capillary wedge pressure tracings. The LVADs were implemented in the lumped-parameter-model via published pressure head versus flow (H-Q) curves. To quantify the flushing effect, virtual contrast agent was released in the ascending aorta and its flushing over the cycles was quantified. Shear stress acting on the aortic endothelium and shear rate in the bloodstream were also quantified as indicators of normal/abnormal blood flow, especially the latter being a biomarker of platelet activation and hemolysis. LVAD speeds for the HVAD and HM3 were selected to match flow rates for the patient's HMII (9,000 RPM for HMII, 5,500 RPM for HM3, and 2,200 RPM for HVAD), the cardiac outputs were 5.81 L/min, 5.83 L/min, and 5.92 L/min, respectively. The velocity of blood flow in the outflow cannula was higher in the HVAD than in the two HeartMate pumps with a cycle average (range) of 0.92 m/s (0.78-1.19 m/s), 0.91 m/s (0.86-1.00 m/s), and 1.74 m/s (1.40-2.24 m/s) for HMII, HM3, and HVAD, respectively. Artificial pulse increased the peak flow rate to 9.84 L/min for the HM3 but the overall cardiac output was 5.96 L/min, which was similar to the continuous mode. Artificial pulse markedly decreased blood stagnation in the ascending aorta; after six cardiac cycles, 48% of the blood was flushed out from the ascending aorta under the continuous operation mode while 60% was flushed under artificial pulse. Shear stress and shear rate in the aortic arch were higher with the HVAD compared to the HMII and HM3, respectively (shear stress: 1.76 vs. 1.33 vs. 1.33 Pa, shear rate: 136 vs. 91.5 vs. 89.4 s-1). Pump-specific factors such as LVAD type and programmed flow algorithms lead to unique flow patterns which influence blood stagnation, shear stress, and platelet activation. The pump-patient interaction can be studied using a novel computational fluid dynamics model to better understand and potentially mitigate the risk of downstream LVAD complications.

The design of RIP belts impacts the reliability and quality of the measured respiratory signals

PurposeEvaluate the effect of respiratory inductance plethysmography (RIP) belt design on the reliability and quality of respiratory signals. A comparison of cannula flow to disposable cut-to-fit, semi-disposable folding and disposable RIP belts was performed in clinical home sleep apnea testing (HSAT) studies.MethodsThis was a retrospective study using clinical HSAT studies. The signal reliability of cannula, thorax, and abdomen RIP belts was determined by automatically identifying periods during which the signals did not represent respiratory airflow and breathing movements. Results were verified by manual scoring. RIP flow quality was determined by examining the correlation between the RIP flow and cannula flow when both signals were considered reliable.ResultsOf 767 clinical HSAT studies, mean signal reliability of the cut-to-fit, semi-disposable, and disposable thorax RIP belts was 83.0 ± 26.2%, 76.1 ± 24.4%, and 98.5 ± 9.3%, respectively. The signal reliability of the cannula was 92.5 ± 16.1%, 87.0 ± 23.3%, and 85.5 ± 24.5%, respectively. The automatic assessment of signal reliability for the RIP belts and cannula flow had a sensitivity of 50% and a specificity of 99% compared with manual assessment. The mean correlation of cannula flow to RIP flow from the cut-to-fit, semi-disposable, and disposable RIP belts was 0.79 ± 0.24, 0.52 ± 0.20, and 0.86 ± 0.18, respectively.ConclusionThe design of RIP belts affects the reliability and quality of respiratory signals. The disposable RIP belts that had integrated contacts and did not fold on top of themselves performed the best. The cut-to-fit RIP belts were most likely to be unreliable, and the semi-disposable folding belts produced the lowest-quality RIP flow signals compared to the cannula flow signal.

A mock circulation loop to test extracorporeal CO2 elimination setups

BackgroundExtracorporeal carbon dioxide removal (ECCO2R) is a promising yet limited researched therapy for hypercapnic respiratory failure in acute respiratory distress syndrome and exacerbated chronic obstructive pulmonary disease. Herein, we describe a new mock circuit that enables experimental ECCO2R research without animal models. In a second step, we use this model to investigate three experimental scenarios of ECCO2R: (I) the influence of hemoglobin concentration on CO2 removal. (II) a potentially portable ECCO2R that uses air instead of oxygen, (III) a low-flow ECCO2R that achieves effective CO2 clearance by recirculation and acidification of the limited blood volume of a small dual lumen cannula (such as a dialysis catheter).ResultsWith the presented ECCO2R mock, CO2 removal rates comparable to previous studies were obtained. The mock works with either fresh porcine blood or diluted expired human packed red blood cells. However, fresh porcine blood was preferred because of better handling and availability. In the second step of this work, hemoglobin concentration was identified as an important factor for CO2 removal. In the second scenario, an air-driven ECCO2R setup showed only a slightly lower CO2 wash-out than the same setup with pure oxygen as sweep gas. In the last scenario, the low-flow ECCO2R, the blood flow at the test membrane lung was successfully raised with a recirculation channel without the need to increase cannula flow. Low recirculation ratios resulted in increased efficiency, while high recirculation ratios caused slightly reduced CO2 removal rates. Acidification of the CO2 depleted blood in the recirculation channel caused an increase in CO2 removal rate.ConclusionsWe demonstrate a simple and cost effective, yet powerful, “in-vitro” ECCO2R model that can be used as an alternative to animal experiments for many research scenarios. Moreover, in our approach parameters such as hemoglobin level can be modified more easily than in animal models.

Estimation of respiration rate and sleeping position using a wearable accelerometer.

Wearable inertial sensors offer the possibility to monitor sleeping position and respiration rate during sleep, enabling a comfortable and low-cost method to remotely monitor patients. Novel methods to estimate respiration rate and position during sleep using accelerometer data are presented, with algorithm performance examined for two sensor locations, and accelerometer-derived respiration rate compared across sleeping positions. Eleven participants (9 male; aged: 47.82±14.14 years; BMI 30.9±5.27 kg/m2; AHI 5.77±4.18) undergoing a scheduled clinical polysomnography (PSG) wore a tri-axial accelerometer on their chest and upper abdomen. PSG cannula flow and position data were used as benchmark data for respiration rate (breaths per minute, bpm) and position. Sleeping position was classified using logistic regression, with features derived from filtered acceleration and orientation. Accelerometer-derived respiration rate was estimated for 30 s epochs using an adaptive peak detection algorithm which combined filtered acceleration and orientation data to identify individual breaths. Sensor-derived and PSG respiration rates were then compared. Mean absolute error (MAE) in respiration rate did not vary between sensor locations (abdomen: 1.67±0.37 bpm; chest: 1.89±0.53 bpm; p=0.52), while reduced MAE was observed when participants lay on their side (1.58±0.54 bpm) compared to supine (2.43±0.95 bpm), p<0.01. MAE was less than 2 bpm for 83.6% of all 30 s windows across all subjects. The position classifier distinguished supine and left/right with a ROC AUC of 0.87, and between left and right with a ROC AUC of 0.94. The proposed methods may enable a low-cost solution for in-home, long term sleeping posture and respiration monitoring.

Clinical evaluation of a new dispersive aortic cannula

Cerebral injury is a serious complication in open-heart surgery. Once it occurs, it causes significant disability and death. We developed a novel dispersive aortic cannula named the Stealth Flow cannula and used it as a standard aortic cannula in cardiopulmonary bypass. The aim of this study was to evaluate the efficiency of this aortic cannula. A total of 182 consecutive patients undergoing cardiac surgery using cardiopulmonary bypass were studied. The patients were divided into two groups: the Soft-Flow cannula group (n = 89) and the Stealth Flow cannula group (n = 93). Patients with a shaggy aortic arch were excluded from this study because the cannulae were inserted at the ascending aorta with a cannula tip directed toward the aortic root in these cases. Patients with multiple arterial perfusion sites were also excluded. Complications including early mortality, perioperative stroke, and intraoperative aortic injury were compared between the two groups. Age, operative procedure, cardiopulmonary bypass time, and the Japan SCORE were not significantly different between the groups. In comparisons between the Stealth Flow and Soft-Flow groups, the incidences of early mortality, perioperative stroke, intraoperative aortic dissection, and all complications were 1.08% versus 1.12% (p = 0.98), 1.1% versus 2.2% (p = 0.53), 0% versus 1.1% (p = 0.33), and 1.1% versus 3.4% (p = 0.29), respectively. The incidence of major cardiovascular events, including early death, perioperative stroke, and aortic dissection, was not different. The Stealth Flow cannula, which was designed based on our previous experimental study, contributed to reducing cerebral and aortic events as much as the Soft-Flow cannula in the present clinical study.

Prevalence of Continuous Pulse Oximetry Monitoring in Hospitalized Children With Bronchiolitis Not Requiring Supplemental Oxygen

US national guidelines discourage the use of continuous pulse oximetry monitoring in hospitalized children with bronchiolitis who do not require supplemental oxygen. Measure continuous pulse oximetry use in children with bronchiolitis. A multicenter cross-sectional study was performed in pediatric wards in 56 US and Canadian hospitals in the Pediatric Research in Inpatient Settings Network from December 1, 2018, through March 31, 2019. Participants included a convenience sample of patients aged 8 weeks through 23 months with bronchiolitis who were not receiving active supplemental oxygen administration. Patients with extreme prematurity, cyanotic congenital heart disease, pulmonary hypertension, home respiratory support, neuromuscular disease, immunodeficiency, or cancer were excluded. Hospitalization with bronchiolitis without active supplemental oxygen administration. The primary outcome, receipt of continuous pulse oximetry, was measured using direct observation. Continuous pulse oximetry use percentages were risk standardized using the following variables: nighttime (11 pm to 7 am), age combined with preterm birth, time after weaning from supplemental oxygen or flow, apnea or cyanosis during the present illness, neurologic impairment, and presence of an enteral feeding tube. The sample included 3612 patient observations in 33 freestanding children's hospitals, 14 children's hospitals within hospitals, and 9 community hospitals. In the sample, 59% were male, 56% were white, and 15% were black; 48% were aged 8 weeks through 5 months, 28% were aged 6 through 11 months, 16% were aged 12 through 17 months, and 9% were aged 18 through 23 months. The overall continuous pulse oximetry monitoring use percentage in these patients, none of whom were receiving any supplemental oxygen or nasal cannula flow, was 46% (95% CI, 40%-53%). Hospital-level unadjusted continuous pulse oximetry use ranged from 2% to 92%. After risk standardization, use ranged from 6% to 82%. Intraclass correlation coefficient suggested that 27% (95% CI, 19%-36%) of observed variation was attributable to unmeasured hospital-level factors. In a convenience sample of children hospitalized with bronchiolitis who were not receiving active supplemental oxygen administration, monitoring with continuous pulse oximetry was frequent and varied widely among hospitals. Because of the apparent absence of a guideline- or evidence-based indication for continuous monitoring in this population, this practice may represent overuse.

Transhepatic echocardiography: a novel approach for imaging in left ventricle assist device patients with difficult acoustic windows.

AimsA significant proportion of left ventricle assist device (LVAD) patients have very difficult transthoracic echocardiographic images. The aim of this study was to find an echocardiographic window which would provide better visualization of the heart in LVAD patients with limited acoustic windows.Methods and resultsBased on the anatomic relationships in LVAD patients, a right intercostal transhepatic approach was proposed. By using a computer simulator, we searched for the appropriate probe orientation. Further, 15 ambulatory LVAD patients (age 56 ± 15 years, 73% males) underwent two echocardiographic studies: one normal transthoracic echocardiography following the institutional protocol (Echo 1) and a second study which included the transhepatic approach (Echo 2). The two exams were performed by two different sonographers and the results validated by a third observer for agreement. The transhepatic intercostal window was feasible in all patients, with an image quality allowing good visualization of structures in 93%. Precise quantification of the left ventricular (LV) and right ventricular (RV) function was achieved more often in the Echo 2 (10 vs. 3 patients for LV, P = 0.03 and 14 vs. 8 patients for RV, P = 0.04). A significant difference existed also in the quantification of the LVAD inflow cannula flow by pulsed Doppler (11 patients in Echo 2 vs. 3 patients in Echo 1, P = 0.009).ConclusionThis is the first study describing a new echocardiographic window in LVAD patients. The transhepatic window may provide better quantification of left and RV dimensions and function and improvement in Doppler interrogation of the inflow cannula.

Confined jets in co-flow: effect of the flow rate ratio and lateral position of a return cannula on the flow dynamics

Co-axial tubes have been used to produce a co-flowing confined jet similar to that found in an Extracorporeal Membrane Oxygenation return cannula flow configuration. Particle Image Velocimetry was used to investigate the flow rate ratio between jet and co-flow as well as changes in flow characteristics due to cannula position. The flow was found to be dominated by three main structures: lateral flow entrainment, shear layer induced vortices and backflow along the wall. An increase in cannula flow rate amplified entrainment and recirculation, resulting in a decrease in length required to reach a fully developed flow. Changing cannula position relative the outer cylinder induced a significant reduction in recirculation zone as well as vortex formation on the side to which the cannula was tilted towards, whereas on the other side, the recirculating flow region was enhanced. Proper Orthogonal Decomposition demonstrated that the dominating structure found in the flow is the backflow, composing of several structures having different oscillation frequencies. The significance of the observed and measured flow structures is in enhancing mixing.

Aortic cannula orientation and flow impacts embolic trajectories: computational cardiopulmonary bypass.

Emboli events are associated with the aortic cannula insertion and final position in the ascending aorta. However, the impact of subtle changes in aortic cannula movement and flow influencing embolic transport throughout the aortic arch is not well understood. The present study evaluated the aortic cannula's outflow and orientation effect on emboli entering the aortic branch arteries. A simplified aortic computational model was anteriorly cannulated in the distal ascending aorta with a 21-French straight aortic cannula, and two orientations were analysed by injecting gaseous and solid emboli at pump flows 2, 3 and 5 L/minute. The first aortic cannula orientation (forward flow cannula) was directed towards the lesser curvature. The second aortic cannula orientation (rear flow cannula) was tilted slightly backwards by 15°, providing flow in the retrograde direction. Forward flow cannula produced a primary arch flow, whereas rear flow cannula produced a secondary arch flow resulting in four times longer emboli arch resident times than forward flow cannula. The rear flow cannula had the highest percentage of gaseous emboli entering the brachiocephalic artery of 8%, 12% and 36% (at 2, 3 and 5 L/minute, respectively). Rear flow cannula provided a positive aortic branch arterial flow at all pump flows, whereas at forward flow cannula, the brachiocephalic artery experienced retrograde flows of -1.0% (3 L/minute) and -4.0% (5 L/minute), with the left common carotid -0.23% (5 L/minute). No significant number of solid emboli entered the aortic branch arteries. This numerical study illustrated distinct trajectory behaviours between gaseous and solid emboli where slight changes in aortic cannula orientation influenced idealised emboli direction with higher pump flows magnifying the effects.