The effectiveness of high-flow nasal cannula during sedated digestive endoscopy: a systematic review and meta-analysis.

BACKGROUND: Studies evaluating the role of high-flow nasal cannula (HFNC) in sedated digestive endoscopy have reported conflicting results. This meta-analysis evaluates the effectiveness of HFNC in patients undergoing digestive endoscopy procedures under sedation. METHODS: PubMed, Medline, EMBASE, Cochrane Central Register of Controlled Trials and Web of Science, were searched from inception to 31 July 2021. Only randomized clinical trials comparing HFNC with standard nasal cannula oxygen (SNC) during sedated digestive endoscopy were included. The incidence of hypoxemia was the primary outcome, and the secondary outcome was the percentage of patients who needed airway interventions. RESULTS: Seven studies that enrolled 2998 patients were included. When compared to SNC, HFNC was associated with a significant reduction in hypoxemia incidence (OR 0.24, 95% CI 0.09 to 0.64) and airway intervention requirements (OR 0.15, 95% CI 0.03 to 0.69), with both high heterogeneity (I2 = 81% and 94%). In subgroup analysis, when hypoxemia was defined as pulse oxygen saturation (SpO2) < 90%, low risk of hypoxemia subjects who received HFNC were associated with a significant reduction in hypoxemia incidence (OR 0.02, 95% CI 0.00 to 0.07; heterogeneity I2 = 39%) and airway intervention requirements (OR 0.02, 95% CI 0.01 to 0.04; heterogeneity I2 = 15%). However, in the high risk of hypoxemia subjects, there were no significant differences between the two oxygen administration techniques in both primary (OR 0.81, 95% CI 0.36 to 1.78; heterogeneity I2 = 0%) and secondary outcomes (OR 0.85, 95% CI 0.46 to 1.59; heterogeneity I2 = 0%). CONCLUSIONS: Compared to SNC, HFNC not only reduce the incidence of hypoxemia but also reduce the requirements for airway interventions during sedated digestive endoscopy procedures, especially in patients at low risk for hypoxemia. In high risk of hypoxemia patients, there were no significant differences between the two oxygen administration techniques. Trial registration PROSPERO International prospective register of systematic reviews on 28 July 2021, registration no. CRD42021264556.

Noninvasive ventilation and high-flow nasal cannula in patients with acute hypoxemic respiratory failure by covid-19: A retrospective study of the feasibility, safety and outcomes.

BACKGROUND: Noninvasive ventilation (NIV) and High-flow nasal cannula (HFNC) are the main forms of treatment for acute respiratory failure. This study aimed to evaluate the effect, safety, and applicability of the NIV and HFNC in patients with acute hypoxemic respiratory failure (AHRF) caused by COVID-19. METHODS: In this retrospective study, we monitored the effect of NIV and HFNC on the SpO2 and respiratory rate before, during, and after treatment, length of stay, rates of endotracheal intubation, and mortality in patients with AHRF caused by COVID-19. Additionally, data regarding RT-PCR from physiotherapists who were directly involved in assisting COVID-19 patients and non-COVID-19. RESULTS: 62.2 % of patients were treated with HFNC. ROX index increased during and after NIV and HFNC treatment (P < 0.05). SpO2 increased during NIV treatment (P < 0.05), but was not maintained after treatment (P = 0.17). In addition, there was no difference in the respiratory rate during or after the NIV (P = 0.95) or HFNC (P = 0.60) treatment. The mortality rate was 35.7 % for NIV vs 21.4 % for HFNC (P = 0.45), while the total endotracheal intubation rate was 57.1 % for NIV vs 69.6 % for HFNC (P = 0.49). Two adverse events occurred during treatment with NIV and eight occurred during treatment with HFNC. There was no difference in the physiotherapists who tested positive for SARS-COV-2 directly involved in assisting COVID-19 patients and non-COVID-19 ones (P = 0.81). CONCLUSION: The application of NIV and HFNC in the critical care unit is feasible and associated with favorable outcomes. In addition, there was no increase in the infection of physiotherapists with SARS-CoV-2.

Optimizing cerebral perfusion and hemodynamics during cardiopulmonary bypass through cannula design combining in silico, in vitro and in vivo input.

Cardiopulmonary bypass (CPB) is a standard technique for cardiac surgery, but comes with the risk of severe neurological complications (e.g. stroke) caused by embolisms and/or reduced cerebral perfusion. We report on an aortic cannula prototype design (optiCAN) with helical outflow and jet-splitting dispersion tip that could reduce the risk of embolic events and restores cerebral perfusion to 97.5% of physiological flow during CPB in vivo, whereas a commercial curved-tip cannula yields 74.6%. In further in vitro comparison, pressure loss and hemolysis parameters of optiCAN remain unaffected. Results are reproducibly confirmed in silico for an exemplary human aortic anatomy via computational fluid dynamics (CFD) simulations. Based on CFD simulations, we firstly show that optiCAN design improves aortic root washout, which reduces the risk of thromboembolism. Secondly, we identify regions of the aortic intima with increased risk of plaque release by correlating areas of enhanced plaque growth and high wall shear stresses (WSS). From this we propose another easy-to-manufacture cannula design (opti2CAN) that decreases areas burdened by high WSS, while preserving physiological cerebral flow and favorable hemodynamics. With this novel cannula design, we propose a cannulation option to reduce neurological complications and the prevalence of stroke in high-risk patients after CPB.

Comparison of Actual Performance in the Flow and Fraction of Inspired O2 among Different High-Flow Nasal Cannula Devices: A Bench Study.

Background: High-flow nasal cannula (HFNC) oxygen therapy has been recommended for use in coronavirus disease 2019 (COVID-19) patients with acute respiratory failure and many other clinical conditions. HFNC devices produced by different manufacturers may have varied performance. Whether there is a difference in these devices and the extent of the differences in performance remain unknown. Methods: Four HFNC devices (AIRVO 2, TNI softFlow 50, HUMID-BH, and OH-70C) and a ventilator with an HFNC module (bellavista 1000) were evaluated. The flow was set at 20, 25, 30, 35, 40, 45, 50, 60, 70, and 80 L/min, and the FiO2 was set at 21%, 26%, 30%, 35%, 40%, 45%, 50%, 60%, 70%, 80%, and 90%. Then, one side of the cannulas was clipped to simulate the compression, bending, or blocking of the nasal cannulas. The flow and FiO2 of the delivered gas were recorded and compared among settings and devices. Results: The actual-flow and actual-FiO2 delivered by different settings and devices varied. AIRVO 2 had superior performance in flow and FiO2 accuracy. bellavista 1000 and OH-70C had good performance in the accuracy of actual-flows and actual-FiO2, respectively. bellavista 1000 and HUMID-BH had a larger flow range from 10 to 80 L/min, but only bellavista 1000 could provide a stable flow with an excessive resistance up to 60 L/min. TNI softFlow 50 had the best flow compensation and could provide sufficient flow with excessive resistance at 20-50 L/min. Conclusions: The variation in flow, FiO2 settings, and devices could influence the actual-flow and actual-FiO2 delivered. AIRVO 2 and OH-70C showed better FiO2 accuracy. TNI softFlow 50, bellavista 1000, and HUMID-BH could lower the risk of insufficient flow support due to accidental compression or blocking of the cannulas. In addition, ventilators with HFNC modules provided comparable flow and FiO2 and could be an alternative to standalone HFNC devices.

Analysis of experience of the use of plastic cannulas in Spanish haemodialysis units.

INTRODUCTION: Plastic cannulas (PC) have shown efficacy in haemodialysis (HD) and are presented as a positive innovation for patients and vascular access survival. OBJECTIVE: To analyse Spanish HD nurses' experience of using PC. DESIGN: Cross-sectional observational study. METHODS: An ad hoc questionnaire was administered on nurses' experience of PC use. RESULTS: A total of 163 Spanish HD nurses were surveyed, of whom 42.3% had PC in their workplace and 50.9% had used them. In all, 55.8% had received training and 77.9% wished to receive more training. These needles were significantly more available in public institutions than in private centres (p < 0.001). There was no significant difference between years of experience and having received training (p = 0.915). There was a moderate-strong correlation (ρ = 0.659) between greater professional satisfaction with the product and greater patient satisfaction (p < 0.001). The nurses would make a median of two [P25 , 1; P75 , 3] modifications in the product design. The characteristics of the PC were rated positively by 55.8% and negatively by 10.3%. CONCLUSIONS: A substantial proportion of the nurses surveyed did not use PC and had not received training in their use. Respondents reported that PC could be improved and a small percentage perceived them negatively. IMPLICATIONS FOR PRACTICE: Based on the evidence presented and available, if we manage to integrate this knowledge and work on the continuum of achieving excellence, we will continue to grow as a profession and provide higher quality care.

High flow nasal therapy versus noninvasive ventilation as initial ventilatory strategy in COPD exacerbation: a multicenter non-inferiority randomized trial.

BACKGROUND: The efficacy and safety of high flow nasal therapy (HFNT) in patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease (AECOPD) are unclear. Our aim was to evaluate the short-term effect of HFNT versus NIV in patients with mild-to-moderate AECOPD, with the hypothesis that HFNT is non-inferior to NIV on CO2 clearance after 2 h of treatment. METHODS: We performed a multicenter, non-inferiority randomized trial comparing HFNT and noninvasive ventilation (NIV) in nine centers in Italy. Patients were eligible if presented with mild-to-moderate AECOPD (arterial pH 7.25-7.35, PaCO2 ≥ 55 mmHg before ventilator support). Primary endpoint was the mean difference of PaCO2 from baseline to 2 h (non-inferiority margin 10 mmHg) in the per-protocol analysis. Main secondary endpoints were non-inferiority of HFNT to NIV in reducing PaCO2 at 6 h in the per-protocol and intention-to-treat analysis and rate of treatment changes. RESULTS: Seventy-nine patients were analyzed (80 patients randomized). Mean differences for PaCO2 reduction from baseline to 2 h were - 6.8 mmHg (± 8.7) in the HFNT and - 9.5 mmHg (± 8.5) in the NIV group (p = 0.404). By 6 h, 32% of patients (13 out of 40) in the HFNT group switched to NIV and one to invasive ventilation. HFNT was statistically non-inferior to NIV since the 95% confidence interval (CI) upper boundary of absolute difference in mean PaCO2 reduction did not reach the non-inferiority margin of 10 mmHg (absolute difference 2.7 mmHg; 1-sided 95% CI 6.1; p = 0.0003). Both treatments had a significant effect on PaCO2 reductions over time, and trends were similar between groups. Similar results were found in both per-protocol at 6 h and intention-to-treat analysis. CONCLUSIONS: HFNT was statistically non-inferior to NIV as initial ventilatory support in decreasing PaCO2 after 2 h of treatment in patients with mild-to-moderate AECOPD, considering a non-inferiority margin of 10 mmHg. However, 32% of patients receiving HFNT required NIV by 6 h. Further trials with superiority design should evaluate efficacy toward stronger patient-related outcomes and safety of HFNT in AECOPD. TRIAL REGISTRATION: The study was prospectively registered on December 12, 2017, in ClinicalTrials.gov (NCT03370666).

The safety and effectiveness of heated humidified high-flow nasal cannula as an initial ventilation method in the treatment of neonatal respiratory distress syndrome: A protocol for systematic review and meta-analysis.

BACKGROUND: This study uses a method of systematic evaluation to evaluate the safety and effectiveness of heated humidified high-flow nasal cannula (HHHFNC) as an initial ventilation method in the treatment of neonatal respiratory distress syndrome (NRDS) scientifically. In the field of evidence-based medicine, this study provides a theoretical reference and basis for choosing appropriate initial non-invasive ventilation methods in the treatment of NRDS, thereby providing assistance for clinical treatment. METHODS: The main electronic network databases were searched by computer, including 4 Chinese databases: CNKI, WangFang Data, CQVIP, SinoMed and 3 English databases: PubMed, The Cochrane Library and EMBASE, the time range of retrieval from the beginning of each database to September 1, 2020. The content involves all the published randomized controlled trials on the effectiveness of HHHFNC compared with NCPAP as an initial ventilation method in the treatment of NRDS. Using a search method that combines medical subject words and free words. Based on the Cochrane risk bias assessment tool, 2 researchers independently screen the literature, and then extract the data we needed in the literature, and cross-check. If it is difficult to decide whether to include literature, then turning to a third researcher for help and making a final decision after discussion, and using RevMan 5.3 and STATA 13.0 to analyze the relative data. RESULTS: Based on the method of meta-analysis, this study analyzes the pre-determined outcome indicators through scientific statistical analysis, and compares the effectiveness and safety of HHHFNC compared with NCPAP as an initial ventilation method in the treatment of NRDS. All results will be published in peer-reviewed high-quality professional academic journals. CONCLUSION: Based on evidence-based medicine, this study will obtain the establishing evidence of comparison that the clinical effectiveness and safety of HHHFNC compared with NCPAP as an initial ventilation method in the treatment of NRDS through the existing data and data, which provides the evidence support of evidence-based medicine in the treatment of NRDS. OSF REGISTRATION NUMBER: September 17, 2020. osf.io/f6at4 (https://osf.io/f6at4).

Use of Noninvasive Ventilation and High-Flow Nasal Cannulae Therapy for Infants and Children with Acute Respiratory Distress Outside of Paediatric Intensive Care: A review article.

Noninvasive ventilation (NIV) and high-flow nasal cannulae therapy (HFNCT) are first-line methods of treatment for children presenting with acute respiratory distress, with paediatric intensive care units (PICUs) providing an ideal environment for subsequent treatment monitoring. However, the availability of step-down units, where NIV and HFNCT can be safely utilised, has reduced the need for such patients to be admitted to PICUs, thereby leading to the better overall utilisation of critical care resources. In addition, NIV and HFNCT can also be used during transport instead of invasive ventilation, thus avoiding the complications associated with the latter approach. This review article examines the safety and applicability of these respiratory support approaches outside of paediatric intensive care as well as various factors associated with treatment success or failure.

A narrative review on trans-nasal pulmonary aerosol delivery.

The use of trans-nasal pulmonary aerosol delivery via high-flow nasal cannula (HFNC) has expanded in recent years. However, various factors influencing aerosol delivery in this setting have not been precisely defined, and no consensus has emerged regarding the optimal techniques for aerosol delivery with HFNC. Based on a comprehensive literature search, we reviewed studies that assessed trans-nasal pulmonary aerosol delivery with HFNC by in vitro experiments, and in vivo, by radiolabeled, pharmacokinetic and pharmacodynamic studies. In these investigations, the type of nebulizer employed and its placement, carrier gas, the relationship between gas flow and patient's inspiratory flow, aerosol delivery strategies (intermittent unit dose vs continuous administration by infusion pump), and open vs closed mouth breathing influenced aerosol delivery. The objective of this review was to provide rational recommendations for optimizing aerosol delivery with HFNC in various clinical settings.

Pressure and flow properties of dual-lumen cannulae for extracorporeal membrane oxygenation.

INTRODUCTION: In the last decade, dual-lumen cannulae have been increasingly applied in patients undergoing extracorporeal life support. Well-performing vascular access is crucial for efficient extracorporeal membrane oxygenation support; thus, guidance for proper cannulae size is required. Pressure-flow charts provided by manufacturers are often based on tests performed using water, rarely blood. However, blood is a shear-thinning and viscoelastic fluid characterized by different flow properties than water. METHODS: We performed a study evaluating pressure-flow curves during standardized conditions using human whole blood in two commonly available dual-lumen cannulae used in neonates, pediatric, and adult patients. Results were merged and compared with the manufacturer's corresponding curves obtained from the public domain. RESULTS: The results showed that using blood as compared with water predominantly influenced drainage flow. A 10-80% higher pressure-drop was needed to obtain same drainage flow (hematocrit of 26%) compared with manufacturer's water charts in 13-31 Fr bi-caval dual-lumen cannulae. The same net difference was found in cavo-atrial cannulae (16-32 Fr), where a lower drainage pressure was required (Hct of 26%) compared with the manufacturer's test using blood with an Hct of 33%. Return pressure-flow data were similar, independent whether pumping blood or water, to the data reported by manufacturers. CONCLUSION: Non-standardized testing of pressure-flow properties of extracorporeal membrane oxygenation dual-lumen cannulae prevents an adequate prediction of pressure-flow results when these cannulae are used in patients. Properties of dual-lumen cannulae may vary between sizes within same cannula family, in particular concerning the drainage flow.

Comparison of preoxygenation with a high-flow nasal cannula and a simple mask before intubation during induction of general anesthesia in patients undergoing head and neck surgery: Study protocol clinical trial (SPIRIT Compliant).

BACKGROUND: To assess the arterial oxygen partial pressure (PaO2) at defined time points during preoxygenation and to compare high-flow heated humidified nasal oxygenation with standard preoxygenation using oxygen insufflation via a facemask for at least 5 minutes, before intubation during induction of general anesthesia. METHODS: This randomized, single-blinded, prospective study will be conducted in patients undergoing head and neck surgery. After standard monitoring, the artery catheter at the radial artery or dorsalis pedis artery will be placed and arterial blood gas analysis (ABGA) for baseline values will be performed simultaneously. Each group will be subjected to 1 of 2 preoxygenation methods (high-flow nasal cannula or simple facemask) for 5 minutes, and ABGA will be performed twice. After confirming intubation, we will start mechanical ventilation and check the vital signs and perform the final ABGA. DISCUSSION: This trial aims to examine the trajectory of PaO2 levels during the whole preoxygenation procedure and after intubation. We hypothesize that preoxygenation with the high-flow nasal cannula will be superior to that with the face mask. STUDY REGISTRATION: This trial was registered with the Clinical Trial Registry (NCT03896906; ClinicalTrials.gov).

Effect of postextubation high-flow nasal cannula therapy on lung recruitment and overdistension in high-risk patient.

BACKGROUND: Postextubation high-flow nasal cannula (HFNC) is used as a support therapy in high-risk patients in ICU. This study aimed to determine the effects of HFNC therapy on lung recruitment and overdistension assessed by electrical impedance tomography (EIT). METHODS: Twenty-four patients who received HFNC within 24 h after extubation were prospectively enrolled in this study. EIT was used to monitor regional lung ventilation distributions at baseline (conventional oxygen therapy) and three flow rate levels of HFNC therapy (20, 40, and 60 L/min). Change of end-expiratory lung impedance (ΔEELI), regional recruitment (recruited-pixels) and overdistension (overdistended-pixels), and lung strain change were determined by EIT. EIT images were equally divided into four ventral-to-dorsal horizontal regions of interest (ROIs 1, 2, 3, and 4). "Overdistension-by HFNC" due to HFNC is defined as an increase of overdistened-pixels > 10 than baseline. Patients were divided into two groups: (1) high potential of recruitment (HPR), recruited-pixels > 10 pixels at 60 L/min than baseline, and (2) low potential of recruitment (LPR), recruited-pixels < 10 pixels at 60 L/min than baseline. RESULTS: When the flow rate gradually increased from baseline to 60 L/min, a significant and consistent increasing trend of global ΔEELI (%) (p < 0.0001), recruited-pixels (p < 0.001), and overdistended-pixels (p = 0.101) was observed. Moreover, the increase of ΔEELI was mainly distributed in ROI2 (p = 0.001) and ROI3 (p < 0.0001). The HPR group (13/24 patients) had significantly higher recruited-pixels than the LPR group (11/24 patients) at 20, 40, and 60 L/min. There were no significant differences in PaO2/FiO2, ΔEELI (%), and overdistention pixels between the two groups. The HPR group had 13 patients in which no one had "overdistension-by HFNC", and the LPR group had 11 patients in which 4 patients had "overdistension-by HFNC" (0/13 vs. 4/11, p = 0.017). CONCLUSIONS: Using EIT could identify diverse effects of HFNC on lung regional ventilation in postextubation situations. Further study is required to validate using "HFNC effect" based on lung recruitment and overdistension by EIT in clinical practice. TRIAL REGISTRATION: The study was retrospectively registered at www.clinicaltrials.gov (no. NCT04245241).

Pressure Injuries of the Nose and Columella in Preterm Neonates Receiving Noninvasive Ventilation via a Specialized Nasal Cannula: A Retrospective Comparison Cohort Study.

PURPOSE: The aims of this study were to measure the incidence and severity of nasal septum injury in premature infants receiving continuous positive airway pressure (CPAP) via a noninvasive thin-walled cannula, and to evaluate the effect of a polyvinyl chloride foam barrier dressing in reducing these injuries. DESIGN: Retrospective chart review, comparison cohort study. SUBJECTS AND SETTING: The sample comprised 235 neonates with a gestational age of 28 weeks or younger. Their mean gestational age was 26 weeks (range 22-28 weeks) and mean birth weight was 840 g (range 430-1320 g). The study setting was a level 4, regional neonatal intensive care unit housed in a 200-bed freestanding children's hospital located in the Northeastern United States. METHODS: Data were collected during 3 periods. During all 3 data collection periods, we used a soft, thin-walled nasal cannula, with a relatively short, binasal prong interphase and small diameter tubing connected to a ventilator circuit capable of transmitting positive airway pressure in neonates. During data collection periods 1 and 3, we used a polyvinyl foam barrier dressing as a preventive intervention against nasal skin damage; specifically, we placed a precut barrier on the prongs to protect the nasal skin. One side of the barrier foam has an adhesive surface, which was placed against the prongs. Study period 2 differed; during this period neonates were treated with the nasal cannula without the foam barrier based on manufacturer experience suggesting the foam barrier is not needed for prevention of skin damage. Pressure injuries (PIs) that occurred during each study period were staged according to National Pressure Ulcer Advisory Panel definitions. RESULTS: Eighty neonates were evaluated during study period 1 (thin-walled nasal cannula plus foam barrier). We evaluated 27 neonates during period 2 (thin-walled nasal cannula and no foam barrier) and 128 were evaluated during study period 3 (thin-walled nasal cannula plus foam barrier). Six neonates (7%) developed PIs during period 1, and 2 (1.5%) developed during study period 3. All were stage 1 and 2 PIs, no full-thickness injuries, also referred to as columella necrosis developed during use of the thin-walled nasal cannula in combination with the foam barrier dressings. In contrast, 13 PIs (48%) of neonates managed during data collection period 2 (thin-walled nasal cannula with no foam barrier) developed PI, and 40% experienced stage 3 PI or columella necrosis. This difference reflects a 6-fold increase in nasal injury occurred when nasal continuous positive airway pressure (NCPAP) was administered without use of the protective barrier dressing. CONCLUSION: We found clinically relevant difference in the occurrences of nasal PI in neonates managed with NCPAP; occurrences of stage 3 PI were 6-fold higher when a thin-walled cannula was used without a protective foam barrier dressing.

Efficacy and safety of early prone positioning combined with HFNC or NIV in moderate to severe ARDS: a multi-center prospective cohort study.

BACKGROUND: Previous studies suggest that prone positioning (PP) can increase PaO2/FiO2 and reduce mortality in moderate to severe acute respiratory distress syndrome (ARDS). The aim of our study was to determine whether the early use of PP combined with non-invasive ventilation (NIV) or high-flow nasal cannula (HFNC) can avoid the need for intubation in moderate to severe ARDS patients. METHODS: This prospective observational cohort study was performed in two teaching hospitals. Non-intubated moderate to severe ARDS patients were included and were placed in PP with NIV or with HFNC. The efficacy in improving oxygenation with four support methods-HFNC, HFNC+PP, NIV, NIV+PP-were evaluated by blood gas analysis. The primary outcome was the rate of intubation. RESULTS: Between January 2018 and April 2019, 20 ARDS patients were enrolled. The main causes of ARDS were pneumonia due to influenza (9 cases, 45%) and other viruses (2 cases, 10%). Ten cases were moderate ARDS and 10 cases were severe. Eleven patients avoided intubation (success group), and 9 patients were intubated (failure group). All 7 patients with a PaO2/FiO2 < 100 mmHg on NIV required intubation. PaO2/FiO2 in HFNC+PP were significantly higher in the success group than in the failure group (125 ± 41 mmHg vs 119 ± 19 mmHg, P = 0.043). PaO2/FiO2 demonstrated an upward trend in patients with all four support strategies: HFNC < HFNC+PP ≤ NIV < NIV+PP. The average duration for PP was 2 h twice daily. CONCLUSIONS: Early application of PP with HFNC, especially in patients with moderate ARDS and baseline SpO2 > 95%, may help avoid intubation. The PP was well tolerated, and the efficacy on PaO2/FiO2 of the four support strategies was HFNC < HFNC+PP ≤ NIV < NIV+PP. Severe ARDS patients were not appropriate candidates for HFNC/NIV+PP. TRIAL REGISTRATION: ChiCTR, ChiCTR1900023564. Registered 1 June 2019 (retrospectively registered).

Effect of blood viscosity on the performance of virtually wall-less venous cannulas.

AIM: This study was designed to quantify the influence of blood as test medium compared to water in cannula bench performance assessment. METHODS: An in vitro circuit was set-up with silicone tubing between two reservoirs. The test medium was pumped from the lower reservoir by centrifugal pump to the upper reservoir. The test-cannula was inserted in a silicone tube connected between the lower reservoir and the centrifugal pump. Flow rate and pump inlet-pressure were measured for wall-less versus thin-wall cannula using a centrifugal pump in a dynamic bench-test for an afterload of 40-60 mmHg using two media: blood 10 g/dL and 5.6 g/dL and water 0 g/dL. RESULTS: The wall-less cannula showed significantly higher flows rates as compared to the thin-wall cannula (control), with both hemoglobin concentrations and water. Indeed, for a target volume of 200-250 mL of blood (Hg 10 g/dL) in the upper reservoir, the cannula outlet pressure (P) was -14 ± 14 mmHg versus -18 ± 11 mmHg for the wall-less and control respectively; the cannula outlet flow rate (Q) was 3.91 ± 0.41 versus 3.67 ± 0.45 L/min, respectively. At the same target volume but with a Hg of 5.7 g/dL, P was -16 ± 12 mmHg versus -19 ± 12 mmHg and Q was 4 ± 0.1 versus 4 ± 0.4 L/min for the wall-less cannula and control respectively. Likewise, P and Q values with water were -1 mmHg versus -0.67 ± 0.58 mmHg and 4.17 ± 0.45 L/min versus 4.08 ± 0.47 L/min for the wall-less and control respectively. CONCLUSION: Walls-less cannula showed 5.6% less pump inlet-pressure differences calculated between blood and water, as compared to that of thin-wall cannula (-21 times). Flow differences were 6% and 10% for the walls-less and thin-wall cannula respectively. We conclude that testing the cannula performance with water is a good scenario and can overestimate the flow by a 10%. However, superiority for wall-less is preserved with both water and blood.

Deep hypothermic extracorporeal membrane oxygenation cannula exchange in a child with necrotic pneumonia.

Necrotizing pneumonia can lead to respiratory insufficiency in previously healthy children. Extracorporeal membrane oxygenation can be used for hemodynamic salvage and subsequent lung rest awaiting recovery. We present a case of a child initially placed on veno-arterial extracorporeal membrane oxygenation and converted to veno-venous extracorporeal membrane oxygenation. This was done under deep hypothermia in the operating theater.

Hemodynamics of neonatal double lumen cannula malposition.

OBJECTIVE: Malposition of dual lumen cannula is a frequent and challenging complication in neonates and plays a significant role in shaping the in vitro device hemodynamics. This study aims to analyze the effect of the dual lumen cannula malposition on right-atrial hemodynamics in neonatal patients using an experimentally validated computational fluid dynamics model. METHODS: A computer model was developed for clinically approved dual lumen cannula (13Fr Origen Biomedical, Austin, Texas, USA) oriented inside the atrium of a 3-kg neonate with normal venous return. Atrial hemodynamics and dual lumen cannula malposition were systematically simulated for two rotations (antero-atrial and atrio-septal) and four translations (two intravascular movements along inferior vena cava and two dislodged configurations in the atrium). A multi-domain compartmentalized mesh was prepared to allow the site-specific evaluation of important hemodynamic parameters. Transport of each blood stream, blood damage levels, and recirculation times are quantified and compared to dual lumen cannula in proper position. RESULTS: High recirculation levels (39 ± 4%) in malpositioned cases resulted in poor oxygen saturation where maximum recirculation of up to 42% was observed. Apparently, Origen dual lumen cannula showed poor inferior vena cava blood-capturing efficiency (48 ± 8%) but high superior vena cava blood-capturing efficiency (86 ± 10%). Dual lumen cannula malposition resulted in corresponding changes in residence time (1.7 ± 0.5 seconds through the tricuspid). No significant differences in blood damage were observed among the simulated cases compared to normal orientation. Compared to the correct dual lumen cannula position, both rotational and translational displacements of the dual lumen cannula resulted in significant hemodynamic differences. CONCLUSION: Rotational or translational movement of dual lumen cannula is the determining factor for atrial hemodynamics, venous capturing efficiency, blood residence time, and oxygenated blood delivery. Results obtained through computational fluid dynamics methodology can provide valuable foresight in assessing the performance of the dual lumen cannula in patient-specific configurations.

Peripheral cannulae selection for veno-arterial extracorporeal life support: a paradox.

Explosive penetration of veno-arterial extracorporeal life support in everyday practice has drawn awareness to complications of peripheral cannulation, resulting in recommendations to use smaller size cannulae. However, using smaller cannulae may limit the effectiveness of extracorporeal support and thereby the specific needs of the patient. Selection of proper size cannulae may therefore pose a dilemma, especially since pressure-flow characteristics at different hematocrits are lacking. This study evaluates the precision of cannula pressure drop prediction with increase of fluid viscosity from water flow-pressure charts by M-number, dynamic similarity law, and via fitted parabolic equation. Thirteen commercially available peripheral cannulae were used in this in vitro study. Pressure drop and flow were recorded using water and a water-glycerol solution as a surrogate for blood, at ambient temperature. Subsequently, pressure-flow curves were modeled with increased fluid viscosity (0.0031 N s m-2), and then compared by M-number, dynamic similarity law, and fitted parabolic equation. The agreement of predicted and measured values were significantly higher when the M-number (concordance correlation = 0.948), and the dynamic similarity law method (concordance correlation = 0.947) was used in comparison to the fitted parabolic equation (concordance correlation = 0.898, p < 0.01). The M-number and dynamic similarity based model allow for reliable prediction of peripheral cannula pressure drop with changes of fluid viscosity and could therefore aid in well-thought-out selection of cannulae for extracorporeal life support.