This paper reports the development of microfluidic oxygenator (MFO) units designed for a lung assist device (LAD) for newborn infants. This device will be connected to the umbilical vessels like the natural placenta and provide gas exchange. The extracorporeal blood flow is only driven by the pressure difference between the umbilical artery and vein without the use of external pumps. The LAD is designed for use in ambient air (~21% of 760 mmHg). The main focus of this paper is the presentation of the development of the MFO units testing various membrane materials with human blood to enhance gas exchange and in the design of fluidic inlets to lower the pressure drop across the oxygenator. Four different membranes, including thin film PDMS, porous PDMS, and two different pore size porous polycarbonate membranes are compared in this study. Among them, the microfluidic oxygenator with porous PDMS membrane has the highest gas exchange rate of 1.46 μL min(-1) cm(2) for oxygen and 5.27 μL min(-1) cm(2) for carbon dioxide and performs better than a commercial hollow fiber-based oxygenator by 367 and 233%, respectively. A new tapered inlet configuration was designed to reduce the pressure drop across the oxygenator and showed a further 57% improvement over the traditional perpendicular inlet configuration.

A miniaturized oxygenator device that is perfused like an artificial placenta via the umbilical vessels may have significant potential to save the lives of newborns with respiratory insufficiency. Recently we presented the concept of an integrated modular lung assist device (LAD) that consists of stacked microfluidic single oxygenator units (SOUs) and demonstrated the technical details and operation of SOU prototypes. In this article, we present a LAD prototype that is designed to accommodate the different needs of term and preterm infants by permitting changing of the number of parallel-stacked microfluidic SOUs according to the actual body weight. The SOUs are made of polydimethylsiloxane, arranged in parallel, and connected though 3D-printed polymeric interconnects to form the LAD. The flow characteristics and the gas exchange properties were tested in vitro using human blood. We found that the pressure drop of the LAD increased linearly with flow rate. Gas exchange rates of 2.4-3.8 μL/min/cm(2) (0.3-0.5 mL/kg/min) and 6.4-10.1 μL/min/cm(2) (0.8-1.3 mL/kg/min) for O2 and CO2 , respectively, were achieved. We also investigated protein adsorption to provide preliminary information on the need for application of anticoagulant coating of LAD materials. Albumin adsorption, as measured by gold staining, showed that surface uptake was evenly distributed and occurred at the monolayer level (>0.2 μg/cm(2) ). Finally, we also tested the LAD under in vivo conditions using a newborn piglet model (body weight 1.65-2.0 kg). First, the effect of an arteriovenous bypass via a carotid artery-to-jugular vein shortcut on heart rate and blood pressure was investigated. Heart rate and mean arterial blood pressure remained stable for extracorporeal flow rates of up to 61 mL/kg/min (101 mL/min). Next, the LAD was connected to umbilical vessels (maximum flow rate of 24 mL/min [10.4 mL/kg/min]), and O2 gas exchange was measured under hypoxic conditions (Fi O2  = 0.15) and was found to be 3.0 μL/min/cm(2) . These results are encouraging and support the feasibility of an artificial placental design for an LAD.

BackgroundGoal-directed therapy guidelines for pediatric septic shock resuscitation recommend fluid delivery at speeds in excess of that possible through use of regular fluid infusion pumps. In our experience, syringes are commonly used by health care providers (HCPs) to achieve rapid fluid resuscitation in a pediatric fluid resuscitation scenario. At present, it is unclear which syringe size health care providers should use when performing fluid resuscitation to achieve maximal fluid resuscitation efficiency. The objective of this study was therefore to determine if an optimal syringe size exists for conducting manual pediatric fluid resuscitation.MethodsThis 48-participant parallel group randomized controlled trial included 4 study arms (10, 20, 30, 60 mL syringe size groups). Eligible participants were HCPs from McMaster Children’s Hospital, Hamilton, Canada blinded to the purpose of the trial. Consenting participants were randomized using a third party technique. Following a standardization procedure, participants administered 900 mL (60 mL/kg) of isotonic saline to a simulated 15 kg child using prefilled provided syringes of the allocated size in rapid sequence. Primary outcome was total time to administer the 900 mL and this data was collected through video review by two blinded outcome assessors. Sample size was predetermined based upon a primary outcome analysis using one-way ANOVA.Results12 participants were randomized to each group (n=48) and all completed trial protocol to analysis. Analysis was conducted according to intention to treat principles. A significant difference in fluid resuscitation time (in seconds) was found between syringe size group means: 10 mL, 563s [95% CI 521; 606]; 20 mL, 506s [95% CI 64; 548]; 30 mL, 454s [95% CI 412; 596]; 60 mL, 455s [95% CI 413; 497] (p<0.001).ConclusionsThe syringe size used when performing manual pediatric fluid resuscitation has a significant impact on fluid resuscitation speed, in a setting where fluid filled syringes are continuously available. Greatest efficiency was achieved with 30 or 60 mL syringes.Trial registrationClinicalTrials.gov, NCT01494116

BackgroundInvestigators conduct survey studies for a variety of reasons. Poor participant response rates are common, however, and may limit the generalizability and utility of results. The objective of this study was to determine whether direct approach with a tablet device enhances survey study participant response rate and to assess participants’ experiences with this mode of survey administration.FindingsAn interventional study nested within a single center survey study was conducted at McMaster Children’s Hospital. The primary outcome was the ability to achieve of a survey study response rate of 70% or greater. Eligible participants received 3 email invitations (Week 0, 2, 4) to complete a web-based (Survey Monkey) survey. The study protocol included plans for a two-week follow-up phase (Phase 2) where non-responders were approached by a research assistant and invited to complete an iPad-based version of the survey. The Phase 1 response rate was 48.7% (56/115). Phase 2 effectively recruited reluctant responders, increasing the overall response rate to 72.2% (83/115). On a 7-point Likert scale, reluctant responders highly rated their enjoyment (mean 6.0, sd 0.83 [95% CI: 5.7-6.3]) and ease of use (mean 6.7, sd 0.47 [95% CI: 6.5-6.9]) completing the survey using the iPad. Reasons endorsed for Phase 2 participation included: direct approach (81%), immediate survey access (62%), and the novelty of completing a tablet-based survey (54%). Most reluctant responders (89%) indicated that a tablet-based survey is their preferred method of survey completion.ConclusionsUse of a tablet-based version of the survey was effective in recruiting reluctant responders and this group reported positive experiences with this mode of survey administration.