Surfactant Delivery Research Articles

SAVING AND EARLY DICHARGE OF A NEONATE WITH SEVERE MECONIUM ASPIRATION SYNDROME

Animal experiments have shown the resolution of radiological infiltrates of meconium aspiration syndrome (MAS) after using surfactant lavage. Intra-tracheal instillation of surfactant, as well as surfactant lavage, is studied in MAS. However, INSURE (INtubation, administration of SURfactant, Extubation) is never reported to have been used for meconium aspiration syndrome although it is used as the standard method of delivery of surfactant for respiratory distress syndrome. This is a case report of the use of INSURE technique for severe Meconium Aspiration syndrome. The baby was born at term gestational age to a primigravida mother by C-section for fetal distress. The baby was vigorous with chest retractions. Hence baby was supported with delivery room Continuous positive airway pressure (CPAP) and shifted to Neonatal Intensive Care Unit (NICU). In NICU, the baby was stabilized and given surfactant using the INSURE technique. Subsequently, a Chest X-ray showed clearing of lung infiltrates and drastically reduced oxygen requirement of the baby and the baby was discharged early to home.

Surfactant Administration Through Laryngeal or Supraglottic Airways (SALSA): A Viable Method for Low-Income and Middle-Income Countries.

Administration of liquid surfactant through an endotracheal tube for the treatment of respiratory distress syndrome has been the standard of care for decades. A skilled health care provider is needed to perform this procedure. In lower-income and middle-income countries (LMICs), healthcare resources are often limited, leading to increased mortality of premature infants, many of whom would benefit from surfactant administration. Therefore, having a simplified procedure for delivery of surfactant without the need for advanced skills could be life-saving, potentially diminish gaps in care, and help ensure more equitable global neonatal survival rates. Modifications to the standard approach of surfactant administration have been put into practice and these include: INtubation-SURfactant-Extubation (INSURE), thin catheter surfactant administration (TCA), aerosolized surfactant, and surfactant administration through laryngeal or supraglottic airways (SALSA). Although there is a need for larger studies to evaluate the comparative effectiveness of these newer methods, these methods are being embraced by the global community and being implemented in various settings throughout the world. Because the SALSA technique does not require laryngoscopy, a provider skilled in laryngoscopy is not required for the procedure. Therefore, because of the ease of use and safety profile, the SALSA technique should be strongly considered as a viable method of delivering surfactant in LMICs.

Comment on "Bilayer aggregate microstructure determines viscoelasticity of lung surfactant suspensions" by C. O. Ciutara and J. A. Zasadzinski, Soft Matter, 2021, 17, 5170-5182.

For applications of pulmonary surfactant delivery to the lungs, the question of rheology of the existing clinical formulations is of upmost importance. Recently, Ciutara and Zasadsinky (C. O. Ciutara and J. A. Zasadzinski, Soft Matter, 2021, 17, 5170-5182.) measured the rheological properties of Infasurf®, Survanta® and Curosurf®, three of the most used pulmonary surfactant substitutes. This study revealed that these fluids are shear-thinning and characterized by a yield stress. The results obtained by Ciutara et al. on Curosurf® differ from our results published in L.-P.-A. Thai, F. Mousseau, E. Oikonomou, M. Radiom and J.-F. Berret, Colloids Surf., B, 2019, 178, 337-345. and in L.-P.-A. Thai, F. Mousseau, E. Oikonomou, M. Radiom and J.-F. Berret, ACS Nano, 2020, 14, 466-475. In contrast, we found that Curosurf® suspensions are viscous Newtonian or slightly shear-thinning fluids, with no evidence of yield stress. The purpose of this Comment is to discuss possible causes for the discrepancy between the two studies, and to suggest that for biological fluids such as surfactant substitutes, the microrheology technique of rotational magnetic spectroscopy (MRS) can provide valuable results.

Alternative Methods of Surfactant Administration in Preterm Infants with Respiratory Distress Syndrome: State of the Art.

For preterm infants with respiratory distress syndrome, delivery of surfactant via brief intubation (INtubate, SURfactant, Extubate; InSurE) has been the standard technique of surfactant administration. However, this method requires intubation and positive pressure ventilation. It is thought that even the short exposure to positive pressure inflations may be enough to initiate the cascade of events that lead to lung injury in the smallest neonates. In an effort to avoid tracheal intubation and positive pressure ventilation, several alternative and less invasive techniques of exogenous surfactant administration have been developed over the years. These have been investigated in clinical studies, including randomized clinical trials, and have demonstrated advantages such as a decrease in the need for mechanical ventilation and incidence of bronchopulmonary dysplasia. These newer techniques of surfactant delivery also have the benefit of being easier to perform. Surfactant delivery via pharyngeal instillation, laryngeal mask, aerosolization, and placement of a thin catheter are being actively pursued in research. We present a contemporary review of surfactant administration for respiratory distress syndrome via these alternative methods in the hope of guiding physicians in their choices for surfactant application in the neonatal intensive care unit.

Predictors of mortality in premature babies with respiratory distress syndrome treated by early rescue surfactant therapy.

To determine the predictors of mortality following early rescue surfactant therapy in preterm babies with respiratory distress syndrome. Prospective cohort study enrolling babies between 28 weeks to 34 weeks with respiratory distress syndrome requiring early rescue surfactant therapy. For statistical analysis babies were further divided into two subgroups: survivors and non-survivors. Maternal and neonatal variables were compared between the two groups to find out the predictors of mortality. Out of total 110 babies, 72 (65.45%) survived. The mean birth weight and mean gestational age of the study population was 1614.36 (±487.86) g and 31.40 (±2.0)1 weeks, respectively. Birth weight < 1500 g, gestational age < 32 weeks, primiparity, vaginal delivery, prolonged rupture of membranes, lack of antenatal steroid cover, bag and mask ventilation at birth, sepsis, apneic episodes and mechanical ventilation were significantly associated with death on univariate analysis. On multivariate analysis, very low birth weight, vaginal delivery, lack of antenatal steroid cover, bag and mask ventilation at birth and mechanical ventilation were found to be independent predictors of mortality. Some of the identified predictors of mortality are modifiable and can be used to draw up a screening tool to predict the clinical severity and mortality among these babies.

Airway injury and pneumomediastinum associated with less invasive surfactant administration in a premature neonate: a case report

BackgroundThe use of less invasive surfactant administration (LISA)/minimally invasive surfactant therapy (MIST) has increased due to its potential advantage over traditional surfactant delivery methods through an endotracheal tube. Known complications for this procedure include failure of the first attempt at insertion, desaturation, and bradycardia. To the best of our knowledge, this is the first reported case of pneumomediastinum and subcutaneous emphysema following LISA.Case presentationA preterm newborn born at 27 weeks of gestation presented with respiratory distress syndrome requiring surfactant replacement. LISA using the Hobart method was completed. There was a report of procedural difficulty related to increased resistance to insertion of the 16G angiocath. The newborn was subsequently noted to have subcutaneous emphysema over the anterior aspect of the neck and substantial pneumomediastinum on radiological assessment. Associated complications included hypotension requiring inotropic support. The newborn was successfully managed conservatively, with complete resolution of the air leak.ConclusionsUpper airway injury leading to air leak syndrome is a rare complication of the Hobart method for LISA. Awareness of such procedural complications is important as the use of the LISA method increases.

A systematic review of surfactant delivery via laryngeal mask airway, pharyngeal instillation, and aerosolization: Methods, limitations, and outcomes.

Less invasive surfactant administration methods without laryngoscopy and endotracheal catheterization include delivery via laryngeal mask airway, pharyngeal instillation, and aerosolization. These less invasive techniques are promising and have several advantages over INSURE(Intubation-Surfactant-Extubation) and thin catheter techniques. The objective of this review is to discuss the requisites, techniques, short-term outcomes, and adverse events associated with these methods.

Impact of Catheter Choice on Procedural Success of Minimally Invasive Surfactant Therapy.

Surfactant delivery via a thin endotracheal catheter during spontaneous breathing; a technique called minimally invasive surfactant therapy (MIST) is an alternative to intubation and surfactant administration. Procedural details among different centers vary, with marked differences in the choice of catheter to instill surfactant. Studies report use of feeding catheters, multiaccess suction catheters, vascular catheters, and more recently custom-built catheters for this purpose. The impact of choice of catheter on procedural success and procedural adverse effects has not been reported. Our present study compares the procedural success and adverse effects of MIST using a semirigid vascular catheter (16G Angiocath-Hobart Method) versus a flexible multiaccess catheter (MAC). This was a retrospective review of prospectively collected data at a tertiary care neonatal intensive care unit in Southwestern Ontario. All neonates who received surfactant via MIST between May 1, 2016 and September 30, 2020 were included in the study. Relevant baseline characteristics and data on procedural details (premedication, type of catheter, etc.) were collected. The procedural success, number of attempts, and adverse effects between neonates who received MIST via MAC and 16G Angiocath was compared by using Chi-square test or Fisher's test as appropriate. A p-value of less that 0.05 was considered significant. A total of 139 neonates received surfactant via MIST method during the study period. Moreover, 93 neonates received the surfactant via MAC, while 46 received it via Angiocath. The baseline demographic characteristics in the two group were similar. A higher proportion of neonates in Angiocath group received Atropine (100 vs. 76%, p = 0.002) and Fentanyl (98 vs. 36%, p < 0.001) than the MAC group.The procedural success was 91% in the Angiocath group and 89% in the MAC group (p > 0.99). Multiple attempts were needed in 24% of neonates in the Angiocath group and 37% in the MAC group (p = 0.158). More episodes of desaturations were noted in the Angiocath group (89%) than the MAC group (69%; p = 0.012). Other rates of common adverse effects were similar between the two groups. On exploratory analysis fentanyl use held significant association with less success, more desaturation, apneic episodes, and need of positive pressure ventilation /intubation. The overall procedural success of MIST is similar in both catheter groups. The proportion of neonates requiring multiple attempts was lower with the Angiocath, though difference was not statistically significant. Desaturation episodes were seen more frequently in the Angiocath group, which was related to higher use of procedural sedation in this group. · MIST is emerging as a less invasive method of surfactant delivery that has proven clinical benefits.. · Considerable, procedural variation is reported, particularly regarding choice of catheter.. · Our present study compares the procedural success and adverse effects of MIST using a semirigid vascular catheter (16G Angiocath-Hobart method) versus a flexible MAC.. · High and comparable procedural success was seen in both groups..

Less-Invasive Surfactant Administration for Neonatal Respiratory Distress Syndrome: A Consensus Guideline

Introduction: Less-invasive surfactant administration (LISA) is a method of surfactant delivery to preterm infants for treating respiratory distress syndrome (RDS), which can reduce the composite risk of death or bronchopulmonary dysplasia and the time on mechanical ventilation. Methods: A systematic literature search of studies published up to April 2021 on minimally invasive catheter surfactant delivery in preterm infants with RDS was conducted. Based on these studies, with parental feedback sought via an online questionnaire, 9 UK-based specialists in neonatal respiratory disease developed their consensus for implementing LISA. Recommendations were developed following a modified, iterative Delphi process using a questionnaire employing a 9-point Likert scale and an a priori level of agreement/disagreement. Results: Successful implementation of LISA can be achieved by training the multidisciplinary team and following locally agreed guidance. From the time of the decision to administer surfactant, LISA should take <30 min. The comfort of the baby and requirements to maintain non-invasive respiratory support are important. While many infants can be managed without requiring additional sedation/analgesia, fentanyl along with atropine may be considered. Parents should be provided with sufficient information about medication side effects and involved in treatment discussions. Conclusion: LISA has the potential to improve outcomes for preterm infants with RDS and can be introduced as a safe and effective part of UK-based neonatal care with appropriate training.

Early INSURE Therapy Reduces CPAP Failure in Late Preterm Newborns with Respiratory Distress Syndrome

Background: INSURE (Intubation, Surfactant administration, and Extubation) therapy is controversial in managing respiratory distress syndrome (RDS) in late preterm newborns. This study aims to determine whether the use of the INSURE in late preterm infants with RDS is associated with improved outcomes compared to similar infants managed with CPAP alone. Methods: A retrospective cohort study compared two different neonatal care units with two different treatments of RDS in late preterm infants in Bucaramanga, Colombia. One cohort used selective bubble CPAP and rescue surfactant, the second cohort used selective bubble CPAP and INSURE within the first hour of life. We included all the newborns with gestational age between 33 - 366/7 weeks, born between 2012 to 2017, that developed early RDS and were treated with CPAP. Results: We recruited 208 patients (57 CPAP and rescue surfactant and 151 CPAP + INSURE). Early INSURE was reported in 117 patients (56.3 %). INSURE therapy was associated with a reduced risk of CPAP failure (RR = 0.50; 95 % CI 0.26 - 0.98); this effect was evident only when surfactant was administered within the first two hours of life (RR = 0.29; 95 % CI 0.12 - 0.69). Early INSURE was associated with a decreased risk of pneumothorax (RR = 0.07; 95 % CI 0.01 - 0.77) and pulmonary hypertension (RR = 0.34; 95 % CI 0.14 - 0.78). Conclusions: Early INSURE therapy was associated with a reduced incidence of CPAP failure, pneumothorax, and pulmonary hypertension in late preterm infants with moderate to severe RDS. Large, well-powered randomized controlled trials are needed to confirm these observations, but its use is supported by studies with similar results in more premature infants.

Less Invasive Surfactant Administration (LISA) vs. Intubation Surfactant Extubation (InSurE) in Preterm Infants with Respiratory Distress Syndrome: A Pilot Randomized Controlled Trial.

There has been an endeavor in recent years, to administer surfactant by minimally invasive techniques to neonates with surfactant deficiency. The objective of this study was to compare the need for intubation and mechanical ventilation after surfactant delivery, using Less Invasive Surfactant Administration (LISA) technique and Intubation SURfactant Extubation (InSurE), in preterm infants with respiratory distress syndrome (RDS). We conducted a pilot randomized control trial (RCT) at a tertiary care center over a period of 18 months. Preterm neonates with RDS (gestational age 28-36 weeks) were randomized to receive surfactant within 6 h of birth by InSurE or LISA. The primary outcome was need for intubation and mechanical ventilation within 72 h of birth. Infants were followed until discharge for adverse events and complications. A total of 40 infants were analyzed (20 in each group). There was no difference in the need for intubation and mechanical ventilation within 72 h of birth between the two groups [InSurE, 6 (30%) and LISA, 6 (30%), relative risk 1.0, 95% confidence interval 0.51-1.97]. About 15% of infants in both groups had adverse events during the procedure. There was no statistically significant difference in the rates of major complications or duration of respiratory support, hospital stay and mortality. We found LISA to be feasible and equally effective as InSurE for surfactant administration in the treatment of RDS in preterm infants. Future larger RCTs are required to compare the efficacy and long-term outcomes of LISA with the standard invasive methods of surfactant administration.

Surfactant delivery via thin catheters: Methods, limitations, and outcomes.

Various less invasive surfactant administration strategies like surfactant replacement therapy via thin catheters, laryngeal mask airway, pharyngeal instillation, and nebulized surfactant are increasingly being practiced to avoid the harmful effects of endotracheal intubation and ventilation. Numerous studies have been done to study surfactant replacement via thin catheters whereas little data is available for other methods. However, there are variations in premedication policies, type of respiratory support used in these studies. Surfactant delivery using thin catheters has been reported to be associated with decrease in the need for mechanical ventilation (MV), duration of MV, bronchopulmonary dysplasia and neonatal mortality. With the current evidence, among all the available surfactant delivery methods, the one using thin catheters appears to be the most feasible and beneficial to improve clinical neonatal outcomes.

Efficacy and safety of surfactant administration via thin catheter in preterm infants with neonatal respiratory distress syndrome: A systematic review and meta-analysis.

The efficacy and safety of surfactant administration via thin catheter in preterm infants with neonatal respiratory distress syndrome (NRDS) was investigated. PubMed, Embase, Cochrane Library, and Web of Science databases were searched to identify randomized controlled trials (RCTs) that comparing thin catheter technique with intubation for surfactant delivery in preterm infants with NRDS. Thirteen RCTs (1931 infants) were included in the meta-analysis. The use of thin catheter technique decreased the incidences of bronchopulmonary dysplasia (BPD), pneumothorax, and hemodynamically significant patent ductus arteriosus (hsPDA) (risk ratio [RR]: 0.59, 95% confidence interval [CI]: 0.46-0.75, p < .0001; RR: 0.60, 95% CI: 0.39-0.93, p = .02 and RR: 0.88, 95% CI: 0.78-1.00, p = .04, respectively). In addition, infants in the intervention group required less mechanical ventilation within 72 h of life or during hospitalization (RR: 0.60, 95% CI: 0.48-0.75, p < .00001 and RR: 0.64, 95% CI: 0.49-0.82, p = .0005, respectively) compared with infants in the control group. However, the rate of surfactant reflux was higher in the intervention group than that in the control group (RR: 2.12, 95% CI: 1.37-3.29, p = .0008). There were no significant differences in mortality and other outcomes between the two groups. The administration of surfactant via thin catheter could lower the requirement for mechanical ventilation, and decrease the incidence of BPD, pneumothorax, and hsPDA.

Minimally invasive surfactant therapy versus intubation for surfactant delivery in preterm infant with RDS: evaluation of safety and efficacy

Background Minimally invasive surfactant therapy (MIST) is a promising mode of administration that offers the potential to limit barotrauma and prevent lung injury in preterm infants with respiratory distress syndrome (RDS). Objective This study assessed the effects of the implementation of MIST on safety and efficacy in infants who met criteria for surfactant administration and were treated by MIST as compared with a historical control group treated with surfactant via an endotracheal tube during mechanical ventilation. Methods This retrospective study included infants born between 2012 and 2017 who met the following inclusion criteria: gestational age 23–36 + 6 weeks, a diagnosis of RDS requiring at least 30% oxygen with or without nasal continuous positive airway pressure (nCPAP). MIST was introduced in 2014 and a comparison was made between the study group who received MIST and the control group who met similar criteria and received surfactant via an endotracheal tube during mechanical ventilation Results No significant differences were found between the groups in baseline and demographic data. Severity of initial disease, assessed by the CRIB II score, was similar in the two groups (control 4.6 ± 2.8, MIST 4.4 ± 2.4, p=.995). The requirement for oxygen during the first 3 d of life was significantly lower (area under the curve [AUC]: p=.001) in the MIST group as assessed by the AUC. Likewise, the mean days of oxygen requirement were significantly lower in the MIST group (Control: 10.3 d, MIST: 5.9 d, p=.04). Only six infants in the MIST group (13%) subsequently required intubation for mechanical ventilation, only one of whom adjacent to the procedure. A modest reduction in duration of ventilation was also noted. Duration of admission was 32 ± 23 d in the control group and 26 ± 21 d in the MIST group, p=.061. No significant differences were found between the groups in the incidence of major morbidities or mortality. No major adverse events related to the procedure were observed. Conclusions Transition to MIST was associated with significantly reduced need for oxygen, mechanical ventilation and surfactant, and a borderline shortened NICU admission.

Stimuli-Responsive, Hydrolyzable Poly(Vinyl Laurate-co-vinyl Acetate) Nanoparticle Platform for In Situ Release of Surfactants.

A stimuli-responsive, sub-100 nm nanoparticle (NP) platform with a hydrolyzable ester side chain for in situ generation of surfactants is demonstrated. The NPs were synthesized via copolymerization of vinyl-laurate and vinyl-acetate [p-(VL-co-VA), 3:1 molar ratio] and stabilized with a protective poly(ethylene-glycol) shell. The NPs are ∼55 nm in diameter with a zeta potential of -54 mV. Hydrolysis kinetics in an accelerated, base-catalyzed reaction show release of about 11 and 30% of the available surfactant at 25 and 80 °C, respectively. The corresponding values in seawater are 22 and 76%. The efficiency of the released surfactant in reducing the interfacial tension, altering wettability, and stabilizing oil-water emulsion was investigated through contact angle measurements and laser confocal scanning microscopy and benchmarked to sodium laurate, a commercially available surfactant. All these measurements demonstrate both the efficacy of the NP system for surfactant delivery and the ability of the released surfactant to alter wettability and stabilize an oil-water emulsion.

Surfactant therapy via thin catheter in preterm infants with or at risk of respiratory distress syndrome.

Surfactant therapy via thin catheter in preterm infants with or at risk of respiratory distress syndrome.

Small Scale Physical and Bio-Chemical Processes Affecting the Transport of Oil after a Spill

AbstractA series of GOMRI-sponsored experimental and computational studies have discovered, elucidated and quantified the impact of small-scale processes on the dispersion, transport and weathering of crude oil slicks and subsurface plumes. Physical interfacial phenomena occurring at micron-scales include the formation of particle-stabilized emulsions, penetration of particles into oil droplets, formation of compound water-containing oil droplets during plume breakup, and the mechanisms affecting the breakup of oil into micro-droplet by tip streaming resulting from the drastic reduction in interfacial tension upon introduction of dispersant. Efforts aimed at development targeted delivery of surfactants have introduced solvent-free halloysite nanotubes that can be filled with surfactants, and preferentially released at oil-water interface. Buoyant surfactant-based gels, which enhance their encounter rates with oil slicks and adhere to weathered oil have also been developed. Studies of oil-bacteria interactions during early phases of biodegradation and shown how the bacteria, some highly active, attach to the oil-water interfaces and form complex films. Clay-decorated droplets sequester these bacteria and promote the propagation of these biofilm. Long extracellular polymeric substance (EPS) streamers generated by these biofilms form connected networks involving multiple droplets and debris, as well as increase the drag on the oil droplets. At 0.01–10 m scales, the generation of subsurface and airborne crude oil droplets by breaking waves, subsurface plumes and raindrop impact have been quantified. For waves, premixing the oil with dispersant reduces the droplets sizes to micron- and submicron-scales, and changes the slope of their size distribution. Without dispersant, the droplet diameters can be predicted based on the turbulence scales. With dispersant, the droplets are much smaller than the turbulence scales owing to the abovementioned tip-streaming. Aerosolization of oil is caused both by the initial splash and by subsequent bubble bursting, as entrained bubbles rise to the surface. Introduction of dispersant increases the airborne nano-droplet concentration by orders of magnitude, raising health questions. Dispersant injection also reduces the size of droplets in subsurface plumes, affecting the subsequent dispersion of these plume by currents and turbulence. Advancements have also been made in modeling of dissolution of oil in plumes, as well as in applications of Large Eddy Simulations (LES) to model plumes containing oil droplets and gas bubbles. The new multiscale framework, which accounts for the droplet size distribution and mass diffusion, can simulate the near- and far-fields of plumes, and predict the effect of vertical mixing promoted by turbulence on the transport of dispersed oil.

Towards homogenization of liquid plug distribution in reconstructed 3D upper airways of the preterm infant

Liquid plug therapies are commonly instilled in premature babies suffering from infant respiratory distress syndrome (IRDS) by a procedure called surfactant replacement therapy (SRT) in which a surfactant-laden bolus is instilled endotracheally in the neonatal lungs, dramatically reducing mortality and morbidity in neonatal populations. Since data are frequently limited, the optimal method for surfactant delivery has yet to be established towards more standardized guidelines. Here, we explore the dynamics of liquid plug transport using an anatomically-relevant, true-scale in vitro 3D model of the upper airways of a premature infant. We quantify the initial plug’s distribution as a function of two underlying parameters that can be clinically controlled; namely, the injection flow rate and the viscosity of the administered fluid. By extracting a homogeneity index (HI), our in vitro results underline how the combination of both high fluid viscosity and injection flow rates may be advantageous in improving homogeneous dispersion. Such outcomes are anticipated to help refine future SRT administration guidelines towards more uniform distribution using more anatomically-realistic 3D in vitro models at true scale of the preterm neonate.

Multivalent counterion induced multilayer adsorption at the air-water interface in dilute Aerosol-OT solutions

The formation of surface multilayer structures, induced by the addition of multivalent counterions in dilute surfactant solutions, has been widely observed in a range of anionic surfactants. The phenomenon is associated with the ability to manipulate surface properties, especially in the promotion of enhanced surface wetting, and in the presence of an extensive near surface reservoir for rapid surface delivery of surfactant and other active components.Hypothesis.In the single alkyl chain anionic surfactants, such as sodium dodecysulfate, SDS, sodium alkylethoxylsulfate, SAES, and alkylestersulfonate, AES, surface multilayer formation is promoted by trivalent counterions such as Al3+, and is generally not observed with divalent counterions, such as Ca2+ or with monovalent counterions. In the di-alkyl chain anionic surfactant, dodecylbenzenesulfonate, LAS, surface multilayer formation now occurs in the presence of divalent counterions. It is attributed to the closer proximity of a bulk lamellar phase, resulting in a greater tendency for surface multilayer formation, and hence should occur in other di-alkyl chain anionic surfactants.Experiments.Aerosol-OT, AOT, is one of the most commonly used di-alkyl chain anionic surfactants, and is extensively used as an emulsifying, wetting and dispersing agent. This paper reports on predominantly neutron reflectivity, NR, measurements which explore the nature of surface multilayer formation of the sodium salt of AOT at the air-solution interface with the separate addition of Ca2+ and Al3+ counterions.Findings.In the AOT concentration range 0.5 to 2.0 mM surface multilayer formation occurs at the air-solution interface with the addition of Ca2+ or Al3+ counterions. Although the evolution in the surface structure with surfactant and counterion concentration is broadly similar to those reported for SDS, SAES and AES, some notable differences occur. In particular the surfactant and counterion concentration thresholds for surface multilayer formation are higher for Ca2+ than for Al3+. The differences encountered reflect the greater affinity of the di-alkyl chain structure for lamellar formation, and how the surface packing is controlled in part by the headgroup structure and the associated counterion binding affinity.

Implementing less invasive surfactant administration on a neonatal unit

There is increasing evidence reflected in both UK 2019 NICE and European guidelines suggesting that less invasive surfactant administration (LISA) reduces the need for mechanical ventilation and reduces the combined...