Pulmonary surfactant serves as a barrier to respiratory epithelium but can also regulate airway smooth muscle (ASM) tone. Surfactant (SF) relaxes contracted ASM, similar to β2-agonists, anticholinergics, nitric oxide, and prostanoids. The exact mechanism of surfactant relaxation and whether surfactant relaxes hyperresponsive ASM remains unknown. Based on previous research, relaxation requires an intact epithelium and prostanoid synthesis. We sought to examine the mechanisms by which surfactant causes ASM relaxation. Organ bath measurements of isometric tension of ASM of guinea pigs in response to exogenous surfactant revealed that surfactant reduces tension of healthy and hyperresponsive tracheal tissue. The relaxant effect of surfactant was reduced if prostanoid synthesis was inhibited and/or if prostaglandin E2-related EP2 receptors were antagonized. Atomic force microscopy revealed that human ASM cells stiffen during contraction and soften during relaxation. Surfactant softened ASM cells, similarly to the known bronchodilator prostaglandin E2 (PGE2) and the cell softening was abolished when EP4 receptors for PGE2 were antagonized. Elevated levels of PGE2 were found in cultures of normal human bronchial epithelial cells exposed to pulmonary surfactant. We conclude that prostaglandin E2 and its EP2 and EP4 receptors are likely involved in the relaxant effect of pulmonary surfactant in airways.

BACKGROUND: At present, preterm infants with respiratory distress syndrome (RDS) in China present higher mortality and morbidity rates than those in high-income countries. The aim of this nationwide survey was to assess the clinical management of RDS in China.
METHODS: A nationwide cross-sectional survey to assess adherence to RDS management recommendations was performed. One neonatologist per hospital was randomly selected. The primary outcome was the key care of RDS management.
RESULTS: Among the 394 participating hospitals, 88·3% were birthing centres. The number of doctors and nurses per bed were 0·27 and 0·72, respectively. Antenatal corticosteroids (any dose) were administered to 90% of the women at risk of preterm birth at < 34 weeks of gestation (90·0% inborn vs. 50·0% outborn, p < 0·001). The median fraction of inspired oxygen (FiO2) for initial resuscitation was 0·30 for babies born at ≤ 32 weeks of gestation and 0·25 for those born at > 32 weeks. T-piece resuscitators were available in 77·8% of delivery rooms (DRs) (tertiary hospitals: 82·5% vs. secondary hospitals: 63·0%, p < 0·001). Surfactant was used in 51·6% of the DRs. Less invasive surfactant administration (LISA) was used in 49·7% of the hospitals (tertiary hospitals: 55·3% vs. secondary hospitals: 31·5%, p < 0·001). Primary non-invasive ventilation was initiated in approximately 80·0% of the patients. High-frequency oscillation ventilation was primarily reserved for rescue after conventional mechanical ventilation (MV) failure. Caffeine was routinely used during MV in 59·1% of the hospitals. Bedside lung ultrasonography was performed in 54·3% of the health facilities (tertiary hospitals: 61·6% vs. secondary hospitals: 30·4%, p < 0·001). Qualified breast milk banks and Family Integrated Care (FICare) were present in 30·2% and 63·7% of the hospitals, respectively.
CONCLUSIONS: Significant disparities in resource availability and guidelines adherence were evident across hospitals. Future strategies should address DR facilities and medication access, technical training, staff allocation, and ancillary facility development for a better management of RDS patients in China.

BACKGROUND: Culturally competent healthcare improves patient satisfaction and clinical outcomes. Many drugs, dressings and implants have human or animal-derived content which may conflict with patients\' religious beliefs, and may even have medicolegal implications.
METHODS: This cross-sectional study (anonymous web-based survey) was done to understand the informed consent process followed by paediatricians and neonatologists in India, their views regarding disclosure pertaining to the animal origin of exogenous surfactants to patients\' families, and their willingness and ability to provide alternative surfactants based on parental preferences.
RESULTS: A total of 114 neonatologists/paediatricians involved in neonatal care and using surfactants in their practice responded to the survey. Although 61(53.5%) neonatal care units stocked two or more brands of surfactant in their inventory, only 38(33.3%) units had both bovine and porcine preparations. Most (104, 91.2%) of the doctors always take parental consent before administering surfactants; but only a few (12,10.5%) said they always inform parents about its animal origin. None of the respondents offer parents a choice between bovine or porcine-origin surfactants, most (73, 64%) presuming that it would be irrelevant for the parents. However, many respondents (27, 23.7%) mentioned that they want to offer the choice to parents but are unable to do so because they do not stock both bovine and porcine preparations.
CONCLUSIONS: Although most parents might agree to a life-saving medicine in emergency situations, this does not mean they do not want to be informed. Healthcare professionals should not have a dismissive attitude to parental belief systems. They must use the antenatal period to take the cultural/spiritual history and the necessary consent.

Surfactant administration significantly improves respiratory outcomes in preterm infants with respiratory distress syndrome (RDS). However, surfactant administration may lead to hemodynamic alterations, particularly in the heart, affecting the patent ductus arteriosus (PDA), the consequences of which are not fully understood. This prospective observational study took place in an Indian neonatal care unit from July 2019 to November 2020, enrolling preterm neonates (26-34 weeks\' gestation) with RDS needing non-invasive positive pressure ventilation. They were divided into two groups: those who received surfactant while on respiratory support and those who did not. All newborns in the study had an initial echocardiogram within 24 h to detect PDA flow. Subsequent echocardiograms were conducted between 48 and 72 h or earlier based on symptoms. Of 220 infants requiring respiratory support, 84 were enrolled, with 42 in each group. While demographic variables were similar, the surfactant group had a lower median gestational age (29.0 vs. 31.0 weeks). In the surfactant group, a significantly higher percentage of neonates had hemodynamically significant PDA (hsPDA) compared to the non-surfactant group (54.76% vs. 26.19%, P-value = .008). Multiple logistic regression found no significant association between gestation, birth weight, or shock and hsPDA occurrence. Pulmonary hemorrhage occurred more often in the surfactant group. Bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH) > grade 2, and necrotizing enterocolitis (NEC) ≥ grade 2 did not differ significantly between the groups. Surfactant therapy via the less invasive surfactant administration technique was associated with a higher incidence of hsPDA. While surfactant is crucial for neonatal respiratory care, its potential hemodynamic effects, including hsPDA, should be considered.

OBJECTIVE: We investigated the predictive value of a lung ultrasound score (LUS) for surfactant administration in a United States Level 4 Neonatal Intensive Care Unit.
METHODS: Thirty infants born at <37 weeks gestational age with respiratory distress syndrome associated respiratory failure requiring continuous positive airway pressure were included. A LUS was obtained within six hours of life. Surfactant administration in the first five days of life was recorded. Receiver operating characteristic (ROC) analysis for LUS and surfactant administration was performed.
RESULTS: Median completed gestational age was 33 weeks (31-34 weeks interquartile range) and median birth weight was 2.0 kg (1.5-2.3 kg). LUS for predicting an initial surfactant dose had an area under the ROC curve of 0.97. A score > 9 provided 100% sensitivity and 91% specificity for predicting administration of an initial surfactant dose.
CONCLUSIONS: A LUS > 9 provided excellent sensitivity and specificity for predicting which infants will receive surfactant for associated respiratory failure.

OBJECTIVE: Improving the deep lung delivery of aerosol surfactant therapy (AST) with a dry powder formulation may enable significant reductions in dose while providing improved efficacy. The objective of Part I of this two-part study was to present the development of a new dry powder aerosol synthetic lung surfactant (SLS) product and to characterize performance based on aerosol formation and realistic in vitro airway testing leading to aerosol delivery recommendations for subsequent in vivo animal model experiments.
METHODS: A new micrometer-sized SLS excipient enhanced growth (EEG) dry powder formulation was produced via spray drying and aerosolized using a positive-pressure air-jet dry powder inhaler (DPI) intended for aerosol delivery directly to intubated infants with respiratory distress syndrome (RDS) or infant-size test animals.
RESULTS: The best-case design (D2) of the air-jet DPI was capable of high emitted dose (> 80% of loaded) and formed a < 2 µm mass median aerodynamic diameter (MMAD) aerosol, but was limited to ≤ 20 mg mass loadings. Testing with a realistic in vitro rabbit model indicated that over half of the loaded dose could penetrate into the lower lung regions. Using the characterization data, a dose delivery protocol was designed in which a 60 mg total loaded dose would be administered and deliver an approximate lung dose of 14.7-17.7 mg phospholipids/kg with a total aerosol delivery period < 5 min.
CONCLUSIONS: A high-efficiency aerosol SLS product was designed and tested that may enable an order of magnitude reduction in administered phospholipid dose, and provide rapid aerosol administration to infants with RDS.

Gas flow is fundamental for driving tidal ventilation and thus the speed of lung motion, but current bias flow settings to support the preterm lung after birth are without an evidence base. We aimed to determine the role of gas bias flow rates to generate positive pressure ventilation in initiating early lung injury pathways in the preterm lamb. Using slower speeds to inflate the lung during tidal ventilation (gas flow rates 4-6 L/min) did not impact lung mechanics, mechanical power or gas exchange compared to those currently used in clinical practice (8-10 L/min). Speed of pressure and volume change during inflation were faster with higher flow rates. Lower flow rates resulted in less bronchoalveolar fluid protein, better lung morphology and fewer detached epithelial cells. Overall, relative to unventilated fetal controls, there was greater protein change using 8-10 L/min, which was associated with enrichment of acute inflammatory and innate responses. Slowing the speed of lung motion by supporting the preterm lung from birth with lower flow rates than currently used clinically resulted in less lung injury without compromising tidal ventilation or gas exchange.

A thin film of pulmonary surfactant lines the surface of the airways and alveoli, where it lowers the surface tension in the peripheral lungs, preventing collapse of the bronchioles and alveoli and reducing the work of breathing. It also possesses a barrier function for maintaining the blood-gas interface of the lungs and plays an important role in innate immunity. The surfactant film covers the epithelium lining both large and small airways, forming the first line of defense between toxic airborne particles/pathogens and the lungs. Furthermore, surfactant has been shown to relax airway smooth muscle (ASM) after exposure to ASM agonists, suggesting a more subtle function. Whether surfactant masks irritant sensory receptors or interacts with one of them is not known. The relaxant effect of surfactant on ASM is absent in bronchial tissues denuded of an epithelial layer. Blocking of prostanoid synthesis inhibits the relaxant function of surfactant, indicating that prostanoids might be involved. Another possibility for surfactant to be active, namely through ATP-dependent potassium channels and the cAMP-regulated epithelial chloride channels [cystic fibrosis transmembrane conductance regulators (CFTRs)], was tested but could not be confirmed. Hence, this review discusses the mechanisms of known and potential relaxant effects of pulmonary surfactant on ASM. This review summarizes what is known about the role of surfactant in smooth muscle physiology and explores the scientific questions and studies needed to fully understand how surfactant helps maintain the delicate balance between relaxant and constrictor needs.

Lubricating base oils have been extensively employed for producing various industrial and consumer products. Therefore, their environmental and health impacts should be carefully evaluated. Although there have been many reports on pulmonary cytotoxicity and inflammatory responses of inhaled lubricating base oils, their potential influences on pulmonary surfactant (PS) films that play an essential role in maintaining respiratory mechanics and pulmonary immunity remains largely unknown. Here a systematic study on the interactions between an animal-derived natural PS and aerosols of water and representative mineral and vegetable base oils is performed using a novel biophysical assessing technique called constrained drop surfactometry capable of providing in vitro simulations of normal tidal breathing and physiologically relevant temperature and humidity in the lung. It was found that the mineral oil aerosols can impose strong inhibitions to the biophysical property of PS film, while the airborne vegetable oils and water show negligible adverse effects within the studied concentration range. The inhibitory effect is originated from the strong hydrophobicity of mineral oil, which makes it able to disrupt the interfacial molecular ordering of both phospholipid and protein compositions and consequently suppress the formation of condensed phase and multilayer scaffolds in a PS film. ENVIRONMENTAL IMPLICATION: Understanding the biophysical influence of airborne lubricating base oils on pulmonary surfactant (PS) films can provide new insights into the environmental impacts and health concerns of various industrial lubricant products. Here a comparative study on interactions between an animal-derived natural PS film and the aerosols of water and representative mineral and vegetable base oils under the true physiological conditions was conducted in situ using constrained drop surfactometry. We show that the most frequently used mineral base oil can cause strong inhibitions to the PS film by disrupting the molecular ordering of saturated phospholipids and surfactant-associated proteins at the interface.

Fibrosis in the lung is thought to be driven by epithelial cell dysfunction and aberrant cell-cell interactions. Unveiling the molecular mechanisms of cellular plasticity and cell-cell interactions is imperative to elucidating lung regenerative capacity and aberrant repair in pulmonary fibrosis. By mining publicly available RNA-Seq data sets, we identified loss of CCAAT enhancer-binding protein alpha (CEBPA) as a candidate contributor to idiopathic pulmonary fibrosis (IPF). We used conditional KO mice, scRNA-Seq, lung organoids, small-molecule inhibition, and potentially novel gene manipulation methods to investigate the role of CEBPA in lung fibrosis and repair. Long-term (6 months or more) of Cebpa loss in AT2 cells caused spontaneous fibrosis and increased susceptibility to bleomycin-induced fibrosis. Cebpa knockout (KO) in these mice significantly decreased AT2 cell numbers in the lung and reduced expression of surfactant homeostasis genes, while increasing inflammatory cell recruitment as well as upregulating S100a8/a9 in AT2 cells. In vivo treatment with an S100A8/A9 inhibitor alleviated experimental lung fibrosis. Restoring CEBPA expression in lung organoids ex vivo and during experimental lung fibrosis in vivo rescued CEBPA deficiency-mediated phenotypes. Our study establishes a direct mechanistic link between CEBPA repression, impaired AT2 cell identity, disrupted tissue homeostasis, and lung fibrosis.