Bovine Surfactant Research Articles

Effects of the lung surfactant protein B construct Mini-B on lipid bilayer order and topography

The hydrophobic lung surfactant protein, SP-B, is essential for survival. Cycling of lung volume during respiration requires a surface-active lipid-protein layer at the alveolar air-water interface. SP-B may contribute to surfactant layer maintenance and renewal by facilitating contact and transfer between the surface layer and bilayer reservoirs of surfactant material. However, only small effects of SP-B on phospholipid orientational order in model systems have been reported. In this study, N-terminal (SP-B(8-25)) and C-terminal (SP-B(63-78)) helices of SP-B, either linked as Mini-B or unlinked but present in equal amounts, were incorporated into either model phospholipid mixtures or into bovine lipid extract surfactant in the form of vesicle dispersions or mechanically oriented bilayer samples. Deuterium and phosphorus nuclear magnetic resonance (NMR) were used to characterize effects of these peptides on phospholipid chain orientational order, headgroup orientation, and the response of lipid-peptide mixtures to mechanical orientation by mica plates. Only small effects on chain orientational order or headgroup orientation, in either vesicle or mechanically oriented samples, were seen. In mechanically constrained samples, however, Mini-B and its component helices did have specific effects on the propensity of lipid-peptide mixtures to form unoriented bilayer populations which do not exchange with the oriented fraction on the timescale of the NMR experiment. Modification of local bilayer orientation, even in the presence of mechanical constraint, may be relevant to the transfer of material from bilayer reservoirs to a flat surface-active layer, a process that likely requires contact facilitated by the formation of highly curved protrusions.

Successful use of bronchoscopic lung insufflation to treat left lung atelectasis

We report first use of bronchoscopic lung insufflation in a child to treat acute left lung collapse. The patient is a 6-year old male asthmatic who was hospitalized with a 2-day history of cough, chest pain, and abdominal pain. He was tachypneic and hypoxemic on room air. Chest exam revealed diminished breath sounds on the left side. Chest X-ray and Chest CT showed complete left lung collapse. He underwent bronchoscopic lung insufflation procedure by injecting total of 200 ml air via flexible bronchoscope in the left upper lobe using 50cc syringe aliquots followed by similar injection of 200 ml of air in left lower lobe. After air insufflations, 6 ml of bovine surfactant (calfactant) were instilled in each lobe. Chest fluoroscopy was done immediately after procedure and showed expansion of entire left lung with no pneumothorax. The procedure was well tolerated. The patient's symptoms and hypoxemia resolved soon after procedure. However, left lower lobe atelectasis recurred next day and persisted for 6 days despite treatments with chest physical therapy, systemic steroids, oral azithromycin, nebulized dornase alpha, and endoscopic removal of secretions from left lower lobe. Bronchoscopic insufflation of left lower lobe was repeated resulting in immediate expansion of that lobe as demonstrated by intraoperative fluoroscopy. The patient was discharged home next day. This case suggests that brochoscopic lung insufflation can be safe and effective in treating acute lung collapse and in treating atelectasis which is refractory to conventional therapy.

Therapeutic effect of surfactant inhalation during warm ischemia in an isolated rat lung perfusion model

Warm ischemia-reperfusion injury related to donation after cardiac death donors is a crucial and inevitable issue. As surfactant function is known to deteriorate during warm ischemia, we hypothesized that surfactant inhalation during warm ischemia would mitigate warm ischemia-reperfusion injury. We used an isolated rat lung perfusion model. The rats were divided into three groups: sham, control, and surfactant. In the control and surfactant groups, cardiac arrest was induced by ventricular fibrillation. Ventilation was restarted 110 min later; subsequently, the lungs were flushed, and heart and lung block was recovered. In the surfactant group, a natural bovine surfactant Surfacten(®) was inhaled for 3 min at the end of warm ischemia. Then, the lungs were reperfused for 80 min. Surfactant inhalation significantly improved graft functions, effectively increased lung tissue ATP levels, and significantly decreased mRNA levels of IL-6 and IL-6/IL-10 ratio at the end of reperfusion. Histologically, lungs in the surfactant group showed fewer signs of interstitial edema and hemorrhage, and significantly less neutrophilic infiltration than those in the control group. Our results indicated that surfactant inhalation in the last phase of warm ischemia maintained lung tissue energy levels and prevented cytokine production, resulting in the alleviation of warm ischemia-reperfusion injury.

Orientation and depth of surfactant protein B C-terminal helix in lung surfactant bilayers

SP-BCTERM is a cationic amphipathic helical peptide and functional fragment composed of residues 63 to 78 of surfactant protein B (SP-B). Static oriented and magic angle spinning solid state NMR, along with molecular dynamics simulation was used to investigate its structure, orientation, and depth in lipid bilayers of several compositions, namely POPC, DPPC, DPPC/POPC/POPG, and bovine lung surfactant extract (BLES). In all lipid environments the peptide was oriented parallel to the membrane surface. While maintaining this approximately planar orientation, SP-BCTERM exhibited a flexible topology controlled by subtle variations in lipid composition. SP-BCTERM-induced lipid realignment and/or conformational changes at the level of the head group were observed using 31P solid-state NMR spectroscopy. Measurements of the depth of SP-BCTERM indicated the peptide center positions ~8Å more deeply than the phosphate headgroups, a topology that may allow the peptide to promote functional lipid structures without causing micellization upon compression.

Derecruitment Test and Surfactant Therapy in Patients with Acute Lung Injury

Introduction. A recruitment maneuver (RM) may improve gas exchange in acute lung injury (ALI). The aim of our study was to assess the predictive value of a derecruitment test in relation to RM and to evaluate the efficacy of RM combined with surfactant instillation in patients with ALI. Materials and Methods. Thirteen adult mechanically ventilated patients with ALI were enrolled into a prospective pilot study. The patients received protective ventilation and underwent RM followed by a derecruitment test. After a repeat RM, bovine surfactant (surfactant group, n = 6) or vehicle only (conventional therapy group, n = 7) was instilled endobronchially. We registered respiratory and hemodynamic parameters, including extravascular lung water index (EVLWI). Results. The derecruitment test decreased the oxygenation in 62% of the patients. We found no significant correlation between the responses to the RM and to the derecruitment tests. The baseline EVLWI correlated with changes in SpO2 following the derecruitment test. The surfactant did not affect gas exchange and lung mechanics but increased EVLWI at 24 and 32 hrs. Conclusions. Our study demonstrated no predictive value of the derecruitment test regarding the effects of RM. Surfactant instillation was not superior to conventional therapy and might even promote pulmonary edema in ALI.

Economic evaluation of the use of exogenous pulmonary surfactants in preterm newborns in a Mexican population

To estimate the cost-effectiveness ratio of surfactant rescue treatment of premature infants with respiratory distress syndrome (RDS) who are covered by the Medical Insurance for a New Generation. A cost-effectiveness evaluation was conducted from the third-payer perspective. Comparisons were made between the use of bovine surfactant (BS) therapy and without BS therapy. A decision tree model with a lifetime horizon was used where the measurements of effectiveness were life years gained (LYG) and quality-adjusted life years (QALYs). A 5% discount rate was considered for costs and health outcomes. All costs are expressed in Mexican pesos 2009. Incremental cost-effectiveness ratios (ICER) were MXN$136,670 per LYG and MXN$125,250 per QALY. Surfactant therapy was confirmed as a cost-effective strategy in accordance with World Health Organization criteria of three per capita gross domestic product (GDP) per QALY in premature infants with RDS in Mexico.

Protein- and Lipid Modification of Natural Bovine Surfactant

Surfactant therapy does not lead to a uniform, optimal and sustained effect on gas exchange in neonatal respiratory distress syndrome (RDS) and acute respiratory distress syndrome (ARDS). The aim of the present study therefore was to compare the effects of a lipid-enriched and protein-modified natural surfactant preparations with a licensed, clinically used bovine surfactant preparation - SF-Ril (Alveofact). SF-Ril was enriched with phosphatidylglycerol, sphingomyeline, phosphatidylethanolamine plasmalogen, phosphatidylethanolamine. Furthermore, SF-Ril was modified with increased surfactant protein B (SP-B)/surfactant protein C (SP-C) content and finally a mercaptoethanol (ME) treated preparation for breaking the sulfhydril bondage of SP-B/SP-C by chemical reduction in methylene chloride using ME was developed. Finally ME was removed by vacuum extraction. These modified surfactants were tested at a dosage of 100 mg/ kg each in a model of respiratory failure induced by lung lavage in male adult rats and compared with SF-Ril at an identical dosage. Mechanical ventilation was standardised with fraction of inspiratory oxygen (FiO2) 1.0 and time-cycled pressure limited ventilation 16/0.8 cmH2O before and 26/6 cmH2O (peak inspiratory pressure/positive endexpiratory pressure) after lung lavage (target arterial oxygen pressure [pa02] < 100 mmHg), respiratory rate 36/min, inspiration/expiration time ratio 1:2. During the observation period of 120 min, the sphingomyeline substituted and protein-modified (ME reduced) surfactant preparations exerted improved and sustained oxygenation compared with SF-Ril. Similar effects were observed for tidal volumes. All other preparations were equal or inferior to SF-Ril in our model. For the development of surfactant preparations less prone for inactivation the above mentioned data may provide useful information, provided they can be confirmed in further investigations employing other alternative models.

A modified squeeze-out mechanism for generating high surface pressures with pulmonary surfactant

The exact mechanism by which pulmonary surfactant films reach the very low surface tensions required to stabilize the alveoli at end expiration remains uncertain. We utilized the nanoscale sensitivity of atomic force microscopy (AFM) to examine phospholipid (PL) phase transition and multilayer formation for two Langmuir–Blodgett (LB) systems: a simple 3 PL surfactant-like mixture and the more complex bovine lipid extract surfactant (BLES). AFM height images demonstrated that both systems develop two types of liquid condensed (LC) domains (micro- and nano-sized) within a liquid expanded phase (LE). The 3 PL mixture failed to form significant multilayers at high surface pressure (π while BLES forms an extensive network of multilayer structures containing up to three bilayers. A close examination of the progression of multilayer formation reveals that multilayers start to form at the edge of the solid-like LC domains and also in the fluid-like LE phase. We used the elemental analysis capability of time-of-flight secondary ion mass spectrometry (ToF-SIMS) to show that multilayer structures are enriched in unsaturated PLs while the saturated PLs are concentrated in the remaining interfacial monolayer. This supports a modified squeeze-out model where film compression results in the hydrophobic surfactant protein-dependent formation of unsaturated PL-rich multilayers which remain functionally associated with a monolayer enriched in disaturated PL species. This allows the surface film to attain low surface tensions during compression and maintain values near equilibrium during expansion.

Efficacy of Porcine Versus Bovine Surfactants for Preterm Newborns With Respiratory Distress Syndrome: Systematic Review and Meta-analysis

To compare the efficacy of a porcine surfactant (poractant alfa) versus bovine surfactants (beractant and calfactant) with respect to clinical outcomes among preterm infants with respiratory distress syndrome. A search of major electronic databases, including Medline (1980-2010) and the Cochrane Central Register of Controlled Trials, for randomized controlled trials that compared poractant alfa versus beractant and/or calfactant among preterm infants with respiratory distress syndrome who required intubation and surfactant treatment was performed. The primary outcome was oxygen requirement at a postmenstrual age of 36 weeks. Five randomized controlled trials involving 529 infants compared poractant alfa versus beractant for rescue treatment. No trials studied surfactant prophylaxis, and none compared poractant alfa versus calfactant. The incidences of oxygen dependence at a postmenstrual age of 36 weeks were similar for poractant alfa and beractant. Infants treated with poractant alfa at 100 mg/kg (low dose) or 200 mg/kg (high dose) exhibited statistically significant reductions in deaths (relative risk: 0.51 [95% confidence interval: 0.30-0.89]), the need for redosing (relative risk: 0.71 [95% confidence interval: 0.57-0.88]), oxygen requirements, duration of oxygen treatment, and duration of mechanical ventilation. The test of heterogeneity yielded positive results for the latter 2 outcomes. The difference remained statistically significant for deaths and the need for redosing with high-dose poractant alfa but not for low dose poractant alfa. There were significant reductions in deaths and the need for redosing with high-dose poractant alfa but not low-dose poractant alfa, compared with beractant.

Surfactant Therapy for Maternal Blood Aspiration: An Unusual Cause of Neonatal Respiratory Distress Syndrome

Surfactant replacement therapy is the main treatment of neonatal respiratory distress syndrome. However, surfactant therapy has been shown to be effective in the treatment of other diseases causing neonatal respiratory diseases such as pulmonary hemorrhage, meconium aspiration syndrome, pneumonia/sepsis, pulmonary edema or acute lung injury resulting a secondary surfactant deficiency (SSD). Rarely, as like as in the present patient, exogenous blood aspiration such as breast milk or formula aspiration may lead to SSD. Blood in alveolus leads to a significant biochemical and functional disturbance of the surfactant system and inhibits surfactant production. Here, the authors report a preterm infant of 33 wk gestational age with secondary surfactant deficiency due to maternal blood aspiration because of abruptio placentae. She was received two courses of beractant, a natural bovine surfactant, therapy in 24 h. She was extubated on second day and did not require oxygen on 4(th) day. To the authors' knowledge, this is the first reported case of SSD due to maternal blood aspiration treated with surfactant. In conditions such as abruptio placentae, infant should be protected from blood aspiration and if respiratory distress occurs, surfactant inhibition and need for surfactant administration should be considered.

Surfactant protein C is an essential constituent for mucosal adjuvanticity of Surfacten, acting as an antigen delivery vehicle and inducing both local and systemic immunity

We have reported that Surfacten® (St), a bovine pulmonary surfactant free of antigenic c-type lectins, is a useful mucosal adjuvant for nasal vaccination. To prepare ample supplies a synthetic adjuvant that mimics St, we analyzed essential constituents of St for mucosal adjuvanticity. Intranasal inoculation of influenza virus hemagglutinin (HA) vaccine combined with St free of surfactant protein (SP)-C resulted in failure of HA vaccine delivery to dendritic cells and loss of local and systemic immune responses. Naïve bovine SP-C, synthetic human or bovine SP-C peptide reconstituted with three major St lipids restored delivery activity and local and systemic immune responses to levels similar to those of St and provided almost complete protection against lethal doses of influenza virus challenge in mice. The delivery of fluoresceinated HA vaccine to cultured dendritic cells was significantly enhanced by co-administration of St or synthetic adjuvant, and moderately stimulated the expression of MHC class II and CD86. In addition, both St and synthetic adjuvant markedly sustained HA vaccine and achieved a wide antigen distribution in murine nasal cavity. These results suggest that synthetic mucosal adjuvant reconstituted with SP-C peptide and major St lipids is useful for ample supply of the potent mucosal adjuvant as an antigen delivery vehicle for intranasal vaccination.

Another ethical dilemma in neonatology

AimTo ascertain parents attitude, knowledge and awareness of the type of Surfactant used in the Tertiary Neonatal unit to treat Respiratory Distress Syndrome and religious limitations.MethodThis is a pilot project....

Interactions of Benzo[&lt;italic&gt;a&lt;/italic&gt;]pyrene and Diesel Exhaust Particulate Matter with the Lung Surfactant System

One of the reasons for cellular changes in the lung tissue exposed to the diesel exhaust composed of soot particles with adsorbed volatile organic molecules is the reduction of the clearance rate in the pulmonary region of the respiratory system. The interaction of the fractal-like particles and organic substances with a surfactant monolayer limits its dynamic activity. The surface properties of Survanta, a purified extract of bovine lung surfactant (LS), which interacted with carbon particles (200 nm aggregates) and benzo[a]pyrene (BaP), molecules were measured with the oscillating bubble technique. The results showed a significant lowering of the dynamics of the surfactant monolayer compared to the control case (no exposure). Additional measurements of surface pressure during the monotonic compression of the air-water interface containing the major LS phospholipid, dipalmitoylphosphatidylcholine (DPPC), showed that the presence of BaP molecules in the system influenced its stability. The experimental results were supplemented with a theoretical molecular dynamics model of the interaction between BaP and DPPC molecules. The simulation results indicated the insertion of BaP molecules into the lipid layer, which explained the measured effects.

Comparative study of clinical pulmonary surfactants using atomic force microscopy

Clinical pulmonary surfactant is routinely used to treat premature newborns with respiratory distress syndrome, and has shown great potential in alleviating a number of neonatal and adult respiratory diseases. Despite extensive study of chemical composition, surface activity, and clinical performance of various surfactant preparations, a direct comparison of surfactant films is still lacking. In this study, we use atomic force microscopy to characterize and compare four animal-derived clinical surfactants currently used throughout the world, i.e., Survanta, Curosurf, Infasurf and BLES. These modified-natural surfactants are further compared to dipalmitoyl phosphatidylcholine (DPPC), a synthetic model surfactant of DPPC:palmitoyl-oleoyl phosphatidylglycerol (POPG) (7:3), and endogenous bovine natural surfactant. Atomic force microscopy reveals significant differences in the lateral structure and molecular organization of these surfactant preparations. These differences are discussed in terms of DPPC and cholesterol contents. We conclude that all animal-derived clinical surfactants assume a similar structure of multilayers of fluid phospholipids closely attached to an interfacial monolayer enriched in DPPC, at physiologically relevant surface pressures. This study provides the first comprehensive survey of the lateral structure of clinical surfactants at various surface pressures. It may have clinical implications on future application and development of surfactant preparations.

Atomic Force Microscopic Examination of Rat Pulmonary Surfactant Films

The ability of pulmonary surfactant to drive surface tension (ST) to low values near 0 mN/m during compression stabilizes the alveoli at end expiration. The manner in which surfactant phospholipids (PL) (50% unsaturation) attain surface tension near zero is still not clear. Atomic force microscopy (AFM) of rat surfactant extract films at a surface pressure (SP) of 20 mN/m reveals microdomains (mD), apparently composed of liquid-ordered (L0) and tilted-condensed (TC) phases within the predominant liquid-expanded (LE) phase. Numerous nanodomains (nD) were also present. As SP increased to 40 mN/m, the area composed of mD increased but the nD decreased. This contrasts with previous studies with bovine surfactant where the mD appeared to form nD. At 50 mN/m, the film exhibited the formation of numerous stacked multilayers (PL bilayers) which could be incorporated into the monolayer during film expansion. The present results are consistent with the reversible squeeze-out of unsaturated PL into multilayers during compression, resulting in a monolayer highly enriched in gel phase saturated PL components. Furthermore, as with other surfactants, the presence of L0 phase appears related to cholesterol. Reducing the cholesterol content by acetone precipitation resulted in the loss of L0 phase, further implicating this sterol in surfactant phase separation.

Animal Origins of Surfactant: A Survey of Neonatologists’ Perceptions and Practices Regarding Parent Information Sharing

Exogenous surfactants commonly used to treat a variety of neonatal respiratory diseases are derived from either bovine or porcine sources. The extent to which parents are aware of this fact is currently unclear, as is the impact that this may have on familial cultural or religious belief systems. Our primary aims were to assess U.S. neonatologists’ utilization of bovine and porcine surfactant preparations, their views on parent disclosure pertaining to the particular animal origins of exogenous surfactant therapy, and their willingness to provide alternative surfactant preparations based on parental religious preferences. An anonymous Web-based survey was provided to 2,137 neonatologists. There was a 46.9% response rate. We found that 63.4% of respondents used only bovine-derived surfactants, 14.9% exclusively used porcine-based surfactants, and 21.7% used combinations. While 74.3% of neonatologists discussed surfactant use with parents, only 2.2% always discussed its animal origins. When asked, 47.9% of neonatologists believed parental preference for religious reasons would not impact their surfactant choice, 19.4% reported it would affect their choice, and 32.7% said it maybe would. Access to only one surfactant was a major barrier to communication. Results showed that many neonatologists may be open to being inclusive of parents regarding surfactant therapy. Carrying different surfactant types on hospital pharmacy formularies and encouraging physician–parent communication may achieve a more family-centered approach to neonatal care.

Synthesis and activity of a novel diether phosphonoglycerol in phospholipase-resistant synthetic lipid:peptide lung surfactants().

This paper reports the chemical synthesis and purification of a novel phospholipase-resistant C16:0, C16:1 diether phosphonoglycerol with structural analogy to ester-linked anionic phosphatidylglycerol (PG) in endogenous pulmonary surfactant. This diether phosphonoglycerol (PG 1) is studied for phospholipase A(2) (PLA(2)) resistance and for surface activity in synthetic exogenous surfactants combined with Super Mini-B (S-MB) peptide and DEPN-8, a previously-reported diether phosphonolipid analog of dipalmitoyl phosphatidylcholine (DPPC, the major zwitterionic phospholipid in native lung surfactant). Activity experiments measured both adsorption and dynamic surface tension lowering due to the known importance of these surface behaviors in lung surfactant function in vivo. Synthetic surfactants containing 9 : 1 DEPN-8:PG 1 + 3% S-MB were resistant to degradation by PLA(2) in chromatographic studies, while calf lung surfactant extract (CLSE, the substance of the bovine clinical surfactant Infasurf®) was significantly degraded by PLA(2). The 9 : 1 DEPN-8:PG 1 + 3% S-MB mixture also had small but consistent increases in both adsorption and dynamic surface tension lowering ability compared to DEPN-8 + 3% S-MB. Consistent with these surface activity increases, molecular dynamics simulations using Protein Modeller, GROMACS force-field, and PyMOL showed that bilayers containing DPPC and palmitoyl-oleoyl-PC (POPC) as surrogates of DEPN-8 and PG 1 were penetrated to a greater extent by S-MB peptide than bilayers of DPPC alone. These results suggest that PG 1 or related anionic phosphono-PG analogs may have functional utility in phospholipase-resistant synthetic surfactants targeting forms of acute pulmonary injury where endogenous surfactant becomes dysfunctional due to phospholipase activity in the innate inflammatory response.

Production of novel lipopeptide antibiotics related to A54145 by Streptomyces fradiae mutants blocked in biosynthesis of modified amino acids and assignment of lptJ, lptK and lptL gene functions

A54145 is a complex of lipopeptide antibiotics produced by Streptomyces fradiae. A54145 factors are structurally related to daptomycin, with four modified amino acids, only one of which is present in daptomycin. We generated three mutants defective in lptJ, lptK or lptL, whose gene products are involved in the formation of hydroxy-Asn(3) (hAsn(3)) and methoxy-Asp(9) (moAsp(9)). Each of the mutants produced novel lipopeptides related to A54145 and the profiles allowed assignment of functions for those genes. We constructed strains carrying different combinations of these genes coupled with a mutation in the lptI gene involved in the biosynthesis of 3-methyl-Glu(12) (3mGlu(12)), and all recombinants produced novel lipopeptides. One of the compounds displayed very good antibacterial activity in the presence of bovine surfactant, which interacts with daptomycin or A54145E to inhibit their antibacterial activities.

Randomized Controlled Trial of Lung Lavage with Dilute Surfactant for Meconium Aspiration Syndrome

To evaluate whether lung lavage with surfactant changes the duration of mechanical respiratory support or other outcomes in meconium aspiration syndrome (MAS). We conducted a randomized controlled trial that enrolled ventilated infants with MAS. Infants randomized to lavage received two 15-mL/kg aliquots of dilute bovine surfactant instilled into, and recovered from, the lung. Control subjects received standard care, which in both groups included high frequency ventilation, nitric oxide, and, where available, extracorporeal membrane oxygenation (ECMO). Sixty-six infants were randomized, with one ineligible infant excluded from analysis. Median duration of respiratory support was similar in infants who underwent lavage and control subjects (5.5 versus 6.0 days, P = .77). Requirement for high frequency ventilation and nitric oxide did not differ between the groups. Fewer infants who underwent lavage died or required ECMO: 10% (3/30) compared with 31% (11/35) in the control group (odds ratio, 0.24; 95% confidence interval, 0.060-0.97). Lavage transiently reduced oxygen saturation without substantial heart rate or blood pressure alterations. Mean airway pressure was more rapidly weaned in the lavage group after randomization. Lung lavage with dilute surfactant does not alter duration of respiratory support, but may reduce mortality, especially in units not offering ECMO.

Physicochemical studies on the interaction of serum albumin with pulmonary surfactant extract in films and bulk bilayer phase

Functionality, structure and composition of the adsorbed films of bovine lipid extract surfactant (BLES), in the absence and presence of bovine serum albumin (BSA), at the air-buffer interface was characterized through surface tension, atomic force microscopy and time of flight secondary ion mass spectrometric methods. Gel and fluid domains of BLES films were found to be altered significantly in the presence of BSA. Differential scanning calorimetric studies on BLES dispersions in presence of BSA revealed that the perturbations of the lipid bilayer structures were significant only at higher amount of BSA. FTIR studies on the BLES dispersions in buffer solution revealed that BSA could affect the lipid head-group hydrations in bilayer as well as the methylene and methyl vibration modes of fatty acyl chains of the phospholipids present in BLES. Serum albumin could perturb the film structure at pathophysiological concentration while higher amount of BSA was required in perturbing the bilayer structures. The studies suggest a connected perturbed bilayer to monolayer transition model for surfactant inactivation at the alveolar-air interface in dysfunctional surfactants.