Effect of enhanced ultraviolet germicidal irradiation in the heating ventilation and air conditioning system on ventilator-associated pneumonia in a neonatal intensive care unit.

OBJECTIVE: The objective of this study was to test the hypothesis that enhanced ultraviolet germicidal irradiation (eUVGI) installed in our neonatal intensive care unit (NICU) heating ventilation and air conditioning system (HVAC) would decrease HVAC and NICU environment microbes, tracheal colonization and ventilator-associated pneumonia (VAP). STUDY DESIGN: The study was designed as a prospective interventional pre- and post-single-center study. University-affiliated Regional Perinatal Center NICU. Intubated patients in the NICU were evaluated for colonization, and a high-risk sub-population of infants <30 weeks gestation ventilated for ≥ 14 days was studied for VAP. eUVGI was installed in the NICU's remote HVACs. The HVACs, NICU environment and intubated patients' tracheas were cultured pre- and post-eUVGI for 12 months. The high-risk patients were studied for VAP (positive bacterial tracheal culture, increased ventilator support, worsening chest radiograph and ≥ 7 days of antibiotics). RESULT: Pseudomonas, Klebsiella, Serratia, Acinetobacter, Staphylococcus aureus and Coagulase-negative Staphylococcus species were cultured from all sites. eUVGI significantly decreased HVAC organisms (baseline 500,000 CFU cm(-2); P=0.015) and NICU environmental microbes (P<0.0001). Tracheal microbial loads decreased 45% (P=0.004), and fewer patients became colonized. VAP in the high-risk cohort fell from 74% (n=31) to 39% (n=18), P=0.04. VAP episodes per patient decreased (Control: 1.2 to eUVGI: 0.4; P=0.004), and antibiotic usage was 62% less (P=0.013). CONCLUSION: eUVGI decreased HVAC microbial colonization and was associated with reduced NICU environment and tracheal microbial colonization. Significant reductions in VAP and antibiotic use were also associated with eUVGI in this single-center study. Large randomized multicenter trials are needed.

Surface activity of a synthetic lung surfactant containing a phospholipase-resistant phosphonolipid analog of dipalmitoyl phosphatidylcholine.

Surface activity and sensitivity to inhibition from phospholipase A2 (PLA2), lysophosphatidylcholine (LPC), and serum albumin were studied for a synthetic C16:0 diether phosphonolipid (DEPN-8) combined with 1.5% by weight of mixed hydrophobic surfactant proteins (SP)-B/C purified from calf lung surfactant extract (CLSE). Pure DEPN-8 had better adsorption and film respreading than the major lung surfactant phospholipid dipalmitoyl phosphatidylcholine and reached minimum surface tensions <1 mN/m under dynamic compression on the Wilhelmy balance and on a pulsating bubble surfactometer (37 degrees C, 20 cycles/min, 50% area compression). DEPN-8 + 1.5% SP-B/C exhibited even greater adsorption and had overall dynamic surface tension lowering equal to CLSE on the bubble. In addition, films of DEPN-8 + 1.5% SP-B/C on the Wilhelmy balance had better respreading than CLSE after seven (but not two) cycles of compression-expansion at 23 degrees C. DEPN-8 is structurally resistant to degradation by PLA2, and DEPN-8 + 1.5% SP-B/C maintained high adsorption and dynamic surface activity in the presence of this enzyme. Incubation of CLSE with PLA2 led to chemical degradation, generation of LPC, and reduced surface activity. DEPN-8 + 1.5% SP-B/C was also more resistant than CLSE to direct biophysical inhibition by LPC, and the two were similar in their sensitivity to biophysical inhibition by serum albumin. These findings indicate that synthetic surfactants containing DEPN-8 combined with surfactant proteins or related synthetic peptides have potential utility for treating surfactant dysfunction in inflammatory lung injury.

Brimonidine formulation in polyacrylic acid nanoparticles for ophthalmic delivery.

In ocular drug delivery, a major problem is providing an adequate concentration of a therapeutic agent in the precorneal area. Mucoadhesive carriers such as polyacrylic acid in sub-colloidal, nanoparticulate form, have a strong potential for ophthalmic drug delivery. A formulation of brimonidine loaded in polyacrylic acid nanoparticles has been prepared for potential delivery in ophthalmic therapy. The particles were prepared by a reverse microemulsion polymerization technique and their sizes were in the range of 50 nm. In a preliminary biocompatibility test, Caco-2 cells (human primary colonic tumour adenocarcinoma) and human corneal epithelial cells incubated with polyacrylic acid nanoparticles were found to retain their viability over varying times. The loading efficiency of the drug brimonidine in the particles was shown to be between 80-85% and pH dependent. The bioadhesive polyacrylic hydrogel nanoparticles, used in the present study, exhibited superior loading properties for brimonidine, and the formulation was stable for more than 5 weeks. When the drug-loaded nanoparticles were dispersed in a phosphate buffer saline (pH = 7.4), the drug was slowly released over several hours. Two-photon laser scanning microscopic studies of dye-conjugated polyacrylic acid nanoparticles demonstrated the accumulation of the particles on the surface and intercellular spaces of Caco-2 cells.

Content-dependent activity of lung surfactant protein B in mixtures with lipids.

The content-dependent activity of surfactant protein (SP)-B was studied in mixtures with dipalmitoyl phosphatidylcholine (DPPC), synthetic lipids (SL), and purified phospholipids (PPL) from calf lung surfactant extract (CLSE). At fixed SP-B content, adsorption and dynamic surface tension lowering were ordered as PPL/SP-B approximately SL/SP-B > DPPC/SP-B. All mixtures were similar in having increased surface activity as SP-B content was incrementally raised from 0.05 to 0.75% by weight. SP-B had small but measurable effects on interfacial properties even at very low levels < or =0.1% by weight. PPL/SP-B (0.75%) had the highest adsorption and dynamic surface activity, approaching the behavior of CLSE. All mixtures containing 0.75% SP-B reached minimum surface tensions <1 mN/m in pulsating bubble studies at low phospholipid concentration (1 mg/ml). Mixtures of PPL or SL with SP-B (0.5%) also had minimum surface tensions <1 mN/m at 1 mg/ml, whereas DPPC/SP-B (0.5%) reached <1 mN/m at 2.5 mg/ml. Physiological activity also was strongly dependent on SP-B content. The ability of instilled SL/SP-B mixtures to improve surfactant-deficient pressure-volume mechanics in excised lavaged rat lungs increased as SP-B content was raised from 0.1 to 0.75% by weight. This study emphasizes the crucial functional activity of SP-B in lung surfactants. Significant differences in SP-B content between exogenous surfactants used to treat respiratory disease could be associated with substantial activity variations.

Component-specific surface and physiological activity in bovine-derived lung surfactants.

Composition, surface activity and effects on pressure-volume (P-V) mechanics are examined for lavaged calf lung surfactant (LS) and the clinical exogenous surfactants Infasurf and Survanta. Lavaged LS and Infasurf had closely-matching compositions of phospholipids and neutral lipids. Survanta had higher levels of free fatty acids and triglycerides consistent with its content of added synthetic palmitic acid and tripalmitin. Infasurf and Survanta both contained less total protein than LS because of extraction with hydrophobic solvents, but the total protein content relative to phospholipid in Survanta was about 45% lower than in Infasurf. This difference was primarily due to surfactant protein (SP)-B, which was present by ELISA at a mean weight percent relative to phospholipid of 1.04% in LS, 0.90% in Infasurf, and 0.044% in Survanta. Studies on component fractions separated by gel permeation chromatography showed that SP-B was a major contributor to the adsorption, dynamic surface activity, and P-V mechanical effects of Infasurf, which approached whole LS in magnitude. Survanta had lower adsorption, higher minimum surface tension, and a smaller effect on surfactant-deficient P-V mechanics consistent with minimal contributions from SP-B. Addition of 0.05% by weight of purified bovine SP-B to Survanta did not improve surface or physiological activity, but added 0.7% SP-B improved adsorption, dynamic surface tension lowering, and P-V activity to levels similar to Infasurf. The SP-B content of lung surfactants appears to be a crucial factor in their surface activity and efficacy in improving surfactant-deficient pulmonary P-V mechanics.

Concentration-dependent, temperature-dependent non-Newtonian viscosity of lung surfactant dispersions.

The bulk shear viscosities of aqueous dispersions of lavaged calf lung surfactant (LS) and its chloroform:methanol extract (CLSE) were measured as a function of concentration, shear rate and temperature. At 10-mg phospholipid per milliliter, dispersions of LS and vortexed CLSE in 0.15 M NaCl (saline) had low viscosities near 1 cp over a range of shear rates from 225 to 1125 s(-1). Lung surfactant viscosity increased with phospholipid concentration and became strongly non-Newtonian with higher values at low shear rates. At 37 degrees C and 40 mg/ml, LS and vortexed CLSE in saline had viscosities of 38 and 34 cp (77 s(-1)) and 12 and 7 cp (770 s(-1)), respectively. Viscosity values for LS and CLSE were dependent on temperature and, at fixed shear, were lower at 23 degrees C than at 37 or 10 degrees C. Hysteresis was also present in viscosity measurements depending on whether shear rate was successively increased or decreased during study. Addition of 5 mM Ca(2+) at 37 degrees C markedly reduced CLSE viscosity at all shear rates and decreased LS viscosity at low shear rates. Dispersion by sonication rather than vortexing increased the viscosity of CLSE at fixed shear, while synthetic phospholipids dispersed by either method had low, relatively Newtonian viscosities. The complex viscous behavior of dispersions of LS and CLSE in saline results from their heterogeneous aggregated microstructure of phospholipids and apoproteins. Viscosity is influenced not only by the aggregate surface area under shear, but also by phospholipid-apoprotein interactions and aggregate structure/deformability. Similar complexities likely affect the viscosities of biologically-derived exogenous surfactant preparations administered to patients in clinical surfactant therapy.

Myeloperoxidase activity as a lung injury marker in the lamb model of congenital diaphragmatic hernia.

PURPOSE: The antioxidant system is the primary intracellular defense system of the lung against oxygen toxicity (neutrophil sequestration). The CDH lamb model antioxidant system is deficient. It is hypothesized that pulmonary neutrophil sequestration may play a part in the acute lung injury of CDH patients. Myeloperoxidase (MPO) is a major constituent of neutrophil cytoplasmic granules and its activity therefore is a direct measure of neutrophil presence and an indirect indicator of lung injury. METHODS: Eight lambs had left-sided diaphragmatic hernias surgically created at 80 days' gestation and were delivered by cesarean section at 140 to 145 days. Eight littermate lambs served as controls. Lambs were either killed before ventilation or were ventilated conventionally for 4 hours with 100% O(2) and then killed. The lungs were dissected en bloc and snap frozen. The samples were homogenized, sonicated, freeze-thawed, and separated by density centrifugation. Supernatants were analyzed for myeloperoxidase (MPO) activity by spectrophotometry with o-dianisidine dihydrochloride and hydrogen peroxide at 460 nm. The MPO activity was normalized to the protein content of the supernatant and expressed as units of MPO activity per milligram of protein. RESULTS: There was significantly more MPO activity in the CDH-ventilated lungs than controls similarly ventilated (3,203 +/- 665 versus 1,220 +/- 194, P =.001). There was no difference in MPO activity between the CDH and control lungs (318 +/- 57 v 348 +/- 61; P =.5). There was no difference between right and left lungs in any group. CONCLUSION: Ventilation and hyperoxia leads to neutrophil accumulation in lung tissue, which is most pronounced in the CDH lung tissue. This is a further clue to the pathophysiology of iatrogenic lung injury in CDH. The myeloperoxidase assay may now be used to evaluate antenatal or postnatal antioxidant therapies for iatrogenic lung injury in CDH.

Upregulation of keratinocyte growth factor in the tracheal ligation lamb model of congenital diaphragmatic hernia.

PURPOSE: Congenital diaphragmatic hernia (CDH) carries a high mortality rate of 60% because of associated anomalies, pulmonary hypoplasia, pulmonary hypertension, and type II cell dysfunction. Prenatal tracheal ligation has been shown to improve lung growth in experimental models. This could be caused by a direct effect of increased endothoracic pressure in utero, secondary to the induction of specific growth factors, or both. Keratinocyte growth factor (KGF) is involved in normal lung organogenesis and is a potent mitogen of alveolar type II cells. The authors have therefore investigated the protein and mRNA levels of keratinocyte growth factor in the lung tissue of control, CDH, and CDH tracheal ligation lambs. METHODS: Eight lambs had left-sided diaphragmatic hernias surgically created at 80 days' gestation. Tracheal ligation was performed at 110 days in 4 lambs, and they were delivered by cesarean section at 140 to 145 days. Twin littermates served as controls. The lungs were dissected en bloc and snap frozen. KGF protein levels were determined by ELISA. Total RNA was isolated, and a RNase protection assay was performed using an ovine cDNA probe for KGF, and a human cDNA probe for GAPDH (house keeping control). Densitometric analysis was used to quantify the relative amounts of mRNA in each sample. RESULTS: There was a significant decrease in the KGF protein levels of the CDH samples (110 v 73.2 pg/mg protein, P =.02). This decrease was mirrored by a significant fall in the level of mRNA expression for KGF (0.694 v 0.235, P = .02). Tracheal ligation normalized the KGF protein levels (96.1 pg/mg protein). This elevation of KGF protein was accompanied by an upregulation of KGF gene expression to control levels (0.56). CONCLUSIONS: Tracheal ligation clearly is accompanied by an upregulation of keratinocyte growth factor protein and gene expression. It is not yet clear whether keratinocyte growth factor is solely responsible for the growth observed in these tracheal ligation preparations. Further growth factor blocking experiments are required.

Acid aspiration increases sensitivity to increased ambient oxygen concentrations.

Previously we have demonstrated that prolonged exposure to 100% ambient oxygen leads to a marked loss in functional lung volume and lung compliance, hypoxemia, and surfactant system abnormalities similar to acute respiratory distress syndrome (ARDS). However, 50% oxygen administration is believed to be safe in most clinical settings. In the present study, we have evaluated the effects of a 24-h exposure to 50% oxygen in rabbits immediately following experimental gastric acid aspiration. Mild hypoxemia, but no changes in mortality, lung volume, lung compliance, surfactant metabolism, or edema formation occurred after 24 h of normoxia postacid aspiration. Conversely, a relatively short (24-h) exposure to 50% oxygen after acid aspiration results in increased pulmonary edema, physical signs of respiratory distress, and mortality, as well as decreased arterial oxygenation, lung volume, lung compliance, and type II alveolar cell surfactant synthesis. These results suggest that acid aspiration alters the "set point" for oxygen toxicity, possibly by "priming" cells through activation of inflammatory pathways. This pathogenic mechanism may contribute to the progression of aspiration pneumonia to ARDS.

Multiple mechanisms of lung surfactant inhibition.

We studied the mechanisms by which C16:0 lysophosphatidylcholine (LPC) and albumin inhibit the surface activity of calf lung surfactant extract (CLSE) by using a pulsating bubble apparatus with a specialized hypophase exchange system, plus adsorption and Wilhelmy balance measurements. In the absence of inhibitors, CLSE (1 mg phospholipid/mL) reached minimum surface tension (gamma(min)) < 1 mN/m within 5 min of bubble pulsation at 20 cycles/min at 37 degrees C. Mixtures of CLSE:LPC had impaired surface activity depending on LPC content: gamma(min) was raised to 5 mN/m by 14 wt % LPC, to 15 mN/m by 25-30 wt% LPC, and to >20 mN/m (67 wt % LPC), even at high CLSE concentrations (3 and 6 mg phospholipid/mL). In contrast, inhibition of CLSE by albumin was more easily abolished when surfactant concentration was raised. Mixtures of albumin (3 mg/mL) and CLSE (1 mg phospholipid/mL) had gamma(min) >20 mN/m, but normal values of gamma(min) < 1 mN/m were reached at higher CLSE concentration (3 mg phospholipid/mL) even when albumin concentration was increased 8-fold to 24 mg/mL. In hypophase exchange studies, LPC, but not albumin, was able to penetrate preformed CLSE surface films and raise gamma(min) CLSE surface films with gamma(min) < 1 mN/m were isolated by an initial hypophase exchange with saline, and a second exchange with an LPC-containing hypophase raised gamma(min) to approximately 10 mN/m. CLSE surface films retained the ability to reach gamma(min) < 1 mN/m in analogous hypophase exchange studies with albumin. The ability of LPC to penetrate surface films of CLSE, although albumin could not, was also demonstrated in adsorption experiments in a Teflon dish, where diffusion was minimized by subphase stirring. Wilhelmy balance experiments also demonstrated that LPC could mix and interact with CLSE or dipalmitoyl phosphatidylcholine in solvent-spread surface films. The ability of LPC or other cell membrane lipids to penetrate interfacial films and raise gamma(min) even at high surfactant concentration may increase their inhibitory actions during acute lung injury.

Tracheal ligation and mechanical ventilation do not improve the antioxidant enzyme status in the lamb model of congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: The antioxidant enzyme (AOE) system is the primary intracellular defense system of the lung against oxygen toxicity. The authors recently demonstrated depressed levels of catalase, glutathione peroxidase, and superoxide dismutase in congenital diaphragmatic hernia (CDH) lambs compared with controls. The aim of this study was to determine whether tracheal ligation (TL) or mechanical ventilation (recently shown to stimulate growth and surfactant metabolism, respectively) could induce an elevation in AOE activity. METHODS: Four nonventilated lambs with surgically created CDH and TL and five CDH lambs ventilated for 4 hours were studied. Lung tissue was analyzed for AOE and the results compared with untreated CDH lambs. RESULTS: Both ventilation and TL failed to elevate AOE activity above that of untreated CDH lambs. CONCLUSIONS: The data provide further evidence that TL does not improve lung metabolism or maturation. Mechanical ventilation, which often involves high oxygen delivery, is a necessary and often beneficial therapeutic modality. In the CDH neonate compromised not only by low baseline levels of the AOE, but also by an inability to induce enzyme synthesis in response to hyperoxia, mechanical ventilation may, by causing lung injury, be contributing to the high morbidity and mortality rate associated with CDH.

Lung physiological and metabolic changes in lambs with congenital diaphragmatic hernia after administration of prenatal maternal corticosteroids.

BACKGROUND/PURPOSE: Improved outcomes of preterm infants born to mothers treated prenatally with corticosteroids have been documented. The authors investigated the role of prenatal maternal corticosteroid therapy in congenital diaphragmatic hernia (CDH). METHODS: Five CDH lambs of ewes given 0.5 mg/kg betamethasone intravenously 24 hours before delivery (single-dose), four CDH lambs of ewes similarly dosed at 48 and 24 hours before delivery (double-dose), five untreated CDH lambs and five control lambs were studied. After 2 hours of ventilation, compliance, arterial oxygen (PO2) and carbon dioxide (pCO2) concentrations were recorded. Lavage protein and phospholipid levels were measured, and lung tissue was analyzed for antioxidant enzyme activity (AOE). RESULTS: No improvement in gas exchange was noted in either treatment group. Significant increases in compliance (P = .02) were noted in the double-dose steroid group, which were different from that of untreated CDH lambs or controls. Minimal changes in AOE activities were seen with steroid administration. CONCLUSIONS: Although the metabolic changes were not significant, the marked improvement in compliance seen in the double-dosed steroid group suggests a potential role for prenatal maternal corticosteroids in CDH. Further timing and dosage studies are warranted in this model.

Regional pulmonary blood flow during partial liquid ventilation in normal and acute oleic acid-induced lung-injured piglets.

OBJECTIVE: To determine the spatial distribution of pulmonary blood flow in three groups of piglets: partial liquid ventilation in normal piglets, partial liquid ventilation during acute lung injury, and conventional gas ventilation during acute lung injury. DESIGN: Prospective randomized study. SETTING: A university medical school laboratory approved for animal research. SUBJECTS: Neonatal piglets. INTERVENTIONS: Regional pulmonary blood flow was studied in 21 piglets in the supine position randomized to three different groups: a normal group that received partial liquid ventilation (Normal-PLV) and two acute lung injury groups that received an oleic acid-induced lung injury: partial liquid ventilation during acute lung injury (OA-PLV) and conventional gas ventilation during acute lung injury (OA-Control). Acute lung injury was induced by infusing oleic acid (0.15 mL/kg iv) over 30 mins. Partial liquid ventilation was instituted with perflubron (LiquiVent, 30 mL/kg) after 30 mins in the Normal-PLV and OA-PLV groups. MEASUREMENTS AND MAIN RESULTS: Arterial and venous blood gases, hemodynamics, and pulmonary mechanics were measured every 15 mins throughout the hour-long study. Pulmonary blood flow was assessed by fluorescent microsphere technique at baseline and after 30, 45, and 60 mins. In the Normal-PLV piglets, pulmonary blood flow decreased from baseline (before injury or partial liquid ventilation) in the most dependent areas of the lung (F ratio = 3.227; p < .001). In the OA-PLV piglets, pulmonary blood flow was preserved over time throughout the lung (F ratio = 1.079; p = .38). In the OA-Control piglets, pulmonary blood flow decreased in the most dependent areas of the lung and increased from baseline in less dependent slices over time (F ratio = 2.48; p = .003). CONCLUSIONS: The spatial distribution of regional pulmonary blood flow is preserved during partial liquid ventilation compared with gas ventilation in oleic acid-induced lung injury.

Reactive oxygen species contribute to oxygen-related lung injury after acid aspiration.

UNLABELLED: Hyperoxia increases pulmonary damage after acid aspiration. We hypothesize that free radicals play a role in acute lung injury. To examine this hypothesis, we injured rats by intratracheal instillation of acidic isotonic sodium chloride solution (NS) (pH 1.25); NS + gastric particles (particle pH 5.3); or acid + particles (pH 1.25). Animals were exposed to 98% oxygen or air for 5 h. Superoxide (HO2) generation was measured in either an aliquot of white blood cells (WBCs) recovered from bronchoalveolar lavage (BAL) or from blood. Lungs were analyzed for thiobarbituric acid-reactive substances (TBARS) and carbonylated proteins. The antioxidant capacity was measured using a 2-2'-azo-bis-amidinopropane hydrochloride neutralizing assay. Generation of HO2 by WBCs in peripheral blood was greater in animals exposed to 98% O2 (89.8 +/- 12.5 U. min-1.10(5) neutrophils) compared with air exposure (37.5 +/- 9.2 U.min-1.10(5) neutrophils) after combined injury (P < 0.05). Similarly, HO2 generation by WBCs retrieved from BAL was higher in oxygen-exposed rats (987.74 +/- 128 U.min-1.10(5) WBC) compared with air-exposed animals after an identical injury (348 +/- 9.2 U. min-1.10(5) WBC) (P < 0.05). TBARS and carbonylated protein levels in the lungs of oxygen-exposed animals (587.9 +/- 58.6 and 55.8 +/- 3.1 pmol/mg of protein, respectively) were higher than those in air-exposed rats after combined injury (342.8 +/- 15.1 and 28.6 +/- 4.6 pmol/mg of protein, respectively) and compared with air-exposed uninjured rats (340.6 +/- 9.8 and 18.3 +/- 2.8 pmol/mg of protein, respectively; P < 0.01). Antioxidant capacity decreased in acid and combined injury groups (2.41 +/- 0.13 min and 1.94 +/- 0.15 min, respectively) compared with the uninjured group after 5 h of exposure to 98% oxygen (4.85 +/- 0.19 min; P < 0.01). We demonstrated evidence of increased oxidant activity on lipids and proteins in injured lungs after oxygen exposure. The decrease in antioxidant capacity after low pH aspiration with exposure to hyperoxia may contribute to this increase. IMPLICATIONS: Oxygen administration results in a lung pathology known as oxygen toxicity. This effect is usually not significant if the duration of exposure is limited to < 24 h. In the presence of acute inflammatory lung injury, exposure to hyperoxia results in lung damage in a shorter time. We demonstrate that sufficiently decreased lung antioxidant reserve capacity may be accountable for this early toxicity.

Contractile properties of intralobar pulmonary arteries and veins in the fetal lamb model of congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Pulmonary hypertension plays a significant role in the pathophysiology of congenital diaphragmatic hernia (CDH). Although there has been an intensive research effort directed at mediators that may cause pulmonary vasoconstriction, no single agent has been identified. The authors hypothesize that there may be an alteration in the cGMP-nitric oxide (NO) pathway of vasodilatation contributing to the pulmonary hypertension observed in CDH. The purpose of these studies is to begin to elucidate vasoactive properties of pulmonary vessels with particular attention to the cGMP-NO pathway of vasodilatation in fetal lambs with CDH. METHODS: Fourth-generation pulmonary arteries and pulmonary veins were dissected from both right and left lungs of eight, 139-day gestational fetuses with surgically created CDH. Vessels were studied with standard isolated tissue bath techniques. Experiments examined basal release of NO in endothelium-intact PVs and PAs of both right and left lungs by measuring the contractile force of vessels constricted with norepinephrine (NE) in the presence and absence of the nitric oxide synthase (NOS) inhibitor N(omega)-nitro-L-arginine (L-NA). Concentration-response curves to the vasodilating agents zaprinast and A23187 were also obtained in vessels contracted by NE. RESULTS: Left and right pulmonary artery responses to NE are enhanced over those of historic controls. Pretreatment of left pulmonary arteries with L-NA enhances the vasoconstrictor response to NE, whereas right PAs show no increased response. Relaxation responses to A23187 and zaprinast, in both left and right pulmonary arteries were not different from control lambs. Relaxation responses of both left and right pulmonary veins to A23187 and zaprinast are blunted compared with controls. This blunting is significantly more in left pulmonary veins than right. Further, right but not left pulmonary veins display enhanced vasoconstrictive response to NE after L-NA pretreatment. CONCLUSIONS: The NO-cGMP pathway of vasodilatation is abnormal in the near term, fetal lamb with CDH. These abnormalities were most apparent in pulmonary veins and may reflect abnormal NOS activity or content between left and right lungs of the fetal lamb with CDH. Pulmonary arteries from CDH lambs have basal and stimulated NO release equal to that of historic controls but appear to be hypersensitive to exogenous vasoconstrictors.

Alveolar vascularization of the lung in a lamb model of congenital diaphragmatic hernia.

Pulmonary hypoplasia and pulmonary hypertension are factors limiting the survival of infants with congenital diaphragmatic hernia (CDH). A reduction in the number of pre-acinar pulmonary vessels and increased muscularization are the structural lesions implicated as causes of irreversible hypoxemia. Whether there is a reduction in the number of air-blood barriers, which represent the capillary surface area of the lung involved in gas exchange, is unknown. We sought to determine if the lungs of CDH lambs have: (1) a reduction in total capillary surface area proportionate to the reduction in the total alveolar surface area of the lung; and/or (2) a disproportionate reduction in the number of capillaries (air blood barriers) within each acinus. The latter measurement was determined by calculating the capillary load which we defined as the number of air blood barriers/unit of surface density. At 80 d gestation (pseudoglandular period), a diaphragmatic hernia was created surgically in one lamb fetus of a twin gestation. At term, the fetuses were removed, the chests opened and the lungs fixed by a tracheal infusion of 1.5% glutaraldehyde at 25 cm of water pressure. Tissues from the lower lobes were examined by light and electron microscopy. Using computerized interactive morphometry, alveolar and capillary surface area, and capillary load were determined by intersection and point counting for the right and left lungs. The data show that the total alveolar surface area of the left CDH and control lungs were 1.8 +/- 0.8 m2 and 6.1 +/- 1.1 m2 (p < 0.01), respectively, and for the right CDH and control lungs 2.5 m2 +/- 0.1 and 11.2 +/- 1.9 m2 (p < 0.01), respectively. The total capillary surface area for the left CDH and control lungs were 0.7 +/- 0.3 m2 and 2.8 +/- 1.2 m2 (p < 0.05), respectively, and for the right CDH and control lungs 0.9 +/- 0.3 m2 and 3.8 +/- 1.5 m2 (p < 0.05), respectively. The capillary load was not statistically different. These findings demonstrate that the lungs in CDH are deficiently vascularized at the alveolar surface due to a reduction in the total alveolar surface area. Each acinus contains the same number of air blood barriers per unit of alveolar surface area indicating a normal acinar composition.

Dysfunction of guinea-pig pulmonary surfactant and type II pneumocytes after repetitive challenge with aerosolized ovalbumin.

BACKGROUND: Asthma symptoms may partially be caused by a surfactant dysfunction. The inflammatory reaction, so characteristic of asthma, involves a protein invasion of airways which harmfully affects the surfactant function. However, mild asthma attacks might also impede the surfactant synthesis in alveolar type II cells. OBJECTIVE: The present study evaluates the hypothesis that type II pneumocyte metabolic function might be disturbed in a model of mild asthma. METHODS: Immunized, as well as not immunized control guinea-pigs, were challenged three times at two-day intervals with 0.04% ovalbumin aerosol. Bronchoalveolar lavage (BAL) was performed one day after the last challenge and the fluid was evaluated for surface activity, and content of phospholipids and proteins. Alveolar type II cells were isolated and their ability to incorporate a 3H labeled surfactant precursor was evaluated. RESULTS: BAL fluid from immunized and challenged animals showed less surface activity (P < 0.01) when compared with BAL fluid from controls, not immunized but challenged. Most likely the reduced surface activity was caused by a 74% increase in the protein concentration (P < 0.05). Isolated type II cells from immunized and challenged animals had 33% less phospholipids than cells from controls (P < 0.05), and phosphatidylcholine synthesis was reduced 35% (P < 0.05). CONCLUSION: These results suggest that the synthesis, intra-cellular storage, and biophysical activity of surfactant are decreased in an intermittent and mild form of asthma.