Persurf, a new method to improve surfactant delivery: a study in surfactant depleted rats

Functional morphometry to estimate the alveolar surface area using a premature baboon model

The main respiratory pathophysiological process following premature birth is the delayed or arrested alveolar development that translates to a smaller alveolar surface area (S_A). Histological morphometry is the gold standard method to measure the S_A but requires invasive tissue sampling or the removal of the whole organ for analysis. Alternatively, the S_A could be measured in living subjects by "functional morphometry" using Fick's first law of diffusion and noninvasive measurements of the ventilation to perfusion ratio (V̇a/Q̇). We herein aim to describe a novel functional morphometric method to measure S_A using a premature baboon model. We used both functional morphometry and postmortem histological morphometry to measure S_A in 11 premature baboons born at 135 days who received intensive care treatment for 14 days. For the calculation of the S_A by functional morphology, we measured the septal wall thickness using microscopy, the alveolar arterial oxygen gradient using concurrent measurements of arterial pressure of O₂ and CO₂, and pulmonary perfusion using echocardiography and integrated Doppler signals. The median [interquartile range (IQR)] S_A using functional morphometry was 3,100 (2,080-3,640) cm² and using histological morphometry was 1,034 (634-1,210) cm² (left lung only). The S_A measured by functional morphometry was not related to the S_A measured by histological morphometry. Following linear regression analysis, the V̇a/Q̇ significantly predicted the histologically measured S_A (R² = 0.659, P = 0.002). In conclusion, functional measurements of ventilation to perfusion ratio could be used to estimate the alveolar surface area in prematurely born baboons and the ventilation perfusion ratio was the main determinant of the alveolar surface area.NEW & NOTEWORTHY The main morphological characteristic of chronic respiratory disease in prematurely born infants is the impaired/arrested alveolar growth that corresponds to a smaller aggregated alveolar surface area (S_A). This decreased S_A might be the limiting factor later in life affecting exercise capacity and quality of life. There is paucity of sensitive, noninvasive biomarkers to monitor the evolution of neonatal respiratory disease. Our noninvasive functional morphometric S_A might help to bridge the gap between pathophysiology and clinical monitoring.

Ferroptosis is Involved in Hyperoxic Lung Injury in Neonatal Rats

Purpose

To evaluate whether ferroptosis is involved in hyperoxic acute lung injury (HALI) and its mechanisms through the HALI model.

Methods

HE staining was used to assess lung injury pathology after the establishment of neonatal rat HALI model. ELISA was used to detect ROS, GPX4, and GSH expression. Prussian blue staining and Western Blot were used to detect iron deposition and the expression of ferroptosis-related proteins, respectively.

Results

The HALI group showed pathological changes with larger and fewer alveoli and thicker alveolar septa after HE staining. Prussian blue staining detected significant iron deposition in the lung tissue of the HALI group. GPX4, GSH, GSS, and SLC7A11 expressions were significantly decreased in the HALI group than in the normal control group. In contrast, ROS, TFRC, FHC, and FLC expressions showed opposite results (p<0.05).

Conclusion

Ferroptosis may be involved in the pathological process of hyperoxic lung injury in neonatal rats.

Experimental Evaluation of Perfluorocarbon Aerosol Generation with Two Novel Nebulizer Prototypes

The potential of non-invasive ventilation procedures and new minimally invasive techniques has resulted in the research of alternative approaches as the aerosolization for the treatment of respiratory distress syndrome (RDS). The aim of this work was to design two nebulizer prototypes and to evaluate them studying the particle size distribution of the inhaled droplets generated with distilled water and two perfluorocarbons (PFCs). Different experiments were performed with driving pressures of 1–3 bar for each compound. An Aerodynamic Particle Sizer was used to measure the aerodynamic diameter (Da), the mass median aerodynamic diameter (MMAD) and the geometric standard deviation (GSD). The results showed that both prototypes produced heterodisperse aerosols with Da mean values in all cases below 5 µm. The initial experiments with distilled water showed MMAD values lower than 9 µm and up to 15 µm with prototype 1 and prototype 2, respectively. Regarding the PFCs, relatively uniform MMAD values close to 12 µm were achieved. The air delivery with outer lumens of prototype 1 presented more suitable mass distribution for the generation and delivery of a uniform aerosol than the two half-circular ring geometry proposed in the prototype 2.

Experimental and Numerical Modeling of Aerosol Delivery for Preterm Infants

Respiratory distress syndrome (RDS) represents one of the major causes of mortality among preterm infants, and the best approach to treat it is an open research issue. The use of perfluorocarbons (PFC) along with non-invasive respiratory support techniques has proven the usefulness of PFC as a complementary substance to achieve a more homogeneous surfactant distribution. The aim of this work was to study the inhaled particles generated by means of an intracorporeal inhalation catheter, evaluating the size and mass distribution of different PFC aerosols. In this article, we discuss different experiments with the PFC perfluorodecalin (PFD) and FC75 with a driving pressure of 4–5 bar, evaluating properties such as the aerodynamic diameter (D_a), since its value is directly linked to particle deposition in the lung. Furthermore, we develop a numerical model with computational fluid dynamics (CFD) techniques. The computational results showed an accurate prediction of the airflow axial velocity at different downstream positions when compared with the data gathered from the real experiments. The numerical validation of the cumulative mass distribution for PFD particles also confirmed a closer match with the experimental data measured at the optimal distance of 60 mm from the catheter tip. In the case of FC75, the cumulative mass fraction for particles above 10 µm was considerable higher with a driving pressure of 5 bar. These numerical models could be a helpful tool to assist parametric studies of new non-invasive devices for the treatment of RDS in preterm infants.

Graphene oxide-stabilized perfluorocarbon emulsions for controlled oxygen delivery

Perfluorocarbon (PFC) emulsions are capable of absorbing large quantities of oxygen. They are widely used as blood alternates for quick oxygenation of tissues. However, they are unsuitable for applications where sustained oxygen supply is desired over an extended period of time. Here, we have designed a new PFC oxygen delivery system that combines perfluorodecalin with graphene oxide (GO), where GO acts both as an emulsifier and a stabilizing agent. The resulting emulsions (PFC@GO) release oxygen at least one order of magnitude slower than emulsions prepared with other common surfactants. The release rate can be controlled by varying the thickness of the GO layer. Controlled release of oxygen make these emulsions excellent oxygen carriers for applications where sustained oxygen delivery is required e.g. in tissue regeneration and vascular wound healing.

Overcoming inactivation of the lung surfactant by serum proteins: a potential role for fluorocarbons?

In many pulmonary conditions serum proteins interfere with the normal adsorption of components of the lung surfactant to the surface of the alveoli, resulting in lung surfactant inactivation, with potentially serious untoward consequences. Here, we review the strategies that have recently been designed in order to counteract the biophysical mechanisms of inactivation of the surfactant. One approach includes protein analogues or peptides that mimic the native proteins responsible for innate resistance to inactivation. Another perspective uses water-soluble additives, such as electrolytes and hydrophilic polymers that are prone to enhance adsorption of phospholipids. An alternative, more recent approach consists of using fluorocarbons, that is, highly hydrophobic inert compounds that were investigated for partial liquid ventilation, that modify interfacial properties and can act as carriers of exogenous lung surfactant. The latter approach that allows fluidisation of phospholipid monolayers while maintaining capacity to reach near-zero surface tension definitely warrants further investigation.