Airspace dimension assessment with nanoparticles as a proposed biomarker for emphysema

Airspace dimension assessment with nanoparticles (AiDA) is a novel method to measure distal airspace radius non-invasively. In this study, AiDA radii were measured in 618 individuals from the population-based Swedish CArdiopulmonary BioImaging Study, SCAPIS. Subjects with emphysema detected by computed tomography were compared to non-emphysematous subjects. The 47 individuals with mainly mild-to-moderate visually detected emphysema had significantly larger AiDA radii, compared with non-emphysematous subjects (326±48 µm vs 291±36 µm); OR for emphysema per 10 µm: 1.22 (1.13–1.30, p<0.0001). Emphysema according to CT densitometry was similarly associated with larger radii compared with non-emphysematous CT examinations (316±41 µm vs 291 µm±26 µm); OR per 10 µm: 1.16 (1.08–1.24, p<0.0001). The results are in line with comparable studies. The results show that AiDA is a potential biomarker for emphysema in individuals in the general population.

Standardization of Methods for Sampling the Distal Airspace in Mechanically Ventilated Patients using Heat Moisture Exchange Filter Fluid

Non-invasive sampling of the distal airspace in patients with Acute Respiratory Distress Syndrome (ARDS) has long eluded clinical and translational researchers. We recently reported that fluid collected from Heat Moisture Exchange filters (HME) closely mirrors fluid directly aspirated from the distal airspace. In the current study, we sought to determine fluid yield from different HME types, optimal HME circuit dwell time and reliability of HME fluid in reflecting the distal airspace. We studied fluid yield from 4 different filter types by loading increasing volumes of saline and measuring volume of fluid recovered. We collected filters after 1, 2 and 4 hours of dwell time for measurement of fluid volume and total protein from 13 subjects. After identifying 4 hours as the optimal dwell time, we measured total protein and IgM in HME fluid from 42 subjects with ARDS and 9 with hydrostatic pulmonary edema (HYDRO). We found that the fluid yield varies greatly by filter type. With timed sample collection, fluid recovery increased with increasing circuit dwell time with a median volume of 2.0 mL (IQR 1.2-2.7) after 4 hours. Total protein was higher in the 42 subjects with ARDS compared to 9 with HYDRO (median 708 µg/ml (IQR 244-2017) vs 364 µg/ml (IQR 136-578), p=0.047) confirming that total protein concentration in HME is higher in ARDS compared to hydrostatic edema. These studies establish a standardized HME fluid collection protocol and confirm that HME fluid analysis is a novel non-invasive tool for study of the distal airspace in ARDS.

Airspace Dimension Assessment (AiDA) by inhaled nanoparticles: benchmarking with hyperpolarised 129Xe diffusion-weighted lung MRI

Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. Airspace Dimension Assessment with inhaled nanoparticles (AiDA) is a new method developed for in vivo measurement of distal airspace dimensions. The aim of this study was to benchmark the AiDA method against quantitative measurements of distal airspaces from hyperpolarised 129Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI). AiDA and 129Xe DW-MRI measurements were performed in 23 healthy volunteers who spanned an age range of 23–70 years. The relationship between the 129Xe DW-MRI and AiDA metrics was tested using Spearman’s rank correlation coefficient. Significant correlations were observed between AiDA distal airspace radius (rAiDA) and mean 129Xe apparent diffusion coefficient (ADC) (p < 0.005), distributed diffusivity coefficient (DDC) (p < 0.001) and distal airspace dimension (LmD) (p < 0.001). A mean bias of − 1.2 µm towards rAiDA was observed between 129Xe LmD and rAiDA, indicating that rAiDA is a measure of distal airspace dimension. The AiDA R0 intercept correlated with MRI 129Xe α (p = 0.02), a marker of distal airspace heterogeneity. This study demonstrates that AiDA has potential to characterize the distal airspace microstructures and may serve as an alternative method for clinical examination of the lungs.

Assessment of a Novel Method for Non-invasive Sampling of the Distal Airspace in Acute Respiratory Distress Syndrome Patients Receiving Inhaled Sedation with Sevoflurane: the ANAISS Study Protocol

ABSTRACTIntroductionRecently, fluid collected from the heat-and-moisture-exchange filters, which are commonly used in most mechanically ventilated patients under intravenous sedation, has been reported as a potential surrogate for fluid in the distal airspace. Therefore, collection of this fluid represents a promising, non-invasive method for sampling the distal airspace in patients with acute respiratory distress syndrome (ARDS) and for facilitating a mechanistic understanding of this devastating disease. The current study protocol was constructed to assess whether this fluid could be sampled from a dedicated device (Anaesthetic Conserving Device [AnaConDa-S], Sedana Medical, Danderyd, Sweden) used to deliver inhaled sevoflurane for sedation in patients with ARDS.Methods and analysisA total of 30 adult patients within 24 hours of meeting the Berlin criteria for moderate-severe ARDS and receiving inhaled sevoflurane as standard sedation in participating centres will be eligible for inclusion into this investigator-initiated, exploratory, prospective, bicentre study. After at least 12 h of inhaled sedation, a sample of directly aspirated, undiluted pulmonary oedema fluid will be collected concurrently with fluid from the AnaConDa-S device. Levels of proinflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α and sTNFr-1) and markers of lung endothelial (Ang-2) and epithelial (sRAGE) injury will be measured in both fluids by Multiplex. The primary endpoint is the correlation between protein markers (IL-1β, IL-6, IL-8, TNF-α, sTNFr-1, Ang-2 and sRAGE) measured in the undiluted pulmonary oedema fluid versus the AnaConDa-S fluid.Ethics and disseminationThe study was approved by the appropriate ethics committee (CPP Est I). Informed consent is required. The fluid collection from the AnaConDa-S has potential to foster our understanding of the potential effects of inhaled sedation in clinical ARDS and to open up novel perspectives for prognostic and predictive enrichment in future trials. The results will be published in a peer-reviewed journal.Registration numberNCT03964155.

Former-preterm lambs have persistent alveolar simplification at 2 and 5 months corrected postnatal age

Preterm birth and mechanical ventilation (MV) frequently lead to bronchopulmonary dysplasia, the histopathological hallmark of which is alveolar simplification. How developmental immaturity and ongoing injury, repair, and remodeling impact completion of alveolar formation later in life is not known, in part because of lack of suitable animal models. We report a new model, using former-preterm lambs, to test the hypothesis that they will have persistent alveolar simplification later in life. Moderately preterm lambs (~85% gestation) were supported by MV for ~6 days before being transitioned from all respiratory support to become former-preterm lambs. Results are compared with term control lambs that were not ventilated, and between males (M) and females (F). Alveolar simplification was quantified morphometrically and stereologically at 2 mo (4 M, 4 F) or 5 mo (4 M, 6 F) corrected postnatal age (cPNA) compared with unventilated, age-matched term control lambs (4 M, 4 F per control group). These postnatal ages in sheep are equivalent to human postnatal ages of 1–2 yr and ~6 yr, respectively. Multivariable linear regression results showed that former-preterm lambs at 2 or 5 mo cPNA had significantly thicker distal airspace walls ( P < 0.001 and P < 0.009, respectively), lower volume density of secondary septa ( P < 0.007 and P < 0.001, respectively), and lower radial alveolar count ( P < 0.003 and P < 0.020, respectively) compared with term control lambs. Sex-specific differences were not detected. We conclude that moderate preterm birth and MV for ~6 days impedes completion of alveolarization in former-preterm lambs. This new model provides the opportunity to identify underlying pathogenic mechanisms that may reveal treatment approaches.