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.

Abstract. Biological aerosol particles affect human health, are essential for microbial- and gene dispersal, and have been proposed as important agents for atmospheric processes. However, the abundance and size distributions of atmospheric biological particles are largely unknown. In this study we used a laser-induced fluorescence instrument to measure fluorescent biological aerosol particle (FBAP) concentrations for 18 months (October 2020–April 2022) at a rural, forested site in Sweden. The aim of this study was to investigate FBAP number concentrations (NFBAP) over time and analyze their relationship to meteorological parameters. The NFBAP was highest in the summer and lowest in winter, exhibiting a ~3-fold difference between these seasons. The median NFBAP was 0.0050, 0.0025, 0.0027 and 0.0126 cm-3 in fall, winter, spring, and summer, respectively, and constituted ~0.1–0.5 % of the total supermicron particle number. The NFBAP were dominated by the smallest measured size fraction (1–3 µm), suggesting that the main portion of the biological particles measured were due to single bacterial cells, fungal spores, and bacterial agglomerates. The NFBAP were significantly correlated with increasing air temperature (P<0.01) in all seasons. For most of the campaign NFBAP was seen to increase with wind speed (P<0.01), while the relationship with relative humidity was for most part of the campaign nonsignificant (46 %) but to a large part (30 %) negative (P<0.05). Our results indicate that NFBAP were highest during warm and dry conditions when wind speeds were high, suggesting that a major part of the FBAP in the spring and summer were due to mechanical aerosol generation and release mechanisms. In the fall, relative humidity may have been a more important factor for bioaerosol release. This is one of the longest time series of atmospheric FBAP, which are highly needed for estimates of bioaerosol background concentrations in comparable regions.

IntroductionFirefighters have increased risk of chronic respiratory disease. Standard clinical techniques used in medical checkups may not detect the earliest microstructural changes in peripheral airways. A new technique called Airspace Dimension Assessment (AiDA) has been shown to enable early detection of emphysema in chronic obstructive pulmonary disease. This method may be useful in the occupational setting to detect early pulmonary changes and enable prevention.AimTo evaluate whether AiDA detects changes in the most peripheral airways of firefighters.MethodsAiDA, measuring the effective airspace radius (rAiDA) and zero-second recovery (R0), was used as a complement to other standardised lung function measures in 21 male firefighters and 16 age-matched male controls.ResultsThere were significant differences inrAiDAandR0between firefighters (meanrAiDA0.301 mm, standard deviation (sd) 0.024; meanR00.336 arbitrary units,sd0.116 and controls (meanrAiDA0.276 mm,sd0.044; meanR00.576 arbitrary units,sd0.168), p=0.03 and p<0.001, respectively. Higher forced vital capacity was found in firefighters (mean 101% of predicted) than in controls (mean 93% of predicted; p=0.03). No significant differences were found with regard to either the ratio between forced expiratory volume in 1 s and forced vital capacity or forced expiratory volume in 1 s. The majority of firefighters had diffusing capacity for carbon monoxide, oscillometry and single-breath nitrogen washout values within the normal ranges.ConclusionAiDA parameters can provide information on early pulmonary peripheral changes that may not be seen with standard techniques used in screening of pulmonary function.

Small dots represent individual 5 min data averages. The curve cutting through the NTAP data shows running 7-day median values of the NFBAP concentration. Vertical dashed lines indicate the first day of each season as identified by the Swedish meteorological and hydrological institute.

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