Airway monitoring by collection and mass spectrometric analysis of exhaled particles

Studying drug excretion into exhaled breath aerosol - A workflow based on an impaction sampling device and LC-HRMS/MS analysis

BACKGROUND

Exhaled breath (EB) aerosol was in principle shown to be a suitable matrix for bioanalysis of volatile but also non-volatile compounds. This attracted particular interest in the field of drug analysis. However, a big gap still exists in the understanding how and which drugs and/or their metabolites are excreted into exhaled breath and could thus actually be detected. The current study aimed to develop an analytical workflow for the qualitative detection of non-volatile drugs in EB aerosol microparticles.

RESULTS

The analyte selection covered different drug classes such as antihypertensives, anticonvulsants or opioid analgesics to investigate and understand the excretion of drugs and their metabolites into EB aerosol. A device for collecting aerosol particles from the lung through impaction was used for the non-invasive sampling procedure. Three expiration cycles per participant and device were collected. The sample preparation consisted of a collector extraction with methanol. Qualitative method development and validation were performed using reversed-phase liquid chromatography (LC) coupled to orbitrap-based high-resolution mass spectrometry (HRMS). Qualitative method validation was done according to published recommendations and international guidelines. Parameters such as selectivity, carry-over, limits of detection and identification, recovery, matrix effects, and long-term stability were evaluated. The limits of detection ranged from 100 pg/collector to 10,000 pg/collector. The procedure was finally used to analyze a total of 31 patient EB samples and demonstrated that e.g., tilidine and its metabolite nortilidine as well as tramadol and its active metabolite O-desmethyltramadol can be detected in EB aerosol.

SIGNIFICANCE AND NOVELTY

The work shows a comprehensive workflow for elucidating drug excretion into exhaled breath aerosol. This bioanalytical strategy and the corresponding novel data from this study are the foundation for further method development and to better understand, which drugs and their metabolites can be addressed by exhaled breath aerosol bioanalysis.

Carbon Nanotube Immunotoxicity in Alveolar Epithelial Type II Cells Is Mediated by Physical Contact-Independent Cell-Cell Interaction with Macrophages as Demonstrated in an Optimized Air-Liquid Interface (ALI) Coculture Model

There is a need for the assessment of respiratory hazard potential and mode of action of carbon nanotubes (CNTs) before their approval for technological or medical applications. In CNT-exposed lungs, both alveolar macrophages (MФs), which phagocytose CNTs, and alveolar epithelial type II cells (AECII cells), which show tissue injury, are impacted but cell-cell interactions between them and the impacted mechanisms are unclear. To investigate this, we first optimized an air-liquid interface (ALI) transwell coculture of human AECII cell line A549 (upper chamber) and human monocyte cell line THP-1 derived macrophages (lower chamber) in a 12-well culture by exposing macrophages to CNTs at varying doses (5-60 ng/well) for 12-48 h and measuring the epithelial response markers for cell differentiation/maturation (proSP-C), proliferation (Ki-67), and inflammation (IL-1β). In optimal ALI epithelial-macrophage coculture (3:1 ratio), expression of Ki-67 in AECII cells showed dose dependence, peaking at 15 ng/well CNT dose; the Ki-67 and IL-1β responses were detectable within 12 h, peaking at 24-36 h in a time-course. Using the optimized ALI transwell coculture set up with and without macrophages, we demonstrated that direct interaction between CNTs and MФs, but not a physical cell-cell contact between MФ and AECII cells, was essential for inducing immunotoxicity (proliferative and inflammatory responses) in the AECII cells.

Validation and application of an automated multitarget LC-MS/MS method for drugs of abuse testing using exhaled breath as specimen

Aerosol microparticles in exhaled breath carry non-volatile compounds from the deeper parts of the lung. When captured and analyzed, these aerosol microparticles constitute a non-invasive and readily available specimen for drugs of abuse testing. The present study aimed to evaluate a simple breath collection device in a clinical setting. The device divides a breath sample into three parallel "collectors" that can be individually analyzed. Urine was used as the reference specimen, and parallel specimens were collected from 99 patients undergoing methadone maintenance treatment. Methadone was used as the primary validation parameter. A sensitive multi-analyte method using tandem liquid chromatography - mass spectrometry was developed and validated as part of the project. The method was successfully validated for 36 analytes with a limit of detection of 1 pg/collector for most compounds. Based on the validation results tetrahydrocannabinol THC), cannabidiol (CBD), and lysergic acid diethylamide (LSD) are suitable for qualitative analysis, but all other analytes can be quantitively assessed by the method. Methadone was positive in urine in 97 cases and detected in exhaled breath in 98 cases. Median methadone concentration was 64 pg/collector. The methadone metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) was detected in 90 % of the cases but below 10 pg/collector in most. Amphetamine was also present in the urine in 17 cases and in exhaled breath in 16 cases. Several other substances were detected in the exhaled breath and urine samples, but at a lower frequency. This study concluded that the device provides a specimen from exhaled breath, that is useful for drugs of abuse testing. The results show that high analytical sensitivity is needed to achieve good detectability and detection time after intake.

Particles in Exhaled Air (PExA): Clinical Uses and Future Implications

Access to distal airway samples to assess respiratory diseases is not straightforward and requires invasive procedures such as bronchoscopy and bronchoalveolar lavage. The particles in exhaled air (PExA) device provides a non-invasive means of assessing small airways; it captures distal airway particles (PEx) sized around 0.5-7 μm and contains particles of respiratory tract lining fluid (RTLF) that originate during airway closure and opening. The PExA device can count particles and measure particle mass according to their size. The PEx particles can be analysed for metabolites on various analytical platforms to quantitatively measure targeted and untargeted lung specific markers of inflammation. As such, the measurement of distal airway components may help to evaluate acute and chronic inflammatory conditions such as asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and more recently, acute viral infections such as COVID-19. PExA may provide an alternative to traditional methods of airway sampling, such as induced sputum, tracheal aspirate, or bronchoalveolar lavage. The measurement of specific biomarkers of airway inflammation obtained directly from the RTLF by PExA enables a more accurate and comprehensive understanding of pathophysiological changes at the molecular level in patients with acute and chronic lung diseases.

Proteomic Analysis of Primary Graft Dysfunction in Porcine Lung Transplantation Reveals Alveolar-Capillary Barrier Changes Underlying the High Particle Flow Rate in Exhaled Breath

Primary graft dysfunction (PGD) remains a challenge for lung transplantation (LTx) recipients as a leading cause of poor early outcomes. New methods are needed for more detailed monitoring and understanding of the pathophysiology of PGD. The measurement of particle flow rate (PFR) in exhaled breath is a novel tool to monitor and understand the disease at the proteomic level. In total, 22 recipient pigs underwent orthotopic left LTx and were evaluated for PGD on postoperative day 3. Exhaled breath particles (EBPs) were evaluated by mass spectrometry and the proteome was compared to tissue biopsies and bronchoalveolar lavage fluid (BALF). Findings were confirmed in EBPs from 11 human transplant recipients. Recipients with PGD had significantly higher PFR [686.4 (449.7-8,824.0) particles per minute (ppm)] compared to recipients without PGD [116.6 (79.7-307.4) ppm, p = 0.0005]. Porcine and human EBP proteins recapitulated proteins found in the BAL, demonstrating its utility instead of more invasive techniques. Furthermore, adherens and tight junction proteins were underexpressed in PGD tissue. Histological and proteomic analysis found significant changes to the alveolar-capillary barrier explaining the high PFR in PGD. Exhaled breath measurement is proposed as a rapid and non-invasive bedside measurement of PGD.

Small airways in asthma: From inflammation and pathophysiology to treatment response

Small airways are characterized as those with an inner diameter less than 2 mm and constitute a major site of pathology and inflammation in asthma disease. It is estimated that small airways dysfunction may occur before the emergence of noticeable symptoms, spirometric abnormalities and imaging findings, thus characterizing them as "the quiet or silent zone" of the lungs. Despite their importance, measuring and quantifying small airways dysfunction presents a considerable challenge due to their inaccessibility in usual functional measurements, primarily due to their size and peripheral localization. Several pulmonary function tests have been proposed for the assessment of the small airways, including impulse oscillometry, nitrogen washout, body plethysmography, as well as imaging methods. Nevertheless, none of these methods has been established as the definitive "gold standard," thus, a combination of them should be used for an effective assessment of the small airways. Widely used asthma treatments seem to also affect several parameters of the small airways. Emerging biologic treatments show promising results in reducing small airways inflammation and remodelling, providing evidence for potential alterations in the disease's progression and outcomes. These novel therapies have implications not only in the clinical aspects of asthma but also in its inflammatory and functional aspects.

Comparison of particles in exhaled air and multiple breath washout for assessment of small airway function in children with cystic fibrosis

BACKGROUND

The introduction of modulator therapy for cystic fibrosis (CF) has led to an increased interest in the detection of small airway disease (SAD) as sensitive marker of treatment response. The particles in exhaled air (PExA) method, which records exhaled particle mass (PEx ng/L) and number (PExNR), detects SAD in adult patients. Our primary aim was to investigate if PExA outcomes in children with CF are different when compared to controls and associated with more severe disease. Secondary aims were to assess feasibility and repeatability of PExA in children with CF and to correlate PExA to multiple breath nitrogen washout (MBNW) as an established marker of SAD.

METHODS

Thirteen healthy children (HC), 17 children with CF with normal lung function (CF-N) (FEV1 z-score ≥ -1.64) and six with airway obstruction (CF-AO) (FEV1 z-score < -1.64) between 8 and 18 years performed MBNW followed by PExA and spirometry. Children with CF repeated the measurements after 3 months.

RESULTS

PEx ng/L and PExNR/L per liter of exhaled breath were similar between the three groups. The lung clearance index (LCI) was significantly higher in both CF-N and CF-AO compared to HC. All participants, except one, were able to perform PExA. Coefficient of variation for PEx ng/l was (median) 0.38, range 0-1.25 and PExNR/l 0.38, 0-1.09. Correlation between LCI and PEx ng/l was low, rs 0.32 (p = .07).

CONCLUSION

PExA is feasible in children. In contrast to LCI, PExA did not differentiate healthy children from children with CF suggesting it to be a less sensitive tool to detect SAD.

Airway and systemic biomarkers of health effects after short-term exposure to indoor ultrafine particles from cooking and candles - A randomized controlled double-blind crossover study among mild asthmatic subjects

BACKGROUND

There is insufficient knowledge about the systemic health effects of exposure to fine (PM_2.5) and ultrafine particles emitted from typical indoor sources, including cooking and candlelight burning. We examined whether short-term exposure to emissions from cooking and burning candles cause inflammatory changes in young individuals with mild asthma. Thirty-six non-smoking asthmatics participated in a randomized controlled double-blind crossover study attending three exposure sessions (mean PM_2.5 µg/m³_; polycyclic aromatic hydrocarbons ng/m³): (a) air mixed with emissions from cooking (96.1; 1.1), (b) air mixed with emissions from candles (89.8; 10), and (c) clean filtered air (5.8; 1.0). Emissions were generated in an adjacent chamber and let into a full-scale exposure chamber where participants were exposed for five hours. Several biomarkers were assessed in relation to airway and systemic inflammatory changes; the primary outcomes of interest were surfactant Protein-A (SP-A) and albumin in droplets in exhaled air - novel biomarkers for changes in the surfactant composition of small airways. Secondary outcomes included cytokines in nasal lavage, cytokines, C-reactive protein (CRP), epithelial progenitor cells (EPCs), genotoxicity, gene expression related to DNA-repair, oxidative stress, and inflammation, as well as metabolites in blood. Samples were collected before exposure start, right after exposure and the next morning.

RESULTS

SP-A in droplets in exhaled air showed stable concentrations following candle exposure, while concentrations decreased following cooking and clean air exposure. Albumin in droplets in exhaled air increased following exposure to cooking and candles compared to clean air exposure, although not significant. Oxidatively damaged DNA and concentrations of some lipids and lipoproteins in the blood increased significantly following exposure to cooking. We found no or weak associations between cooking and candle exposure and systemic inflammation biomarkers including cytokines, CRP, and EPCs.

CONCLUSIONS

Cooking and candle emissions induced effects on some of the examined health-related biomarkers, while no effect was observed in others; Oxidatively damaged DNA and concentrations of lipids and lipoproteins were increased in blood after exposure to cooking, while both cooking and candle emissions slightly affected the small airways including the primary outcomes SP-A and albumin. We found only weak associations between the exposures and systemic inflammatory biomarkers. Together, the results show the existence of mild inflammation following cooking and candle exposure.

Activation of the Complement and Coagulation Systems in the Small Airways in Asthma

BACKGROUND

Several studies have shown the importance of the complement and coagulation systems in the pathogenesis of asthma.

OBJECTIVES

We explored whether we could detect differentially abundant complement and coagulation proteins in the samples obtained from the small airway lining fluid by collection of exhaled particles in patients with asthma and whether these proteins are associated with small airway dysfunction and asthma control.

METHOD

Exhaled particles were obtained from 20 subjects with asthma and 10 healthy controls (HC) with the PExA method and analysed with the SOMAscan proteomics platform. Lung function was assessed by nitrogen multiple breath washout test and spirometry.

RESULTS

53 proteins associated with the complement and coagulation systems were included in the analysis. Nine of those proteins were differentially abundant in subjects with asthma as compared to HC, and C3 was significantly higher in inadequately controlled asthma as compared to well-controlled asthma. Several proteins were associated with physiological tests assessing small airways.

CONCLUSIONS

The study highlights the role of the local activation of the complement and coagulation systems in the small airway lining fluid in asthma and their association with both asthma control and small airway dysfunction. The findings highlight the potential of complement factors as biomarkers to identify different sub-groups among patients with asthma that could potentially benefit from a therapeutic approach targeting the complement system.

Evaluation of indoor environmental quality, personal cumulative exposure dose, and aerosol transmission risk levels inside urban buses in Dalian, China

The transmission of pollutants in buses has an important impact on personal exposure to airborne particles and spread of the COVID-19 epidemic in enclosed spaces. We conducted the following real-time field measurements inside buses: CO2, airborne particle concentration, temperature, and relative humidity data during peak and off-peak hours in spring and autumn. Correlation analysis was adopted to evaluate the dominant factors influencing CO2 and particle mass concentrations in the vehicle. The cumulative personal exposure dose to particulate matter and reproduction number were calculated for passengers on a one-way trip. The results showed the in-cabin CO2 concentrations, with 22.11% and 21.27% of the total time exceeding 1000 ppm in spring and autumn respectively. In-cabin PM2.5 mass concentration exceeded 35 μm/m3 by 57.35% and 86.42% in spring and autumn, respectively. CO2 concentration and the cumulative number of passengers were approximately linearly correlated in both seasons, with R value up to 0.896. The cumulative number of passengers had the most impact on PM2.5 mass concentration among tested parameters. The cumulative personal exposure dose to PM2.5 during a one-way trip in autumn was up to 43.13 μg. The average reproductive number throughout the one-way trip was 0.26; it was 0.57 under the assumed extreme environment. The results of this study provide an important basic theoretical guidance for the optimization of ventilation system design and operation strategies aimed at reducing multi-pollutant integrated health exposure and airborne particle infection (such as SARS-CoV-2) risks.

Releasing high positive end-expiratory pressure to a low level generates a pronounced increase in particle flow from the airways

OBJECTIVES

Detecting particle flow from the airways by a non-invasive analyzing technique might serve as an additional tool to monitor mechanical ventilation. In the present study, we used a customized particles in exhaled air (PExA) technique, which is an optical particle counter for the monitoring of particle flow in exhaled air. We studied particle flow while increasing and releasing positive end-expiratory pressure (PEEP). The aim of this study was to investigate the impact of different levels of PEEP on particle flow in exhaled air in an experimental setting. We hypothesized that gradually increasing PEEP will reduce the particle flow from the airways and releasing PEEP from a high level to a low level will result in increased particle flow.

METHODS

Five fully anesthetized domestic pigs received a gradual increase of PEEP from 5 cmH₂O to a maximum of 25 cmH₂O during volume-controlled ventilation. The particle count along with vital parameters and ventilator settings were collected continuously and measurements were taken after every increase in PEEP. The particle sizes measured were between 0.41 µm and 4.55 µm.

RESULTS

A significant increase in particle count was seen going from all levels of PEEP to release of PEEP. At a PEEP level of 15 cmH₂O, there was a median particle count of 282 (154-710) compared to release of PEEP to a level of 5 cmH₂O which led to a median particle count of 3754 (2437-10,606) (p < 0.009). A decrease in blood pressure was seen from baseline to all levels of PEEP and significantly so at a PEEP level of 20 cmH₂O.

CONCLUSIONS

In the present study, a significant increase in particle count was seen on releasing PEEP back to baseline compared to all levels of PEEP, while no changes were seen when gradually increasing PEEP. These findings further explore the significance of changes in particle flow and their part in pathophysiological processes within the lung.

Aerosol measurement identifies SARS-CoV 2 PCR positive adults compared with healthy controls

BACKGROUND

SARS-CoV-2 is spread primarily through droplets and aerosols. Exhaled aerosols are generated in the upper airways through shear stress and in the lung periphery by 'reopening of collapsed airways'. Aerosol measuring may detect highly contagious individuals ("super spreaders or super-emitters") and discriminate between SARS-CoV-2 infected and non-infected individuals. This is the first study comparing exhaled aerosols in SARS-CoV-2 infected individuals and healthy controls.

DESIGN

A prospective observational cohort study in 288 adults, comprising 64 patients testing positive by SARS CoV-2 PCR before enrollment, and 224 healthy adults testing negative (matched control sample) at the University Hospital Frankfurt, Germany, from February to June 2021. Study objective was to evaluate the concentration of exhaled aerosols during physiologic breathing in SARS-CoV-2 PCR-positive and -negative subjects. Secondary outcome measures included correlation of aerosol concentration to SARS-CoV-2 PCR results, change in aerosol concentration due to confounders, and correlation between clinical symptoms and aerosol.

RESULTS

There was a highly significant difference in respiratory aerosol concentrations between SARS-CoV-2 PCR-positive (median 1490.5/L) and -negative subjects (median 252.0/L; p < 0.0001). There were no significant differences due to age, sex, smoking status, or body mass index. ROC analysis showed an AUC of 0.8918.

CONCLUSIONS

Measurements of respiratory aerosols were significantly elevated in SARS-CoV-2 positive individuals, which helps to understand the spread and course of respiratory viral infections, as well as the detection of highly infectious individuals.

Exhaled breath condensate as bioanalyte: from collection considerations to biomarker sensing

Since the SARS-CoV-2 pandemic, the potential of exhaled breath (EB) to provide valuable information and insight into the health status of a person has been revisited. Mass spectrometry (MS) has gained increasing attention as a powerful analytical tool for clinical diagnostics of exhaled breath aerosols (EBA) and exhaled breath condensates (EBC) due to its high sensitivity and specificity. Although MS will continue to play an important role in biomarker discovery in EB, its use in clinical setting is rather limited. EB analysis is moving toward online sampling with portable, room temperature operable, and inexpensive point-of-care devices capable of real-time measurements. This transition is happening due to the availability of highly performing biosensors and the use of wearable EB collection tools, mostly in the form of face masks. This feature article will outline the last developments in the field, notably the novel ways of EBA and EBC collection and the analytical aspects of the collected samples. The inherit non-invasive character of the sample collection approach might open new doors for efficient ways for a fast, non-invasive, and better diagnosis.

An explorative study on respiratory health among operators working in polymer additive manufacturing

Additive manufacturing (AM), or 3D printing, is a growing industry involving a wide range of different techniques and materials. The potential toxicological effects of emissions produced in the process, involving both ultrafine particles and volatile organic compounds (VOCs), are unclear, and there are concerns regarding possible health implications among AM operators. The objective of this study was to screen the presence of respiratory health effects among people working with liquid, powdered, or filament plastic materials in AM.

Methods

In total, 18 subjects working with different additive manufacturing techniques and production of filament with polymer feedstock and 20 controls participated in the study. Study subjects filled out a questionnaire and underwent blood and urine sampling, spirometry, impulse oscillometry (IOS), exhaled NO test (FeNO), and collection of particles in exhaled air (PEx), and the exposure was assessed. Analysis of exhaled particles included lung surfactant components such as surfactant protein A (SP-A) and phosphatidylcholines. SP-A and albumin were determined using ELISA. Using reversed-phase liquid chromatography and targeted mass spectrometry, the relative abundance of 15 species of phosphatidylcholine (PC) was determined in exhaled particles. The results were evaluated by univariate and multivariate statistical analyses (principal component analysis).

Results

Exposure and emission measurements in AM settings revealed a large variation in particle and VOC concentrations as well as the composition of VOCs, depending on the AM technique and feedstock. Levels of FeNO, IOS, and spirometry parameters were within clinical reference values for all AM operators. There was a difference in the relative abundance of saturated, notably dipalmitoylphosphatidylcholine (PC16:0_16:0), and unsaturated lung surfactant lipids in exhaled particles between controls and AM operators.

Conclusion

There were no statistically significant differences between AM operators and controls for the different health examinations, which may be due to the low number of participants. However, the observed difference in the PC lipid profile in exhaled particles indicates a possible impact of the exposure and could be used as possible early biomarkers of adverse effects in the airways.

Exhaled biomarkers in adults with non-productive cough

BACKGROUND

Chronic cough is a common condition but disease mechanisms are not fully understood. Our aim was to study respiratory biomarkers from the small airways in individuals with non-productive cough.

METHODS

A cohort of 107 participants answered detailed questionnaires, performed spirometry, exhaled NO measurement, impulse oscillometry, gave blood samples and particles in exhaled air (PEx) samples. Current smokers (N = 38) were excluded. A total of 14 participants reported non-productive cough (cases). A total of 55 participants reported no cough (control group). PEx samples, containing exhaled particles derived from small airways, were collected and analysed with the SOMAscan proteomics platform.

RESULTS

Participants with non-productive cough had similar age, sex, BMI, and inflammation markers in blood tests, as participants without cough. The proteomics analysis found 75 proteins significantly altered among participants with chronic cough compared to controls, after adjusting for sex and investigator performing the PExA measurement (all with p-value < 0.05 and q-value ≤ 0.13, thereof 21 proteins with a q-value < 0.05). These proteins were mostly involved in immune and inflammatory responses, complement and coagulation system, but also tight junction proteins and proteins involved in neuroinflammatory responses.

CONCLUSIONS

This exploratory study on proteomics of exhaled particles among individuals with chronic cough found alterations in relative abundance of 75 proteins. The proteins identified are implicated in both pathways known to be implicated in cough, but also potentially new pathways. Further studies are needed to explore the importance of these findings.

A new method for investigating bioequivalence of inhaled formulations: A pilot study on salbutamol

Purpose: An efficient, cost-effective and non-invasive test is required to overcome the challenges faced in the process of bioequivalence (BE) studies of various orally inhaled drug formulations. Two different types of pressurized meter dose inhalers (MDI-1 and MDI-2) were used in this study to test the practical applicability of a previously proposed hypothesis on the BE of inhaled salbutamol formulations. Methods: Salbutamol concentration profiles of the exhaled breath condensate (EBC) samples collected from volunteers receiving two inhaled formulations were compared employing BE criteria. In addition, the aerodynamic particle size distribution of the inhalers was determined by employing next generation impactor. Salbutamol concentrations in the samples were determined using liquid and gas chromatographic methods. Results: The MDI-1 inhaler induced slightly higher EBC concentrations of salbutamol when compared with MDI-2. The geometric MDI-2/MDI-1 mean ratios (confidence intervals) were 0.937 (0.721-1.22) for maximum concentration and 0.841 (0.592-1.20) for area under the EBC-time profile, indicating a lack of BE between the two formulations. In agreement with the in vivo data, the in vitro data indicated that the fine particle dose (FPD) of MDI-1 was slightly higher than that for the MDI-2 formulation. However, the FPD differences between the two formulations were not statistically significant. Conclusion: EBC data of the present work may be considered as a reliable source for assessment of the BE studies of orally inhaled drug formulations. However, more detailed investigations employing larger sample sizes and more formulations are required to provide more evidence for the proposed method of BE assay.

Impact of Chemical Properties of Human Respiratory Droplets and Aerosol Particles on Airborne Viruses' Viability and Indoor Transmission

The airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified as a potential pandemic challenge, especially in poorly ventilated indoor environments, such as certain hospitals, schools, public buildings, and transports. The impacts of meteorological parameters (temperature and humidity) and physical property (droplet size) on the airborne transmission of coronavirus in indoor settings have been previously investigated. However, the impacts of chemical properties of viral droplets and aerosol particles (i.e., chemical composition and acidity (pH)) on viability and indoor transmission of coronavirus remain largely unknown. Recent studies suggest high organic content (proteins) in viral droplets and aerosol particles supports prolonged survival of the virus by forming a glassy gel-type structure that restricts the virus inactivation process under low relative humidity (RH). In addition, the virus survival was found at neutral pH, and inactivation was observed to be best at low (<5) and high pH (>10) values (enveloped bacteriophage Phi6). Due to limited available information, this article illustrates an urgent need to research the impact of chemical properties of exhaled viral particles on virus viability. This will improve our fundamental understanding of indoor viral airborne transmission mechanisms.

Aerosol emissions from wind instruments: effects of performer age, sex, sound pressure level, and bell covers

Aerosol emissions from wind instruments are a suspected route of transmission for airborne infectious diseases, such as SARS-CoV-2. We evaluated aerosol number emissions (from 0.25 to 35.15 μm) from 81 volunteer performers of both sexes and varied age (12 to 63 years) while playing wind instruments (bassoon, clarinet, flute, French horn, oboe, piccolo, saxophone, trombone, trumpet, and tuba) or singing. Measured emissions spanned more than two orders of magnitude, ranging in rate from < 8 to 1,815 particles s-1, with brass instruments, on average, producing 191% (95% CI 81-367%) more aerosol than woodwinds. Being male was associated with a 70% increase in emissions (vs. female; 95% CI 9-166%). Each 1 dBA increase in sound pressure level was associated with a 28% increase (95% CI 10-40%) in emissions from brass instruments; sound pressure level was not associated with woodwind emissions. Age was not a significant predictor of emissions. The use of bell covers reduced aerosol emissions from three brass instruments tested (trombone, tuba, and trumpet), with average reductions ranging from 53 to 73%, but not for the two woodwind instruments tested (oboe and clarinet). Results from this work can facilitate infectious disease risk management for the performing arts.

Short- and medium-term effect of inhaled corticosteroids on exhaled breath biomarkers in severe asthma

BACKGROUND

Inhaled corticosteroids (ICS) are the mainstay of therapy in asthma, but benefits vary due to disease heterogeneity. Steroid insensitivity is a particular problem in severe asthma, where patients may require systemic corticosteroids and/or biologics. Biomarkers sensitive to ICS over a short period of time could inform earlier and more personalised treatment choices.

OBJECTIVE

To investigate how exhaled breath biomarkers change over two-hours and one-week following monitored ICS dosing in severe asthma patients with evidence of uncontrolled airway inflammation.

METHOD

Patients with severe asthma and elevated FeNO (≥45ppb, indicative of active airway inflammation) were recruited. Exhaled breath biomarkers were evaluated using fractional exhaled nitric oxide (FeNO), exhaled breath temperature (EBT), particles in exhaled breath (PExA) and volatile organic compounds (VOCs). Samples were collected over 2 hrs following observed inhalation of 1000mcg fluticasone propionate, and at a second visit 1 week after taking the same dose daily via an inhaler monitoring device that recorded correct actuation and inhalation. Changes in parameters over 2 hrs were analysed by the Friedman test and 1 week by Wilcoxon's test (p-value for significance set at 0.05; for VOCs false discovery rate q of 0.1 by Benjamini-Hochberg method applied).

RESULTS

17 participants (9 male) were recruited with median (IQR) age 45 (36-59) yrs. EBT (p<0.05) and levels of six VOCs (q<0.1) fell over the 2 hrs after high dose ICS; there were no changes in FeNO or PEXA. After one week of using high dose ICS, there were falls in FeNO, EBT and two VOCs (p<0.05), but no changes in PEXA.

CONCLUSION

Reduction in exhaled breath temperature over the short and medium term after high dose ICS may reflect airway vascular changes, and this, together with the observed changes in exhaled VOCs, merits further investigation as potential markers of inhaled corticosteroid use and effectiveness.

Correlation of theophylline levels in rat exhaled breath and lung tissue after its intravenous injection

It is important to know the drug level in the target tissue to determine its dose. Some methods rely on blood levels of a drug to estimate its concentration in the tissues, which can be inaccurate. We thought that drug levels in exhaled breath aerosol (EBA) to give a more accurate value of the level of a test drug in the lung. Rats were intravenously injected with the bronchodilator theophylline and exhaled breath was collected up to 10-20 min after administration. Immediately after breath collection, lung, liver, kidney, and blood were collected and the pharmacokinetics were examined using these samples. Awake free-moving rats were used to efficiently collect exhaled breath from rats with low tidal volume. The amount of exhaled breath of rats was estimated by the amount of exhaled water vapor, and the drug concentration in exhaled breath sample was expressed by the amount of water vapor as the denominator. By using the active sampling method in which the adsorbent is sucked by a pump, theophylline in rat exhaled breath could be measured accurately. When the correlation of theophylline concentration in each sample was examined, a high correlation (r²= 0.74) was found only in exhaled breath and lung tissue. EBA was considered better than blood in pharmacokinetic analysis of lung tissue.

Inflammatory cytokines can be monitored in exhaled breath particles following segmental and inhalation endotoxin challenge in healthy volunteers

Particles in exhaled air (PEx) are generated when collapsed small airways reopen during breathing. PEx can be noninvasively collected by particle impaction, allowing the analysis of undiluted epithelial lining fluid (ELF). We used the endotoxin (LPS) challenge model to proof the concept that PEx can be used to monitor inflammatory changes in the lung. In this pilot study PEx were collected from ten healthy nonsmoking subjects using the PExA^® instrument twice before and twice after a segmental LPS challenge (5, 21 h). Following a 4-week washout period, PEx were collected during the week before and 5 h after a whole lung LPS inhalation challenge. PEx biomarkers were compared to blood, bronchoalveolar lavage (BAL) following segmental challenge and induced sputum (ISP) following inhalation challenge. A clear LPS-induced inflammatory response was detectable in BAL fluid, ISP and blood. Albumin and surfactant-protein D were detectable in all PEx samples. While most baseline cytokines were close to or below the detection limit, the median (IQR) IL-6 and IL-8 concentrations in PEx increased significantly after segmental (0.04 (0.03; 0.06) fg/ng PEx; 0.10 (0.08; 0.17) fg/ng PEx) and inhalation LPS challenge (0.19 (0.15; 0.23) fg/ng PEx; 0.32 (0.23; 0.42) fg/ng PEx). Using a highly sensitive analysis platform, we were able to detect a cytokine response in PEx during the early phase of LPS-induced inflammation. This will broaden the spectrum of applications for this noninvasive method to monitor inflammatory processes in the lung, including its use in clinical trials for respiratory drug development.Trial registration: The study has been registered on 07.02.2017 at Clinicaltrials.gov (NCT03044327).

Exploring a new method for the assessment of metal exposure by analysis of exhaled breath of welders

Purpose

Air monitoring has been the accepted exposure assessment of toxic metals from, e.g., welding, but a method characterizing the actual dose delivered to the lungs would be preferable. Sampling of particles in exhaled breath can be used for the biomonitoring of both endogenous biomarkers and markers of exposure. We have explored a new method for the sampling of metals in exhaled breath from the small airways in a study on welders.

Methods

Our method for particle sampling, Particles in Exhaled Air (PExA®), is based on particle counting and inertial impaction. We applied it on 19 stainless steel welders before and after a workday. In parallel, air monitoring of chromium, manganese and nickel was performed as well as blood sampling after work.

Results

Despite substantial exposure to welding fumes, we were unable to show any significant change in the metal content of exhaled particles after, compared with before, exposure. However, the significance might be obscured by a substantial analytical background noise, due to metal background in the sampling media and possible contamination during sampling, as an increase in the median metal contents were indicated.

Conclusions

If efforts to reduce background and contamination are successful, the PExA® method could be an important tool in the investigations of metals in exhaled breath, as the method collects particles from the small airways in contrast to other methods. In this paper, we discuss the discrepancy between our findings and results from studies, using the exhaled breath condensate (EBC) methodology.

Severe acute respiratory syndrome coronavirus 2 can be detected in exhaled aerosol sampled during a few minutes of breathing or coughing

BACKGROUND

The knowledge on the concentration of viral particles in exhaled breath is limited. The aim of this study was to explore if severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be detected in aerosol from subjects with the coronavirus disease 2019 (COVID-19) during various types of breathing and coughing and how infection with SARS-CoV-2 may influence the number and size of exhaled aerosol particles.

METHODS

We counted and collected endogenous particles in exhaled breath in subjects with COVID-19 disease by two different impaction-based methods, during 20 normal breaths, 10 airway opening breaths, and three coughs, respectively. Breath samples were analyzed with reverse transcription real-time polymerase chain reaction (RT-PCR).

RESULTS

Detection of RNA in aerosol was possible in 10 out of 25 subjects. Presence of virus RNA in aerosol was mainly found in cough samples (n = 8), but also in airway opening breaths (n = 3) and in normal breaths (n = 4), with no overlap between the methods. No association between viral load in aerosol and number exhaled particles <5 μm was found. Subjects with COVID-19 exhaled less particles than healthy controls during normal breathing and airway opening breaths (all P < 0.05), but not during cough.

CONCLUSION

SARS-CoV-2 RNA can be detected in exhaled aerosol, sampled during a limited number of breathing and coughing procedures. Detection in aerosol seemed independent of viral load in the upper airway swab as well as of the exhaled number of particles. The infectious potential of the amount of virus detected in aerosol needs to be further explored.

Smoking induces sex-specific changes in the small airway proteome

Introduction

Cigarette smoke triggers many cellular and signaling responses in the lung and the resulting inflammation plays a central role in smoke-related lung diseases, such as COPD. We explored the effects of smoking on the small airway proteome in samples obtained by collection of exhaled particles with the aim to identify specific proteins dysregulated by smoking.

Methods

Exhaled particles were obtained from 38 current smokers, 47 former smokers and 22 healthy controls with the PExA method. 120 ng of sample was collected from individual subjects and analyzed with the SOMAscan proteomics platform. General linear model-based statistics were performed.

Results

Two hundred and three proteins were detected in at least half of 107 total samples. Active smoking exerted a significant impact on the protein composition of respiratory tract lining fluid (RTLF), with 81 proteins altered in current smokers compared to never smokers (p < 0.05, q < 0.124). Among the proteins most clearly discriminating between current and never smokers were sRAGE, FSTL3, SPOCK2 and protein S, all of them being less abundant in current smokers. Analysis stratified for sex unveiled sex differences with more pronounced proteomic alterations due to active smoking in females than males. Proteins whose abundance was altered by active smoking in women were to a larger extent related to the complement system. The small airway protein profile of former smokers appeared to be more similar to that observed in never smokers.

Conclusions

The study shows that smoking has a strong impact on protein expression in the small airways, and that smoking affects men and women differently, suggesting PExA sampling combined with high sensitivity protein analysis offers a promising platform for early detection of COPD and identification of novel COPD drug targets.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01825-6.

Particle flow rate from the airways as fingerprint diagnostics in mechanical ventilation in the intensive care unit: a randomised controlled study

Introduction

Mechanical ventilation can be monitored by analysing particles in exhaled air as measured by particle flow rate (PFR). This could be a potential method of detecting ventilator-induced lung injury (VILI) before changes in conventional parameters can be detected. The aim of this study was to investigate PFR during different ventilation modes in patients without lung pathology.

Method

A prospective study was conducted on patients on mechanical ventilation in the cardiothoracic intensive care unit (ICU). A PExA 2.0 device was connected to the expiratory limb on the ventilator for continuous measurement of PFR in 30 patients randomised to either volume-controlled ventilation (VCV) or pressure-controlled ventilation (PCV) for 30 min including a recruitment manoeuvre. PFR measurements were continued as the patients were transitioned to pressure-regulated volume control (PRVC) and then pressure support ventilation (PSV) until extubation.

Results

PRVC resulted in significantly lower PFR, while those on PSV had the highest PFR. The distribution of particles differed significantly between the different ventilation modes.

Conclusions

Measuring PFR is safe after cardiac surgery in the ICU and may constitute a novel method of continuously monitoring the small airways in real time. A low PFR during mechanical ventilation may correlate to a gentle ventilation strategy. PFR increases as the patient transitions from controlled mechanical ventilation to autonomous breathing, which most likely occurs as recruitment by the diaphragm opens up more distal airways. Different ventilation modes resulted in unique particle patterns and could be used as a fingerprint for the different ventilation modes.

Particle flow rate (PFR) from the airways may be used to continuously monitor the small airways in real time. A low PFR during mechanical controlled ventilation is likely to correspond to a protective ventilation.https://bit.ly/2RSkIqL

Current smoking alters phospholipid- and surfactant protein A levels in small airway lining fluid: An explorative study on exhaled breath

Small airways are difficult to access. Exhaled droplets, also referred to as particles, provide a sample of small airway lining fluid and may reflect inflammatory responses. We aimed to explore the effect of smoking on the composition and number of exhaled particles in a smoker-enriched study population. We collected and chemically analyzed exhaled particles from 102 subjects (29 never smokers, 36 former smokers and 37 current smokers) aged 39 to 83 years (median 63). A breathing maneuver maximized the number exhaled particles, which were quantified with a particle counter. The contents of surfactant protein A and albumin in exhaled particles was quantified with immunoassays and the contents of the phospholipids dipalmitoyl- and palmitoyl-oleoyl- phosphatidylcholine with mass spectrometry. Subjects also performed spirometry and nitrogen single breath washout. Associations between smoking status and the distribution of contents in exhaled particles and particle number concentration were tested with quantile regression, after adjusting for potential confounders. Current smokers, compared to never smokers, had higher number exhaled particles and more surfactant protein A in the particles. The magnitude of the effects of current smoking varied along the distribution of each PEx-variable. Among subjects with normal lung function, phospholipid levels were elevated in current smokers, in comparison to no effect of smoking on these lipids at abnormal lung function. Smoking increased exhaled number of particles and the contents of lipids and surfactant protein A in the particles. These findings might reflect early inflammatory responses to smoking in small airway lining fluid, also when lung function is within normal limits.

The role of respiratory droplet physicochemistry in limiting and promoting the airborne transmission of human coronaviruses: A critical review

Whether virulent human pathogenic coronaviruses (SARS-CoV, MERS-CoV, SARS-CoV-2) are effectively transmitted by aerosols remains contentious. Transmission modes of the novel coronavirus have become a hot topic of research with the importance of airborne transmission controversial due to the many factors that can influence virus transmission. Airborne transmission is an accepted potential route for the spread of some viral infections (measles, chickenpox); however, aerosol features and infectious inoculum vary from one respiratory virus to another. Infectious virus-laden aerosols can be produced by natural human respiratory activities, and their features are vital determinants for virus carriage and transmission. Physicochemical characteristics of infectious respiratory aerosols can influence the efficiency of virus transmission by droplets. This critical review identifies studies reporting instances of infected patients producing airborne human pathogenic coronaviruses, and evidence for the role of physical/chemical characteristics of human-generated droplets in altering embedded viruses' viability. We also review studies evaluating these viruses in the air, field studies and available evidence about seasonality patterns. Ultimately the literature suggests that a proportion of virulent human coronaviruses can plausibly be transmitted via the air, even though this might vary in different conditions. Evidence exists for respirable-sized airborne droplet nuclei containing viral RNA, although this does not necessarily imply that the virus is transmittable, capable of replicating in a recipient host, or that inoculum is sufficient to initiate infection. However, evidence suggests that coronaviruses can survive in simulated droplet nuclei for a significant time (>24 h). Nevertheless, laboratory nebulized virus-laden aerosols might not accurately model the complexity of human carrier aerosols in studying airborne viral transport. In summary, there is disagreement on whether wild coronaviruses can be transmitted via an airborne path and display seasonal patterns. Further studies are therefore required to provide supporting evidence for the role of airborne transmission and assumed mechanisms underlying seasonality.

Optimization of an air-liquid interface in vitro cell co-culture model to estimate the hazard of aerosol exposures

Inhalation exposure to environmental and occupational aerosol contaminants is associated with many respiratory health problems. To realistically mimic long-term inhalation exposure for toxicity testing, lung epithelial cells need to maintained and exposed under air-liquid interface (ALI) conditions for a prolonged period of time. In addition, to study cellular responses to aerosol particles, lung epithelial cells have to be co-cultured with macrophages. To that aim, we evaluated human bronchial epithelial Calu-3, 16HBE14o- (16HBE), H292, and BEAS-2B cell lines with respect to epithelial morphology, barrier function and cell viability under prolonged ALI culture conditions. Only the Calu-3 cells can retain the monolayer structure and maintain a strong tight junction under long-term ALI culture at least up to 2 weeks. As such, Calu-3 cells were applied as the structural barrier to create co-culture models with human monocyte-derived macrophages (MDMs) and THP-1 derived macrophages (TDMs). Adhesion of macrophages onto the epithelial monolayer was allowed for 4 h with a density of 5 × 10⁴ macrophages/cm². In comparison to the Calu-3 mono-culture model, Calu-3 + TDM and Calu-3 + MDM co-culture models showed an increased sensitivity in inflammatory responses to lipopolysaccharide (LPS) aerosol at Day 1 of co-culture, with the Calu-3 + MDM model giving a stronger response than Calu-3 + TDM. Therefore, the epithelial monolayer integrity and increased sensitivity make the Calu-3 + MDM co-culture model a preferred option for ALI exposure to inhaled aerosols for toxicity testing.

Novel non-invasive particles in exhaled air method to explore the lining fluid of small airways-a European population-based cohort study

INTRODUCTION

Respiratory tract lining fluid of small airways mainly consists of surfactant that can be investigated by collection of the particles of exhaled aerosol (PExA) method. This offers an exciting prospect to monitor small airway pathology, including subjects with asthma and smokers.

AIM

To explore the influence of anthropometric factors and gender on phospholipids, surfactant protein A (SP-A) and albumin of the lining fluid of small airwaysand to examine the association with asthma and smoking. Furthermore, to examine if the surfactant components can predict lung function in terms of spirometry variables.

METHOD

This study employs the population-based cohort of the European Community Respiratory Health Survey III, including participants from Gothenburg city, Sweden (n=200). The PExA method enabled quantitative description and analytical analysis of phospholipids, SP-A and albumin of the lining fluid of small airways.

RESULTS

Age was a significant predictor of the phospholipids. The components PC14:0/16:0, PC16:0/18:2 (PC, phosphatidylcholine) and SP-A were higher among subjects with asthma, whereas albumin was lower. Among smokers, there were higher levels particularly of di-palmitoyl-di-phosphatidyl-choline compared with non-smokers. Most phospholipids significantly predicted the spirometry variables.

CONCLUSION

This non-invasive PExA method appears to have great potential to explore the role of lipids and proteins of surfactant in respiratory disease.

A novel system for the comprehensive collection of nonvolatile molecules from human exhaled breath

Characterization of nonvolatile molecules in exhaled breath particles can be used for respiratory disease monitoring and diagnosis. Conventional methods for the collection of nonvolatile molecules in breath heavily rely on the physical properties of exhaled breath particles. Strategies taking advantage of their chemical properties have not yet been explored. In the present study, we developed a column system in which the surface chemistry between organic nonvolatile molecules and octadecyl carbon chain was exploited for the comprehensive collection of metabolites, lipids, and proteins. We demonstrated that the collection system had the capture efficiency of 99% and the capacity to capture representative nonvolatile molecules. The collection system was further evaluated using human subjects and proteins collected from human exhaled breath were characterized and identified using gel electrophoresis and bottom-up proteomics. The identified 303 proteins from mass spectrometry were further searched against reported bronchoalveolar lavage fluid proteomes and it was shown that 60 proteins have the tissue origin of lower respiratory airways. In summary, we demonstrate that our collection system can collect nonvolatile molecules from human exhaled breath in an efficient and comprehensive manner and has the potential to be used for the study of respiratory diseases.

Mechanically ventilated patients exhibit decreased particle flow in exhaled breath as compared to normal breathing patients

Introduction

In this cohort study, we evaluated whether the particles in exhaled air (PExA) device can be used in conjunction with mechanical ventilation during surgery. The PExA device consists of an optical particle counter and an impactor that collects particles in exhaled air. Our aim was to establish the feasibility of the PExA device in combination with mechanical ventilation (MV) during surgery and if collected particles could be analysed. Patients with and without nonsmall cell lung cancer (NSCLC) undergoing lung surgery were compared to normal breathing (NB) patients with NSCLC.

Methods

A total of 32 patients were included, 17 patients with NSCLC (MV-NSCLC), nine patients without NSCLC (MV-C) and six patients with NSCLC and not intubated (NB). The PEx samples were analysed for the most common phospholipids in surfactant using liquid-chromatography-mass-spectrometry (LCMS).

Results

MV-NSCLC and MV-C had significantly lower numbers of particles exhaled per minute (particle flow rate; PFR) compared to NB. MV-NSCLC and MV-C also had a siginificantly lower amount of phospholipids in PEx when compared to NB. MV-NSCLC had a significantly lower amount of surfactant A compared to NB.

Conclusion

We have established the feasibility of the PExA device. Particles could be collected and analysed. We observed lower PFR from MV compared to NB. High PFR during MV may be due to more frequent opening and closing of the airways, known to be harmful to the lung. Online use of the PExA device might be used to monitor and personalise settings for mechanical ventilation to lower the risk of lung damage.

The PExA device is safe to use in conjunction with mechanical ventilation during surgery, and can measure and collect particles in exhaled air for subsequent biochemical analysishttp://bit.ly/2ofo6gw

Intra-individual variation of particles in exhaled air and of the contents of Surfactant protein A and albumin

INTRODUCTION

Particles in exhaled air (PEx) provide samples of respiratory tract lining fluid from small airways containing, for example, Surfactant protein A (SP-A) and albumin, potential biomarkers of small airway disease. We hypothesized that there are differences between morning, noon, and afternoon measurements and that the variability of repeated measurements is larger between days than within days.

METHODS

PEx was obtained in sixteen healthy non-smoking adults on 11 occasions, within one day and between days. SP-A and albumin were quantified by ELISA. The coefficient of repeatability (CR), intraclass correlation coefficient (ICC), and coefficient of variation (CV) were used to assess the variation of repeated measurements.

RESULTS

SP-A and albumin increased significantly from morning towards the noon and afternoon by 13% and 25% on average, respectively, whereas PEx number concentration and particle mean mass did not differ significantly between the morning, noon and afternoon. Between-day CRs were not larger than within-day CRs.

CONCLUSIONS

Time of the day influences the contents of SP-A and albumin in exhaled particles. The variation of repeated measurements was rather high but was not influenced by the time intervals between measurements.

Pharmacokinetics of methylphenidate and ritalinic acid in plasma correlations with exhaled breath and oral fluid in healthy volunteers

PURPOSE

The primary aim of this study was to explore the potential of alternative sampling matrices for methylphenidate by assessing the correlations between dl-threo-methylphenidate and dl-threo-ritalinic acid concentrations in exhaled breath and oral fluid with those in plasma, in repeated samples collected after a single oral dose of methylphenidate. The secondary aim was to study the enantioselective pharmacokinetics of methylphenidate in plasma, with a focus on interindividual variability in the metabolism of methylphenidate to ritalinic acid.

METHODS

Twelve healthy volunteers received a single oral dose of dl-threo-methylphenidate (Ritalin® capsules, 20 mg). Venous blood samples were collected for 24 h, and plasma analyzed for threo-enantiomers of methylphenidate and ritalinic acid with LC-MS/MS. Repeated sampling of exhaled breath, using a particle filter device, and of non-stimulated oral fluid, using a felt pad device, was also performed. Exhaled breath and oral fluid were analyzed with a non-enantioselective LC-MS/MS method for dl-threo-methylphenidate and dl-threo-ritalinic acid.

RESULTS

In all subjects, d-threo-methylphenidate was detectable in plasma for at least 15 h after the dose with a biphasic profile. l-threo-Methylphenidate was measurable in only five subjects and in most cases in low concentrations. However, one female subject displayed a biphasic concentration-time profile for l-threo-methylphenidate. This subject also had the highest d-threo-methylphenidate AUC (191 ng*h/mL versus 32-119 ng*h/mL in the other subjects). d-threo-Ritalinic acid concentrations were on average 25-fold higher (range 6-126) than the corresponding d-threo-methylphenidate concentrations. Single-time point plasma concentration ratios between d-threo-ritalinic acid and d-threo-methylphenidate 1.5-12 h after dose correlated highly (r = 0.88-0.98) with the d-threo-ritalinic acid AUC/d-threo-methylphenidate AUC ratio. In eleven subjects, dl-threo-methylphenidate in oral fluid mirrored the biphasic profile of methylphenidate (sum of d- and l-threo-enantiomers) in plasma, but the concentrations in oral fluid were on average 1.8 times higher than in plasma. dl-threo-Methylphenidate was detected in exhaled breath in all subjects, but there was no consistent concentration-time pattern.

CONCLUSIONS

In some subjects, the pharmacologically less active l-threo-enantiomer may contribute to the total plasma methylphenidate concentrations. Monitoring methylphenidate concentrations without enantiomeric determination carries the risk of missing such subjects, which might affect how the plasma concentrations of methylphenidate are interpreted and used for clinical decision making. The use of exhaled breath and oral fluid to assess medication adherence to MPH in patients with ADHD warrants further studies.

Assessing small airways dysfunction in asthma, asthma remission and healthy controls using particles in exhaled air

Asthma is a chronic disease, characterised by variable airflow obstruction and airway inflammation [1]. Small airways are thought to be a major site of pathology in asthma [2, 3]. There are different tools to assess small airways dysfunction (SAD), such as spirometry, body plethysmography, impulse oscillometry (IOS), multiple-breath nitrogen washout (MBNW), alveolar fraction of exhaled nitric oxide (F_ENO) and gas trapping assessed by high-resolution computed tomography (CT). However, there is no golden standard and some tests are difficult to perform [2, 3].

PExA mass can distinguish asthmatics from healthy individuals. Subjects with complete, but not clinical, asthma remission exhale more PExA mass compared to asthma. Higher PExA mass was associated with better function of both the small and large airways.http://bit.ly/2znHABg

Toward clinically applicable biomarkers for asthma: An EAACI position paper

Inflammation, structural, and functional abnormalities within the airways are key features of asthma. Although these processes are well documented, their expression varies across the heterogeneous spectrum of asthma. Type 2 inflammatory responses are characterized by increased levels of eosinophils, FeNO, and type 2 cytokines in blood and/or airways. Presently, type 2 asthma is the best-defined endotype, typically found in patients with allergic asthma, but surprisingly also in nonallergic patients with (severe) asthma. The etiology of asthma with non-type 2 inflammation is less clear. During the past decade, targeted therapies, including biologicals and small molecules, have been increasingly integrated into treatment strategies of severe asthma. These treatments block specific inflammatory pathways or single mediators. Single or composite biomarkers help to identify patients who will benefit from these treatments. So far, only a few inflammatory biomarkers have been validated for clinical application. The European Academy of Allergy & Clinical Immunology Task Force on Biomarkers in Asthma was initiated to review different biomarker sampling methods and to investigate clinical applicability of new and existing inflammatory biomarkers (point-of-care) to support diagnosis, targeted treatment, and monitoring of severe asthma. Subsequently, we discuss existing and novel targeted therapies for asthma as well as applicable biomarkers.

Surfactant Protein A in particles in exhaled air (PExA), bronchial lavage and bronchial wash - a methodological comparison

Introduction

At present, there are few methods available for monitoring respiratory diseases affecting distal airways. Bronchoscopy is the golden standard for sampling the lower airways. The recently developed method for collecting non-volatile material from exhaled air – PExA (Particles in Exhaled air) is a promising new tool, but no direct comparison between the two methods has yet been performed. The aim of the present study was to compare sampling using PExA with bronchial wash (BW) representing the larger more proximal airways and broncho-alveolar lavage (BAL) representing the distal airways.

Methods

15 healthy non-smoking subjects (7 female/8 male), age 28 ± 4 years, with normal lung function were included in the study. PExA-sampling (2 × 250 ng particles) and bronchoscopy with BW (2 × 20 ml) and BAL (3 × 60 ml sterile saline) was performed. Albumin and Surfactant Protein A (SP-A) were analyzed with ELISA, and analyses of correlation were performed.

Results

A significant association was found between BAL-fluid albumin and PExA-albumin (r_s:0.65 p = 0.01). There was also an association between SP-A in PExA and BAL, when corrected for albumin concentration (r_s:0.61, p = 0.015). When correlating concentrations of albumin and SP-A in bronchial wash and PExA respectively, no associations were found.

Conclusions

This is the first direct comparison between the bronchoscopy-based BW/BAL-fluids and material collected using the PExA methodology. Both albumin and albumin-corrected SP-A concentrations were significantly associated between BAL and PExA, however, no such association was found in either marker between BW and PExA. These results indicate that the PExA method samples the distal airways. PExA is thus considered a new promising non-invasive assessment for monitoring of the distal airways.

First evaluation of the possibility of testing for drugged driving using exhaled breath sampling

Objective: Driving under the influence of psychoactive drugs causes an increased risk for accidents. In combating this, sobriety tests at the roadside are common practice in most countries. Sampling of blood and urine for forensic investigation cannot be done at the roadside and poses practical problems associated with costs and time. An alternative specimen for roadside testing is therefore warranted and the aerosol particles in exhaled breath are one such alternative. Methods: The present study investigated how the exhaled breath sample compared with the routine legal investigations of blood and urine collected from suspects of drugged driving at 2 locations in Sweden. Exhaled breath was collected using a simple filter collection device and analyzed with state-of-the-art mass spectrometry technique. Results: The total number of cases used for this investigation was 67. In 54 of these cases (81%) the results regarding a positive or negative drug test result agreed and in 13 they disagreed. Out of these, the report from the forensic investigation of blood/urine was negative in 21 cases. In 6 of these, analytical findings were made in exhaled breath and these cases were dominated by the detection of amphetamine. In 7 cases a positive drug test from the forensic investigation was not observed in the breath sample and these cases were dominated by detection of tetrahydrocannabinol in blood. In total, 45 samples were positive with breath testing and the number of positives with established forensic methods was 46. Conclusion: The promising results from this study provide support to exhaled breath as a viable specimen for testing of drugged driving. The rapid, easy, and convenient sampling procedure offers the possibility to collect a drug test specimen at the roadside. The analytical investigation must be done in a laboratory at present because of the need for a highly sensitive instrument, which is already in use in forensic laboratories. The analytical work is not more challenging than for blood or oral fluid and should not cause an increase in cost. However, more studies need to be done before exhaled breath drug testing can be applied routinely for drugged driving investigation.

Different particle flow patterns from the airways after recruitment manoeuvres using volume-controlled or pressure-controlled ventilation

Objectives

Noninvasive online monitoring of different particle flows from the airways may serve as an additional tool to assess mechanical ventilation. In the present study, we used a customised PExA, an optical particle counter for monitoring particle flow and size distribution in exhaled air, to analyse airway particle flow for three subsequent days. We compared volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) and performed recruitment manoeuvres (RM).

Methods

Six animals were randomised into two groups: half received VCV before PCV and the other half received PCV before VCV. Measurements were taken daily for 1 h in each mode during three subsequent days in six fully anaesthetised domestic pigs. A RM was performed twice daily for 60 s at positive end-expiratory pressure (PEEP) of 10, 4 breaths/min and inspiratory-expiratory ratio (I:E) of 2:1. Measurements were taken for 3 min before the RM, 1 min during the RM and for 3 min after the RM. The particle sizes measured were between 0.48 and 3.37 μm.

Results

A significant stepwise decrease was observed in total particle count from day 1 to day 3, and at the same time, an increase in fluid levels was seen. Comparing VCV to PCV, a significant increase in total particle count was observed on day 2, with the highest particle count occurring during VCV. A significant increase was observed comparing before and after RM on day 1 and 2 but not on day 3. One animal developed ARDS and showed a different particle pattern compared to the other animals.

Conclusions

This study shows the safety and useability of the PExA technique used in conjunction with mechanical ventilation. We detected differences between the ventilation modes VCV and PCV in total particle count without any significant changes in ventilator pressure levels, FiO₂ levels or the animals’ vital parameters. The findings during RM indicate an opening of the small airways, but the effect is short lived. We have also showed that VCV and PCV may affect the lung physiology differently during recruitment manoeuvres. These findings might indicate that this technique may provide more refined information on the impact of mechanical ventilation.

Measuring antibiotics in exhaled air in critically ill, non-ventilated patients: A feasibility and proof of concept study

PURPOSE

Measurement of antibiotic concentrations is increasingly used to optimize antibiotic therapy. Plasma samples are typically used for this, but other matrices such as exhaled air could be an alternative.

MATERIALS AND METHODS

We studied 11 spontaneously breathing intensive care unit patients receiving either piperacillin/tazobactam or meropenem. Patients exhaled in the ExaBreath® device, from which the antibiotic was extracted. The presence of antibiotics was also determined in the condensate found in the device and in the plasma.

RESULTS

Piperacillin or meropenem could be detected in the filter in 9 patients and in the condensate in 10. Seven patients completed the procedure as prescribed. In these patients the median quantity of piperacillin in the filter was 3083 pg/filter (range 988-203,895 pg/filter), and 45 pg (range 6-126 pg) in the condensate; meropenem quantity was 21,168 pg/filter, but the quantity in the condensate was below the lower limit of quantification. There was no correlation between the concentrations in the plasma and quantities detected in the filter or condensate.

CONCLUSIONS

Piperacillin and meropenem can be detected and quantified in exhaled air of non-ventilated intensive care unit patients; these quantities did not correlate with plasma concentrations of these drugs.

Exhaled particles and small airways

BACKGROUND

Originally, studies on exhaled droplets explored properties of airborne transmission of infectious diseases. More recently, the interest focuses on properties of exhaled droplets as biomarkers, enabled by the development of technical equipment and methods for chemical analysis. Because exhaled droplets contain nonvolatile substances, particles is the physical designation. This review aims to outline the development in the area of exhaled particles, particularly regarding biomarkers and the connection with small airways, i e airways with an internal diameter < 2 mm.

MAIN BODY

Generation mechanisms, sites of origin, number concentrations of exhaled particles and the content of nonvolatile substances are studied. Exhaled particles range in diameter from 0.01 and 1000 μm depending on generation mechanism and site of origin. Airway reopening is one scientifically substantiated particle generation mechanism. During deep expirations, small airways close and the reopening process produces minute particles. When exhaled, these particles have a diameter of < 4 μm. A size discriminating sampling of particles < 4 μm and determination of the size distribution, allows exhaled particle mass to be estimated. The median mass is represented by particles in the size range of 0.7 to 1.0 μm. Half an hour of repeated deep expirations result in samples in the order of nanogram to microgram. The source of these samples is the respiratory tract ling fluid of small airways and consists of lipids and proteins, similarly to surfactant. Early clinical studies of e g chronic obstructive pulmonary disease and asthma, reported altered particle formation and particle composition.

CONCLUSION

The physical properties and content of exhaled particles generated by the airway reopening mechanism offers an exciting noninvasive way to obtain samples from the respiratory tract lining fluid of small airways. The biomarker potential is only at the beginning to be explored.

Exhaled Breath Condensate in Childhood Asthma: A Review and Current Perspective

Exhaled breath condensate (EBC) was introduced more than two decades ago as a novel, non-invasive tool to assess airway inflammation. This review summarizes the latest literature on the various markers in EBC to predict asthma in children. Despite many recommendations and two comprehensive Task Force reports, there is still large heterogeneity in published data. The biggest issue remains a lack of standardization regarding EBC collection, preservation, processing, and analysis. As a result, published studies show mixed or conflicting results, questioning the reproducibility of findings. A joint, multicenter research study is urgently needed to address the necessary methodological standardization.

Evolution of clinical and environmental health applications of exhaled breath research: Review of methods and instrumentation for gas-phase, condensate, and aerosols

Human breath, along with urine and blood, has long been one of the three major biological media for assessing human health and environmental exposure. In fact, the detection of odor on human breath, as described by Hippocrates in 400 BC, is considered the first analytical health assessment tool. Although less common in comparison to contemporary bio-fluids analyses, breath has become an attractive diagnostic medium as sampling is non-invasive, unlimited in timing and volume, and does not require clinical personnel. Exhaled breath, exhaled breath condensate (EBC), and exhaled breath aerosol (EBA) are different types of breath matrices used to assess human health and disease state. Over the past 20 years, breath research has made many advances in assessing health state, overcoming many of its initial challenges related to sampling and analysis. The wide variety of sampling techniques and collection devices that have been developed for these media are discussed herein. The different types of sensors and mass spectrometry instruments currently available for breath analysis are evaluated as well as emerging breath research topics, such as cytokines, security and airport surveillance, cellular respiration, and canine olfaction.

Particles in exhaled air (PExA): non-invasive phenotyping of small airways disease in adult asthma

RATIONALE

Asthma is often characterised by inflammation, damage and dysfunction of the small airways, but no standardised biomarkers are available.

OBJECTIVES

Using a novel approach-particles in exhaled air (PExA)-we sought to (a) sample and analyse abundant protein biomarkers: surfactant protein A (SPA) and albumin in adult asthmatic and healthy patients and (b) relate protein concentrations with physiological markers using phenotyping.

METHODS

83 adult asthmatics and 21 healthy volunteers were recruited from a discovery cohort in Leicester, UK, and 32 adult asthmatics as replication cohort from Sweden. Markers of airways closure/small airways dysfunction were evaluated using forced vital capacity, impulse oscillometry and multiple breath washout. SPA/albumin from PEx (PExA sample) were analysed using ELISA and corrected for acquired particle mass. Topological data analysis (TDA) was applied to small airway physiology and PExA protein data to identify phenotypes.

RESULTS

PExA manoeuvres were feasible, including severe asthmatic subjects. TDA identified a clinically important phenotype of asthmatic patients with multiple physiological markers of peripheral airway dysfunction, and significantly lower levels of both SPA and albumin.

CONCLUSION

We report that the PExA method is feasible across the spectrum of asthma severity and could be used to identify small airway disease phenotypes.

Positive matrix factorization: A data preprocessing strategy for direct mass spectrometry-based breath analysis

Interest in exhaled breath has grown considerably in recent years, as breath biosampling has shown promise for non-invasive disease diagnosis, therapeutic drug monitoring, and environmental exposure. Real time breath analysis can be accomplished via direct online mass spectrometry (MS)-based methods, which can provide more accurate and detailed data and an enhanced understanding of the temporal evolution of exhaled VOCs in the breath; however, the complicated chemical composition and large raw datasets involved in breath analysis have hindered the discovery of sources contributing to the exhaled VOCs. The positive matrix factorization (PMF) receptor model has been widely used for source apportionment in atmospheric studies. Since the exhaled VOCs contain compounds from various sources, such as alveolar air, mouth air and respiratory dead-space air, PMF may be also helpful for source apportionment of exhaled VOCs in the breath. Thus, this study explores the application of PMF in the pretreatment of direct breath measurement data. The results indicate that (i) endogenous compounds and background contaminants sources can be readily distinguished by PMF in data obtained from replicate measurements of human exhaled breath at single time points (~30 s/measurement), which may benefit both exhalome investigations and the identification of exposure biomarkers; (ii) sources resolved from online measurement data collected over longer periods (1.5 h) can be used to isolate the evolution of exhaled VOCs and investigate processes such as the pharmacokinetics of ketamine and its major metabolites. Therefore, PMF has shown promise for both data processing and subsequent data mining for the ambient MS-based breath analysis.

A new way of monitoring mechanical ventilation by measurement of particle flow from the airways using Pexa method in vivo and during ex vivo lung perfusion in DCD lung transplantation

BACKGROUND

Different mechanical ventilation settings are known to affect lung preservation for lung transplantation. Measurement of particle flow in exhaled air may allow online assessment of the impact of ventilation before changes in the tissue can be observed. We hypothesized that by analyzing the particle flow, we could understand the impact of different ventilation parameters.

METHODS

Particle flow was monitored in vivo, post mortem, and in ex vivo lung perfusion (EVLP) in six porcines with the Pexa (particles in exhaled air) instrument. Volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) were used to compare small versus large tidal volumes. The surfactant lipids dipalmitoylphosphatidylcholine (DPPC) and phosphatidylcholine (PC) were quantified by mass spectrometry.

RESULTS

In vivo the particle mass in VCV¹ was significantly lower than in VCV² (p = 0.0186), and the particle mass was significantly higher in PCV¹ than in VCV¹ (p = 0.0322). In EVLP, the particle mass in VCV¹ was significantly higher than in PCV¹ (p = 0.0371), and the particle mass was significantly higher in PCV² than in PCV¹ (p = 0.0127). DPPC was significantly higher in EVLP than in vivo.

CONCLUSIONS

Here, we introduce a new method for measuring particle flow during mechanical ventilation and confirm that these particles can be collected and analyzed. VCV resulted in a lower particle flow in vivo but not in EVLP. In all settings, large tidal volumes resulted in increased particle flow. We found that DPPC was significantly increased comparing in vivo with EVLP. This technology may be useful for developing strategies to preserve the lung and has a high potential to detect biomarkers.

Non-invasive approach to diagnosis of pulmonary tuberculosis using microdroplets collected from exhaled air

In this report we present a proof-of-principle study aimed at developing non-invasive diagnostics for pulmonary TB that are based on analyzing TB biomarkers in exhaled microdroplets of lung fluid (MLFs). Samples were collected on electrospun filters recently developed by the authors, and then tested for the presence of Mycobacterium tuberculosis (Mtb) cells, Mtb DNA, and protein biomarkers (secreted Mtb antigens and antigen-specific antibodies). The latter were detected using rapid ultra-sensitive immunochemistry methods developed in our laboratory. Neither Mtb cells (limit of detection, LOD = 1 cell) nor Mtb DNA (LOD ∼ 10 CFU) were found in the MLF samples exhaled by TB patients. However, immunoglobulin A (IgA) was found in over 90% of samples from TB patients and healthy volunteers. Antigen-specific IgA were detected at higher rates in the patient samples as compared to those from nominally healthy volunteers resulting in a modest discrimination level of 72% sensitivity and 58% specificity. As such, this novel, non-invasive and fast breath diagnostic method shows promise for further development.

Evaluation of a new simple collection device for sampling of microparticles in exhaled breath

The microparticle fraction of exhaled breath is of interest for developing clinical biomarkers. Exhaled particles may contain non-volatile components from all parts of the airway system, formed during normal breathing. This study aimed to evaluate a new, simple sampling device, based on impaction, for collecting microparticles from exhaled breath. Performance of the new device was compared with that of the existing SensAbues membrane filter device. The analytical work used liquid chromatography-tandem mass spectrometry methods. The new device collected three subsamples and these were separately analysed from eight individuals. No difference was observed between the centre position (0.91 ng/sample) and the side positions (1.01 ng/sample) using major phosphatidylcholine (PC) 16:0/16:0 as the analyte. Exhaled breath was collected from eight patients on methadone maintenance treatment. The intra-individual variability in measured methadone concentration between the three collectors was 8.7%. In another experiment using patients on methadone maintenance treatment, the sampling efficiency was compared with an established filter device. Compared to the existing device, the efficiency of the new device was 121% greater for methadone and 1450% greater for DPPC. The data from lipid analysis also indicated that a larger fraction of the collected material was from the distal parts. Finally, a study using an optical particle counter indicated that the device preferentially collects the larger particle fraction. In conclusion, this study demonstrates the usefulness of the new device for collecting non-volatile components from exhaled breath. The performance of the device was superior to the filter device in several aspects.

Electret filter collects more exhaled albumin than glass condenser: A method comparison based on human study

In recent years, noninvasive diagnosis based on biomarkers in exhaled breath has been extensively studied. The procedure of biomarker collection is a key step. However, the traditional condenser method has low efficacy in collecting nonvolatile compounds especially the protein biomarkers in breath. To solve this deficiency, here we propose an electret filter method.Exhaled breath of 6 volunteers was collected with a glass condenser and an electret filter. The amount of albumin was analyzed. Furthermore, the difference of exhaled albumin between smokers and nonsmokers was evaluated.The electret filter method collected more albumin than the glass condenser method at the same breath volume level (P < .01). Smokers exhaling more albumin than nonsmokers were also observed (P < .01).The electret filter is capable of collecting proteins more effectively than the condenser method. In addition, smokers tend to exhale more albumin than nonsmokers.