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

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.

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.

Exhaled phospholipid transfer protein and hepatocyte growth factor receptor in lung adenocarcinoma

BACKGROUND

Screening decreases mortality among lung cancer patients but is not widely implemented, thus there is an unmet need for an easily accessible non-invasive method to enable early diagnosis. Particles in exhaled air offer a promising such diagnostic tool. We investigated the validity of a particles in exhaled air device (PExA) to measure the particle flow rate (PFR) and collect exhaled breath particles (EBP) to diagnose primary lung adenocarcinoma (LUAD).

METHODS

Seventeen patients listed for resection of LUAD stages IA-IIIA and 18 non-cancer surgical control patients were enrolled. EBP were collected before and after surgery for LUAD, and once for controls. Proteomic analysis was carried out using a proximity extension assay technology. Results were validated in both plasma from the same cohort and with microarray data from healthy lung tissue and LUAD tissue in the GSE10072 dataset.

RESULTS

Of the 92 proteins analyzed, levels of five proteins in EBP were significantly higher in the LUAD patients compared to controls. Levels of phospholipid transfer protein (PLTP) and hepatocyte growth factor receptor (MET) decreased in LUAD patients after surgery compared to control patients. PFR was significantly higher in the LUAD cohort at all timepoints compared to the control group. MET in plasma correlated significantly with MET in EBP.

CONCLUSION

Collection of EBP and measuring of PFR has never been performed in patients with LUAD. In the present study PFR alone could distinguish between LUAD and patients without LUAD. PLTP and MET were identified as potential biomarkers to evaluate successful tumor excision.

New insight: particle flow rate from the airways as an indicator of cardiac failure in the intensive care unit

AIMS

Exhaled breath particles have been explored for diagnosing different lung diseases. We recently showed in an experimental model that different cardiac output results in different particle flow rate (PFR) from the airways. Given the well-known close relationship between impaired cardiac function and respiratory failure, we hypothesized that PFR in exhaled air can be used to detect cardiac failure.

METHODS

PFR was analysed using a customized PExA device. Particles in the range of 0.41-4.55 μm were measured. The included patients (n = 20) underwent cardiac surgery and received mechanical ventilation as a part of routine post-operative care. Ten patients with clinical signs of pronounced post-operative haemodynamic instability and need for inotrope or mechanical support had been selected to the cardiac failure group. The control group consisted of 10 patients without signs of cardiac failure.

RESULTS

The patients in cardiac failure group required inotropic support in the form of dobutamine (9/10), epinephrine (2/10), or levosimendan (4/10) or use of an intra-aortic balloon pump (4/10). There was no use of inotropes or mechanical support devices among the controls. All patients in the cardiac failure group had pre-operative left ventricular ejection fraction ≤40% compared with the control group, whose pre-operative ejection fraction was ≥50%, P < 0.001. Patients with cardiac failure had significantly longer median total time in mechanical ventilation compared with the patients in the control group: 53.5 h (IQR 6.8-116101.0 h) and 4.5 h (IQR 4.0-5.5 h), respectively, P < 0.001, and the median length of stay in the ICU, 165 h (IQR 28-192 h) and 22 h (IQR 20-23.5 h), respectively, P = 0.007. Median PFR in patients with cardiac failure was higher than PFR in those with normal cardiac function: 80.9 particles/min (interquartile range (IQR) 25.8-336.6 particles/min), vs. 15.3 particles/min (IQR 8.1-17.7 particles/min), respectively, P < 0.001. Median particle mass was 8.95 ng (IQR 1.68-41.73 ng) in the cardiac failure group and 0.75 ng (IQR 0.18-1.45 ng) in the control group, P = 0.002.

CONCLUSIONS

Patients with post-operative cardiac failure following cardiac surgery exhibited an increase in exhaled particle mass and PFR compared with the control group, indicating a significant difference between those two groups. The increase in particle mass and PFR in the absence of respiratory pathologies may indicate cardiac failure. In comparison with controls, impaired cardiac function was also associated with different composition of the particles regarding their size distribution.

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

Monitoring lung injury with particle flow rate in LPS- and COVID-19-induced ARDS

In severe acute respiratory distress syndrome (ARDS), extracorporeal membrane oxygenation (ECMO) is a life-prolonging treatment, especially among COVID-19 patients. Evaluation of lung injury progression is challenging with current techniques. Diagnostic imaging or invasive diagnostics are risky given the difficulties of intra-hospital transportation, contraindication of biopsies, and the potential for the spread of infections, such as in COVID-19 patients. We have recently shown that particle flow rate (PFR) from exhaled breath could be a noninvasive, early detection method for ARDS during mechanical ventilation. We hypothesized that PFR could also measure the progress of lung injury during ECMO treatment. Lipopolysaccharide (LPS) was thus used to induce ARDS in pigs under mechanical ventilation. Eight were connected to ECMO, whereas seven animals were not. In addition, six animals received sham treatment with saline. Four human patients with ECMO and ARDS were also monitored. In the pigs, as lung injury ensued, the PFR dramatically increased and a particular spike followed the establishment of ECMO in the LPS-treated animals. PFR remained elevated in all animals with no signs of lung recovery. In the human patients, in the two that recovered, PFR decreased. In the two whose lung function deteriorated while on ECMO, there was increased PFR with no sign of recovery in lung function. The present results indicate that real-time monitoring of PFR may be a new, complementary approach in the clinic for measurement of the extent of lung injury and recovery over time in ECMO patients with ARDS.

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

Increased particle flow rate from airways precedes clinical signs of ARDS in a porcine model of LPS-induced acute lung injury

Acute respiratory distress syndrome (ARDS) is a common cause of death in the intensive care unit, with mortality rates of ~30-40%. To reduce invasive diagnostics such as bronchoalveolar lavage and time-consuming in-hospital transports for imaging diagnostics, we hypothesized that particle flow rate (PFR) pattern from the airways could be an early detection method and contribute to improving diagnostics and optimizing personalized therapies. Porcine models were ventilated mechanically. Lipopolysaccharide (LPS) was administered endotracheally and in the pulmonary artery to induce ARDS. PFR was measured using a customized particles in exhaled air (PExA 2.0) device. In contrast to control animals undergoing mechanical ventilation and receiving saline administration, animals who received LPS developed ARDS according to clinical guidelines and histologic assessment. Plasma levels of TNF-α and IL-6 increased significantly compared with baseline after 120 and 180 min, respectively. On the other hand, the PFR significantly increased and peaked 60 min after LPS administration, i.e., ~30 min before any ARDS stage was observed with other well-established outcome measurements such as hypoxemia, increased inspiratory pressure, and lower tidal volumes or plasma cytokine levels. The present results imply that PFR could be used to detect early biomarkers or as a clinical indicator for the onset of ARDS.