Mucociliary and cough clearance as a biomarker for therapeutic development

EFFECT OF HIGH-FREQUENCY CHEST WALL OSCILLATION ON CLINICAL INDICES OF COMMUNITY-ACQUIRED PNEUMONIA IN CHILDREN

OBJECTIVE

The aim: To study the effect of high-frequency chest wall oscillation (HFCWO) on clinical indices of community-acquired pneumonia (CAP) in children.

PATIENTS AND METHODS

Materials and methods: The main clinical symptoms were assessed in 107 children (girls - 45.79% and boys - 54.21%) aged 6 to 17 years with acute and uncomplicated course of CAP of moderate severity. The main group (MG) consisted of 55 children who were prescribed basic therapy (BT) in combination with HFCWO procedures. The control group (CG) comprised 52 children who received BT exclusively.

RESULTS

Results: In the children of MG, the intensity of cough decreased to 0.28 ± 0.06 points compared with children of CG - 0.5 ± 0.07 points (p <0.05) on the 10th day of treatment. A positive dynamics of CAP in the form of the amount of sputum reduction was revealed in the MG children up to 0.06 ± 0.03 points compared with the CG children - 0.42 ± 0.07 (p <0.05). On the 10th day of therapy the MG children with CAP had decrease in the number of râles in the lungs up to 0.08 ± 0.04 points compared with those of CG - 0.4 ± 0.07 points (p <0.05).

CONCLUSION

Conclusions: High efficacy of HFCWO method in complex treatment of CAP in children is confirmed by the dynamics of the main clinical symptoms, such as reduction of intensity and productivity of cough as well as absence shortness of breath and moist râles in the lungs. The data obtained indicate recovery of mucociliary clearance (MCC) functions and the bronchopulmonary system as a whole.

The Use of Single Photon Emission Computed Tomography in Aerosol Medicine

Imaging of radiolabeled aerosols provides useful in vivo data on both the initial site of deposition and its subsequent transport by mucociliary clearance and epithelial permeability. Single Photon Emission Computed Tomography (SPECT) uses a gamma camera with multiple rotating heads to produce three-dimensional (3D) images of inhaled radioaerosol labeled with technetium-99m. This enables total lung deposition and its 3D regional distribution to be quantified. Aligned 3D images of lung structure allow deposition data to be related to lung anatomy. Mucociliary clearance or epithelial permeability can be assessed from a time series of SPECT aerosol images. SPECT is slightly superior to planar imaging for measuring total lung deposition. However, it is more complex to use, and for studies where total lung deposition is the endpoint, planar imaging is recommended. However, SPECT has been shown to be clearly superior to planar imaging for assessing regional distribution of aerosol and is the method of choice for this purpose. It therefore has applications in studying the influence of regional deposition on clinical effectiveness and also in validating computer models of deposition. The inability to directly radiolabel drug molecules with ^99mTc is a clear disadvantage of SPECT and limits its potential use for pharmacokinetic studies. SPECT provides a wealth of data on aerosol deposition, which has been relatively underused at present. Optimal methods of analyzing and interpreting the data need to be developed. SPECT can also, in principle, provide detailed information of mucociliary clearance and has the potential to significantly improve knowledge of this process and hence clarify the role of clearance as a biomarker.

Imaging Aerosol Deposition with Two-Dimensional Gamma Scintigraphy

Several imaging modalities have been employed to quantify lung dose and the distribution of the dose of orally inhaled aerosols in vivo. Two-dimensional (2D, or planar) imaging using gamma scintigraphy is the most widely used of these modalities. Two-dimensional gamma scintigraphy studies are accomplished using a single- or dual-headed gamma camera. The formulation to be tested is admixed with the gamma emitting radioisotope ^99mtechnetium, which serves as a surrogate for the drug. This article provides details as to how 2D gamma scintigraphy images should be acquired and analyzed using recently standardized methods. Based on the new guidelines, the investigator should confirm that the drug formulation is unchanged with the addition of the radioisotope, determine the amount of radioactivity needed for inhalation to obtain appropriate radioactivity counts in the lungs, perform quality control procedures for the gamma camera, identify the lung borders of the study subject using a reference image such as an X-ray computed tomography scan, a ventilation scan, or a transmission scan, acquire a lung transmission image to correct for attenuation of radioactivity by lung tissue, instruct the subject how to inhale the radiolabel-drug mixture and record associated breathing parameters, acquire anterior and/or posterior views of the lungs and any other regions of interest (i.e., oropharynx, stomach) and assess the acquired images for total and regional dose to the lungs. Total dose should be assessed after identification of the right lung border and appropriate correction for tissue attenuation. Regional dose should be quantified as a normalized outer/inner deposition ratio (O/I) and expressed as the penetration index (PI). Mass balance should be performed as needed. By following the standardized methods, 2D gamma scintigraphy data from studies in different laboratories may be compared and combined, leading to multi-center studies and more rapid development of new medications and devices for inhaled therapies.

Design of In Vivo Deposition and Clearance Experiments

Experiments designed to image in vivo deposition of radiolabel-drug mixtures are useful for estimating inhaled drug delivery and for assessing bioequivalence of delivery devices. Validation of the radiolabel-drug mixture is vital to ensure that subsequent imaging is reflective of drug deposition. Application of gamma attenuation corrections allows both total and regional lung deposition of drug to be estimated by two-dimensional (2D) imaging. Imaging methods are also useful for measuring in vivo mucociliary clearance (MC) function. Such measures allow assessment of the efficacy of drugs designed to improve clearance of airway secretions in airway disease. MC rates can be measured by controlled inhalation and gamma camera monitoring of radiolabeled aerosols containing non-permeating tracers. While in vivo MC rates reflect the function of the mucociliary apparatus, they are also dependent on regional deposition patterns of the inhaled aerosol.

Acute and durable effect of inhaled hypertonic saline on mucociliary clearance in adult asthma

Background

Impaired mucus clearance and airway mucus plugging have been shown to occur in moderate–severe asthma, especially during acute exacerbations. In cystic fibrosis, where airway mucus is dehydrated, it has been shown that inhaled hypertonic saline (HS) produces both acute and sustained enhancement of mucociliary clearance (MCC). The current study was designed to assess the acute and sustained effect of inhaled 7% HS on MCC in adult asthma.

Methods

Well-controlled, moderate–severe female asthmatic patients (n=8) were screened with a single test dose of albuterol (four puffs by metered-dose inhaler) followed by HS (7% sodium chloride, 4 mL using PARI LC Star nebuliser). Spirometry was measured pre-treatment and 5 and 30 min post-treatment for safety. MCC was measured using γ-scintigraphy on three separate visits: at baseline, during inhalation and 4 h after a single dose of HS.

Results

MCC was acutely enhanced during HS treatment; mean±sd clearance over 60 min of dynamic imaging (Ave60Clr) was 8.9±7.9% (baseline) versus 23.4±7.6% (acute HS) (p<0.005). However, this enhancement was not maintained over a 4-h period where post-HS treatment Ave60Clr was 9.3±8.2%. In this small cohort we found no decrements in lung function up to 30 min post-treatment (forced expiratory volume in 1 s 97.4±10.0% predicted pre-treatment and 98.9±10.7% predicted 30 min post-treatment).

Conclusion

While MCC was rapidly enhanced during 7% HS treatment there was no effect on MCC at 4 h post-treatment. While these findings may not support aerosolised HS use for maintenance therapy, they do suggest a benefit of treating acute exacerbations in patients with moderate–severe asthma.

Acute inhalation of 7% saline dramatically enhances mucociliary clearance in adult asthmatics, but, unlike in cystic fibrosis, does not provide sustained enhancement 4 h post-treatmenthttps://bit.ly/2Qiae2K

Longitudinal Speech Biomarkers for Automated Alzheimer's Detection

We introduce a novel audio processing architecture, the Open Voice Brain Model (OVBM), improving detection accuracy for Alzheimer's (AD) longitudinal discrimination from spontaneous speech. We also outline the OVBM design methodology leading us to such architecture, which in general can incorporate multimodal biomarkers and target simultaneously several diseases and other AI tasks. Key in our methodology is the use of multiple biomarkers complementing each other, and when two of them uniquely identify different subjects in a target disease we say they are orthogonal. We illustrate the OBVM design methodology by introducing sixteen biomarkers, three of which are orthogonal, demonstrating simultaneous above state-of-the-art discrimination for two apparently unrelated diseases such as AD and COVID-19. Depending on the context, throughout the paper we use OVBM indistinctly to refer to the specific architecture or to the broader design methodology. Inspired by research conducted at the MIT Center for Brain Minds and Machines (CBMM), OVBM combines biomarker implementations of the four modules of intelligence: The brain OS chunks and overlaps audio samples and aggregates biomarker features from the sensory stream and cognitive core creating a multi-modal graph neural network of symbolic compositional models for the target task. In this paper we apply the OVBM design methodology to the automated diagnostic of Alzheimer's Dementia (AD) patients, achieving above state-of-the-art accuracy of 93.8% using only raw audio, while extracting a personalized subject saliency map designed to longitudinally track relative disease progression using multiple biomarkers, 16 in the reported AD task. The ultimate aim is to help medical practice by detecting onset and treatment impact so that intervention options can be longitudinally tested. Using the OBVM design methodology, we introduce a novel lung and respiratory tract biomarker created using 200,000+ cough samples to pre-train a model discriminating cough cultural origin. Transfer Learning is subsequently used to incorporate features from this model into various other biomarker-based OVBM architectures. This biomarker yields consistent improvements in AD detection in all the starting OBVM biomarker architecture combinations we tried. This cough dataset sets a new benchmark as the largest audio health dataset with 30,000+ subjects participating in April 2020, demonstrating for the first time cough cultural bias.

Quantitative Assessment of Regional Mucociliary Clearance in Smokers with Mild-to-Moderate Chronic Obstructive Pulmonary Disease and Chronic Bronchitis from Planar Radionuclide Imaging

Background: Mucociliary clearance (MCC) rate from the lung has been shown to be reduced in chronic obstructive pulmonary disease (COPD). This study investigates the value of regional clearance measurements in assessing MCC in mild-to-moderate disease. Methods: Measurement of lung MCC using planar gamma camera imaging was performed in three groups: (i) healthy nonsmoking controls (NSCs) (n = 9), (ii) smoking controls (SCs) who were current smokers with normal lung function (n = 10), and (iii) current smokers with mild-to-moderate COPD and bronchitis (n = 15). The mean (±standard deviation) forced expiratory volumes at 1 second (FEV1) for the three groups were 109 (± 18), 94 (± 5), and 78 (± 12), respectively. After inhalation of a technetium-99m labeled aerosol, planar imaging was performed over 4 hours and then at 24 hours. Both lung clearance and tracheobronchial clearance (TBC) (normalized to 24 hours clearance) were calculated for inner and outer lung zones. Inner zone clearance was corrected for input from the outer zone. A novel parameter, the bronchial airways clearance index (BACI), which combined clearance data from both zones, was also evaluated. Regional results were compared with whole lung clearance in the same subjects. Results: Corrected inner zone clearance at 3 hours was not reduced compared with NSC in either SCs or COPD. Outer zone clearance was higher in COPD than in the other groups. Corrected inner zone TBC showed significant reductions in SC and COPD compared with NSC. BACI was significantly reduced in COPD compared with NSC and also correlated with FEV1. The mean BACI for SC was also reduced compared with NSC, but the distribution of results was bimodal, with a significant proportion of subjects having values in the NSC range. Conclusions: Regional MCC demonstrated differences between NSCs, SCs, and subjects with mild-to-moderate COPD, which were not apparent with whole lung measurements.

Oxidative stress, autophagy and airway ion transport

Mucociliary clearance is critically important in protecting the airways from infection and from the harmful effects of smoke and various inspired substances known to induce oxidative stress and persistent inflammation. An essential feature of the clearance mechanism involves regulation of the periciliary liquid layer on the surface of the airway epithelium, which is necessary for normal ciliary beating and maintenance of mucus hydration. The underlying ion transport processes associated with airway surface hydration include epithelial Na⁺ channel-dependent Na⁺ absorption occurring in parallel with CFTR and Ca²⁺-activated Cl^- channel-dependent anion secretion, which are coordinately regulated to control the depth of the periciliary liquid layer. Oxidative stress is known to cause both acute and chronic effects on airway ion transport function, and an increasing number of studies in the past few years have identified an important role for autophagy as part of the physiological response to the damaging effects of oxidation. In this review, recent studies addressing the influence of oxidative stress and autophagy on airway ion transport pathways, along with results showing the potential of autophagy modulators in restoring the function of ion channels involved in transepithelial electrolyte transport necessary for effective mucociliary clearance, are presented.

Biodistribution, Clearance, and Long-Term Fate of Clinically Relevant Nanomaterials

Realization of the immense potential of nanomaterials for biomedical applications will require a thorough understanding of how they interact with cells, tissues, and organs. There is evidence that, depending on their physicochemical properties and subsequent interactions, nanomaterials are indeed taken up by cells. However, the subsequent release and/or intracellular degradation of the materials, transfer to other cells, and/or translocation across tissue barriers are still poorly understood. The involvement of these cellular clearance mechanisms strongly influences the long-term fate of used nanomaterials, especially if one also considers repeated exposure. Several nanomaterials, such as liposomes and iron oxide, gold, or silica nanoparticles, are already approved by the American Food and Drug Administration for clinical trials; however, there is still a huge gap of knowledge concerning their fate in the body. Herein, clinically relevant nanomaterials, their possible modes of exposure, as well as the biological barriers they must overcome to be effective are reviewed. Furthermore, the biodistribution and kinetics of nanomaterials and their modes of clearance are discussed, knowledge of the long-term fates of a selection of nanomaterials is summarized, and the critical points that must be considered for future research are addressed.

Mucociliary clearance: pathophysiological aspects

Mucociliary clearance has long been known to be a significant innate defence mechanism against inhaled microbes and irritants. Important knowledge has been gathered regarding the anatomy and physiology of this system, and in recent years, extensive studies of the pathophysiology related to lung diseases characterized by defective mucus clearance have resulted in a variety of therapies, which might be able to enhance clearance from the lungs. In addition, ways to study in vivo mucociliary clearance in humans have been developed. This can be used as a means to assess the effect of different pharmacological interventions on clearance rate, to study the importance of defective mucus clearance in different lung diseases or as a diagnostic tool in the work-up of patients with recurrent airway diseases. The aim of this review is to provide an overview of the anatomy, physiology, pathophysiology, and clinical aspects of mucociliary clearance and to present a clinically applicable test that can be used for in vivo assessment of mucociliary clearance in patients. In addition, the reader will be presented with a protocol for this test, which has been validated and used as a diagnostic routine tool in the work-up of patients suspected for primary ciliary dyskinesia at Rigshospitalet, Denmark for over a decade.

Effect of inhaled dry powder mannitol on mucus and its clearance

Insufficient hydration at the airway surface can make mucus adherent and poorly cleared. Cough, the major mechanism of mucus clearance in disease, is ineffective when mucus is adhesive. Inhaled mannitol creates an osmotic drive for water to move into the airway lumen. The consequent increased hydration of the airway surface decreases the adherence of mucus to the epithelium, facilitates the coupling of mucus and cilia thereby increasing mucus clearance. Inhaled mannitol also promotes effective coughing and stimulates mucociliary clearance. The beneficial effect of mannitol on mucus and its clearance has been demonstrated in patients with asthma, bronchiectasis and cystic fibrosis. Inhaled dry powder mannitol (Bronchitol™) is promising to be an effective treatment for the clearance of retained airway secretions.

The co-imaging of gamma camera measurements of aerosol deposition and respiratory anatomy

The use of gamma camera imaging following the inhalation of a radiolabel has been widely used by researchers to investigate the fate of inhaled aerosols. The application of two-dimensional (2D) planar gamma scintigraphy and single-photon emission computed tomography (SPECT) to the study of inhaled aerosols is discussed in this review. Information on co-localized anatomy can be derived from other imaging techniques such as krypton ventilation scans and low- and high-resolution X-ray computed tomography (CT). Radionuclide imaging, combined with information on anatomy, is a potentially useful approach when the understanding of regional deposition within the lung is central to research objectives for following disease progression and for the evaluation of therapeutic intervention.

Multisite comparison of mucociliary and cough clearance measures using standardized methods

BACKGROUND

A standardized protocol for measuring mucociliary (MCC) and cough clearance (CC) was developed and tested at the University of North Carolina at Chapel Hill, NC (UNC), Johns Hopkins University (JHU), and the University of Pittsburgh (Pitt).

METHODS

A total of 50 healthy nonsmoking adults with normal lung function were studied at the three sites: 30 [21 males/9 females (21M/9F)] at UNC, 10 (6M/4F) at JHU, and 10 (4M/6F) at Pitt. Subjects inhaled an aerosol of (99m)technetium sulfur colloid in 0.9% saline (mass median aerodynamic diameter=5.4 μm) under controlled breathing conditions (500 mL/sec, 30 breaths/min) by following a metronome and flow signal from a commercial dosimeter. Following inhalation, subjects sat in front of a gamma camera as sequential lung images were acquired for 60 min. Subjects then coughed 60 times, and images were acquired after each set of 20 coughs, i.e., at 70, 80, and 90 min. Subjects returned to the laboratory approximately 24 hr later for a final image of residual lung activity. Initial aerosol distribution was measured as a central/peripheral (C/P) ratio of activity. MCC/CC was expressed as the area under the retention versus time curve over 90 min (AUC90).

RESULTS

A multivariate analysis of clearance versus time with site and C/P as covariates showed no significant site-specific differences. Interestingly, MCC/CC was greater in females (n=19) versus males (n=31), with AUC90=0.84 ± 0.11 and 0.90±0.07, respectively (p=0.03), for the combined data set from all sites (not significant for any given site). There were no gender differences for either C/P ratio or 24-hr clearance.

CONCLUSIONS

This standardized protocol may prove beneficial in multicenter trials for testing new therapies that are designed to improve MCC/CC.

Comparison of 133 xenon ventilation equilibrium scan (XV) and 99m technetium transmission (TT) scan for use in regional lung analysis by 2D gamma scintigraphy in healthy and cystic fibrosis lungs

BACKGROUND

Quantification of particle deposition in the lung by gamma scintigraphy requires a reference image for location of regions of interest (ROIs) and normalization to lung thickness. In various laboratories, the reference image is made by a transmission scan ((57)Co or (99m)Tc) or gas ventilation scan ((133)Xe or (81)Kr). There has not been a direct comparison of measures from the two methods.

METHODS

We compared (99m)Tc transmission scans to (133)Xe equilibrium ventilation scans as reference images for 38 healthy subjects and 14 cystic fibrosis (CF) patients for their effects on measures of regional particle deposition: the central-to-peripheral ratio of lung counts (C/P); and ROI area versus forced vital capacity. Whole right lung ROI was based on either an isocontour threshold of three times the soft tissue transmission (TT) or a threshold of 20% of peak xenon ventilation counts (XV). We used a central ROI drawn to 50% of height and of width of the whole right lung ROI and placed along the left lung margin and centered vertically.

RESULTS

In general, the correlation of normalized C/P (nC/P) between the two methods was strong. However, the value of nC/P was significantly smaller for the XV method than the TT method. Regression equations for the relationship of nC/P between the two methods were, for healthy subjects, y=0.75x+0.61, R(2)=0.64 using rectangular ROIs and y=0.76x+0.45, R(2)=0.66 using isocontour ROIs; and for CF patients, y=0.94x+0.46, R(2)=0.43 and y=0.85x+0.42, R(2)=0.41, respectively.

CONCLUSIONS

(1) A transmission scan with an isocontour outline in combination with a rectangular central region to define the lung borders may be more useful than a ventilation scan. (2) Close correlation of nC/Ps measured by transmission or gas ventilation should allow confident comparison of values determined by the two methods.

Challenges in assessing regional distribution of inhaled drug in the human lungs

INTRODUCTION

Both the total amount of drug deposited in the lungs (whole lung deposition) and the amount deposited in different lung regions (regional lung deposition) are potentially important factors that determine the safety and efficacy of inhaled drugs. Radionuclide imaging is well established for quantifying the whole lung deposition of inhaled drugs, but the assessment of regional lung deposition is less straightforward, because of the complex nature of the lung anatomy.

AREAS COVERED

This review describes the challenges and problems associated with quantifying regional lung deposition by the two-dimensional (2D) radionuclide imaging method of gamma scintigraphy, and by the three-dimensional (3D) radionuclide imaging methods of single-photon-emission computed tomography (SPECT) and positron-emission tomography (PET). The advantages and disadvantages of each method for assessing regional lung deposition are discussed.

EXPERT OPINION

Owing to its 2D nature, gamma scintigraphy provides limited information about regional lung deposition. SPECT provides regional lung deposition data in three dimensions, but usually involves a (99m)Tc radiolabel. PET enables the regional lung deposition of radiolabeled drug molecules to be quantified in three dimensions, but poses the greatest logistical and technical difficulties. Despite their more challenging nature, 3D imaging methods should be considered as an alternative to gamma scintigraphy whenever the determination of regional lung deposition of pharmaceutical aerosols is a major study objective.