Multiple breath washout test data for healthy controls

Deployment-Related Respiratory Disease: Where Are We?

Military personnel and veterans who have deployed to Afghanistan, Iraq, and parts of Southwest Asia (SWA) since 1990 are at risk of developing a host of respiratory symptoms and deployment-related respiratory diseases (DRRDs). This review aims to summarize our current understanding of DRRD and inform pulmonary practitioners of recent updates to DRRD screening, diagnosis, evaluation, and management. The most common respiratory diseases in these patients include asthma, chronic sinonasal disease, laryngeal disease/dysfunction, and distal lung disease. Pulmonary function testing and chest imaging are the most commonly used diagnostic tools, but techniques such as lung clearance index testing via multiple breath washout, forced oscillation testing/impulse oscillometry, and quantitative chest computed tomography (CT) assessment appear promising as noninvasive modalities to aid in lung disease detection in this population. We also summarize guidance on conducting an occupational and deployment exposure history as well as recommendations for testing. Finally, we discuss the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics Act of 2022 (PACT Act) that includes a list of health conditions that are "presumptively" considered to be related to SWA military deployment toxic exposures, and provide resources for clinicians who evaluate and treat patients with DRRD.

Multiple Breath Washout for Early Assessment of Pulmonary Complications in Patients With Primary Antibody Deficiencies: An Observational Study in Pediatric Age

BACKGROUND

In primary antibody deficiencies (PADs), pulmonary complications are the main cause of morbidity, despite immunoglobulin substitutive therapy, antibiotic treatment of exacerbations, and respiratory physiotherapy. Current Italian recommendations for surveillance of PADs respiratory complications include an annual assessment of spirometry and execution of chest high-resolution computed tomography (HRCT) every 4 years.

OBJECTIVE

This study aimed to evaluate the effectiveness of the lung clearance index (LCI) as an early marker of lung damage in patients with PADs. LCI is measured by multiple breath washout (MBW), a non-invasive and highly specific test widely used in patients with cystic fibrosis (CF).

METHODS

Pediatric patients with PADs (n = 17, 10 male, 7 female, and age range 5-15 years) underwent baseline assessment of lung involvement with chest HRCT, spirometry, and multiple breath nitrogen washout. Among them, 13 patients were followed up to repeat HRCT after 4 years, while performing pulmonary function tests annually. Their baseline and follow-up LCI and forced expiratory volume at 1 s (FEV1) values were compared, taking HRCT as the gold standard, using logistic regression analysis.

RESULTS

Lung clearance index [odds ratio (OR) 2.3 (confidence interval (CI) 0.1-52) at baseline, OR 3.9 (CI 0.2-191) at follow-up] has a stronger discriminating power between altered and normal HRCT rather than FEV1 [OR 0.6 (CI 0.2-2) at baseline, OR 1.6 (CI 0.1-13.6) at follow-up].

CONCLUSION

Within the context of a limited sample size, LCI seems to be more predictive of HRCT alterations than FEV1 and more sensitive than HRCT in detecting non-uniform ventilation in the absence of bronchiectasis. A study of a larger cohort of pediatric patients followed longitudinally in adulthood is needed to challenge these findings.

Role of Particulate Matter from Afghanistan and Iraq in Deployment-Related Lung Disease

Approximately 3 million United States military personnel and contractors were deployed to Southwest Asia and Afghanistan over the past two decades. After returning to the United States, many developed persistent respiratory symptoms, including those due to asthma, rhinosinusitis, bronchiolitis, and others, which we collectively refer to as deployment-related lung diseases (DRLD). The mechanisms of different DRLD have not been well defined. Limited studies from us and others suggest that multiple factors and biological signaling pathways contribute to the onset of DRLD. These include, but are not limited to, exposures to high levels of particulate matter (PM) from sandstorms, burn pit combustion products, improvised explosive devices, and diesel exhaust particles. Once inhaled, these hazardous substances can activate lung immune and structural cells to initiate numerous cell-signaling pathways such as oxidative stress, Toll-like receptors, and cytokine-driven cell injury (e.g., interleukin-33). These biological events may lead to a pro-inflammatory response and airway hyperresponsiveness. Additionally, exposures to PM and other environmental hazards may predispose military personnel and contractors to more severe disease due to the interactions of those hazardous materials with subsequent exposures to allergens and cigarette smoke. Understanding how airborne exposures during deployment contribute to DRLD may identify effective targets to alleviate respiratory diseases and improve quality of life in veterans and active duty military personnel.

Multiple breath washout: A noninvasive tool for identifying lung disease in symptomatic military deployers

RATIONALE

Military deployments to austere environments since November 9, 2001 may put "deployers" at risk for respiratory disease. Sensitive, noninvasive tools for detecting large and small airways injury are needed to identify early disease and help inform management for this at-risk population.

OBJECTIVES

We examined multiple breath washout (MBW) as a tool for identifying deployment-related airways disease and assessed host and exposure risk factors compared to healthy controls.

METHODS

Between March 2015 and March 2020, 103 healthy controls and 71 symptomatic deployers with asthma and/or distal lung disease completed a questionnaire, spirometry and MBW testing. SAS v. 9.4 was used to compare MBW parameters between deployers and controls via univariate analyses and adjusted for demographic factors using multiple linear regression.

MEASUREMENTS AND MAIN RESULTS

Deployers were significantly more likely than controls to have an abnormal lung clearance index (LCI) score indicating global ventilation inhomogeneity. Adjusting for sex, smoking status, smoking pack-years and body mass index, LCI scores were significantly more abnormal among those with deployment-related asthma and distal lung disease compared to controls. The unadjusted variable Sacin (a marker of ventilation inhomogeneity in the acinar airways) was higher and thus more abnormal in those with both proximal and distal airways disease. Deployers who reported more frequent exposure to explosive blasts had significantly higher LCI scores.

CONCLUSIONS

This study demonstrates the utility of MBW in evaluating exposure-related airways disease in symptomatic military personnel following deployment to austere environments, and is the first to link exposure to explosive blasts to measurable small airways injury.