The Prevalence Of Small Airways Dysfunction In Asthma Patients And The Impact On The Asthma Control

Asthma, which are one of the most important causes of morbidity and mortality both in the world and in our country, constitute a very serious social and economic burden. An estimated 300 million people suffer from asthma worldwide, which is a major public health problem. Asthma is complex and heterogeneous chronic airway diseases that require a multifaceted approach. In asthma, small airways represent key regions of airflow obstruction. Although small airway dysfunction is known in chronic airway diseases, the importance of small airway dysfunction on disease control, exacerbations and quality of life, and the importance of taking place among treatable targets is not clear. Thus, there is an unmet need to assess its role in the control of the disease. Therefore, our primary aim in the study is to determine the frequency of small airway dysfunction measured by impulse oscillometry in Asthma patients. Our secondary aim is to evaluate the role of small airway dysfunction in disease severity, disease phenotypes, disease control, quality of life and its effect on predicting the risk of exacerbation and its role among treatable targets in Asthma.

This is a prospective cross-sectional interventional design. 73 asthmatic patients who applied to Mersin University Faculty of Medicine Hospital Chest Diseases Clinic between 01.10.2019-01.04.2020 will be taken. 35 healthy volunteers who were admitted to our clinic within the same date range will be taken as control group. Impulse oscillometric pulmonary function tests will be performed to all participants. Thorax computed tomography will be performed to evaluate small airway dysfunction. To evaluate the degree of disease inflammation and phenotype in asthma patients, nitric oxide measurements will be made in the breath air with fractional exhaled nitric oxide (FENO) device. The blood eosinophil level will be studied to determine the asthma phenotype.Asthma control test (ACT) will be applied to measure symptom control in patients with asthma. Asthma quality of life scale (AQLQ) will be applied to determine the quality of life in asthmatic patients. All patients will be followed for 1 year to record the number of exacerbations requiring emergency and hospital admissions for asthma. The effect of small airway dysfunction on asthma group, on the disease severity and control degree, disease phenotypes and quality of life, and the effect on the risk of exacerbation will be analyzed.

Impulse oscillometric pulmonary function tests and spirometric pulmonary function test will be performed to all asthmatic patients.To evaluate the degree of disease inflammation and phenotype, nitric oxide measurements will be made in the breath air with fractional exhaled nitric oxide (FENO) device. Blood eosinophil values will be examined. Thorax computed tomography will be performed to evaluate small airway dysfunction. Asthma control test (ACT) and asthma quality of life scale (AQLQ) will be applied. All patients will be followed for 1 year to record the number of exacerbations requiring emergency and hospital admissions for asthma.

Impulse oscillometric pulmonary function test, spirometric pulmonary function test and chest x ray will be performed.

We will used respiratory resistance at 5 and 20 Hz (R5 and R20, respectively) for the analyses. R5 and R20 are regarded as reflecting total and proximal airway resistance, respectively, and the fall in resistance from R5 to R20 (R5-R20) will used as a surrogate for the resistance of small airways.

Indirect changes caused by the small airways on the lung parenchyma will be detected by computed tomography (CT).

Residual volume (RV) and total lung capacity (TLC) will be measured by body plethysmography test to determine small airway dysfunction.

In the asthma group, each participant will be followed for 1 year in terms of recording exacerbations.

Forced expiratory volume in 1 second (fev1) change will be evaluated by spirometric pulmonary function test.

Forced expiratory volume in 1 second (fev1) change over one year period will be evaluated with spirometric pulmonary function test during recruitment and 1st year of follow-up.

Fractional Exhaled Nitric Oxide (FENO) test will be used as an indicator of inflammation in determining the relationship between airway inflammation and small airway dysfunction.

The relationship between blood inflammation cells and small airway dysfunction will be evaluated by complete blood count ( CBC).

Inclusion Criteria: Asthma group Participants who applied to the chest diseases clinic of Mersin University Hospital, between October 1, 2019 and April 1, 2020 Participants who were diagnosed asthma with spirometry test Reading and signing Informed Consent Form Participants must be older than 18 years Healthy control group To apply to the chest diseases clinic of Mersin University Hospital between October 1, 2019 and April 1, 2020 Reading and signing informed consent form Participants must be older than 18 years Must have no lung disease Must have no smoking history Exclusion Criteria: Participants who do not sign the Informed Consent Form Under the age of 18 years Pregnant women Participants who with a history of cancer in the past 5 years Participants who previously had lung surgery Participants who with Interstitial Lung Disease Participants who with respiratory muscle disease Participants who with active pulmonary tuberculosis Participants who can not perform respiratory function tests

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