Asthma Diagnosis: Anatomy and Pathophysiology of Asthma Karen Meyerson, MSN, RN, FNP-C, AE-C Asthma Network of West Michigan April 21, 2009 Acknowledgements: LeRoy M. Graham, MD, Atlanta, GA
Definition of Asthma Chronic inflammatory disease of the airways characterized by: Recurrent episodes of wheezing Shortness of breath Chest tightness/pain Coughing Airflow limitation is at least partially reversible Airways are supersensitive and react to a variety of stimuli or triggers
Asthma Pathophysiology In response to a trigger: Airway inflammation Bronchial smooth muscles constriction (bronchospasm) Increased mucus production The airways become narrow and breathing becomes difficult
Normal Airways
Asthma Airways
Mechanisms Underlying the Definition of Asthma Risk Factors (for development of asthma) INFLAMMATION Airway Hyperresponsiveness Airflow Limitation Risk Factors (triggers) Symptoms
Asthma Airways Before 10 Minutes After Allergen Challenge
Airway Remodeling Normal Jeffery P. Asthma. 1998. Asthmatic
The Tip of the Iceberg ASTHMA Symptoms Airflow obstruction Bronchial hyperresponsiveness Airway inflammation National Asthma Education and Prevention Program. Highlights of the Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma. Bethesda, MD., May 1997. NIH Publication No. 97-4051A.
Factors Predicting Persistent Asthma Family history of asthma (maternal > paternal) Atopy (IgE/positive skin tests, eczema, rhinitis) Allergen exposure (dust mites / animals) Viral (RSV) infection Gender (males > females) Smoking (passive or active) The strongest predictor for wheezing that develops into asthma is ATOPY
Symptoms Asthma Diagnosis Medical history Physical exam Measurements of lung function Diurnal variation in peak flow Evaluation of allergic status Exclude alternative diagnoses Bronchiolitis, cystic fibrosis, GERD, foreign body aspiration
Asthma Diagnosis Assessing Symptoms Cough Wheeze Dyspnea Nocturnal symptoms Activity affected? Recurrent episodes of cough (+ wheeze) are frequently due to asthma Coughing may be the only symptom present
Asthma Diagnosis Medical History Repeated cough, wheeze, chest tightness Repeated diagnoses of reactive airway disease, allergic bronchitis or wheezy bronchitis Symptoms worsened by viral infection, smoke, allergens, exercise, weather Symptoms occur/worsen at night Reversible airflow limitation Wheezing may or may not be present
Coughing, wheezing Asthma Diagnosis Physical Exam Prolonged forced expiration Use of accessory muscles Retractions Hyperexpansion of the chest Signs of other allergic diseases: Atopic dermatitis Allergic rhinitis Physical examination of the chest may be normal
Asthma Predictive Index (API) High risk children (under age 3) who: have had > 4 wheezing episodes in the past year that lasted more than one day and affected sleep are significantly more likely to have persistent asthma after the age of 5 if they have either (1) of the following: One major criteria Parent with asthma Physician diagnosis of atopic dermatitis Evidence of sensitization to aeroallergens OR Two minor criteria Evidence of sensitization to foods >4 percent blood eosinophilia Wheezing apart from colds Castro-Rodriguez J et al. AJRCCM 2000; 162:1403-1406.
Asthma Predictive Index (API) Birth cohort followed through 13 years of age. 76% of children diagnosed with asthma after 6 years of age had a positive asthma predictive index before 3 years of age. 97% of children who did not have asthma after 6 years of age had a negative asthma predictive index before 3 years of age. Castro-Rodriguez J et al. AJRCCM 2000; 162:1403-1406.
Asthma Diagnosis Measurements of Lung Function FEV 1 (Forced Expiratory Volume in 1 Second) this is the volume of air expired in the first second during maximal expiratory effort. The FEV 1 is reduced in both obstructive and restrictive lung disease. FVC (Forced Vital Capacity) this is the total volume of air expired after a full inspiration. FEV 1 /FVC this is the percentage of the vital capacity which is expired in the first second of maximal expiration.
Spirometry: Flow-Volume Loop Obstruction
Asthma Diagnosis Measurements of Lung Function Spirometry: An FEV 1 response of >12% post-bronchodilator is suggestive of asthma BUT, Spirometry is difficult in children <4 years old Some children cannot perform spirometry adequately until >7 years of age Alternative assessment: PEF variability
Asthma Diagnosis Cough especially if: after exertion breathing cold air at night after colds paroxysmal Wheezing tightness noisy breathing? Dyspnea (Breathlessness) especially if: intermittent or variable after exertion at night
Asthma Diagnosis Cough especially if: after exertion breathing cold air at night after colds paroxysmal Wheezing tightness noisy breathing? Dyspnea (Breathlessness) especially if: intermittent or variable after exertion at night
Asthma Diagnosis Cough especially if: after exertion breathing cold air at night after colds paroxysmal Wheezing tightness noisy breathing? Dyspnea (Breathlessness) especially if: intermittent or variable after exertion at night
Asthma Diagnosis Cough especially if: after exertion breathing cold air at night after colds paroxysmal Wheezing tightness noisy breathing? Dyspnea (Breathlessness) especially if: intermittent or variable after exertion at night
Asthma Diagnosis Cough especially if: after exertion breathing cold air at night after colds paroxysmal Wheezing tightness noisy breathing Dyspnea (Breathlessness) especially if: intermittent or variable after exertion at night
Questions? Download the Guidelines at: http://www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf Download the Summary Report at: http://www.nhlbi.nih.gov/guidelines/asthma/asthsumm.pdf