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

Risk Factors (triggers)

Airflow Limitation

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

Asthma Diagnosis 

Symptoms



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

Asthma Diagnosis Physical Exam 

Coughing, wheezing



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

OR

 Parent with asthma  Physician diagnosis of

atopic dermatitis  Evidence of sensitization

to aeroallergens

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  FEV1 (Forced Expiratory Volume in 1 Second) –

this is the volume of air expired in the first second during maximal expiratory effort. The FEV1 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.  FEV1/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 FEV1 response of >12% post-bronchodilator is suggestive of asthma

BUT, 

Spirometry is difficult in children 7 years of age

Alternative assessment: 

PEF variability

Asthma Diagnosis Wheezing • tightness • noisy breathing Cough

Dyspnea (Breathlessness)

especially if:

• after exertion • breathing cold air • at night • after colds • paroxysmal

especially if:

?

• intermittent or variable • after exertion • at night

Asthma Diagnosis Wheezing • tightness • noisy breathing Cough

Dyspnea (Breathlessness)

especially if:

• after exertion • breathing cold air • at night • after colds • paroxysmal

especially if:

?

• intermittent or variable • after exertion • at night

Asthma Diagnosis Wheezing • tightness • noisy breathing Cough

Dyspnea (Breathlessness)

especially if:

• after exertion • breathing cold air • at night • after colds • paroxysmal

especially if:

?

• intermittent or variable • after exertion • at night

Asthma Diagnosis Wheezing • tightness • noisy breathing Cough

Dyspnea (Breathlessness)

especially if:

• after exertion • breathing cold air • at night • after colds • paroxysmal

especially if:

?

• intermittent or variable • after exertion • at night

Asthma Diagnosis Wheezing • tightness • noisy breathing Cough

especially if:

• after exertion • breathing cold air • at night • after colds • paroxysmal

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