Asthma Diagnosis:Anatomy and Pathophysiology of

Asthma

Karen Meyerson, MSN, RN, FNP-C, AE-CAsthma Network of West Michigan

April 21, 2009Acknowledgements: LeRoy M. Graham, MD, Atlanta, GA

Allan T. Luskin, MD, Madison, WI

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 Underlyingthe Definition of Asthma

INFLAMMATIONINFLAMMATION

Risk FactorsRisk Factors(for development of asthma)(for development of asthma)

AirwayAirwayHyperresponsivenessHyperresponsiveness Airflow LimitationAirflow Limitation

SymptomsSymptomsRisk FactorsRisk Factors

(triggers)(triggers)

Asthma Airways

Before 10 Minutes After Allergen Challenge

Airway Remodeling

AsthmaticAsthmaticNormalNormalJeffery P. Asthma. 1998.

The “Tip” of the Iceberg

Airway inflammation

Airflow obstruction

Bronchial hyperresponsiveness

ASTHMA Symptoms

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 DiagnosisAssessing 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 DiagnosisMedical 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 DiagnosisPhysical 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:

Castro-Rodriguez J et al. Castro-Rodriguez J et al. AJRCCM AJRCCM 2000; 162:1403-1406.2000; 162:1403-1406.

One major criteria 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

OROR

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. Castro-Rodriguez J et al. AJRCCM AJRCCM 2000; 162:1403-1406.2000; 162:1403-1406.

Asthma DiagnosisMeasurements 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 LoopObstruction

Asthma DiagnosisMeasurements of Lung Function

Spirometry: An FEV1 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

?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

Asthma Diagnosis

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