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Environmental Triggers of Asthma
Clinical Assessment

Course: WB 1102
CE Original Date: October 17, 2007
CE Renewal Date: October 17, 2010
CE Expiration Date: October 16, 2012
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Learning Objectives

Upon completion of this section, you will be able to

  • identify the key signs and symptoms of asthma,
  • describe questions regarding environmental asthma triggers that should be included in the standard medical history,
  • describe pulmonary function test criteria for diagnosing asthma,
  • identify the role of allergy testing in managing asthma, and
  • describe questions regarding occupational exposures that should be included in the standard medical history.

Key Elements of Diagnosis

To establish a diagnosis of asthma, the clinician should confirm the following key points:

  • episodic symptoms of airflow obstruction are present,
  • airflow obstruction is at least partially reversible, and
  • alternative diagnoses are excluded.

Recommended mechanisms to establish the diagnosis include

  • detailed medical history,
  • physical exam focusing on the upper respiratory tract, chest, and skin, and
  • spirometry to demonstrate reversibility.

Additional studies may be considered to:

  • evaluate alternative diagnoses,
  • identify precipitating factors,
  • assess severity, and
  • investigate potential complications.

Some cases may require referral to a specialist in asthma care for consultation or treatment (NHLBI 1997; NHLBI 2003).

Medical History

The focus of the medical history should be on the presence of any of the following (NHLBI 1997; NHLBI 2003):

  • cough (particularly worse at night),
  • family history of asthma or allergies,
  • recurrent chest tightness,
  • recurrent difficulty in breathing, and
  • recurrent wheeze

Note whether symptoms occur or worsen in the presence of (NHLBI 1997; NHLBI 2003):

  • airborne chemicals or dusts,
  • animals with fur or feathers,
  • changes in weather,
  • dust mites (i.e., in mattresses, pillows, upholstered furniture, carpets, bed linens, stuffed animals; note laundering/cleaning practices involving these items),
  • exercise,
  • menses,
  • mold,
  • pollen,
  • smoke (tobacco, wood),
  • strong emotional expression (laughing or crying hard), or
  • viral infection

A sample environmental trigger exposure history is included in Appendix 1. This tool was developed by The National Environmental Education and Training Foundation for children and adolescents with asthma (NEETF 2005).

A resource for general exposure history taking is “Case Studies in Environmental Medicine: Taking an Exposure History” (http://www.atsdr.cdc.gov/csem/csem.asp?csem=17&po=0).

Physical Exam

The physical examination should focus on the upper respiratory tract, chest, and skin (NHLBI 1997; NHLBI 2003).

Physical findings that increase the probability of asthma include

  • appearance of hunched shoulders,
  • atopic dermatitis/eczema or any other manifestation of an allergic skin condition,
  • chest deformity,
  • hyperexpansion of the thorax (especially in children),
  • increased nasal secretion, mucosal swelling, and nasal polyps,
  • prolonged phase of forced exhalation (typical of airflow obstruction),
  • sounds of wheezing during normal breathing, and
  • use of accessory muscles of respiration (neck, back, and chest).

Note—Wheezing during forced exhalation is not always a reliable indicator of airflow limitation. In mild intermittent asthma, or between exacerbations, wheezing may be absent.

Pulmonary Function Testing

Spirometry typically measures the maximal volume of air forcibly exhaled from the point of maximal inhalation (forced vital capacity, FVC) and the volume of air exhaled during the first second of the FVC (forced expiratory volume in 1 second, FEV1). Airflow obstruction is indicated by reduced FEV1 and FEV1/FVC values relative to reference or predicted values.

Spirometry measurements (FEV1, FVC, and FEV1/FVC) before and after the patient inhales a short-acting bronchodilator should be taken to help confirm a diagnosis of asthma.This also helps determine whether airflow is obstructed and whether it is reversible over the short term. Spirometry is generally valuable in children over 4 years of age; however, some children cannot conduct the maneuver adequately until after 7 years of age (NHLBI 1997; NHLBI 2003).

Significant reversibility is indicated by an increase of 12% or more and 200 mL or more in FEV1 after inhaling a short-acting bronchodilator. A 2 to 3-week trial of oral corticosteroid therapy may be required to demonstrate reversibility. The spirometry measures that establish reversibility may not indicate the patient's best lung function. Abnormalities of lung function are categorized as restrictive and obstructive defects.

  • A reduced ratio of FEV1/FVC (i.e., < 65%*) indicates obstruction to the flow of air from the lungs.
  • A reduced FVC with a normal FEV1/FVC ratio suggests a restrictive pattern.

*<70% is often taken as the normal cut-off. The normal cut-off is age dependent (falling over time).

The severity of abnormal spirometric measurements is evaluated by comparison of the patient's results with reference values that are based on:

  • age,
  • height,
  • race, and
  • sex (NHLBI 1997; NHLBI 2003).

Allergy Testing

For patients with persistent asthma who take daily medications, the clinician should identify allergen exposures and consider using skin testing or in vitro testing to assess sensitivity to perennial indoor allergens. Determination of sensitivity to a perennial indoor allergen is often not possible from a patient medical history alone. Susceptible individuals tend to be atopic and will demonstrate an immediate wheal-and-flare skin reaction when prick-tested against various common allergens. Skin testing and in vitro laboratory results (e.g., radioallergosorbent test [RAST testing]), which determine antigen-specific IgE concentration in serum, must be correctly interpreted and correlated with the patient's history and exam (see Table 3). The demonstration of IgE antibodies to an allergen demonstrates prior exposure, but does not always prove that the patient's allergic symptoms are related to that specific allergen (NHLBI 1997; NHLBI 2003).

The recommendation to do skin or in vitro tests for patients with persistent asthma exposed to perennial indoor allergens will result in a limited number of allergy tests for about half of all asthma patients. This is based on the prevalence of persistent asthma and the level of exposure to indoor allergens. Skin or in vitro tests for patients exposed to perennial allergens are essential to justify the expense and effort involved in implementing environmental controls. In addition, patients are less likely to maintain environmental controls (e.g., with regard to pets) without proof of their sensitivity to allergens (NHLBI 1997; NHBLI 2003).

Table 3. Comparison of In Vivo vs. In Vitro Allergy Testing (NHLBI 1997; NHLBI 2003)
Advantages of Skin Testing Advantages of RAST and Other In Vitro Test
  • Less expensive than in vitro tests
  • Results are available within 1 hour
  • More sensitive than in vitro tests
  • Results are visible to the patient (This may encourage compliance with environmental control measures.)
  • Does not require knowledge of skin testing technique
  • Does not require availability of allergen extracts
  • No risk of systemic reactions
  • Can be performed on patients who are taking medications that suppress the immediate skin test (antihistamines, antidepressants)
  • Can be done for patients with extensive eczema

Diagnosis and Evaluation of Occupational Asthma

Occupational asthma is the most prevalent form of work-related lung disease in industrialized nations. (ATS 1995). Increasing numbers of new chemicals are being produced and new manufacturing processes are being introduced. The variety of environments in which individuals may become exposed to respiratory sensitizers and irritants makes diagnosing and treating this illness even more challenging. Clinicians must first document the presence of asthma, and then establish a relationship between asthma and the workplace.

The adult patient's occupational history is the key diagnostic tool. In addition, lung function assessments that include spirometry and bronchial responsiveness are now often coupled with immunological assessment and an evaluation of inflammation in the investigation of occupational asthma. Evaluations may include serial peak expiratory flow rate (PEFR) measurements and nonspecific hypersensitivity challenges with histamine or methacholine. Serial PEFR monitoring while at work and away from work may be important in documenting whether asthma is work-related in selected people, work-environment permitting (Malo and Chan-Yeung 2001). Information about workplace exposures to irritants and sensitizers may be useful. Specific challenge testing at tertiary referral centers providing specialized laboratories can also be helpful (Rabatin and Cowl 2001) but is rarely necessary and may create unnecessary risk.

Since asthma is an inflammatory disease, a measure of the degree of inflammation would be helpful in quantitating severity and titrating of anti-inflammatory therapy. There is evidence that monitoring eosinophils and neutrophils in induced sputum can help in the management of asthma (Lemiere 2004). A noninvasive method for measuring pulmonary inflammation would be helpful to assist the physician in initial treatment and assist in titration of anti-inflammatory therapy for asthma. Exhaled nitric oxide (NO) assays are being evaluated but are not yet validated for routine use (DeNicola et al. 2000; Bates and Silkoff 2003).

Key Points

  • The medical history should include a set of standard questions addressing factors that worsen the patient's asthma symptoms.
  • Asthma is an episodic disease. Physical findings may vary dramatically with time.
  • Spirometry measurements before and after a short-acting bronchodilator are extremely helpful in the diagnosis of asthma.
  • For those patients with persistent asthma who take medications daily, the clinician should consider using skin testing or in vitro testing to assess sensitivity to perennial indoor allergens.
  • Occupational asthma is the most prevalent form of work-related lung disease in industrialized nations.
   

Progress Check

7. Medical history questions about environmental asthma triggers should include

A. Tobacco smoke.
B. Pets.
C. Bedding and laundering practices.
D. All of the above.

Answer:

To review relevant content, see Medical History in this section.

8. It is possible to make the diagnosis of asthma without detectable wheezing.

A. True.
B. False.

Answer:

To review relevant content, see Pulmonary Function Tests in this section.

9. The key diagnostic tool in occupational asthma is

A. Complete blood count.
B. Chest X-ray.
C. The occupational exposure history.
D. Arterial blood gases.

Answer:

To review relevant content, see Diagnosis and Evaluation of Occupational Asthma in this section.

10. An individual who increases his/her FEV1 by more that 12% after inhaling a short-acting bronchodilator probably has asthma

A. True.
B. False.

Answer:

To review relevant content, see Physical Exam in this section.

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