___________________________________________________________ Asthma: Diagnosis and Management
[10; 21]. Guidelines for normal breathing are based on analy- sis of data obtained from large segments of the population. A patient’s information is plotted on a continuum, allowing comparison to average breathing patterns for healthy individu- als of the same sex, age, and size. Two common methods of measuring airflow assess forced expiratory volume (FEV 1 ) and peak expiratory flow (PEF) [9; 10; 21]. Spirometry A spirometer is a simple machine used to determine both the total amount of air that can be forcefully exhaled after maxi- mum inspiration, referred to as forced vital capacity (FVC), and how fully air can be expelled from the lungs, measured by the amount of air forced from the lungs in one second, which is expressed as FEV 1 [9; 21]. The spirometer is generally used in diagnosis to establish airflow obstruction and reversibility. Obstruction may be ascertained if the FEV 1 is less than 80% of the predicted value or if FEV 1 divided by FVC is less than 65%. Normally, the FEV 1 should account for more than 75% of the FVC; anything less than 75% indicates a possible obstruction and 65% or less may indicate a diagnosis of asthma [9; 10; 21]. Peak Flow Meter A peak flow meter measures the speed of exhalation. The high- est speed or best flow is PEF or peak flow. The peak flow meter is less sophisticated than a spirometer, which provides a more thorough assessment of lung function. However, the meter has the advantages of being less expensive, portable, and easy to use. The severity of a patient’s asthma can be determined by careful and consistent monitoring of peak flow and comparison to a patient’s best peak flow and to standard measurements. Studies confirm that short-term peak flow measurements assist healthcare providers in assessing asthma severity [8; 9; 21]. Exhaled Nitric Oxide Studies have shown that measuring exhaled nitric oxide (FeNO) is helpful in evaluating and diagnosing asthma, particu- larly in cases of an uncertain diagnosis of asthma using history, clinical course, clinical findings, and spirometry (including bronchodilator responsiveness testing) or when spirometry cannot be performed [9; 10; 13]. Nitric oxide is a mediator for the inflammation that occurs during an asthma episode; the amount of nitric oxide measured during exhalation will directly correlate with the inflammation in the bronchial tubes. In general, higher concentrations of nitric oxide are a sign of more severe forms of asthma. However, the NAEPP notes that increased FeNO levels can be caused by allergic rhinitis and atopy, which can be present in individuals with and without asthma; taking these factors into consideration is important for accurate interpretation of FeNO test results [9; 10]. Monitoring the concentration of nitric oxide in expired breath may allow healthcare providers to confirm the reversible nature of the inflammation and assess the effectiveness and adherence to the prescribed therapeutic treatment. It is not recommended, however, that asthma treatment be routinely tailored based on exhaled nitric oxide levels alone [9; 10; 13].
DIAGNOSIS
PHYSICAL EXAMINATION AND PATIENT HISTORY In some instances, a physical examination and a thorough exploration of a patient’s medical history offer enough infor- mation for an accurate asthma diagnosis. There are several main criteria that should be present for a diagnosis of asthma to be ascertained. It is vital that a history of episodic asthma symptoms, characterized by airflow obstruction, be established. Symptoms that increase the probability of an asthma diagno- sis include episodic wheeze, chest tightness, allergic rhinitis, atopic dermatitis, shortness of breath, and cough. It should also be noted if symptoms worsen at night or in the presence of aeroallergens, irritants, or exercise. A family history of asthma, allergies, sinusitis, or rhinitis is also an indication of potential asthma. According to the National Institutes of Health (NIH), most recurrent episodes of coughing and/or wheezing may be attributed to asthma [9; 10]. Clinical signs of airway narrowing generally consist of wheezing, increased respiratory rate, retractions, nasal flaring, and grunting. Later signs can include tripoding (using accessory muscles to breathe) and altered mental status. In general, asthma symptoms are revealed in different combinations and varying intensities. Due to the fact that asthma symptoms can vary throughout a day, month, or even year, absence of the symptoms during the examination does not exclude a diagnosis. The physical examination should include an assessment of the upper respiratory tract, chest, and skin. One presenting sign is hyperexpansion of the thorax. Patients with severe asthma often develop a barrel-shaped chest due to the forced inhala- tion and exhalation, which may cause chest and rib muscles to overdevelop. In time, the chest walls stretch out of shape, assuming a rounded appearance. As the patient inhales and exhales deeply, the quality of the breath sounds can be assessed. Sounds of wheezing during normal breathing or a prolonged phase of forced exhalation may indicate asthma. Observing increased nasal secretions, mucosal swelling, sinusitis, rhini- tis, nasal polyps, or edema under the eyes are possible signs of allergic asthma. Any of these indications should be noted. Lastly, the skin should be examined for evidence of atopic dermatitis, eczema, or other allergic skin reactions. Red, scaly skin with pruritus may indicate eczema and can signal other forms of allergy and possibly allergy-related asthma. PULMONARY TESTS Most physicians order tests to confirm an asthma diagnosis or to rule out any complications and evaluate the severity of the condition. The objectivity of pulmonary tests allows for a reliable analysis of lung function that patient history and physical examination may not provide; this information may be valuable to the diagnosis process. The most critical tests for evaluating asthma assess pulmonary function, which measures lung performance. Pulmonary tests calculate the amount and rate of air expelled during a single breath, helping to discern whether constricted airways are responsible for blocked airflow
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