What is the best method for objective assessment of the severity of an asthma attack?

From the Guidelines

The best method for objective assessment of asthma attack severity is peak expiratory flow (PEF) measurement using a peak flow meter. This simple, portable device measures how quickly a person can exhale, providing an objective numerical value that can be compared to the patient's personal best or predicted values based on age, height, and gender. During an asthma attack, a PEF reading below 60% of personal best indicates a severe attack requiring immediate medical attention, while readings between 60-80% suggest a moderate attack. For accurate assessment, the patient should stand upright, take a deep breath, form a tight seal around the mouthpiece, and exhale as forcefully as possible, repeating three times and recording the highest value.

Key Points to Consider

• Other objective measures include oxygen saturation via pulse oximetry (values below 92% indicate severity) 1, spirometry (FEV1 measurement) in clinical settings, and assessment of clinical signs such as respiratory rate, heart rate, ability to speak in full sentences, and use of accessory muscles.
• PEF measurement is particularly valuable because it provides quantifiable data that helps track response to treatment and guides clinical decision-making while being accessible for home monitoring 1.
• The severity of asthma exacerbations can be categorized as mild, moderate, severe, or life-threatening based on symptoms, signs, and functional lung assessment, with the primary determinant being percent predicted FEV1 or PEF 1.
• The use of PEF or FEV1 measurements enables both the patient and the attending medical practitioner to assess more accurately the severity of the asthma attack, and failure to recognize a severe attack has consistently been identified as contributing to death from asthma 1.

From the FDA Drug Label

The use of albuterol sulfate inhalation solution can be continued as medically indicated to control recurring bouts of bronchospasm During this time most patients gain optimum benefit from regular use of the inhalation solution. If a previously effective dosage regimen fails to provide the usual relief, medical advice should be sought immediately, as this is often a sign of seriously worsening asthma that would require reassessment of therapy.

The best method for objective assessment of the severity of an asthma attack is measurement of peak expiratory flow. This is because peak expiratory flow (PEF) is a direct measure of lung function and can be used to assess the severity of asthma symptoms.

• Pulse oximetry measures oxygen saturation, which can be affected by asthma, but it is not a direct measure of lung function.
• Pulmonary function tests are more comprehensive and can provide more detailed information about lung function, but they may not be readily available in all settings.
• Arterial blood gases can provide information about oxygenation and ventilation, but they are more invasive and may not be necessary for routine assessment of asthma severity.
• Chest radiograph is not typically used to assess the severity of an asthma attack, as it is more useful for diagnosing other conditions such as pneumonia. 2 2

From the Research

Objective Assessment of Asthma Attack Severity

The best method for objective assessment of the severity of an asthma attack can be determined through various lung function measurements.

• Peak Expiratory Flow (PEF) Measurement: PEF is a commonly used method to assess asthma severity, as it measures the fastest rate at which a person can exhale air after a maximum inhalation 3, 4, 5, 6, 7. However, the accuracy of PEF measurements can be affected by various factors, such as the patient's ability to report their personal best PEF 3.
• Pulmonary Function Test: Pulmonary function tests, such as forced expiratory volume in one second (FEV1), can also be used to assess asthma severity 4. However, studies have shown that FEV1 and PEF measurements may not be equivalent, and the use of one or the other may result in different classifications of asthma severity 4.
• Other Methods: Other methods, such as pulse oximetry, arterial blood gases, and chest radiograph, may also be used to assess the severity of an asthma attack, but they are not as directly related to lung function as PEF and pulmonary function tests.

Comparison of Methods

A study comparing the use of PEF and FEV1 measurements found that there was considerable variability between the two measurements, and that the use of one or the other may result in different classifications of asthma severity 4. Another study found that PEF measurements were decreased in asthmatic patients compared to healthy controls, and that there was a significant relation between decline in lung function and asthma severity 6.

Clinical Guidelines

Clinical guidelines recommend the use of PEF measurements, in addition to symptoms and medication requirements, to assess asthma severity 7. The guidelines also recommend classifying asthma severity based on history and lung function measurement, with patients having PEF <60% or continuous symptoms classified as severe persistent, and those with PEF >80% and symptoms less than once per week classified as intermittent 7.