How to Diagnose Acute Asthma in Adults?

Bronchial asthma is a chronic (long-term) inflammatory condition of the lungs. It occurs basically in the airways. Usually, bronchial asthma can be controlled with medications and lifestyle modifications. However, some people may develop acute attacks (exacerbation) of asthma.

Features of acute asthma

It is important to identify and manage acute asthma. There are some features, which help identify or diagnose acute asthma attacks.

Severe shortness of breath (breathlessness), which includes too breathless to complete sentences in one breath.
Increased heart rate (tachycardia) or pulse rate
Increased respiratory rate (tachypnoea)
Poor respiratory effort without wheezing
Collapsed patient
Bluish discolouration (cyanosis) of lips, tongue, or fingers, which is due to low oxygen in the blood.

However, these are not specific features of an acute asthma attack. Their absence doesn’t rule out a severe attack. Why is it important to identify acute asthma attacks? People with acute severe asthma and one or more psychosocial risk factors have a higher risk of death.

Investigations

Acute asthma attacks can be diagnosed with clinical features and some tests. Investigations include Peak Expiratory Flow (PEF), Forced Expiratory Volume in one second (FEV1), chest X-ray, Arterial blood gases (ABG), and pulse oximetry.

PEF is also known as PEFR (peak expiratory flow rate). It measures a person’s maximum speed of expiration with a small equipment called peak flow meter. Therefore, it helps assess the degree of the obstruction of airways. FEV1 indicates the volume of air, which can forcibly be exhaled within one second. PEF is stated as a percentage of the patient’s earlier best value. It is very useful clinically. If there is no previous PEF values, PEF can be mentioned as a percentage of the predicted value.

Pulse oximetry measures oxygen saturation (SpO2) in the blood as a percentage. It helps identify the adequacy of oxygen supply to the patient. Oxygen flow should be adjusted to keep up SpO2 between 94 % and 98 %. If the patient is with a SpO2 value of less than 92 %, or other symptoms or signs of life-threatening bronchial asthma, he or she needs an ABG test. An ABG test measures the amounts of some gases (oxygen and carbon dioxide) and electrolytes in the arterial blood.

Chest X-ray is indicated, if the patient has at least one of the following.

Suspected pneumonia
Suspected pneumothorax
Suspected pneumomediastinum
Life-threatening bronchial asthma
A requirement of mechanical (artificial) ventilation
Failure to respond to treatments sufficiently

Types of acute asthma attacks

Acute bronchial asthma attacks can be divided into four groups based on the severity. They are:

Moderate exacerbation of bronchial asthma
Acute severe bronchial asthma
Life-threatening bronchial asthma
Near fatal bronchial asthma

Moderate exacerbation of bronchial asthma

Moderate exacerbation can be diagnosed with the following features.

No features of acute severe bronchial asthma
Increasing symptoms
PEF is more than 50-75 % of the earlier best or predicted value.

Acute severe bronchial asthma

If the patient has one of the following features, acute severe bronchial asthma is likely.

Respiratory rate 25 cycles per minute or above and heart rate 110 beats per minute or above
Failure to complete sentences in one breath
PEF is 33-50 % of the earlier best or predicted value.

Life-threatening bronchial asthma

If the patient with acute severe asthma has at least one of the following features, life-threatening bronchial asthma can be diagnosed.

SpO2 (oxygen saturation in the blood) is less than 92 %.
PEF is less than 33 % of the earlier best or predicted value.
PaO2 (arterial partial pressure of oxygen) is less than 60 mmHg (8 kPa).
Normal PaCO2 (arterial partial pressure of carbon dioxide), between 35 mmHg and 45 mmHg (4.6-6 kPa)
Cyanosis
Silent chest
Poor respiratory effort
Physical exhaustion
Altered conscious level
Rhythm abnormalities of the heart (arrhythmia)