Bronchial asthma is a narrowing of the airways most commonly due to an immune-mediated hypersensitivity. As a result of swelling of the walls of the bronchi and bronchioles, excess mucus production and most importantly the contraction of the wall muscles, the bronchoconstriction leads to a reduced air inflow. This contributes to the typical presentation of breathlessness with or without wheezing. Based on the frequency and intensity of symptoms, asthma may be classified as :
- mild persistent
- moderate persistent
- severe persistent
Signs and Symptoms of Asthma
Despite the often severe nature of acute asthmatic attacks, many asthmatics may have little or no symptoms for prolonged periods of time. This contradicts the typical picture that many have of the wheezing asthmatic clutching at a bronchodilator pump as sometimes portrayed in the media.
Very mild bronchoconstriction may go by unnoticed or patients may complain of a “heavy chest” or “chest tightness” without any prominent difficulty in breathing and the absence of abnormal breathing sounds like wheezing. These sensations may precede the rapid onset of an acute attack. Typically, asthmatic patients are practically asymptomatic between attacks. This often creates a false sense of security and leads some patients to discontinue prophylactic (preventative) medication, especially well controlled cases.
Asthma typically presents with the following signs and symptoms :
- Dyspnea – shortness of breath, breathlessness, difficulty breathing
- Audible wheeze – usually expiratory (when exhaling)
- Coughing – dry but can be productive
These symptoms are usually triggered or exacerbated by :
- exposure to known trigger factors like allergens, airborne irritant, exercise
- at night (nocturnal asthma) particularly around 4AM
- viral respiratory tract infections
In the cough-variant subtype of asthma, patients may only report a persistent cough with no other symptoms present. This can be unrelated to any trigger factors and this can be misleading thereby delaying proper diagnosis.
At times an attack can be preceded by upper respiratory symptoms like a runny nose and sneezing, often viral or allergic in nature. Patients may also report a history of sinusitis, sinus headache and disturbances with the sense of smell or even a loss of smell (asomnia).
The word ‘attack’ may sometimes be misleading as it infers a severe state of sudden onset. Therefore the term episode is preferred as it encompasses the acute exacerbations seen in mild cases.
With mild episodes, patients may report some discomfort, only exhibit breathlessness after physical activity and a wheeze may only be audible at the end of expiration upon auscultation (listening to the breathing sounds with a stethoscope). There is usually a slight increase in the breathing rate, but this may not be tachypnea (abnormally rapid breathing).
Moderately Severe Asthmatic Episodes
In these type of episodes, the signs and symptoms are more prominent and often characteristic of what is thought of as an asthma attack.
There is breathlessness that is pronounced after talking and even light physical activity. Patients may report a discomfort in breathing when lying down. A clearly audible and often loud expiratory wheeze can be heard with rapid breathing (tachypnea : breathing rate > 20 breaths per minute) evident.
Some other signs of respiratory distress may be evident like flaring nostrils and labored breathing requiring the use of accessory respiratory muscles (retraction). Clinical investigation may reveal a rapid heart rate (tachypnea) and pulsus paradoxus (sudden fall in systolic blood pressure during inspiration).
Severe Asthmatic Episodes
The breathlessness in these episodes are so severe that it is present even at rest and inhibits the patient from sitting upright, talking in full sentences or even eating. Patients are usually agitated.
Tachypnea is severe with greater than 30 breaths per minutes. An inspiratory and expiratory wheeze (biphasic) is clearly audible and loud. Signs of respiratory distress mentioned above are much more prominent. Tachycardia is present and pulsus pardoxus is prominent.
This is the most severe presentation of asthma that is prolonged, unresponsive to treatment and associated with respiratory arrest. The overinflated lungs with almost complete airway obstruction may cause signs and symptoms that are opposite to the typical presentation seen in mild, moderate and severe attacks. Wheezing may be absent. Bradycardia (slow heart rate) instead of tachycardia may be seen due to hypoxemia (low blood oxygen levels). Pulsus paradoxus may also be absent. The other symptoms of respiratory distress like sweating become evident. Patients shift from being agitated to confused, drowsy and even listless in the most severe states.