Pulsus Paradoxus and Asthma

Pulsus paradoxus is an exaggerated reduction in blood pressure that occurs with inhalation and occurs due to an underlying heart or lung conditions.⁽¹⁾

Systolic blood pressure measures the force the heart exerts on the artery wall with each beat. Diastolic is the measure of the force the heart exerts on the artery walls between the beats. While monitoring blood pressure both systolic and diastolic readings are measured.

Inhalation causes a negative pressure on the lungs. This means the pressure outside the lungs is higher than inside. As the heart is present in the chest, this difference in pressure reduces the amount of blood leaving the left ventricle causing a subtle dip in systolic blood pressure.

In pulsus paradoxus, the negative pressure in the lungs is more pronounced due to breathing difficulties and therefore the drop in blood pressure is more significant.

Pulsus paradoxus occurs as a result of breathing difficulty but is not a feature of asthma.

Asthma causes inflammation of the airways, which causes constriction of the airway. This makes a person harder to breathe, especially during an asthma attack.

The pressure of the lungs decreases during inhalation, which is normal. A person who has breathing difficulties due to severe obstruction experiences an exaggerated response due to the decrease in the air pressure within the lungs, which further leads to a decrease in the systolic blood pressure.

There are conditions other than asthma that can cause pulsus paradoxus. They include the following:

• Cardiac Tamponade: It is a life-threatening condition and occurs due to the build-up of fluid in the space around the heart. This leads to pressure on the heart and prevents it from pumping effectively. It can occur due to infection, heart attack and cancer.
• Cardiomyopathy: This condition leads to stretching, thickening, or stiffening of the heart muscles making it difficult for the heart to pump blood around the body effectively.
• Heart Attack: It occurs due to sudden blockage in the blood supply to the heart especially if the blockage affects the left ventricle.
• Collapsed Lungs: It is a life-threatening condition in which the air escaping the lungs enters the space between the heart and the lungs. The air build-up puts pressure on the lungs preventing its full expansion during inhalation. This condition can occur after injury to the lungs.
• Pulmonary Embolism: This condition occurs after the blockage of the pulmonary artery in the lungs. It mostly occurs when the blood clot from other parts of the body travels to the lungs.

To diagnose pulsus paradoxus, accurate blood pressure management is necessary when a person breathes in. Certain steps are adopted by the doctor or the nurse for accurate blood pressure measurement. These include:

• The reading is first taken when the person is relaxing and not doing any physical activity.
• The person is asked to sit on a chair with the back supported.
• The person’s legs should not be crossed.
• He is asked to stay quiet during the reading as speaking can elevate blood pressure.
• He is asked to relax as anxiety and stress can raise blood pressure and lead to inaccurate readings.
• The reading should be taken before the person breathes in.
• The automatic cuff cannot diagnose the blood pressure accurately and hence the pulsus paradoxus.

There are numerous conditions that can lead to pulsus paradoxus. Therefore a doctor needs to take a complete medical history and order additional tests for heart and lung function.

Pulsus paradoxus is not a disease. It is a symptom of many condition. Therefore rather than treating pulsus paradoxus, the doctor looks at it as a symptom of asthma, how severe is the condition, and how it is reacting to the treatments.

Additionally asthma treatments are recommended for a person who has asthma with pulsus paradoxus. These treatments include:⁽²⁾

• Controlling the environmental factors such as removing allergens, treating underlying allergies, and wearing masks during allergy season.
• Lifestyle changes include losing weight, exercising, and managing stress and anxiety.
• Emergency medications need to be taken to stop an asthma attack.
• Long-acting asthma medications such as inhaled corticosteroids may reduce the severity of asthma symptoms and frequency of attacks.

Pulsus paradoxus is a symptom of heart and lung condition and not a condition itself. It can be cured by treating the cause.