Why does tachycardia occur w asthma?

Tachycardia, or a rapid heart rate, is often seen in patients with asthma due to several factors:

1. Increased sympathetic nervous system activity: Asthma is characterized by airway inflammation and constriction, leading to difficulty breathing and increased work of breathing. This can trigger the sympathetic nervous system, which controls the body's "fight or flight" response. Activation of the sympathetic nervous system results in increased heart rate and dilation of the airways to improve oxygen delivery to the body.

2. Hypoxia: Severe asthma attacks can lead to hypoxia, a condition where there is a deficiency of oxygen in the body's tissues. Hypoxia stimulates the heart to beat faster in an attempt to compensate for the reduced oxygen levels and deliver more oxygen to the vital organs.

3. Hyperinflation: In severe asthma, the airways become obstructed, causing air trapping in the lungs. This leads to hyperinflation, where the lungs become over-expanded. Hyperinflation can put pressure on the heart, affecting its function, and can also trigger tachycardia as the heart tries to adapt to the increased pressure load.

4. Emotional stress: Asthma can be a stressful condition, and anxiety or panic attacks associated with asthma can further increase heart rate.

5. Medications: Some asthma medications, such as beta-agonists (e.g., salbutamol, terbutaline), can have a side effect of causing tachycardia due to their stimulatory effects on the heart.

It is important to note that while tachycardia is a common response to asthma, managing the underlying asthma condition and addressing any contributing factors can help control the heart rate and improve overall symptoms.