Active stand test
Both figures show heart rate (upper part - in red) and blood pressure (blue). The normal response (left panel) is a brief fall in blood pressure compensated by a transient increase in heart rate.
In POTS (right panel), heart rate remains at a high level throughout standing accompanied by strong oscillations in both heart rate and blood pressure. POTS is defined as an increase in heart rate of more than 30 beats per minute from supine to standing (40 for those under the age of 18 years). POTS is also characterised by the strong oscillations in heart rate and blood pressure.
Deep Breathing and Valsalva Maneuvre
The left panel shows heart rate (red) in response to deep breathing at a slow pace respiration. During inspiration heart rate increases and falls during expiration in response to reflex acitivty in the autonomic nervous system.
The right panel shows heart rate (red) and blood pressure in response to expiration against a resistance (begining at the first arrow). Lung pressure is elevated causing resistance to the blood returning to the heart. Thsi leads to a fall in blood pressure compensated by increases in heat rate and contraction of peripheral vessels