Hyperventilation can be defined as breathing too heavily or too fast. Some patients with POTS hyperventilate when they stand. When this happens, patients might feel as if they cannot catch their breath or cannot relax their breathing. Panic-like symptoms also might develop.
This post highlights recent research showing how the heart and blood vessels function differently when patients with POTS hyperventilate during tilt-table testing compared to patients with panic attacks who hyperventilate, and healthy individuals during voluntary hyperventilation.1 Please see our previous post (“POTS 101”) for a discussion about tilt-table testing.
Although an increase in heart rate with standing (postural tachycardia) is a diagnostic feature of POTS, hyperventilation can also cause the heart rate to increase. Try it. Sit upright, feel the pulse in your wrist, and breath rapidly and deeply until you feel lightheaded. Your heart rate should have increased.
Since panic attacks can cause hyperventilation, and the hyperventilation can cause an increased heart rate, how do we know that POTS symptoms aren’t just a form of panic? Dr. Julian Stewart and colleagues¹ sought to answer the question: What is different between patients with POTS and hyperventilation and patients with panic attacks and hyperventilation?
The researchers looked at differences in breathing, heart rate, heart pumping, and blood vessel function between patients with POTS, patients with panic attacks, and healthy individuals with voluntary hyperventilation. All of the research was done during tilt-table testing. They found that individuals in each group had an increase in heart rate. This was expected because everyone in the study hyperventilated. However, breathing patterns, heart pumping, and blood pressure changes were different between groups. How these measures differed is complex. POTS patients hyperventilated by taking deeper breaths without increasing the speed of breathing, had decreased blood pumping from their hearts (referred to as low cardiac output), and had increased blood pressure and blood vessel tightening (referred to as high vascular resistance). Patients with panic attacks had the opposite. The focus of this posting is not to introduce or explain these complex terms, but to highlight the research findings: panic attacks are not the cause of hyperventilation with POTS.
This does not mean that patients with POTS cannot also have panic attacks. In fact, we know that hyperventilation alone can trigger panic attacks in some individuals. Regardless of the POTS diagnosis, if you have symptoms of anxiety, panic, or depression, it is important that you discuss these feelings with your healthcare provider.
¹ Stewart JM, Pianosi P, Shaban MA, Terilli C, Svistunova M, Visintainer P, Medow MS. Hemodynamic characteristics of postural hyperventilation: POTS with hyperventilation versus panic versus voluntary hyperventilation. J Appl Physiol. 2018;125:1396-1403.