Hemodynamic Effects of Aquatic vs. Land Exercise in Patients With Orthostatic Hypotension

Orthostatic hypotension is a highly prevalent deficit in the aging population especially when coupled with stroke, frailty, diabetes, Parkinson's disease or spinal cord injuries. This population has difficulty with the autonomic regulation of blood pressure and experiences elevated risks of falls. The fall risk is greatest when the person transitions from supine or sitting to standing as this is when blood has a tendency to pool in the legs preventing adequate blood circulation to vital organs. This is a safety concern and limiting factor for rehabilitation of patients with orthostatic hypotension in the inpatient rehabilitation setting. There is low-quality evidence that compression garments such as abdominal binders and compression stockings can be helpful to manage orthostatic hypotension and the associated fall risk. However, many people with orthostatic hypotension perceive the treatment approach with compression stockings to be largely unacceptable.

Aquatic immersion may provide better advantages to compression garments because hydrostatic pressure exerts a little over 22 mmHg pressure for every foot of water. Therefore, an individual standing in 4 ft depth water will have roughly 90 mmHg pressure on their feet and about 56 mmHg at their knees. These amounts of pressure are more than those induced by typical compression stockings, which provide 30-40 mm Hg pressure. In addition, immersion at level of xiphoid process or higher is known to translocate blood from the lower to the center of the body and act to increase cerebral blood flow which may be beneficial for preventing orthostatic hypotension symptoms.

No studies have looked at the physiologic response to immersion and aquatic exercise for people with orthostatic hypotension. Since this population is known to have difficulty with autonomic regulation of blood pressure, it is unclear if they will experience a similar hemodynamic response during immersion than the healthy population during or after aquatic therapy due to orthostatic hypotension.

Anecdotal evidence suggests that patients with orthostatic hypotension do not exhibit adverse effects due to orthostatic hypotension when standing in water or participating in aquatic exercise independent of compression garments use. They often have improved standing tolerance in the pool compared with prolonged standing on land. Steps to manage orthostatic hypotension when out of the pool, such as hydration during pool session, placing compressive garments prior to exit of pool and slow transitions out of pool setting has been adequate to prevent symptoms of orthostatic hypotension in the post exercise period in this population.

The primary aim of this study is to look at heart rate and blood pressure response when going from sit to stand during physical therapy sessions on land compared to in the pool for people who have orthostatic hypotension (defined as a drop in systolic blood pressure of at least 15 mmHg or 7 mmHg drop in diastolic blood pressure from sitting to standing). The secondary aim of this study is to evaluate tolerance for physical activity during physical therapy sessions in the pool compared to on land for people with orthostatic hypotension. The third aim of the study is to investigate heart rate and blood pressure response for 3 hours following the physical therapy sessions.

We hypothesize that orthostatic hypotension will be reduced and standing exercise tolerance will be increased when in the pool compared to on land. In addition, we hypothesized that there will not be a significant difference in heart rate or blood pressure response in the 3-hour post exercise period of aquatic vs. land exercise.


Eligibility Criteria:
Inclusion Criteria:

1. Patient at Central Texas Rehabilitation Hospital in Austin, Texas
2. Age 18 years or older
3. Patient presents with orthostatic hypotension defined as transitions from sit to stand using a threshold of drop of at least 15 mmHg for SBP or at least 7 mmHg for DBP.
4. Aquatic therapeutic exercise is included in patients plan of care.
5. Signed informed consent

Exclusion Criteria:

1. Contraindication for aquatic physical therapy including but not limited to open wound that cannot be safely covered with a waterproof dressing, diarrhea, fever or know contagious infection.
2. Unable to safely maintain standing position for 2 min with or without assistance to measure vitals in pool and land.
3. Change in blood pressure medication or medical status between pool and land data collection.