Hypercapnia and Orthostatic Tolerance in Postural Orthostatic Tachycardia Syndrome
试验速览
- 阶段
- 不适用
- 状态
- 招募中
- 入组人数
- 26
- 试验地点
- 2
- 主要终点
- Heart Rate (HR) variation
研究概览
简要总结
The mechanism behind postural orthostatic tachycardia syndrome (POTS) involves many causes including a sympathetic nervous system problem. Blood gases, like carbon dioxide (CO2), have an important effect on sympathetic activation.
The purpose of this research study is to determine if higher CO2 levels have any effect in lowering heart rate and reducing POTS symptoms when upright/standing. The investigators are also searching for the ideal CO2 concentration to achieve the most effective response
详细描述
The effects of hypercapnia on cerebral blood flow velocity and arterial blood pressure in healthy subjects lead to an increase in orthostatic tolerance, peak HR and time to peak HR compared with normocapnic orthostatism. The CO2 effects on heart rate and orthostatic tolerance were observed in a small group of POTS patients with orthostatic hypocapnia, after supplying CO2 to correct hypocapnia. It is unclear, however, whether this intervention will also work for the broader POTS population. This might constitute an attractive option of therapy for POTS patients.
The investigator's hypothesis is that increasing end-tidal CO2 (ETCO2) will reduce orthostatic tachycardia and orthostatic symptoms in patients with POTS. The secondary hypothesis is that blood pressure will be better maintained during increased ETCO2 via improved cardiac output.
INTERVENTION The RespirAct™ system (Thornhill Research Inc., Toronto, Canada) is a computer-controlled gas blender providing CO2, O2 and nitrogen for a subject to inhale while breathing for the purpose of controlling the concentrations of the respective blood gases. The RespirAct™ records inspired and exhaled gas concentrations, which can be recalled, analyzed and graphed. Data is collected breath-by-breath including end-tidal O2 and CO2, the length of inspiration and expiration for the breath, the respiration rate and the tidal volume per breath. The system has been Health Canada approved and utilized in several publications in healthy individuals and clinical populations. Subjects will be fitted with a face mask which will be connected to a tube supplied with gas from RespirAct™ system
Primary Analysis The primary analysis will compare the magnitude of ΔHR from supine to HUTT during hypercapnia compared to HUTT with no intervention (HUTT 3 and 4 vs 1). The comparison will use a paired t-test (or a Wilcoxon Signed-Rank test if the data are non-normally distributed).
Secondary Analysis The secondary analysis will compare the VOSS Symptom Rating at the end of each 8 min HUTT, comparing each HUTT run.
研究设计
- 研究类型
- Interventional
- 分配方式
- Na
- 干预模型
- Single Group
- 主要目的
- Other
- 盲法
- None
盲法说明
All participants will be fitted with a face mask connected to a tube supplied with gas from the RespirAct™ system. The participants will not be informed about the concentration of gases during the tilt tests. After the study completion they will be informed about the order of interventions.
入排标准
- 年龄范围
- 18 Years 至 60 Years（Adult）
- 性别
- All
- 接受健康志愿者
- 否
入选标准
- •Physician diagnosis of Postural Tachycardia Syndrome (POTS)
- •Age 18-60 years
- •Male and Female
- •Non - smokers.
- •Able and willing to provide informed consent.
- •Ability to travel to Libin Cardiovascular Institute of Alberta Autonomic Testing Lab at the University of Calgary, Calgary, AB.
排除标准
- •Overt cause for postural tachycardia, i.e., acute dehydration
- •Participants with somatization or severe anxiety symptoms will be excluded
- •Inability to tolerate mask for the duration of the study
- •Subjects who require portable oxygen at rest or with exercise
- •Subjects with chronic heart failure or severe pulmonary disease who are unable to climb one flight of stairs due to shortness of breath.
- •Other factors which in the investigator's opinion would prevent the participant from completing the protocol, including poor compliance during previous studies.
结局指标
主要结局
Heart Rate (HR) variation
时间窗: difference between HR from supine to peak HR during tilt test for each intervention (mean value HR between the 8th and 9th minute of supine; peak parameters, during HUTT, mean value during the first min and between the 3rd and 8th min)
Magnitude of ΔHR
次要结局
- VOSS symptom score(VOSS will be accessed at the 8th minute of each HUTT, comparing the intensity of symptoms in each intervention)
- Cerebral blood flow velocity (CBFv) variation(difference between CBFv from supine to peak during tilt test for each intervention (mean value CBFv between the 8th and 9th min of supine; peak parameters, during HUTT, mean value CBFv during the first min and between the 3rd and 8th min))