Breathing for Two: Inspiratory Muscle Strength Training for Supporting Healthy Blood Pressure in Pregnancy

Overview

This is an interventional study that will test whether a breathing exercise called Inspiratory Muscle Strength Training (IMST) can safely and effectively lower blood pressure during late pregnancy. The goal is to see if a home-based breathing training can help prevent or reduce high blood pressure disorders in pregnancy. The main objectives are to make sure the training is safe and tolerable for pregnant women and to examine blood pressure and blood vessel health. Participants in their third trimester will be randomly assigned to either do moderate resistance IMST or a minimal resistance sham IMST, for 5 to 8 minutes a day over six weeks.

Interventions

• Other Exercise at 15% PI max
  Minimal resistance training, similar to yoga, for 5 to 8 minutes a day over six weeks.
• Other Exercise at 50% PI max
  Moderate resistance training, similar to strength training for 5 to 8 minutes a day over six weeks.

Primary outcome measures

• Incidence of Maternal and Fetal Safety Events During Inspiratory Muscle Strength Training (IMST) [Time frame: 6 weeks]
• Adherence to IMST Training and Home Blood Pressure (BP) Monitoring [Time frame: 6 weeks]
• Change from Baseline in Systolic Blood Pressure [Time frame: 6 weeks]
• Change from Baseline in Endothelial Function as Assessed by Post-Occlusive Reactive Hyperemia (PORH) [Time frame: 6 weeks]
• Change from Baseline in Urinary Nitrite/Nitrate Concentration [Time frame: Change in urinary nitrite/nitrate concentration (µM), measured weekly via Griess colorimetric assay (Cayman Nitrite Colorimetric Assay), as an indirect marker of nitric oxide bioavailability.]

Secondary outcome measures (3)

• Change from Baseline in Perceived Sleep Quality [Time frame: 6 weeks]
• Change from Baseline in Dyspnea Severity [Time frame: 6 weeks]
• Change from Baseline in Perceived Stress [Time frame: 6 weeks]

Eligibility criteria

Inclusion criteria

• Female sex
• Pregnant (32 to 34 weeks of gestation, confirmed by ultrasound, at the time of first training session, eligible patients may consent/enrolled earlier in pregnancy)
• Singleton pregnancy
• Age 18 to 55
• Able to read English and provide consent
• Possess smartphone for syncing the AiroFit and Omron devices using Bluetooth and completing online surveys
• Smartphone updated to iOS 12+ or Android 11+
• No contraindication for moderate exercise at time of enrollment
• Not planning delivery for at least one month at time of enrollment (< 38 weeks of gestation)
• Willing to adhere to AiroFit device use throughout study period
• Must already be scheduled, or in the process of scheduling, for weekly NST appointments by 32 to 34 weeks gestational age (per provider order / due to obstetric indication)

Lower-Risk Pregnancy Cohort Inclusion Criteria:

• No history or evidence of hypertensive disorders of pregnancy
• May be undergoing antenatal testing for:
• Conception via in vitro fertilization, BMI ≥ 35, an advanced maternal age (age >/=35), or other condition not listed in exclusion criteria or 'higher risk for HDP group' but is recommended for antenatal testing.

Higher-Risk Pregnancy Cohort Inclusion Criteria:

• Conditions associated with higher risk of developing HDP, including:
• Gestational diabetes mellitus, chronic hypertension, gestational hypertension, or a history of preeclampsia in a previous pregnancy

Exclusion criteria

• Younger than 18 or older than 55 years of age
• Multiple gestation (twin or higher-order pregnancy)
• Fetal chromosomal abnormalities or major anatomical anomalies
• Planning to deliver earlier than 38 weeks or within 4 weeks of study enrollment
• Any contraindication for moderate exercise (e.g., cardiomyopathy, congenital cardiac conditions)
• Deep vein thrombosis
• Complications in current pregnancy including intrauterine growth restriction (IUGR), oligohydramnios, preeclampsia, or severe-range blood pressures (>/=160/110 or <100/60)
• Active vaginal bleeding, or history of coagulopathy
• Placenta previa or other placental abnormalities (including placental cyst or abruption)
• Signs of labor
• Current substance use disorder
• History of neurological, respiratory, head/neck, or thoracic surgeries, or conditions such as collapsed lung or perforated eardrum
• Individuals with any of the following:
• Chronic obstructive pulmonary disorder (COPD)
• Severe asthma
• Severe ischemic heart disease
• Left-sided heart failure
• Chronic laryngitis, chronic bronchitis, emphysema, pneumonia
• Latent or active tuberculosis
• Chronic cough
• Neurological problems (e.g. seizure disorder)
• Severe scoliosis with no history of surgical correction or management.
• Organ transplant
• HIV or other immunocompromising conditions
• Autoimmune disease with possible vascular complications (e.g. Lupus)
• Significant respiratory compromise (e.g., severe dyspnea, O₂ saturation <95%, uncontrolled asthma, history of pneumothorax)

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: Yes

Study design

Allocation

Randomized

Model

Parallel assignment

Masking

Quadruple blind

Primary purpose

Prevention

Study locations

United States · 1 center

• Banner University Medical Center — Tucson

Identifiers

NCT: NCT07687745 · STUDY00007216

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗