Respiratory Motor Control and Blood Pressure Regulation After Spinal Cord Injury
Condition: Spinal Cord Injury
MeSH terms: Spinal Cord Injuries; Wounds and Injuries
Study type: Interventional

Summary: 
      The proposed study is designed to answer a novel research question: Can resistive respiratory
      muscle training designed to improve respiratory motor control also improve blood pressure
      regulation impaired by spinal cord injury? Resistive breathing exercise, or respiratory
      muscle training, has been applied to rehabilitate breathing after spinal cord injury, but has
      not been evaluated as a method for increasing resting blood pressure and / or improving its
      regulation under stress as is planned in the proposed project. For the first time,
      respiratory muscle training intervention will be used as a tool to investigate the
      physiological relationships between pulmonary and cardiovascular function in individuals with
      Spinal Cord Injury (SCI). Thus, it will foster a new direction from which to address
      neglected issues surrounding the cardiovascular complications of spinal cord injury.
    

Detailed description: 
      Screening:

      To aid in determining eligibility, participants will have a respiratory and cardiovascular
      function tests. The participants will also have an ASIA (American Spinal Injury Association)
      exam to grade the degree and level of their SCI.

      Enrollment:

      Following screening process, consenting and recruiting, the experimental recordings:

        1. Pulmonary Function Test- This test measures lung volumes, airflow and airway pressure
           with standard equipment;

        2. Respiratory Motor Control Assessment- Pulmonary function test is repeated while
           participant is sitting in a special hospital bed and lying on their back while the
           investigators record electrical impulses from their neck, chest, arms, legs, abdomen and
           back muscles. These impulses record how their muscles are contracting. The investigators
           also record how their chest and abdomen are moving by placing elastic belts around their
           chest and abdomen. Blood pressure will be measured using a finger cuff;

        3. Orthostatic stress test- Using the same methods as above, the investigators will measure
           blood pressure, heart rate and chest and abdomen movements while the participant is
           lying down on their back and when the position is suddenly changed to sitting in the
           investigators' cardiac chair or to upright vertical position on a Tilt table. The
           investigators will measure blood samples at several intervals from a small catheter
           inserted into the vein in the arm.

        4. Ultrasound of the heart will be performed before and after the Respiratory Muscle
           Training (RMT) program.

      RMT:

      During the training session, subjects will be seated in their personal wheelchair with an
      approximately 45° head-up tilt with nose clip on. Standard threshold Positive Expiratory
      Pressure Device or standard threshold Inspiratory Muscle Trainer or combination of both will
      be used to breathe through with adjustable resistance ranging of 20 to 41 cm of water.

      All of these devices are in routine clinical use. These devices will be assembled together
      using a T-shaped connector with flanged mouthpiece. The participants will be instructed to
      perform inspiratory and expiratory efforts against a resistive load. During inhalation, the
      subjects will be instructed to sustain the effort until their lungs feel full. During
      exhalation, the subjects will be instructed to sustain their effort until their lungs feel
      empty.

      This study will use two test-subject pre-training assessment sessions to provide its internal
      experimental group control. To match the training period (4 weeks), the pre-training
      assessment sessions will be performed four weeks apart and the measured parameters will be
      used to establish the variance in untrained subjects. The pulmonary function tests include
      the measurement of lung volume, airflow, and static mouth airway pressures using standard
      clinical methods and equipment while the SCI participant is sitting in their personal
      wheelchair. The investigators will also record the surface electromyogram (sEMG) activity
      from the trunk muscles during Maximal Inspiratory Pressure (PImax) and Maximal expiratory
      pressure (PEmax) measurements in supine position (PImax and PEmax tasks). The investigators
      will measure a Sympathetic Skin Response (SSR) by recording limb skin resistance during
      neural stimulations. The investigators will assess beat-to-beat systemic blood pressure,
      heart rate and cardiac output will be recorded during the orthostatic stress test. In
      addition, during the orthostatic stress test, the investigators will collect venous blood
      samples to measure the levels of catecholamines. In addition to the beat-to beat calculated,
      resting cardiac output will be measured by ultrasonic cardiac echography. After these initial
      tests, participants will be assigned to RMT. The participants in experimental group will
      complete the study after 4 weeks of training totaling 20 sessions of 45 minutes per day
      carried out 5 days per week. The testing battery will be repeated immediately after
      completing the training and repeatedly during the follow-up period. Ten matched control
      subjects will undergo the same procedures except training.
    

Intervention name(s): Respiratory Muscle Training
Intervention type(s): Behavioral
Intervention description(s): Standard threshold Positive Expiratory Pressure Device and threshold Inspiratory Muscle Trainer assembled together using a T-shaped connector with flanged mouthpiece will be used. The participants will be instructed to perform inspiratory and expiratory efforts against a resistive load. Training session lasts 45 minutes per day, 5 days per week, for 4 weeks.
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Health Services Research
Keywords: Blood pressure regulation; Respiratory Muscle Training