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Intermittent Hypoxia and Inspiratory Threshold Loading to Enhance Inspiratory Muscle Function

Primary Purpose

Intermittent Hypoxia

Status

Completed

Phase

Not Applicable

Locations

United States

Study Type

Interventional

Intervention

Intermittent Hypoxia

Inspiratory Threshold Loading

Sham Intermittent Hypoxia

About this trial

This is an interventional treatment trial for Intermittent Hypoxia focused on measuring Inspiratory threshold loading

Eligibility Criteria

18 Years - 40 Years (Adult)All SexesAccepts Healthy Volunteers

Inclusion Criteria:

Participating in three or fewer musculoskeletal strength training sessions per week at an intensity equivalent to 7-10 on the Modified Borg's scale
Participating in three or fewer cardiovascular endurance training sessions per week at an intensity equivalent to 7-10 on the Modified Borg's scale

Exclusion Criteria:

Diagnosis of cardiovascular disease (Hypertension, arrhythmias, coronary artery disease, congenital and valvar heart diseases)
Diagnosis of neuromuscular disease
Diagnosis of any neurological disease
Presence of concurrent medical illness including infection, fractures
Diagnosis of obstructive sleep apnea
Diagnosis of obstructive/restrictive lung disease
Diagnosis of exercise induced asthma
Forced expiratory volume at one second/forced vital capacity (FVC) <80% and/or FVC<80% of predicted value indicating airway obstruction
Subjects on prednisolone therapy or selective serotonin reuptake inhibitor (SSRI) therapy will be excluded from the study.
Diagnosis of epilepsy or history of seizures and attention deficit disorders
Pregnancy
Diabetes
History of coagulation disorders
History of chronic pain
Body mass index(BMI)> 35kg/m2
Subjects on prescription medicines such as beta blockers and other drugs that are prescribed in any of the exclusionary disorders listed above.
Any other factor that in the investigators' opinions would prevent response to training or create an unsafe condition for the subject.

Sites / Locations

University of Florida

Arms of the Study

Arm 1

Arm 2

Arm 3

Arm 4

Arm Type

Experimental

Sham Comparator

Arm Label

IH + ITL

Intermittent hypoxia (IH)

Sham IH + ITL

Sham IH

Arm Description

Subjects will be exposed to a session of Intermittent hypoxia (IH) (45 minutes, 2 minutes of hypoxia alternating with 1 minute of hyperoxia) followed by 5 sets of Inspiratory threshold loading (ITL) at 80%MIP (10 breaths per set).

Subjects will only be exposed to a session of intermittent hypoxia.

Sham Intermittent Hypoxia + Inspiratory threshold loading (ITL) subjects will be exposed to a single 45-minute session of sham IH (normoxia). This will consist of the subject breathing room air (FiO2=21%) through a 4 way valve connected to the hypoxicator. Exposure to normoxia will be followed by 5 sets of ITL at 80%MIP (10 breaths per set).

Sham intermittent hypoxia subjects will be exposed to a single 45-minute session of sham IH alone.

Outcomes

Primary Outcome Measures

Maximal Inspiratory Pressure will be measured across all groups

Maximal Inspiratory Pressure(MIP) which is a measure of inspiratory muscle strength will be measured as the MIP recorded at the mouth by a pressure manometer. Subjects will be seated upright in a comfortable chair and the nose occluded with clips. After exhaling to residual volume (RV), subjects place their lips around the mouthpiece and inspire as forcefully as possible for at least three seconds. Repeated measurements will be taken, with a 1- to 2-min rest between trials, until three measurements are obtained within 5% variability. Of these three values, the best MIP will be recorded.

Ventilatory responses to inspiratory loading will be measured across all groups

Subjects will be asked to breathe as forcefully as possible against a inspiratory load( 2-4 sets of 5 repetitions) of either 40% of their maximal inspiratory pressure(MIP) or at 41CmH2O (lowest of the two as the maximum resistance offered by the device is 41CmH2O) using a inspiratory muscle training (IMT) device. During this task, a respiratory monitor will be connected to the IMT device. Parameters such as the inspiratory flow, volume and pressure generated by the subjects while breathing against the load will be recorded. Imposed work of breathing (WOBi) will be calculated as a product of the pressure generated and the inspired tidal volume when breathing against a fixed load (40%MIP).

Mouth occlusion pressure (P0.1) will be measured across all groups

To record P0.1, the subjects will breathe through a mouth piece connected to a 2 way respiratory valve in a closed circuit. As the subjects breathe through the circuit, the inspiratory valve will be manually occluded during the expiratory phase and the occlusion will be maintained till the end of next inspiration. Occlusion will be random in order to prevent the subjects from getting conscious about the occlusions. The circuit is connected to the respiratory monitor and the negative pressure recorded in the first 100 milliseconds of the occluded breath will be recorded as the subject's P0.1. 3 such recordings will be obtained and the highest pressure amongst the 3 trials will be considered for analysis.

Secondary Outcome Measures

Heart Rate Variability (HRV) will be measured across all groups

Heart Rate Variability (HRV): HRV will be assessed to determine the autonomic response to intermittent hypoxia. HRV will be measured using a 3 lead ECG and HRV recording kit.

Full Information

NCT ID

NCT03029559

First Posted

January 17, 2017

Last Updated

June 19, 2019

Sponsor

University of Florida

1. Study Identification

Unique Protocol Identification Number

NCT03029559

Brief Title

Intermittent Hypoxia and Inspiratory Threshold Loading to Enhance Inspiratory Muscle Function

Official Title

Intermittent Hypoxia and Inspiratory Threshold Loading as Strategies to Enhance Inspiratory Muscle Function

Study Type

Interventional

2. Study Status

Record Verification Date

June 2019

Overall Recruitment Status

Completed

Study Start Date

February 17, 2017 (Actual)

Primary Completion Date

February 19, 2018 (Actual)

Study Completion Date

February 19, 2018 (Actual)

3. Sponsor/Collaborators

Responsible Party, by Official Title

Sponsor

Name of the Sponsor

University of Florida

4. Oversight

Studies a U.S. FDA-regulated Drug Product

Studies a U.S. FDA-regulated Device Product

Data Monitoring Committee

5. Study Description

Brief Summary

Rehabilitation approaches introduce a stimulus to a motor system, with the goal to enhance motor function to patients. For example, exposure to brief and intermittent episodes of mild hypoxia has shown to strengthen synaptic pathways to respiratory and skeletal muscle motor neurons. In humans with spinal cord injury, exposure to intermittent hypoxia (IH) alone or in combination with rehabilitative strategies has shown enhanced motor function. Another strategy known as inspiratory threshold loading, which involves breathing against pressure threshold loads, results in improved inspiratory muscle strength. Although there is evidence supporting the use of IH alone or in combination with other rehabilitative strategies in improving motor function in humans, the impact of exposure to IH or IH with inspiratory threshold loading on inspiratory muscle function and ventilation in humans is unknown.

Detailed Description

Investigators will test whether exposure to IH alone and in combination with inspiratory threshold loading (ITL) will result in increased inspiratory muscle strength and ventilation. Investigators will use a Latin square, repeated measures design which will consist of 12 subjects participating in four experimental conditions.There will be an interval of 1 week between each of the four conditions, which will serve as a washout period. At the end of each of the 5 sessions, the subjects will rest in a reclining chair for 15 minutes while their heart rate, blood pressure, oxygen saturation and breathing are monitored. Subjects that have a blood systolic blood pressure > 140 or diastolic pressure > 90 or SPO2 < 92% will be asked to remain in the laboratory for 15 additional minutes and the vital signs will be repeated. If the blood pressure and/or peripheral capillary oxygen saturation (SPO2) remain outside of the criteria mentioned above, the subject will be instructed to seek assessment by their health provider and the incident will be reported to the Institutional Review Board. Subjects will also be asked to report any discomfort.

6. Conditions and Keywords

Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study

Intermittent Hypoxia

Keywords

Inspiratory threshold loading

7. Study Design

Primary Purpose

Treatment

Study Phase

Not Applicable

Interventional Study Model

Factorial Assignment

Model Description

Latin square, repeated measures design to study the effects of IH administered alone and in combination with inspiratory threshold loading on the above stated respiratory parameters.

Masking

Participant

Masking Description

We will use a Latin square, repeated measures design which will consist of 12 subjects participating in the following four experimental conditions: There will be an interval of 1 week between each of the four conditions, which will serve as a washout period. IH+ITL: Subjects will be exposed to a session of IH (45 minutes, 2 minutes of hypoxia alternating with 1 minute of hyperoxia) followed by 5 sets of ITL at 80%MIP (10 breaths per set). IH: Subjects will only be exposed to a session of intermittent hypoxia. Sham IH +ITL: Subjects will be exposed to a single 45-minute session of sham IH (normoxia). This will consist of the subject breathing room air (FiO2=21%) through a 4 way valve connected to the hypoxicator. Exposure to normoxia will be followed by 5 sets of ITL at 80%MIP (10 breaths per set). Sham IH: Subjects will be exposed to a single 45-minute session of sham IH (normoxia) alone.

Allocation

Randomized

Enrollment

20 (Actual)

8. Arms, Groups, and Interventions

Arm Title

IH + ITL

Arm Type

Experimental

Arm Description

Arm Title

Intermittent hypoxia (IH)

Arm Type

Experimental

Arm Description

Subjects will only be exposed to a session of intermittent hypoxia.

Arm Title

Sham IH + ITL

Arm Type

Experimental

Arm Description

Arm Title

Sham IH

Arm Type

Sham Comparator

Arm Description

Sham intermittent hypoxia subjects will be exposed to a single 45-minute session of sham IH alone.

Intervention Type

Other

Intervention Name(s)

Intermittent Hypoxia

Other Intervention Name(s)

Intervention Description

A single session of IH will last for 45 minutes and will consist of alternating phases of hypoxia(FiO2 :9%-11%) and hyperoxia (FiO2 :22%-38%). Each hypoxic interval will last for 2 minutes whereas the hyperoxic interval lasts for 1 minute each (15, two-minute episodes of hypoxia and 15, one-minute episodes of hyperoxia).

Intervention Type

Other

Intervention Name(s)

Inspiratory Threshold Loading

Other Intervention Name(s)

ITL

Intervention Description

Subjects will undergo inspiratory threshold loading using a commercially available Threshold IMT device (Power breathe®). ITL will be administered at an intensity of 80% of the individual's maximal inspiratory pressure (MIP). The subjects will be instructed to take 10 deep, forceful breaths through the threshold device followed by at least 2 minutes of rest. The process will be repeated 4 more times for a total of 5 sets of 10 breaths each.

Intervention Type

Other

Intervention Name(s)

Sham Intermittent Hypoxia

Other Intervention Name(s)

Normoxia

Intervention Description

Subjects will be exposed to a session of sham Intermittent hypoxia.This will consist of breathing room air for 45 minutes through a hypoxicator.

Primary Outcome Measure Information:

Title

Maximal Inspiratory Pressure will be measured across all groups

Description

Time Frame

Change between 15, 30, and 60 minutes

Title

Ventilatory responses to inspiratory loading will be measured across all groups

Description

Time Frame

Change between 15, 30, and 60 minutes

Title

Mouth occlusion pressure (P0.1) will be measured across all groups

Description

Time Frame

Change between 15, 30, and 60 minutes

Secondary Outcome Measure Information:

Title

Heart Rate Variability (HRV) will be measured across all groups

Description

Heart Rate Variability (HRV): HRV will be assessed to determine the autonomic response to intermittent hypoxia. HRV will be measured using a 3 lead ECG and HRV recording kit.

Time Frame

Change between 15, 30, and 60 minutes

10. Eligibility

Sex

All

Minimum Age & Unit of Time

18 Years

Maximum Age & Unit of Time

40 Years

Accepts Healthy Volunteers

Eligibility Criteria

Inclusion Criteria: Participating in three or fewer musculoskeletal strength training sessions per week at an intensity equivalent to 7-10 on the Modified Borg's scale Participating in three or fewer cardiovascular endurance training sessions per week at an intensity equivalent to 7-10 on the Modified Borg's scale Exclusion Criteria: Diagnosis of cardiovascular disease (Hypertension, arrhythmias, coronary artery disease, congenital and valvar heart diseases) Diagnosis of neuromuscular disease Diagnosis of any neurological disease Presence of concurrent medical illness including infection, fractures Diagnosis of obstructive sleep apnea Diagnosis of obstructive/restrictive lung disease Diagnosis of exercise induced asthma Forced expiratory volume at one second/forced vital capacity (FVC) <80% and/or FVC<80% of predicted value indicating airway obstruction Subjects on prednisolone therapy or selective serotonin reuptake inhibitor (SSRI) therapy will be excluded from the study. Diagnosis of epilepsy or history of seizures and attention deficit disorders Pregnancy Diabetes History of coagulation disorders History of chronic pain Body mass index(BMI)> 35kg/m2 Subjects on prescription medicines such as beta blockers and other drugs that are prescribed in any of the exclusionary disorders listed above. Any other factor that in the investigators' opinions would prevent response to training or create an unsafe condition for the subject.

Overall Study Officials:

First Name & Middle Initial & Last Name & Degree

Daniel Martin, PhD

Organizational Affiliation

University of Florida

Official's Role

Principal Investigator

Facility Information:

Facility Name

University of Florida

City

Gainesville

State/Province

Florida

ZIP/Postal Code

32611

Country

United States

12. IPD Sharing Statement

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