Could Apnea Induce Hypoalgesia?

Study Overview
=================
Brief Summary
-----------------
A randomized controlled trial (RCT) in healthy subjects will be conducted with the following aims: (1) Explore the effect of low pulmonary volume dynamic apnoea bouts on Pressure Pain Threshold (PPT) and conditioned pain modulation (CPM); (2) analyse whether CPM response correlates with apnoea induced hypoalgesia; (3) examine the association between apnoea bouts, Rate of Perceived Exertion, hypoxemia and Heart Rate changes in PPT.

Detailed Description
-----------------
A randomized controlled trial (RCT) in healthy subjects will be conducted with the following aims: (1) Explore the effect of low pulmonary volume dynamic apnoea bouts on Pressure Pain Threshold (PPT) and conditioned pain modulation (CPM); (2) analyse whether CPM response correlates with apnoea induced hypoalgesia; (3) examine the association between apnoea bouts Rate of Perceived Exertion, hypoxemia and Heart Rate changes in PPT

Official Title
-----------------
Could Apnea Induce Hypoalgesia? An Explorative Randomized Controlled Trial

Conditions
-----------------
Pain, Apnea

Intervention / Treatment
-----------------
* Other: Apnea
* Other: Control Intervention


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Healthy participants 18-30 years Currently pain-free Basal SpO2 ≥95% Exclusion Criteria: Diabetes diagnosis Hypertension or hypotension diagnosis Pharmacological treatment Frequent pain during last month Drug consumption Self-harming behaviours Pregnant or potentially pregnant Cardiac or respiratory pathology Splenectomy or spleen disease Having performed moderate or high intensity physical activity 24 hours prior to the study Not having slept the previous night Alcohol intake 24 hours prior to study.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Experimental Group<br>Experimental Group | Other: Apnea<br>* In both experimental and control groups participants walked on a treadmill at 5.5 km/h with 5º inclination for 6 minutes. The experimental group (EG) added throughout the 6 minutes intervention the following breathing pattern cyclically: 5 seconds breathing normally followed by 10 seconds of low volume apnoea, performing a total of 24 cycles of normal breathing continued by apnoea.<br>|
| Sham Comparator: Control Group<br>Control Group | Other: Control Intervention<br>* In both experimental and control groups participants walked on a treadmill at 5.5 km/h with 5º inclination for 6 minutes. The Control group (CG) performed this protocol breathing normally.<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Pressure Pain Threshold | PPT refers to the minimal amount of pressure needed to cause the first sensation of pain. The mechanical pressure algometer (PAIN TEST™ FPX 25, Wagner Instruments, Greenwich, CT, USA) counted with a round rubber disc of 1 cm2, displaying values in Kg, hence, data was expressed in Kg/cm2. Two locations, in upper and lower limbs, were examined to examine systemic hypoalgesia effects. The dorsal distal-phalange base of the thumb and tibialis anterior muscle belly, both in the dominant limb, were tested. These regions were marked with a pen before assessments, to repeat the trials in the same place. Three trials were tested in each location, with 30 seconds rest between trials. Pressure speed was paced with a metronome applying a constant force of 0.5 Kg/cm2/s ± 0.1 Kg/cm2/s. | Before and immediately after the interventions | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Conditioned pain modulation | Conditioning stimulus was applied on the contralateral limb to test stimulus, since its arrangement does not influence CPM response. Only controversial CPM response have appeared when tests and conditioned stimuli were applied on the same body region. Ischemic pain was applied as conditioning stimulus and PPT as test stimulus. Ischemic pain was provoked inflating a sphygmomanometer at the proximal region of the non-dominant arm. When inflated up to 180-200 mmHg patients were asked to actively move fingers and wrist. They were asketd to report when a 7/10 pain in Numerical Pain Rating Scale (NPRS) scale was reached. In that moment, three trials of test stimuli were applied on the dorsal distal-phalange base of the thumb in the dominant arm, while maintaining the ischemic pain perception. | Before and immediately after the interventions | 
| Heart Rate and Oxygen Saturation | We video-taped HR and SpO2 values during the 6 min interventions and 2 minutes afterwards to explore their changes during and after interventions. HR and SpO2 data were extracted in each second. These values would be graphically displayed. Peak %HRmax and minimum SpO2, and means of both variables, value would be extracted from the 6-minute interventions. HR zones or exercise-induced hypoxemia zones were also recorded. | During the intervention and for 2 minutes additionally after the end of the intervention | 
| Rated Perceived Exertion | Apnea and control interventions were explored in terms of Rated Perceived Exertion in with Borg's modified CR-10 | This outcome was assessed immediately after having finished the intervention protocols | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Pain, Apnoea, Apnea, Hypoalgesia