Clinical trial NCT01830335: Cerebral Blood Flow and PETCO2 on Neuromuscular Function During Environmental Stress
Official title: The Influence of Cerebral Blood Flow and Alkalosis on Neuromuscular Function During Environmental Stress
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE4
Conditions: Healthy Males
Neuromuscular Function
Lead sponsor: Brock University
Sponsor class: OTHER
First posted: 2013-04-12
Enrollment: 8
Sex: MALE
Minimum age (years): 18
Maximum age (years): 25
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: SINGLE_GROUP
Primary purpose: BASIC_SCIENCE

Brief summary: Environmental stress, such as low oxygen availability (hypoxia), has been associated with impaired neuromuscular performance; however, the mechanisms associated with these performance decrements remain unclear. While the majority of research suggests that the observed fatigue is related to the central nervous system, the influence of changes in cerebral blood flow (CBF) and associated changes in cerebral pH (partial pressure of carbon dioxide; PCO2) remains unexamined. In response to hypoxic stress, humans hyperventilate to maintain oxygen consumption, resulting in a hypocapnia mediated decrease in CBF and cerebral alkalosis (decreased PCO2). Previous research suggests that hyperventilation induces changes in neural excitability and synaptic transmission; however, it remains unclear if these changes are related to hypocapnia mediated decrease in CBF or cerebral alkalosis or both.

The purpose of the proposed research program is to examine the influence of changes in CBF and cerebral alkalosis on neuromuscular function during environmental stress. The research program will consist of 2 separate projects, summarized below in a table outlining the proposed protocols and resultant physiological manipulations. During each manipulation, neuromuscular function will be evaluated and compared to baseline (normoxic) conditions using a repeated measures design.

The research program will consist of 2 separate projects. Project 1 will examine the changes in CBF and alkalosis by using (a) indomethacin (decrease CBF; no change PCO2) and (b) hypocapnia (decrease CBF; decrease PCO2). Using a similar experimental design, Project 2 will examine the change in CBF and alkalosis during hypoxia by using (a) poikilocapnic hypoxia (decrease PO2; decrease CBF; decrease PCO2), (b) isocapnic hypoxia (decrease PO2; no change CBF; no change PCO2) and (c) isocapnic hypoxia + indomethacin (decrease PO2; decrease CBF; no change PCO2). During each manipulation, neuromuscular function will be evaluated and compared to baseline (normoxic) conditions using a repeated measures design.

Therefore, Project 1 will examine the separate and combined effect of changes in CBF and cerebral alkalosis on neuromuscular function independent of environmental manipulations. Subsequently, Project 2 will examine neuromuscular function during hypoxia while controlling CBF and cerebral alkalosis. It is hypothesized that changes in PCO2 and therefore, changes in cerebral alkalosis will contribute to neuromuscular fatigue independent of changes in CBF and oxygen availability.


Eligibility criteria: Inclusion Criteria:

* 18 to 25 yrs old; healthy males

Exclusion Criteria:

* diagnosed medical condition; NSAID allergy; smoker; high altitude exposure; implants

Primary outcomes:
measure: Resting motor threshold
timeFrame: Change from baseline 90-minutes
measure: H-Reflex Amplitude
timeFrame: Change from baseline 90-minutes
measure: Maximal Voluntary Contraction
timeFrame: Change from baseline 90-minutes
measure: H-reflex latency
timeFrame: Change from baseline 90-minutes
measure: Voluntary Activation
timeFrame: Change from baseline 90-minutes
Secondary outcomes:
measure: Middle Cerebral Artery Blood Flow Velocity
timeFrame: Change from baseline 90-minutes
measure: Brachial Artery Blood flow
timeFrame: Change from baseline 90-minutes
measure: Internal Carotid Artery Blood Flow
timeFrame: Change from baseline 90-minutes
measure: Blood pressure
timeFrame: Change from baseline 90-minutes
measure: Pulse oximetry
timeFrame: Change from baseline 90-minutes
measure: Heart Rate
timeFrame: Change from baseline 90-minutes
measure: End-Tidal Gas Concentrations
timeFrame: Change from baseline 90-minutes
Other outcomes:
Locations:
city: St Catharines
country: Canada
facility: Brock University
state: Ontario
Study officials:
affiliation: Brock University
name: Stephen Cheung, PhD
role: PRINCIPAL_INVESTIGATOR
References: