Hypercapnia
Conditions
Keywords
Caffeine, Carbon dioxide, Cognitive Function
Brief summary
The aim of this randomized, double-blind, placebo-controlled crossover trial is to determine the effects of caffeine vs. placebo on psychomotor vigilance and carbon dioxide tolerance during graded hypercapnia.
Detailed description
Healthy and fit young adults (men and women) will participate in this study. Participants will perform two primary experimental trials on separate days, one after consuming 400 mg caffeine, and the other after consuming a non-caffeinated placebo. During each trial, participants will breathe increasing levels of inspired CO2 in a stepwise manner (0%, 2%, 4%, 6%, 8% CO2; all with 21% oxygen) during successive 12-minute stages. The endpoints of the graded hypercapnia protocol will be completion of the 8% CO2 stage, voluntary subject termination due to discomfort, or end-tidal CO2 greater than 70 mmHg. The investigators hypothesize that, compared to placebo, caffeine will lower end tidal and arterialized PCO2 and mitigate CO2-mediated decrements in psychomotor vigilance.
Interventions
OTHERGraded hypercapnia
Volunteers breathe 0%, 2%, 4%, 6%, and 8% CO2 (with 21% O2, balance nitrogen) for 12 minutes each
DRUGCaffeine
400 mg caffeine capsule taken in a single dose 1 hour prior to graded hypercapnia
DRUGPlacebo
Placebo (microcrystalline cellulose) capsule taken in a single dose 1 hour prior to graded hypercapnia
Sponsors
United States Army Research Institute of Environmental Medicine
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
DOUBLE (Subject, Investigator)
Intervention model description
Randomized, double-blind, placebo-controlled crossover trial
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* Male or female, age 18-45 * Body mass index 18.5-30.0 kg m-2 * Body mass 50-100 kg * In good health as determined by the Office of Medical Support & Oversight (OMSO) General Medical Clearance * Perform exercise at least 2 times per week * Willing to abstain from exercise and alcoholic beverages for 24 hours before each study visit. * Willing to abstain from caffeine for 12 hours prior to all study visits * Willing to abstain from caffeine for 12 hours after visits 3 and 4 * Willing to remain fasted (no food or fluid other than water) from lights out until after arrival at the laboratory the following morning on each study day (\ 10 hours) * Have supervisor approval if permanent party military or a federal employee at U.S. Army Natick Soldier System Center
Exclusion criteria
* Females who are pregnant or planning to become pregnant during the study * Females who are surgically sterile * History of severe adverse reaction to caffeine (e.g., headache, dizziness, diarrhea, insomnia) * Taking dietary supplements, prescriptions, or over the counter medication, other than a contraceptive (unless approved by OMSO & PI) * Abnormal blood count (For example: hemoglobin (Hb) outside of the typical normal values reported by LabCorp in accordance with OMSO (Normal \[Hb\] Males = 12.6-17.7 g/dL; Females = 11.1-15.9 g/dL) or hematocrit (Hct) outside of the normal ranges (Normal Hct Males = 37.5-51.0%; Females = 34.0-46.6%) levels, presence of abnormal blood chemicals (hemoglobin S or sickle cell traits) * Any history of pulmonary or cardiovascular disease * Current diagnosis of asthma (childhood asthma with no recurrence in the last 5 years ok) * Smokers or nicotine users (unless have quit \>1 month prior) * Current or recent respiratory tract or sinus infections (\< 1 month prior) * Current diagnosis of migraine or recurrent headaches (previous diagnosis with no recurrence in the last 5 years ok) * Any history of seizures * Any history of panic disorder * Blood donation in the previous 8 weeks * Positive Covid-19 test within the last month (based on self-report)
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| End-tidal CO2 | 60 minutes | End-tidal CO2 (mmHg) |
| PVT Performance | 60 minutes | Psychomotor vigilance (mean reaction time in s) |
| Carbon dioxide tolerance | 60 minutes | Time spent in graded hypercapnia protocol (minutes) |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Tidal volume | 60 minutes | Tidal volume (L) |
| Oxygen Consumption | 60 minutes | Oxygen consumption (L/min) |
| Carbon dioxide release | 60 minutes | Carbon dioxide release (L/min) |
| Heart Rate | 60 minutes | Heart Rate (Beats per minute) |
| Blood Pressure | 60 minutes | Blood pressure (mmHg) |
| Total Mood Disturbance | 60 minutes | Profile of Mood States (AU); higher number is worse mood |
| Arterialized capillary pH | 60 minutes | pH (unitless) |
| Arterialized capillary bicarbonate | 60 minutes | Bicarbonate (mmol/L)) |
| Dyspnea | 60 minutes | Borg 0-10 Scale (higher number is more dyspnea) |
| Discomfort | 60 minutes | Borg 0-10 Scale (higher number is more discomfort) |
| Headache | 60 minutes | 100mm visual analog scale (higher number is worse headache) |
| Plasma caffeine | 60 minutes | Plasma caffeine (ug/mL) |
| Plasma theobromine | 60 minutes | Plasma theobromine (ug/mL) |
| Plasma theophylline | 60 minutes | Plasma theophylline (ug/mL) |
| Plasma paraxanthine | 60 minutes | Plasma paraxanthine (ug/mL) |
| Arterialized capillary PCO2 | 60 minutes | Partial pressure of carbon dioxide (mmHg) |
| Ventilation | 60 minutes | Ventilation (L/min) |
| Respiratory Rate | 60 minutes | Breaths per minute |
Countries
United States
Outcome results
None listed