Influence of Caffeine on Psychomotor Vigilance and Carbon Dioxide Tolerance During Graded Hypercapnia
- Conditions
- Hypercapnia
- Interventions
- Registration Number
- NCT06636825
- Lead Sponsor
- United States Army Research Institute of Environmental Medicine
- 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.
Recruitment & Eligibility
- Status
- COMPLETED
- Sex
- All
- Target Recruitment
- 29
- 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
- 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)
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- CROSSOVER
- Arm && Interventions
Group Intervention Description Experimental Caffeine 400 mg caffeine capsule taken in a single dose 1 hour prior to graded hypercapnia Placebo Placebo Placebo (microcrystalline cellulose) capsule taken in a single dose 1 hour prior to graded hypercapnia Experimental Graded hypercapnia 400 mg caffeine capsule taken in a single dose 1 hour prior to graded hypercapnia Placebo Graded hypercapnia Placebo (microcrystalline cellulose) capsule taken in a single dose 1 hour prior to graded hypercapnia
- Primary Outcome Measures
Name Time Method 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 Outcome Measures
Name Time Method Ventilation 60 minutes Ventilation (L/min)
Respiratory Rate 60 minutes Breaths per minute
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 PCO2 60 minutes Partial pressure of carbon dioxide (mmHg)
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)
Trial Locations
- Locations (1)
US Army Research Institute of Environmental Medicine
🇺🇸Natick, Massachusetts, United States