ObjectivesA previous study found that individuals with blood pressure sensitivity to high sodium intake tend to have a high resting partial pressure of end-tidal CO (2) (PetCO2). The present study analyzed the test-retest reliability of individual PetCO2over 6 months, and the association of individual PetCO2with age, gender, and personality characteristics.MethodsPetCO2of 104 men and women (mean ages 42.1 +/- 1.5 years) was monitored via a respiratory gas monitor for 25 minutes during each of three sessions over an 11-day interval, and 59 subjects also participated in a 25-minute follow-up session 261 +/- 10 days later. Each subject completed the NEO Personality Inventory.ResultsPetCO2remained stable within and between monitoring sessions over a 6-month period. PetCO2was higher in men than in women, and decreased progressively over the life span. PetCO2was not correlated with the Extraversion, Openness, Agreeableness, or Conscientiousness Scales of the NEO Personality Inventory, but was highly positively associated with the Neuroticism Scale of the NEO Personality Inventory, and with its subscales.ConclusionsHigh resting end-tidal CO2tends to be a stable individual characteristic that is accompanied by a tendency to worry and experience negative emotions.