Regulation of arterial pCO2 in reproductive age subjects is gender-associated

Background The resting arterial pCO2 set point (38±4 mmHg) is influenced by many factors. Hyperventilation is caused by hypoxia via central and peripheral chemoreceptors, e.g. by ketoacidosis (Kußmaul breathing) or lactic acidosis (strenuous exercise). In addition, overarching factors can change the ventilatory drive. Research question: To analyze the gender aspects of resting pCO2 before starting a cardiopulmonary exercise test (CPET). Method: We analyzed a CPET databank of the Division of Pulmonology, MedUniGraz. Most of the investigations were performed due to explained or unexplained dyspnea. They comprised 2916 investigations, performed between 2010 and 2022. We removed all duplicates, incomplete data sets, investigations with peak VO 2 below the 5 th percentile, peak heart rate below the 5 th or above the 90 th percentile, and peak systolic blood pressure above the 90 th percentile, according to reference values [ 1 ]. Results: We identified 511 subjects that met all criteria (349 females and 162 males). Characteristics (mean±SD): age 54±15 yr, height 169±9 cm, weight 72±14 kg, peak work rate 132±45 W, peak VO2 1.75±0.56 L/min, resting arterial pO2 84±10 mmHg, resting arterial pCO2 35.8±3.5 mmHg. Gender differences: PCO2 in females vs. males in all subjects, subjects≥45 yr, and subjects