Objective CO2 sensitivity (ventilatory response to changing arterial CO2) is regulated by central medullary chemoreceptors. We compared CO2 sensitivity during a 5% CO2 rebreathe test within 10 days of sport-related concussion (SRC) and again after clinical recovery, and in healthy controls.

Design Case-control.

Setting University laboratory.

Participants Concussed athletes (CA, n=23, 15.4±1.2 years, 56% male, 7.5±2 days since injury) and healthy athletes (HA, n=17, 15.7±1.7 years, 59% male, no SRC within the past year).

Interventions (or Assessment of Risk Factors) Participants breathed room air for 5-minutes and then 5% CO2 for 3-minutes during which end-tidal CO2 (EtCO2, by capnograph), respiration rate (RR), and ventilation were measured using spirometer. CA were seen weekly until recovered and returned for physiological testing after return-to-play (43.5±31 days since Visit 1). HA repeated testing 49.4±21 days after Visit 1 (p=0.50).

Outcome Measures Respiratory Rate (RR, breaths/min), ventilation (Liters per min, L/m), EtCO2 (mmHg), and CO2 sensitivity (L/min/mmHg)

Main Results At Visit 1, groups did not differ in resting RR (CA: 19.8±0.2, HA: 19.5±0.7, p=0.14) but CA had a higher EtCO2 (CA: 37.9±4.2, HA: 34.8±2.8, p=0.01). During rebreathing, groups did not differ in CO2 sensitivity (CA: 0.46±0.14, HA: 0.42±0.11, p=0.50). At Visit 2, groups did not differ in resting RR (CA: 19.8±0.2, HA: 19.8±0.1, p=0.98) or EtCO2 (CA: 35.5±3.9, HA: 36.2±3.1, p=0.52), but they differed in CO2 sensitivity (CA: 0.50±0.13, HA: 0.43±0.11, p=0.05).

Conclusions Concussed adolescents did not demonstrate altered CO2 sensitivity within 10 days of injury; however, they had increased CO2 sensitivity after clinical recovery, suggesting persistent physiological alteration of central medullary function after recovery from SRC.