Baseline Cardiorespiratory Function in Youth with Persistent Post-Concussion Symptoms

Objective To evaluate cardiorespiratory functions in youth with persistent post-concussion symptoms compared to controls and to examine the predictive value of relevant demographic and medical variables. Background Recent studies propose that persistent post-concussion symptoms (PPCS) (e.g., headache, fatigue, or dizziness; lasting >2 months post injury) may be linked to autonomic dysregulation, initially provoked by injury but then maintained by biopsychosocial factors during recovery (i.e., pain sensitivity, behavioral avoidance of symptom triggers, worries, etc). One way that autonomic dysregulation can be detected is through monitoring cardiorespiratory dynamics such as end-tidal CO2 fraction (ETCO2), respiratory rate (RR), oxygen saturation (PsO2) and pulse rate (PR). However, the few studies measuring cardiorespiratory outcomes in concussion are restricted to the acute stage of injury. Therefore, the present study sought to examine 1) cardiorespiratory functioning in youth patients with PPCS and 2) the relationship of relevant demographic and medical variables to these outcomes. Design/Methods Participants between the ages of 13-25 were recruited into two groups: 1) n = 7 patients diagnosed with concussion and PPCS (2-9 months post-injury) and 2) n = 7 non-injured controls. Data (ETCO2, RR, PsO2, & PR) were collected using a capnometer during a 5-minute passive recording session. Results At rest, patients’ ETCO2 measurements were significantly lower than controls (p = .04) with a large effect size (d = 1.22). Besides injury status, the only significant medical or demographic variable was positive family history of anxiety, which predicted lower ETCO2 (p = .04; d = 1.35). Of note, personal history of anxiety disorder was not significantly correlated with ETCO2. Conclusions PPCS patients appear to have ETCO2 concentration below the normal range at baseline (i.e., rest), supporting the theory that disrupted autonomic regulation in this population is related to persistent symptoms. Importantly, autonomic dysregulation as measured through cardiorespiratory functioning could represent a promising treatment target for PPCS patients.