Some PCS patients have exercise intolerance due to abnormal CBF regulation that may be the result of concussion-induced altered sensitivity to CO2. Return of normal CBF control and exercise tolerance may be physiological markers of recovery from concussion.

No abstract

SummaryThis study assesses the diagnostic potential of a tomographic technique with phase analysis to detect premature electroventricular contraction patterns simulated by pacing in the baboon. The data of gated SPECT were analysed by backprojection of the Fourier coefficients, followed by angulation and integration to thick slices of the entire ventricular mass yielding separate ventricular contraction patterns in three perpendicular views. Electrodes were implanted in each baboon: at the sinu-atrial node; posterior, left ventricular; anterior left ventricular; on the left and the right lateral ventricular walls. The atrium was stimulated throughout at a fixed rate. Subsequent ventricular stimuli followed during the QRS complex, such to invoke the appearance of pre-excitation QRS morphology. The first points of activation (FPA) from this algorithm were correctly detected for the RV, for the anterior and posterior sites, although the latter two manifested first points in the RV. LV pacing manifested also as a FPA in the RV, but was followed by a true subsequent point in the LV.

Cerebral autoregulation (CA) maintains cerebral blood flow (CBF) constant over a wide range of perfusion pressures (MAP). However, arterial PCO2 (PETCO2) may modify CBF if brain metabolism and total oxygen consumption (VO2) are modified. During exercise MAP, VO2 and VCO2 are increased and may affect CBF. Female (13) and male (9) subjects completed a CO2 sensitivity test at rest and a graded exercise treadmill test. Heart rate (HR), MAP, ventilation (VE) and CBF velocity (CBFV) were measured in both tests. During rest CBFV (45%) and VE (221%) increased linearly with PETCO2 (58%). During exercise CBFV increased (31%) from 61 ± 16 cm/s to 78 ± 16 cm/s at 80% of VO2max. Once above the ventilatory threshold, CBFV decreased to 65 ± 16 cm/s at 100% VO2max. The changes in CBFV paralleled the changes in PETCO2 (36 ± 5 to 46 ± 6 to 36 ± 6 mmHg), despite a linear increase in MAP with VO2. Multiple linear regression indicated that PETCO2 was contributing more to CBFV than MAP (CBFV = 5.001 + (0.759 * PETCO2) + (0.313 * MAP)). During exercise CA did not maintain CBFV and PETCO2 strongly influenced it, thus ventilatory regulation (PETCO2) in exercise is critical in determining CBF. Resting CO2 sensitivity did not predict exercise PETCO2. Regulation of PETCO2 during exercise may explain the differences in CBF among individuals or conditions. One example may be the dysregulation of CBF in post concussion syndrome patients.

Vitamin D status is associated with bone health and with cardiovascular health, diabetes mellitus and cancer. Since vitamin D status is affected by food and supplement intake and by sun exposure, the ability to accurately predict vitamin D status assessed from these sources is important. The objective of this study is to evaluate the use of 3‐day diet records (3DR) including dietary supplements and a food frequency questionnaire (FFQ) not including dietary supplements to predict serum 25‐hydroxyvitamin D concentrations [25(OH)D] in 40 male and female subjects (30 to 69 yrs). Time spent in sunlight was self‐reported along with a Fitzpatrick Skin Type Questionnaire. Vitamin D intake from the 3DR was positively correlated with 25(OH)D with a curvilinear relationship and may be used to predict 25(OH)D (rs=0.60, P <0.001). FFQ was not correlated with 25(OH)D (rs=0.15, P=0.38) but the FFQ with supplements was positively correlated (rs=0.42, P=0.013). Unprotected sun exposure or skin type did not aid the ability to predict 25(OH)D levels possibly due to winter month data collection with minimum unprotected sun exposure. Intake of vitamin D from supplements must be considered when estimating vitamin D status.