Cardiopulmonary parameters and organ blood flows for workers expressed in terms of VO2 for use in physiologically based toxicokinetic modeling

Abstract

ABSTRACT Minute ventilation rates (VE), alveolar ventilation rates (VA), cardiac outputs (Q), liver blood flow (LBF) and kidneys blood flows (KBF) for physiologically based toxicokinetic modeling and occupational health risk assessment in active workers have apparently not been determined. Minute energy expenditure rates (E) and oxygen consumption rates (VO2) in workers during exertions and their aggregate daytime activities are obtained by using open-circuit wearable devices for indirect calorimetry measurements and the doubly labeled water method respectively. Hundreds of E (in kcal/min) and VO2 (in L of O2/min) were previously reported for workers. The oxygen uptake factors of 0.2059 ± 0.0019 and 0.2057 ± 0.0018 L of O2/kcal during postprandial and fasting phases respectively enabled conversion of E into VO2. Equations determined in this study based upon more than 25 000 published measurements enable the calculation of 15 parameters in the same worker only by using the VO2 reflecting workload. These parameters, notably VE, VA, VE/VO2 VA/Q, Q, LBF and KBF were found to be interrelated. Altering one of these changes the order of magnitude of the others. Q, LBF and KBF decrease when supine adults at rest switch to an upright position. This effect of gravity diminished when VO2 increased. The fall in LBF and KBF during exertion might enhance muscle blood flow as reportedpreviously. Taken together these equations and data may improve the accuracy of physiologically based toxicokinetic modeling as well as occupational health assessment studies in active workers exposed to xenobiotics. List of main abbreviations: AVOD: arterioveinous oxygen content difference.BMI: body mass index (in kg/m2).BSA: body surface area (in m2).BTPS: body temperature and saturated with water vapor.Bw: body weight (in kg).E: minute energy expenditure rate (in kcal/min).FGE: organ blood flow factor for the gravitational effect on blood circulation.H: oxygen uptake factor, volume of oxygen (at STPD) consumed to produce 1 kcal of energy expended.KBF: kidneys blood flow (in ml/min).LBF: liver blood flow (in ml/min).PBF: liver or kidneys blood flows expressed in terms of percentages (in %) of Qsup C values: namely PBF = (LBF or KBF/Qsup C) x 100.Q: cardiac output (in L/min or ml/min).Qsup C: cardiac output for the cohort of males or females in supination (in ml/min).STPD: standard temperature and pressure, dry air.sup: values measured when adults are in the supine position.up: values measured when adults are in the upright position.VDphys: physiological dead space at BTPS (in L).VT: tidal volume at BTPS (in L).VA: alveolar ventilation rate at BTPS (in L/min).VA/Q: ventilation-perfusion ratio (unitless).VE: minute ventilation rate at BTPS (in L/min).VO2: oxygen consumption rate (i.e. the oxygen uptake) at STPD (in L/min).VQ: ventilatory equivalent for VO2 (VE at BTPS /VO2 at STPD)