Derivation of physiological inhalation rates in children, adults, and elderly based on nighttime and daytime respiratory parameters

Abstract

The methodology developed in our previous studies () for the determination of physiological daily inhalation rates was improved by integrating into the calculation process, both nighttime and daytime respiratory parameters, namely oxygen uptake factors (H) and ventilatory equivalents (VQ). H values during fasting (0.2057 ± 0.0018 L of O2/kcal; mean ± SD) and postprandial phases (0.2059 ± 0.0019 L of O2/kcal) as well as VQ values for subjects at rest (27.4 ± 4.8 to 32.2 ± 3.1, unitless) and during the aggregate daytime activities (29.9 ± 4.2 to 33.7 ± 7.2) were determined and combined with published doubly labeled water measurements for the calculation of daily inhalation rates in normal-weight males and females aged 0.22–96 years (n = 1235). Depending upon the unit value chosen, the highest 99th percentiles for inhalation data were found in males aged 35 to <45 years (35.40 m3/day), 2.6 to <6 months (1.138 m3/kg-day), and 10 to <16.5 years (22.29 m3/m2-day). Means and percentiles expressed in m3/kg-day as well as in m3/m2-day suggest generally higher intakes of air pollutants in children than in adults and in males than in females (in µg/kg-day or µg/m2-day) for identical exposure concentrations and conditions. For instance, means in boys aged 2.6 to <6 months of 10.99 ± 3.50 m3/m2-day and 0.572 ± 0.191 m3/kg-day are 1.3- and 2.5-folds higher, respectively, than those in adult males 65–96 years old (8.42 ± 2.13 m3/m2-day, 0.225 ± 0.059 m3/kg-day).