We examined breath-by-breath (B-B) variations of FRC (delta FRC) and their effect on measured O2 and CO2 gas exchange in 52 2- to 4-min segments of continuous air breathing obtained in 29 patients (age range 6--50 yr). Respiratory frequency ranged from 13 to 43 breaths/min, VE from 6.7 to 22.5 l/min (BTPS), and expired VT from 234 to 1,370 ml (BTPS). Computer analysis was based on the following source data measured at the mouth: inspired (VI) and expired (VE) gas flow, FN2, FO2 and FCO2. The analysis provides B-B evaluation of VI, VE, delta FRC in terms of VN2, and VO2 and VCO2 at the mouth and at the alveolar level, i.e., after correction for delta FRC. Significant B-B variations of FRC were found in all studies. delta FRC ranged from +360 to -360 ml (BTPS). For single respiratory cycles VI - VE is primarily a function of N2 exchange at the mouth (VMN2). VO2 and VCO2, uncorrected for delta FRC, are significantly more dispersed about mean values than the corrected gas uptakes (P less than 0.0005). The data support the view that the assumption of VIN2 = VEN2 is invalid for single respiratory cycles. Determination of breath-by-breath VO2 and VCO2 should therefore, not be based on steady-state gas uptake equations. It requires measurement of both inspired and expired breath volumes and evaluation of N2 gas exchange.
Starting from the assumption that one can literally perceive someone's anger in their face, I argue that this would not be possible if what is perceived is a static facial signature of their anger. There is a product–process distinction in talk of facial expression, and I argue that one can see anger in someone's facial expression only if this is understood to be a process rather than a product.
Measurement of mean pulmonary blood flow (Qp) as a function of pulmonary inert gas (N2O) uptake was studied with the aid of a mathematical model, fast response measurement of gas flow and gas concentrations at the mouth, and digital computer analysis of the data. The model treats the total pulmonary inert gas uptake as the sum of dead space, alveolar, lung tissue, and pulmonary blood flow uptakes. Analysis of any two breaths during breathing of a gas mixture (39 percent N2O, 21 percent O2, 40 percent N2 or He) in terms of the soluble (N2O) and the insoluble (N2 or He) inert gas yields two simultaneous equations with two unknowns which can be solved for Qp. No assumptions are required about the magnitude of the alveloar, dead space, or lung tissue volumes and constant FRC is not a requirement. The validity of the mathematical model and its sensitivity to known measurement errors was studied by computer simulation of respiratory gas exchange for N2O and N2. Comparison of Qp (N2O) with the direct Fick method (O2) in five anesthetized dogs showed agreement within plus or minus 20 percent. The proposed method has promise as a clinical method for determination of cardiac output on a breath-to-breath basis during regular breathing at rest or during exercise.
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