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Biomedical subjects

Y Fukuchi

Publications and source records attributed to Y Fukuchi.

At least 253 records · Page 14Linked to original sources
PubMed1981

[The effects of nitroglycol at low concentrations (author's transl)].

In the first experiment of the present study, low concentrations of nitroglycol (ethylene glycol dinitrate) which are doses corresponding to the amounts of occupational exposure, were administered to 13 mongrel dogs and the changes of blood pressure (BP) cardiac output (CO), coronary blood flow (CBF) and femoral blood flow (FBF) were observed. A multichannel square wave electromagnetic blood flowmeter was used to measure the blood flows. After the administration of nitroglycol, fall of BP and increases of CO, CBF and FBF were observed. The increase of CBF were recognized more than 1 microgram of Ng per kg of body weight. As 50-200 micrograms/kg nitroglycol was administered intravenously, although a transient increase of CBF was found, the decrease of CBF for a relatively long period was followed. This fact suggested that a state of disadvantage for the coronary circulation was caused. In the second experiment, nitroglycol concentrations in blood and urine in 22 workers in a dynamite factory were measured by Götell's method. 0-145 ng/ml nitroglycol was detected in the blood after work, with high levels being noted in workers who had frequent exposure to skin absorption. The relationship between the nitroglycol concentration in blood of the workers and the experimental results in dogs was assessed and valuable suggestions concerning further research in the study of chronic exposure to nitroglycol at low concentration were obtained.

Animals↗
PubMed1980

Intraregional basis for sequential filling and emptying of the lung.

We studied the sequential pattern of lung filing by measuring the slope of the alveolar plateau in single breath helium washouts after inhaling a bolus at a lung volume (VI) equivalent to 20. 40, 60 and 80% of vital capacity (VC). In seated subjects, prone dogs, both with the chest intact and wide open, and individual canine lobes, slopes at VI = 20% VC were more positive than those at VI = 80% VC, indicating a "first in - last out' pattern. Furthermore the range of slopes, which reflects the magnitude of sequencing, was comparable in the four situations. We conclude that sequential filing and emptying of the lung has predominantly an intraregional basis. A two compartment optimization analysis using single exponential pressure-volume curves suggests that only a small proportion of the lung needs to behave differently to produce the sequencing observed in individual lobes.

Adult↗
PubMed1979

Dual tracer single breath studies of gas transport in the lung.

We studied the ratio of the expired He and SF6 concentrations (He/SF6) after 1 litre inspirations of a gas mixture containing 5% of He and SF6. Five subjects aged 49 to 60 yrs. performed the maneuvers with both inspiration and expiration at 0.2--0.41/s or 1.5--2.01/s. In all subjects separation of the tracer gases was observed, the He/SF6 falling early to a minimum of 0.80 +/- 0.01 (mean +/- 1 SE), and increasing gradually during expiration to a maximum of 1.08 +/- 0.01. The slope of the SF6 alveolar plateau was 1.45 +/- 0.09 times that for He. Computer simulations of simultaneous convection and diffusion in an axisymmetrical series lung model predicted a pattern of He/SF6 early in expiration which corresponded qualitatively to that observed experimentally. However, the model did not predict a rising He/SF6 ratio late in expiration. This was simulated only by incorporation of parallel inhomogeneity with sequential emptying into the model analysis. Consideration of Taylor type dispersion and airway asymmetry did not influence the simulations significantly. The results suggest that differing slopes of the alveolar plateau of two tracer gases may be due to diffusion dependent concentration differences among lung units ventilated in parallel rather than due to stratification alone.

Computers↗
PubMed1977

Influence of pericardial fluid on cardiogenic gas mixing in the lung.

Respirat. Environ. Exercise Physiol. 42(1): 5-12, 1977. -In eight open-chested dogs we measured the end-inspiratory N2 concentration within 12 airways, 2.5-8.3 mm in diameter during constant flow inflations with 0.5 liter of O2 before and after the introduction of saline into the pericardial sac. The critical flow rate necessary to achieve a given end-inspiratory FN2, as well as the maximal amplitude of cardiogenic N2 fluctuations, became smaller in the presence of pericardial fluid (PF). In the presence of only 25-50 ml of saline in the pericardium the effective diffusion coefficient, incorporating cardiogenic gas mixing, decreased by as much as 50-66%, respectively. Studies in two dogs with the chest intact showed that PF caused a qualitatively similar impairment of gas mixing during breath holding. Multiple-breath N2 washouts did not reflect the decreases in gas mixing produced by PF. We believe that PF decreases cardiogenic gas mixing mainly by protecting the lung from the rotational thrust of the heart during myocardial contraction.

Animals↗
PubMed1976

Convection, diffusion and cardiogenic mixing of inspired gas in the lung; an experimental approach.

In 8 open-chested dogs, we measured the FN2 within 26 airways, 2.5-8.6 mm in diameter, during constant flow inflations with 0.5 liter of O2. At low flows the FN2 did not fall to zero but reached a plateau, at a value that was inversely related to inspiratory flow. When inspiratory flow is constant, the measured FN2 represents one point on a stationary front separating inspired and alveolar gas. At all points on the front the convective and diffusive transport of N2 is equal and opposite in direction. We quantitated cardiogenic gas mixing by comparing in vivo and post mortem the flow which resulted in a given stable FN2 value within the same airway. In vivo, this flow and therefore the calculated effective diffusion coefficient (D') was more than 5 times greater than that post mortem. Our results confiem some of the predictions made from model analyses of gas transport in the lung. However, calculations based on molecular diffusion as the sole mixing mechanism necessarily overestimate diffusion times and the magnitude of stratification.

Animals↗
PubMed1976

Influence of diaphragmatic contraction on ventilation distribution in horizontal man.

The washout of a bolus of helium (inhaled from residual volume) during relaxed expiration (RE) through a resistance was compared with that during expiration with voluntary diaphragmatic contraction (VDCE) achieved by tensing the abdominal muscles while maintaining constant expiratory flow (less than 0.4 l/s). In six subjects in the lateral decubitus position, phase IV during RE started at 58 +/- 1.6% vital capacity (VC) (mean +/- 1 SE). During VDCE, when the transdiaphragmatic pressure (Pdi) exceeded 30 cmH2O, phase IV commenced at 8.2 +/- 0.8% VC. The expired He concentration (FEHe) at lung volumes greater than 70% VC was 1.3 +/- 0.05 times that during RE. In supine subjects VDCE flattened the slope of the alveolar plateau and decreased closing volume by 3.7 +/- 0.4% VC. Our results suggest that when the diaphragm is relaxed in the horizontal subject, the hydrostatic gradient of pressure within the abdomen enhances early emptying of dependent lung zones. Diaphragmatic contraction results in more homogeneous emptying. We conclude that diaphragmatic tone influences the vertical gradient of regional volume, and hence of pleural pressure. The latter is not constant, being less during inspiration than during expiration. Therefore, differences in the changes of applied pressure between dependent and nondependent lung regions influence ventilation distribution in subjects in the horizontal posture.

Diaphragm↗
PubMed1976

Influence of bronchomotor tone on ventilation distribution and airway closure in asymptomatic asthma.

Simultaneous washouts of nitrogen (N2) and helium (He) boluses were performed in 9 seated symptom-free asthmatic patients. Recent work has indicated a correlation between the height of Phase IV (deltaIV) of a vital capacity washout and the end-inspiratory vertical concentration gradient of the gas in the lung. The deltaIV for both He and N2 washouts increased by a factor of 2 and 1.25, respectively, after isoproterenol inhalation. In addition, the amplitude of the cardiogenic oscillations increased from a mean of 0.32 per cent to 0.51 per cent for N2 and from 0.030 per cent to 0.051 per cent for He. Closing volume measured by the He bolus method was higher than that by the N2 method in 8 of 9 subjects, by 3.7 +/- 0.7 per cent vital capacity (mean +/- 1 SE, P less than 0.001). Similarly, He closing capacity was greater than N2 closing capacity in the same 8 subjects by 2.6 +/- 1.3 per cent total lung capacity (P less than 0.001). Despite a decrease in closing volume in 8 subjects, and in closing capacity in all 9 subjects after isoproterenol, the differences between the results obtained by the 2 methods remained unchanged. The slope of Phase III in both N2 and He washouts was influenced in an inconstant fashion, probably reflecting differing contributions from topographic and intraregional inhomogeneities of ventilation in these subjects. The results suggest that in patients with asymptomatic asthma the vertical gradient of regional residual volume as well as the pattern of airway closure is more uniformly distributed between apex and base of the lung. Furthermore, the slope of Phase III in either N2 or He bolus washouts may not reflect the degree of bronchoconstriction.

Adult↗