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Biomedical subjects

I Kuwahira

Publications and source records attributed to I Kuwahira.

6 recordsLinked to original sources
PubMed1991

O2 uptake and CO2 elimination during mechanical ventilation with high frequency oscillation.

This study was intended to elucidate gas exchange in a quasi-steady state during high frequency oscillatory ventilation (HFO) in terms of arterial blood gases, tidal volume(VT) and frequency of oscillation (f). Firstly, experiments were performed on anesthetized, paralyzed and tracheostomized dogs using a piston-type oscillator with a fresh air bias flow. The f values employed in the animal experiments were 10 to 30 Hz, and VT values were 1 to 3 ml/kg of body weight. Changes in PaO2 observed during HFO could be expressed by the equation PaO2 = 125.2-60.3/(VT X f), which closely coincided with the alveolar ventilation equation for O2, i.e., PaO2 = 125-78/, VA, Where P(A-a) O2 and O2 consumption were assumed to be 25 Torr and 90 ml/min, respectively. PaCO2 during HFO deviated from the curve of the alveolar ventilation equation, PaCO2 = constant/, VA at a higher VT x f, and was distributed along the hyperbolic curve of PaCO2 = 1/, VA + 14.7. This suggested that HFO shows a certain limitation in CO2 elimination. Secondly, indicator gas transport through straight tube models for two directions, i.e., wash-in and wash-out, were observed. Wash-in of indicator gases (He, N2 and SF6) in terms of indicator appearance time at the other end of the tube changed as a function of VT x f. The effect of increasing f at a fixed VT on the wash-in was much less than that of increasing VT at a fixed f. The heavier gas (SF6) was washed in faster than the lighter gas (He) although wash-in of each indicator gas was closely related to the function VT x f. Washout in terms of the appearance time of indicators in the opposite direction was, however, strongly dependent on VT, and the effect of increasing f at a fixed VT on wash-out reached a limit beyond a certain f. It was concluded from the present study, that both convective dispersion and augmented diffusion play important roles, although they are not clearly distinguished, as gas transport mechanisms during HFO. The difference between inspiratory and expiratory gas transport modes could be explained by differences in flow profiles, relative important of convective dispersion, and/or time required for gas mixing in the airways.

Animals↗
PubMed1990

Acute respiratory failure in multiple sclerosis.

A 23-year-old woman developed acute respiratory failure in the course of multiple sclerosis. The lack of bulbar dysfunction, the presence of quadriplegia, and the bilateral diaphragmatic weakness indicated the presence of spinal cord lesions involving pyramidal tracts bilaterally. Magnetic resonance imaging revealed a cervical demyelinating lesion between C1 and C3.

Acute Disease↗
PubMed1989

Effect of cold pressor test on carbon monoxide diffusing capacity in normal subjects.

We investigated changes in the pulmonary carbon monoxide diffusing capacity (DLco) during the cold pressor test (CPT) on 25 normal subjects. In 10 of them we also observed changes in circulatory parameters by a computerized dual cadmium telluride detector system, using an equilibrium radionuclide blood-pool label. DLco and DLco per unit of alveolar volume (DLco/VA) averaged in the control period were 29.4 +/- 4.1 ml/min/mm Hg, 6.1 +/- 0.8 ml/min/mm Hg/l (mean +/- SD). During the 2nd minute of CPT, DLco increased by 3.6 +/- 1.5% and DLco/VA by 5.1 +/- 1.5% (mean +/- SE). The systemic blood pressure increased by 17% (mean increase) whereas the heart rate and the stroke volume remained unchanged. The increases were small but significant (p less than 0.05, p less than 0.01, respectively). We conclude that the increase in DLco is due to cold-induced systemic vasoconstriction followed by a passive shift of blood into the pulmonary vasculature.

Adult↗
PubMed1989

A computerized standard flow-generator for spirometer calibration.

We analyzed the dynamic characteristics of a newly designed standard flow generator (SFG) to be used for spirometer calibration. The SFG consisted of a computer, large-bore cylinder, and piston driven by a high torque motor. The computer develops numerical equations to simulate a flow-volume pattern with different convexities of the descending limb. The excursion of the piston was processed according to the computer-developed equation. The computer's numerical solutions were compared to those of the SFG and agreement of the values of the peak flow, forced expiratory volume, and flow-volume pattern was satisfactory in repeated trials. Application of an external resistive load (3.5 cm H2O/sec) did not change the flow output. However, there were several minor disagreements due to the dynamic characteristics of the SFG. In an emphysema pattern the ascending limb of the generated flow-volume curve flattened and the descending limb was less convex compared to the preset pattern. When the SFG was generating sinusoidal waves of high frequency (e.g., 10.0 Hz) the flow output was deformed. The newly designed SFG was used to examine the dynamic characteristics of rolling-seal spirometers. There was an overshoot of the peak flow, over-convection, and oscillations of the descending limb in the spirometer output. These deformations were more prominent with the severe emphysema pattern. It is concluded that the SFG can be very useful in the examination and calibration of spirometers.

Computers↗
PubMed1987

Seadragon VI: a 7-day saturation dive at 31 ATA. V. Cardiovascular responses to a 90 degree body tilt.

Cardiovascular deconditioning (CD) has been reported to occur in weightlessness, bed rest, and head-out water immersion. An expanded intrathoracic blood volume results, at least initially, in all these diverse conditions. Subjects in hyperbaric environments exhibit cephalad redistribution of blood volume, which also occurs in weightlessness, bed rest, and head-out water immersion. This physiologic similarity led us to suspect that CD may also occur as a consequence of hyperbaric exposure. We examined this possibility in 3 young male subjects during a 7-d dry saturation dive at 31 ATA. Changes in blood pressure, heart rate, and stroke volume were measured before and during 15 min of the 90 degree body tilt. These changes, expressed either singly or in combination, provided indications of CD during and immediately after hyperbaric exposure. One of the principal indicators of CD was the inability to exert adequate vasoconstriction. In addition, 1 subject fainted during hyperbaric exposure, whereas no such episode occurred before or after the exposure. These findings suggest that inappropriate orthostatic reflexes may be evoked by hyperbaria and reduced physical activity over the period of confinement. It should be noted, however, that CD was already evident within 24 h of hyperbaric exposure, suggesting that the initial phase of CD was unrelated to physical confinement. We postulate that CD occurs during hyperbaric exposure as an expression of cardiovascular and neurohumoral adaptation to an expanded central blood volume with a reduced total blood volume.

Adult↗