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Biomedical subjects

R Y Sun

Publications and source records attributed to R Y Sun.

At least 37 records · Page 2Linked to original sources
PubMed1987

Effects of lung volume and alveolar surface tension on pulmonary vascular resistance.

Utilizing the arterial and venous occlusion technique, the effects of lung inflation and deflation on the resistance of alveolar and extraalveolar vessels were measured in the dog in an isolated left lower lobe preparation. The lobe was inflated and deflated slowly (45 s) at constant speed. Two volumes at equal alveolar pressure (Palv = 9.9 +/- 0.6 mmHg) and two pressures (13.8 +/- 0.8 mmHg, inflation; 4.8 +/- 0.5 mmHg, deflation) at equal volumes during inflation and deflation were studied. The total vascular pressure drop was divided into three segments: arterial (delta Pa), middle (delta Pm), and venous (delta Pv). During inflation and deflation the changes in pulmonary arterial pressure were primarily due to changes in the resistance of the alveolar vessels. At equal Palv (9.9 mmHg), delta Pm was 10.3 +/- 1.2 mmHg during deflation compared with 6.8 +/- 1.1 mmHg during inflation. At equal lung volume, delta Pm was 10.2 +/- 1.5 mmHg during inflation (Palv = 13.8 mmHg) and 5.0 +/- 0.7 mmHg during deflation (Palv = 4.8 mmHg). These measurements suggest that the alveolar pressure was transmitted more effectively to the alveolar vessels during deflation due to a lower alveolar surface tension. It was estimated that at midlung volume, the perimicrovascular pressure was 3.5-3.8 mmHg greater during deflation than during inflation.

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PubMedDate not supplied

Gas exchange and haemodynamics during high frequency body surface oscillation in rabbits.

To establish the clinical feasibility of high frequency body surface oscillation (HFBSO) as a mode of controlled ventilation for infants and to examine its effects on basic haemodynamic parameters, we studied twelve intact rabbits in two groups. The animals were placed in a body chamber with their heads remaining outside through a neck-hole. The mean chamber pressure was maintained at -3 to -4 cmH2O and a piston pump, operating at 3, 6, 9, 12 and 15 Hz, created pressure swings in the chamber, thus generating oscillatory tidal volumes. A fresh-airflow of 2 1.min-1 was used over the mouth. In the first group of six rabbits, we obtained the relationship between tidal volume (VT) and frequency (f) which maintained a normocapnic state (PaCO2 = 40 +/- 2 mmHg) when the animals were paralysed. The average tidal volumes required were between 1.36 and 1.78 ml.kg-1 for the 3-15 Hz frequency range, or about 1/4 of the spontaneous tidal volume. The corresponding mean PaO2 was 66.7 mmHg at 3 Hz and 73.4 mmHg at 9 Hz. These results indicate that adequate ventilation and acceptable gas exchange took place in these experimental animals during HFBSO. In the second group, six rabbits were catheterized with catheter-tip pressure transducers in order to obtain the aortic (ABP), central venous (CVP) and intrathoracic pressures. The arterial pressure profile was severely deranged by HFBSO, but, electronic subtraction of the intrathoracic pressure swings from the ABP signal resulted in the return of the normal pressure profile.(ABSTRACT TRUNCATED AT 250 WORDS)

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