| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1997: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
The acute lung mechanical responses to hypoxia were studied in the open-chest, paralyzed and vagotomized rabbits (n=7) at different positive end-expiratory pressure (PEEP) levels (2,5 and 8hPa ; randomly arranged), and compared the results with those of histamine injection (n=5). The tracheal flow and pressure were measured during tidal mechanical ventilation (respiratory rete : 40/min). Total lung resistance (R<@D2L@>D2) and total lung clastance (E<@D2L@>D2) were calculated breath by breath using linear regression. The influence of difference in the viscosity between the hypoxic (10%O<@D22@>D2) and normoxic gas(25%O<@D22@>D2) on the E<@D2L@>D2 measurement was corrected. The ratio of the increased value to the baseline value of R<@D2L@>D2 and E<@D2L@>D2 was defined as Percent Increase Ratio (PIR-R<@D2L@>D2 and PIR-E<@D2L@>D2, respectively) The PIR-E<@D2L@>D2/PIR-R<@D2L@>D2 values in hypoxic trial were significantly larger than that in histamine trial at 2 hPa PEEP (hypoxia ; 0.91(]SY.+-。[)0.23, histamine ; 0.37(]SY.+-。[)0.065, P<0.05). The negative PEEP dependency was noted in terms of PIR-E<@D2L@>D2/PIR-R<@D2L@>D2 in hypoxic condition (PIR : 8.07(]SY.+-。[)4.22<@D1**@>D1,1.73(]SY.+-。[)0.78, PIR-E<@D2L@>D2/PIR-R<@D2L@>D2 : 0.91(]SY.+-。[)0.23<@D1**@>D1,0.23(]SY.+-。[)0.11 ; 2 and 8 hPa PEEP, respectively : <@D1**@>D1 : P<0.05 compared to 8 hPa). The increase of E<@D2L@>D2 at histamine injection has been explained to be mainly derived from the tissue distortion secondary to the bronchial constriction. Thus, our results suggest that the increase of E<@D2L@>D2 at low PEEP partially includes the tissue response independent of bronchial constriction, such as contractile interstitial cells and imply that this hpoxic response of the lung tissucis sensitive to the increase of parenchymal tethering at the high PEEP.
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