<原著>気管支喘息の肺循環動態 : ネコ摘出還流肺における各種気道収縮物質投与時の肺微小循環および気道反応に及ぼす影響

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Ventilation perfusion mismatch and bronchial edema are two of the important clinical features in bronchial asthma. In order to elucidate these subjects from the viewpoint of pulmonary microcirculation, the isolated and perfused lung of cat was used, and bronchoconstriction was provoked by the intratracheal injection of acetylcholine (ACh), histamine (Hist) and a platelet activating factor (PAF), and the microvascular pressure was measured both by the servo-null micropuncture (MP) method and the venous occlusion (VO) method. Thirty-four cats were perfused with diluted autologous blood (hematocrit 10.3±2.9%) at a constant flow (173.6±57.3ml/min). The blood flow was set to obtain the pulmonary arterial pressure (P_<PA>) of 15cmH_2O when the left atrial pressure (P_<LA>) was 8cmH_2O and the airway pressure (P_<AW>) was 7 cmH_2O. After the start of perfusion, normoxic (F_IO_2=0.30,F_ICO_2=0.05,F_IN_2=0.65) gas was used to ventilate the lungs of the cat at a tidal volume of 15ml/kg/body/weight+5ml. ACh, Hist and PAF were injected either into the trachea or into the perfusate for comparison. The doses of these bronchoconstrictors were predetermined at a minimal dose to induce at least 15% increase of P_<AW>. The changes of P_<PA>, P_<LA>, P_<AW> and pulmonary venular pressure (P_<VENULE>) were monitored. The lung resistance (R_L) and dynamic compliance (Cdyn) were calculated from the changes of airflow rate (V), tidal volume (V) and P_<AW>. The injection of ACh into the trachea did not increase the P_<PA> significantly, and the P_<VENULE> (MP) and P_<VENULE> (VO) remained stable. Hist injection into the trachea increased the P_<VENULE> (MP) (p<0.05) and P_<VENULE> (VO) (p<0.1), while the P_<PA> was not significantly increased by the injection. PAF injection into the trachea resulted in the significant increase of P_<PA> and P_<VENULE> (VO) (p<0.01), and P_<VENULE> (MP) also increased in some of the cases. The administration into the perfusate both of ACh and Hist resulted in the significant increase of P_<PA> along with the increase of P_<AW> except a case in Hist injection. PAF, when injected into the perfusate, induced the increase of P_<PA>, while the P_<AW> remained constant. The changes of R_L were almost identical to the changes of P_<AW>. Thus the effect of bronchoconstricting substances on the pulmonary circulation is considered to be much greater when the substances were injected into the perfusate than injected into the trachea. From the results it may be concluded that the mechanical changes of the airway, e.g. bronchoconstriction, little affect P_<VENULE> and do not aggravate the bronchial edema through the increase of pulmonary venous tone which should raise bronchial wall microvascular pressure. On the other hand, Hist and PAF raised the P_<VENULE> even when these drugs were administered in the dose equivalent to the amount to cause bronchospasm in the same degree. In summary, the author's deduction is as follows, bronchoconstriction itself does not aggravate bronchial mucosal edema, but some chemical mediators cause the increase of P_<VENULE> probably by their direct effect on pulmonary vessels.
近畿大学の論文
1989-03-25

<原著>気管支喘息の肺循環動態 : ネコ摘出還流肺における各種気道収縮物質投与時の肺微小循環および気道反応に及ぼす影響

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