ペンシル型CCD生体顕微鏡システムを用いたin vivo肺微小循環と肺胞呼吸の同時可視化

抄録

We succeeded in visualizing in vivo perialveolar microcirculation and individual alveolar respiration in rats, by our high resolution intravital charge-coupled device videomicroscopy system.To elucidate the relevance and usefullness of our methods, we investigated their behavior 1) under control conditions, 2) during increased tidal volumes (TV), 3) during positive-end expiratory pressure (PEEP) application, and 4) during exposure to hypoxia. We recognized a sheet-like flow pattern in capillaries, and observed semi-collapsed capillaries at end-inspiration while flow continued. The latter indicate existence of“vascular waterfall phenomenon”. When TV was increased from 2.5 to 5ml, the alveolar size was increased from 30±10 to 65±18μm (n=21, p<0.05), and the red blood cell velocities in perialveolar capillary were significantly decreased from 910±210 to 290±140μm/sec (n=21, p<0.05). Following PEEP application with TV of 5ml, the alveolar diameter was increased even more to 80±20μm (n=12, p<0.05) and the flows of microvessels stopped temporarily at end-inspiration. We also visualized that precapillary arterioles clearly constricted from 34±6 to 28±6μm in response to hypoxia (n=9, p<0.05).In conclusion, the intravital pencil lens-probe videomicroscopy can be a powerful tool for in vivo observation of perialveolar microcirculation and alveolar respiration under important physiological conditions such as changing TV, application of PEEP, and exposure to hypoxia.