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.
肺微小循環 (pulmonary microcirculation)
Waterfall 現象 (waterfall phenomenon)
低酸素性肺血管収縮 (pulmonary hypoxic vasoconstriction)