Gas Exchange Mechanism during High Frequency Ventilation

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  • Hiraoka Hitoshi
    The first department of internal medicine, Nihon University School of Medicine

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  • Ｈｉｇｈ　ｆｒｅｑｕｅｎｃｙ　ｖｅｎｔｉｌａｔｉｏｎのガス交換メカニズムに関する研究　　とくにＨｉｇｈ　ｆｒｅｑｕｅｎｃｙ　ｊｅｔ　ｖｅｎｔｉｌａｔｉｏｎを中心として
  • High Frequency Ventilation ノ ガス コウカン メカ
  • High Frequency Jet Ventilationを中心として

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Pulmonary gas exchange was investigated in normal anesthetised rabbits and dogs during high frequency jet ventilation (HFJV) and high frequency piston ventilation (HFPV) by measuring PaO2, PaCO2, tracheal pressure and minute ventilation (VE) by capacitance pneumograph (C. P). During HFJV (0.5-20 Hz) on rabbit, quadratic regression correlation was found between oscillatory frequency and PaO2 or PaCO2. The highest value of PaO2 and the lowest value of PaCO2 were found around the frequency of 4 to 8 Hz. The highest VE was also found on these particular frequencies. A hyperbolik regression correlation compatible with alveolar equation was found between VE and PaO2 or PaCO2.<BR>Above data suggested that the blood gas value was determined by VE measured by C. P, not by oscillatory frequency. The largest VE was found between 4 to 8Hz. These particular frequencies may be associated with resonant frequency of the rabbit lung.<BR>During HFJV on dog, linear correlation was found between oscillatory frequency and PaO2 or PaCO2. The value of PaO2 decreased and of PaCO2 increased in association with increment of frequency. Above data suggested that the response to HFJV was different between rabbit and dog.<BR>During HFPV on rabbit, linear correlation was found between oscillatory frequency and PaO2 or PaCO2. The value of PaO2 increased and of PaCO2 decreased with increment of frequency. No clear correlation was found between VE and PaO2 or PaCO2 on HFPV.<BR>In conclusion, gas exchange mechanism might be the same in HFJV and HFPV, since blood gas value was determined by VE on HFJV and by VT X f on HFPV.<BR>Bulk flow and diffusion are main factors for gas exchange on low frequency, and augmented diffusion, circulating current (Disco lung) and bulk nondiffusive exchange mechanism may be important factors on high frequency ventilation.

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