The breathing system is also connected to a glass cylinder containing a floating puck, which is set in motion as per the settings for frequency and amplitude. In IPPV mode the frequency selectable ranges from 75 to 240 breaths per minute (BPM). A switch to HFOV mode changes the frequency range to 750 to 2400 "breaths" or more accurately cycles per minute. The "tidal volume" during HFOV is generally an order of magnitude less than it would be during IPPV and is now used to set up an oscillation of the molecules of gas from the breathing system down to the alveoli. This oscillation helps promote the diffusion of the different gasses in the system. The animal now only vibrates slightly, gas exchange is accomplished by the diffusion of molecules as motivated by the difference in partial pressure gradients of the different gasses. No longer do you have the gross movement of the respiratory cycle so annoying to the microsurgeon.
Also incorporated into the MicroVent II is a system that allows you to connect to either vacuum directly or an active or a passive scavenging system with the flip of a switch.
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