Changes

'''Bi-level''' is the application of more than 1 pressure level during different breathing stages. Below is Oscar's representation of the changing pressure during The example below shows bi-level therapy in action. This is whilst using Softpap2 on a Prisma20A, at a set CPAP pressure of 12cmH2o. The difference between the machine is now applying 2 different pressures . The lower pressure of '''EPAP ''' (exhalation positive airway pressure) and the higher pressure of '''IPAP ''' (inhalation positive airway pressure) . The difference between these two pressures is termed pressure support, abreviated normally to '''PS'''. The example below shows a PS or pressure support of 3cmH2o. This is the maximum PS achievable with the available on a '''Prisma Smart''' and delivers the same support as Resmeds EPR 3, although as you will see, the differing air delivery of the two devices, affects how this pressure support shapes your breathing.

We can see clearly, If we look closely at the bi-level algorithm in use by Lowenstein. Notice we notice that following the drop from release of IPAP pressure down to EPAPpressure, the machine immediately begins to ramp back up to IPAP pressure. It meets Peak pressure is set to arrive closely aligned with the beginning of inspiration. This is how Lowenstein achieves Apnea control at lower pressures. By returning to max pressure near the end of exhalation (when Apneas develop), the airway is fully supported.

In contrast, the Resmed example below shows the very different implementation of its Bi-Level mode. The lower pressure of EPAP pressure is maintainedthroughout exhalation, it does not provide a movement toward IPAP pressure until the beginning of inspiration. Full Peak IPAP pressure is not reached until mid to late inspiration.

Often when pressure is insufficient, you can see in a Resmed trace, the second hump in the flow rate and/or the fuller second half of inspiration. The example above has pressure set to 6cmH2o and with EPR of 2 (a common minimum pressure new users are sent home with). You can see the obvious instability. This is why with a Resmed machine, the moment you switch on EPR, you are setting a new lower EPAP pressure. Not only that, you will spend a majority of time now at pressures around EPAP and only a brief time at IPAP. You must take this into consideration. If you are looking to keep EPAP where it was, but increase minimum pressurein inhalation then you would increase main pressures by the same amount as epr set.

This same principle is not generally needed with LowensteinSoftPap. SoftPap behaves in the reverse of Resmed EPR. You will spens a majority of time around IPAP pressures and only briefly drop to EPAP. This is because of does affect how each Bi-Level mode is implementedunit must be set and what conditions these two methods favour. You must use each tool by simply understanding how each tool works.