Pressure support is above peep

The pressure support works WITH the patients inspiratory effort. It doesn't ever "take over" as long as the patient is making respiratory effort. It also doesn't wait for the end of the patient effort to "top up" the breath. PS and patient effort work simultaneously. That being said, a patient making weaker efforts will likely require more "help" from the pressure support to generate sufficient volumes, whereas a patient who is making stronger efforts will need less. It's ultimately a balance between patient effort and machine support. If the patient is not making any effort, PSV may not be the best mode for them. They may need to recover further from the underlying insult that lead them to be ventilated before PSV is tried again. Hope that helps.

@@RespiratoryReview Yes now i get it fully. Thank you very much!🙏🙏

Jonathan Downham Hey Jonathan yeah email me and we'll figure out a good time.

Hi Rashad. Yes PS can be used during non-invasive ventilation. Most modern ventilators have “non invasive” modes where the patient can be receive CPAP+PS via a face mask or other NIV interface.

@@RespiratoryReview woww,thank you for your quick response..

Do you have any live session (certificate program)on ventilator settings?

Pressure support ventilation requires patient effort - which won’t happen if you paralyze them. So you can’t paralyze people for PSV. If you did, there is a built in safety mechanism of the ventilator called APNEA ventilation (or back up ventilation) which will take over and ventilate the patient. So you need a controlled mode of ventilation if you plan to use paralysis (or deep sedation - which also can lead to apnea). Hope that helps.

Great question. Setting PS is a bit of an art. You want to adjust to achieve an appropriate tidal volume, decrease work of breathing, but allow the patient to take on enough of the work of breathing to exercise their respiratory muscles. Interestingly, patients control their minute ventilation with their respiratory centre in the medulla, and increasing the pressure support (increasing the tidal volume) doesn't tend to increase the minute volume - they just breath slower to compensate. So as mentioned in the video we are less able to tightly control the blood gas in PSV. Hope that answers your question.

RespiratoryReview Thank you. Can one give "too much" PS, causing respiratory distress/uncomfortable sensation to the patient? I would assume so, which would tie up with your reply that this is the art of medicine.

Yes definitely. Giving too much PS does a couple of things. Firstly it exposes the lungs to the well known deleterious effects of large pressure changes (deltaP as it's sometimes called), secondly it almost entirely unloads the work of breathing from the patient, which defeats the purpose of PSV. We want them to be using their respiratory muscles and contributing to the WOB. Giving too much PS is a very quick way of making someone ventilator dependant - resp. muscles atrophy and they can't tolerate not being on the vent. We've all seen that happen!

RespiratoryReview Great video and even better ( hardly seems possible) replies to questions. Looking forward to the next installment.

Not sure if this is a question or not but appreciate you posting. PSV is pressure limited, flow cycled .

@@RespiratoryReview Hi yes you are correct, that it is pressure-limited. I cant recall now but I believe my comment might've been a response to an error about the control variable of PSV referenced in this video, which would be flow not pressure .

@@johntadros50 No problem. I’d recommend you take a look at the video on phases of a breath where I cover what limit, cycle, control variables etc are. It seems like you’re confusing some of them a bit. Flow is not controlled in PSV. You’ll notice I don’t mention any variable as a controlled variable in this video.

@@RespiratoryReview Oh sorry you might have misunderstood what I meant by Flow -controlled. A control variable is the primary mechanism by which a breath is delivered/regulated so in the case of PSV that would be flow. A common mistake people make when thinking of PSV is that pressurized air is being delivered but this is not the case. Flow is delivered and that flow creates a pressure which we limit with the pressure support parameter.

@@johntadros50 Sorry John you're mistaken here. Flow is variable in PSV. It isn't controlled by the ventilator. Look up Pilbeam, S.P. (2015). Mechanical Ventilation: Physiological and Clinical Applications. Elsevier Health Sciences

The patient decides when to breath. IF they don’t take a breath (apnea) for 20 seconds, it will trigger the ventilator to take over and deliver breaths at a preset “backup rate”. If the patient is initiating breaths there is no RR that we set. They choose how many times a minute to breathe. The back up rate only kicks in if they go apenic for 20sec (or whatever we set the apnea time threshold to).

@@RespiratoryReview thanks sir

Sir wat to do if rise time is oblique nt straight nd wat is its significance if it is oblique