I am in school to become an RT. I need help on understanding IPPB. The two vents we have to know at this time is the Mark Bird 7 and Bennett PR. Can anyone help me understand this concept of IPPB? Some of my questions are as follows: what affects insp. time, what affects FIO2, purpose of a retard valve, how are secretions cleared from the respiratory tract during IPPB?

Helpless,
IPPB is basically an automated Ambu bag with a set pressure. It is classsified as a pneumatically powered, pressure cyled ventilator. Meaning that it does not need electrical power to work and it will continue inspiration untill set pressure is meet. When the IPPB is triggered into inspiration the Machnine will push a set flow at the patient filling up their lungs, as their lungs fill up with gas the pressure also increase, this rise in pressure to the set pressure is what cycles the machine into expiration.

Secretions are cleared due to getting air behind the secretions and allowing for a more productive cough.

I however do not recommend IPPB, because it normally will overinflate compliant alveoli and never open ateletactic alveoli due to slower time constants. IPV works much better for secretion removal and recruitment of alveoli.

Light

You have a flow adjustment on the front of the bird increase and decrease that affects the inspiratory time. It is the same as peak flow rate but doesnt have a set number. You set your flow and peak pressure but tidal volume varies since that isnt set. There is a sensitivity setting on side that determines how hard you have to drawn in to initiate a breath. There is a small knob on the front of the bird 7 that you can push in for a hundred percent or pull out for mixed gas by air entrainment. The approximate percent is 40 with knob pulled out. The only way to know for sure what oxygen level you are delivering is to analysis it. You can add a blender to the machine to deliver preset oxygen level. The retard valve is added to the exhalation port of the circuit to hold open the airways during exhalation. The doctor orders how much retard he would like. The retard cap has holes of varying sizes. I have been doing therapy for 30 years and we use to use IPPB with retard a lot. I used the bird mark 7 mostly. The Bennet Pr works basically the same but the design is different and I am not as familiar with it. So to the question of what affects inspiratory time, flow does.

To add to what's above.

From memory so "buyer beware"

The Bird IPPB machines cylce into inspiration when the preset pressure is reached. You set the flow rate and also can have it entrain room air or work totally off the gas source. From the extremes of... 1) patient very SOB and needing to be unloaded to 2) patient not acutely SOB but needing to open up alveoli and/or raise secretions, ..you might want very different pressure/flow/input settings.

The PB machine cycles from inspiration to exhalation when the pressure has been reached and flow decays (a true pressure support). You can "set", really adjust to some degree, the flow. Then also there is the Termination setting which affects how much flow decay needs to occur. So high flow will reach pressure sooner (prematurely?), but could last longer than on Bird with same flow setting if flow termination extended it.

To get a good feel for this, breath on both and adjust the settings from one extreme to the other.

I did a lot of totally useless "therapy" with both machines. Such was done in the "fee for service" era when insurance companies would pay for anything ordered by Doctor Marcus Welby. But I also did a fair amount of effective therapy with these. I seemed to have better luck with the Bird. At end inspiration you can occlude the exp port for a bit of insp. hold (in select patients). If the patient wouldn't hyperventilate you could actually get a bit of collateral circulation going and improve certain patients. Bipap and IPV are the modern incantations of IPPB. I heard of one hospital where the docs still order IPPB. The RT's just take a Bipap to the room and give the IPPB that way with the individual patient circuit there.

IPPB should be of historical and technical interest. But I doubt you'll be using IPPB machines of yore at all in clinical practice.

I like Jeff's answer to a point as the two most common IPPB machines do work differently. The Bird used a magnetic disk and was terminated inspiration when the set peak pressure was achieved. The PB PR-2 and TV-2P where, as he stated true pressure support devices which termanated inspiration when a preset terminal flow was achieved. This was usually set at about 5 L/min and could be slightly modified. When I 1st started in RT the PR-2 was our intensive care ventilator and was used for years after the influx of volume ventilators at St. Joseph's in Tucson in their recovery room. Very effectively I must add. We used the Bird Mark 7 and Mark 14 as transport ventilators with Air-Evac out of Phoenix since they were very durable and easy to manipulate with just the use of a a respirometer to monitor the exhaled volumes. When volume ventilators took over the ICU mission, these venerable pressure ventilators were relegated to IPPB Tx. They were very much abuse just as I see small volume nebulizer therapy being abuse today but they did play a vital role with those feeble old folks who just weren't able to get in enough volume to effective cough. It's a shame thay've pretty much disappeared since we now accomplish the same task with the more expensive NIV devices. Kind of reminds me of blow-bottles and PEP.