Add an in-line, adjustable PEEP valve on the expiratory limb of each patient.
An in-line, adjustable PEEP valve is also a good candidate for a flow restrictor on the inspiratory limb, see our flow restrictor page >>
An in-line PEEP valve is a PEEP valve for which the vented air is collected—as opposed to vented to the room—such that the vented volume can be passed on to the ventilator through the remaining parts of the expiratory circuit. For almost all ventilators the individual PEEP valves will have to be placed in-line: most ventilators rely on a comparison between outgoing and incoming volumes to detect leaks, and some ventilators, especially anesthesia ventilators, will not even work when they don’t receive back all of the volume that has flowed out into the patient’s circuits initially.
However, most commercially available, adjustable PEEP valves we encountered are not in-line. We did find some adjustable (magnetic) inline PEEP valves, but they are not for sale everywhere in the world, and they did not perform well in our initial tests. We have therefore designed several options to convert adjustable PEEP valves to in-line valves. We are currently also testing a completely printable in-line, adjustable PEEP valve.
Advice and comments from our contributors
Please note that the obtained individual PEEP will be the sum of the ventilator PEEP and the PEEP set by the individual PEEP valve. For example, to set a PEEP equal to 12cmH20 for patient A and 16cmH20 for patient B, with an adjustable PEEP valve with minimal value 2cmH20 PEEP, one could set up the ventilator and in-line PEEP valves as follows:
- ventilator setting at PEEP = 10cmH20
- individual PEEP valve for patient A at 2cmH20, resulting in individual effective PEEP = 12 cmH20
- individual PEEP valve for patient B at 6cmH20, resulting in individual effective PEEP = 16 cmH20
Alternatively, one could set the PEEP on the ventilator to zero, and use only the individual PEEP valves at, e.g., 12 cmH20 and 16 cmH20. In that case, please note that some ventilators always provide a minimal PEEP, even when they are set to zero.