Demand Valve for Pulmonary Edema?

[CivilDefense2002]

My agency is currently looking at the options for ventilation and O2 delivery. It was decided the MTV/FROPVD/Demand Valve resuscitator was the way to go instead of BVM. This being in light of the new AHA guidelines recommending two-handed mask seal, and the studies showing demand valve to cause less gastric distention.

I have heard about the utility of demand valve resuscitators in pulmonary edema. I've been told that it was the "prehospital CPAP" before the commercial units came available. Plenty of anecdotes from the "old school" medics I've talked with. I'm looking for any research on the efficacy of the demand valve for spontaneously breathing patient with APE. It'd be especially useful to find something comparing it to commercially available CPAP units. Only demand valve research I've been able to find is for ventilating apneic patients.

Seems to me that the demand valve would provide a fair amount of inspiratory PAP during inhalation with the 160 LPM demand flow, and none on expiration. Considering the extra work of breathing needed to overcome CPAP flow during expiration, this lack of flow/pressure during expiration with the demand valve might even be a plus. Kinda a bit like BiPAP I imagine. Maybe it would be better to just use the demand valve and not bother with also keeping a CPAP generator too.

Thoughts?

CivilDefense2002

[AZCEP]

You and your associates have made a critical error in considering using the demand valve for any patients.

CPAP and BiPAP are not the same mechanism, and need to be used long before a demand valve. All of the information from your "old school" peers needs to be severly discounted. Their "anectdotal" experiences have no place in the current EMS environment.

The continuous pressure of CPAP is where the benefit lies. The generator creates the pressure to maintain airway patency. The demand valve will allow the airways to collapse, only to be forced back open with the next ventilation cycle. You have no way to measure the pressure that is being generated by a demand valve either. A BVM gives you a feel for compliance, a CPAP/BiPAP generator will only provide pressure to a preset level that can be monitored.

The AHA guidelines recommending a two-hand mask seal are not new. They've been published since the 1996 revisions. A demand valve, by itself, is just as likely to cause gastric distension as any other ventilation device used without a secured airway.

[VentMedic]

On another thread, OXY-PEEP for CPAP?, you'll find an explanation of CPAP and PEEP. There are also some links for more reference material.

Now, let us remember the Elder Valve briefly ( a history lesson for the youngsters) and then put it back to rest since we now have safer forms of ventilation on the market. The Elder Valve via mask; high flows at high pressures = gastric distention, turbulent flow, ineffective ventilation. Via tube; overinflation, pneumothorax. For Pulmonary Edema: BVM or a portable ventilator for ventilation with PEEP or a CPAP/BIPAP system (can also be some ventilators for effective NIV).

On the Demand Valve, if the patient can trigger the demand valve, great for ventilatory assist. But by mask that requires a tight seal so the patient can effectively generate greater than -20 cm H20 pressure without a seal leak. Not as easy as it sounds even at -20 cm H2O. However, if you're the one pushing the button and your counting is bad.....

Dr. Norman McSwain probably got the idea for the McSwain Dart after the Elder Valve gained popularity in the 70s.

Evaluation of the Elder Demand Valve Resuscitator for use by First Aid Personnel.

Pearson JW, Redding JS Anesthesiology 1967 Vol 28 Pages 623-624 OF HISTORICAL INTEREST

The authors begin by noting that mechanical resuscitators have often been too complicated to be consistently reliable in the hands of first aid personnel. A tight mask fit is difficult to achieve and a diversity of control knobs gives rise to confusion and ineffective resuscitation. The Elder Demand Valve appears to overcome most of these objections. A maximum flow rate of 150 lpm can be delivered. This is claimed to be enough flow to ventilate in spite of major mask leaks. Flow ceases when a pressure of about 54 centimeters of water is attained, even if the button is still depressed. 10 full-time personnel of the ambulance service at Baltimore County Fire Bureau were evaluated, comparing values for mouth-to-mouth, bag-valve-mask and Elder Valve ventilation. The values using mouth-to-mouth did not differ significantly from those obtained with the Elder Valve. The same values with the bag-valve-mask were significantly less (P<0.05) than those obtained by the other two methods. The authors conclude that the advantages of the Elder Valve over previously available equipment include simplicity, delivery of 100% oxygen, ability to use two hands to maintain a mask fit, high flow rate allowing adequate ventilation in spite of mask leaks, and avoidance of personal contact with the victim. Disadvantages are the lack of ready availability and dependence on compressed oxygen as a power source.

[Chief1C]

UOE of Houston Texas makes resuscitator units, the old way. You can pick up a dual cylinder outfit with a yoke and an oxygen powered resuscitator and aspirator. The 10800A is a real nice model, again, made like they were back in the days when everything on the ambulance was heavy. We don't use it for the ambulance, however, it's more of a disaster type device. You can run a mask, and two demand valves off of it no problem. I'll throw on the link, now it may look like a museum, but I assure you it's not.

http://www.uoequipment.com/index.htm

[Richard B the EMT]

Now, my own "anecdotal" experiences with "Demand/Positive Pressure" manually triggered ventilation units, non-specific, as I don't remember the brand names of what I used to use.

On the "demand" side, with a mask properly seated and sealed on a patient's face, if the patient started to inhale, the device would push Oxygen at the patient, until the patient stopped inhaling, and the O2 delivery would stop, until the next inhalation.

On the "positive pressure" side, we long-timers could, at the push of a button, or a lever on the thing, blow out lungs and distend the abdomen way too easily, as we then delivered "full breaths" as guided by both American Heart Association and American Red Cross training, not the current "just till you get chest rise".

Yes, it is a little more difficult to use a Bag Valve Mask, but, as I see it, it does place the patient at less risk of injury from the very equipment being used to save them.

Oops, nearly forgot...the regulators had a suction unit attached to them, and the unfortunacy was, they'd deplete the tank really quick, and really didn't have that great a suctioning vacuum available.

[CBEMT]

My agency is currently looking at the options for ventilation and O2 delivery. It was decided the MTV/FROPVD/Demand Valve resuscitator was the way to go instead of BVM. This being in light of the new AHA guidelines recommending two-handed mask seal, and the studies showing demand valve to cause less gastric distention.

:shock: :shock: :shock: :shock:

The demand valve has been completley removed from my states protocols effective this month.

Unfortuntely, we still have to teach it in class because apparently it's still in the NREMT-B test.

[CivilDefense2002]

AZCEP and VentMedic: Thanks for your replies.

I completely agree, anecdotal evidence is not evidence at all. A comprehensive literature review on the use of MTV's consistantly shows lower peak airway pressures, lowered gastric distention, and increased tidal volume. The abstract to one of the more interesting recent in vivo studies comparing demand valves and BVM ventilation I have found thus far can be found at http://www.ncbi.nlm.nih.gov/sites/entrez?c...p;dopt=Abstract . There's a bunch of in vitro type studies as well, but that one is the only decent n-value study involving EMS providers and actual patients. Please also note the AHA 2006 ECC Guidelines now says demand valves may be used in non-intubated apneic patients. This is a reversal of the opinion in the 2000 Guidelines to discontinue their use until more research could be done.

I am willing to give the MTV devices a chance in light of what the research is saying. I have found some case studies indicating traumatic pneumocephalus, overventilation, pneumos, etc. but these mostly refer to the use of the 160 LPM demand valves available before 1986, with the introduction of the 40 LPM units.

This of course is only my analysis of what I've been able to dig up, but my purpose here wasn't to research the use of demand valves in apneic patients. There seems to be plenty of studies on that, just nothing I've found on their utility on spontaneously breathing patients. That's what I'm looking for before we go out and buy "cool toys" with nothing to back up their efficacy.

I am not an RT, but I believe I have a decent understanding of CPAP. I did read the other thread, by the way. I hadn't considered that since you'd only be providing flow during inspiration, you'd be allowing atelectasis during expiration. I was thinking this might be a benefit as you wouldn't have to actively "fight" the continuous flow of a CPAP generator, but I can see how providing flow only during inspiration and not expiration would allow collapse of the alveoli. While BiPAP provides lower pressure during expiration, it still keeps some amount of pressure on to keep the airways open. I'm sure this "half CPAP" would probably be beneficial in some amount, but how much so? Has there been any studies on this? Can't find any myself.

Lastly, in looking at all the different models, all of them trigger at -5 cm H2O, not -20. Again, not an RT, but I do know the default trigger sensitivity on the UniVent Eagle 754 is -2 cm H2O. They allow it to be set up to -6 cm H2O. With no experience in setting trigger sensitivity, I can only guess that -5 cm H2O would be doable for most alert, spontaneously breathing patients. Am I off base?

4cmk6: I actually have UOE's catalog. Now my staff can carry the same resuscitator case that Gage and DeSoto had on Emergency!. Might just buy the carrying case just for the cool factor. Gotta let the "inner wacker" out eventually. Not so sure about their products though. Haven't really been able to get good specs out of them, nor Allied/LSP. Seems O-Two Technologies is the only company I've been able to find who believes in spec sheets and educational materials. :?

CivilDefense2002

[VentMedic]

Lastly, in looking at all the different models, all of them trigger at -5 cm H2O, not -20. Again, not an RT, but I do know the default trigger sensitivity on the UniVent Eagle 754 is -2 cm H2O. They allow it to be set up to -6 cm H2O. With no experience in setting trigger sensitivity, I can only guess that -5 cm H2O would be doable for most alert, spontaneously breathing patients. Am I off base?

Actually those numbers do pose a lot of work of breathing. Modern ventilators have gone to flow triggering instead of pressure triggering.

For your continued reading;

http://www.umdnj.edu/idsweb/idst7100/annot...ib_example1.pdf

I have used the Oxyalator and found it relatively effective in a primitive sense. Would I want to put a patient with a severe pulmonary problem on it for any length of time? Probably not unless they were sedated and I knew what I could get away with in terms of oxygenation and ventilation. This would include ABGs, CXR and waveform analysis of pressure, flow and volume. As a back up for a non-pulmonary patient, yes this is a decent "ventilator". This device is included in a generation of "safer" demand valves in that they can be regulated for pressure and volume.

http://www.lifesavingsystemsinc.com/em100.htm

Ventilation and Oxygenation being key principles when choosing the right device for the job.

The straight demand valve is not CPAP. Review the gas flow principles of using resistances and retards that make use of flow.

Now for an article on some history of the Demand Valve, IPPB and modern CPAP.

http://ajrccm.atsjournals.org/cgi/reprint/163/2/540.pdf

[Chief1C]

I have one of those orange boxes with the demand valve from LSP. Cost wise, UOE is the way to go, you get two tanks, two set ups, one case. Same price as an LSP kit. I prefer a BVM, but I've had the opportunity to use the demand valve on multiple occasions and I do like them. Mine has the valve to use it as an inhalator as well, I find it useful for firemen who've gotten a little smoke. They seem to feel better breathing in forced oxygen, rather than just a mask, able to control how much they get and when.

[CivilDefense2002]

Actually those numbers do pose a lot of work of breathing. Modern ventilators have gone to flow triggering instead of pressure triggering.

Really... Hmm. I need to research triggering more then. Interesting that the Eagle doesn't have the better trigger system, just about all the critical care teams I know use it or the LTV1200.

Thanks for the reference, looks like its got a lot of background. I will of course be looking into CPAP more. I must admit I am not up to speed on "resistances and retards," but I will make sure I am.

4cmk6: I am looking seriously at UOE, and I like their products. But, they are actually somewhat more expensive. Their single tank demand valve/inhalator/aspirator unit is functionally identical to the LSP kit you describe, but UOE charges $874 and the LSP set is $839 at EMP. The dual-tank system is $1164. Notice also that the UOE kits don't come with acylinder, while the LSP kit does. That's another $100 per tank. I must say that UOE has much better customer service though. I haven't gotten a response from LSP after e-mailing two weeks ago.

I'm not sure what I'm going to go with. I might buy the UOE dual-tank case and the unusual dual-tank regulator, and get the aspirator and MTV from O-Two. Not sure. Much research still needs to be done on what the best buy would be. I also need to work out how much benefit would be had from the double tank system. Premie facie it seems like it'd be a benefit for a code that needed both ventilation and the use of the aspirator (it'd be a backup to the Impact 326 we've got), administering O2 to two patients (one on demand valve, one on NRBM, for example), and of course if we go with a CPAP the generator drains a single tank quick... Lot more work ahead of me with the calculations on that one...

CivilDefense2002