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Use of the f/VT with Geriatric patients
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Picture of jogger
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Does anyone use a higher number than 105 for geriatric patients? Can you wean them from vent support based on this measurement.Is a f/VT of < 150 considered ok to continue weaning?I am considering using this tool as a guide on whether a geriatric patient is ready to be weaned from ventilator support based one a initial one minute trial on psv of 5 cpap = peep.
 
Posts: 13 | Location: Greenwwood,ar.,united states | Registered: November 09, 2003Reply With QuoteReport This Post
<Horacio>
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My friend: F/Vt index will not longer used, Please read the recent article : "A Randomized, controlled trial of the role of weaning: Predictors in clinical decision making." Crit Care Med 2006, 34:1-5
 
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Horacio,
much appreciation for your bringing this article to our attention. I was able to get to the abstract, here is link to "A randomized, controlled trial of the role of weaning: Predictors in clinical decision". Here is my take on this information. Rather than offering that the f/VT calculation should go out the window, perhaps it is suggesting that as Jogger has perhaps observed that the classic 105 threshold that Yang and Tobin originally found as the predictive threshold is not the threshold for all patient populations. I am not going to go and dig up the citations, but I have read verifications of the predictive strength of the f/VT many times. Is it totally the answer of will they or won't they on any given day, no. Is it one of the best tools we have as to whether they probably should go to T-bar, or should they go to CPAP/PSV, or are they a probable wash for the day, yes, but I will qualify that particularly as to the last, that of weaning efforts being predicted as a wash. Here is one of the main points this article drives home to me. It is not so much that the f/VT is a useless value, its predictive strength will continue to make it a useful tool in weaning, rather this piece drives home the thing we must never forget when weaning, and that is that there is no predictive tool or assessment that is up to the task. There is no physician, nurse or RT that can just examine any patient and their data and say, they just can't or they will and have any validity. I have seen this proven over and over and over as we had terminal wean and extubation patients fly, and rarely, but sometimes even go on to improve. Is this the result of some miraculous event as families want to believe as their loved one breathes unsupported when they have been told over and over, sometimes for weeks, they would expire without that machine and tube. The only totally valid predictor of can they or can't they is to just take them off and give them a chance. This of course must be done at a reasonable point in the progress of the patient's disease process with as much supportive data as can be brought to bear on the likelihood of success with very close monitoring, but this is the only test that has proven to work. Sort of like jumping off a cliff to see if you can fly, but if you have a good parachute, and know how to and are willing to use it, you will get your answer, and it will be definitive, at least for that moment in time.

Jogger, I just want to offer some thoughts on the collection of this value. I believe I have read that collection on vent and off vent will produce equal values. This has not been my experience, although I am still quite willing to examine evidence on this. It is so much more convenient to the process if the collection of weaning data can be done though the vent circuit, I just remain skeptical. We just opened our new facility in Fort Worth, and have 4 patients, but no vent patient yet, but we will be doing comparisons between parameters collected on the vent and off the vent. (Any one else that would like to do this and submit me your data, perhaps we can verify or blast the on vent measurements. I am talking just VE, f, avg.VT and f/VT, at your facilities standard baseline for this measurement, and then off the vent using the process I will describe. Collect a couple of months and send to gary@ventworld.com. Let me know if you would like to contribute, I will reply with a simple form and a simple protocol for collection of the data.) Currently I am partial to off vent, but am hoping to be convinced otherwise. The reason I am skeptical of on vent is that f/VT is often collected at various levels of support ranging from 0/0 to 12/whatever PEEP, and beyond. In my previous personal observations in which I would collect the data both before and after I observed frequently similar, but almost never equal data. What we are attempting to assess with f/VT in my opinion is what will that patient do when completely removed? Any PEEP, any PS, any triggering resistance, any tubing resistance, any mechanical dead space that they will not deal with when off completely, and any number of unpredictable variables that will be different when breathing on T-Bar/T-collar and off vent seems to me to affect the end result. Is this difference enough to affect the usefulness of the result? Possibly not, but I am of a mind that if I am going to collect data and produce a result I want that result to be as accurate as possible. 1 or 2% difference is probably insignificant, but my observations have offered that it might be more. I'll get back with you when I have a little more solid data.

Jogger, I wonder first about your method of collection suggested. You describe a 1 minute CPAP trail no specific level, just what PEEP has been, and PSV of 5. That could be PEEP of anything. If we are going to predict potential success without the machine attached, might as well go for some baseline level like 3 or 5, I just never like 0. The PS of 5 is probably fine; I have worked with 5, and 8. If you have a machine with ATC, that level might be a good place to take this measurement. I still think that any support may well skew the result. The gold standard for me for collection of f/VT to achieve the most useful value goes as follows: (this is just my way of doing it, I figured this out over time and have little but my observations to support it, but I hope you will see obvious logic) Equipment needed NIF-T or some similar device, double one way valved T. You will need a way to entrain O2 into the inspiration side of the T. The NIF-T comes with an adaptor that has a 19mm end that you can connect your flowing T-bar to. I like thermovents with O2 entrainment adaptor. I hope that description is not too complex. You are T'ing off the side of the valved T so you can provide supplemental O2 while you collect the information. Hypoxemia will also skew the result, you will be providing supplemental O2 during your off vent SBT so you should provide during this pre trial assessment of potential ability to tolerate. The next steps involve obtaining what I call "full engagement" of the respiratory drive. I have seen therapists who pull patients directly from complete rest settings where the patient had no respiratory activity for hours on full support, and start this process, proclaim the patient as apneaic, and go on to other tasks. I like to use full rest (no respiratory engagement) settings between SBTs. A patient has to be turned down gradually from these settings. I start with a low rate SIMV like 4 with a solid PSV level like 15, something that will give about the same SpontVT as their set VT. I just wait until they start triggering consistently. Then I go to CPAP and allow them to get used to the job of doing all of their own rate and depth setting. Next I work the PS down until I am at somewhere in the ballpark of PEEP 3, PS 8. I watch them a little longer until it seems f is consistent, and VE is compatible with life. If they fail to make it to this point for any reason, I know they are by no means safe to pull off; they may well be unsafe for any weaning activity. I have had patients who could get to this point, but couldn't make the jump to completely unsupported. I will work them as tolerated in CPAP. If this is the case I collect values from the vent readouts and clearly document that they were collected "on vent". If they can't make it to this point, they failed the weaning parameter attempt, I document that and return to rest settings, holding weaning. It may sound like this is a drawn out process, but it usually is not. It usually takes only 1-5 minutes to get full engagement, but without that you do not have good predictive results. Once to 8/3 or some similar I place them on my one way T with O2 side streamed from the insp side. Using a filter isolated mechanical respirometer (Wrights) I start collect VEs and counting RRs. I am looking for a couple of consistent minutes to indicate that respiratory drive is leveled off. I record the VE and RR from the full minute of observation; calculate the avg VT and SBI and that is where I hang my hat. I prefer a SVC rather than a NIF, and that rounds out what I consider weaning parameters.

What is the optimal threshold to use as predictive is the next question that bears consideration. I have found that if the classic 105 is used as the threshold for difficult to wean patients then you will leave some out. 150 is very aggressive and there will be few left out, but you may launch on some that are verging on unsafe for unsupported breathing. I have set the threshold at 120 in the protocol I use. We use that threshold to determine whether to try them supported or unsupported. < 120 goes to T-bar/T-collar, >120 goes into CPAP/PSV trial. In the CPAP leg we set PSV to keep f high 20s to low 30s. We monitor all physiological parameters available in both directions very closely and end weans based on demonstrated intolerance thresholds being met. We will progress a high f/VT patient on to unsupported SBT from CPAP if they demonstrate excellent tolerance of the trial and do fine on low PS levels. Also even if they have a elevated f/VT, if they have tolerated the weaning parameter process with no changes in monitored parameters we may just go unsupported with them to see.

So, what threshold, what method, is it even useful? After working from NIFs for so many years I find the f/VT, RSBI or SBI, whatever it is called so much more useful. I do not expect to use NIFs at all at my new location. I have had no experience with it, but am excited that our vents will give us p0.1, and we will have access to volumetric CO2. Until something better comes along that I can get so easily that is better, I will continue to use the f/VT calculation, but I will not consider it the answer to can they or can't they. That is my advice.
 
Posts: 147 | Location: Buckeye Az | Registered: January 27, 2006Reply With QuoteReport This Post
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Interesting reads
1) Cohen JD. Shapiro M. Grozovski E. Lev S. Fisher H. Singer P. Extubation outcome following a spontaneous breathing trial with automatic tube compensation versus continuous positive airway pressure. [Journal Article. Randomized Controlled Trial] Critical Care Medicine. 34(3):682-6, 2006 Mar.

2) Soo Hoo GW. Park L. Variations in the measurement of weaning parameters: a survey of respiratory therapists.[see comment]. [Journal Article] Chest. 121(6):1947-55, 2002 Jun.

OBJECTIVES: Respiratory therapists differ in the methods used to obtain weaning parameters. A questionnaire survey was conducted to better characterize those differences. DESIGN: A questionnaire survey was conducted among respiratory therapists from nine hospitals in the Los Angeles area. The four-page, 32-question instrument was self-administered and anonymous. Responses were tabulated for analysis. SETTING: Respondents from nine hospitals, three hospitals with residency training programs and six community hospitals without training programs in the Los Angeles area. PARTICIPANTS: One hundred two respiratory therapists. RESULTS: There was no universally acknowledged group of weaning parameters, although four parameters were named by > 90%. There was wide variation in methods used to obtaining weaning parameters. Almost all (91%) obtained measurements with the patients breathing their current fraction of inspired oxygen, but there was great variability in the ventilator mode used to collect these parameters (T-tube, continuous positive airway pressure, pressure support), with an equally wide range of pressures added to each mode (0 to 10 cm H(2)O). There was great variation in the time (< 1 to > 15 min) before recording weaning parameters. Measurement of parameters was done either with bedside instruments or read from the ventilator display. The maximal inspiratory pressure had great variation in the duration of airway occlusion (< 1 to 20 s), with the most frequent time frame being 2 to 4 s. Differences were noted between therapists from the same hospital as well as between hospitals. CONCLUSIONS: There is great variation among respiratory therapists when obtaining weaning parameters. This calls for further standardization of the measurement of weaning parameters.

3) Ely EW. Meade MO. Haponik EF. Kollef MH. Cook DJ. Guyatt GH. Stoller JK. Mechanical ventilator weaning protocols driven by nonphysician health-care professionals: evidence-based clinical practice guidelines. [Review] [75 refs] [Journal Article. Review] Chest. 120(6 Suppl):454S-63S, 2001 Dec.

Abstract Health-care professionals (HCPs) can provide protocol-based care that has a measurable impact on critically ill patients beyond their liberation from mechanical ventilation (MV). Randomized controlled trials have demonstrated that protocols for liberating patients from MV driven by nonphysician HCPs can reduce the duration of MV. The structure and features of protocols should be adapted from published protocols to incorporate patient-specific needs, clinician preferences, and institutional resources. As a general approach, shortly after patients demonstrate that their condition has been stabilized on the ventilator, a spontaneous breathing trial (SBT) is safe to perform and is indicated. Ventilator management strategies for patients who fail a trial of spontaneous breathing include the following: (1) consideration of all remediable factors (such as electrolyte derangements, bronchospasm, malnutrition, patient positioning, and excess secretions) to enhance the prospects of successful liberation from MV; (2) use of a comfortable, safe, and well-monitored mode of MV (such as pressure support ventilation); and (3) repeating a trial of spontaneous breathing on the following day. For patients who pass the SBT, the decision to extubate must be guided by clinical judgment and objective data to minimize the risk of unnecessary reintubations and self-extubations. Protocols should not represent rigid rules but, rather, guides to patient care. Moreover, the protocols may evolve over time as clinical and institutional experience with them increases. Useful protocols aim to safely and efficiently liberate patients from MV, reducing unnecessary or harmful variations in approach.

I have some other that show that reduction of SIMV rate is a poor way to liberate (wean) a patient from a vent as well as reduction in PS levels. Articles 1 and 2 I just thought were interesting when looking at SBT and then also weaning parameters. Best practice for me is to place a patient to ATC with 5 of PEEP on my Drager E4 and see how they do, if they can manage this on their own we call them electronically extubated and pull the tube. Mangement is classified as as a RSBI <105 with Vt greater than 5ml/kg. Sometimes this takes a minute or so for the patients to start breathing on their own after continous full suport but they will strat breathing on their own. If they don't I start to wonder why I even tried in the first place, never gotten there yet but who knows maybe someday. Some patients also increase their rate quickly when support is removed but then slow down as they get used to the new vent style. In my experiences this is where most therapist change back to full support to early. You must give the patient a chance to adjust. Just my two cents


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Posts: 104 | Location: Springfield, MO | Registered: March 08, 2004Reply With QuoteReport This Post
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Thanks for the related references, and the great words of wisdom and experience. Thanks a million for your two cents.
 
Posts: 147 | Location: Buckeye Az | Registered: January 27, 2006Reply With QuoteReport This Post
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Jogger,
I have spent over 10 years of my carreer in a geriatric hospital.
The first thing you need to look at is the patients overall health and/or prior ADLs.
Your long time COPD patients actually will do better by using RSBI guidelines. They do not have enough reserve to perform NIFs and VCs.You also must get them back to their own baseline ABG values and use those as the guidelines (low FiO2,CPAP and low PS works fairly well for most).Check you pre-albumins and ensure good nutritional support. The geriatric "jet-set" are not noted for good nutritional standards to begin with.
S/P CVAs need the NIF component along with RSBI/VC. ALso early intervention with rehab to help regain muscle loos is imperiative. We used to do respiratory muscle training prior to weaning to help ensure success.
CABGs are the easiest and fastest to wean. They have become the closest to text book weaning.
Your other challenge will come from you multi system failures. Base your weaning on the bodies needs as it starts to correct its own problems.
Weaning is an art form and you are the artist.
Don't be afraid to pull ideas from the archives of your forefathers...some of the old ways may still be the most appropriate, but we have let technology take over and forgot the power of our own brains.
 
Posts: 74 | Registered: June 14, 2006Reply With QuoteReport This Post
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quote:
Originally posted by jogger:
Does anyone use a higher number than 105 for geriatric patients? Can you wean them from vent support based on this measurement.Is a f/VT of < 150 considered ok to continue weaning?I am considering using this tool as a guide on whether a geriatric patient is ready to be weaned from ventilator support based one a initial one minute trial on psv of 5 cpap = peep.
 
Posts: 74 | Registered: June 14, 2006Reply With QuoteReport This Post
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