Intraoperative ventilation NEJM Study

[seinfeld]

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A Trial of Intraoperative Low-Tidal-Volume Ventilation in Abdominal Surgery

N Engl J Med 2013;369:428-37.

BACKGROUND
Lung-protective ventilation with the use of low tidal volumes and positive endexpiratory
pressure is considered best practice in the care of many critically ill
patients. However, its role in anesthetized patients undergoing major surgery is
not known.
METHODS
In this multicenter, double-blind, parallel-group trial, we randomly assigned 400
adults at intermediate to high risk of pulmonary complications after major abdominal
surgery to either nonprotective mechanical ventilation or a strategy of
lung-protective ventilation. The primary outcome was a composite of major pulmonary
and extrapulmonary complications occurring within the first 7 days after
surgery.
RESULTS
The two intervention groups had similar characteristics at baseline. In the intention-
to-treat analysis, the primary outcome occurred in 21 of 200 patients (10.5%)
assigned to lung-protective ventilation, as compared with 55 of 200 (27.5%) assigned
to nonprotective ventilation (relative risk, 0.40; 95% confidence interval [CI], 0.24
to 0.68; P = 0.001). Over the 7-day postoperative period, 10 patients (5.0%) assigned
to lung-protective ventilation required noninvasive ventilation or intubation for
acute respiratory failure, as compared with 34 (17.0%) assigned to nonprotective
ventilation (relative risk, 0.29; 95% CI, 0.14 to 0.61; P = 0.001). The length of the hospital
stay was shorter among patients receiving lung-protective ventilation than among
those receiving nonprotective ventilation (mean difference, −2.45 days; 95% CI,
−4.17 to −0.72; P = 0.006).
CONCLUSIONS
As compared with a practice of nonprotective mechanical ventilation, the use of
a lung-protective ventilation strategy in intermediate-risk and high-risk patients
undergoing major abdominal surgery was associated with improved clinical outcomes
and reduced health care utilization. (IMPROVE ClinicalTrials.gov number,
NCT01282996.)

 

[pie944]

Think it is a great article.

I wish they had not excluded people with BMIs > 35. I think you find a lot of people calculating tidal volumes based off actual body weight as opposed to taking the time to calculate the PBW. Therefore, I think a great benefit might be found in this growing segment of our population when using 6cc/kg(PBW).

I also wish they had added PEEP to the control group. I know the Drager machine's default to a PEEP of 0, but I believe most providers do add some PEEP during their cases. I may be wrong in this assessment? I just would be curious the benefit that is present when comparing a control group of larger tidal volumes with PEEP versus a 6cc/kg tidal volume with PEEP in the operating room setting.

I have been teaching anyone I interact with in the operating rooms that there is no reason to use larger tidal volumes and the importance of utilizing PBW over actual body weight for calculations.

I handed out this article today to three people, hopefully more in the coming days.

 

[BLADEMDA]

Anesthesiology. 2013 Jun;118(6):1307-21. doi: 10.1097/ALN.0b013e31829102de.

Protective mechanical ventilation during general anesthesia for open abdominal surgery improves postoperative pulmonary function.

Severgnini P, Selmo G, Lanza C, Chiesa A, Frigerio A, Bacuzzi A, Dionigi G, Novario R, Gregoretti C, de Abreu MG, Schultz MJ, Jaber S, Futier E, Chiaranda M, Pelosi P.


Source

Department of Ambient, Health and Safety, University of Insubria, Varese, Italy. [email protected]


Abstract


BACKGROUND:

The impact of intraoperative ventilation on postoperative pulmonary complications is not defined. The authors aimed at determining the effectiveness of protective mechanical ventilation during open abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function.

METHODS:

Prospective randomized, open-label, clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive end-expiratory pressure (standard ventilation strategy) or tidal volumes of 7 ml/kg ideal body weight, 10 cm H2O positive end-expiratory pressure, and recruitment maneuvers (protective ventilation strategy). Modified Clinical Pulmonary Infection Score, gas exchange, and pulmonary functional tests were measured preoperatively, as well as at days 1, 3, and 5 after surgery.

RESULTS:

Patients ventilated protectively showed better pulmonary functional tests up to day 5, fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1, 3, and 5 (mmHg; mean ± SD): 77.1 ± 13.0 versus 64.9 ± 11.3 (P = 0.0006), 80.5 ± 10.1 versus 69.7 ± 9.3 (P = 0.0002), and 82.1 ± 10.7 versus 78.5 ± 21.7 (P = 0.44) respectively. The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3. The percentage of patients in hospital at day 28 after surgery was not different between groups (7 vs. 15% respectively, P = 0.42).

CONCLUSION:

A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay

 

[BLADEMDA]

This is a controversial area. I recommend caution and common sense in applying these studies to your daily practice. In particular, a PEEP of 10 may or may not be beneficial to patients. Yes, lower tidal volumes of 6-7 ml/kg (reasonable body weight used, not actual) with a PEEP of 5 seems quite reasonable.

Take a look at these studies before jumping on this bandwagon:

http://bja.oxfordjournals.org/content/109/2/263.long


http://www.ncbi.nlm.nih.gov/pubmed/20103541?dopt=Abstract

 

[BLADEMDA]

Chest. 2011 Mar;139(3):530-7. doi: 10.1378/chest.09-2293. Epub 2010 Sep 9.

Does a protective ventilation strategy reduce the risk of pulmonary complications after lung cancer surgery?: a randomized controlled trial.

Yang M, Ahn HJ, Kim K, Kim JA, Yi CA, Kim MJ, Kim HJ.


Source

Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-Dong, Kangnam-Gu, Seoul, Korea, 135-710.


Abstract


BACKGROUND:

Protective ventilation strategy has been shown to reduce ventilator-induced lung injury in patients with ARDS. In this study, we questioned whether protective ventilatory settings would attenuate lung impairment during one-lung ventilation (OLV) compared with conventional ventilation in patients undergoing lung resection surgery.

METHODS:

One hundred patients with American Society of Anesthesiology physical status 1 to 2 who were scheduled for an elective lobectomy were enrolled in the study. During OLV, two different ventilation strategies were compared. The conventional strategy (CV group, n=50) consisted of FIO2 1.0, tidal volume (Vt) 10 mL/kg, zero end-expiratory pressure, and volume-controlled ventilation, whereas the protective strategy (PV group, n=50) consisted of FIO2 0.5, Vt 6 mL/kg, positive end-expiratory pressure 5 cm H2O, and pressure-controlled ventilation. The composite primary end point included PaO2/FIO2<300 mm Hg and/or the presence of newly developed lung lesions (lung infiltration and atelectasis) within 72 h of the operation. To monitor safety during OLV, oxygen saturation by pulse oximeter (SpO2), PaCO2, and peak inspiratory pressure (PIP) were repeatedly measured.

RESULTS:

During OLV, although 58% of the PV group needed elevated FIO2 to maintain an SpO2>95%, PIP was significantly lower than in the CV group, whereas the mean PaCO2 values remained at 35 to 40 mm Hg in both groups. Importantly, in the PV group, the incidence of the primary end point of pulmonary dysfunction was significantly lower than in the CV group (incidence of PaO2/FIO2<300 mm Hg, lung infiltration, or atelectasis: 4% vs 22%, P<.05).

CONCLUSION:

Compared with the traditional large Vt and volume-controlled ventilation, the application of small Vt and PEEP through pressure-controlled ventilation was associated with a lower incidence of postoperative lung dysfunction and satisfactory gas exchange. Trial registry: Australian New Zealand Clinical Trials Registry; No.: ACTRN12609000861257; URL: www.anzctr.org.au.

 

[BLADEMDA]

I've been using a TV of 6-7 ml/kg with a PEEP of 5 since this study came out in 2008. Whether or not I should increase my PEEP from 5 to 10 is something we can discuss here. Perhaps, on higher risk patients undergoing major surgery increasing PEEP from 5 to 10 is warranted.

http://www.ncbi.nlm.nih.gov/pubmed/18156881

 

[Ignatius J]

I've been using a TV of 6-7 ml/kg with a PEEP of 5 since this study came out in 2008. Whether or not I should increase my PEEP from 5 to 10 is something we can discuss here. Perhaps, on higher risk patients undergoing major surgery increasing PEEP from 5 to 10 is warranted.

http://www.ncbi.nlm.nih.gov/pubmed/18156881

Are you using actual body weight, IBW, or LBW? Stupid question, but just curious as I have seen folks bombing 100kg persons with "low tidal volumes" at 700cc per breath.

 

[Mman]

I actually wish I could do some sophisticated programming of a ventilator during a case. Set it for smallish tidal volumes 6 ml/kg of IBW with some PEEP for the majority of the time, but cycling up to some bigger 12-14 ml/kg breaths every 15-30 minutes. It'd be much closer to what happens in normal physiology with smaller breaths most of the time and periodic deeper sighs.

 

[BLADEMDA]

I actually wish I could do some sophisticated programming of a ventilator during a case. Set it for smallish tidal volumes 6 ml/kg of IBW with some PEEP for the majority of the time, but cycling up to some bigger 12-14 ml/kg breaths every 15-30 minutes. It'd be much closer to what happens in normal physiology with smaller breaths most of the time and periodic deeper sighs.

Great idea. GE or Drager owes you a dinner

 

[BLADEMDA]

6 ml/kg of predicted body weight. Formula: Males: PBW (kg) = 50 + 2.3 (height (in) &#8211; 60); Females: PBW (kg) = 45.5 + 2.3 (height (in) &#8211; 60)

 

[BLADEMDA]

6 ml/kg of predicted body weight. Formula: Males: PBW (kg) = 50 + 2.3 (height (in) &#8211; 60); Females: PBW (kg) = 45.5 + 2.3 (height (in) &#8211; 60)


http://www.ardsnet.org/node/77460


Predicted body weight is not as high as we would think it should be. Hence, tidal volumes are smaller than most provides are used to dialing in.

 

[BLADEMDA]

Keep this link on your smart phone.


http://www.mdcalc.com/ideal-body-weight/

 

[BLADEMDA]

Seinfeld,

I really appreciate your effort in posting that recent NEJM article. Thank You.

 

[Planktonmd]

The problem with all those studies is that they are focusing on limiting the tidal volume instead of limiting the airway pressure.
A given tidal volume can produce different pressures in different patients based on individual airway characteristics, pre-existing respiratory disease and actual body weight (not ideal or predicted body weight).
I hope some one will eventually study the effect of airway pressure on post-op complications and maybe determine what would be a protective airway pressure based on body weight (actual weight not ideal).

 

[Ronin786]

Is it normal to have patients on a tidal volume of 10-12 in routine surgery? I'd think that alone would skew the results in the researchers favor.

 

[Idiopathic]

their mean tidal volume in the control group was 720. in my short career of delivering anesthesia, ive never had a single patient with a tidal volume that high. also BMI>35 as exclusion criteria?

🙄

 

[ferning]

The problem with all those studies is that they are focusing on limiting the tidal volume instead of limiting the airway pressure.
A given tidal volume can produce different pressures in different patients based on individual airway characteristics, pre-existing respiratory disease and actual body weight (not ideal or predicted body weight).
I hope some one will eventually study the effect of airway pressure on post-op complications and maybe determine what would be a protective airway pressure based on body weight (actual weight not ideal).

Yea, theres too many universal yardstick rulesin medicine already.

The studies here arent terribly impressive like most, you can make almost anything statistically significant. Good outcomes resulting from intervention always seem to come with unintended bad which is never reflected on. So sick of these j/o trying to get published with sweeping implications based on one dimensional and linear reasoning. Just because our language and though process is more manageable in such a way does not mean the processeses of the physical and biological sciences will conform to it.

I'm just starting my surg rotation, but what is the pathophysio reasoning behind this to begin with? And whats the "rule of thumb" for this. Like surgeries of what length, pt characteristics

Is an unintended adverse effect of this some atelectasis?

 

[psychbender]

their mean tidal volume in the control group was 720. in my short career of delivering anesthesia, ive never had a single patient with a tidal volume that high. also BMI>35 as exclusion criteria?

🙄

I thought the same thing, but unfortunately, I have seen TVs that high on several occasions now. Several times as a resident, dealing with some older attendings giving me a break during a case, I would return to see TVs set in the 700-800 range. When asked why they changed my vent, they replied that I was underventilating the patient, and walked out. I have also seen that a few times when giving certain CRNAs breaks, or taking over their case at the end of the day. Until then, I never understood why Pulm/CC would need to write in their consult notes to 'please keep TV below 10mL/kg in the OR.'

 

[BLADEMDA]

The problem with all those studies is that they are focusing on limiting the tidal volume instead of limiting the airway pressure.
A given tidal volume can produce different pressures in different patients based on individual airway characteristics, pre-existing respiratory disease and actual body weight (not ideal or predicted body weight).
I hope some one will eventually study the effect of airway pressure on post-op complications and maybe determine what would be a protective airway pressure based on body weight (actual weight not ideal).

There are studies looking at Plateau airway pressure. This number should be less than 35 cm h20 or even 30 cm h20. Still, benefits of low tidal volume with PEEP have been seen even when both groups have plateau pressures less than 20.

A recent editorial in Anesthesiology (June 2013) commented that normal tidal volumes in the 8-9 ml/kg range combined with PEEP may be just as beneficial as low tidal volumes of 6ml/kg with PEEP.

Finally, I see many patients being ventilated with 650-700 ml Tidal Volumes on a daily basis. I suspect most midlevel providers are using that Tidal Volume for males and 500-550 for females.

Actual Body Weight doesn't work because we see patients who are Female, 5'1" who weigh 40 kg up to 120 kg on a daily basis.

 

[BLADEMDA]

Is it normal to have patients on a tidal volume of 10-12 in routine surgery? I'd think that alone would skew the results in the researchers favor.

Yes. Remember, we are using Ideal or Predicted body weight and not actual body weight. I suspect even in your Operating rooms most providers are using 10 ml/kg (or more) of predicted body weight.

 

[BLADEMDA]

their mean tidal volume in the control group was 720. in my short career of delivering anesthesia, ive never had a single patient with a tidal volume that high. also BMI>35 as exclusion criteria?

🙄

There are MANY studies on this topic from Critical Care literature and Anesthesia.
There are many approaches to "lung protection" modalities but all of them incorporate a low tidal volume strategy (5-7 ml/kg) with Peep (5-12). Some include recruitment maneuvers to limit atelectasis and this is the area I find most intriguing to study.

Some authors use the following:

1. Inspiratory pause
2. Escalating Tidal Volumes until Plateau pressure of 35cm h20 (every 0.5-1.0 hrs)
3. Intermittent breath with a peak pressure of 40-45 cm h20 for 10-30 seconds (every hour)
4. adjust ventilator to deliver high Peep (20) for a short interval
5. Pressure Control with Peep is just as good as Volume Control with Peep (maybe even better with morbid obesity).

 

[Planktonmd]

Actual Body Weight doesn't work because we see patients who are Female, 5'1" who weigh 40 kg up to 120 kg on a daily basis.

Actual body weight is what determines airway pressure at a provided tidal volume.
The more fat you have on top of your chest wall and your abdomen the higher the airway pressure.
And since airway pressure is the force causing pulmonary complications in mechanically ventilated patients I don't know how you can arrive to the conclusion that actual body weight is irrelevant!
Giving a tidal volume based on ideal or predicted body weight is silly in a world where obesity has become the norm.

 

[pie944]

Actual body weight is what determines airway pressure at a provided tidal volume.
The more fat you have on top of your chest wall and your abdomen the higher the airway pressure.
And since airway pressure is the force causing pulmonary complications in mechanically ventilated patients I don't know how you can arrive to the conclusion that actual body weight is irrelevant!
Giving a tidal volume based on ideal or predicted body weight is silly in a world where obesity has become the norm.

So someone who is your sex and your height, but decided to add 100 kg of extra weight has lungs of what size compared to your lungs?

If you can give a large tidal volume(10-12 cc/kg) with plateau pressures < 30 cm H20 is that acceptable? You seem to be saying that it is only the pressure that matters, or am I misreading?

 

[BLADEMDA]

Refocusing on the pressure diff erence across the lung is
important, as the peak and driving transpulmonary
(transalveolar) pressures are those that count with
respect to the causation of iatrogenic lung damage [48].
In theory, know ing the func tional residual capacity and
the trans alveolar (as opposed to plateau) static pressure
would be necessary to interpret the safety of our tidal
volume selection.


Although stretching, shearing, and small airway
trauma have been demonstrated to occur when
transpulmonary pressures are excessive, tissue tension
cannot be directly measured. Unfortunately our reliance
on airway pressures alone (PEEP and plateau
pressures) &#8211; which merge infor mation from all aircontaining
sectors, are distorted by chest wall stiff ness,
and are infl uenced by the presence or absence of
spontaneous breathing eff orts &#8211; glosses over such
realities (Figure 4). Experienced clinicians are aware
that airway pressures alone may be misleading when the
chest wall is stiffened by obesity, surgery, trauma, or
disease as well as when the patient makes forceful
inspiratory and expira tory eff orts. Even measuring
trans pulmonary pressure with the aid of an esophageal
balloon catheter may not be enough [52-54]. A
challenging aspect of managing the stresses and strains
developed within a mechanically heterogeneous lung is
the amplifi cation (or stress focusing) that occurs at the
interfaces between fully open and closed lung units [55].


http://ccforum.com/content/pdf/cc11499.pdf

 

[BLADEMDA]

Actual body weight is what determines airway pressure at a provided tidal volume.
The more fat you have on top of your chest wall and your abdomen the higher the airway pressure.
And since airway pressure is the force causing pulmonary complications in mechanically ventilated patients I don't know how you can arrive to the conclusion that actual body weight is irrelevant!
Giving a tidal volume based on ideal or predicted body weight is silly in a world where obesity has become the norm.

Your statements are not proven fact at all. It isn't airway pressure alone which determines injury but rather a number factors including transpulmonary pressure and velocity of air flow.

Many "experts" don't believe high peak pressures on morbidly obese patients undergoing Laparoscopic procedures are necessarily exposed to increased risk of pulmonary complications; the lung tissue itself may not be receiving excessive pressure.

 

[Planktonmd]

So someone who is your sex and your height, but decided to add 100 kg of extra weight has lungs of what size compared to your lungs?

If you can give a large tidal volume(10-12 cc/kg) with plateau pressures < 30 cm H20 is that acceptable? You seem to be saying that it is only the pressure that matters, or am I misreading?

No... I didn't say that pressure is the only thing that matters but can you tell me how else an increased tidal volume can injure the alveoli if it's not pressure?
And when a patient has factors that increase airway resistance (obesity, obstructive and restrictive pathology...) how do you determine the appropriate tidal volume if you ignore airway pressure?
It is too simplistic to focus only on the tidal volume and ignore airway pressure in all these studies that people keep publishing and others keep quoting.

 

[Planktonmd]

Your statements are not proven fact at all. It isn't airway pressure alone which determines injury but rather a number factors including transpulmonary pressure and velocity of air flow.

Many "experts" don't believe high peak pressures on morbidly obese patients undergoing Laparoscopic procedures are necessarily exposed to increased risk of pulmonary complications; the lung tissue itself may not be receiving excessive pressure.

Really?
Which one of your statements are proven a FACT?
I can't believe that you even think that anything in medicine could ever be proven a fact!
I can give you a million example of things that people like you thought were facts in medicine and were found to be pure crap.

 

[pie944]

No... I didn't say that pressure is the only thing that matters but can you tell me how else an increased tidal volume can injure the alveoli if it's not pressure?
And when a patient has factors that increase airway resistance (obesity, obstructive and restrictive pathology...) how do you determine the appropriate tidal volume if you ignore airway pressure?
It is too simplistic to focus only on the tidal volume and ignore airway pressure in all these studies that people keep publishing and others keep quoting.

Pulmonary volutrauma is not the same as barotrauma, they are different. That's why I asked the question, is it acceptable to have large tidal volumes in the setting of plateau pressures less than 30 cm H20? Would this avoid parenchymal injury?

I am not saying to ignore airway pressures, but I am saying a provider shouldn't base the tidal volume on their actual weight. It should be based on their predicted body weight, equations Blade posted above. That is how one determines the appropriate tidal volume based on weight based volumes. This should be the case if one wants to use 6, 8, 10, or 12 mL/kg of tidal volume. Just because one adds a few hundred pounds to their body does not mean that the lungs have increased in size.

 

[Planktonmd]

Pulmonary volutrauma is not the same as barotrauma, they are different. That's why I asked the question, is it acceptable to have large tidal volumes in the setting of plateau pressures less than 30 cm H20? Would this avoid parenchymal injury?

I am not saying to ignore airway pressures, but I am saying a provider shouldn't base the tidal volume on their actual weight. It should be based on their predicted body weight, equations Blade posted above. That is how one determines the appropriate tidal volume based on weight based volumes. This should be the case if one wants to use 6, 8, 10, or 12 mL/kg of tidal volume. Just because one adds a few hundred pounds to their body does not mean that the lungs have increased in size.

Using the same magical number plateau pressure on every patient regardless of their body mass or airway characteristics makes no sense!
I am saying that as we search for the ideal tidal volume for each patient maybe we should also be looking for the ideal pressure which all these new studies seem to ignore.
You shouldn't base the tidal volume on actual weight without taking into consideration airway pressure, since airway pressure is the only parameter other than volume that we can measure clinically (we can't directly see what happens inside the alveoli).
Maybe the volume pressure loop is a good place to start?

 

[BLADEMDA]

http://www.carefusion.com/medical-p...ation/transpulmonary-pressure-monitoring.aspx

http://www.carefusion.com/medical-products/respiratory/ventilation/avea/avea-tpp.aspx
We can measure transpulmonary pressure (an estimate of it anyway) using a device like the one above.

Best available evidence strongly suggest low tidal volume based on predicted body weight, peep in the range of 5-10 and recruitment maneuvers periodically. This is the best course of action for higher risk patients undergoing Major surgery like abdominal and open thoracotomies.

 

[FiremedicMike]

Forgive me for inserting my out of hospital vent perspective/question.

What about PCV with PEEP of 5, increasing your pressure setting to reach a TV of ~6cc/kg while looking for a tidal volume/pressure setting that gives EtCO2 of 35-45 and SpO02 of 97-99%? I'm told that EtCO2 monitoring is done primarily out of hospital and rarely inside, but it definitely helps me tweak the vent on the helicopter, could it have a place in the OR as well?

 

[WholeLottaGame7]

Forgive me for inserting my out of hospital vent perspective/question.

What about PCV with PEEP of 5, increasing your pressure setting to reach a TV of ~6cc/kg while looking for a tidal volume/pressure setting that gives EtCO2 of 35-45 and SpO02 of 97-99%? I'm told that EtCO2 monitoring is done primarily out of hospital and rarely inside, but it definitely helps me tweak the vent on the helicopter, could it have a place in the OR as well?

I realize you're a medic, but I couldn't help but laugh. The thought of doing a case without EtCO2 is just so foreign to us in anesthesia; it is standard of care for all general anesthetics and has been for awhile.

Also, most of the newer anesthesia ventilators have a mode called PCV-VG (pressure control ventilation - volume guarantee), which is exactly what you describe. It is a pressure control mode but you set a tidal volume instead.

 

[FiremedicMike]

I realize you're a medic, but I couldn't help but laugh. The thought of doing a case without EtCO2 is just so foreign to us in anesthesia; it is standard of care for all general anesthetics and has been for awhile.

Also, most of the newer anesthesia ventilators have a mode called PCV-VG (pressure control ventilation - volume guarantee), which is exactly what you describe. It is a pressure control mode but you set a tidal volume instead.

Ah, my mistake. I suppose I assumed that because I literally never see them utilized in the ED or ICU, that they were an out of hospital thing only..

Either way, my original question stands.

 

[BLADEMDA]

Forgive me for inserting my out of hospital vent perspective/question.

What about PCV with PEEP of 5, increasing your pressure setting to reach a TV of ~6cc/kg while looking for a tidal volume/pressure setting that gives EtCO2 of 35-45 and SpO02 of 97-99%? I'm told that EtCO2 monitoring is done primarily out of hospital and rarely inside, but it definitely helps me tweak the vent on the helicopter, could it have a place in the OR as well?

We adjust the respiratory rate to achieve te desired ETCO2 (35-40). Usually, the tidal volume can be set (6-7 ml/kg) along with Peep (5-10) and then the rate is adjusted as needed (usually 10-12). Of course, we can adjust the tidal volume, I:E ratio, Insp pause, etc as well as change modes of ventilation (Pressure control-volume guarantee).

The history of mechanical/artifcial ventilation is a fascinating read; today's state of the art ventilator is leaps and bounds better than what we had just 10 years ago.

We now know that how we ventilate patients in the operating room may indeed play an important role in patient outcome.

 

[BLADEMDA]

Ah, my mistake. I suppose I assumed that because I literally never see them utilized in the ED or ICU, that they were an out of hospital thing only..

Either way, my original question stands.

http://www.cardiothoracicsurgery.org/content/pdf/1749-8090-5-99.pdf

http://www.ncbi.nlm.nih.gov/pubmed/22976857

 

[BLADEMDA]

When I see high plateau or peak airway pressures despite low tidal volume I try a few basic maneuvers. Yes, the transpulmonary pressure may be low but I don't have an esophageal device in place to measure it. So, even though the high airway pressure is likely due to obesity and the surgical conditions (prone or laparascopic surgery) I will still try and limit airway pressure. I will try Pressure control first then changing the i:e ratio next.


http://www.ncbi.nlm.nih.gov/pubmed/21897297

http://www.ncbi.nlm.nih.gov/pubmed/19403595

http://www.ncbi.nlm.nih.gov/pubmed/23717224

 

[hippaA]

I can see where the medic is coming from with etco2. It's rarely used outside the OR where i work.
I don't think many nurses or RTs understand its utility. I'm the only nurse that uses it in our unit.

 

[seinfeld]

If you look at the tables of Peak pressures the difference, which was statistically significant, was 19 in the low tidal volume group and 20 in the high tidal volume group. Therefore this study showed that volutrauma is often under appreciated.

As far as whether people actually ventilate like this I will say that most newer anesthesiologists will not do this secondary to the increased time spent in the ICU during training. There is an article that I know well 😉 that was published a few years ago which showed that in a large academic center the average Vt was close to 9ml/kg, interestingly when looked at overtime there was a general trend with each successive year that the average tidal volumes were slowly declining and the amount of peep used increased.

I too relieve many CRNAs and even more older attendings who use tidal volumes close to 9-10ml/kg actual body weight.

 

[Idiopathic]

If you look at the tables of Peak pressures the difference, which was statistically significant, was 19 in the low tidal volume group and 20 in the high tidal volume group. Therefore this study showed that volutrauma is often under appreciated.

As far as whether people actually ventilate like this I will say that most newer anesthesiologists will not do this secondary to the increased time spent in the ICU during training. There is an article that I know well 😉 that was published a few years ago which showed that in a large academic center the average Vt was close to 9ml/kg, interestingly when looked at overtime there was a general trend with each successive year that the average tidal volumes were slowly declining and the amount of peep used increased.

I too relieve many CRNAs and even more older attendings who use tidal volumes close to 9-10ml/kg actual body weight.

wait so you are seeing people running liter tidal volumes? also, you say volutrauma here but i think postoperative atalectasis (or intraoperative atalectrauma) is a much more compelling explanation

 

[FiremedicMike]

http://www.cardiothoracicsurgery.org/content/pdf/1749-8090-5-99.pdf

http://www.ncbi.nlm.nih.gov/pubmed/22976857

👍

Thanks!

 

[WholeLottaGame7]

If you look at the tables of Peak pressures the difference, which was statistically significant, was 19 in the low tidal volume group and 20 in the high tidal volume group. Therefore this study showed that volutrauma is often under appreciated.

As far as whether people actually ventilate like this I will say that most newer anesthesiologists will not do this secondary to the increased time spent in the ICU during training. There is an article that I know well 😉 that was published a few years ago which showed that in a large academic center the average Vt was close to 9ml/kg, interestingly when looked at overtime there was a general trend with each successive year that the average tidal volumes were slowly declining and the amount of peep used increased.

I too relieve many CRNAs and even more older attendings who use tidal volumes close to 9-10ml/kg actual body weight.

I think you are right. I rarely go over 600mL for men or 500mL for women, so unless their PBW is <60kg, I almost never go over 10ml/kg. And I'd say that most other residents are similar, as well.

 

[seinfeld]

Yes to the occasional 900-1000ml Vt. But remember your 5'10" male a Vt of 438ml is 6ml/kg and a 5'6" female is 356ml. I highly doubt that the majority of practitioners routinely keep volumes that low. Hell our new Drager's default to 700ml !!!

http://www.ardsnet.org/system/files/pbwtables_2005-02-02_0.pdf

Also I will disagree with your assertion that atelectasis would be more common cause of the increased mortality seen in the higher tidal volumes. Many choose, and many editors comments I had to deal with asserted, higher tidal volumes to reduce atelectasis potential. All the articles sited about sighs illustrate the quest to mimic the normal variation in respiration which is felt to keep atelectasis to a minimum.

 

[Idiopathic]

Yes to the occasional 900-1000ml Vt. But remember your 5'10" male a Vt of 438ml is 6ml/kg and a 5'6" female is 356ml. I highly doubt that the majority of practitioners routinely keep volumes that low. Hell our new Drager's default to 700ml !!!

http://www.ardsnet.org/system/files/pbwtables_2005-02-02_0.pdf

Also I will disagree with your assertion that atelectasis would be more common cause of the increased mortality seen in the higher tidal volumes. Many choose, and many editors comments I had to deal with asserted, higher tidal volumes to reduce atelectasis potential. All the articles sited about sighs illustrate the quest to mimic the normal variation in respiration which is felt to keep atelectasis to a minimum.

maybe if you keep the PEEP constant then you will have less atalectasis with Tv of 8cc/kg as opposed to 6cc/kg, but if you have no PEEP in one arm, that group will almost certainly have more atalectasis, predisposing to hypoxemia, pneumonia, etc. Also, the study group performed recruitment maneuvers well demonstrated to prevent atalectasis, as well as adding PEEP. to me, atalectrauma is more likely than volutrauma/barotrauma to be the pathophysiologic mechanism behind the worse outcomes.

certainly you cant make the case that the higher Tv group under general anesthesia with no PEEP and no recruitment maneuvers had less atalectasis?

 

[bkell101]

This is a very interesting discusssion.

I am a ca1 and was just in he OR with a senior resident. Patient had sats 90-92, he performed recruitment maneuver, sats came up. He says "pt has atelectasis, ill also turn up the tv from 600 to 700".

I google searched and came across articles saying that atelectasis as determined by imaging in a low tv group vs high tv group are the same. This tells me that it is the peep and not tidal volume that is preventing the atelectasis, is that correct? 6cc/kg tv strategy i would assume does not have higher incidence of atelectasis correct?

 

[bkell101]

Also, in reference to he high airways pressures being the detrimental source to the lung...i was doing some reading on ards last year...on the pulm cc org website i remember coming across an article showing that low tv strategy had improved outcomes independent of the airway pressure. I remeber the take home message being to adhere to the low tv strategy even if the airway pressures arent high. I will have to look for this article.

 

[Idiopathic]

This is a very interesting discusssion.

I am a ca1 and was just in he OR with a senior resident. Patient had sats 90-92, he performed recruitment maneuver, sats came up. He says "pt has atelectasis, ill also turn up the tv from 600 to 700".

I google searched and came across articles saying that atelectasis as determined by imaging in a low tv group vs high tv group are the same. This tells me that it is the peep and not tidal volume that is preventing the atelectasis, is that correct? 6cc/kg tv strategy i would assume does not have higher incidence of atelectasis correct?

i think thats what i said. recruitment maneuvers immediately after intubation have been shown to prevent atalectasis when combined with PEEP versus just PEEP alone. i think there is some data about larger tidal volumes preventing atalectasis when combined with PEEP (as opposed to EITHER larger tidal volumes OR PEEP)

The atalectasis that you can prevent or affect happens at the end of the breathing cycle, so it only makes sense to increase PEEP, as long as the patient can tolerate it hemodynamically, as opposed to going to supranormal tidal volumes (not that 700 is that high)

 

[Idiopathic]

Also, in reference to he high airways pressures being the detrimental source to the lung...i was doing some reading on ards last year...on the pulm cc org website i remember coming across an article showing that low tv strategy had improved outcomes independent of the airway pressure. I remeber the take home message being to adhere to the low tv strategy even if the airway pressures arent high. I will have to look for this article.

thats what this study is saying as well. However there is also evidence that treating patients with lung protective strategies can increase the risk of ventilator induced lung injury when they dont have ARDS

 

[bkell101]

So there is some data to support large tv + peep > peep ( in terms of preventing atelectasis ) ? .this makes me think that larger tidal volumes protective against atelectasis....but an article I was reading compared 6cc/kg to 10 cc/kg and found similar rates of atelectasis....maybe you need even larger Tv's?

I seem to remember somebody explaining to me that delivering a large tv to a lung does not help atelectasis because the collapsed lung has higher resistance to flow and is less compliant than the already open areas which makes the large delivered tv unevenly distributed (favoring he non atelectatic lung). In essence you're just sending more volume to the already open alveoli. ....now I could be totally wrong because I get these things mixed up all the time...maybe vent can chime in.

 

[BLADEMDA]

So there is some data to support large tv + peep > peep ( in terms of preventing atelectasis ) ? .this makes me think that larger tidal volumes protective against atelectasis....but an article I was reading compared 6cc/kg to 10 cc/kg and found similar rates of atelectasis....maybe you need even larger Tv's?

I seem to remember somebody explaining to me that delivering a large tv to a lung does not help atelectasis because the collapsed lung has higher resistance to flow and is less compliant than the already open areas which makes the large delivered tv unevenly distributed (favoring he non atelectatic lung). In essence you're just sending more volume to the already open alveoli. ....now I could be totally wrong because I get these things mixed up all the time...maybe vent can chime in.

There is no need to exceed 8 ml/kg. I use 7 ml/kg (Predicted body weight) routinely with a Peep of 5. After this latest article I will increase peep to 6 on my low risk groups and use 8 (up to 12) on my higher risk groups. The key is to dial up the Peep with recruitment maneuvers. Tidal Volumes greater than 8-9 ml/kg are unnecessary and potentially harmful.

Again, low tidal volumes without peep and Recruitment maneuvers are no better than traditional ventilation techniques with 10-12 ml/kg.

The higher the overall risk score the more likely that lung protection strategies (low tidal volume, PEEP and Recruitment maneuvers) will be in reducing the incidence of postoperative pulmonary complications.


http://www.ncbi.nlm.nih.gov/pubmed/11712875

Patients were divided into five risk classes by using risk index scores. Pneumonia rates were 0.2% among those with 0 to 15 risk points, 1.2% for those with 16 to 25 risk points, 4.0% for those with 26 to 40 risk points, 9.4% for those with 41 to 55 risk points, and 15.3% for those with more than 55 risk points. The C-statistic was 0.805 for the development cohort and 0.817 for the validation cohort.

CONCLUSIONS:

The postoperative pneumonia risk index identifies patients at risk for postoperative pneumonia and may be useful in guiding perioperative respiratory care.

 

[BLADEMDA]

Let me explain this concept in simple language.

Risk stratify your operating room patients. Those at level 1 are at low risk of pulmonary complications so your ventilation strategy isn't likely to matter much.

Those at risk level 2 are likely to see some benefit or risk reduction by employing the low tidal, peep and recruitment maneuver strategy as described in this thread.

But, those patents at risk level 3 and higher should definitely get the lung protection technique as described in the articles listed in this thread. That means tidal volumes should NOT exceed 8 ml/kg and recruitment maneuvers employed right after intubation and throughout the Case. In addition, peep shoud be used throughout the operation at a minimum level of 6; but, a minimum peep level of 8-10 appears to be preferable in these higher risk groups if patient hemodynamics permit. Also, since the vast majority of us don't utilize transpulmonary pressure the literature supports trying to keep the plateau pressure below 30cm h20 if possible (but I would go higher on obese patients, interstitial lung disease, etc if needed).