Lung protective/injurious ventilation

[sluggs]

I know ARDS NET/Low tidal volumes for "lung protection", but what do people think about other modes of ventilation for lung protection. For example, is pressure control, with limited plats "lung protective"-- let's say you have a patient on AC/PC 12/5 and the patient is pulling large tidal volumes because he/she has compliant lungs? Is there any doubt that APRV with a Phigh 25 or less is as "protective" as low volumke ventilation?
We have an ongoing debate about this where I work, with one camp focusing on "volume" in any mode and another focusing on plats.
Basically, if you are using a mode besides volume control (ie pressure control or APRV) di you worry about volumes?
Thanks for any thoughts!

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[Hernandez]

Yes you should worry. And when I titrate these other modalities, I still titrate the pressures to limit the volumes. There was a point-conterpoint in chest last year on this topic.

If you look at the sub group analysis of the ARDSNet data, even those with low plat pressures with high tidal volumes had worse outcomes than those with low plat and low TV

 

[sluggs]

I read that article, but weren't all the patients studied being ventilated with volume AC as opposed to a pressure control mode?

 

[Hernandez]

I read that article, but weren't all the patients studied being ventilated with volume AC as opposed to a pressure control mode?

The take away point I think from the sub group analysis is that it isn't JUST lowering pressers that improves out comes. There are many papers that talk about volutrama.

Read the chest point conterpoint from last year on the related topic

 

[VentdependenT]

low volume is key. in severe ards the pt shouldnt have compliant lungs and thus shouldnt pull supraARDSnet recommended TV in cc/kg IBW. I rarely use pressure control in these pts but it has its place if you know what your doing.

Low TV is #1 priority
I prefer high fio2 in mild ards vs High peep strat in mod to severe.
High peep rocks lungs all on its own (as do "high" tidals)
paralyse to hit your TV goals if you must

 

[proman]

This is my concern with APRV. Some patients get incredibly high tidal volumes (like over 10cc/kg) yet the proponents of the mode say that's not injurious. I use low tidal volume, high PEEP. I don't think the delivery really matters (pressure control vs volume control) but as far as I know there's no data to indicate otherwise. I'm really looking forward to the PRESSURE trial (APRV vs ADRSnet). My hospital has some very strong advocates for APRV, almost a cult like following.

 

[Hernandez]

This is my concern with APRV. Some patients get incredibly high tidal volumes (like over 10cc/kg) yet the proponents of the mode say that's not injurious. I use low tidal volume, high PEEP. I don't think the delivery really matters (pressure control vs volume control) but as far as I know there's no data to indicate otherwise. I'm really looking forward to the PRESSURE trial (APRV vs ADRSnet). My hospital has some very strong advocates for APRV, almost a cult like following.

I'd also advocate people reading this point/counterpoint debate

The oscillate trial used an ARDSNet based stratagy except with PCAV being their mode of choice, and I'm fairly sure they still titrate TV to ~6mL/kg

After the initial RM, RTs initiate CV with the following settings:
• FiO2 1.0;
• PEEP 20 cm H2O;
• Mode: Pressure control;
• Vt = 6 ml/kg PBW;
• PPLAT ≤ 35 cm H2O
• Inspiratory to expiratory (I:E) ratio 1:1 to 1:3, avoiding autoPEEP
• Respiratory rate set to match previous minute ventilation to maximum of 35 bpm
At initiation of the CV strategy, target a driving pressure to achieve an inspired Vt of 6 ml/kg predicted body weight (PBW) and a PPLAT ≤ 35 cm H2O. This adjustment may occur over a period of a few minutes to a couple of hours, depending upon the baseline Vt and the ability of the patient to tolerate sudden changes. In keeping with routine clinical practices, an arterial blood gas should be drawn within 1-2 hours of transitioning onto the study protocol to assess both oxygenation and ventilation.

5.3. Ventilator Mode
Pressure Control mode is the default mode for patients assigned to the CV strategy. Strict Volume Control, other Volume Control modes [including Pressure-Regulated Volume Control (Siemens, Viasys), CMV with Autoflow (Dräger), VC+ (Puritan Bennett), PCV-VG (GE)], or Pressure Support (without tubecompensation) may be used if patients and clinicians are more comfortable. Airway Pressure Release Ventilation (or Bi-level Positive Airway Pressure), and Synchronised Intermittent Mandatory Ventilation (SIMV, or IMV) may not be used. The same limits to Pplat and Vt apply regardless of ventilator mode.​

 

[Bostonredsox]

I'd also advocate people reading this point/counterpoint debate

The oscillate trial used an ARDSNet based stratagy except with PCAV being their mode of choice, and I'm fairly sure they still titrate TV to ~6mL/kg

After the initial RM, RTs initiate CV with the following settings:
• FiO2 1.0;
• PEEP 20 cm H2O;
• Mode: Pressure control;
• Vt = 6 ml/kg PBW;
• PPLAT ≤ 35 cm H2O
• Inspiratory to expiratory (I:E) ratio 1:1 to 1:3, avoiding autoPEEP
• Respiratory rate set to match previous minute ventilation to maximum of 35 bpm
At initiation of the CV strategy, target a driving pressure to achieve an inspired Vt of 6 ml/kg predicted body weight (PBW) and a PPLAT ≤ 35 cm H2O. This adjustment may occur over a period of a few minutes to a couple of hours, depending upon the baseline Vt and the ability of the patient to tolerate sudden changes. In keeping with routine clinical practices, an arterial blood gas should be drawn within 1-2 hours of transitioning onto the study protocol to assess both oxygenation and ventilation.

5.3. Ventilator Mode
Pressure Control mode is the default mode for patients assigned to the CV strategy. Strict Volume Control, other Volume Control modes [including Pressure-Regulated Volume Control (Siemens, Viasys), CMV with Autoflow (Dräger), VC+ (Puritan Bennett), PCV-VG (GE)], or Pressure Support (without tubecompensation) may be used if patients and clinicians are more comfortable. Airway Pressure Release Ventilation (or Bi-level Positive Airway Pressure), and Synchronised Intermittent Mandatory Ventilation (SIMV, or IMV) may not be used. The same limits to Pplat and Vt apply regardless of ventilator mode.​

Read it. Was a good dialogue. Makes quite a bit of sense to me. I use VC low tidal volumes for my ARDS patients and I have to agree with Dr. Mac, I do it mainly because I do not have alot of comfortability with PC in this patient population as of yet. The reasons for doing VC and PC are both well defended by the two of them and what I took from this dialogue is that there is no established, inherent benefit to one vs the other. Each as their own 'situational advantadges' if-you-will, but for a face-value, use this everytime idea, one is not superior to the other. It is worth noting as mentioned that the major ARDSnet trials used VC-low Tidal strategies so technically PC mode is not as well demonstrated from a pure trial perspective but if we were extrapolating the data from institutions that are using PC more frequently for their ARDS patients, my guess is the outcomes will not vary.