Author: societymechanicalventilation

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Multi Modal Monitoring (MMM) during mechanical ventilation

Since the inception of mechanical ventilation and for many decades we depended on numbers like tidal volumes, pressures, flow and monitoring gas exchange to monitor and treat patients on mechanical ventilators. Clearly those are not enough.

Our colleagues in the neuro intensive care have beaten us to the concept of multimodal monitoring to get a complete understanding of the brain function (blood flow, ICP, brain oxygenation, electrical status, etc.) Now it is our turn to use the same concept for patients on mechanical ventilation.

The interactions between the ventilator and the lungs, and between the ventilator and other organs, and between the lungs and other organs are very complex and our understanding of the connection pathways and ways of injury that we can create is still evolving and thus we need to look at the issue from multiple different sides and planes.

Though we are finally recognizing Ventilator Induced Lung Injury and its very harmful many negative effects, we are still scratching the surface on what cause it, how to recognize it and how to prevent it (if we ever will be that’s the question).

Goes without saying that monitoring alone even if perfect and complete (we are not there by long shot) is not enough and useless without correct interpretations and actions (the famous example is the poor Pulmonary Artery Catheter that got blamed for not improving or even worsening mortality just because it was inserted, sad story).

Anyway, let’s stick with traditional and rising nontraditional monitoring for now with the understanding that each monitoring technique has its benefits and shortcomings.

Traditional

– Ventilator: the ventilator waveforms give wealth of information about mechanics, patient ventilator interactions (PVI), measuring energy and power from the ventilator, way beyond this blog and the first line of monitoring

– Gas exchange: tell a piece of the story though shouldn’t be the only goal we seek

– Imaging: traditional imaging with x-rays, CT, US also provide a piece of the puzzle

– Hemodynamics of course goes without saying

Nontraditional

– Esophageal balloon: additional old but gold tool that gives us more information about the other side about the lung and the chest wall mechanics separately, transpulmonary pressures, setting PEEP, PVI, etc. Its use is very slowly rising but in personal opinion should be a routine monitoring tool in my opinion

– EIT: rising technology that is actually pretty old from the 70s but finally making its presence and benefits felt at the bedside from measuring volume, blood flow distribution and thus V/Q would be an integral part of future monitoring.

– Volumetric capnometry: another oldy but goody that adds lots of information like dead space, VCO2, and again should be a routine monitoring technique.

– FRC: some ventilators are capable of measuring the FRC which might be helpful as a monitoring technique.

– Evolving technologies (measurements of stress, strain, tidal volume distribution, etc.)

– AI driven closed-loop systems, love it or hate it, its reality and will be there sooner than you think. It will be capable of better instantaneous interpretation of data from different monitoring and immediate action (if you ask me, I love it).

Think of the whole process as a symphony, the clinician is the conductor and all the monitoring are the musicians that play different tunes and have to work in harmony to produce a beautiful music piece.  So how we will be better conductors and incorporate and use all the available information from the existing and the new coming ones to improve our outcomes will be challenge but we can do it friends.   

Advanced monitoring during mechanical ventilation

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Which ventilator should I buy ?

We get that important question frequently, but If you want me to tell you a specific brand and model, sorry I mislead you.

When it comes to a decision to buy a ventilator or multiple ventilators, it is a really tough decision with so many brands, models with different capabilities, modes and of course prices.

But one thing for sure, they are not all the same.

I encourage you to read this article: “Decision analysis for large capital purchases: how to buy a ventilator”

I welcome your feedback and comments on any other important factors that I might have skipped.

So what factors are involved ?

Price/Budget

Let’s start with the easy/difficult one. Price and budget are very important, but as my mother used to tell me “You get what you paid for”

Of course price/budget could restraint you but trust me it should not be the only decisive point.

Cost Efficiency

Initial Cost: Balance between features, brand reputation, and cost.

Operating Costs: Include consumables (filters, tubing), maintenance, software updates, and licensing fees.

Longevity: Consider the lifespan of the device and the potential need for future upgrades.

Capabilities

I always say: a fancy expensive car and a working 2nd hand old car will take you from one point to the other, but others will tell me it wouldn’t be the same journey.

Depending on your needs, you should consider a ventilator with neonatal, pediatric, adult capabilities (3 in 1). Having high flow oxygen therapy, non-invasive capabilities are a great plus (another 3 in 1)

Integrated humidification and options for delivering aerosolized medication is beneficial too.

Technological Features

Finally the exciting stuff

Modes: When it comes to modes, most of ventilators have the base set point modes like volume-control, pressure-control, pressure support, SIMV, APRV, etc. Few others have their own automated or smart modes. Evaluate your needs and consider their benefits. Just please don’t get confused by names of different modes names that sound fancy but they are basic modes that might be available in all other ventilators.

Monitoring: don’t disregard monitoring, in my opinion it is the most important feature of a ventilator. Now most of ventilators have airway pressure, flow, volume – time and loops to monitor. Advanced monitoring like esophageal pressure, transpulmonary pressure vs time and volume curves, volumetric capnometry, and maybe one day Electrical Impedance Tomography (EIT) integrated in the ventilator.

Accuracy of delivered flow, volume and pressures are very important especially in neonates or pediatrics. FDA and ISO have standards of usually +/- 5 – 10% deviation which could be significant in those patients’ population.

Connectivity: Ability to interface with central monitoring systems and other hospital technology for remote monitoring and data collection.

Durability and Reliability

Build Quality: The robustness and durability for long-term use in different environments (ICU, transport, MRI).

Maintenance Needs: Evaluate how frequently maintenance is required and the ease of servicing.

Battery Life and Backup: adequate battery life for power outages or patient transport.

Ease of Use and Usability

User Interface: A clear and non confusing intuitive touch-screen interface for quick adjustments and monitoring

Workflow Integration: Easy integration into existing workflows, including charting and electronic health record (EHR) systems.

Mobility and Portability: If it needs to be moved frequently, consider its weight, mobility (e.g., battery life for transport), and size.

Training and Support: Availability of comprehensive training for staff and 24/7 support services from the manufacturer.

Brand Reputation and Reviews

Manufacturer Reputation: Consider the track record and reputation of the manufacturer for quality, reliability, and service.

User Reviews: Feedback from healthcare facilities and clinicians using the same or similar models can provide valuable insights.

At the end, good luck and remember so far for the most part, clinicians control the machine not the machine control the clinician

At least for the time being

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Which one are you ?

We all seen it, some clinicians are very enthusiastic about mechanical ventilation spending time to watch and analyze what is going on, while others who come do their routine round, check some nobs and go chart. Why is that ? and does it make a difference?

This is all speculative and not studied to my knowledge

A clinician who works with ventilators and genuinely loves the field might display several differences compared to those who don’t have the same passion for it:

Deep Engagement and Curiosity

Passionate Clinician: They are likely to be more deeply engaged in their work, continually seeking to understand the nuances of mechanical ventilation. They might stay updated on the latest advancements, research, and best practices in the field. This curiosity drives them to explore new technologies and methodologies with enthusiasm.

Less Passionate Clinician: They may still be competent but might approach the work as a routine task rather than an area of deep interest. They might not actively seek out new knowledge or innovations unless required.

Problem-Solving and Innovation

Passionate Clinician: They are more likely to take initiative in solving complex cases, perhaps coming up with innovative solutions or custom settings for patients with unique needs. Their love for the field might push them to think creatively and go the extra mile.

Less Passionate Clinician: While they may still solve problems effectively, they might rely more on established protocols and may be less inclined to explore unconventional approaches.

Patience and Persistence

Passionate Clinician: They might exhibit greater patience and persistence when dealing with challenging cases or troubleshooting ventilator issues. Their love for the work sustains them through difficult times, making them more resilient in the face of setbacks.

Less Passionate Clinician: They might prefer to stick to what they know works, potentially becoming frustrated more quickly if a situation doesn’t resolve easily.

Education and Mentorship

Passionate Clinician: They may be more inclined to educate others, sharing their enthusiasm and knowledge with colleagues, students, or trainees. They might take on a mentorship role, helping to cultivate the next generation of ventilator specialists.

Less Passionate Clinician: They might still teach but might not do so with the same level of enthusiasm or depth, possibly focusing more on the basics rather than inspiring others with the broader possibilities within the field.

Emotional Connection

Passionate Clinician: Their love for ventilators might translate into a strong emotional connection with their work, leading to a greater sense of fulfillment and satisfaction. This could also make them more attuned to the emotional aspects of patient care, as they see their work as a vital, life-sustaining effort.

Less Passionate Clinician: They might approach the work more clinically and objectively, focusing on the technical aspects without as much emotional investment. This can still be effective but might lack the same depth of personal satisfaction.

Overall, the key difference lies in the level of enthusiasm and commitment to the specific field of ventilators. A clinician who loves working with ventilators is likely to be more proactive, innovative, and emotionally invested in their work, which can positively impact both patient outcomes and their personal job satisfaction.

So, lets get the enthusiasm and energy again, but how ?

There is no pill for that unfortunately

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The High vs. Low PEEP Debate in Mechanical Ventilation: Are We Just Blowing Hot Air?

In the world of mechanical ventilation, few topics spark as much debate—and as many eye rolls—as the discussion around PEEP settings. Yes, that’s right, we’re talking about Positive End-Expiratory Pressure, the setting that keeps our patients’ lungs open, their oxygen levels up, and our Journal and conferences locked in never-ending debates. But while some clinicians treat this debate like it’s a life-and-death matter (because, well, it kind of is), let’s take a moment to breathe deeply and look at the High vs. Low PEEP controversy with a bit of humor. After all, who says we can’t laugh at ourselves since we really don’t know

The High PEEP Advocates: More is More, Right?

If you’ve ever met a High PEEP enthusiast, you know they’re a passionate bunch. For them, cranking up the PEEP is akin to turning up the volume on your favorite song—louder is always better. They argue that higher PEEP levels keep the alveoli open, improve oxygenation, and prevent the dreaded atelectasis from rearing its ugly head. And, in many cases, they’re right. For patients with severe ARDS, a higher PEEP can indeed make the difference between life and death.

But let’s be honest—High PEEP proponents can sometimes take it a bit too far. It’s as if they believe that more pressure will magically solve every problem, much like the guy at the gym who thinks adding more weight to the bar will instantly turn him into the Hulk. But here’s the thing: while High PEEP can be a powerful tool, it’s not a one-size-fits-all solution. There are risks, like barotrauma and hypotension, that can make this approach a double-edged sword. So, while we applaud their enthusiasm, maybe it’s time to dial it back just a notch. Not every patient needs to feel like they’re in a wind tunnel.

The Low PEEP Loyalists: Less is More (And Also Safer)

On the other side of the battlefield, we have the Low PEEP loyalists—those who believe that when it comes to PEEP, less is definitely more. For them, the idea of pumping high pressures into delicate lung tissue is as appealing as putting pineapple on pizza (a practice that sparks its own set of heated debates: The Hawaiians ruined the Pizza according to Anger from Inside Out)).

Low PEEP advocates argue that keeping PEEP low reduces the risk of barotrauma, minimizes the potential for hemodynamic instability, and generally makes life easier for the lungs. And they’ve got sorta a little point.

Low PEEP settings are often preferred for patients with conditions like COPD or when there’s a concern about blood pressure dropping faster than a Wi-Fi signal during a Zoom meeting. The Low PEEP approach is all about caution, careful monitoring, and avoiding the pitfalls of too much pressure. It’s the respiratory equivalent of the “minimalist” movement—why add more when less will do just fine?

The Gray Area: Why the Debate is Far From Over

Of course, as with most things in life, the truth lies somewhere in the middle. The High vs. Low PEEP debate isn’t black and white—it’s more like fifty shades of gray, each with its own clinical nuances. Patient variability, underlying conditions, and real-time monitoring mean that what works for one patient might not work for another. It’s like trying to find the perfect temperature for your shower—everyone’s got their own sweet spot.

But wait, how about the science, the prospective studies, the meta analysis, the Biblical societies guidelines, the PEEP-FiO2 tables. Those solved the problem and ended the debate right ? I’ll leave you to laugh at that for a little bit…..

The reality is that the High vs. Low PEEP debate is as much about philosophy as it is about physiology. Some clinicians are risk-takers, willing to push boundaries for the sake of better oxygenation. Others prefer a more conservative approach, focusing on steady, reliable outcomes. And both sides have valid points. So, while we may never fully resolve the debate, it’s important to keep the conversation going. Because in the end, what really matters is doing what’s best for the patient in front of us—even if it means admitting that maybe, just maybe, we’re all just blowing a little hot air.

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Indociated (Induced-Associated)

Don’t bother for a definition, it’s a made up hybrid word, may be a neologisms in the making

The mechanical ventilation literature is jammed with those 2 acronyms VALI (Ventilator Associated Lung Injury) & VILI (Ventilator Induced Lung Injury)

Is there a difference between them ? Are they synonyms ?

If they are the same then why use different terms for the same meaning ? and if they are different, how to differentiate between them ?

is it “You Say Tomato, I say Tomato”

To add to the confusion, some authorities decided to create the term VAE (Ventilator Associated Events), a garbage term that indicates that the condition is worse denoted by the increase in FiO2 or PEEP just to penalize hospitals for it. What they don’t know is sometimes you need to increase PEEP even if FiO2 is 30-40% just to prevent lung injury (whole different lond discussion). Anyway lets go back to VILI-VALI

If you look at the definitions:

VALI: implies lung injury that can happen while the patient is on mechanical ventilation, it could be directly caused by the ventilator (actually our settings, let’s be honest) or just a progression of the disease process that lead the patient to be on the ventilator in the first place.

VILI: is a subset of VALI which implies and incriminates the ventilator (again our settings for the most part) to the progressive worsening of the lung mechanics.

Can we differentiate between both conditions clinically:

maybe but mostly not, the easy one is barotrauma like pneumothorax, pneumomediastinum, but how about all the other terms. volutrauma, atelectrauma, ergotrauma, rheotrauma, biotrauma, ergotrauma ? maybe CT scans, EIT, US can be suggestive but not diagnostic

So far there has been no clinical golden marker or bio-marker that can differentiate or incriminate the ventilator (there are many biomarkers used in research labs and the literature) in the worsening of the patient condition or for gosh sake even VAP (Ventilator Associated Pneumonia) remains a pathological diagnosis as a gold standard despite all the studies, definitions, labs, cultures, etc.

So, lets not fool ourselves and pretend to know what we are talking about when we use one term over the other, or argue which one is correct and which one is incorrect and maybe use the made up term “Indociated” till we really know.

Hopefully, one day we will know

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AI in Mechanical Ventilation: Friend or Foe ?

Clinicians may understandably have concerns about the impact of AI in medicine. While AI has the potential to revolutionize healthcare by improving diagnostics, treatment plans, and patient outcomes, it is unlikely to completely replace clinicians “in the near future”. Instead, AI is more likely to augment their skills and support their decision-making processes.

Artificial Intelligence (AI) can be applied during mechanical ventilation to improve patient outcomes and reduce healthcare costs. AI algorithms can be used to analyze patient data to dynamically adjust ventilator settings and predict patient needs. This allows for more precise control of ventilation, reducing the risk of patient harm and improving treatment efficiency. Additionally, AI can assist in detecting and diagnosing respiratory problems, such as VAP, VILI earlier and more accurately. AI in mechanical ventilation is a rapidly growing field with the potential to significantly impact patient care.

The future of AI in mechanical ventilation looks promising, with increasing potential for further advancements and wider adoption in clinical practice. Here are a few areas where AI is expected to make a significant impact in the future:

– Predictive analytics: AI algorithms will become more sophisticated and able to provide real-time predictions of patient needs, allowing for more proactive and personalized treatment.

– Automated decision making: AI-powered systems will increasingly be able to make automated decisions, such as adjusting ventilator settings, without human intervention, thus reducing the risk of human error.

– Improved patient outcomes: As AI becomes more widely used in mechanical ventilation, it is expected to lead to improved patient outcomes through more precise and efficient treatment.

– Cost savings: The use of AI in mechanical ventilation is expected to lead to cost savings for healthcare organizations by reducing the need for manual intervention and reducing the risk of patient harm.

– Overall, the future of AI in mechanical ventilation is exciting, and it is likely that we will see significant advancements and improvements in patient care in the coming years.

We need to be vigilant assessing, monitoring and learning the impact and the hypothetical benefits or harms of AI during mechanical ventilation in the ICU and in health care in general.

(This blog is written with some assistance from ChatGPT/Bard)

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Should we automate PEEP ?

Before we dig in this tough topic, let’s agree or disagree that that there is nothing called optimal or best PEEP. Regardless of the PEEP level used, there will be overdistention in some areas, some under distention and collapse in other areas of the lungs.

Here are some points to keep in mind when we talk PEEP

  • The normal and the diseased lungs are markedly heterogenic with each lobule or even each of the approximately 500 million alveoli have their own mechanics
  • The pleural pressures are not uniform and thus the trans-alveolar pressures will vary depending on the location of the alveoli
  • Not all Lungs especially ARDS are recruitable
  • “Not all ARDS are the same” but studies don’t differentiate ARDS phenotypes
  • “PEEP does not recruit, rather prevents derecruitment”
  • We don’t have much agreements in the literature on how to set PEEP or if PEEP affect mortality
  • The respiratory mechanics change frequently, even between breaths to breaths but we don’t change the PEEP frequently enough, so what was good 10 minutes ago might not be good now

Why automate PEEP or let the machine adjust PEEP?

Simple answer, because we honestly don’t know how despite 50 years of research, and we can’t do it continuously or be at the bedside all the time while the respiratory mechanics are continuously changing

What are the benefits?

  • To minimize the over and under distention of one level of PEEP
  • The ventilator can be consistent on the way it adjust the PEEP per specific algorithms

Are there any modes that currently automate PEEP?

Yes, INTELLiVENT‑ASV from Hamilton was the first mode to automate PEEP, among all other parameters of ventilation and proved to be an effective mode of ventilation from intubation to extubation. However the algorithms used is the ARDSnet PEEP-FiO2 table, though this table have been used for the last 2 decades, it is very non physiological and does not take in account the lung recruitability or if the higher PEEP could be beneficial or harmful.

PMLV (Programmed Multi Level Ventilation) uses alternating 2 or 3 levels of PEEP but they are set by the clinicians

How can the ventilator choose PEEP level ?

As mentioned above, there is no agreement in the literature on the best method of setting PEEP. There are so many different physiologic ways, lets name some:

  • Pressure Volume curve (Hysteresis of the curve, Lower inflection point of the inspiratory limb, point of maximal curvature on the expiratory limb)
  • Incremental or decremental PEEP trial
  • Best compliance and lowest driving / tidal pressure
  • Expiratory time constant during different PEEP levels
  • Esophageal balloon monitoring and transpulmonary pressures
  • Volumetric capnometry (Dead space and VCO2)
  • Electrical Impedance Tomography (EIT) signals of over and under inflation during different PEEP levels
  • According to measured FRC

Now, the next question is: can the ventilator do those maneuvers by itself? when ? and how often?

Currently most of those maneuvers, signals, information (except EIT, though the ventilator can get the signal from EIT monitor) are measured by the new generation ventilators. The ventilator would know when respiratory compliance changes (it measures it breath by breath)

As a computer, the ventilator can be programed to do any of those maneuvers independently, and at a programmed intervals according to a specific algorithm and through feedback system can change the current PEEP settings up or down.

Goes without saying, that this would be controversial and needs more studying and research, but for now its just a blog with some ideas

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High Flow Oxygen Therapy (HFOT): We need more

No doubt, HFOT has set foot as an important therapy in the field of respiratory failure and became an important tool in the armamentarium of therapies available to hopefully avoid invasive mechanical ventilation.  

The mechanisms of its action and physiologic beneficial effects have been described in multiple reviews and studies. 

Isn’t that enough? No, let’s be greedy and demand more.

More of what? 

  • Monitoring: The field of respiratory failure relies heavily on monitoring which helps tailor the therapy to the patient’s needs. Yes, we can monitor the patient’s clinical condition and oxygenation but  

– How about the amount of positive pressure created with therapy? This is a major path for improving oxygenation with HFOT. We only hypothesize the number of pressures based on simulator studies but not in real patients. 

– How about the end tidal CO2 (capnometry): it has been described but how accurate is the information which is crucial to calculate the dead space during therapy. 

– Monitoring of the patient’s own inspiratory flow so we can match the delivered flow instead of empirically delivering set flow 

  • Modes of delivery: conventionally, HFOT is being delivered with a special nasal cannula, but has been tried through tracheostomy tubes and even Non Invasive masks, studies are needed to test the differences between different delivery modalities.

Humidification: is essential during HFOT to avoid drying mucosa, bleeding and improve turbulent flow. How much humidification is needed during such high flow? If airway humidification is too excessive, theoretically it will reduce the Alveolar Partial Pressure of Oxygen (PAO2) which can worsen hypoxia.  

Are all devices similar?: HFOT are offered on a stand alone devices but are also incorporated on many critical care ventilators. Are all the same? Possibly not. We need more studies comparing the same therapy on different devices that might help us choose the more superior one and improve the inferior ones.

  • Smart (Adaptive) machines: similar to closed-loop modes of mechanical ventilation that have the capabilities and autonomy (within limits) to adjust pressures, flow, minute ventilation depending on the respiratory mechanics, there is a need for similar HFOT devices.  

So, what is the solution and how? 

Artificial intelligence (AI): incorporation of AI has the possibility to achieve: 

  1. Flow rate optimization: AI algorithms can analyze patient data, such as oxygen saturation levels, lung function, and vital signs, to determine the optimal flow rate for high flow oxygen therapy. 
  1. Monitoring and alerting: AI-powered monitoring systems can constantly monitor patient data and send alerts to healthcare providers if any abnormalities are detected. 
  1. Personalization: AI can be used to analyze patient data and make personalized recommendations for high flow oxygen therapy. For example, an AI algorithm can analyze a patient’s medical history, current condition, and response to therapy to determine the optimal flow rate, humidity level, and other settings for the therapy. 
  1. Predictive modeling: AI-powered predictive models can be used to predict the likelihood of a patient’s condition worsening or improving. This can help healthcare providers make more informed decisions about the patient’s care and adjust the high flow oxygen therapy accordingly. 
  1. Smart devices: to my knowledge, there are some companies that are developing AI-powered devices that can deliver high flow oxygen therapy. These devices can be connected to the internet and can collect data on the patient’s respiratory status and other vital signs, which can then be analyzed by AI algorithms to adjust the therapy as needed. 

The future of how we monitor and treat patients with respiratory failure is very exciting and coming fast so watch out. 

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The missing piece: Lung regeneration therapy

Over the last couple of decades, our understanding of lung injury and the support of the injured lung has evolved significantly.

The lungs are an expansive organ with relatively fewer cells than other organs but have great ability to heal and regenerate the injured epithelial, endothelial and supporting matrix.

However, the healing process could be different in different pathologies, different acuities, different ages.

The ultimate repair of the injured lungs is through regeneration (making new cells), however through many different inflammatory and immune pathways sometimes repair (scarring/fibrosis) occurs, and in chronic lung conditions, modulation or dysregulated repair can occur leading to further worsening of lung function.

Our research focus has been mainly on supporting the injured lung till healing or improvement occurs, treating the inflammatory/infectious pathologies, and concurrently trying to minimize further lung injury.

Unfortunately, much less focus, research and investments has been allocated to the healing process. The healing process can take up to weeks or months and studies have shown that patients who survive from ARDS can still be symptomatic 6-12 months after.

Currently, our only long-term hope especially for the chronically injured failling lung is lung transplant.

Stem cell research is still considered in its infancy but there is some slow progress in identifying progenitor cells that hopefully can be used as a target for new therapies.

I hope we focus and invest in this extremely important process that might improve outcomes and lives.

From: Lucas, A., Yasa, J. and Lucas, M. (2020), Regeneration and repair in the healing lung. Clin Transl Immunol, 9: e1152.

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Indexing the Power

This is a continuation of the last blog: Mechanical Power

Over the last two decades we were stuck on targeting a certain value of tidal volume or an inspiratory pressure (tidal, driving pressure) in a hope to reduce VILI and mortality. Have we been wrong? Maybe yes, maybe it was just a step in the right direction.

We now know that it is much more than that, and the interaction between the tidal volume (strain), pressure (stress) in interaction with flow rates, inspiratory time, respiratory rate, PEEP levels all summed up in the mechanical power are all indicted contributors.

Before we repeat our previous mistakes and fall in the trap of targeting certain value of mechanical power or its components of elastic and resistive power, lets take it slow and think about it more.

We should probably consider the mechanical power in context of other factors.

We propose indexing the power to the compliance or elastance which might give more insight in this issue and for further studies to investigate.

For example Power Compliance Index:  a healthy compliant respiratory system probably will need less ventilatory power to inflate (e.g. 10 J/min / 70 mlcmH2O = 0.14), while a less compliant system will require more ventilatory power (e.g. 20 J/min / 30mlcmH2O = 0.66).

Other denominators to consider indexing are FRC, lung weight, lung water, IBW.

I will repost two of my previous questions:

– Is the same energy or power exerted on a healthy or an already injured lung can exert the same effects or potential damage? Which one can withstand more energy?

There are some evidence that the healthy lung is more prone to injury than the already injured lung?

Conceptually makes more sense is to consider the forces acting on the lung itself not the whole Chest wall. Can the ventilator hurt the chest wall, probably not the ribs or skeletal muscles but theoretically the diaphragm) i.e. maybe we really need to concentrate on the trans-pulmonary mechanical power and index it also on the lung compliance. Which brings the role of the esophageal balloon manometry and the debate for its use.

Lastly for now at least, how about the active patient work? Is the force to pull the air in by the patient against the force to push the air in by the ventilator do they have the same effect? Do they ameliorate and counterbalance each other or amplify the problem? There is ample of evidence that spontaneous or partial breathing might be beneficiary but on the other hand there is also benefits that muscle relaxants or paralytics might be protective.

More questions and hopefully more answers will come but please let’s not jump to premature conclusions about the topic blindly folded and repeat our mistakes of the past but learn from them.

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