Are the "Vent Protocols" causing harm in COVID?

Here is a response to Deborah Mayo's excellent blog post posing this question.  I encourage you to first read her post.  Here, I explicate my view of the problems that are raised in that post.  I don't have time for a lot of hot links and stuff, so post your specific comments below.

There is a lot correct here, and @learnfromerror has done a far better job of summarizing it than I could ever explain a normal distribution. But there is a lot missing, because the commentators have not gotten to the crux, and have made slogans for their points that are distracting and misguided if not totallly incorrect.

First, and this is very very important, is that *there are NO protocols for intubation* as the NYC ER doctor suggests. I talk about that on my other blog a lot. ARDS trials enroll patients who are *already intubated* and the criteria for that intubation are absent from the study protocols. It is assumed in an ARDS study that if you are intubated, you were appropriately intubated. Therefore, there is no “problem with the protocols” for ventilators, there is a glaring and longstanding problem with the criteria (or the absence of criteria) for intubating patients. Is it blood gas values, or vital signs, or physical examination signs, or subjective distress or some combination? There is ZERO standardization in this area. COVID has brought this underappreciated problem to the fore.

Why is this just coming out now? Ah, that’s another crux of the problem and a reason that COVID has become a perfect storm for ventilator management. Usually, if you intubate a little old lady with influenza, even if you do it for shaky reasons, she can be extubated (tube removed) in a couple of days or a week with little harm done (or with a level of harm that we take for granted, probably mistakenly). Not so with COVID. The natural history of the disease has 2 important features that make the decision to intubate likely to culminate in a massive therapeutic misadventure: 1.) the duration of the illness is protracted, two to perhaps as long as four weeks; and 2.) the level of sedation needed to counteract the massive air hunger these patients have, for the duration they need it, is through the roof.  This problem is compounded by the mandate to use small tidal volumes which are poorly tolerated in the face of massive air hunger. So, 2 weeks after intubation, they are veritable zombies, cannot be weaned from sedatives (a prerequisite from being weaned from the ventilator), and are stuck on the vent, assuming that before this stage other complications have not set in and/or death ensued.

Another facet of the perfect storm, which I think is also the Rosetta Stone, and a key to untangling this giant mess we find ourselves in, is that this normal lung compliance that people are talking about is *the reason why* there is this so-called “silent hypoxemia” of the type mentioned by the ER doc in Mayo’s post. Failure to recognize this connection betrays a common misunderstanding of respiratory physiology (my attempt to disabuse people of these errors can be found here: https://pulmccm.org/ards-review/great-lecture-applied-respiratory-physiology/). Dyspnea is not driven by hypoxemia as much as it is by hypercarbia, which can be compensated for by hyperventilation which these patients are doing! To a person who has a firm grasp on applied respiratory physiology, this is no surprise – the patients have compliant lungs, so they don’t have workload imbalance and can sustain ventilation in the face of significant hypoxemia (which is a MINOR driver of dyspnea) very well. In sum, I am not surprised by these clinical presentations, nor am I surprised that this quagmire has allowed problems with the understanding of applied respiratory physiology to surface.

This disease is very difficult for these and many other reasons. When the choice is let a hypoxemic person who is defending her CO2 - like the little old lady the ER doc talks about - ride it out (which she can probably do for a very long time, see my tweets about sustaining very high Ve indefinitely [50% of the 15-second MVV]), versus intubating her for a marginal gain in gas exchange accompanied by a massive cost in sedation and paralysis, the choice is clear, let them ride it out, don't incur that cost.

The problem is not with the “vent protocols” the problem lies in a widespread lack of understanding of applied respiratory physiology which leads to questionable calls regarding intubation which are usually, in non-pandemic times, lost in the signal and noise of the fray. Not so with COVID – premature or unnecessary intubations precipitate a cascade of status iatrogenicus.

Limits of the Possible: Clinical Reasoning of a Harrowing Extubation

"The only way of discovering the limits of the possible is to venture a little way past them into the impossible."  -  Clark's Second Law

In prior posts here and on the Medical Evidence Blog (here, here, here, and here), I have outlined my position that the only way you can really know if a patient can breathe on their own is to let them try - a "trial of extubation".  Prediction equations get you published, but their signal to noise ratio is often poor and ignored, to patients' peril.  Indeed the reason I'm obsessed with extubation is because I think being intubated unnecessarily is one of the worst things a patient can endure, and the best thing I can do as an intensivist is identify the earliest moment when a patient can breathe on his own and extubate him.

I faced a very harrowing extubation decision recently, and I admitted to the medical students that it was the most nail-biting of my career.  But I think analyzing it, both before and after the fact can be very instructive.

DIPSHIS: Diprivan Induced Pseudo-Shock & Hypoxic Illness Syndrome

This would be a very informative case report (and it's true and unexaggerated), but I anticipate staunch editorial resistance (even sans puns), so I'll describe it here and have some fun with it.

Background:  The author has anecdotally observed for many years that so-called "septic shock" follows rather than precedes intubation and sedation.  This raises the possibility that some proportion of what we call septic (or other) shock is iatrogenic and induced by sedative agents rather than progression of the underlying disease process.

Methods:  Use of a case report as a counterfactual to the common presumption that shock occurring after intubation and sedation is consequent to the underlying disease process rather than associated medical interventions.

Results:  A 20-something man was admitted with pharyngitis, multilobar pneumonia (presumed bacterial) and pneumomediastinum (presumed from coughing).  He met criteria for sepsis with RR=40, HR=120, T=39, BP 130/70.  He was treated with antibiotics and supportive care but remained markedly tachypneic with rapid shallow respirations, despite absence of subjective respiratory distress.  A dialectic between a trainee and the attending sought to predict whether he was "tiring out" and/or "going into ARDS", but yielded equipoise/a stalemate.  A decision was made to intubate the patient and re-evaluate the following day.  After intubation, he required high doses of propofol (Diprivan) for severe agitation, and soon had a wide pulse pressure hypotension, which led to administration of several liters of fluids and initiation of a noradrenaline infusion overnight.  He was said to have "gone into shock" and "progressed to ARDS", as his oxygen requirements doubled to 80% from 40% and PEEP had been increased from 8 to 16.  The next morning, out of concern that "shock" and "ARDS" were iatrogenic complications given considerations of temporality to other interventions, sedation and vasopressors were abruptly discontinued, diuresis of 2 liters achieved, and the patient was successfully extubated and discharged from the ICU a day later.

Conclusions:  This case provides anecdotal "proof of concept" for the counterfactual that is often unseen:  Patients "go into shock" and "progress to ARDS" not in spite of treatment, but because of it.  The author terms this syndrome, in the context of Diprivan (propofol) in the ICU setting, "DIPSHIS".  The incidence of DIPSHIS is unknown and many be underestimated because of difficulty in detection fostered by cultural biases in the care of critically ill medical patients.  Anesthesiologists have long recognized DIPSHIS but have not needed to name it, because they do not label as "shock" anesthetic-induced hypotension in the operating theater - they just give some ephedrine until the patient recovers.  DIPSHIS has implications for the epidemiological and therapeutic study of "septic shock" as well as for hospital coding and billing.

Technological Crutches and Agenesis and Atrophy of Procedural Skills

This article in the New York Times describes the possibility that with increasing reliance on technology and automation, there is atrophy of human skillsets which can lead to untoward outcomes, especially when technology fails and humans have to take back the steering wheel.  One example it called upon was a crash in 2009 of an Air France jetliner that was caused by icing over of the airspeed sensors upon which the autopilot program relied.  When the autopilot failed and the pilots took over, they were confused and ill prepared, and the plane crashed into the Atlantic Ocean.

I am no general fan of romanticizing dated technology (except for the pager) such as the physical examination when superior and ubiquitous technology supercedes it.  Spending five or ten minutes flipping the patient into different contortions trying to identify a gallop or a subtle murmur seems quixotic if an echo has been ordered or the result is pending (although if this interests you as it did me, indulge yourself, its performance and ponderment reinforces the underlying physiology poignantly).  On the other hand, if a patient in the coronary care unit crumps and you cannot identify the obvious holosystolic murmur from a chordae rupture….

I am reminded specifically of certain technological crutches graduates of internal medicine and critical care training programs have come to depend upon in the past decade such as ultrasounds for the placement of central lines and performance of thoracenteses, and fiberoptic aids for endotracheal intubations.  These devices certainly have a role in both training and patient care, and I am generally familiar with the favorable data on success and complication rates, but something is certainly lost when a trainee’s or a practitioner’s efficacy is overly dependent upon use of these technological crutches.

What to do during a Code Blue on the floor when there is no ultrasound and no intravenous access?  I recall several Code Blues where I inserted a subclavian line during brief epochs when chest compressions were held, but it is not uncommon nowadays that trainees leave a critical care fellowship with no proficiency in the subclavian approach whatsoever (or worse, that they learned erroneously that the jugular approach is generally superior to the subclavian approach).  What to do when there is a Code Blue but the Glidescope is in the ER, or there is no Glidescope, the Glidescope malfunctions, or there is a Glidescope but there is also a GI bleed or profuse vomiting and no fiberoptic visibility?  How can you know how to instinctually position the head and neck for a direct view of the larynx if you have trained almost exclusively on a device that obviates a direct view of the larynx?  How do you percuss and tap a pleural effusion when there is no ultrasound available if you have learned this procedure by the “point and poke” method?

One approach to this problem is to insist that trainees learn the tried and true methods first, and resort to the technological aids only for difficult cases or those in which the simple methods have failed.  Make an attempt with the Miller 2 blade (one brief attempt) and if that fails, proceed to the Glidescope.  Identify the internal jugular using proper patient positioning and identification of anatomical landmarks and make a pass with the finder needle before resorting to the use of the ultrasound, or use the ultrasound to confirm or refute your estimation of the jugular position prior to making a pass, rather than relying on it from the get-go.  In this way, the technology can be a way to calibrate predictions and can enhance learning of the underlying basic techniques, while also bolstering proficiency in their performance, and increasing optionality in procedural approaches.

Even with widespread availability of echocardiograms, cardiologists must be able to identify basic murmurs.  If trainees are leaving their programs where 90% or more of their procedures were performed with a technological crutch or aid, they may have rude awakenings when atrophy of basic skills (or the absence of their development) becomes apparent during exigent circumstances in real world settings.