Acute Respiratory Distress Syndrome, ARDS, is a condition that occurs when fluid fills the lungs and often requires a patient to be placed on a ventilator.
Dr. Jason Mock, an Instructor in the Division of Pulmonary Diseases and Critical Care Medicine, discusses how physicians care for ARDS, how to prevent ventilator injury, and communicating with families of a patient with ARDS.
Patients that have active physical therapy in an ICU, even on a ventilator- this helps those long-term outcomes… Physical therapy early on helps fight against the long-term morbidities of muscle weakness, neurocognitive abnormalities such as memory, depression..”
– Dr. Jason Mock
Part Two: ARDS Care and Preventing Ventilator Injury
Mock: A lot is known about the initial events that cause ARDS. Much less is known about how the lung resolves injury. That’s some of what we do in the lab. Back to the patients, we know that, primarily, over the last decade and a half, the things that help patients recover and decrease mortality, are things like the ventilator and lowering those breaths that we give patients to cause less injury from the ventilator
Falk: There are several things we need to talk about. When one is intubated, on an artificial breathing machine, otherwise known as a ventilator, that process in and by itself causes lung injury. Always or sometimes?
Falk:What are the conditions in which a ventilator can actually induce more damage than providing good?
Mock: It’s an important question. Normally, when we breathe naturally, our diaphragms contract-there’s a negative pressure and air is pulled into the lungs. The ventilator does the exact opposite. We have a patient on the ventilator with a tube down their throat, and we’re forcing air in. We know from animal models that over distention, or full collapse of the lung, is injurious.
We want to have this middle ground of keeping the lung open but also not over-distending it. It’s important with how we ventilate patients on life support, the mechanical ventilator. So as not to cause either too small of a breath, or too large of a breath, and that’s caused ventilator-induced lung injury.
Falk: If ventilators are both helpful and injurious, what can you do to make sure that you as an ICU physician limit the possible damage to the patient’s lung?
Mock: There are several things that we can do. Treatment is primarily supportive, but the most beneficial and significant advance has been small breaths over time from the ventilator. That initial study came out in 2000 and it was done by either giving patients the standard breath, or half the volume. What was found was those patients that received half the volume actually had about a 9% decrease in mortality– a huge decrease. The average mortality of ARDS now ranges between 20 and 50%.
Falk: Wow. So if you give a person a diagnosis of ARDS, there’s really a mortality risk associated that’s pretty large.
Mock: Absolutely. When you look at epidemiological cohort studies, it’s estimated that in the United States there’s probably about 190,000 cases a year of ARDS, and about 75,000 deaths. That’s estimated to increase by 2030, so over 330,000 cases and 150,000 deaths, and that’s due to an aging population.
Falk: There are things then that you can do just with the ventilator by itself to decrease the mortality rate.
Mock: Yes, it’s those low tidal volumes. So every patient on a ventilator, we measure that based on your ideal body weight.
Falk: If you’re a family member or a patient with ARDS, what are the risk factors that are associated with this mortality rate? What tells you if you’re going to be in the group that will survive or not survive?
Mock: Age is probably the primary driver. If an 18-year-old comes down with viral influenza, pneumonia, their mortality is less than 20 percent. If you’re an 85-year-old person with the exact same process, your mortality is up above 50 percent. Age is primarily one.
The other is the actual etiology. It’s how we treat and care for it. So if you have sepsis or an exuberant inflammatory response, that has a higher mortality than if you had inhalational lung injury or a drug reaction or a transfusion reaction-so that’s the second. The third is the other chronic conditions the patient might have. If they’re immunocompromised, such as HIV or AIDS, or a transplant patient, their mortality is higher. If they have chronic kidney injury, or if they smoke, or chronic alcohol abuse, those are all risk factors that we see for certain etiologies increase your risk and your mortality for ARDS.
Falk: Some of those prognostic factors one has no control of. It seems like the factors one that may have control of may have to do with treatment options. What are the treatment options then that would improve the outcome for patients with ARDS?
Mock: Besides the ventilator, there are several non-ventilator therapies that very recently have been shown to improve mortality. One is neuromuscular blockers or paralytics. When we talk about putting a patient on a ventilator, we want them to be in sync with the ventilator. Because if they’re not in sync that potentially causes more ventilator injury.
Falk: You don’t want the person to fight the ventilator.
Mock: Correct. So the best way to do that is by giving them a little bit of sedation and making them comfortable. But when their injury is severe and they’re fighting the ventilator, one of the therapies that has been shown to improve mortality is actually to paralyze the patient. Keep them heavily sedated and give them a paralytic.
Falk: That’s always a terrifying thought. There you have somebody who’s on a ventilator and now you’re paralyzing them, and there’s a loved one you want to make sure that the person doesn’t feel any of that.
Mock: Absolutely, and so when I care for a patient in the ICU, and we have to reach for paralysis, I talk to the family extensively and say that they won’t remember this, that they are heavily sedated when they are paralyzed, to help the ventilator work and allow time for their lungs to recover from the injury.
Falk: Because the last thing anyone wants is a paralyzed human on a ventilator who’s wide awake, that would be terrifying. So sedation is incredibly important. What else can you do to alter treatment?
Mock: One of the things that we find is that we can place patients on their stomach, what we call the prone position. That’s also for severe injury, and that homogenizes the ventilation. So just putting them on their stomach causes less injury to the lung. That’s been shown recently to also improve mortality.
Falk: So there have to be new ICU beds that have a place for the person to be able to lie on their stomach with a tube, there have to be holes in the bed.
Mock: There are specialty beds, but actually it’s not a process that is done with a lot of extra effort. It takes 3 or 4 nurses and a staff willing to place a patient on their stomach. In this study there weren’t any increase in adverse events–the tube coming out, extra bleeding, pressure ulcers-so there isn’t a lot of risk to actually just move a patient on their stomach for up to sixteen hours a day. We know and we’ve seen that that improves oxygenation and does have a mortality benefit. Twenty days out, patients that are proned early, on their stomach early, have an 18% mortality versus about a 30% mortality.
Falk: What about the role of physical therapy?
Mock: It’s huge. Even more so now, we’re finding that from a basic science standpoint, exercise actually is probably anti-inflammatory. Patients that have active physical therapy in an ICU, even on a ventilator, helps those long-term outcomes. On average, a patient who survives ARDS, about 77% return to work in one year. Physical therapy early on helps fight against the long-term morbidities of muscle weakness, neurocognitive abnormalities such as memory, depression.
Falk: When a patient is in an ICU, whether they’re on a ventilator or not, most of the time patients do not recall that much about the episode in any case. Does physical therapy help with that post-ICU phenomenon?
Mock: It does. It helps against what you’re describing as Post-ICU Delirium. So even two decades ago, patients, to promote being in sync with the ventilator, they were heavily sedated, we’re finding that patients that are in sync with the ventilator, not fighting it, the less sedation we give them, the more physical therapy we give them, the less ICU delirium that they have.
Falk: So it’s a balance between paralysis, sedation, and being able to do physical therapy.
Mock: Correct. We only reach for paralysis in severe cases, the small fraction. The majority of patients on a ventilator, the goal is now to keep them awake, and have them work with physical therapy. Actually walk down the hall on the ventilator, if possible.
Falk: If you’re sitting in the ICU and you’re caring for somebody, what questions do you want the family to ask you?
Mock: The families often asks first, how likely the patient is to survive this. That’s a difficult question to answer oftentimes, and I don’t like giving percentages. But knowing the etiology and knowing the patient, it becomes very patient-specific. It’s the sort of patient who has a disease process, and not a disease that a patient has-is helpful.
The other thing that patients’ families want to know is what to expect if they get better. Telling them that they’re in for potentially a long rehabilitation stay, and some of these other consequences—memory loss, post-ICU delirium, even post traumatic stress disorder from the ICU. Those are the sort of things that patients’ families ask us, and I often talk about as they improve through their stay, what to expect after they leave the ICU.
Falk: On the other side of the coin, how do you tell a family member or another physician how to avoid ARDS?
Mock: There’s a lot of studies now in how do we prevent this from even happening in the first place. Patients that are on a ventilator who have no injury. We know that those small volumes help prevent ARDS or lung injury from first occurring. We know that less sedation is usually helpful. We know that sitting a patient up in bed to keep from aspirating and causing more damage to their lungs, is also helpful.
Falk: If somebody hasn’t been ventilated yet and you’re worried about them developing ARDS, what can be done in those hours before the thought of ventilation happens?
Mock: Using other modalities that don’t place a patient on a ventilator, things like noninvasive ventilation—high flow, that give a lot of oxygen, but to an awake patient that helps support their need for that oxygen. Without having to then place them on a ventilator.
Falk: Probably give them plenty of oxygen and maybe even if possible get them up. Jason, thank you so much for spending time with us today.
Mock: You’re welcome. Thanks for having me.
Dr. Jason Mock is an Instructor in the Division of Pulmonary Diseases and Critical Care Medicine.
This is the second segment of Dr. Falk’s conversation with Dr. Mock.
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