Critical Care Scenarios Brandon Oto, PA-C, FCCM and Bryan Boling, DNP, ACNP, FCCM

We discuss the field of rehabilitation psychology, and how it can help patients with persistent critical illness, with Dr. Megan Hosey (@DrMeganHoseyPhD), clinical psychologist and assistant professor at Johns Hopkins School of Medicine, where she practices in the medical ICU.







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Takeaway lessons









* Rehabilitation psychology is a specialty of clinical psychology that generally partners with patients who have acute illness or injury, and helps them adapt to life in these new circumstances. They discuss health behaviors, values and priorities, help patients find paths back to what they love, and assess cognitive and behavioral changes that accompany new illness. In the ICU, they can assist with the psychological aspects of care, particularly in patients with a prolonged stay where psychological factors play an important role in recovery, or for treatment-refractory delirium.







* Delirium often dominates the patient experience of the ICU. This is primarily an experience of inattention, with relatively little awareness of their circumstances, the day, the context for events, and the presence of often-vivid hallucinations and delusions.







* ICU care is highly anxiety provoking, with common questions of “when,” “why,” and many other (often unanswerable) questions. The more certainty and structure you can provide, the better.







* Depression is common as well in longstanding inpatients, and is often better characterized as “hospital demoralization,” a fairly appropriate response to prolonged confinement and limited access to their regular life. This can lead to sensations of helplessness and hopelessness.







* Motivation can be improved by strategies to reduce the emotional barriers to engagement, while also strengthening their sense of meaning—i.e. what matters to them, and how will their involvement help move towards that?







* Effective psychological care relies on communication with the patient, and medical measures like tracheostomies and endotracheal tubes can be a barrier. Good care that minimizes sedation and delirium, close involvement from respiratory therapy and speech therapy (with tools like speaking valves), and non-verbal tools like speech boards, eye gaze, yes/nos, etc. are key.







* Patients with persistent/chronic critical illness appreciate having their schedule set out for the day, to give them a clear sense for what to expect and reduce anxiety.







* Try to build pleasurable activities into their day, aka “behavioral activation.” Doing things that are meaningful and pleasurable creates a positive feedback loop that enables more activity. Animal therapy, “sunshine therapy” (getting outside), music therapy (or just playing preferred music) are all valuable. Merely asking patients their preferred music and playing it can reduce anxiety and sedation requirement (see Linda Chlan’s work on this)







* Relaxation strategies can be learned, and in the ICU setting, vital sign monitoring can even be used as a form of biofeedback to appreciate changes in heart rate or respiratory rate in response to stress.







* Motivational interviewing emphasizes taking control over the aspects of their life that can be controlled.







* Normalize and validate the difficulty of being in the hospital.

We explore the profession of respiratory therapy in the US, including their role and training and how to optimize our clinical relationships, with Keith Lamb (@kdlamb1), RRT, RRT-ACCS, FAARC, FCCM. Keith is an RT at the University of Virginia in Charlottesville, working clinically in neuro/surgical/trauma critical care, who has been active in research and has held a variety of leadership positions.







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Responsible self-directed learning occurs in a zone between comfort and novelty.







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We discuss the principles and application of automatic tube compensation (ATC) on modern ventilators, with its creator Ben Fabry. Dr. Fabry is a professor and chair of biophysics at University of Erlangen-Nuremberg, originally trained as an electrical engineer, who originally developed ATC as part of his PhD program.







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Takeaway lessons









* ATC, originally called “electronic extubation,” is meant to normalize or eliminate the resistance to flow created by the endotracheal tube. Since this resistance is always present, yet is dynamic and varies by flow (and tube size), it creates a continuous confounding variable, making the displayed pressure on the ventilator a measurement not of tracheal pressure, but of another, largely meaningless pressure (the pressure outside the patient).







* ATC works by increasing airway pressure during spontaneous inspiration to eliminate the pressure gradient created by the tube at the current flow, and reducing it during expiration to reverse the effect.







* While ATC can be used in any mode, it is mostly meant for pressure support or other spontaneous modes. It has no real role in volume control. In pressure control, it has little meaningful impact during inspiration, although it will reduce the airway pressure below the set PEEP during expiration, which may help facilitate expiration.







* The original ATC test ventilator could drop pressure below atmospheric pressure during expiration, but this feature is not possible on modern ventilators, so the lowest possible pressure during ATC is zero (probably not quite even, that due to expiratory valve resistance). Some modern vents will not drop pressure during expiration at all.







* In principal, actual tracheal pressure could be measured by a separate monitoring lumen. In practice, this is dangerous, as the lumen could be occluded by mucus, so the resistance constant is instead applied mathematically. The modifiers were derived empirically by testing a variety of tubes at different flow rates.







* ATC will generally ask for the tube size. Length has some effect but a fairly trivial one, as resistance is mostly influenced by turbulence, which is mainly a product of diameter. Resistance is not a constant, but increases with (roughly) the square of the flow of gas.







* A swivel connector on the ETT outlet adds about 1 cm H2O of resistance. An HME adds about 3 cm H2O.







* Changes in gas composition at different FiO2 changes resistance trivially, although a mix like Heliox would change it significantly, and would make the internal calculations incorrect.







* No fixed single pressure support value can accurately match tube resistance, due to its dynamic nature during and between breaths, even if you were willing to set the sort of pressure needed—which might be 50+ cm H2O in a strongly breathing patient.







* The main downside of ATC is that modern ventilators don’t do it very well—they can only vary flow so quickly, so when there are brisk changes in pressure, they fail to match it. They usually can match only about 50% of tube resistance, with the worst at the start of a breath as they lag behind the initial drop in pressure. (You can appreciate this by seeing the airway pressure drop below the set PEEP.) Response is even less in some of the current generation of vents with radial blowers and slower valves







* Quality check your ATC by watching the tracheal pressure—the vent will display this ...

Brandon summarizes his recent publication describing best practices for performing POCUS. Read the paper open access at POCUS Journal.







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Our collaboration with Sarah Lorenzini of the Rapid Response RN podcast, discussing a case and general principles for diagnosing and managing obstructive shock. Check out the other episodes on shock in the Nurses’ Podcrawl 2024!







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