— MEDICAL SCHOOL —
Oregon Health & Science University School of Medicine
— GRADUATING CLASS —
As medical students, we spend 1.5 to 2 years learning the many ways in which our bodies work—and the many ways in which they can malfunction or even stop working. We spend hours putting together pieces of the puzzle known as the human body. We spend many more hours learning the myriad manifestations of physiology gone wrong. I remember spending time during one of our heaviest blocks, cardio–pulmonary–renal, learning not only how our lungs function but also the incredible ways in which we adapt: for example, to keep our puzzle whole, minute changes in oxygen and carbon dioxide set off a cascade of events.
If I am low on oxygen, sensors in my body will go off and tell my lungs to breathe faster. If I have too much acid in my body, my lungs will try to blow off carbon dioxide to bring my body back into balance. We learn to recognize normal breathing and what is not so normal. In clinic, we talk about the importance of recognizing “sick” and “not sick.” That is, does my patient look like they are struggling to breathe? Have they recruited muscles typically not used for normal breathing? Do they appear pale or disoriented? Do they need higher levels of care or intervention?
The COVID-19 pandemic has made learning this knowledge not only practical but essential. Now more than ever, we as students are exposed to the ravages of lung disease, from COVID-19 pneumonia, acute respiratory distress syndrome (ARDS), secondary bacterial infections, to blood clots in the lungs. As students, our job on wards and in clinic is to learn these signs and symptoms, recognize the ill, and ensure their safety and receipt of appropriate care. One day, it will be on us to make those decisions, and that day is coming sooner every minute.
On my very first rotation, I was asked by my attendings how we recognize neonatal distress. We talked about how to identify the typical findings, looking at how the neonates are breathing. Is there accessory muscle usage? Nasal flaring? Are they restless or still and quiet? Adults are rarely still and quiet, but the signs and symptoms are often similar. Patients will say, “I can't catch my breath,” and we will notice the prominent strain of the sternocleidomastoid, the gasping sounds emitting from their mouths, and their faces drained of color. We will see them grappling with illness and know they need help.
But what happens when these signs are absent? Can someone be in respiratory distress without any signs or symptoms? During the early pandemic, many news outlets were reporting patients with COVID-19 having oxygen saturations “incompatible with life” yet denying any trouble breathing, so-called “silent hypoxia.” There were reports of patients with oxygen saturations in the 60s playing with their cellphones in triage, others floridly denying any trouble breathing.
One such patient, a 70+-year-old man who had diabetes, presented to clinic “feeling off” but otherwise had no complaints. He denied any trouble breathing or any history of lung disease. His pulse oxygen read 74%. My first thought? No possible way is he sitting here comfortably with an oxygen saturation of 74%—this must be wrong. He did, however, have a fever, which prompted us to order a test for COVID-19. Ten seconds later, the rapid test was clearly positive. The patient was sent to the ED where a chest radiograph revealed lungs filled with fluid and he was diagnosed with ARDS. I was floored.
Is silent hypoxia real? Despite considerable media coverage, few medical journals have addressed the topic. The American Journal of Respiratory and Critical Care Medicine published a series of case reports on the subject in August of 2020. There are some physiologic explanations for why patients may appear “silently hypoxic” (1). Regardless of the precise physiology at play, it was both surprising and important for me to recognize that signs and symptoms might not always tell the full picture. There are many variations in presentation and many more reasons as to why that might be. For example, being elderly and having diabetes, both of which were present in this patient, can reduce the respiratory drive by 50% each (1).
This case was a near miss for me. I anchored on the many things I had learned about respiratory distress. If those weren't present, that must not be the diagnosis. Erroneously, I viewed his hypoxemia as artifact instead of fact. As I went through the internal medicine exercise of the “cognitive autopsy,” it was clear where some things had gone wrong. His fever helped to ground his case in the world of infection, and it provided potential evidence to support his low oxygen despite him appearing comfortable in our office. When viewed together, his low oxygen and fever recentered the case to his lungs and triggered us to order the COVID-19 test.
As medical students (and residents, fellows, and attendings), we will be constantly learning and growing our clinical knowledge and acumen. It is important to build our illness scripts and know what respiratory distress looks like. It is also important to know when the puzzle isn't looking quite right. As tempting as it is to jam that “near-but-not-quite-perfect” piece into place, wrong pieces are still wrong pieces. When clinical data don't match the story, we must reassess. We must go back and ask ourselves, “Are we missing anything?” Diagnostic reasoning is a skill that must be practiced consistently and diligently. It is a cornerstone of internal medicine and can take a lifetime to master.
Building illness scripts, taking in data, forming relationships with patients, and circling back to interpret data in the context of a person in front of you—these are all pieces of the puzzle we are building every day. It's tempting to think that we need to have all of the answers now, but the reality is that no person has every answer. Being a lifelong learner can be hard, but it is also a joyful process. As we move through our education and into our careers and beyond, we will continue to grow who we are as physicians. When the days are hard, when you miss that diagnosis, when something goes awry, remember: you're just building your puzzle.
- Tobin MJ, Laghi F, Jubran A. Why COVID-19 silent hypoxemia is baffling to physicians. Am J Respir Crit Care Med. 2020;202:356-360. [PMID: 32539537] doi:10.1164/rccm.202006-2157CP
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