How Healthcare Providers can Screen Patients for Pneumonia with a Stethoscope and Know When to Sequester and Test for COVID-19
Dr. Steve Pham
March 11, 2020
The global scientific and public health response to the continuing COVID-19 pandemic has been remarkable. Within two months, researchers identified and sequenced a novel respiratory illness. Diagnostics companies have developed several RT-PCR assays that can identify COVID-19 within hours. Radiologists can spot characteristic imaging patterns of lower respiratory infection caused by COVID-19 within minutes of CT scanning. However, access to these technologies remains limited. Providers can expect a turnaround time of 2 or more days for test results due to the constrained supply of RT-PCR assays. Diagnostic imaging might be available in every emergency department, but clinicians cannot expose every patient with a cough to 4 millisieverts of radiation.
If your clinical practice is like mine at the Emergency Department, then you have to negotiate between the high volumes of sick and worried patients and the overutilization of costly and constrained resources. How is a healthcare provider at the frontlines of care to know when to sequester and test for COVID-19? The answer might be hanging around your neck.
Public health institutions are recommending that providers risk stratify patients with geographic and personal risk of exposure to COVID-19 presenting with signs and symptoms of lower respiratory illness. The first step of any COVID-19 diagnosis depends not on the test itself, but on the fundamentals of physical examination described by Rene Laennec more than 200 years ago and still taught to this day on the first week of our clinical educations.
Now would be a good time to review what the signs of pneumonia are. Thorough vital sign measurement and careful auscultation are essential to identify patients with a risk of significant lower respiratory illness.
Start with the fundamentals: perform vital sign screening on patients who complain of a fever, shortness of breath, cough, or flu-like symptoms. Look for a temperature greater than 37.8 C, oxygen saturation less than 95%, and a peripheral pulse rate greater than 100 beats per minute. Just like sepsis screening, COVID-19 screening requires vital sign vigilance because the vital sign abnormality might be subtle. It sounds simple, but it’s easy to overlook a borderline febrile patient when everything about the patient screams “worried well.” Any vital sign abnormality should raise your suspicion for infection, and you should proceed with a very thorough and comprehensive physical exam.
Focus your physical exam on a complete auscultation of the lungs. Grab that decorative rubber neckpiece and listen to at least eight lung fields bilaterally. Pull out your dusty Bates’ Guide to Physical Examination and History-Taking and lookup egophony. Then listen for wheezes, crackles, and egophony.
Wheezes - lung sounds recorded a stethoscope
You know it when you hear it. The typical high-frequency whistling noise is very specific to airway narrowing. Lower respiratory tract infections can cause secretion and edema where the lung is infected. Focal or unilateral wheezes typically indicate focal pneumonia, however diffuse or bilateral wheezes could mean upper airway bronchospastic disease or diffuse multifocal pneumonia. This is not the most sensitive finding (15-30%), but when combined with crackles, can have a specificity of 97%.
Crackles - lung sounds recorded a stethoscope
Crackles, or rales, are a scratchy sound quality evident when fluid fills up in the alveolar and interstitial spaces. These sounds can be focal and coarse in localized areas of pulmonary edema or consolidation in pneumonia. Diffuse and fine crackles are more typical of pulmonary fibrosis, but can also be present in atypical types of pneumonia. In a 2017 study, crackles were the only physical exam finding out of 4 total findings that were significant in diagnosing radiographically confirmed pneumonias.
Egophony - lung sounds recorded a stethoscope
Egophony is my favorite provoked auscultation finding. Have the patient say “E” and auscultate to see if it becomes “A”. Pneumonia can consolidate focal parts of the lungs into dense tissue that filters out low frequencies, allowing for higher frequencies to pass through. Egophony had an LR+ of 5.3 for diagnosing radiographically confirmed pneumonia and appears to outperform other auscultation findings for pneumonia.
Of course, no physical exam or vital sign finding on its own is sufficient to identify pneumonia or lower respiratory tract infections. Use your stethoscope, but also use your judgment to help you identify who should be considered for COVID-19 investigation. Shoulders up, take a deep breath - you got what you need hanging around your neck.
About Dr. Pham
Dr. Steve Pham is a practicing emergency medicine physician, the head of medical and research affairs at Eko, and a new father. His passion is translating between digital and clinical insights.