Peer Reviewed

Radiology Quiz

What Caused This Older Man’s Persistent Desaturation?

    Aryan Vahedi-Faridi, MD, MS1 • David Perkins, MD, MPH1 • Kevin Govani1 • Michael Ebisi2 • Sumera Khan3 • Pranav Patel, MD4

    1Saint James School of Medicine, Anguilla
    2Avalon University School of Medicine, Curaçao
    3Windsor University School of Medicine, Saint Kitts and Nevis
    4Palos Medical Care, Palos Heights, Illinois

    Vahedi-Faridi A, Perkins D, Govani K, Ebisi M, Khan S, Patel P. What caused this older man’s persistent desaturation? Consultant. 2022;62(3):e12-e14. doi:10.25270/con.2021.04.00014

    Received November 18, 2020. Accepted January 13, 2021. Published online April 22, 2021.

    The authors report no relevant financial relationships.

    Aryan Vahedi-Faridi, MD, MS, BS, Saint James School of Medicine, Albert Lake Drive The Quarter, A-1 2640, 2640, Anguilla (


    A 72-year-old Black man presented to our clinic with subjective fever, severe fatigue, chest tightness, and dry cough for the previous 3 days. His history was significant for hypothyroidism, and he was a lifelong nonsmoker. The patient denied any illicit drug use and had no history of asthma or aspiration disease.

    A physical examination was significant for dyspnea, dry cough, and decreased exercise tolerance. Oxygen saturation was measured at 96% on room air. Community-acquired pneumonia (CAP) was suspected, and the patient was sent home with a 5-day course of azithromycin and a methylprednisolone dose pack.

    At the follow-up visit 1 week later, the patient reported no improvement in his symptoms. Clinically, he appeared worse than his previous visit, with significant fatigue and dyspnea on minor exertion. A physical examination demonstrated diffuse wheezing and crackles in both lung bases. Pulse oximetry measured an oxygen saturation of 88% on room air. Given his condition, the patient was instructed to go to the emergency department for further evaluation.

    At the hospital, the patient continued to show poor oxygen saturation but showed some improvement after being given an oxygen mask. The bilateral crackles that were heard previously had diminished with use of the mask. Inflammatory markers were significant for an elevated erythrocyte sedimentation rate of more than 100 mm/h (reference range, 0-20 mm/h), leukocytosis with a white blood cell count of 14.0 × 109/L (reference range, 3.4-10.3 × 109/L), and neutrophilia with a neutrophil count of 11.30 × 109/L (reference range, 3.02-6.35 × 109/L) and neutrophil percentage of 80.7% (reference range, 35.0%-79.0%).

    Diagnostic testing. Acute hypoxemic respiratory failure was diagnosed because of his persistent oxygen desaturation to 88% on room air. Patients with persistent hypoxemia of less than 90% and signs of respiratory distress, such as dyspnea or accessory muscle use, meet criteria for a formal diagnosis of acute hypoxemic respiratory failure even without arterial blood gas results per European Respiratory Society/American Thoracic Society guidelines.

    Results of a metabolic panel indicated anion gap metabolic acidosis, with a sodium level of 130 mEq/L (reference range, 135-145 mEq/L), bicarbonate level of 20 mEq/L (reference range, 23-30 mEq/L), and a serum anion gap of 22 mEq/L (reference range, 3-10 mEq/L). The patient’s glucose level was 116 mg/dL.

    Results of viral respiratory, hepatitis, fungal, and autoimmune panels were negative for atypical pulmonary disease. These panels included serology assays for influenza, hepatitis A-C, legionella, blastomycosis, histoplasmosis, antinuclear antibodies, and rheumatoid factor. A chest radiograph taken during the initial survey showed extensive bilateral lower and middle lobe consolidation (Figure 1). Blood cultures and a Gram stain also were negative for bacterial pathology.

    Figure 1. Chest radiograph taken just prior to intubation for worsening acute hypoxemic respiratory failure
    Figure 1. Chest radiograph taken just prior to intubation for worsening acute hypoxemic respiratory failure.


    A computed tomography (CT) scan of the chest with contrast demonstrated interstitial disease with subpleural reticular infiltration in both lungs without any findings for pulmonary embolism (Figure 2). Chest radiographs continued to demonstrate progressive alveolar infiltrates and pleural effusions throughout the patient’s initial course. Despite continued oxygen therapy with a target oxygen saturation of more than 90% on room air and treatment with broad-spectrum antibiotics for suspected CAP, the patient progressively began to desaturate below goal and was admitted to the intensive care unit for advanced respiratory management. A trial of bilevel positive airway pressure (BiPAP) therapy failed to improve his condition, and he was subsequently intubated. Bronchoscopy with alveolar lavage was performed several days after intubation but did not yield any positive findings in culture for fungal mycobacterial or bacterial cultures. A Gram stain of the samples was also negative.

    Figure 2a. Axial view
    Figure 2b. sagittal view
    Figure 2. Axial (a, top) and sagittal (b, bottom) CT views of the chest taken several days after admission, demonstrating interstitial disease with subpleural reticular infiltration in both lungs.




    Answer and discussion on next page.