Medical Image of the Month: Air Bronchogram Sign

Figure 1. Chest radiograph showing bilateral dense airspace disease with air bronchograms. Veno-venous ECMO catheter is visible tracking from the right internal jugular vein to the inferior vena cava.

Figure 2. Chest radiograph on day 5 of ECMO after 4 days of induction chemotherapy demonstrating marked improvement of his airspace disease.

An 18-year-old man without any known past medical history presented with a one-day history of progressive shortness of breath. He reported a sudden onset of symptoms the morning of presentation, and an accompanying sensation of confusion with difficulty concentrating. Initial laboratory evaluation was significant for leukocytosis over 60 K/mm³. Due to his increased work of breathing and worsening lethargy, the patient was intubated and sedated for airway protection and ventilatory support. The patient was admitted to the ICU, and his initial chest radiograph was concerning for acute respiratory distress syndrome. Subsequent hematologic analyses from his admission CBC were consistent with a new diagnosis of acute myelogenous leukemia.

Despite aggressive alveolar recruitment maneuvers and maximum ventilator support, the patient’s oxygen saturation remained poor and his respiratory reserve continued to decline. The decision was made to place the patient on veno-venous extracorporeal membrane oxygenation (ECMO) prior to initiating therapy with doxorubicin and cytarabine (7+3 induction protocol). A dual-lumen ECMO catheter was placed in the right internal jugular vein. His initial chest radiograph demonstrated complete bilateral air bronchograms (Figure 1). The patient was started on chemotherapy while on ECMO and was successfully decannulated after five days on the circuit. His chest radiograph on day 5 of ECMO was significant for marked improvement in bilateral airspace disease (Figure 2).

In patients with hematologic malignancy, an inflammatory response can be generated by either the malignant cells themselves, or more commonly as a reaction to subsequent infection. This inflammation often results in protein-rich fluid infiltrating the alveoli. When this process becomes severe enough to cause hypoxic respiratory failure, it can progress to acute respiratory distress syndrome (ARDS) (1). The chest radiograph demonstrates dense airspace disease which developed in this patient. The fluid-filled alveoli in this extreme example of ARDS created a volume of uniform opacities throughout his lung parenchyma which make the conducting airways stand out clearly (2). Segmental air bronchograms can be seen in localized airspace disease, such as atelectasis or pneumonia, but a full-pulmonary air bronchogram of this clarity can only be seen on a patient undergoing ECMO as there are effectively no functional alveoli to participate in gas exchange.

Eric Brucks, MD and Richard Young, MD

Department of Internal Medicine

Banner University Medical Center

University of Arizona

Tucson, AZ USA

References

1. Papazian L, Calfee CS, Chiumello D, Luyt CE, Meyer NJ, Sekiguchi H, Matthay MA, Meduri GU. Diagnostic workup for ARDS patients. Intensive Care Med. 2016 May;42(5):674-85. [CrossRef] [PubMed]
2. Natt B, Raz Y. Air Bronchogram. N Engl J Med. 2015 Dec 31;373(27):2663. [CrossRef] [PubMed]

Cite as: Brucks E, Young R. Medical image of the month: air bronchogram sign. Southwest J Pulm Crit Care. 2019;19(4):119-20. doi: https://doi.org/10.13175/swjpcc036-19 PDF 

Medical Image of the Week: Fat Embolism

Figure 1. A CT with IV contrast at the pelvic level showing a filling defect (red arrow) in left external iliac vein extending from left common iliac vein in axial (A), sagittal (B), and coronal (C) sections. Its attenuation coefficient (Hounsfield Unit) suggests fat embolus mixed with thrombus.

A 74-year-old woman presented to the hospital with a left femoral neck fracture after a fall. The next day she underwent an uneventful left hip hemiarthroplasty. About 3 hours postoperatively, she became lethargic, tachycardic, tachypneic, febrile, and hypotensive. An arterial blood gas analysis revealed mild hypoxemia with PaO2 / FiO2 ratio of 270. Hemoglobin decreased from 9.4g/dL to 7.7g/dL postoperatively. A chest x-ray showed only bibasilar opacities. Sepsis, acute postoperative blood loss anemia, and pulmonary embolism (PE) were entertained as a differential diagnosis. The patient was resuscitated with intravenous fluids and packed red blood cells, and was started on broad-spectrum antibiotics. Her hemodynamic status stabilized shortly thereafter. A CT chest with PE protocol and abdomen/pelvis down to thigh level was performed; no PE was identified. It did not show any intraabdominal pathology or signs of hemorrhage. However, it incidentally revealed fat embolus mixed with thrombus in the left common and external iliac veins (Figure 1). All microbiologic studies were negative. Therefore, she was thought to have fat embolism syndrome (FES) with transient systemic inflammatory syndrome (SIRS). An IVC filter was placed and anticoagulation was also started.

FES is a collection of symptoms and signs including respiratory insufficiency, petechial rash, and neurologic impairment associated with fat in the circulation (1). Fat emboli cause an intense inflammation (2), and FES shares many features characteristic of systemic inflammatory response syndrome (SIRS) (1). It is a diagnostic challenge as many of the manifestations are common to other critical illnesses (1). It is most commonly associated with long bone fractures and orthopedic procedures. Literature on radiographic finding of fat emboli in the venous system is rare (3); although neither necessary nor sufficient, its radiographic demonstration in the venous system can substantially aid in diagnosis of FES, as demonstrated in our case.

Hyeong J. Kim MD¹, Michael Jesinger MD², and Medhi Khosravi MD²

¹ Division of Pulmonary, Critical Care, and Sleep Medicine, East Carolina University, Greenville, NC, USA

² Internal Medicine, University of Kentucky, Lexington, KY, USA

³ Division of Pulmonary, Critical Care, and Sleep Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, Lexington, KY, USA

References

1. Mellor A, Soni N. Fat embolism. Anaesthesia. 2001 Feb;56(2):145-54. [CrossRef] [PubMed]
2. Kwiatt ME, Seamon MJ. Fat embolism syndrome. Int J Crit Illn Inj Sci. 2013 Jan;3(1):64-8. [CrossRef] [PubMed]
3. Harris AC, Torreggiani WC, Lyburn ID, Zwirewich CV, Ho SG, Munk PL. CT and sonography of traumatic fat embolism in the common femoral vein. AJR Am J Roentgenol. 2000 Dec;175(6):1741-2. [CrossRef] [PubMed]

Cite as: Kim HJ, Jesinger M, Khosravi M. Medical image of the week: fat embolism. Southwest J Pulm Crit Care. 2017;15(6):297-8. doi: https://doi.org/10.13175/swjpcc138-17 PDF

Medical Image of the Week: Complex Arteriovenous Malformation

Figure 1. Initial chest radiograph demonstrating right mid lung field process.

Figure 2. Panel A: Contrast enhanced thoracic CT scan axial view demonstrating very large, complex AVM. Panel B: Sagittal view.

Figure 3. Chest radiograph after coil embolization.

A 62-year-old man presented to the emergency department complaining of shortness of breath with exertion and mild non-productive cough. The patient was afebrile and physical exam was remarkable only for scattered bilateral rhonchi. White blood cell count was 8,800 K/uL and hematocrit was 51.5%. Room air arterial blood gas (at 1520 meters altitude) was pH 7.41, pCO2 42 mm Hg, PO2 45 mm Hg, and O2 saturation 78%. D-dimer was normal at 0.36 ug/ml. Chest radiograph (Figure 1) demonstrated what was interpreted as a right-sided mid/lower lung field infiltrate. The patient was placed on high-flow supplemental oxygen and treatment was initiated with intravenous levofloxacin, methylprednisilone and nebulized beta-agonists. The patient’s oxygenation failed to improve over a period of several days, and a CAT of the chest (Figures 2) was obtained, which demonstrated a very large, right middle lobe, complex pulmonary arteriovenous malformation. The patient was referred to interventional radiology for catheter directed coil embolization (Figure 3). Following that procedure the patient’s oxygen requirement decreased from 15 l/m via nasal cannula to 3 l/m.

Pulmonary arteriovenous malformations (PAVM’s) are rare, with an incidence of 2-3 per 100,000, and are associated with hereditary hemorrhagic telangiectasia (HHT), in approximately 80% of cases (1). The intrapulmonary shunt associated with PAVM’s may result in significant hypoxemia, cerebrovascular accident or embolic brain abscess. The preferred screening tool is transthoracic contrast echocardiography, which demonstrates extra-cardiac shunt. Chest CT scan may be used to both confirm the diagnosis of PAVM and to define the vascular anatomy. Patients who meet three of the four Curacao criteria (epistaxis, family history, telangiectasia, and visceral lesions) are recognized as suffering from HHT (2). Catheter directed coil embolization is an effective and well-tolerated treatment method for PAVM; and generally results in reduced shunt fraction and improved oxygenation (3).

Kathleen Monahan and Charles J. VanHook MD

Longmont United Hospital

Longmont, Colorado USA

References

1. Cartin-Ceba R, Swanson KL, Krowka MJ. Pulmonary arteriovenous malformations. Chest. 2013 Sep;144(3):1033-44. [CrossRef] [PubMed]
2. Shovlin CL, Guttmacher AE, Buscarini E, Faughnan ME, Hyland RH, Westermann CJ, Kjeldsen AD, Plauchu H. Diagnostic criteria for hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber syndrome). Am J Med Genet. 2000 Mar 6;91(1):66-7. [CrossRef] [PubMed]
3. Dutton JA, Jackson JE, Hughes JM, Whyte MK, Peters AM, Ussov W, Allison DJ.Pulmonary arteriovenous malformations: results of treatment with coil embolization in 53 patients. AJR Am J Roentgenol. 1995 Nov;165(5):1119-25. [CrossRef] [PubMed]

Cite as: Monahan K, VanHook CJ. Medical image of the week: complex arteriovenous malformation. Southwest J Pulm Crit Care. 2016 May;12(5):197-8. doi: http://dx.doi.org/10.13175/swjpcc027-16 PDF

Medical Image of the Week: Pulmonary Arteriovenous Fistula

Figure 1. Panel A: Micro-bubbles appear in the right atrium (RA) and right ventricle (RV) with delayed appearance in the left atrium (LA) and left ventricle (LV). Panels B and C: The density of the micro-bubbles were same in the left and the right cardiac chambers even after 10 cardiac cycles. Panel D: When the injection was stopped, there were micro-bubbles in the left cardiac chambers, but none in the right cardiac chambers.

A 60 year-old man with hepatic cirrhosis, was referred for chest pain, shortness of breath, and progressive cyanosis and an echocardiographic evaluation. PaO2 was 64 mm Hg on room air, but only 74 mm Hg on 100% oxygen.  Chest X-ray and pulmonary function testing were normal. A contrast echocardiography using agitated saline (bubble study) was performed. A delayed appearance of a substantial amount of micro-bubbles in the left atrium greater than three cardiac cycles after appearance in the right atrium and ventricle was suggestive of pulmonary arteriovenous fistula (Figure 1A). The delayed appearance and a large amount of micro-bubbles in the left atrium preclude the intracardiac shunting result of a patent foramen ovale (PFO) or atrial septal defect (ASD). Interestingly, the density of micro-bubbles were same in the left and the right cardiac chambers even after 10 cardiac cycles (Figure 1B and 1C). When the injection was stopped, there were micro-bubbles in the left cardiac chambers, but none in the right cardiac chambers (Figure 1D). Although pulmonary angiography remains the gold standard method for definitive diagnosis of the pulmonary arteriovenous malformations, contrast echocardiography can suggest arteriovenous fistula in the setting of unexplained hypoxemia before angiography, especially in hospitals without on-site angiography facilities.

Manisha Bajracharya MD, Madhu Gupta MD, Liping Chen MD PhD

Department of Gynecology and the Cardiovascular Disease Center, Norman Bethune College of Medicine, Jilin University, Changchun, China

Reference

Nanthakumar K, Graham AT, Robinson TI, Grande P, Pugash RA, Clarke JA, Hutchison SJ, Mandzia JL, Hyland RH, Faughnan ME. Contrast echocardiography for detection of pulmonary arteriovenous malformations. Am Heart J. 2001;141(2):243-6. [CrossRef] [PubMed]

Reference as: Bajracharya M, Gupta M, Chen L. Medical image of the week: pulmonary arteriovenous fistula. Southwest J Pulm Crit Care. 2014;8(4): . doi: http://dx.doi.org/10.13175/swjpcc035-14 PDF