Postgraduate Clinical Section Reading chest radiographs in the critically ill (Part II): Radiography of lung pathologies common in the ICU patient Khan Ali Nawaz, Al-Jahdali Hamdan, Al-Ghanem Sarah, Gouda Alaa King Fahad Hospital, Abstract: King Abdulaziz Medical This is part II of two series review of reading chest radiographs in the critically ill. Conventional chest radiography City, Riyadh, Saudi remains the cornerstone of day to day management of the critically ill occasionally supplemented by computed Arabia tomography or ultrasound for specific indications. In this second review we discuss radiographic findings of cardiopulmonary disorders common in the intensive care patient and suggest guidelines for interpretation based not only on imaging but also on the pathophysiology and clinical grounds. Key words: Chest x-ray, intensive care unit, cardiopulmonary disorders nterpreting chest radiographs in the critically The aim of this paper is[1] to discuss the radiographic Iill patients in intensive care units (ICU) poses a findings of cardiopulmonary disorders common challenge not only for the intensive care physicians in the ICU patient and suggest guidelines for but also for the radiologist. These challenges arise interpretation based not only on the chest because of several factors:[1] ICU patients are prone radiograph but also on the pathophysiology and to several cardiopulmonary disorders which when clinical grounds;[2] to describe the normal position superimposed on the underlying pathology that of monitoring devices and correct placement prompted admission creates a complex radiological of other lines , and prompt recognition when appearance, which may be difficult to interpret on they are misplaced or when other complications imaging findings alone.[2] The standard postero- occur. We discuss correct placement of, as well as anterior (PA) radiograph is replaced by the common complications due to, monitoring lines. suboptimal AP radiograph in the ICU patient.[3] [1] Instrumentation, mechanical ventilation, equipment This is a two-part series: Part I: Normal chest radiographic appearances in the ICU patient, for monitoring of cardiac and other vital signs, correct and incorrect placement of various feeding tubes, etc., distract from other findings intrathoracic tubes and lines and complications on the ICU chest radiograph.[4] Radiologists/ from instrumentation. Part II: Radiography of Intensive care physicians are under pressure for lung pathologies common in the ICU patient. rapid interpretation of chest x-rays when treating critically ill patients, often with inadequate clinical Pulmonary Edema information partly due to the fact that things can change rapidly in the critically ill.[5] Radiological Pulmonary edema is secondary to accumulation interpretation is hampered by the bewildering Address for of fluid in the lung interstitium or alveolar space. correspondence: array of line placements in the ICU patient, where Pulmonary edema is frequently seen and is a Dr. Ali Nawaz Khan King incorrect placement is not uncommon, which may common cause of oxygen desaturation in the Abdulaziz Medical City, not be obvious to the observer without clinical King Fahad National ICU patient. Several mechanisms are implicated input.[6] Air space shadowing in the ICU patient Guard Hospital, P.O. Box in the genesis of pulmonary edema, including 22490, Riyadh 11426, may have identical appearances in a variety of increased hydrostatic gradient, increased oncotic Saudi Arabia. cardiopulmonary pathologies. Although the pressure or increased capillary permeability. One E-mail: drkhan1966@msn. imaging modality of choice in the ICU patient or a combination of these mechanisms may be com remains that of chest radiography, computed involved. Pulmonary edema is broadly subdivided tomography is often performed as computerized into cardiac and noncardiac. Cardiac edema is tomography pulmonary artery (CTPA) with Submission: 15-12-08 usually secondary to poor cardiac function, whilst Accepted: 29-01-09 suspected pulmonary embolism. Ultrasound is noncardiogenic pulmonary edema can result from DOI: used to confirm pleural and pericardial effusions volume overload, diminished oncotic pressure or 10.4103/1817-1737.53349 and when pleural intervention is planned. from endothelial injury as in the patient with adult Annals of Thoracic Medicine - Vol 4, Issue 3, July-September 2009 149 Khan, et al.: Reading chest radiographs in the critically ill respiratory distress syndrome (ARDS). lower lung, extending to the pleura [Figure 1]. Interstitial edema results from fluid collection in the lung Alveolar pulmonary edema generally develops when the interstitial space and usually develops when the pulmonary pulmonary venous pressure exceeds 30 mm Hg and is venous pressure rises to 25-30 mm Hg. Interstitial pulmonary usually preceded by interstitial pulmonary edema [Figure 2]. edema is one condition which may be seen on a chest radiograph Chest radiographic findings include bilateral opacities that before symptoms develop. Radiographic signs that suggest extend in a fan shape outward from the hilum in a ‘batwing’ interstitial pulmonary edema include loss of definition of large pattern [Figure 3]. With worsening alveolar edema, the lung pulmonary vessels, the appearances of septal lines, interlobar opacification become increasingly homogenous. Normally the septal thickening, diffuse reticular pattern resembling interstitial bronchi in the lung periphery are not seen because of air density fibrosis and peribronchial cuffing seen as bronchial wall within the bronchi and the surrounding lung parenchyma. thickening as a result of fluid retention in the lung interstitium. However, along with fluid-filled alveoli from pulmonary edema Septal lines represent fluid in the deep septae and lymphatics or infection (pneumonia), the air-filled bronchi can be easily and appear as[1] Kerley’s A lines, which range from 5 to 10 cm seen, an appearance known as ‘air bronchogram’ [Figure 4]. in length and extend from the hilum of the lung toward the Air bronchograms associated with congestive heart failure are periphery in a straight or slightly curved course; and[2] Kerley’s usually visible in the right upper lobe. In pulmonary edema B lines, approximately 2 cm long, seen in the periphery of the due to heart failure, the heart size is often enlarged. Figure 1: Frontal chest radiograph (right) showing features of interstitial pulmonary edema. Radiographic signs (shown in the figure) that suggest interstitial pulmonary edema include loss of definition of large pulmonary Figure 2: Frontal chest radiograph showing features of alveolar pulmonary vessels, the appearances of septal lines, interlobar septal thickening and edema. The findings include opacification of both lungs with increasing diffuse reticular pattern associated with cardiomegaly. Both Kerley’s A and density towards the lung bases due to a combination of air space shadowing Kerley’s B lines are seen. The magnified view of the left costophrenic angle is and pleural effusions, cardiomegaly, upper lobe blood diversion (unreliable from another patient, depicting Kerley’s B lines (left) on supine AP radiograph) and an air bronchogram in the right upper zone Figure 3: A frontal chest radiograph and axial CT show features of ‘batwing’ Figure 4: Supine portable chest radiograph showing extensive air space alveolar pulmonary edema. Chest radiographic findings include bilateral shadowing throughout the whole of the right lung and the left lung base due opacities that extend in a fan shape outward from the hilum in a batwing; to alveolar pulmonary edema with associated pleural effusions secondary to pattern. With worsening alveolar edema, the lung opacification becomes heart failure. Note the air bronchograms in the right upper zone, sometimes increasingly homogenous seen with congestive heart failure 150 Annals of Thoracic Medicine - Vol 4, Issue 3, July-September 2009 Khan, et al.: Reading chest radiographs in the critically ill Diagnosis of pulmonary edema is not always straightforward, Adult Respiratory Distress Syndrome and atypical patterns can present diagnostic difficulties on radiographic findings alone. Atypical radiographic patterns Adult respiratory distress syndrome (ARDS) is a term applied of pulmonary edema include unilateral, lobar, miliary or to a syndrome where signs and symptoms of pulmonary lower-zones edema; and other asymmetric or unusual edema occur in the absence of elevated pulmonary venous distribution patterns [Figure 5]. Miliary edema may precede pressures. ARDS is associated with high mortality, as much full-blown lung edema. Lower-zones edema and lobar as 50%, and is common in the ICU patients. ARDS results pulmonary edema generally occur in patients with chronic from a variety of causes, including sepsis or pulmonary obstructive pulmonary disease and pulmonary emphysema. infection, severe trauma, and aspiration of gastric contents.[17] The final pathway in ARDS is common to all causes, which Congestive cardiac failure causing cardiogenic pulmonary edema is damage to the alveolar capillary endothelium, increased is usually the result of left ventricular failure, which is in turn vascular permeability, and subsequent development of due to poor cardiac output and increased pulmonary venous first, interstitial, and then, alveolar pulmonary edema. hydrostatic pressures. Generally it is a combination of a failing Patients with ARDS present with severe respiratory distress cardiac pump and fluid overload that