Because up to 25% of ET tubes are initially suboptimally positioned, radiographic confirmation of tube location is crucial; positioning the ET tube in the right main bronchus often results in right upper lobe or left lung atelectasis or right sided barotrauma. (Left main intubations are uncommon because the left main bronchus is smaller and angulates sharply from the trachea.) Conversely, if the tube tip lies too high in the trachea (above the level of the clavicles), unintended extubation is likely. When the head is in a neutral position, the tip of the ET tube should rest in the mid-trachea, approximately 5 cm above the carina. In adult patients, the T5-7 vertebral level is a good estimate of carinal position if it cannot be directly visualized. The carina is usually located just inferior to the level of the aortic arch. (Another method to locate the carina uses the intersection of the midline of the trachea with a 45 degree bisecting line which passes through the middle of the aortic knob.) ET tubes move with flexion, extension, and rotation of the neck. Contrary to what might be expected, the tube tip moves caudally when the neck is flexed (i.e., chin down = tip down). Conversely, head rotation away from the midline and neck extension elevates the ET tube tip. Total tip excursion may be as much as 4 to 5 cm.

The normal ET or tracheostomy tube should occupy one half to two thirds of the tracheal width and should not cause bulging of the trachea in the region of the tube cuff. Bulging is associated with an increased risk of subsequent airway stenosis, presumably the result of tracheal wall ischemia from cuff overinflation. Gradual dilation of the trachea may occur during long-term positive pressure ventilation, but every effort should be made to prevent this complication by minimizing ventilator cycling pressure and cuff sealing pressures.

After tracheostomy, a CXR may detect subcutaneous air, pneumothorax, pneumomediastinum, or malposition of the tube. The T3 vertebral level defines the ideal position of the tracheostomy site. (This usually places the tip halfway between the stoma and the carina.) Unlike the orally placed ET tube, the tracheostomy tube does not change position with neck flexion or extension. Lateral radiographs are necessary for evaluation of AP angulation. Sharp anterior angulation of the tracheal tube is associated with the development of tracheoinnominate fistulas, whereas posterior erosion can produce a tracheoesophageal fistula. Massive hemoptysis usually signals the former condition, whereas sudden massive gastric distention with air occurs in the latter.

In patients with previous intubation or tracheostomy, the tracheal air column should be examined for evidence of stenosis. Tracheal narrowing is relatively common and can occur at the level of the tracheal tube tip, at the cuff, or at the tracheostomy tube stoma (most common site). The typical hourglass shaped narrowing can be hard to visualize on a single AP radiograph and stenosis must be substantial (luminal opening < 4 mm) to be symptomatic.

For accurate pressure measurement the tip of the CVC should lie within the thorax, well beyond any venous valves. These are commonly located in the subclavian and jugular veins, approximately 2.5 cm from their junction with the brachiocephalic trunk (at the radiographic level of the anterior first rib). Because CVC catheters in the right atrium or ventricle may cause arrhythmias or perforation, the desirable location for these lines is in the midsuperior vena cava, with the tip directed inferiorly. Radiographically, catheter tips positioned above the superior margin of the right mainstem bronchus are unlikely to rest in the atrium. Catheters should have no sharp bends along their course and should descend lateral and parallel to the spine. Stiff catheters, particularly hemodialysis catheters, inserted from the left subclavian may impinge on the lateral wall of superior vena cava, potentially resulting in vascular perforation. Complications resulting from vascular puncture include air embolism, fluid infusion into the pericardium or pleural space, hemopneumothorax, and pericardial tamponade. Imaging studies reveal that partial thrombosis occurs distressingly often with CVCs and peripherally inserted central catheters (PICC). Postprocedure radiographs reveal complications in up to 15% of CVC placements. On occasion, catheters inserted from the subclavian route can pass across the midline into the contralateral subclavian vein, or even turn cephalad entering the internal
jugular veins. Similarly, catheters inserted in the internal jugular veins may track into the subclavian vein of either side. The phenomenon of a subclavian catheter crossing the midline is most common when a triple lumen catheter is threaded through a larger bore placed in the right subclavian vein. Although not evidence based, many clinicians are comfortable leaving CVCs which terminate in the contralateral subclavian in place, provided there are no clinical effects but are much less at ease with CVCs terminating in the internal jugular vein.

As a general rule it is a good idea to obtain a CXR following failed attempts at CVC placement before attempting insertion on the contralateral side. Doing so reduces the already tiny chance of producing bilateral pneumothoraces. Obviously, this safeguard must be abandoned under truly exigent circumstances where venous access must be obtained immediately.

Every insertion-related complication of CVCs, including pneumothorax, pleural entry, and arterial injury, can result from the placement of the pulmonary artery catheter (PAC). Unique complications of PAC placement include knotting or looping and entanglement with other catheters or pacing wires and pulmonary artery rupture and infarction. Knotting or entanglement of PACs with other catheters is frightening to the less experienced practitioner, but can usually be avoided, and need not be dangerous if a few simple steps are followed. Knotting can largely be avoided by proper insertion technique as outlined in Chapter 2. The basic safety measure is to not advance the catheter more than 20 cm before the next chambers pressure tracing is observed. For example, a right ventricular tracing should be seen with less than 20 cm of catheter advancement after obtaining a right atrial pressure tracing, and a pulmonary artery tracing should be obtained before 20 cm of catheter is inserted after obtaining the right ventricular tracing. Doing so prevents the catheter from forming a large loop in the right atrium or ventricle. If the PAC does become knotted or entangled with another device (e.g., pacing wire or vena caval filter), it is essential to resist the temptation to pull on the catheter harder to extract it; doing so only tightens the knot, making eventual extraction more difficult. Almost always knotted catheters can be “untied” under fluoroscopic guidance simply by loosening the knot, with aid of a stiff internal guidewire. Interventional radiology services are often helpful for disentanglement.

Pulmonary thromboembolism is being recognized with increasing frequency and is now reported in 1% to 10% of PAC placements. The most common radiographic finding is distal catheter tip migration, with or without pulmonary infarction. With an uninflated balloon, the tip of the PAC usually overlies the middle third of a well-centered AP CXR (within 5 cm of the midline). Distal migration is common in the first hours after insertion as the catheter softens and is propelled distally by right ventricular contraction. If pressure tracings suggest continuous wedging, it is important to look for distal migration, as well as a catheter folded on itself across the pulmonic valve or a persistently inflated balloon (appearing as a 1-cm diameter, rounded lucency at the tip of the catheter). Inflation of the balloon of a persistently wedged PAC can result in immediate catastrophic pulmonary artery rupture or delayed formation of a pulmonary artery pseudoaneurysm. Pseudoaneurysms present as indistinct rounded densities on CXR 1 to 3 weeks after PAC placement. The diagnosis is easily confirmed by MRI or contrasted chest CT.

The width of the mediastinal and cardiac shadows should be assessed following placement of PACs and CVCs, because perforation of the free wall of the ventricle may result in pericardial tamponade. Temporary phrenic nerve paralysis due to the lidocaine used in catheter placement rarely precipitates unilateral hemidiaphragm elevation.

When transvenous pacing wires are inserted emergently they are often malpositioned in the coronary sinus, right atrium, or pulmonary artery outflow tract. On an AP view of the chest, a properly placed pacing catheter should have a gentle curve with the tip overlying the shadow of the right ventricular apex. However, it is often difficult to assess the position of the pacing wire on a single film. On a lateral view, the tip of the catheter should lie within 4 mm of the epicardial fat stripe and point anteriorly. (Posterior angulation suggests coronary sinus placement.) In patients with permanent pacemakers, leads commonly fracture at the entrance to the pulse generator, a site that should be checked routinely. Pacing wires can also result in cardiac perforation so it is important to examine the CXR for signs of tamponade.

The optimal position for a chest tube depends on the reason for its placement. Posterior positioning is ideal for the drainage of free-flowing pleural fluid, whereas anterosuperior placement is preferred for air removal. On an AP chest film, posteriorly placed tubes are closer to the film than those placed anteriorly. This proximity of the chest tube to the film results in a “sharp” or focused appearance of the catheter edge and its radiopaque stripe. Conversely, anteriorly placed chest tubes often have fuzzy or blurred margins. Chest tube location may appear appropriate on a single AP film, even though the tube actually lies within subcutaneous tissues or lung parenchyma. Failure to re-expand the pneumothorax or drain the effusion should be a clue to extrapleural placement. Oblique or lateral films or a chest CT may be necessary to confirm appropriate positioning. On plain film, another clue to the extrapleural location of a chest tube is the inability to visualize both sides of the catheter. Chest tubes are constructed with a “sentinel eye,” an interruption of the longitudinal radiopaque stripe that delineates the opening of the chest tube closest to the drainage apparatus. This hole must lie within the pleural space to achieve adequate drainage and ensure that no air enters the tube via the subcutaneous tissue. After removal of the chest tube, fibrinous thickening stimulated by the presence of the tube may produce lines (the tube track), which simulate the visceral pleural boundary, suggesting pneumothorax.

The intra-aortic balloon (IAB) is an inflatable device placed in the proximal aorta to assist the failing ventricle. Diastolic inflation of the balloon produces a distinct, rounded lucency within the aortic shadow, but in systole the deflated balloon is not visible but the underlying catheter is. Ideal positioning places the catheter tip just distal to the left subclavian artery. Placed too proximally, the IAB may occlude the carotid or left subclavian artery. Placed too distally, the IAB may occlude the lumbar or mesenteric arteries and produce less-effective counterpulsation. Daily radiographic assessment is prudent to detect catheter migration or a change of the aortic contour suggestive of IAB-induced dissection.

Whether inserted through the nose (NG) or mouth (OG), it is usually prudent to obtain a CXR to confirm gastric tube position before administration of medication, fluid, or feeding, even when clinical evaluation indicates proper position. Even in intubated patients, a surprising number of tubes intended for the stomach end up in the lung (usually the right mainstem bronchus). Vigorous insertion technique can force the gastric tube through the lung into the pleural space. Inadvertent airway cannulation is most likely to occur when using a small-bore-stylet-stiffened tube, especially when inserted in comatose or deeply sedated patients. When inserted via the esophagus, the side holes of the enteral tube should be fully advanced past the lower esophageal sphincter to minimize reflux. After a percutaneous endoscopic gastric (PEG) tube is placed, an abdominal film should be obtained to search for the most common complications of extragastric placement or peritoneal leakage.

Atelectasis is a frequent cause of infiltration on ICU CXRs. The wide spectrum of findings ranges from invisible microatelectasis, through plate, segmental, and lobar atelectasis, to collapse of an entire lung. Differentiating between segmental atelectasis and segmental pneumonia is often difficult, because these conditions often coexist. However, marked volume loss and rapid onset and reversal are more characteristic of acute collapse.

Atelectasis tends to develop in dependent regions and, more commonly, in the left rather than the right lower lobe by a 2:1 margin. Radiographic findings of atelectasis include hemidiaphragm elevation, infiltration or vascular crowding (especially in the retrocardiac area), deviation of hilar vessels, ipsilateral mediastinal shift, and loss of the lateral border of the descending aorta or heart. Each lobe has a characteristic pattern of atelectasis. With right upper lobe collapse, apical density increases as the minor fissure rotates superior-medially producing an easily recognizable curvilinear arch extending to the mediastinum. Because the left lung does not have a middle lobe or minor fissure, upper lobe collapse occurs anteriorly producing a diffuse haziness of the hemithorax and loss of the upper left cardiac border. In both cases the main pulmonary artery shadow moves cephalad. On lateral CXR, right middle lobe atelectasis appears as a prominent wedge with its apex directed toward the hilum, as the minor fissure and major fissure move toward
each other. Unfortunately, on posterior-anterior (PA) CXR findings are typically much more subtle with only obscuration of the right heart border. Partial collapse of either the right or left lower lobe produces a similar pattern of diaphragmatic silhouetting. When lower lobe volume loss is extensive, a triangular posteriomedial density can be seen with its base resting on the diaphragm. Contrary to popular belief, the “silhouette sign” is not always reliable on portable films, particularly in the presence of an enlarged heart or on a film obtained in a lordotic or rotated projection. Air bronchograms extending into an atelectatic area suggest that collapse continues without total occlusion of the central airway and that attempts at airway clearance by bronchoscopy or suctioning are likely to fail.