Recognizing the Correct Placement of Lines and Tubes and Their Potential Complications: Critical Care Radiology

Endotracheal Tubes (ETT)

• Why they are used

  • Assist ventilation

  • Isolate the trachea to permit control of the airway

  • Prevent gastric distension

  • Provide a direct route for suctioning

  • Administer medications

• Correct placement of an ETT

  • Endotracheal tubes are usually wide-bore tubes (about 1 cm) with a radio-opaque marker stripe and no side-holes. The tip is frequently diagonally shaped.

  • With the patient’s head in the neutral position (i.e., bottom of mandible is at the level of C5-C6), the tip of the ETT should be about 3 to 5 cm from the carina or roughly half the distance between the medial ends of clavicles and the carina ( Fig. 9.1 ).

    

• Ideally the diameter of the endotracheal tube should be one-half to two-thirds the width of trachea. An inflated cuff (balloon), if present, may fill—but shouldn’t distend—the lumen of the trachea ( Fig. 9.2 ).

  

Important Points

• How to find the location of the carina on a frontal chest radiograph

  • Follow the right or left main bronchus backward until either meets the opposite main bronchus.

  • Alternatively, the carina projects over the T5, T6, or T7 vertebral bodies in 95% of people.

• Movement of tip with flexion and extension

  • Neck flexion may cause 2 cm of descent of the tube tip. This is why the tip should be 3 to 5 cm above the carina.

  • Neck extension from neutral may cause 2 cm of ascent of the tip.

  • There is a silly, but helpful, rhyming sentence to help remember the direction of movement of the tip of an ETT with movement of the head: “The tip of the hose (i.e., ETT) follows the tip of the nose. ”

• Incorrect positioning and complications of an ETT

  • Most common malposition: because of the shallower angle and wider diameter of the right main bronchus or bronchus intermedius, the tip of the ETT will tend to slide into the right-sided bronchial tree preferentially to the left.

    • This can lead to atelectasis (especially of the nonaerated right upper lobe and left lung) (see Case Quiz 6).

    • Intubation of the right main bronchus could also lead to a right-sided tension pneumothorax .

  • Inadvertent esophageal intubation will produce a dilated stomach.

  • The tip of the tube should not be positioned in the larynx or pharynx as damage to the vocal cords can occur ( Fig. 9.3 ).

    

Tracheostomy Tubes

• Why they are used

  • In patients with airway obstruction at or above level of larynx

  • In respiratory failure requiring long-term intubation (>21 days)

  • For airway obstruction during sleep apnea

  • When there is paralysis of the muscles that affect swallowing or respiration

• Correct placement of a tracheostomy tube ( Fig. 9.4 )

  • The tip should be about halfway between the stoma in which the tracheostomy tube was inserted and the carina. The carina is usually around the level of T3.

  • Unlike an ETT, the placement of the tip of a tracheostomy tube is not affected by flexion and extension of the head.

  • The width of the tracheostomy tube should be about two-thirds the width of trachea.

  

• Incorrect placement and complications of a tracheostomy tube

  • Immediately after insertion look for signs of inadvertent perforation of the trachea such as pneumomediastinum, pneumothorax, and subcutaneous emphysema.

  • If the tracheostomy tube is equipped with a cuff , the cuff should generally be inflated to a diameter that fills , but does not distend, the normal tracheal contour.

  • Long-term complication of tracheostomies:

    • Tracheal stenosis is the most common late-occurring complication of a tracheostomy tube and can occur at the entrance stoma, level of the cuff, or at the tip of tube, but is most common at the stoma .

Central Venous (Pressure) Catheters (CVC, CVP)

• Why they are used

  • For venous access to instill chemotherapeutic and hyperosmolar agents not suitable for peripheral venous administration

  • Measurement of central venous pressure

  • To maintain and monitor intravascular blood volume

• Correct placement of central venous catheters

  • Central venous catheters have a small diameter (3 mm) and are uniformly opaque without a marker stripe.

  • Their correct placement is shown in Fig. 9.5 and Fig. 9.6 .

    
    

• Incorrect placement and complications of central venous catheters

  • Central venous catheters are most often malpositioned with their tips in the right atrium or internal jugular vein ( Fig. 9.7 ). In the right atrium, they can produce cardiac arrhythmias. When central venous catheters are malpositioned, they may provide inaccurate central venous pressure readings.

    

  • Pneumothorax can occur in up to 5% of CVC insertions, more often with the subclavian approach than the internal jugular route.

  • All bends in the catheter should be smooth curves. Occasionally CVCs may perforate the vein and lie outside of the blood vessel. Look for sharp bends/kinks in the catheter as a clue to a potential perforation.

  • Sometimes, they may be inadvertently inserted in the subclavian artery rather than the subclavian vein. Suspect arterial placement if the blood return is pulsatile upon placement and the course of the catheter follows the aortic arch or fails to descend to the right of the spine ( Fig. 9.8 ).

    

Important Points

• Two or more attempts at inserting a CVC

  • A frontal chest radiograph is obtained following placement of a CVC. Should initial placement fail , it is customary to obtain a chest radiograph before trying insertion on the other side to avoid the possibility of producing bilateral pneumothoraces.