Complications/Concerns of Mechanical Ventilation

Ventilator Associated Pneumonia


Saline should never be instilled into ETTs in order to break up secretions because as little as 5 cc can dislodge up to 300,000 bacterial colonies [Am J Crit Care 3: 444, 1994]. NAC can be instilled (direct instillation preferred over aerosol, which is irritative) to break up mucus plugs. Because of its hypertonicity (and potential for bronchorrhea), NAC should only be used as needed and not daily. The “Mucus Slurper” is a new ETT with radially-oriented suction ports that sit above the cuff and which has been shown to be effective in sheep [Intensive Care Med 32:1414, 2006; Crit Care Med Jan 2007: Epub].

Alveolar Rupture

Can produce pulmonary interstitial emphysema, subcutaneous emphysema, pneumomediastinum, pneumoperitoneum, or pneumothorax. Signs and symptoms may be absent, but the most valuable clinical sign is subcutaneous emphysema in the neck and upper thorax. Pneumothorax occurs in 5 – 15% of intubated patients when diagnosed radiographically. Breath sounds are unreliable b/c ventilator equipment distorts them. Portable X-rays can be very difficult because air does not collect in the apex if patients are supine – in supine patients, look for air in the basilar and subpulmonic spaces, which in reality are most elevated. Beware of the redundant skin fold – can produce a radiographic shadow that mimics a pneumothorax.

THE USE OF SUCTION TO EVACUATE PLEURAL AIR IS UNECESSARY AND POTENTIALLY HARMFUL. Traditionally, air was evacuated with a chest tube in the 4th or 5th intercostal space, mid-axillary, advancing anterior-superior and connected to a 3 chamber system (Collection bottle; One way water seal: prevents air from entering into the pleural space, also allows air to be removed (bubbling is a sign of continuous bronchopleural air leak; Suction-control bottle: sets a maximum limit on suction by taking in air).

Occult PEEP (aka auto-PEEP)

High inflation volumes, rapid breathing, and high I:E ratios increase the likelihood, as does COPD (in fact, auto-PEEP is probably unavoidable in COPD patients on AC ventilation). Auto-PEEP can decrease cardiac performance, rupture alveoli, and increase the work of breathing by flattening the diaphragm and moving the lungs towards a less compliant volume (over-distended).

Auto-PEEP can be measured by clamping the tubing at end-expiration and seeing if the proximal airway pressure gauge registers a non-zero value. This is difficult to do. Failure of extrinsic PEEP to increase the peak inspiratory pressure is another sign – the level of extrinsic PEEP that first causes inspiratory pressure to rise is the value of auto-PEEP. It can also be detected (but not measured) by listening fro airflow at end expiration [Am J Repir Crit Care Med 159: 290, 1999]


Preferred in patients who are ventilated for extended periods of time – reduced laryngeal damage (most important indication), more comfortable, more effective clearance of secretions, food can be ingested, and Passy-Muir valve allows speaking. Serious complication rate of 5% with mortality rates as high as 2% in some studies. Immediate complications include pneumothorax, hemorrhage, and decannulation (can reinsert if decannulated within 1 week of operation, using a 12-French suction catheter as a guidewire). The most feared complication, however, is tracheal stenosis.

Timing is controversial. A previously utilized rule of thumb suggested that after 1 week of intubation, if extubation does not appear likely within a week, place the tracheostomy (because the clinical course at one week seems to be predictive of final outcome [Crit Care Med 30: 2450, 2002]). The TracMan trial randomized 909 patient to early tracheostomy (within 4 days) or late tracheostomy (after 10 days if still indicated) and found no difference in the primary outcome (30-day mortality) or other secondary outcomes [Young D et al. JAMA 309: 2121, 2013].

A prospective, randomized, controlled trial of 120 ICU patients showed that mortality was 50% lower in the early percutaneous tracheotomy (within 48 hours) compared with the delayed group (tracheotomy given at 14 – 16 days, if thought to be needed at that time, p < .005). Pneumonia dropped from 25% to 5% (p < 0.005). ICU stay dropped from 16.2 to 4.8 days (p < .001), and days on the ventilator dropped from 17.4 to 7.6 (p < .001). Tracheal stenosis trended to be worse at 10 weeks in the early tracheotomy group but was statistically insignificant [Crit Care Med 32: 1689, 2004]

A metaanalysis of percutaneous vs. open tracheostomy suggested that the percutaneous technique is associated with less bleeding and fewer infections [Chest 118: 1412, 2000]