Air that continually flows from the endobronchial tree to the pleural space is known as a persistent air leak (PAL). Most air leaks do not pose a problem and are not life-threatening. However, in critically ill patients, the presence of a PAL complicates ventilator management and is challenging. Here are the keys to winning the battle…
What are Air Leaks?
Extra-alveolar air can come in many different forms. Most commonly, it can be seen as a pneumothorax, subcutaneous emphysema, pneumomediastinum, or pneumopericardium. It can occur from trauma, surgery, vascular line placement, tumors, or from specific diseases, including, but not limited to, COPD and ARDS. PALs can be identified by either an intermittent (during inspiration) or continuous air leak through a chest tube.
Air leaks in mechanically ventilated patients are associated with an increase in morbidity and mortality. When secondary to barotrauma or direct lung injury, mortality has been reported from 50-60%. The challenge and goal for mechanical ventilation management becomes aimed at techniques to minimize the pressure gradient across the fistula, reduce the leak and allow healing to occur.
To reduce the leak, both inspiratory pressure and PEEP need to be minimized. This will work to minimize peak airway pressure (Paw). Grotberg et al. cited a case study that demonstrated volume loss through a fistula increased from 15% to 54% with the addition of 15 cm H2O PEEP. While pressure control ventilation (PCV) controls peak pressures, caution must be used as it may increase the leak, as it maintains the higher pressure throughout the inspiratory phase of the cycle. Therefore, the use of pressure vs. volume should carefully be considered in determining which mode best minimizes the leak. Leak compensation should be turned off with PAL.
Some patients may need paralysis to reduce air leak and maintain acceptable cardiopulmonary function. An air leak may also increase with spontaneous breathing. Use of pressure support should be used cautiously, as inspiration only terminates when flow is decreased to a certain level and the ventilator may not cycle appropriately if the leak is greater than this level. Additionally, frequent adjustments of cycling criteria may be needed, as well as, trigger sensitivity since suction pressure of the chest tube may trigger the ventilator.
Tidal volumes should be set from 4-8 mL/kg PBW with an inspiratory time between 0.5-0.8 sec. Plateau pressures should be minimized, kept below 28 cm H2O and driving pressure less than 15 cm H2O. Higher FiO2 may be used lieu of higher pressures. Permissive hypercapnia and permissive hypoxemia (PaO2 > 50 mm Hg) should be considered.
Hess and Kacmarek (2019) suggest the following for ventilator management in patients with air leaks. After careful consideration of initial settings
- consider FiO2 adjustments to maintain saturations between 88% – 95%.
- Maintain pH between 7.25 and 7.45 by adjusting the rate.
- If exhaled tidal volumes are less than 75% of inhaled tidal volumes, evaluate and consider changes in tidal volume, frequency, PEEP, inspiratory time, pressure vs. volume and mode of ventilation.
- The presence of persistent air leaks complicates ventilator management
- Air leaks are associated with increased morbidity and mortality
- Identification, monitoring, proper ventilator settings and management are key in minimizing air leaks and optimizing care for patients with air leaks
- Grotberg, J. C., Hyzy, R. C., De Cardenas, J., & Co, I. N. (2021). Bronchopleural fistula in the mechanically ventilated patient: A concise review. Critical Care Medicine, 49(2), 292–301. https://doi.org/10.1097/ccm.0000000000004771
- Hess, D., & Kacmarek, R. M. (2019). Essentials of mechanical ventilation (4th ed.). McGraw-Hill Education.