July 2002 / Volume 47 / Number 7 / Page 808
Airway Clearance Techniques for the Patient with an Artificial Airway
IntroductionArtificial airways provide both opportunities and challenges to clinicians concerned with airway clearance. For example, the artificial airway provides direct access to the lower airways for catheter suctioning of secretions and a direct route for lung instillation of medications that promote secretion mobilization. At the same time, the presence of an artificial airway impairs natural mechanisms of airway clearance -- coughing and mucociliary function. Artificial airways are invariably coated with an antibiotic-resistant bacterial biofilm that can be introduced into the lung by several commonly applied airway clearance techniques. This factor is rarely considered during research on airway clearance techniques for patients with artificial airways. This review summarizes current research on airway clearance techniques for patients with artificial airways, with special attention to the implications of the bacterial biofilm. Directions for future research are also discussed.
Effects of Artificial Airways on Mucus Clearance
Impaired Mucus Transport
Increased Risk of Aspiration
Abnormal Bacterial Colonization
Goals of Airway Clearance Techniques with the Intubated Patient
Prevent Catastrophic Obstruction of the Endotracheal Tube
Prevent or Reduce Peripheral Airway Obstruction
Reduce Infectivity of Secretions
Components of Airway Clearance Strategies
Prevent Secretion Dehydration
Reduce Upper Airway and Gastrointestinal Tract Bacterial Colonization
Prevent Secretion Accumulation above the Endotracheal Tube Cuff
Prevent Aspiration of Secretions from the Supra-Cuff Space
Prevent Development of Biofilm
Prevent Disruption and Aspiration of the Biofilm
Maintain Patency of the Central Airway
Compensate for Lack of Normal Cough
Compensate for Lack of Spontaneous Position Change
The presence of an endotracheal tube (ETT) impairs the body's normal mechanisms of airway clearance. In addition, placement of an ETT increases the risk of pulmonary infection, in part because of the development of a bacteria-rich biofilm on the interior and exterior surfaces of the tube. Some generally accepted methods of secretion removal in the intubated patient, such as endotracheal suction, can disrupt the biofilm and introduce bacteria into the lower airway. Other airway clearance techniques, such as chest wall percussion and vibration, may have a similar effect. Introduction of bacteria into the airway of a critically ill patient can result in a tissue-damaging inflammatory process, as well as life-threatening pneumonia. Studies of airway clearance techniques applied to the intubated patient must therefore include nosocomial pneumonia as a major outcome variable, as well as the more immediate effects of airway clearance procedures on other variables, such as sputum volume and lung mechanics.
Bacterial infection of the airway can also trigger a systemic inflammatory response, which can result in additional morbidity and extra-pulmonary organ dysfunction. These effects may be hard to anticipate and identify, but their presence could be inferred from differences in overall mortality, length of stay, and hospital expenditures. These variables are rarely addressed in studies of airway clearance techniques applied to the intubated patient. This review therefore is written from the perspective that airway clearance techniques must be evaluated not only by measuring such factors as volume of sputum produced and changes in pulmonary function, but by broader measures, such as total mortality and length of intensive care unit (ICU) stay.
An evaluation of airway clearance techniques for the intubated patient must also recognize the role of upper airway bacterial colonization in the pathogenesis of ventilator-associated pneumonia (VAP). Therefore, this review is written from the perspective that minimizing bacterial colonization of all structures in the airway (including the teeth and sinuses) must be addressed when evaluating airway clearance techniques.