July 2002 / Volume 47 / Number 7 / Page 786
Positive Pressure Techniques for Airway Clearance
IntroductionPositive airway pressure (PAP) has been used since the 1930s to improve oxygenation, increase lung volumes and reduce venous return. More recently, PAP has been identified as an effective method of splinting airway during expiration, improving collateral ventilation, increasing response to inhaled bronchodilators, and aiding secretion clearance in patients with cystic fibrosis and chronic bronchitis. A range of devices, administration techniques, and evidence supporting their clinical use is explored, suggesting that PAP is equivalent to postural drainage in the clearance of secretions. PAP produced by threshold and fixed orifice resistors generate different characteristic flow, and airway and esophageal pressure patterns that may contribute to different physiologic effects. Further clinical studies are required to better understand the effects of these differences.
Definitions of Positive Airway Pressure
Continuous Positive Airway Pressure
Expiratory Positive Airway Pressure
Positive Expiratory Pressure
Types of Resistors
Physiologic Rationale for Positive Airway Pressure
Comparison of Flow, and Airway and Esophageal Pressures
Positive airway pressure (PAP) is an effective tool in promoting bronchial hygiene. Since the 1930s, positive airway pressure has been used to improve oxygenation, increase lung volumes, and reduce venous return in patients with congestive heart failure. More recently, positive airway pressure for mobilization and clearance of secretions has captured the attention of the cystic fibrosis community, and a growing body of evidence has evolved to support its use. This review explores how PAP is generated and the theoretical and empirical basis for its use as a secretion clearance technique.