Progressive neurodegenerative conditions inhibit the normal cough reflex, while chronic obstructive pulmonary disorders such as cystic fibrosis and bronchiectasis alter the production and composition of mucus. Airway obstruction and structural damage result from recurring infection, inflammatory changes and secretion retention.

Technological and clinical advances offer practitioners a variety of expulsion and breathing techniques, manual therapy and medical devices to aid in secretion clearance.This review discusses the various techniques and devices that have demonstrated therapeutic effectiveness for secretion removal.

Review of the Literature The literature offers a plethora of information with regard to airway clearance therapeutic modalities (see Table 1).However,systematic reviews of airway clearance research suggest a number of methodological limitations exist. Small sample sizes, lack of reproducibility, sparse use of sham therapy and reports limited to short-term outcomes with respect to a single treatment session contribute to the lack of evidence to support the use of a particular device or breathing technique. In practice, clinicians must have integral knowledge of airway clearance techniques, the patient s cognitive ability and disease processes, as well as therapeutic goals, in order to devise an effective plan of care.

Cough Assist Techniques and Devices Directed and huff coughing are simplistic techniques used to imitate the attributes of an effective, spon- taneous cough. Directed coughing, also known as quad coughing, involves the manual application external pressure to the epigastric region or thoracic rib cage during exhalation to expel secretions from the airway. It is seldom combined with other airway clearance modalities and is usually employed when mucociliary function is unencumbered and neuro- muscular disease is present.

Huff coughing consists of a series of forced expiratory maneuvers from mid to low lung volumes performed with an open glottis.The intent is to facilitate cephalad movement of sputum through the tracheobronchial tree while minimizing changes in pleural pressure and the probability of bronchial collapse. Unlike directed cough, this technique is rarely used alone. Rather, huff coughing is used as an adjunct to other airway clearance techniques to expel secretions in the final phases of therapy. Huff coughing is often used in place of a spontaneous cough in obstructive disease processes, such as cystic fibrosis, where coughing against a closed glottis results in lower airway collapse.

Mechanical devices can also be used to produce the cough. Mechanical cough assist machines, commonly known as mechanical insufflation exsufflation (MIE) devices, mimic a cough by delivering a positive pressure breath followed by a rapid reversal of airway pressures.The inspiratory maneuver is delivered over a one-second period at pressures of 30 50cm H2O.

Evacuation of that breath immediately follows at pressures of -30 to -50cm H2O. This breath sequencing can be delivered non-invasively (by face mask) or by connection to a temporary or permanent artificial airway (endotracheal or tracheostomy tube).

Initial support for this device was gained in the early 1950s to assist cough generation in polio victims. In recent years, individuals diagnosed with progressive neuromuscular disease have benefited from a resurgence of this therapy to clear secretions and prevent pulmonary compromise.As an added benefit, side effects typically associated with airway clearance therapy in this population, such as bradycardia and hypoxemia, were reported to be minimized.

Conversely, the literature does not substantiate the use of this device with chronic pulmonary conditions in which mucociliary function is compromised.

Secretion Clearance Principles and Practice Teresa A Volsko, MHHS, RRT, FAARC, is Vice President of Respiratory Services at Advanced Health Systems in Hudson, Ohio. She is a member of the Long Term Care Committee and former Chair of the Committee on Community Acquired Pneumonia of the American Association for Respiratory Care (AARC), member of the Board of Trustees and Vice Chair of the Clinical Simulation Committee and Subcommittee on Credentialing Research of the National Board for Respiratory Care, a reviewer and editorial board member of the Respiratory Care Journal and international editorial board member of Update in Respiratory Technology and Applied Technology. Ms Volsko was awarded the 1996 Glaxo-Wellcome Award for the best paper based on a open forum presentation and was made a Fellow of the AARC in 2001. She is guest editor of Respiratory Clinics of North America and author of several peer reviewed manuscripts and book chapters.