Vol. 12 •Issue 2 • Page 59
Wide Spectrum of Airway Clearance Techniques Helps to Improve Patients’ Lives
For more than 40 years, chest physiotherapy has been the standard modality for airway clearance. However, it has drawbacks. Conditions, such as osteoarthritis, surgical incisions and thoracic cage tenderness, limit the applicability of percussion and vibration. Although an effective cough is critical for secretion clearance, uncontrolled cough can precipitate airway collapse, bronchospasm or syncope in susceptible patients.
In the home, CPT often requires the assistance of a second person. It also can contribute to the development of carpal tunnel syndrome in health care workers who perform percussion and vibration multiple times daily. Performing CPT can be fatiguing, and techniques vary from one therapist to another. Mechanical chest percussors, which simulate the cupping action of the therapists’ hands, can alleviate these problems.
In recent years, alternative methods of secretion mobilization have emerged that enhance the health and quality of life in patients with pulmonary disease. To choose the most appropriate airway clearance technique, consider patient motivation, goals, age, ability to concentrate, fatigue, need for equipment/personnel, limitations, costs and desirability of combining methods.
POSITIVE EXPIRATORY PRESSURE
Positive expiratory pressure (PEP) mobilizes secretions without the risks or limitations of CPT. PEP increases expiratory pressure as the patient actively exhales through an expiratory resistor. He or she uses a mask or mouthpiece, a one-way valve, an expiratory port with a variable resistance and a manometer. (See Sidebar.)
The patient should perform diaphragmatic breathing and inspire to a volume of air larger than normal tidal volume, but not to total lung capacity. Exhalation should be to functional residual capacity, active yet not forced, and through the fixed orifice resistor chosen to achieve a PEP of 10 cm H2O to 20 cm H2O.
PEP prevents airway collapse during exhalation. When positive pressure is applied, the exhalation continues, carrying secretions more centrally into the lung where they are more easily expectorated.
A small hand-held device is available that combines PEP with high-frequency oscillations. This accelerates expiratory airflow, facilitating upward movement of mucus.
Cardiovascular exercise training also is valuable. It improves overall aeration and ventilation, or perfusion ratio. It can increase sputum production, improve pulmonary function and fitness and improve self-esteem. Because exercise is encouraged for healthy living, increased activity helps normalize the respiratory patient’s life, rather than add a therapy that would accentuate differences from peers.
When prescribing exercise, it’s important to include warm-up and cool-down periods. Don’t forget to consider hydration and the possibility of exercise-induced asthma.
Breathing exercises help patients with mucociliary clearance. Active cycle of breathing techniques is a cycle of breathing control, thoracic expansion exercise and forced expiration technique. During breathing control, the patient gently breathes using the lower chest while relaxing the upper chest and shoulders. Thoracic expansion requires breathing deeply, exaggerating inspiration, and exhaling slowly and quietly. Forced expiration technique includes performing a “huff” maneuver — coughing from the chest rather than the throat — to expectorate mucus.
Blowing bubbles, blowing out candles, blowing up balloons or playing wind instruments are simple breathing exercises that are enjoyable and encourage compliance, especially in children.
CHEST WALL OSCILLATION
Patients also can use an air-pulse generator attached to an inflatable vest that covers the entire thorax. When the generator is turned on, the pressure in the vest increases and decreases between five and 25 times per second. The procedure, known as high frequency chest wall oscillation (HFCWO), applies rapid oscillations to the patient’s chest wall.
During the first half of its cycle, the vest used at this time inflates rapidly, compressing the chest and airways, producing a high expiratory flow. During the second half of the cycle, the vest deflates, allowing the chest and airways to rebound, producing a relatively higher expired flow. Together these make up one oscillating cycle, which can repeat up to 25 times per second.
HFCWO increases airflow at low lung volumes, produces cough-like forces, decreases mucus tenacity and, consequently, increases mucus mobilization. Because the vest mechanism isn’t reliant on gravity, it provides effective airway clearance independent of postural drainage.
Autogenic drainage uses three stages of controlled exhalation to mobilize secretions. Patients first breathe at low lung volumes to loosen peripheral mucus, and then breathe at middle lung volumes to move the mucus to the central airways. Finally, they breathe at mid to high volumes to evacuate the mucus from the central airways. Patients use sensory and auditory signals to adjust inhalation speed. Once mastered, autogenic drainage can be performed independently and is an effective method of airway clearance.
Assisted cough calls for the therapist to place the palms of both hands on the patient’s abdomen. As the patient exhales, the therapist pushes inward and upward, under the thorax. Repetition assists in sputum expectoration.
When manual methods are insufficient, cough simulating devices are available that alternate positive and negative pressure to achieve effective expiratory cough flow.
Incentive spirometry encourages sustained maximal inspiration and can prevent and treat atelectasis. It allows patients to visualize their progress by moving a ball or disc as they inhale at a predetermined flow rate or volume.
Although airway clearance is tremendously important, compliance is often poor. Increased age, poor nutrition, poor pulmonary function and poor perceived quality of life are associated with low adherence to airway clearance. Insurance and gender appear to play no part in compliance. It remains unclear whether poor health leads to less compliance, or if better health results from compliant patients.
A multidisciplinary care team must examine the patient and determine appropriate interventions, implement a care plan and periodically re-evaluate the effectiveness of the interventions.
Hyman is pulmonary education specialist with Children’s Healthcare of Atlanta.
Positive Pressure Techniques for Airway Clearance
Positive airway pressure bronchial hygiene techniques have emerged as effective alternatives to chest physical therapy in expanding the lungs and mobilizing secretions.1,2
Continuous positive airway pressure (CPAP), positive expiratory pressure (PEP) and expiratory positive airway pressure (EPAP) are all forms of PAP. PAP therapy is more effective in treating atelectasis than incentive spirometry and intermittent positive pressure breathing (IPPB) and has been shown to enhance response to aerosol bronchodilator delivery.3-6 Forced expiratory technique, active cycle of breathing and huff cough are essential components of effective PAP therapy in mobilizing secretions.
Pursed-lip breathing is a natural adaptation to air trapping and the predecessor to modern strategies of applying positive expiratory pressure to the airway. Pursed-lips breathing is performed by many patients with chronic obstructive lung disease who have taught themselves to relieve air trapping caused by collapse of unstable airways during expiration. The pursed lips form a fixed orifice resistor so that the resistance at the mouth transmits back pressure to splint the airways open, preventing compression and premature closure.7,8
As early as 1936, the use of the positive pressure mask for the treatment of congestive heart failure and cardiogenic pulmonary edema was described.9 Interest in the use of CPAP for lung expansion or mobilization of secretions began in the early 1980s, and several studies compared it to incentive spirometry, deep breathing and coughing.10,11 Researchers concluded that intermittent mask CPAP was as effective as incentive spirometry or deep breathing and coughing in return of pulmonary function following thoracic or upper abdominal surgery.12,13
POSITIVE EXPIRATORY PRESSURE
By preventing expiratory collapse, PEP promotes more homogenous distribution of ventilation throughout the lung via collateral interbronchiolar channels.2 Researchers reported increased functional residual capacity from 2.6 L to 3.6 L and 4.4 L and an increase in total lung capacity from 5.1 L to 5.9 L and 6.9 L, with use of a 5 cm H2O and 15 cm H2O threshold resistor, respectively. Volumes returned to normal when pressure was removed from the airway.14
When comparing CPT to PEP therapy, PEP has come out on top in research studies. For example, researchers randomly assigned 40 patients, ages 6 to 17 years, to perform CPT or PEP therapy for a one-year period.15 In the CPT group, pulmonary function declined in all parameters, while the PEP group had positive changes in FEV1 (p=0.02) and FVC (p=0.02).
Equipment for PEP therapy consists of a mask or mouthpiece, T-piece with a one-way valve, a variety of fixed orifice resistors (or adjustable expiratory resistor) and a manometer.16 PEP therapy is typically performed with the subject seated comfortably, elbows resting on a table.
The subject is instructed to relax while performing diaphragmatic breathing, inspiring a volume of air larger than normal tidal volume but not to total lung capacity, through the one-way valve. Exhalation to functional residual capacity is active but not forced, through the resistor chosen to achieve a positive airway pressure between 10 cm H2O to 20 cm H2O during exhalation.
A series of 10 breaths to 20 breaths are performed with the mask or mouthpiece in place. The mask (or mouthpiece) is then removed, and the individual performs several directed coughs to raise secretions. This sequence of 10 PAP breaths to 20 PAP breaths followed by huff or forced expiration technique coughing is repeated four to six times per PEP therapy session. Each session for bronchial hygiene takes from 10 minutes to 20 minutes and may be performed one time per day to four times per day.
The key to successful therapy is selection of an appropriate fixed orifice resistor between 2.5 mm to 4.0 mm in diameter to achieve a positive expiratory pressure between 10 cm H2O to 20 cm H2O, with an inhalation/exhalation ratio of 1-3 to 1-4. Adults achieve this pressure range utilizing a flow restricting orifice. A manometer placed in-line can measure the expiratory pressure to select the appropriate sized orifice. After a resistor is found that generates peak pressures of 10 cm H2O to 20 cm H2O, the manometer isn’t necessary.
When an orifice is too small, the expiratory phase is too long, and pressure can rise to above 20 cm H2O, increasing the work of breathing. Too large an orifice results in low pressure and a short exhalation. Sicker patients are encouraged to increase the frequency of PEP sessions rather than extend the length of individual sessions.
Sinusitis, ear infection, epistaxis, or recent facial, oral, or skull injury or surgery may be a problem, and should be considered before a decision is made to initiate PEP mask therapy. Active hemoptysis or unresolved pneumothorax are absolute contraindications for PAP therapy. To date, no complications of PEP have been reported.
Fink is the fellow of respiratory science at Aerogen Inc., Mountain View, Calif.
For a list of references, please call Debra Yemenijian at (610) 278-1400, ext. 1153, or visit www.Respiratory-care-sleep-medicine.advanceweb.com/mrreflist.html.