Chest Physiotherapy and Cystic Fibrosis: Autogenic Drainage
Autogenic drainage is a form of self-drainage using controlled breathing techniques to alter the rate and depth of ventilation The aim of AD is to reach the highest possible airflow in different generations of bronchi while finding the balance between expiratory flow, existing intrabronchial pressure, and the stability of the bronchial walls. When compared with conventional CPT and the positive expiratory pressure (PEP) mask, AD increased secretion clearance and improved pulmonary function in CF subjects. This technique assumes that all subjects present with “unstable airways,” that the subject can reliably alter the rate and depth of ventilation and sensitively detect the location of secretions, and that pressure differences within the lung can be equalized by pausing at end inspiration. The technique also requires extended supervision to learn and at least 30 to 45 min twice a day to perform. Pulmonary function tests have been used to show alterations in ventilation, but no evidence is available currently to show the “unsticking” and mobilizing of secretions by these fluctuations in ventilation. canadian neighbor pharmacy
Dab and Alexander (1977) investigated the effects of AD on 14 children with asthma with excessive secretion production. Specific airway resistance was monitored after treatment to show that removal of secretions resulted in a lowering of airways resistance. While specific airway resistance generally decreased after treatment, this measure was not statistically significant. Of the 62 tests conducted in this study, 9 tests were rejected because AD resulted in an acute asthmatic attack. The authors concluded that any bronchospasm was a result of the forced expiration maneuvers or the cough component, or both, or errors in the execution of the technique.
Recently, Miller et al (1993) conducted a randomized two-day crossover trial, comparing the effects of AD with the ACBT on PFTs, oxygen saturation, heart rate, sputum weights, ventilation distribution, and isotopic clearance in a group of 18 CF subjects. Autogenic drainage was found to improve small airway function and resulted in significantly greater isotopic clearance than the ACBT, but no other significant differences were noted. While group differences were generally not significant, individual responses to the two techniques were varied.