Chest Physiotherapy and Cystic Fibrosis: Oral High-Frequency Oscillation and High-Frequency Chest Compression
Piper et al (1992) investigated the use of nocturnal nasal intermittent positive pressure ventilation in a group of four CF patients presenting with hyper-capnic respiratory failure that proved refractory to conventional therapy. Nocturnal nasal intermittent positive pressure ventilation was tolerated by all subjects and resulted in improved blood gas values, a lessening of severe dyspnea, and an improvement in their level of daily activities. In addition, each patient was better able to tolerate daily physiotherapy and two reported improved secretion clearance. The application of nocturnal ventilatory support in the areas of pulmonary rehabilitation and prolongation of the life of patients awaiting heart-lung transplant appears promising and will no doubt be the subject of further investigation throughout the 1990s. asthma mist asthma relief
Oral high frequency oscillation (OHFO) is a modification of the original high-frequency ventilation in which sine wave oscillations in gas flow are produced in the airways via an external pump. Whereas high-frequency ventilation was found to result in a retrograde movement of secretions, OHFO has been shown to increase mucociliary clearance and reduce minute ventilation when superimposed on normal tidal breathing in normal subjects. The mechanism by which OHFO increases mucociliary clearance is unclear, though possibilities include altered mucus rheology, production and airway responses, and facilitation of the intrinsic vibratory action of the bronchial walls.
Studies investigating the effects of OHFO as an adjunct to respiratory physiotherapy are scarce. George et al (1986) compared the use of OHFO alone to OHFO and PD with FET and to PD with FET alone in a group of seven CF adults. Secretion clearance was measured via radioactive aerosol clearance and wet weight of sputum expectorated. While all three treatment groups showed a trend toward improved secretion clearance, only OHFO combined with PD and FET reached statistical significance. However, Pryor et al (1989) could show no additional advantage in including OHFO in physiotherapy compared with physiotherapy alone in a group of patients with chronic bronchitis and airflow limitation.