A subset of asthma patients are unresponsive to routine therapies and experience acute, severe, even life-threatening exacerbations. Ongoing bronchospasm, inflammatory edema, and mucus plugging critically diminish airway diameter and initiate a cascade of events including hypoxia, hypercapnia, acidosis, lung hyperinflation, increased work of breathing, and ventilatory muscle fatigue; life-threatening cardiovascular depression and respiratory arrest may ensue. In fatal cases, mucus plugging is a routine post-mortem finding.

  1. Koga T, Kawazu T, Iwashita K, Yahata R. Pulmonary hyperinflation and respiratory distress following solvent aspiration in a patient with asthma: expectoration of bronchial casts and clinical improvement with high-frequency chest wall oscillation. Respir Care. 2004 Nov; 49(11):1335-8.
    This case report describes the experience of an 18-year old man with status asthmaticus following accidental inhalation of toluene. The patient presented with severe dyspnea, did not respond to standard treatment [including chest physiotherapy (CPT)] and deteriorated rapidly. Symptoms included a sharp decline in oxygen saturation, rapid, shallow breathing, profuse sweating, and activation of accessory respiratory muscles. Combined treatment with high frequency chest wall oscillation (HFCWO) for airway clearance and BiPAP for ventilatory support resulted in expectoration of a large bronchial cast followed by copious volumes of mucus and additional casts. Authors suggest that HFCWO may have been effective in this patient because of its ability to reduce the viscoelastic and cohesive properties of mucus and to enhance clearability by inducing a cephalad airflow bias in obstructed or plugged airways.
  2. Krishnan JA, Spencer L, Schmidt, L, Bilderback MS, and Diette GB MD, MHS. Feasibility of High Frequency Chest Wall Oscillation (HFCWO) for Treatment of Asthma Exacerbations. Chest 2004; 126 (4): 721S.
    This randomized, controlled, double-blinded trial compared active and sham device high frequency chest wall oscillation (HFCWO) treatments (15 minute treatments, 3X daily) in eight patients hospitalized with asthma exacerbation. Outcomes for adherence, comfort, and perceived benefit were assessed after 4 treatments. Adherence to HFCWO was high (mean 98.1%; range 87% -100%). 100% of participants agreed that the therapy was both comfortable and beneficial.
  3. Naviaux W, Stamey D, Redding G. Factors altering airflow during high-frequency chest wall compression in normal and asthmatic subjects. Am J Respir Crit Care Med 1998; 157 (Suppl 30): A630.
    In this study of oscillatory airway flow measured at the mouth during high frequency chest wall compression (HFCC)/high frequency chest wall oscillation (HFCWO), both normal and asthmatic subjects with significant airway disease showed increased airflow with the addition of inhaled Heliox (30% O2 -70% He mixture) over that achieved when subjects breathed room air. Data suggest that Heliox inhalation during HFCC/HFCWO treatment may augment mucus clearance in some patients.
  4. Wen AS, Woo MS, Keens TG. Safety of chest physiotherapy in asthma. Am J Respir Crit Care Med 1996; 153 (Suppl): A 77.
    In this randomized crossover study, 13 asthma patients received either nebulized bronchodilator (NB) treatment or NB plus high frequency chest compression (HFCC)/high frequency chest wall oscillation (HFCWO) on different days. No episodes of bronchiospasm occurred, suggesting that HFCC/HFCWO administered in conjunction with NB may be used safely in patients with asthma.

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