Hyperinflation dynamic

Calverley PM, Koulouris NG. Flow limitation and dynamic hyperinflation key concepts in modern respiratory physiology. Eur Respir J 2005 25(1) 186-199. 

Kimball WR, Leith DE, Robins AG. Dynamic hyperinflation and ventilator dependence in chronic obstructive pulmonary disease. Am Rev Respir Dis 1982 126(6) 991-995. 

Exercise limitation and functional disability in COPD have a complex, multifactorial basis. Ventilatory limitation is caused by increased airways resistance, static and dynamic hyperinflation, increased elastic load to breathing, gas exchange disturbances, and mechanical disadvantage and/or weakness of the respiratory muscles (4-6). Car-diocirculatory disturbances (7,8), nutritional factors (9), and psychological factors, such as anxiety and fear, also contribute commonly to exercise intolerance. Skeletal muscle dysfunction is characterized by reductions in muscle mass (10,11), atrophy of type I (slow twitch, oxidative, endurance) (12,13) and type Ila (fast twitch) muscle fibers (14), altered myosin heavy chain expression (15), as well as reductions in fiber capillarization (16) and oxidative enzyme capacity (17,18). Such a dysfunction is another key factor that contributes... 

O Donnell DE, Revill SM, Webb KA. Dynamic hyperinflation and exercise intolerance in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2001 164 770-777. 

The patients who required a tracheostomy may subsequently manage spontaneous ventilation with improvements in their underlying condition and respiratory muscle strength and endurance. Resolution of dynamic hyperinflation also improves the length-tension relationships of the inspiratory muscles (56). Strengthening of the upper extremities or the inspiratory muscles has provided mixed results (57,58). 

Careful patient selection prevents unsafe levels of alveolar hypoventilation with subsequent hypoxemia and hypercapnea, especially if the tidal volume leakage is >20%. Any compensatory increase in respiratory rate and shortened expiratory time, attributable to the air leakage, may aggravate dynamic hyperinflation, especially among patients with airflow obstruction (15). Ventilator-supported speech has been reported in patients with neuromuscular diseases (NMD) and intact bulbar function (16-19). The physiologic characteristics that enable this population to tolerate ventilator-supported speech include little or no decrease in chest wall or lung compliance and the absence of airflow obstmction. Therefore, patients with NMD may be ventilated with a deflated or cuffless tracheostomy tube accepting the modest compromise in alveolar ventilation (16,20-22). Patient populations, such as those with chronic obstructive pulmonary disease may be able to tolerate cuff deflation for short periods provided there is adequate supervision. 

---