Lung disease hyperinflation

O Donnel DE, Lam M, Webb KA. Measurement of symptoms, lung hyperinflation, and endurance during exercise in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1998 158 1557-1565. 

Several clinical conditions that adversely affect lung function have to be excluded before diagnosing BOS (e.g., infection, acute rejection, bronchial anastomotic problems, disease recmrence, aging, native lung hyperinflation, disease progression, and factors that induce a restrictive defect such as pleural disease, steroid myopathy, pain, etc.) (14). 

In individual patients, however, both types of respiratory failure may coexist, as one respiratory problem leads to another with a cascade of interaction (3). For example, patients with cardiogenic pulmonary edema or status asthmaticus first develop hypoxemia due to lung failure if the disease persists or progresses, pump failure and hypercapnia appear because of several mechanisms (increased work of breathing, reduced oxygen delivery, hyperinflation). 

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. 

In established pulmonary disease, the chest radiograph is usually abnormal. The most common abnormalities are a reticular pattern, micronodules (measuring up to 2 mm in diameter) and cysts (Lacronique et al. 1982). There is no obvious predilection for the central or peripheral lung. A useful diagnostic clue on chest radiographs (but not necessarily confined to cases of LCH) is that, despite the apparently extensive interstitial disease, lung volumes may be preserved or, in some patients, even increased (Lacronique et al. 1982) (Fig. 4.3). Indeed, hyperinflation becomes... 

Hyperinflation of the native lung is a specific problem of recipients of a single lung for COPD. Due to the progression of the underlying disease the obstruction increases and subsequent air trapping re-... 

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