Thoracoabdominal mechanics in dyspnea.

80 severely ill patients with various lung diseases were studied in order to relate the feeling of breathlessness at rest with the severity of lung mechanical impairment. Moderate to severe dyspnea (grade 2 to grade 3) at rest was present only in 46 of 80 patients (57%) with severe lung disease. The prevalence of breathlessness at rest among the various lung diseases was as follows: 80% in acute bronchial asthma, 70% acute interstitial pneumonia, 50% in diffuse lung fibrosis and 30% in chronic obstructive lung disease. None of the 10 X 9 measured or calculated parameters (IVC, FEV1, FEV1/IVC X 100, TGV, RV, RV/TLC X 100, TLC, MMEF, CC/TLC X 100, SGaw I-E, FV curve indices, quasi-static transpulmonary pressure, dynamic compliance, gastric pressure and RR) seemed to characterize the patients presenting with severe dyspnea. High breathing frequency, low SCdyn and a near negative abdominal pressure consistently identified a small group of subjects with severe dyspnea at rest, regardless of the underlying lung disease.