Interrelation between Alterations in Pulmonary Mechanics and hemodynamics in Acute Myocardial Infarction

Benjamin Interiano; Richard W. Hyde; Morrison Hodges; Paul N. Yu

doi:10.1172/JCI107384

Interrelation between Alterations in Pulmonary Mechanics and hemodynamics in Acute Myocardial Infarction

Benjamin Interiano, Richard W. Hyde, Morrison Hodges, and Paul N. Yu

Published August 1, 1973 - More info

View PDF

Abstract

Pulmonary mechanics were evaluated in 30 patients with acute myocardial infarction by measuring forced expiratory flow rates and total pulmonary resistance (R_T) with the oscillometric method at the resonant frequency of the chest (6-8) cycle/s). During the first 3 days after infarction, forced expiratory volume (FEV) and forced mid-expiratory flow rate (FEF_25-75%) were 69% and 60% of predicted values, respectively. 10 or more wk later these values were 95% and 91%. Initially, R_T was 52% greater than predicted, but was only 4% greater 10 or more wk later. In 11 patients R_T was measured at both resonant frequency and at 3 cycle/s. Five of these patients had no clinical signs of heart failure, but nine had abnormally high values of pulmonary artery pressure, “wedge” pressure and pulmonary extravascular water volume. All of these patients recovered. Initially, R_T at resonance was 50% and R_T at 3 cycle/s was 130% greater than predicted values. 2-3 wk later these figures were -3% and +6% of those predicted, respectively. At 10 wk or more, significant frequency dependence of R_T had disappeared (R_T at 3 cycle/s was 7% greater than R_T at resonance). Isoproterenol inhalation in six patients caused no change in flow rates, R_T at resonance, or R_T at 3 cycle/s. R_T at resonance and at 3 cycle/s, FEV, and FEF_25-75% correlated significantly with the pulmonary vascular pressures. Patients with more marked arterial hypoxia and larger values for extravascular water volume had greater elevations of R_T and depression of FEF_25-75%, but linear correlations were not significant. Clinical signs of congestive heart failure significantly correlated with a fall in FEV and FEF_25-75%, the development of frequency dependence of R_T, and elevation of the pulmonary wedge pressure. The initial elevation of R_T and low flow rates indicate a modest degree of airway obstruction in acute myocardial infarction. Lack of response to isoproterenol suggests that bronchial muscular constriction is not a major factor. Frequency dependence of R_T accompanied by elevated pulmonary vascular pressures and extravascular water volume indicates that pulmonary congestion causes the development of uneven time constants in the airways. Vascular engorgement and interstitial edema from elevated vascular pressures causing narrowing of the peripheral airways and closure of collateral airways could account for the above findings.