The Effect of Exercise on Lung Distensibility and Respiratory Work in Mitral Stenosis

Abstract

The selection of patients with mitral stenosis for valvotomy is considerably influenced by the degree of dyspncea of which the patient complains, and in many cases the history of progressive dyspncea with episodes of acute pulmonary cedema or haemoptysis makes the need for operation obvious. In some cases, however, fatigue is confused with dyspncea as a reason for limiting physical activity or the synmptoms of the effort syndrome may be superimposed so that some objective measurement of the degree of disability might be of value. Attempts to correlate the degree of dyspncea with the circulatory changes in the heart and lungs, measured by means of the cardiac catheter, or with results of tests of respiratory efficiency have given conflicting results. Most of these studies have been carried out with the patient at rest but even when repeated during steady exercise the same lack of correlation has been reported (West et al., 1953).Pathologists have long been familiar with the fact that the lungs of patients dying in heart failure were more rigid than normal lungs, but it was not until 1934 that Christie and Meakins (1934) measured in vivo the distensibility of the lungs in patients with congestive heart failure by means of simultaneous tracings of the tidal air and the intrapleural pressure fluctuations. They showed that in heart failure the lungs were more rigid than normal, probably because of pulmonary congestion, and that with clinical improvement the distensibility of the lungs improved. There was thought to be a direct relationship between the degree of lung rigidity and the amount of dyspncea and it was later suggested that cardiac dyspncea was reflex in origin, the increased lung rigidity through the Hering-Breuer reflex causing the rapid shallow breathing of heart failure (Christie, 1938). Because of the necessity of inducing a small pneumothorax to record the changes in intrapleural pressure little use has been made of the method of Christie and Meakins (1934) of measuring the pulmonary distensibility in cardiac patients. Dornhorst and Leathart (1952) have shown that an accurate record of changes in intrathoracic pressure can be obtained by recording the pressure changes in the cesophagus and this method has been used to study on a larger scale changes in lung distensibility and respiratory work in heart failure (Marshall et al., 1954).If the degree of cardiac dyspncea is directly related to the increased rigidity of the lungs, the measurement of pulmonary distensibility might be of help in assessing the amount of disability. In this investigation the relationship between dyspncea and pulmonary distensibility and respiratory work has been studied in 30 patients with mitral stenosis. Measurements were made at rest, and during and immediately after exercise, and in 6 patients were repeated 3-6 months after mitral valvotomy. METHODSChanges in intrathoracic pressure were measured using an cesophageal catheter and these were recorded simultaneously with records of the tidal air obtained with the pneumotacho...

Pulmonary Function in Pulmonary Hypertension

“…As would be expected, lung complance was reduced in the patient ral valve disease (Marshall et al, 1954;Hayward and Knott, 1955), and also in the patient with pulmonary fibrosis (Case 18) in whom the inspiratory resistance was also raised. In two patients with congenital heart disease, in whom there was a history of associated lung disease (Cases 7 and 22), the mechanical properties of the lungs were also grossly abnormal.…”

The resistive and elastic work of breathing during exercise in patients with chronic heart failure

“…It should be noted that these parameters are not indicative of respiratory muscle work per se , but rather provide an index of respiratory muscle blood flow and oxygen uptake [37, 38]. Others have determined the W b in HF patients using P oes – V T loops obtained during exercise [8, 9, 11, 39]. However, these studies often neglected the elastic work incurred by movement of the chest wall and, therefore, may have underestimated the total W b in these patients.…”

“…We interpret the above findings to represent an increased inspiratory and expiratory resistive load to breathing in HF patients during physical activity. Such an increased resistive load to breathing in HF patients may arise from the development (or progressive worsening) of pulmonary congestion and/or an increased bronchomotor tone during graded exercise [8, 19, 41]. …”

“…[4–7]. Accordingly, the energetic demands of exercise for HF patients may be compounded by an inordinately high work of breathing ( W b ) for a given level of minute ventilation ( V ′ E ) and external work [8, 9]. This heightened W b necessitates greater oxygen delivery to the respiratory muscles, potentially at the expense of oxygen supply to the locomotor muscles, impairing the patient’s ability to perform muscular work [10, 11].…”

The interactions between respiratory and cardiovascular systems in systolic heart failure

“…The mechanical work contributed by the respiratory muscles is inordinately higher in HF patients during physical activity (22,27,36,59,70). There are two primary factors which contribute to this greater overall mechanical cost of breathing in HF: 1) exercise hyperventilation; and 2) mechanical derangement.…”