Effects of Pulmonary Vascular Congestion on Postural Changes in the Perfusion and Filling of the Pulmonary Vascular Bed*

Abstract

Measured by a variety of techniques, the overall ventilation-perfusion relationship of the normal human lung is different in supine and upright positions, and in the upright position, the upper regions of the lung are relatively poorly perfused (1-4). Similarly, pulmonary diffusing capacity (DL) is reduced when normal subjects change from supine to upright positions (5, 6); in the upright position, carbon monoxide absorption is greater in the lower portions of the lung than in the upper portions (7). These differences are probably related to a gravity dependent gradient of perfusion and capillary filling caused by the inability of the normally low pulmonary arterial pressure to provide uniformly adequate perfusion against the hydrostatic gradient that must be present in the pulmonary vascular bed of normal adult humans in an upright position (2,8).The present investigation was undertaken to determine a) whether the normal postural changes in physiologic dead space and diffusing capacity are present in patients in whom the pulmonary vascular pressure should be great enough to insure perfusion of the entire lung in the upright position and b) whether an acute increase in pulmonary vascular pressures affects the arterialalveolar CO2 gradient and alveolar dead space of normal men in an upright position. MethodsThirty-four adult patients having clinical cardiac catheterizations and 20 trained normal subj ects were * Submitted for publication July 8, 1963; accepted September 19, 1963. This study was supported in part by research grants H-6228 and H-4080 from the National Heart Institute, U. S. Public Health Service, Bethesda, Md., and in part by U. S. Air Force contract 33(616) 8378.t Fellow, Indiana Heart Association. used in this study. The patients' surface areas, pulmonary vascular pressures, and diagnoses are listed in Table I. Those patients with mean pulmonary arterial pressure greater than 20 mm Hg are grouped separately and are considered to have pulmonary hypertension. With few exceptions, all patients with pulmonary hypertension had mitral valvular disease. The normal subjects were healthy men whose ages were between 22 and 36 and whose mean surface area was 1.89 ± 0.4 in'. Their pulmonary vascular pressures were assumed to be normal.Tilting was performed on a motor-driven tilt table. Measurements were made in random sequence; subjects were flat or tilted 600 with their heads up. The change in lung volume that occurred during tilting was measured with a bag-in-box spirometer system, in which a steady base line is obtained during spontaneous breathing before and after a change in position, the recorded difference representing the difference in lung volume in the two positions. Measurements of physiologic dead space were begun 15 to 30 seconds after the subjects reached the 600 position. During a different tilt, diffusing capacity was measured 1 minute after reaching the 60°p osition. The effect of acute pulmonary vascular engorgement on alveolar dead space and arterial-alveolar Pco, gradient was studied in...

Maximal Diffusing Capacity of the Lung for Carbon Monoxide*

“…Our results confirm those of Newman, Smalley, and Thomson (13) (14)(15)(16)(17). However, in the present investigation the pulmonary capillary blood volumes were no greater in three patients with mitral stenosis working at full capacity than in normal subjects exercising (Figure 2), and the results obtained by other investigators who have measured Vc in patients with pulmonary congestion (15)(16)(17) are in essential agreement with our own (Figure 3).…”

“…The anatomical estimates of Vc are within the same range as those found by physiologic measurements in normal subjects at peak exercise and in patients with -pulmonary congestion. The patients with pulmonary congestion studied by Daly and co-workers (14) had mitral stenosis and as a group had an average left atrial pressure of 23 mm Hg. The patients studied by Bucci and Cook had high pulmonary blood flows due to interatrial septal defects plus some associated obstruction to left ventricular filling (15 …”

The Effect of Transfusion on Lung Capacity, Diffusing Capacity, and Arterial Oxygen Saturation in Patients with Thalassemia Major

“…A likely explanation for the increase in Go is an increase in pulmonary capillary blood volume (1 3). This may be associated with a more uniform interregional distribution of pulmonary capillary volume after transfusion in a manner similar to that which has been shown to occur with a change from the upright to the supine posutre (4,14,15). In addition, Daly et al (14) showed an increase in pulmonary diffusing capacity associated with use of an inflation suit which forced a shift in blood volume to the lungs.…”

The Diabetic Lung - A New Target Organ?

“…It is well known that in normal subjects the increase in DLCO in the supine, compared to the sitting position, is related to the recruitment of the upper lobe pulmonary capillaries, thus increasing the total volume of pulmonary blood volume [59,60]. Although normal when measured in sitting position, DLCO did not increase with a change from sitting to supine position in patients with type 1 diabetes, compared to healthy subjects [61].…”

“…It is also conceivable that the abovementioned functional deficits can depress the host defense of the airways and the mucociliary clearance, thereby helping to promote the development of lower respiratory tract infections and/or to delay healing. Finally, the derangements of the autonomic innervation with consequent reduction of both peripheral and central chemosensibility may be involved in the altered perception of breathlessness and in anomalous patterns in the ventilatory response to exercise, as frequently observed in diabetic patients with dysautonomia [26,59]. Therefore, periodic monitoring of the respiratory function in patients with diabetes is an appropriate action, to measure the progression of systemic microangiopathy, and could have prognostic significance since the reduction in some functional indices has been shown to correlate with mortality.…”