EFFECTS OF PULMONARY VASCULAR CONGESTION ON POSTURAL CHANGES IN THE PERFUSION AND FILLING OF THE PULMONARY VASCULAR BED

Postural variation of pulmonary diffusing capacity as a marker of lung microangiopathy in Indian patients with type 2 diabetes mellitus

INTRODUCTION

Diabetes mellitus (DM) is characterized by the presence of chronic hyperglycemia and formation of advanced glycation end products (AGEs). Interaction between AGE and its receptor leads to endothelial damage and microangiopathy. This study was undertaken to investigate the possibility of using a postural variation of diffusing capacity as an early marker of lung microangiopathy and its correlation with the level of adhesion molecules, HbA1c, duration of diabetes, and insulin resistance in type 2 DM (T2DM) patients with and without microangiopathy.

MATERIALS AND METHODS

Forty patients having T2DM without any microangiopathy (n = 20) as well as with microangiopathy (n = 20), and 22 age and sex matched healthy controls were enrolled in this cross-sectional study. Measurement of lung volumes and capacities were done. DLco was measured in sitting and supine position. Levels of vascular cell adhesion molecule-1 (VCAM-1), E-selectin, fasting glucose, and insulin were estimated in plasma of the patients and compared with controls.

RESULTS

Restrictive type of ventilatory change was observed in DM patients. Diffusing capacity (% predicted) in the supine position (P < 0.0001), postural change in DLco (P < 0.0001), and coefficient of diffusion were significantly less in DM patients as compared to controls. Plasma levels of VCAM-1 were significantly higher in DM patients without microangiopathy and negatively correlated (r = -0.4054, P = 0.0094) with Δ DLco in all diabetic subjects. All patients had significantly higher insulin resistance.

CONCLUSION

Lack of postural increase in diffusing capacity in type 2 diabetic patients along with increased VCAM-1 levels could reflect the presence of an early microangiopathy of the small pulmonary vessels.

The diabetic lung--a new target organ?

Several abnormalities of the respiratory function have been reported in patients with type 1 and type 2 diabetes. These abnormalities concern lung volume, pulmonary diffusing capacity, control of ventilation, bronchomotor tone, and neuroadrenergic bronchial innervation. Many hypotheses have emerged, and characteristic histological changes have been described in the "diabetic lung", which could explain this abnormal respiratory function. Given the specific abnormalities in diabetic patients, the lung could thus be considered as a target organ in diabetes. Although the practical implications of these functional changes are mild, the presence of an associated acute or chronic pulmonary and/or cardiac disease could determine severe respiratory derangements in diabetic patients. Another clinical consequence of the pulmonary involvement in diabetes is the accelerated decline in respiratory function. The rate of decline in respiratory function in diabetics has been found to be two-to-three times faster than in normal non-smoking subjects, as reported in longitudinal studies. This finding, together with the presence of anatomical and biological changes similar to those described in the aging lung, indicates that the "diabetic lung" could even be considered a model of accelerated aging. This review describes and analyses the current insight into the relationship of diabetes and lung disease, and suggests intensifying research into the lung as a possible target organ in diabetes.

Diabetes mellitus vs. Raynaud disease: different lung vascular bed disorders

BACKGROUND

In type II diabetes mellitus there are few data concerning pulmonary function abnormalities. In normal subjects and in patients with primary Raynaud phenomenon, cold pressor test induces a decrease in carbon monoxide single-breath diffusing capacity (DL,co) but not in secondary Raynaud phenomenon. Our objective was to assess evaluation of lung diffusion capacity postural changes in diabetes mellitus and in secondary Raynaud phenomenon, two diseases with different pulmonary capillaries functional disorders.

METHODS

Twenty-five patients with type II diabetes mellitus (mean age 52.24 years), 17 patients with secondary Raynaud phenomenon (mean age 47.06 years), non-smokers without pulmonary or heart disease, and 26 healthy matched subjects (mean age 47.50 years) underwent lung diffusion capacity measurements by single-breath method also corrected by alveolar volume (DL,co) in sitting and supine positions.

RESULTS

Patients with diabetes mellitus exhibited lower values of DL,co and DL,co/VA measurements in comparison with subjects with Raynaud phenomenon and control group (p <0.01). Additionally, they had a significant decrease in DL,co in supine compared to sitting position (83.88 +/- 16.53 vs. 89.68 +/- 18.03, p = 0.023). To the contrary, supine position in secondary Raynaud phenomenon and in control group after cold pressor test showed a significant increase in DL,co/VA (120.93 vs. 109.78 in Raynaud and 114.36 vs. 99.47 in control group, p <0.001).

CONCLUSIONS

Postural changes of lung diffusion capacity could be used as a simple, non-invasive method to detect vascular disease resulting from different pathophysiologic mechanisms such as diabetes mellitus and Raynaud phenomenon.

Postural variations of pulmonary diffusing capacity in insulin-dependent diabetes mellitus

STUDY OBJECTIVE

To assess whether posture-related changes of diffusing capacity could be considered as an early sensitive marker of pulmonary abnormalities in patients with insulin-dependent diabetes mellitus (IDDM) and whether the postural variations of pulmonary capillary blood volume (Vc) could reflect the lung capillary damage that characterizes the diabetic microangiopathy.

DESIGN

Carbon monoxide diffusing capacity (DCO) was measured by the single-breath method. Four DCO measurements, two in sitting and two in supine position, were performed in each subject using gas mixtures containing different oxygen concentrations. Membrane and capillary volume components of the diffusion capacity were calculated and both were expressed as absolute value and corrected by alveolar volume (VA).

PATIENTS

Twenty IDDM patients and 20 normal subjects matched for age and sex were studied.

MEASUREMENTS AND RESULTS

The IDDM patients showed normal pulmonary volumes and flows. No significant differences between the two groups were found for DCO, coefficient of diffusion, Vc, and pulmonary capillary blood volume corrected by alveolar volume in sitting position. All these indexes significantly increased in normal subjects but not in diabetics, by changing the posture of the subject from sitting to supine position. In a multivariate analysis, the presence of diabetes mellitus and the age of the subjects were the only significant predictors of Vc postural changes.

CONCLUSIONS

This postural test, adjusted for age, could be included in a screening diagnostic procedure for an early assessment of pulmonary abnormalities in diabetic patients. The lack of Vc postural increase in diabetics could reflect the presence of a microangiopathy involving the pulmonary small vessels.

Effects of body position and age on membrane diffusing capacity and pulmonary capillary blood volume

The effects of body position and age on the membrane diffusing capacity (Dm), pulmonary capillary blood volume (Vc), and the single breath carbon monoxide diffusing capacity (Dco) were evaluated in the erect (sitting) and supine positions in 16 normal young men (under 40 years old, younger group) and in 13 older men (over 40 years old, older group). Dm and Vc were estimated by several measurements of the Dco at increasing alveolar oxygen tension (PAO2). The results showed that Dco, Dm, Vc, and Kco (Dco corrected by alveolar volume) decreased with age in both positions. The differences in Dco, VC, and Kco between the two positions (supine minus the erect position) also decreased with age. The mechanisms of the increases in Dco in the supine position remain to be explained but may be due to a change in pulmonary capillary shape from an elliptical (erect position) to a circular configuration (supine position) since Vc increased more than Dm on assuming the supine position. The findings may be of clinical importance since many physicians have attempted to utilize a reduction in the positional change in Dco as a potential marker of disease.

Abnormal distribution of pulmonary blood flow after the Glenn shunt or Fontan procedure: risk of development of arteriovenous fistulae

Since the Fontan procedure results in low pulsatile pulmonary blood flow similar to that seen in patients with a Glenn shunt, it may also be associated with abnormal distribution of flow to the lower lung lobes and with the development of pulmonary arteriovenous fistulae (PAVF). In 12 patients 0.8 to 4.5 years after Fontan procedure and in 20 patients 0.2 to 18 years after receipt of Glenn shunts we assessed ventilation (with 133Xe) and perfusion (after a peripheral injection of 99mTc-macroaggregated albumin) to compare upper to lower lobe distribution of blood flow with that in a control group. The presence of PAVF was assessed by radionuclide activity in kidneys and the brain and by a two-dimensional echocardiographic contrast study. A decreased upper/lower lobe perfusion ratio was noted in 13 of 20 patients with Glenn shunts (65%) and correlated with the time after surgery (p less than .05). Despite the shorter follow-up period, two of 12 (16%) patients who had undergone the Fontan procedure also had a decreased upper/lower lobe perfusion ratio, and one of these developed right heart failure. Brain and kidney radionuclide counts above control values were observed in all patients with Glenn shunts and in 11 of 12 patients who had the Fontan operation. However, in only five of 20 (25%) patients with Glenn shunts were PAVF confirmed by the two-dimensional echocardiographic contrast study. Three of the five patients with PAVF had Glenn shunts of long duration.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary hypertension in mitral valve disease: 56 surgical patients reviewed

A total of 392 patients have undergone prosthetic valve surgery including the mitral valve over a four-year period (1972-76). Of these patients 56 (14%) had a pulmonary artery systolic pressure of 70 mmHg or more during preoperative cardiac catheterisation and the hospital mortality of this group was 5.4%. Similarly, the hospital mortality of the remaining 336 patients with a pulmonary artery pressure below 70 mmHg was 5.4%. The presence of pulmonary hypertension in patients with valve disease including the mitral valve does not therefore indicate that the risk of dying in hospital as a consequence of corrective surgery is increased. The absence of a raised hospital mortality in this recent series may be attributed to improved surgical techniques and materials, while the use of droperidol and pentolinium which may reduce pulmonary vascular resistance as well as systemic resistance during surgery could be contributory.

Acute effects of increase in pulmonary vascular distending pressures on pulmonary blood volume and pulmonary extravascular fluid volume in man

The acute hemodynamic effects of supine leg exercise or atrial pacing were studied in 114 patients undergoing right and either transseptal (87 cases) or retrograde (27 cases) left heart catheterization. Seventy-one patients - 15 with coronary artery disease, 22 with aortic valve disease, and 34 with mitral valve disease - performed exercise on a bicylce ergometer. Forty-three patients, of whom 22 had coronary artery disease, nine aortic valve disease and 12 mitral valve disease, were studied during rapid atrial pacing. Cardiac index (CI), pulmonary artery mean (PAm), and left atrial mean (LAm) pressure, pulmonary blood volume (PBV) and pulmonary extravascular volume (PEV) were measured during the control state and during acute intervention. Both exercise and pacing resulted in significant elevations in PAm (range 37-65%) and LAm (range 36-43%) mean pressures in all patients. Cardiac index rose between 34 and 58% in the exercise groups, but did not change in those who were paced. During intervention both PBV and PEV increased significantly in all but the nine patients with aortic valve disease who were paced. Although volume increased occurred, they did not achieve the 5% significanc- level. For all patients the mean increment in PBV ranged between 37 and 123 ml/m2 over control, while PEV rose between 15 and 35 ml/m2. In each group the increases in PEV and PBV were proporationate, so that the ratio of PEV/PBV DID NOT CHANGE SIGNIFICANTLY BETWEEN THE CONTROL AND INTERVENTION STATES. Thus PEV and PBV increases occurred with elevations in pulmonary vascular pressures whether or not blood flow increased. Our data in patients with normal pulmonary vascular beds (i.e., coronary artery disease and aortic valve disease) strongly support the hypothesis that recruitment of vascular channels accounts for the acute changes in PEV and PBV and that the changes in PEV over a brief period of time do not necessarily reflect a "true" increase in extravascular lung water. Although pressures are higher in the lungs of patients with mitral valve disease, the data also suggest that recruitment is likely to be the mechanism for the observed proportionate increase in pulmonary extravascular volume and pulmonary blood volume.

Pulmonary diffusing capacity in disorders of the pulmonary circulation

The pulmonary diffusing capacity for carbon monoxide was measured by single breath (DcoSB) and steady state (DcoSS) techniques in 48 patients with various pulmonary circulatory disorders and the results compared with the type of hemodynamic abnormality. Patients with pure inflow obstruction (primary pulmonary hypertension, recurrent pulmonary emboli) had the lowest Dco (mean DcoSB = 14.3 ml/min/mm Hg [59%], mean DcoSS = 9.0 ml/min/mm Hg [58%]). Patients with inflow and outflow obstruction, (valvular heart disease with increased pulmonary vascular resistance [PVR]), had higher values (mean DcoSB = 16.2 [68%], mean DcoSS = 10.2 [65%]). In patients with pure outflow obstruction (valvular heart disease and normal PVR) Dco was normal (means 23.2 [96%] and 14.4 [87%] respectively). Patients with increased pulmonary blood flow (PBF), (left to right shunts), had the highest Dco (means 31.3 [118%] and 16.4 [106%]). There was a reciprocal relationship between Dco and PVR, a low Dco being characteristic of pulmonary inflow obstruction. Patients with increased PBF had lower Dco values than exercising normal subjects with comparable PBF. In patients with pulmonary circulatory abnormalities and no obstructive or restrictive lung disease, Dco is low when inflow obstruction predominates. Dco inceases with the addition of outflow obstruction and is above normal when there is an increased PBF and low PVR.

Indicator dilution measurements of extravascular water in the lungs

Multiple indicator dilution studies of the pulmonary circulation were carried out in conscious, resting and exercising, and anesthetized dogs under conditions where there was no pulmonary edema. Labeled red cells, water, and albumin were injected together into the pulmonary artery, and effluent dilution patterns were obtained from the descending thoracic aorta. The product of the mean transit time differences between labeled water and red cells, and the pulmonary water flow was used to estimate extravascular parenchymatous water; and this was expressed as a proportion of the water content of the blood-drained lung at postmortem examination. These estimates of the proportional water content were found to increase with flow, and to approach an asymptotic value. Reconsideration of the flow patterns in capillaries, however, led to the postulate that extravascular water should be calculated, utilizing as the appropriate vascular reference a substance that uniformly labels the water in red cells and plasma, and which is confined to the circulation, rather than a tracer that only labels red cells. The mean transit time of this substance is approximated by the sum of the mean transit times of labeled red cells and albumin, each weighted according to the proportion of the water content of blood present in that phase. The values for lung water content so computed also increased with flow, and appeared to approach an asymptote that corresponded to approximately two-thirds of the wet lung weight. The estimated values for the water space after pentobarbital anesthesia corresponded to the lower values obtained in the resting conscious animals. When the anesthetized animals were also bled, the estimated water space was disproportionately large, in relation to the previous values. These experimental results support the hypothesis that dilutional estimates of the lung water space reflect pulmonary capillary filling; that this filling increases with exercise; and that a relative increase in filling also occurs as part of the response to hemorrhage.

Physiologic studies of the pulmonary capillary bed after barium sulfate embolization

22 anesthetized dogs were given a barium sulfate suspension intravenously in a dose sufficient to double mean pulmonary artery pressure. 10 sec breath-holding carbon monoxide diffusing capacity (D(LCO10)) was measured before and after this standard embolization in each dog. No post-embolic decrease in D(LCO10) was observed. In the study of this apparent paradox, it was found that the potential for further increase in D(LCO10) during exercise remained after embolization. During rest prolongation of breath holding to 60 sec decreased CO absorption significantly more in the embolized than in the nonembolized dogs. While D(LCO10) was not affected by standard barium embolization, oxygen diffusing capacity was clearly decreased. The bronchial collateral circulation did not participate in preventing a D(LCO10) decrease after embolization since surgical interruption of the bronchial circulation did not alter the response to barium. Microscopic examination of lung sections taken after standard embolization showed plugging of precapillary vessels in the 40-50 mu range. These studies suggest that acute precapillary embolic obstruction of vessels of this size interferes remarkably little with CO absorption over short periods of time, probably because of continued CO absorption in portions of the capillary net distal to the sites of impaction. The remarkable anastomotic nature of this capillary network with multiple sources of access possibly provides the anatomic basis for this observation. This study demonstrates a clear dissociation between acute changes in pulmonary vascular resistance and D(LCO10)-both during rest and exercise.

The pulmonary capillary bed in various forms of pulmonary hypertension

Pulmonary diffusing capacity for CO (D L ), membrane diffusing capacity (D M ), and pulmonary capillary blood volume (V c ) were measured in 44 patients with various forms and severity of pulmonary vascular disease, and these measurements were compared with hemodynamic data obtained at cardiac catheterization, with clinical disability, and, in 27 patients, with the results of corrective cardiac surgery. In 11 of these patients, D L , D M , and V c were remeasured up to 8 months after cardiac surgery.

In general, the diffusing characteristics and pressure-volume relationships in this larger group confirmed the previously reported findings in mitral valve disease. 1 D M was impaired in almost all cases regardless of etiology or severity. Most of the 11 patients restudied showed no change in D L , D M , or V c up to 8 months after surgery. Reduction in V c correlated well both with clinical disability and with surgical results.

Two patients with primary pulmonary hypertension and three of the four patients with equally severe pulmonary hypertension due to mitral valve disease had high V c relative to pulmonary vascular resistance. If the measurements of V c are not falsely high, then it appears that the capillary bed makes relatively and absolutely less contribution to the total rise in pulmonary vascular resistance in these patients. This could be explained by intense precapillary vasoconstriction in the presence of a relatively normal pulmonary capillary bed.

Physiological alterations in the pulmonary capillary bed at rest and during exercise. The effect of body position and trimethaphan camphorsulfonate

The reactivity of the pulmonary capillary bed during exercise as estimated by change in the pulmonary diffusing capacity (D l co ) has been shown to be dependent upon at least two separate mechanisms. The initial (0 to 10 second) D l co rise with exercise appears to be volume-pressure dependent and may be altered by mechanisms influencing these factors in the lungs. The later elevation of D l co with exercise was demonstrated to be primarily independent of the initial rise and uninfluenced by factors affecting peripheral venous return, that is body position and ganglionic blockade.