Respiratory and Cardiovascular Function in Patients with Severe Pulmonary Hypertension

Abstract

applied the term hypertensive pulmonary vascular disease to patients with chronic, severe pulmonary hypertension. They emphasized that this disease is a distinct clinicopathologic entity with uniform clinical features and characteristic morphologic changes of the pulmonary arteries and arterioles irrespective of the etiology of the hypertension. The vascular changes indicate restriction of the pulmonary vascular bed, which may alter pulmonary gas exchange. This study of the respiratory physiology of such patients was undertaken to determine if the uniform clinical picture could in part result from some common, specific pathophysiologic mechanism.Methods Patients Data were obtained in 12 patients with chronic, severe pulmonary hypertension of varied etiology. In four patients interatrial or interventriicular septal defects were established by cardiac catheterization. No intracardiac defects were demonstrated in the other eight patients. The diagnosis of primary pulmonary hypertension in one patient was based upon postmortem observations of pulmonary vascular changes and massive right ventricular hypertrophy. Diffuse pulmonary schistosomiasis was confirmed by biopsy of the lung in another patient. No definite pathologic confirmation is yet available in six patients. In nine patients hemodynamics, ventilation, lung volumes, ventilation-blood flow relationship's, and steadystate carbon monoxide diffusing capacity at rest and at exercise were studied on one or more oc-casions. It was not p,ossible to complete all measurements in three patients. ProcedureRight heart catheterization was performed in the usual manner from an antecubital vein and left atrial puncture by the percutaneous transthoracic approach. Intracardiac shunts were detected by differential blood samples and dye-dilution curves. Cardiac output and shunit flows were calculated by the Fick principle.Ventilation capacity and lung volumes were determined by conventional methods. Metabolism during rest and exercise, diffusion capacity, and arterial bloiod composition were measured with the patient standing still and, whenever possible, while walking on a treadmill. Arterial blood siamples were analyzed for pH and for sitandard bicarbonate by the Astrup macro method, and the PC02 was determined from his line charts.2 Oxygen saturation was calculated from duplicate Van Slyke analyses of oxygen content and capacity with appropriate correction for dissolved gas. The piartial pressure of oxygen was read from a standard oxyhemoglobin dissociation curve.3 Diffusing capacity measurements were performed by a steady-state continuous-breathing method4 with modification of the breathing circuilt to provide for automatic end-tidal gas sampling.5 Expired air was analyzed for oxygen with a paramagnetic analyzer, for carbon dioxide in a Scholander microlgas analyzer, and for carbon moinoxide with an infrared carbon monoxide meter.All calculations of diffusing capacity were corrected for carbon monoxide back pressure, which was assumed equal to the arterial pressure.6 Result...

Chronic Thromboembolic Pulmonary Hypertension: Effects of Pulmonary Endarterectomy

“…The combination of alveolar hyperventilation and increased (parallel) dead space ventilation is remarkable as it puts an extra ventilatory drive on an already increased effort of breathing. These findings are in unison with reports in patients with iPAH (Meyer et al, 2005;Wessel et al, 1964;Zoia et al, 2002). The alveolar hyperventilation seemed to be only in part hypoxic driven, as administration of 100% oxygen for at least 20 minutes increased but did not normalize Pa,CO 2 (4.50 ± 0.42 kPa vs. 4.58 ± 0.42 kPa).…”

“…In the past, abnormalities in coagulation and fibrinolysis pathways have been identified in CTEPH patients, however, the frequency of these defects in such patients were similar to those in the general population. Lupus anticoagulant and antiphospholipid antibodies were shown to be present in 10-20% of patients with CTEPH, which is higher than in patients with acute venous thromboembolism (Auger et al, 1995;Wolf et al, 2000). Bonderman et al showed increased levels of factor VIII (FVIII) in about 40% of CTEPH patients as compared to both healthy controls and patients with non-thromboembolic pulmonary hypertension (Bonderman et al, 2003).…”

The CO Single Breath Transfer Factor of the Lung

“…The picture is further complicated, especially in mitral valve disease, by the oc currence of obliterative lesions involving in itially the small peripheral branches of the pulmonary arterial tree. This is accompa nied by thrombosis, thromboembolism and functional vascoconstriction [Parker and Weiss, 1936;Wessel et al, 1964;Forster, 1957;Hamer, 1965;Aber and Campbell, 1965;Yu, 1969], giving rise to an inflow obstruction of the alveolar capillary system. This results in a decrease of Vcv.…”

Primary (Idiopathic) Pulmonary Hypertension

“…T h erefo re, th e m e c h a n ic al fu n c tio n o f lu n g s a n d th o ra x is re la tiv e ly u n d is tu rb e d a n d sig n ifican t changes in th is re g a rd do n o t o ccu r u n til th e o n set o f h e a r t failu re. A slight in crease o f resid u al v o lu m e a n d R V /T L C ra tio in o u r a n d a few o th e r p a tie n ts [23,26] is m ore likely re la te d to c o m p lic a tin g o b stru c tiv e a irw a y disease and th is is n o t a com m on finding [19,24], T h e re m a rk a b le e x te rn a l h y p e rv e n tila tio n e x h ib ite d b y o u r p a tie n t has been n o te d b y o th e rs [24,26]. I t re su lts in in creased w ork of b re a th in g w hich larg ely a c c o u n ts fo r th e co m p lain t of d y sp n e a .…”

“…T h e diffusing c a p a c ity is u su a lly n o rm al or slig h tly red u ced [22,23,31] a n d th is w as so in o u r case. A ny re d u c tio n m u st b e th e resu lt o f a d ecrease in th e effective area of th e m e m b ra n e r a th e r th a n an in crease in its thickness.…”