Conditions associated with severe carbon monoxide diffusion coefficient reduction.

OBJECTIVE: To identify conditions associated with severe carbon monoxide transfer coefficient reduction (Kco < 40% of predicted values). PATIENTS AND METHODS: We retrospectively reviewed pulmonary function tests, such as Kco measurement, in consecutive patients evaluated in the physiology unit of a University hospital over a 6-year period. Patients were included if they had at least 1 measure of severe Kco reduction, with further detailed pulmonary function tests, clinical data, and diagnostic procedures conducted within 6 months. RESULTS: 5576 patients underwent 9061 Kco measurements. 195 patients (3.5%) with Kco < 40% were investigated (156 males; mean age 62 ± 12 years). Mean Kco was 29 ± 9% of predicted values. The main conditions associated with severe Kco reduction were: emphysema (46%); interstitial lung disease (28%); combined pulmonary fibrosis and emphysema (16%); and pre-capillary pulmonary hypertension (8%). Systolic pulmonary artery pressure was ≥ 35 mmHg at echocardiography in 88% of patients. Right heart catheterization performed in 97 patients showed pre-capillary pulmonary hypertension in 86 of 195 patients (44%). Pulmonary hypertension was the most frequent condition associated with Kco severe reduction. Pulmonary hypertension was present in 29%, 53%, and 48% of patients with chronic obstructive pulmonary disease, interstitial lung disease, and combined pulmonary fibrosis and emphysema, respectively, and was disproportionate to the parenchymal lung disease (mean pulmonary artery pressure > 35 mmHg) in 63% of cases. CONCLUSION: Severe Kco reduction is frequently related to pulmonary hypertension, especially when associated with emphysema and/or interstitial lung disease. Systematic echocardiography is thus warranted in any patient with severe Kco diminution.

Right-to-left shunt with hypoxemia in pulmonary hypertension.

BACKGROUND: Hypoxemia is common in pulmonary hypertension (PH) and may be partly related to ventilation/perfusion mismatch, low diffusion capacity, low cardiac output, and/or right-to-left (RL) shunting. METHODS: To determine whether true RL shunting causing hypoxemia is caused by intracardiac shunting, as classically considered, a retrospective single center study was conducted in consecutive patients with precapillary PH, with hypoxemia at rest (PaO2 < 10 kPa), shunt fraction (Qs/Qt) greater than 5%, elevated alveolar-arterial difference of PO2 (AaPO2), and with transthoracic contrast echocardiography performed within 3 months. RESULTS: Among 263 patients with precapillary PH, 34 patients were included: pulmonary arterial hypertension, 21%; PH associated with lung disease, 47% (chronic obstructive pulmonary disease, 23%; interstitial lung disease, 9%; other, 15%); chronic thromboembolic PH, 26%; miscellaneous causes, 6%. Mean pulmonary artery pressure, cardiac index, and pulmonary vascular resistance were 45.8 +/- 10.8 mmHg, 2.2 +/- 0.6 L/min/m2, and 469 +/- 275 dyn.s.cm-5, respectively. PaO2 in room air was 6.8 +/- 1.3 kPa. Qs/Qt was 10.2 +/- 4.2%. AaPO2 under 100% oxygen was 32.5 +/- 12.4 kPa. Positive contrast was present at transthoracic contrast echocardiography in 6/34 (18%) of patients, including only 4/34 (12%) with intracardiac RL shunting. Qs/Qt did not correlate with hemodynamic parameters. Patients' characteristics did not differ according to the result of contrast echocardiography. CONCLUSION: When present in patients with precapillary PH, RL shunting is usually not related to reopening of patent foramen ovale, whatever the etiology of PH.

Pulmonary arteriovenous malformations in patients with hereditary hemorrhagic telangiectasia.

Pulmonary arteriovenous malformations (PAVMs) associated with hereditary hemorrhagic telangiectasia may cause severe cerebral complications that may be prevented by embolization therapy. We retrospectively compared the diagnostic value of noninvasive tests for the screening of treatable (amenable to embolization) PAVMs in a series of 105 patients, using chest computerized tomography (CT) and/or pulmonary angiography as a "gold standard." Patients had assessment of dyspnea, chest radiograph, alveolar-arterial PO2 gradient under 100% oxygen (AaPO2), contrast echocardiography, and radionuclide perfusion lung scanning. Contrast echocardiography in the supine position was the most sensitive test (93%). The sensitivity of self-reported dyspnea (59%), chest radiograph alone (70%), measurement of AaPO2 by the 100% oxygen method (62%), or radionuclide lung scanning (71%), was not suitable for efficient screening. A 100% sensitivity and negative predictive value could be obtained when combining anteroposterior chest radiograph and contrast echocardiography. Our data support a screening algorithm based on the combined use of contrast echocardiography and anteroposterior chest radiograph, followed by chest CT if either test is positive. An alternative is to screen directly by chest CT. However, this algorithm may obviate the need for chest CT in patients without PAVM, who represent a majority of patients with hereditary hemorrhagic telangiectasia.