Pulmonary vasodilatation and augmentation of right ventricular function following terbutaline infusion in severe chronic pulmonary disease

In vitro hypoxia impairs beta2-adrenergic receptor signaling in primary rat alveolar epithelial cells

Hypoxia inhibits beta(2)-adrenergic receptor (beta(2)-AR) signaling in a variety of tissues, but effects in alveolar epithelium are unclear. We therefore examined the effect of 24 h of hypoxia on beta(2)-AR function in primary rat alveolar epithelial [alveolar type II (ATII)] cells. ATII cells were isolated, cultured to confluence, and incubated in normoxia or hypoxia (3% O(2)) for 24 h. Hypoxia decreased maximal terbutaline-stimulated cAMP production by 37%; potency of terbutaline was not affected. Reoxygenation (3 h) reversed this effect. Density of beta(2)-AR assessed by (-)-[(125)I]iodocyanopindolol binding was decreased in hypoxia (-22%). Hypoxia did not affect terbutaline binding affinity to beta(2)-AR. Hypoxia decreased G(s) protein levels by 27%, whereas no change was observed in G(i1/2), G(i3), and Gbeta subunits. Forskolin-stimulated cAMP production was not inhibited by hypoxia. Pertussis toxin (PTX; 0.5 microg/ml, 2 h), an inhibitor of G(i/o) proteins, restored terbutaline-stimulated cAMP production of hypoxic ATII cells to normoxic control values. Cholera toxin (CTX)-stimulated G(s) protein activity did not change in hypoxia. Hypoxia increased the sensitivity of beta(2)-AR to desensitization. These results indicate that despite the decrease in G(s) protein level G(s) protein was still functional and that hypoxia impairs beta(2)-AR signaling due to an increased activity of G(i/o) proteins.

Doppler echocardiographic assessment of the effects of inhaled long-acting β2-agonists on pulmonary artery pressure in COPD patients

Increase in pulmonary artery pressure (PAP), which is common in severe chronic obstructive pulmonary disease (COPD), is a predictor of mortality independent of airflow limitation. beta-agonists might slightly attenuate this increase because they exert a vasodilating effect on pulmonary circulation when systematically administered. We have investigated the acute effects of salmeterol and formoterol on echocardiographic systolic pulmonary artery pressure (sPAP) in 20 patients with COPD and a sPAP greater than 20mmHg at rest. Acute haemodynamic responses to inhaled formoterol or salmeterol were assessed in all patients, in a randomized, double-blind double-dummy fashion. On two consecutive days, patients received, in a randomized order, formoterol 12microg via Turbuhaler plus placebo via Diskus or salmeterol 50microg via Diskus plus placebo via Turbuhaler. Transthoracic Doppler echocardiography measurements of sPAP were made before and 15, 30, 60 and 180min after bronchodilator inhalation. Lung function, pulse oximetry and heart rate were also monitored at the same times. Mean sPAP significantly (p<0.05) decreased in comparison with baseline at 15, 30, and 60min post inhalation but returned towards control levels at 180min after both salmeterol and formoterol. There was no correlation between the maximum increase in FEV(1) and maximum decrease in sPAP either after inhalation of salmeterol (r(2)=0.071) or after that of formoterol (r(2)=0.0006). The increases in FEV(1) in comparison with baseline were always significant (p<0.05) from 15 to 180min post inhalation after either salmeterol or formoterol. Neither pulse oximetry nor heart rate changed in a significant manner (p>0.05). This study demonstrated that salmeterol and formoterol were equally beneficial for pulmonary haemodynamics in patients with COPD. A direct vasodilatation due to the activation of beta-adrenoceptors that are present in pulmonary vessels is a likely mechanism of their action in inducing the decrease in sPAP.

Life-threatening complications of systemic sclerosis

Pulmonary arterial hypertension is common in patients with SSc. Fig. 1 shows the diagnostic and therapeutic approach to PAH in SSc. Doppler echocardiography may suggest the diagnosis, but RHC is necessary to confirm PAH and to measure vasoreactivity. Therapy is directed at the underlying connective tissue disease. Vasoreactive patients often benefit from therapy with high-dose calcium-channel [figure: see text] blockers, but most patients are not vasoreactive. Intravenous epoprostenol and oral endothelin-1 receptor antagonists improve hemodynamic measurements and symptoms in SSc-associated PAH. The therapy of right ventricular failure is focused on vasodilators, inotropes, and diuretics with careful attention to avoiding systemic hypotension. The scleroderma pulmonary-renal syndrome and the scleroderma renal crisis are distinct syndromes with different clinical presentations, histopathologic manifestations, treatments, and outcomes. The scleroderma pulmonary renal syndrome is an autoimmune vasculitis of kidney and lung associated with normal blood pressure. Treatment is supportive, and prognosis is dismal. In contrast, scleroderma renal crisis is associated with systemic hypertension, onion skinning of afferent arterioles, and response to ACE inhibition and renal replacement therapy. Pericardial effusions are common but only occasionally lead to tamponade. Esophageal dysmotility is often associated with aspiration, leading to pulmonary fibrosis, pneumonia, or ARDS. Diffuse bowel involvement may result in pseudo-obstruction, bacterial overgrowth, or malabsorption. Prokinetic agents, antibiotics, and parenteral nutrition may be required.

Changes in transfer factor of the lung in response to bronchodilatation

Measurement of the transfer factor for carbon monoxide (TLCO) is a widely used clinical lung function test. Although it is frequently applied in patients with bronchial obstruction, there is little information on the effects of bronchodilatation on the test. We therefore measured TLCO in 40 patients before and after inhalation of terbutaline. TLCO was measured with the single-breath technique in 20 patients and with the intra-breath technique in 20 patients. TLCO was also measured in 20 healthy subjects with the single-breath technique. Forced expiratory volume (FEV1) increased from 2.9 +/- 1. 1 to 3.2 +/- 1.2 l in patients with bronchial obstruction in response to terbutaline inhalation. TLCO increased from 8.2 +/- 2.6 to 8.6 +/- 2.7 mmol min-1 kPa-1 (P< 0.001) and alveolar volume (VA) from 5.74 +/- 1.21 to 5.90 +/- 1.21 l (P<0.001). There was no difference between the single-breath and the intra-breath techniques. There was little change in FEV1 in the healthy subjects in response to terbutaline. TLCO increased from 10.2 +/- 2.1 to 10.5 +/- 2.2 mmol min-1 kPa-1 (P< 0.01), but there was no change in VA. The increase in TLCO in patients may partly be explained by improved distribution of the inhaled gas. In healthy subjects, terbutaline may increase pulmonary capillary volume. We conclude that bronchodilatation results in a small increase in TLCO in patients with light to moderate bronchoconstriction as well as in healthy subjects. The effect is small and should in most cases be simple to account for in the interpretation of pulmonary function tests, provided the patient's treatment is known.