Ben Fox

Peripheral endothelial dysfunction in patients with pulmonary arterial hypertension

BACKGROUND Pulmonary endothelium plays an important role in the mechanism of pulmonary arterial hypertension (PAH). However, there is only a few data regarding the systemic endothelium in this syndrome. This study focused on the systemic endothelial involvement in PAH. METHODS Endothelial function was evaluated in 54 patients with idiopathic (n=28), scleroderma-associated (n=10), chronic thromboembolic (n=7), or Eisenmenger (n=9) PAH and 21 controls (13 healthy; eight scleroderma and normal pulmonary pressure). All underwent clinical evaluation, pulmonary assessment, echocardiography, and pulmonary cardiac stress test. Endothelial function was evaluated by measuring the forearm blood flow dilatation response to brachial arterial occlusion by a non-invasive plethysmograph, yielding a peripheral arterial tone (PAT) ratio. RESULTS The PAT ratio was significantly lower (p<0.05) than healthy controls in all patients except the Eisenmenger group (control: 2.20+/-0.25; idiopathic 1.84+/-0.51; scleroderma 1.66+/-0.66; thromboembolic 1.89+/-0.32; Eisenmenger 2.17+/-0.62). The impaired hyperemic response significantly correlated with disease severity, as measured by NYHA classification (r=-0.210, p=0.035), pulmonary pressure (r=-0.228, p=0.035), 6 min walking distance (r=0.215, p=0.047), and oxygen desaturation on effort (r=0.207, p=0.038). Mean systolic pulmonary pressure among patients was 54-99 mmHg. CONCLUSION A systemic component of endothelial dysfunction might be involved in idiopathic, scleroderma-associated and chronic thromboembolic PAH that is correlated with disease severity.

Prediction of extubation outcome: a randomised, controlled trial with automatic tube compensation vs. pressure support ventilation

IntroductionTolerance of a spontaneous breathing trial is an evidence-based strategy to predict successful weaning from mechanical ventilation. Some patients may not tolerate the trial because of the respiratory load imposed by the endotracheal tube, so varying levels of respiratory support are widely used during the trial. Automatic tube compensation (ATC), specifically developed to overcome the imposed work of breathing because of artificial airways, appears ideally suited for the weaning process. We further evaluated the use of ATC in this setting.MethodsIn a prospective study, patients who had received mechanical ventilation for more than 24 hours and met defined criteria for a weaning trial, underwent a one-hour spontaneous breathing trial with either ATC (n = 87) or pressure support ventilation (PSV; n = 93). Those tolerating the trial were immediately extubated. The primary outcome measure was the ability to maintain spontaneous, unassisted breathing for more than 48 hours after extubation. In addition, we measured the frequency/tidal volume ratio (f/VT) both with (ATC-assisted) and without ATC (unassisted-f/VT) at the start of the breathing trial as a pretrial predictor of extubation outcome.ResultsThere were no significant differences in any of the baseline characteristics between the two groups apart from a significantly higher Acute Physiology and Chronic Health Evaluation (APACHE) II score in the ATC group (p = 0.009). In the PSV group, 13 of 93 (14%) patients failed the breathing trial compared with only 6 of 87 (6%) in the ATC group; this observed 8% difference, however, did not reach statistical significance (p = 0.12). The rate of reintubation was not different between the groups (total group = 17.3%; ATC = 18.4% vs. PSV = 12.9%, p = 0.43). The percentage of patients who remained extubated for more than 48 hours was similar in both groups (ATC = 74.7% vs. PSV = 73.1%; p = 0.81). This represented a positive predictive value for PSV of 0.85 and ATC of 0.80 (p = 0.87). Finally, the ATC-assisted f/VT was found to have a significant contribution in predicting successful liberation and extubation compared with the non-significant contribution of the unassisted f/VT (unassisted f/VT, p = 0.19; ATC-assisted f/VT, p = 0.005).ConclusionsThis study confirms the usefulness of ATC during the weaning process, being at least as effective as PSV in predicting successful extubation outcome and significantly improving the predictive value of the f/VT.Trial registrationCurrent Controlled Trials ISRCTN16080446

Diagnostic value of complement components in pleural fluid: Report of 135 cases

We prospectively assessed the diagnostic value of pleural fluid complement levels (total, C3, C4) in 135 patients with pleural effusion of five main etiologies, using novel markers. Complement levels correlated with pleural levels of protein, amylase, and transuded fluids. On univariate analysis, CHF-related pleural effusions were associated with significantly lower C4 levels than postsurgery or parapneumonic effusions. On multivariate analysis, pleural fluid C4 level was a significant predictor of CHF. Although the specificity, positive predictive value, and accuracy of the parameters were low in all diagnostic groups, their negative predictive value as well as the AUC ROC was high for CHF and post-LTX. We conclude that pleural fluid C4 levels can differentiate CHF-related pleural effusion from other etiologies and that normal level of C3 or C4 rule out CHF or LTX as causes of pleural effusion. Complement should be included in the assessment of pleural effusion when traditional diagnostic methods fail.

Once bitten, twice shy

A 46-year-old man of Ethiopian origin was admitted to hospital in 2008 for investigation of cough, increasing dyspnoea and weight loss over several weeks. He was known to be HIV positive. He had a history of several opportunistic infections, including Cryptosporidium diarrhoea, tuberculosis, Mycobacterium avium complex and Pseudomonas pneumonia. He had also been treated in 2005 for visceral leishmaniasis with liposomal amphotericin. His prescribed medication included trimethoprim–suxamethoxazole, clarithromycin, efarinez, lamivudine, zidovudine and folic acid. His compliance with highly active antiretroviral therapy (HAART) was known to be poor. On physical examination he was afebrile. Aside from moderate tachypnoea (24 respirations/min), his vital signs were normal. General examination showed cachexia and marked parotid swelling. The abdomen was non-tender with hepatosplenomegaly. Cardiac/respiratory examination was …