Charis Roussos

The respiratory muscles.

THE respiratory system consists essentially of two parts: a gas-exchanging organ — the lungs—and a pump that ventilates the lungs. The pump consists of the chest wall, the respiratory muscles that ...

Aminophylline improves diaphragmatic contractility.

In an attempt to explain the clinical efficacy of aminophylline, we studied its effect on diaphragmatic function in eight normal subjects. The relation between the electrical activity of the diaphragm and the pressure generated by the diaphragm was assessed during voluntary contractions before and after aminophylline infusion. Aminophylline shifted the electrical activity/pressure curve to the left; the pressure at a given electrical activity increased an average of 15 per cent (P less than 0.001). In four subjects, pressure was also measured during stimulation of the phrenic nerve at various frequencies before and after diaphragmatic fatigue was produced by resistive breathing, with and without aminophylline infusion. Pressure increased after fatigue at all stimulation frequencies with aminophylline, as compared with the pressure after identical fatigue runs at the same stimulation frequencies without aminophylline. The mean plasma aminophylline concentration associated with these responses was 13 +/- 0.9 mg per liter. We conclude that aminophylline improves the diaphragms contractility and renders it less susceptible to fatigue.

Effect of carbon dioxide on diaphragmatic function in human beings

We studied the effects of acute changes in the partial pressure of arterial carbon dioxide on diaphragmatic contractility and performance in four normal men. To study contractility we measured the ability of the diaphragm to generate pressure at a given level of excitation by determining the relation between the electrical activity of the diaphragm and transdiaphragmatic pressure during a voluntary quasi-isometric inspiratory effort carried out at different levels of end-tidal carbon dioxide. Our results show that contractility was reduced with hypercapnia (when end-tidal carbon dioxide was 7.5 per cent or higher), although hypocapnia (end-tidal carbon dioxide, 3 per cent) had no effect on diaphragmatic contractility. We also studied the development of diaphragmatic fatigue before and during carbon dioxide breathing. Subjects were studied at the same diaphragmatic tension-time index, a value analogous to the more familiar myocardial tension-time index, while the same inspiratory flow was maintained. Electromyographic signs of fatigue appeared at a lower tension-time index during hypercapnia than during normocapnia, indicating that endurance is diminished during hypercapnia. These findings show that acute respiratory acidosis equivalent to an arterial carbon dioxide tension of about 54 mm Hg decreases the contractility and endurance time of the diaphragm in human beings.

Coagulation system and platelets are fully activated in uncomplicated sepsis.

Objective: To test the hypothesis that the coagulation system and platelets are activated in sepsis, the uncomplicated and usually earliest stage of the septic process, and to compare the findings detected in sepsis with those found in severe sepsis and septic shock. Design: Prospective study comparing patients with sepsis, severe sepsis, and septic shock, and healthy volunteers. Setting: General intensive care unit in a tertiary university hospital. Patients: Seventy‐four consecutive septic patients (45 with sepsis, 15 with severe sepsis, and 14 with septic shock). Fourteen healthy volunteers served as control subjects. Intervention: None. Measurements and Main Results: After blood sampling, molecular activation markers of coagulation (prothrombin fragments 1 and 2, fibrinopeptide A, thrombin‐antithrombin complexes, and monomers of fibrin) and of platelets (β‐thromboglobulin and platelet factor 4), several coagulation factors, global tests of coagulation (prothrombin time and activated partial thromboplastin time), and platelet count (PTL) were measured. In sepsis, prothrombin fragments 1 and 2, fibrinopeptide A, thrombin‐anti‐thrombin complexes, and monomers of fibrin were increased to 2.52 ± 0.21 nmol/L, 20.88 ± 2.52 ng/mL, 33.8 ± 2.9 μg/L, and 69% positive, respectively, compared with control subjects (0.86 ± 063 nmol/L, 1.14 ± 0.15 ng/mL, 16.07 ± 1.01 μg/L, and 0%, respectively). β‐Thromboglobulin and the β‐thromboglobulin‐to‐platelet factor 4 ratio were also increased to 107.87 ± 11.87 IU/mL and 8.86 ± 1.06, compared with controls (18.36 ± 2.99 IU/mL and 2.67 ± 0.52, respectively). With the exception of a decrease in factor XII and an increase in fibrinogen, coagulation factors, global coagulation tests, and PTL were not changed in sepsis. In severe sepsis and mainly in septic shock, coagulation factors were markedly decreased, global coagulation tests were prolonged, and PTL was reduced. All changes were independent of the causative infectious pathogen. Conclusion: Coagulation system and platelets are strongly activated in sepsis. In this stage, only factor XII is decreased. In contrast, in severe sepsis and mainly in septic shock, most of the coagulation factors are depleted, PTL is decreased, and global coagulation tests are prolonged, indicating exhaustion of hemostasis. Finally, Gram‐positive, Gram‐negative, and other microorganisms produce identical impairment of coagulation.

Electrical muscle stimulation preserves the muscle mass of critically ill patients: a randomized study

IntroductionCritically ill patients are characterized by increased loss of muscle mass, partially attributed to sepsis and multiple organ failure, as well as immobilization. Recent studies have shown that electrical muscle stimulation (EMS) may be an alternative to active exercise in chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients with myopathy. The aim of our study was to investigate the EMS effects on muscle mass preservation of critically ill patients with the use of ultrasonography (US).MethodsForty-nine critically ill patients (age: 59 ± 21 years) with an APACHE II admission score ≥13 were randomly assigned after stratification upon admission to receive daily EMS sessions of both lower extremities (EMS-group) or to the control group (control group). Muscle mass was evaluated with US, by measuring the cross sectional diameter (CSD) of the vastus intermedius and the rectus femoris of the quadriceps muscle.ResultsTwenty-six patients were finally evaluated. Right rectus femoris and right vastus intermedius CSD decreased in both groups (EMS group: from 1.42 ± 0.48 to 1.31 ± 0.45 cm, P = 0.001 control group: from 1.59 ± 0.53 to 1.37 ± 0.5 cm, P = 0.002; EMS group: from 0.91 ± 0.39 to 0.81 ± 0.38 cm, P = 0.001 control group: from 1.40 ± 0.64 to 1.11 ± 0.56 cm, P = 0.004, respectively). However, the CSD of the right rectus femoris decreased significantly less in the EMS group (-0.11 ± 0.06 cm, -8 ± 3.9%) as compared to the control group (-0.21 ± 0.10 cm, -13.9 ± 6.4%; P < 0.05) and the CSD of the right vastus intermedius decreased significantly less in the EMS group (-0.10 ± 0.05 cm, -12.5 ± 7.4%) as compared to the control group (-0.29 ± 0.28 cm, -21.5 ± 15.3%; P < 0.05).ConclusionsEMS is well tolerated and seems to preserve the muscle mass of critically ill patients. The potential use of EMS as a preventive and rehabilitation tool in ICU patients with polyneuromyopathy needs to be further investigated.Trial Registrationclinicaltrials.gov: NCT00882830

Hydrogen Sulfide Is an Endogenous Inhibitor of Phosphodiesterase Activity

Objective—Recent studies have demonstrated that hydrogen sulfide (H2S) is produced within the vessel wall from l-cysteine regulating several aspects of vascular homeostasis. H2S generated from cystathione &ggr;-lyase (CSE) contributes to vascular tone; however, the molecular mechanisms underlying the vasorelaxing effects of H2S are still under investigation. Methods and Results—Using isolated aortic rings, we observed that addition of l-cysteine led to a concentration-dependent relaxation that was prevented by the CSE inhibitors dl-propargylglyicine (PAG) and &bgr;-cyano-l-alanine (BCA). Moreover, incubation with PAG or BCA resulted in a rightward shift in sodium nitroprusside-and isoproterenol-induced relaxation. Aortic tissues exposed to PAG or BCA contained lower levels of cGMP, exposure of cells to exogenous H2S or overexpression of CSE raised cGMP concentration. RNA silencing of CSE expression reduced intracellular cGMP levels confirming a positive role for endogenous H2S on cGMP accumulation. The ability of H2S to enhance cGMP levels was greatly reduced by the nonselective phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine. Finally, addition of H2S to a cell-free system inhibited both cGMP and cAMP breakdown. Conclusion—These findings provide direct evidence that H2S acts as an endogenous inhibitor of phosphodiesterase activity and reinforce the notion that this gasotransmitter could be therapeutically exploited.

Angiopoietin-2 is increased in severe sepsis: correlation with inflammatory mediators.

Objective: Angiopoietin (Ang)‐2 is an endothelium‐specific growth factor, regulated by proinflammatory stimuli, that destabilizes vascular endothelium and increases vascular leakage; consequently, Ang‐2 may contribute to sepsis pathophysiology. We have studied 1) serum Ang‐2 levels in critically‐ill patients and investigated potential relationships with inflammatory mediators and indices of disease severity and 2) the effect of sepsis‐related inflammatory mediators on Ang‐2 production by lung endothelium in vitro. Design: Prospective clinical study followed by cell culture studies. Setting: General intensive care unit and research laboratory of a university hospital. Subjects: Human and bovine lung microvascular endothelial cells and 61 patients (32 men). Patients were grouped according to their septic stage as having: no systemic inflammatory response syndrome (n = 6), systemic inflammatory response syndrome (n = 8), sepsis (n = 16), severe sepsis (n = 18), and septic shock (n = 13). Interventions: Cells were exposed to lipopolysaccharide, tumor necrosis factor‐&agr;, and interleukin‐6. Measurements and Main Results: Patients’ serum Ang‐2 levels were significantly increased in severe sepsis as compared with patients with no systemic inflammatory response syndrome or sepsis (p < .05 by analysis of variance). Positive linear relationships were observed with: serum tumor necrosis factor‐&agr; (rs = 0.654, p < .001), serum interleukin‐6 (rs = 0.464, p < .001), Acute Physiology and Chronic Health Evaluation II score (rs = 0.387, p < .001), and Sequential Organ Failure Assessment score (rs = 0.428, p < .001). Multiple regression analysis revealed that serum Ang‐2 is mostly related to serum tumor necrosis factor‐&agr; and severe sepsis. Treatment of human lung microvascular endothelial cells with all mediators resulted in a concentration‐dependent Ang‐2 reduction. Treatment of bovine lung microvascular endothelial cells with lipopolysaccharide and tumor necrosis factor‐&agr; increased Ang‐2 release, and interleukin‐6 reduced basal Ang‐2 levels. Conclusions: First, patients’ serum Ang‐2 levels are increased during severe sepsis and associated with disease severity. The strong relationship of serum Ang‐2 with serum tumor necrosis factor‐&agr; suggests that the latter may participate in the regulation of Ang‐2 production in sepsis. Second, inflammatory mediators reduce Ang‐2 release from human lung microvascular endothelial cells, implying that this vascular bed may not be the source of increased Ang‐2 in human sepsis.

Angiopoietin‐1 inhibits endothelial permeability, neutrophil adherence and IL‐8 production

Angiopoietin‐1 (Ang1) is an angiogenic growth factor that binds to the Tie2 receptor on vascular endothelium, promoting blood vessel maturation and integrity. In the present study, we have investigated whether Ang1 also possesses anti‐inflammatory properties by determining its effects on endothelial barrier function, neutrophil (PMN) adherence to endothelial cells (EC) and production of the PMN chemotactic factor interleukin‐8 (IL‐8). Pretreatment of endothelial monolayers with Ang1 attenuated the permeability increase induced by thrombin in both lung microvascular cells and a human endothelial cell line. Similarly, Ang1 prevented the permeability‐inducing effects of platelet‐activating factor, bradykinin and histamine. Pretreatment of EC with Ang1 also reduced the adherence of PMN to EC stimulated by thrombin. In contrast to its ability to counteract the increase in monolayer permeability brought about by various inflammatory agents, Ang1 did not affect the ability of histamine, PAF, or tumor necrosis factor‐α to stimulate PMN adherence to EC. In addition to its ability to inhibit PMN adherence, Ang1 diminished IL‐8 production from EC challenged with thrombin in a concentration‐dependent manner. When EC were preincubated with the specific Rho kinase (ROCK) inhibitor Y‐27632, we observed a reduction in PMN adherence in response to thrombin, as well as a decrease in thrombin‐stimulated IL‐8 production. Coincubation of monolayers with Y‐27632 and Ang1 did not further attenuate the above‐mentioned responses. However, Ang‐1 failed to inhibit the activation of RhoA in response to thrombin, suggesting that inhibition of EC adhesiveness for PMN and IL‐8 production by Ang1 does not result from reduced ROCK activation. We conclude that Ang1 can counteract several aspects of the inflammatory response, including endothelial permeability, PMN adherence to EC as well as inhibition of IL‐8 production by EC.

Inhibition of LPS-stimulated pathways in macrophages by the flavonoid luteolin.

We have previously shown that the flavonoid luteolin inhibits the expression of pro‐inflammatory molecules induced by LPS. In the present study we tested the ability of luteolin to block signalling pathways implicated in LPS‐induced inflammatory gene expression in macrophages. Exposure of the murine macrophage cell line RAW 264.7 to LPS increased phosphorylation of the mitogen‐activated protein kinase family members ERK1/2, p38 and JNK1/2 in a time‐dependent manner. Pretreatment of RAW 264.7 with luteolin inhibited the LPS‐induced ERK1/2 and p38, but not JNK1/2, phosphorylation, and blocked the LPS‐induced TNF‐α release. To investigate which of these pathways contribute to the inhibitory effects of luteolin on TNF‐α release, cells were pretreated with pharmacological inhibitors of these pathways; PD98059 and SB203580 when used alone failed to inhibit TNF‐α release, whereas pretreatment with both agents attenuated TNF‐α release. We have previously shown that luteolin blocks Akt phosphorylation in response to LPS in RAW 264.7 macrophages. To determine the role of Akt in TNF‐α release, cells were transiently transfected with a dominant negative form of Akt (K179M). Overexpression of K179M Akt did not alter LPS‐induced TNF‐α release, suggesting that inhibition of this kinase does not mediate the inhibitory action of luteolin. In addition, DRB (a pharmacological inhibitor of CK2) blocked TNF‐α release in a concentration‐dependent manner, whereas co‐treatment of cells with luteolin and DRB did not have an additive effect. We conclude that luteolin interferes with LPS signalling by reducing the activation of several MAPK family members and that its inhibitory action on TNF‐α release correlates with inhibition of ERK, p38 and CK2 activation.

Lung involvement in primary Sjögren’s syndrome is mainly related to the small airway disease

OBJECTIVE To evaluate lung involvement in patients with primary Sjögren’s syndrome. METHODS Sixty one consecutive, non-smoking patients, 58 women and three men, were evaluated clinically, physiologically, and radiologically. A bronchial and/or transbronchial biopsy was performed on 13 of the patients. Physiological data were compared with that of a control group of 53 healthy non-smoking subjects matched for age and sex. RESULTS In 41% of the patients the main symptom was dry cough. Physiological studies revealed that the patients presented significantly lower expiratory flow values (% pred) when compared with those of the control group: the forced expiratory volume in one second (FEV1) (mean (SD)) was 96% (16) v 111% (13) (p<0.0001), the maximal expiratory flow at the 50% of the vital capacity (MEF50) was 72% (24) v103% (17) (p<0.0001), and the maximal expiratory flow at the 25% of the vital capacity (MEF25) was 49% (25)v 98 % (20) (p<0.0001). No significant difference was noted for the carbon monoxide diffusion value (% pred), between patients and controls. Blood gases were evaluated in 44 patients: mild hypoxemia was observed, and the alveolo-arterial oxygen difference (P(A-a)o 2) correlated significantly with MEF50 (r=0.35, p<0.01) and MEF25 (r=0.33, p<0.01) values. Chest radiography showed mild, interstitial-like changes in 27 patients while slightly increased markings were present in 21. High resolution computed tomography of the lungs was performed in 32 patients (four with a normal chest radiograph, six with suspected interstitial pattern, 19 with apparent interstitial pattern, and three with hyperinflation) and revealed predominantly wall thickening at the segmental bronchi. All positive findings by computed tomography derived from the patients with abnormal chest radiographs. Transbronchial and/or endobronchial biopsy specimens in 10 of the 11 sufficient tissue samples revealed peribronchial and/or peribronchiolar mononuclear inflammation, while interstitial inflammation coexisted in two patients. CONCLUSION The airway epithelia seem to be the main target of the inflammatory lesion of the lung in patients with primary Sjögren’s syndrome. It seems to be common, subclinically leading to obstructive small airway physiological abnormalities.