Publications by authors named "Felix Machleidt"

7 Publications

  • Page 1 of 1

Evaluation of PEEP and prone positioning in early COVID-19 ARDS.

EClinicalMedicine 2020 Nov 11;28:100579. Epub 2020 Oct 11.

Department of Infectious Diseases and Respiratory Medicine, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany.

Background: In face of the Coronavirus Disease (COVID)-19 pandemic, best practice for mechanical ventilation in COVID-19 associated Acute Respiratory Distress Syndrome (ARDS) is intensely debated. Specifically, the rationale for high positive end-expiratory pressure (PEEP) and prone positioning in early COVID-19 ARDS has been questioned.

Methods: The first 23 consecutive patients with COVID-19 associated respiratory failure transferred to a single ICU were assessed. Eight were excluded: five were not invasively ventilated and three received veno-venous ECMO support. The remaining 15 were assessed over the first 15 days of mechanical ventilation. Best PEEP was defined by maximal oxygenation and was determined by structured decremental PEEP trials comprising the monitoring of oxygenation, airway pressures and trans-pulmonary pressures. In nine patients the impact of prone positioning on oxygenation was investigated. Additionally, the effects of high PEEP and prone positioning on pulmonary opacities in serial chest x-rays were determined by applying a semiquantitative scoring-system. This investigation is part of the prospective observational PA-COVID-19 study.

Findings: Patients responded to initiation of invasive high PEEP ventilation with markedly improved oxygenation, which was accompanied by reduced pulmonary opacities within 6 h of mechanical ventilation. Decremental PEEP trials confirmed the need for high PEEP (17.9 (SD ± 3.9) mbar) for optimal oxygenation, while driving pressures remained low. Prone positioning substantially increased oxygenation (<0.01).

Interpretation: In early COVID-19 ARDS, substantial PEEP values were required for optimizing oxygenation. Pulmonary opacities resolved during mechanical ventilation with high PEEP suggesting recruitment of lung volume.

Funding: German Research Foundation, German Federal Ministry of Education and Research.
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November 2020

Severe COVID-19 Is Marked by a Dysregulated Myeloid Cell Compartment.

Cell 2020 09 5;182(6):1419-1440.e23. Epub 2020 Aug 5.

Department of Infectious Diseases and Respiratory Medicine, Charité, Universitätsmedizin Berlin, Berlin, Germany; German Center for Lung Research (DZL).

Coronavirus disease 2019 (COVID-19) is a mild to moderate respiratory tract infection, however, a subset of patients progress to severe disease and respiratory failure. The mechanism of protective immunity in mild forms and the pathogenesis of severe COVID-19 associated with increased neutrophil counts and dysregulated immune responses remain unclear. In a dual-center, two-cohort study, we combined single-cell RNA-sequencing and single-cell proteomics of whole-blood and peripheral-blood mononuclear cells to determine changes in immune cell composition and activation in mild versus severe COVID-19 (242 samples from 109 individuals) over time. HLA-DRCD11c inflammatory monocytes with an interferon-stimulated gene signature were elevated in mild COVID-19. Severe COVID-19 was marked by occurrence of neutrophil precursors, as evidence of emergency myelopoiesis, dysfunctional mature neutrophils, and HLA-DR monocytes. Our study provides detailed insights into the systemic immune response to SARS-CoV-2 infection and reveals profound alterations in the myeloid cell compartment associated with severe COVID-19.
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September 2020

COVID-19 severity correlates with airway epithelium-immune cell interactions identified by single-cell analysis.

Nat Biotechnol 2020 08 26;38(8):970-979. Epub 2020 Jun 26.

Center for Digital Health, Berlin Institute of Health (BIH) and Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.

To investigate the immune response and mechanisms associated with severe coronavirus disease 2019 (COVID-19), we performed single-cell RNA sequencing on nasopharyngeal and bronchial samples from 19 clinically well-characterized patients with moderate or critical disease and from five healthy controls. We identified airway epithelial cell types and states vulnerable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In patients with COVID-19, epithelial cells showed an average three-fold increase in expression of the SARS-CoV-2 entry receptor ACE2, which correlated with interferon signals by immune cells. Compared to moderate cases, critical cases exhibited stronger interactions between epithelial and immune cells, as indicated by ligand-receptor expression profiles, and activated immune cells, including inflammatory macrophages expressing CCL2, CCL3, CCL20, CXCL1, CXCL3, CXCL10, IL8, IL1B and TNF. The transcriptional differences in critical cases compared to moderate cases likely contribute to clinical observations of heightened inflammatory tissue damage, lung injury and respiratory failure. Our data suggest that pharmacologic inhibition of the CCR1 and/or CCR5 pathways might suppress immune hyperactivation in critical COVID-19.
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August 2020

GHRH-mediated GH release is associated with sympathoactivation and baroreflex resetting: a microneurographic study in healthy humans.

Am J Physiol Regul Integr Comp Physiol 2019 07 1;317(1):R15-R24. Epub 2019 May 1.

Department of Internal Medicine II, University Hospital Schleswig-Holstein, Luebeck, Germany.

Previous research suggested substantial interactions of growth hormone (GH) and sympathetic nervous activity. This cross talk can be presumed both during physiological (e.g., slow-wave sleep) and pathological conditions of GH release. However, microneurographic studies of muscle sympathetic nerve activity (MSNA) and assessment of baroreflex function during acute GH-releasing hormone (GHRH)-mediated GH release were not conducted so far. In a balanced, double-blind crossover design, GHRH or placebo (normal saline) were intravenously administered to 11 healthy male volunteers. MSNA was assessed microneurographically and correlated with blood pressure (BP) and heart rate (HR) at rest before (pre-) and 30-45 (post-I) and 105-120 min (post-II) after respective injections. Additionally, baroreflex function was assessed via graded infusion of vasoactive drugs. GHRH increased GH serum levels as intended. Resting MSNA showed significant net increases of both burst rate and total activity from pre- to post-I and post-II following GHRH injections compared with placebo (ANOVA for treatment and time, burst rate: = 0.028; total activity: = 0.045), whereas BP and HR were not altered. ANCOVA revealed that the dependent variable MSNA was not affected by the independent variables mean arterial BP (MAP) or HR (MAP: = 0.006; HR: = 0.003). Baroreflex sensitivity at baroreflex challenge was not altered. GHRH-mediated GH release is associated with a significant sympathoactivation at central nervous sites superordinate to the simple baroreflex feedback loop because GH induced a baroreflex resetting without altering baroreflex sensitivity.
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July 2019

Intranasal insulin suppresses systemic but not subcutaneous lipolysis in healthy humans.

J Clin Endocrinol Metab 2014 Feb 1;99(2):E246-51. Epub 2013 Jan 1.

Department of Internal Medicine I (K.A.I., F.S., T.W., F.M., H.L.), Section of Experimental and Clinical Endocrinology, University of Lübeck, 23538 Lübeck, Germany; Departments of Medicine and Neuroscience and Diabetes, Obesity and Metabolism Institute (DOMI) (T.S., C.B.), Icahn School of Medicine at Mt Sinai, New York, New York 10029; Department of Internal Medicine III (T.S.), Division of Endocrinology and Metabolism, Medical University of Vienna, 1090 Vienna, Austria; Department of Internal Medicine, Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry (M.He., H.-U.H., A.F.), Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich at the University of Tübingen (IDM) (M.He., H.P., H.-U.H., A.F., M.Ha.), fMEG (Fetal Magnetoencephalography) Center (H.P.), and Department of Medical Psychology and Behavioral Neurobiology (M.Ha.), University of Tübingen, 72076 Tübingen, Germany; and German Center for Diabetes Research (DZD) (M.He., H.P., H.-U.H., A.F., M.Ha.), 72076 Tübingen, Germany.

Context: Insulin infused into the central nervous system of rats suppresses lipolysis in white adipose tissue, indicating a role of brain insulin in regulating systemic lipid metabolism.

Objective: We investigated whether central nervous insulin delivery suppresses lipolysis in healthy humans.

Design: Placebo-controlled, balanced within-subject comparisons were performed in both a main and an independent corroborative experiment. SETTING/PARTICIPANTS/INTERVENTION: Two groups of healthy volunteers were examined at the German University Clinics of Lübeck and Tübingen, respectively, with molecular analyses taking place at Mt Sinai School of Medicine (New York, New York). The 14 healthy male subjects of the main study and the 22 women and 5 men of the corroborative study each received 160 IU of human insulin intranasally.

Main Outcome Measures: In the main study, we measured systemic levels of free fatty acids (FFAs), triglycerides, and glycerol and the rate of appearance of deuterated glycerol as an estimate of lipolysis before and after intranasal insulin administration. We also analyzed the expression of key lipolytic enzymes in sc fat biopsies and measured blood glucose and glucoregulatory hormones. In the corroborative study, FFA concentrations were assessed before and after intranasal insulin administration.

Results: In the main experiment, intranasal insulin suppressed circulating FFA concentrations and lipolysis (rate of appearance of deuterated glycerol) in the absence of significant changes in circulating insulin levels. Lipolytic protein expression in sc adipose tissue was not affected. The corroborative study confirmed that intranasal insulin lowers systemic FFA concentrations.

Conclusions: Our findings indicate that brain insulin controls systemic lipolysis in healthy humans by predominantly acting on non-sc adipose tissue.
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February 2014

Experimental hyperleptinemia acutely increases vasoconstrictory sympathetic nerve activity in healthy humans.

J Clin Endocrinol Metab 2013 Mar 7;98(3):E491-6. Epub 2013 Feb 7.

Department of Internal Medicine I, University Hospital of Schleswig-Holstein, Campus Lübeck, D-23538 Lübeck, Germany.

Background: Obesity and arterial hypertension are tightly connected. Obese individuals show significant elevation of vasoconstrictory muscle sympathetic nerve activity (MSNA). Obesity-related hyperleptinemia might play a key role in mediating these effects. Leptin is synthesized in proportion to body fat mass and activates SNA in animal models. In humans, however, direct evidence linking hyperleptinemia to sympathetic activation has not yet been established. In the present study, we characterize the effects of acute hyperleptinemia on microneurographically recorded SNA in humans.

Methods: In a balanced, double-blind crossover design, 12 healthy normal-weight males received an iv bolus of leptin or placebo. MSNA (bursts per minute) was continuously recorded using a microneurographic technique. Ten-minute periods were analyzed at resting periods before (t-100) and at 20 (t20), 60 (t60), and 140 (t140) minutes after substance administration. Blood pressure and heart rate (HR) were recorded simultaneously.

Results: Baseline values of MSNA, blood pressure, and HR were comparable in both conditions (MSNA: t-100, 24.3 ± 1.6 vs 22.7 ± 1.7, not significant). After application of leptin, MSNA showed a significant increase (t20, 31.0 ± 1.9 vs. 24.9 ± 1.8, P = .05) that persisted until the end of the experiment (t60, P = .008; t140, P = .004). There were no significant changes in blood pressure and HR.

Conclusions: Acute experimental hyperleptinemia has significant central nervous excitatory effects on vasoconstrictory sympathetic outflow as measured by MSNA in healthy men. These results suggest that leptin acts as an important mediator linking obesity to elevated MSNA and potentially to the development of hypertension.
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March 2013

Ghrelin modulates baroreflex-regulation of sympathetic vasomotor tone in healthy humans.

Am J Physiol Regul Integr Comp Physiol 2012 Jun 4;302(11):R1305-12. Epub 2012 Apr 4.

Univ. of Luebeck, Dept. of Internal Medicine I, Ratzeburger Allee 160, D-23538 Luebeck, Germany.

Ghrelin, a neuropeptide originally known for its growth hormone-releasing and orexigenic properties, exerts important pleiotropic effects on the cardiovascular system. Growing evidence suggests that these effects are mediated by the sympathetic nervous system. The present study aimed at elucidating the acute effect of ghrelin on sympathetic outflow to the muscle vascular bed (muscle sympathetic nerve activity, MSNA) and on baroreflex-mediated arterial blood pressure (BP) regulation in healthy humans. In a randomized double-blind cross-over design, 12 lean young men were treated with a single dose of either ghrelin 2 μg/kg iv or placebo (isotonic saline). MSNA, heart rate (HR), and BP were recorded continuously from 30 min before until 90 min after substance administration. Sensitivity of arterial baroreflex was repeatedly tested by injection of vasoactive substances based on the modified Oxford protocol. Early, i.e., during the initial 30 min after ghrelin injection, BP significantly decreased together with a transient increase of MSNA and HR. In the course of the experiment (>30 min), BP approached placebo level, while MSNA and HR were significantly lower compared with placebo. The sensitivity of vascular arterial baroreflex significantly increased at 30-60 min after intravenous ghrelin compared with placebo, while HR response to vasoactive drugs was unaltered. Our findings suggest two distinct phases of ghrelin action: In the immediate phase, BP is decreased presumably due to its vasodilating effects, which trigger baroreflex-mediated counter-regulation with increases of HR and MSNA. In the delayed phase, central nervous sympathetic activity is suppressed, accompanied by an increase of baroreflex sensitivity.
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June 2012