Flow-volume curves as measurement of respiratory mechanics during ventilatory support:The effect of the exhalation valve

Objective: To assess the feasibility of expiratory flow-volume curves as a measurement of respiratory mechanics during ventilatory support: to what extent is the shape of the curve affected by the exhalation valve of the ventilator? Design: Prospective, comparative study. Setting: Medical intensive care unit of a university hospital. Patients: 28 consecutive patients with various conditions, mechanically ventilated with both the Siemens Servo 900C and 300 ventilators, were studied under sedation and paralysis. Interventions: The ventilator circuit was intermittently disconnected from the ventilator at end-inspiration in order to obtain flow-volume curves with and without the exhalation valve in place. Measurements and results: Peak flow (PEF) and the slope of the flow-volume curve during the last 50% of expired volume (SF50) were obtained both with and without the exhalation valve in place. The exhalation valve caused a significant reduction in peak flow of 0.3 l/s (from 1.27 to 0.97 l/s) with the Siemens Servo 900 C ventilator and of 0.42 l/s (from 1.36 to 0.94 l/s) with the Siemens Servo 300 ventilator (p &lt; 0.001). The SF50 was not affected. Conclusion: In mechanically ventilated patients, the exhalation valve causes a significant reduction in peak flow, but does not affect the SF50. This study further suggests that the second part of the expiratory flow-volume curve can be used to estimate patients' respiratory mechanics during ventilatory support.</p

Breast cancer radiotherapy and the risk of acute coronary events - insights from a process oriented model

BACKGROUND AND PURPOSE: Acute coronary events (ACEs) are considered the most important side effect of radiotherapy (RT) for breast cancer but underlying mechanisms still have to be identified. Process oriented models mathematically describe the development of disease and provide a link between mechanisms and subsequent risk. Here, this link is exploited to learn about the underlying mechanisms from the observed age-time patterns of ACE risk. MATERIALS AND METHODS: A process oriented model of atherosclerosis and subsequent ACEs was applied to a contemporary breast cancer cohort of 810 patients with measurements of coronary artery calcification. Patients with prior ischemic heart disease were excluded. The process oriented model describes disease development as a series of different stages. Different variants of the model were fitted to the data. In each variant, one stage was assumed to be accelerated in relation to mean heart dose. RESULTS: During a mean follow up of 9.1 years, 25 ACEs occurred. The model reproduced the prevalence and associated risk of coronary calcifications. Mean heart dose significantly improved the fit only when implemented as affecting a late stage of atherosclerosis on already existing, complicated lesions (achieving p = 0.007). This can be understood by atherosclerosis being a slowly progressing disease. Therefore, an increase of ACEs few years after RT requires advanced atherosclerosis at the time of RT. CONCLUSION: Risk of ACE increases within few years in patients with advanced atherosclerosis at RT. Therefore, patients should be assessed for cardiovascular risk, and also elderly patients need to be considered for heart sparing techniques

The Importance of Radiation Dose to the Atherosclerotic Plaque in the Left Anterior Descending Coronary Artery for Radiation-Induced Cardiac Toxicity of Breast Cancer Patients?

IMPORTANCE: Radiation-induced acute coronary events (ACEs) may occur as treatment-related late side effect of breast cancer (BC) radiation. However, the underlying mechanisms behind this radiation-induced cardiac disease remains to be determined. OBJECTIVE: The objective of this study was to test the hypothesis that radiation dose to calcified atherosclerotic plaques in the left anterior descending coronary artery (LAD) is a better predictor for ACEs than radiation dose to the whole heart or left ventricle in BC patients treated with radiotherapy (RT). DESIGN, SETTING, PARTICIPANTS, AND MAIN OUTCOMES AND MEASURES: The study cohort consisted of 910 BC patients treated with postoperative RT after breast conserving surgery. In total, 163 patients had an atherosclerotic plaque in the LAD. The endpoint was the occurrence of an ACE after treatment. For each individual patient, the mean heart dose (MHD), volume of the left ventricle receiving ≥ 5 Gy (LV-V5), mean LAD dose and mean dose to calcified atherosclerotic plaques in the LAD, if present, were acquired based on planning CT-scans. Cox-regression analysis was used to analyse the effects on the cumulative incidence of ACEs. RESULTS: The median follow-up time was 9.2 years (range: 0.1-14.3 years). In total, 38 patients (4.2%) developed an ACE during follow-up. For patients with an atherosclerotic plaque (n=163) the mean dose to the atherosclerotic plaque was the strongest predictor for ACE, even after correction for cardiovascular risk factors (HR: 1.269 (95% CI: 1.090-1.477), P=0.002). The LV-V5 was associated with ACEs in patients without atherosclerotic plaques in the LAD (n=680) (hazard ratio (HR): 1.021 (95% CI: 1.003-1.039; P=0.023). CONCLUSION AND RELEVANCE: The results of this study suggest that radiation dose to pre-existing calcified atherosclerotic plaques in the LAD is strongly associated with the development of ACEs in BC patients

Validation of separate multi-atlases for auto segmentation of cardiac substructures in CT-scans acquired in deep inspiration breath hold and free breathing

Background and purpose: Developing NTCP-models for cardiac complications after breast cancer (BC) radiotherapy requires cardiac dose-volume parameters for many patients. These can be obtained by using multi-atlas based automatic segmentation (MABAS) of cardiac structures in planning CT scans. We investigated the relevance of separate multi-atlases for deep inspiration breath hold (DIBH) and free breathing (FB) CT scans. Materials and methods: BC patients scanned in DIBH (n = 10) and in FB (n = 20) were selected to create separate multi-atlases consisting of expert panel delineations of the whole heart, atria and ventricles. The accuracy of atlas-generated contours was validated with expert delineations in independent datasets (n = 10 for DIBH and FB) and reported as Dice coefficients, contour distances and dose-volume differences in relation to interobserver variability of manual contours. Dependency of MABAS contouring accuracy on breathing technique was assessed by validation of a FB atlas in DIBH patients and vice versa (cross validation). Results: For all structures the FB and DIBH atlases resulted in Dice coefficients with their respective reference contours > 0.8 and average contour distances < 2 mm smaller than slice thickness of (CTs). No significant differences were found for dose-volume parameters in volumes receiving relevant dose levels (WH, LV and RV). Accuracy of the DIBH atlas was at least similar to, and for the ventricles better than, the interobserver variation in manual delineation. Cross-validation between breathing techniques showed a reduced MABAS performance. Conclusion: Multi-atlas accuracy was at least similar to interobserver delineation variation. Separate atlases for scans made in DIBH and FB could benefit atlas performance because accuracy depends on breathing technique

Exploring the Origin of the Bering Sea: Initial Results of Cruise SO249-2 (17th July – 13th August 2016)

The Bering Sea is one of the largest marginal seas on Earth with still poorly understood origin and evolution. Cruise SO249-2 of the German research vessel Sonne explored the western half of Bering Sea by multibeam mapping, sediment profiling and dredge sampling in the framework of the joint German-Russian-U.S. American project BERING. Focus areas were A) the Chukotka-Beringian margins, once the possible site of Cretaceous arc volcanism prior to Eocene initiation of the Aleutian arc, B) the enigmatic Shirshov Ridge, separating the Komandorsky from the Aleutian Basin, C) Beta Rise, an area of anomalous high heat flow in the Komandorsky basin, D) the Volcanlogists Massif and adjacent volcanic and tectonic structures and E) the Komandorsky block, the westernmost section of the modern arc.....

Validation and Modification of a Prediction Model for Acute Cardiac Events in Patients With Breast Cancer Treated With Radiotherapy Based on Three-Dimensional Dose Distributions to Cardiac Substructures

PurposeA relationship between mean heart dose (MHD) and acute coronary event (ACE) rate was reported in a study of patients with breast cancer (BC). The main objective of our cohort study was to validate this relationship and investigate if other dose-distribution parameters are better predictors for ACEs than MHD.Patients and MethodsThe cohort consisted of 910 consecutive female patients with BC treated with radiotherapy (RT) after breast-conserving surgery. The primary end point was cumulative incidence of ACEs within 9 years of follow-up. Both MHD and various dose-distribution parameters of the cardiac substructures were collected from three-dimensional computed tomography planning data.ResultsThe median MHD was 2.37 Gy (range, 0.51 to 15.25 Gy). The median follow-up time was 7.6 years (range, 0.1 to 10.1 years), during which 30 patients experienced an ACE. The cumulative incidence of ACE increased by 16.5% per Gy (95% CI, 0.6 to 35.0; P = .042). Analysis showed that the volume of the left ventricle receiving 5 Gy (LV-V5) was the most important prognostic dose-volume parameter. The most optimal multivariable normal tissue complication probability model for ACEs consisted of LV-V5, age, and weighted ACE risk score per patient (c-statistic, 0.83; 95% CI, 0.75 to 0.91).ConclusionA significant dose-effect relationship was found for ACEs within 9 years after RT. Using MHD, the relative increase per Gy was similar to that reported in the previous study. In addition, LV-V5 seemed to be a better predictor for ACEs than MHD. This study confirms the importance of reducing exposure of the heart to radiation to avoid excess risk of ACEs after radiotherapy for BC. (C) 2017 by American Society of Clinical Oncology.</p