Biomedical subjects

Hendrik Schmidt

Publications and source records attributed to Hendrik Schmidt.

18 recordsLinked to original sources

PubMed2007

Application of a calibration method provides more realistic results for a finite element model of a lumbar spinal segment.

BACKGROUND: An important step in finite element modeling is the process of validation to derive clinical relevant data. It can be assumed that defect states of a finite element model, which have not been validated before, may predict wrong results. The purpose of this study was to show the differences in accuracy between a calibrated and a non-calibrated finite element model of a lumbar spinal segment for different clinical defects. METHODS: For this study, two geometrically identical finite element models were used. An in vitro experiment was designed, deriving data for the calibration. Frequently used material properties were obtained from the literature and transferred into the non-calibrated model. Both models were validated on three clinical defects: bilateral hemifacetectomy, nucleotomy and interspinous defects, whereas in vitro range of motion data served as control points. Predictability and accuracy of the calibrated and non-calibrated finite element model were evaluated and compared. FINDINGS: Both finite element models could mimic the intact situation with a good agreement. In the defects, the calibrated model predicted motion behavior with excellent agreement, whereas the non-calibrated model diverged greatly. INTERPRETATION: Investigating the biomechanical performance of implants and load distribution of different spinal structures by numerical analysis requires not only good agreement with the intact segment, but also with the defect states, which are initiated prior to implant insertion. Because of more realistic results the calibration method may be recommended, however, it is more time consuming.

Finite Element Analysis↗

PubMed2006

Biomechanical evaluation of a new total posterior-element replacement system.

STUDY DESIGN: In vitro study to characterize the flexibility of a new total posterior-element system when instrumented to L4-L5 segments. OBJECTIVE: The goal of this in vitro study was to investigate whether an optimized version of the TOPS implant (Impliant Ltd., Ramat Poleg, Israel) is capable to restore the physiologic motion characteristic of a spinal segment after facetectomy. SUMMARY OF BACKGROUND DATA: The TOPS implant is designed to replace the posterior elements of a functional spinal unit, to provide flexible restabilization and spinal alignment, while maintaining the intervertebral disc. The implant is composed of bilateral pedicle screws, connected with 2 crossbars in the transversal plane. The crossbars are joined together by an elastic element capable of transmitting tensile and compressive loads, as well as shear forces. METHODS: Six human cadaver specimens (L3-S1) (median age 61 years: minimum 47 and maximum 74 years) were used for this in vitro experiment. The specimens were loaded with pure moments of +/-7.5 Nm in flexion/extension, lateral bending, and axial rotation. The following states were investigated: (1) intact; (2) after bilateral laminectomy, including facetectomy of the lower facet joints, of the upper vertebra L4; and (3) after device implantation. The range of motion (ROM), neutral zone, and intradiscal pressure were determined from a third cycle. In a second step, the ROM in axial rotation was determined as a function of different flexion/extension postures. RESULTS: In the neutral position, the laminectomy and facetectomy increased the median values of the ROM in flexion plus extension, lateral bending right plus left, and significantly in axial rotation left plus right from: 8.2 degrees, 7.6 degrees, 3.6 degrees to 12.1 degrees, 8.5 degrees, and 8.5 degrees (Wilcoxon signed rank test; P < 0.05). After fixation of the implant, the ROM was again reduced to 6.8 degrees, 7.8 degrees, and 3.8 degrees. In a flexed posture, the ROM in axial rotation was slightly increased compared to the neutral position. With increasing extension, the axial rotation decreased linearly from 3.7 degrees in neutral position to 2.3 degrees in 4 degrees extension in the segment L4-L5. The characteristic of the intradiscal pressure versus load with the implant was similar to that of the intact specimen. CONCLUSION: The TOPS implant almost ideally restored the ROM in lateral bending and axial rotation compared to that of the intact specimen. In the sagittal plane, 85% of the intact ROM could be obtained. The ROM in axial rotation as a function of flexion and extension angle also mimics the biomechanical behavior of the posterior complex of a lumbar spine. This relationship between ROM and posture emphasizes the importance of a proper implantation.

Aged↗

PubMed2006

Secretory lysosomes and their cargo in T and NK cells.

Secretory lysosomes are specialized organelles that combine catabolic functions of conventional lysosomes with an inducible secretory potential. They are present in various hematopoietic cell types commonly characterized by the need for rapid mobilization and secretion of effector proteins. As an example, the cytotoxic effector function of T cells and natural killer cells strictly depends on the activation-dependent mobilization of such vesicles to the cytotoxic immunological synapse. This review focuses on some molecules that have been identified as cargo of secretory lysosomes and which play a major role in effector function of CTL and NK cells. We also briefly point to the fact that the dysregulation of formation and transport of secretory vesicles is causative for severe immunodeficiencies and autoimmunity observed in patients and also in mice that have been used as representative model systems to analyze the pathophysiological relevance of secretory vesicles in vivo.

Animals↗

PubMed2006

Association of statin therapy and increased survival in patients with multiple organ dysfunction syndrome.

OBJECTIVE: The multiple organ dysfunction syndrome (MODS) is the sequential failure of several organ systems after a trigger event, such as sepsis, pneumonia or cardiogenic shock. Even today, mortality is high. Statin therapy is associated with reduction of inflammation and subsequent rates of severe sepsis and ICU admission of patients admitted to hospital with presumed or documented acute bacterial infection. Our study aimed to characterize a potential survival benefit by statin therapy in MODS patients. DESIGN: Retrospective cohort study. SETTING: Twelve-bed medical intensive care unit in a university center. PATIENTS: Forty score-defined MODS patients under statin treatment and 80 age- and sex-matched score-defined MODS patients without statin treatment. Inclusion criterion was an APACHE II score > or = 20 at admission to ICU. INTERVENTIONS: Assessment of statin treatment and calculation of disease severity by scoring. The patients were followed up for 28-day mortality as well as for hospital mortality. MEASUREMENTS AND RESULTS: The MODS severity was equally pronounced in both groups. There were 42/80 deaths in the group without statin treatment and 13/40 deaths in the statin group (28-day mortality 53% vs. 33%, p = 0.03). Cox proportional hazard analysis revealed a hazard ratio of 0.53 (95% CI 0.29-0.99, p = 0.04). Hospital mortality was calculated at 72% (non-statin group) vs. 35% (statin group; chi-square = 15.6, p < 0.0001). The overall hospital mortality was 60%. CONCLUSIONS: Patients under statin treatment developing MODS might have a better outcome than patients without statin therapy, probably by reduction of inflammatory responses and increase of vagal activity in MODS.

Atorvastatin↗

PubMed2006

Stepwise reduction of functional spinal structures increase vertebral translation and intradiscal pressure.

To date, there are only a few studies that provide data to efficiently calibrate finite element models for the spine due to its complexity. In a recent study, we quantified the range of motion rotation and the lordosis angle. This paper provides complementary results regarding two more parameters, intradiscal pressure and vertebral translation. All parameters were obtained as a function of stepwise anatomical reduction, loading direction and magnitude. Eight lumbar spinal segments (L4-5) with a median age of 52 years (38-59 years) and no signs of disc degeneration were used for the in vitro testing. A miniaturized pressure probe was implanted into the nucleus. An ultrasound-based motion-tracking system was employed to record spatial movements of several landmarks on the specimens. The center of L4, the anterior, posterior, left and right point of the lower endplate of L4 were digitized as landmarks and its translation was determined. Specimens were loaded with pure moments (1-10Nm) in the three principal anatomical planes at a loading rate of 1.0 degrees /s. Anatomy was stepwise reduced by cutting different ligaments, facet capsules and joints and removing nucleus. Translation analysis showed that the L4 center point had its largest displacement in sagittal direction and almost none vertically. Removal of the supra- and interspinous, flaval ligaments showed a slight increase and further removal of structures, a higher increase of translation. Axial rotation also was accompanied with L4 to elevate when torsion was applied. This effect was found to be larger with progressing defects. Nucleotomy exhibited the most unstable situation for specimens. Results of the intradiscal pressure indicated a large increase after removing the facet capsules and joints. Furthermore, it was found that intradiscal pressure correlated well with data of range of motion for rotation. Predicting and simulating clinical defects, surgical intervention or treatment methods requires a well performed calibration based on in vitro data, whereas it is important to adapt all including structures with as many known parameters as possible. Results provided by these studies may be used as a database for researchers aiming to calibrate or validate finite element models of L4-5 segments.

Adult↗

PubMed2006

Stepwise reduction of functional spinal structures increase range of motion and change lordosis angle.

Many investigators have performed studies on specific defect situations or determined the contribution on isolated structures. Investigating the contribution of functional structures requires obtaining the kinematic response directly on spinal segments. The purpose of this study was to quantify the function of anatomical components on lumbar segments for different loading magnitudes. Eight spinal segments (L4-5) with a median age of 52 years (ranging from 38 to 59 years) and a low degree of disc degeneration were utilized for the in vitro testing. Specimens were mounted in a custom-built spine tester and loaded with pure moments (1-10 N m) to move within three anatomical planes at a loading rate of 1.0 degrees /s. Anatomy was successively reduced by: ligaments, facet capsules, joints and nucleus. Data were evaluated for range of motion, neutral zone and lordosis angle. Transection of posterior ligaments predominantly increased specimen flexion for all bending moments applied. Supraspinous ligament also indicated to resist in extension slightly, whereas the facet capsules did not. Facet joints contributed to axial rotation, but not in lateral bending. The anterior longitudinal ligament was found to slightly resist in axial rotation, but strongly in extension. Nucleotomy caused largest increase of all movements. The unloaded posture of the specimens changed after ligament dissection, indicating ligament pretension. The region of lumbar spine is interesting for finite element (FE) simulation due to the high evidence of disc degeneration and injuries. This study may help to understand the function of specific anatomical structures and assists in FE model calibration. We suggest to start a calibration procedure for such models with the smallest functional structure (annulus) and to cumulatively add further structures.

Adult↗

PubMed2006

Autonomic information flow improves prognostic impact of task force HRV monitoring.

Heart rate variability (HRV) represents the cardiovascular control mediated by the autonomic nervous system and other mechanisms. In the established task force HRV monitoring different cardiovascular control mechanisms can approximately be identified at typical frequencies of heart rate oscillations by power spectral analysis. HRV measures assessing complex and fractal behavior partly improved clinical risk stratification. However, their relationship to (patho-)physiology is not sufficiently explored. Objective of the present work is the introduction of complexity measures of different physiologically relevant time scales. This is achieved by a new concept of the autonomic information flow (AIF) analysis which was designed according to task force HRV. First applications show that different time scales of AIF improve the risk stratification of patients with multiple organ dysfunction syndrome and cardiac arrest patients in comparison to standard HRV. Each group's significant time scales correspond to their respective pathomechanisms.

Adult↗

PubMed2006

Application of a new calibration method for a three-dimensional finite element model of a human lumbar annulus fibrosus.

BACKGROUND: Major deficits of many finite element models of the lumbar spine are the oversimplification, assumed constellation of the material properties or the insufficiently performed calibration using experimental in vitro data. The aim of this study was, to develop a method for calibrating the two-composite structure of the annulus fibrosus, the ground substance and collagen fibers. METHODS: For that purpose, a three-dimensional, non-linear finite element model of a denucleated intervertebral disc with the adjacent vertebral bodies (L4-L5) was created. Previously performed in vitro experiments provided experimental data for the range of motion in each load direction, needed for calibration. A method was developed to determine the individual contribution of the fibers and the ground substance for bending moments with four different magnitudes (2.5, 5.0, 7.5 and 10 Nm). For each bending moment, the stiffness of fibers was varied to approximate the Young's modulus of the ground substance in order to fulfil the required range of motion obtained from in vitro results within an accuracy of 99%. RESULTS: Infinite material parameter combinations of collagen fibers and ground substance led to the same range of motion, which were different for each bending moment. However, there was only one combination, which was valid for all applied bending moments; and in all load direction. INTERPRETATION: This calibration method was performed on range of motion data; however, the procedure could also be applied to other loading scenarios and measurement parameters like disc bulge, translation and intradiscal pressure.

Calibration↗

PubMed2006

Analysis of complex physiological systems by information flow: a time scale-specific complexity assessment.

In the last two decades conventional linear methods for biosignal analysis have been substantially extended by non-stationary, non-linear, and complexity approaches. So far, complexity is usually assessed with regard to one single time scale, disregarding complex physiology organised on different time scales. This shortcoming was overcome and medically evaluated by information flow functions developed in our research group in collaboration with several theoretical, experimental, and clinical partners. In the present work, the information flow is introduced and typical information flow characteristics are demonstrated. The prognostic value of autonomic information flow (AIF), which reflects communication in the cardiovascular system, was shown in patients with multiple organ dysfunction syndrome and in patients with heart failure. Gait information flow (GIF), which reflects communication in the motor control system during walking, was introduced to discriminate between controls and elderly patients suffering from low back pain. The applications presented for the theoretically based approach of information flow confirm its value for the identification of complex physiological systems. The medical relevance has to be confirmed by comprehensive clinical studies. These information flow measures substantially extend the established linear and complexity measures in biosignal analysis.

Adult↗

PubMed2006

Complex autonomic dysfunction in cardiovascular, intensive care, and schizophrenic patients assessed by autonomic information flow.

BACKGROUND: The cardiovascular control system is mediated by mechanisms acting at different time scales, such as heart period, vagal, sympathetic, and other slower controllers. Since these elements are interrelated in a complex manner, classical control theory fails and information-based description, based on autonomic information flow (AIF) functions, is appropriate. We investigated the hypothesis that AIF functions of typical time scales specifically characterize autonomic dysfunction and prognosis. MATERIALS AND METHODS: Holter recordings of patients with multiple organ dysfunction syndrome (MODS) (26 survivors, 10 non-survivors), heart failure (13 low risk, 13 high risk of cardiac arrest), idiopathic dilated cardiomyopathy (IDC) (26 low risk, 11 high risk), after abdominal aorta surgery (AAS) [32 with length of stay in hospital (LOS) >7 days; 62 with LOS < or =7 days] or with schizophrenia (n=20) were assessed and compared to 20 control subjects. RESULTS: We found different AIF time scales discriminating risk. AIF measures of heart beat period had predominant prognostic value in heart failure patients, those of vagal communication in MODS and IDC, and those of long-term communication after AAS. Schizophrenic patients were discriminated from controls by vagally mediated communication. CONCLUSION: Different time scales of AIF represent specific pathophysiological aspects of altered complex autonomic control (communication) and consequently have predictive implications.

Autonomic Nervous System↗

PubMed2006

Attenuated autonomic function in multiple organ dysfunction syndrome across three age groups.

Multiple organ dysfunction syndrome (MODS) is the failure of several organs after a trigger event. The mortality is high, at up to 70%. We hypothesize that autonomic dysfunction may substantially contribute to the development of MODS and speculate that there is an age dependence of autonomic dysfunction in MODS. A total of 90 consecutively admitted MODS patients were assigned to this study. Three variables of autonomic function were analyzed: heart rate variability (HRV), baroreflex sensitivity (BRS) and chemoreflex sensitivity (CRS). The patient cohort was divided into three age groups. The main finding was that BRS, CRS and almost all indices of HRV were attenuated in comparison to normal range data and there was no age dependence for HRV indices or CRS, but there was for BRS. In conclusion, autonomic function in MODS is attenuated. The influence of MODS on autonomic function overwhelms the age dependence of autonomic function observed in healthy subjects.

Aging↗

PubMed2005

Fitting of random tessellation models to keratin filament networks.

The role of specific structural patterns in keratin filament networks for regulating biophysical properties of epithelial cells is poorly understood. This is at least partially due to a lack of methods for the analysis of filament network morphology. We have previously developed a statistical approach to the analysis of keratin filament networks imaged by scanning electron microscopy. The segmentation of images in this study resulted in graph structures, i.e. tessellations, whose structural characteristics are now further investigated by iteratively fitting geometrical statistical models. An optimal model as well as corresponding optimal parameters are detected from a given set of possible random tessellation models, i.e. Poisson-Line tessellations (PLT), Poisson-Voronoi tessellations (PVT) and Poisson-Delaunay tessellations (PDT). Using this method, we investigated the remodeling of keratin filament networks in pancreatic cancer cells in response to transforming growth factor alpha (TGFalpha), which is involved in pancreatic cancer progression. The results indicate that the fitting of random tessellation models represents a suitable method for the description of complex filament networks.

Algorithms↗

PubMed2005

Analysis of the influence of disc degeneration on the mechanical behaviour of a lumbar motion segment using the finite element method.

Compared to a healthy intervertebral disc, the geometry and the material properties of the involved tissues are altered in a degenerated disc. It is not completely understood how this affects the mechanical behaviour of a motion segment. In order to study the influence of disc degeneration on motion segment mechanics a three-dimensional, nonlinear finite element model of the L3/L4 functional unit was used. Different grades of disc degeneration were simulated by varying disc height and bulk modulus of the nucleus pulposus. The model was loaded with pure moments of 10Nm in the three main anatomic planes. The finite element model predicted the same trends for intersegmental rotation and intradiscal pressure as described in the literature for in vitro studies. A comparison between calculated intersegmental rotation and experimental data showed a mean difference of 1.9 degrees while the mean standard deviation was 2.5 degrees . A mildly degenerated disc increases intersegmental rotation for all loading cases. With further increasing disc degeneration intersegmental rotation is decreased. For axial rotation the decrease takes place in the final stage. Intradiscal pressure is lower while facet joint force and maximum von Mises stress in the annulus are higher in a degenerated compared to a healthy disc.

Biomechanical Phenomena↗

PubMed2005

Prognostic impact of autonomic information flow in multiple organ dysfunction syndrome patients.

BACKGROUND: Multiple organ dysfunction syndrome (MODS) is the sequential failure of several organ systems after a trigger event, like cardiogenic shock or decompensated heart failure. Mortality is high, up to 70%. Autonomic dysfunction (AD) may substantially contribute to the development of MODS. In cardiology, it has recently been shown that nonlinear parameters could predict mortality. Our study aimed at 1. characterising the complex characteristics of AD of critically ill MODS patients by the nonlinear parameters of autonomic information flow (AIF), 2. comparing AIF with autonomic function of healthy controls, and 3. characterising the accuracy of this parameter in predicting mortality in MODS. METHODS: We enrolled 43 score-defined MODS patients who were consecutively admitted to a twelve-bed medical intensive care unit in a university centre into this prospective outcome study. Additionally, we assigned 50 healthy controls to the study. AIF was assessed as a complexity function of AD using 24-h ECG. Measures of AIF were introduced according to the standard HRV concept. The patients were followed up for 28-day mortality. RESULTS: MODS causes a disorganisation of short term AIF in favour of an enhanced (rigid) long term AIF. Concerning prognosis increased short term AIF was associated with survival. Short term AIF discriminated between MODS survivors and non-survivors at the level of APACHE II score. CONCLUSIONS: This is the first study providing evidence that complex AD of MODS patients is specifically assessed by AIF time scales and that AIF has significant prognostic impact.

Adult↗

PubMed2005

Chemo- and ergoreflexes in health, disease and ageing.

The chemo- and ergoreflexes (muscle receptors) are among the major reflex arches, which adapt the respiratory and the cardiovascular system to the needs of the body and contribute to its homeostasis. The present paper reviews the interplay of these reflexes with other major cardiovascular reflex arches; the methods used for their calculation and their normal range data. The clinical implications of chemoreflex sensitivities and ergoreflexes in chronic heart failure (CHF) as well as the application of chemoreflexes in coronary artery disease, sudden cardiac death and multiple organ dysfunction syndrome are discussed.

Aging↗

PubMed2005

Autonomic dysfunction predicts mortality in patients with multiple organ dysfunction syndrome of different age groups.

OBJECTIVE: Multiple organ dysfunction syndrome (MODS) is the sequential failure of several organ systems after a trigger event, like sepsis or cardiogenic shock. Mortality rate is high, up to 70%. Autonomic dysfunction may substantially contribute to the development of MODS. Our study aimed to characterize a) the spectrum of autonomic dysfunction of critically ill MODS patients; b) whether autonomic dysfunction is different in patients receiving sedation, mechanical ventilation, or catecholamines; c) the age dependency of autonomic dysfunction in MODS; and d) whether autonomic dysfunction predicts mortality in MODS. DESIGN: Prospective cohort study. SETTING: Twelve-bed medical intensive care unit in a university center. PATIENTS: Ninety consecutively admitted score-defined MODS patients. INTERVENTIONS: Assessment of heart rate variability, baroreflex sensitivity, and chemoreflex sensitivity as markers of autonomic dysfunction. The patients were followed for 28-day mortality. MEASUREMENTS AND MAIN RESULTS: Baroreflex sensitivity, chemoreflex sensitivity, and almost all indexes of heart rate variability were attenuated in comparison to normal range data. There was no association between the assessed heart rate variability variables, baroreflex sensitivity or chemoreflex sensitivity, and the presence of sedation or catecholamine therapy. Except for frequency-domain variables, pNN50 (percentage of differences of successive RR intervals differing >50 msecs) and rMSSD (root mean square of successive difference of N-N intervals), none of the measured variables were related to the presence of mechanical ventilation. Age dependency was detected for baroreflex sensitivity but not for heart rate variability indexes or chemoreflex sensitivity (across ages 24-96 yrs). lnVLF predicted 28-day mortality best in the entire cohort of patients and in a subgroup of patients with cardiogenic-triggered MODS. CONCLUSIONS: Autonomic function of MODS patients is blunted, and this attenuation has prognostic implications. The extensive influence of MODS on autonomic function overwhelms and masks the well-known age dependency of autonomic function seen in healthy persons.

Adult↗

PubMed2005

Optimal maximum tracking rate of dual-chamber pacemakers required by children and young adults for a maximal cardiorespiratory performance.

INTRODUCTION: Children and young adults require a higher maximum tracking rate (MTR) for physical activity. The objective of the present study was to observe whether higher MTR of 170 or 190 beats per minute (bpm) have a positive impact on the maximal cardiorespiratory capacity of children and young adults in comparison with a lower MTR of 140 bpm. METHODS: Fifteen patients with atrioventricular block and normal sinus-node chronotropic function (age 7-24 years) with DDD- (14) or VDD-pacemakers (PM) (1) were enrolled. First, the MTR was adjusted to 140 bpm for 6 weeks and elevated in a second step to 170 or 190 bpm. At the end of each period two cardiopulmonary exercise tests, a 24-hour ECG and a PM test were performed. RESULTS: All patients increased their maximal heart rate (139.0 +/- 1.0 vs 177.0 +/- 10.0 bpm, P < 0.001), peak cardiorespiratory capacity (2.4 +/- 0.6 vs 2.8 +/- 0.7 W/kg, P < 0.001), peak oxygen uptake (28.3 +/- 7.0 vs 35.7 +/- 9.5 mL/kg/min, P < 0.005), and oxygen uptake (23.7 +/- 7.4 vs 29.3 +/- 8.4 mL/kg/min, P < 0.02) at the anaerobic threshold. There were no evident heart rhythm disturbances with elevated MTR. Patients with a Wenckebach behavior of the PM had an attenuated increase of maximal cardiorespiratory performance. CONCLUSION: Children and young adults with DDD-/VDD-PM benefit from an elevated MTR by an increased cardiorespiratory capacity, without having more heart rhythm disturbances. A Wenckebach behavior of the PM should be avoided.

Adolescent↗

PubMed2004

Impaired chemoreflex sensitivity in adult patients with multiple organ dysfunction syndrome--the potential role of disease severity.

OBJECTIVE: The cardiac chemoreflex sensitivity is a powerful predictor of autonomic dysfunction in chronic heart failure and after myocardial infarction. The objective of the present study was to characterize cardiac chemoreflex sensitivity in patients with multiple organ dysfunction syndrome (MODS). We also aimed to elucidate the effect of the severity of MODS on the assessment of cardiac chemoreflex sensitivity. DESIGN: Prospective cohort study. SETTING: Twelve-bed medical intensive care unit in a university center. PATIENTS: Forty consecutively admitted patients with MODS during a 7-month period. Patients with MODS were identified by an APACHE II score of 20 or more. Sepsis was defined as a Sepsis Score, according to Elebute and Stoner, of 12 or more. INTERVENTIONS: The cardiac chemoreflex sensitivity was assessed using the regression of heart interval (ms) versus arterial oxygen pressure (mmHg). MEASUREMENTS AND RESULTS: First, we established a new method to assess cardiac chemoreflex sensitivity and applied it to healthy controls and patients. Second, we found that cardiac chemoreflex sensitivity correlated with the severity of MODS as calculated by the APACHE II score ( r(2)=0.34, p=0.001). This relation was best fitted by a model including minimum heart rate and standard bicarbonate in 24 h ( r(2)=0.5, p<0.001) and Glasgow Coma Scale ( r(2)=0.5, p=0.005). Age, however, did not significantly contribute ( r(2)=0.001, p=0.8). CONCLUSIONS: The calculation of cardiac chemoreflex sensitivity enabled us to quantify an important component of the cardiorespiratory interactions in patients with MODS. Severity of illness was a more pronounced determinant of impaired cardiac chemoreflex sensitivity than age. The quantification of the cardiorespiratory interactions by measuring the cardiac chemoreflex sensitivity has potential to identify a subgroup of patients with worse prognosis.

APACHE↗