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Biomedical subjects

Vladimir Kaplan

Publications and source records attributed to Vladimir Kaplan.

9 recordsLinked to original sources
PubMed2005

Monitoring carbon dioxide tension and arterial oxygen saturation by a single earlobe sensor in patients with critical illness or sleep apnea.

OBJECTIVES: The purpose of the study was to evaluate a novel, combined sensor for transcutaneous monitoring of arterial oxygen saturation and carbon dioxide tension. DESIGN: The new monitoring technique was compared to established reference methods. SETTING: ICU and sleep laboratory of a university hospital. PATIENTS: Eighteen critically ill adult patients with acute respiratory failure or heart failure, and 12 patients with sleep apnea (mean [+/- SD] apnea/hypopnea index, 43 +/- 24 events per hour). MEASUREMENTS: Continuous measurements were performed over several hours by the novel heated (temperature, 42 degrees C) earlobe sensor (TOSCA; Linde Medical Sensors; Basel, Switzerland), incorporating electrochemical and optical elements for carbon dioxide measurement (PtcCO2) and pulse oximetry (SpO2), respectively. The data were compared to the results of repeated arterial blood gas analyses in critically ill patients and to simultaneous nocturnal pulse oximetry performed with different devices with earlobe or finger sensors in sleep apnea patients. RESULTS: In critically ill patients, the mean difference and limits of agreement (bias +/- 2 SDs) of transcutaneous PtcCO2 vs arterial PaCO2 were 3 +/- 7 mm Hg; the corresponding values for changes in PtcCO2 vs PaCO2 were 1 +/- 6 mm Hg. The bias +/- 2 SDs for pulse oximetric SpO2 vs arterial oxygen saturation (SaO2) were 1 +/- 4%. In sleep apnea patients, the combined earlobe sensor identified more transient oxygen desaturations, and the rate of change in oxygen saturation during events was greater compared to those with other tested pulse oximeters, indicating a faster response. CONCLUSIONS: Due to its ability to accurately assess both ventilation and oxygenation by a single transcutaneous sensor, the described noninvasive monitoring technique is a valuable tool for respiratory monitoring with potential applications in critical care and sleep medicine.

Acute Disease↗
PubMed2004

Dynamic microsimulation to model multiple outcomes in cohorts of critically ill patients.

BACKGROUND: Existing intensive care unit (ICU) prediction tools forecast single outcomes, (e.g., risk of death) and do not provide information on timing. OBJECTIVE: To build a model that predicts the temporal patterns of multiple outcomes, such as survival, organ dysfunction, and ICU length of stay, from the profile of organ dysfunction observed on admission. DESIGN: Dynamic microsimulation of a cohort of ICU patients. SETTING: 49Forty-nine ICUs in 11 countries. PATIENTS: One thousand four hundred and forty-nine patients admitted to the ICU in May 1995. INTERVENTIONS: None. MODEL CONSTRUCTION: We developed the model on all patients (n=989) from 37 randomly-selected ICUs using daily Sequential Organ Function Assessment (SOFA) scores. We validated the model on all patients (n=460) from the remaining 12 ICUs, comparing predicted-to-actual ICU mortality, SOFA scores, and ICU length of stay (LOS). MAIN RESULTS: In the validation cohort, the predicted and actual mortality were 20.1% (95%CI: 16.2%-24.0%) and 19.9% at 30 days. The predicted and actual mean ICU LOS were 7.7 (7.0-8.3) and 8.1 (7.4-8.8) days, leading to a 5.5% underestimation of total ICU bed-days. The predicted and actual cumulative SOFA scores per patient were 45.2 (39.8-50.6) and 48.2 (41.6-54.8). Predicted and actual mean daily SOFA scores were close (5.1 vs 5.5, P=0.32). Several organ-organ interactions were significant. Cardiovascular dysfunction was most, and neurological dysfunction was least, linked to scores in other organ systems. CONCLUSIONS: Dynamic microsimulation can predict the time course of multiple short-term outcomes in cohorts of critical illness from the profile of organ dysfunction observed on admission. Such a technique may prove practical as a prediction tool that evaluates ICU performance on additional dimensions besides the risk of death.

Cohort Studies↗
PubMed2004

Variability of inspiratory conductance quantifies flow limitation.

In the present study, our aim was to investigate whether the variability of conductance over the course of inspiration reflects flow limitation. Pressure/flow conditions in the upper airway were modelled by a collapsible tube within a rigid chamber and a pump simulating respiration. Instantaneous conductance was estimated every 20 ms as flow/resistive pressure, and its variability during inspiration expressed as the 90th/50th percentile ratio. Accuracy of this ratio to quantify flow limitation was evaluated by observing whether it changed predictably with adjustments of model parameters. To illustrate the potential of this ratio to quantify flow limitation in a clinical setting, we recorded pneumotachographic airflow and oesophageal pressure in 11 patients with obstructive sleep apnoea during nasal continuous positive airway pressure (CPAP) ventilation, and observed changes in the 90th/50th percentile ratio of inspiratory lung conductance induced by mask pressure titration. Rising pressure surrounding the collapsible tube from subatmospheric to positive values induced progressive inspiratory collapse and increased 90th/50th percentile ratios of inspiratory conductance as predicted. Changes in flow limitation induced by other model modifications were also correctly tracked by the 90th/50th conductance percentile ratio. Increasing mask pressure during CPAP ventilation in sleep apnoea patients from subtherapeutic to therapeutic pressure levels was associated with the expected decrease in the 90th/50th percentile ratio of inspiratory lung conductance from a mean of 6.5+/-3.1 to 1.6+/-0.3 ( P <0.001). We conclude that variability of inspiratory conductance quantified by the 90th/50th percentile ratio may serve as a measure of flow limitation that is independent of the absolute value of conductance.

Airway Resistance↗
PubMed2004

Comparison of Cox and Gray's survival models in severe sepsis.

BACKGROUND: Although survival is traditionally modeled using Cox proportional hazards modeling, this approach may be inappropriate in sepsis, in which the proportional hazards assumption does not hold. Newer, more flexible models, such as Gray's model, may be more appropriate. OBJECTIVES: To construct and compare Gray's model and two different Cox models in a large sepsis cohort. To determine whether hazards for death after sepsis were nonproportional. To explore how well the different survival modeling approaches describe these data. DESIGN: Analysis of combined data from the treatment and placebo arms of a large, negative, sepsis trial. SETTING: Intensive care units at 136 U.S. medical centers. SUBJECTS: A total of 1090 adults aged 18 yrs or older with signs and symptoms of severe sepsis and documented or probable Gram-negative infection. MEASUREMENTS: We considered 27 potential baseline risk factors and modeled survival over the 28 days after the onset of sepsis. We tested proportionality in single-variable Cox analysis using Schoenfeld residuals and log-log plots. We constructed a traditional multivariable Cox model, a multivariable Cox model with time-varying covariates, and a multivariable Gray's model. RESULTS: In single-variable analyses, 20 of the 27 potential factors were significantly associated with mortality, and 10 of 20 had nonproportional hazards. In multivariate analysis, all three models retained a very similar set of significant covariates (two models retained the identical set of nine variables, and the third differed only in that it retained the same nine plus a tenth variable). Four of the nine common covariates had nonproportional hazards. Of the three models, Gray's model best captured these changing hazard ratios over time. CONCLUSION: We confirm that many of the important predictors of mortality in severe sepsis are nonproportional and find that Gray's model seems best suited for modeling survival in this condition.

Adult↗
PubMed2003

Pneumonia: still the old man's friend?

BACKGROUND: Hospital mortality of patients admitted with community-acquired pneumonia (CAP) has been well described. However, the long-term survival of those discharged alive is less clear. We sought to determine long-term survival of patients hospitalized with CAP and compare the outcome with controls hospitalized for reasons other than CAP. METHODS: We performed a matched case-control analysis using the Medicare hospital discharge database from the first quarter of 1997. We compared all Medicare recipients 65 years or older hospitalized with CAP and controls matched for age, sex, and race hospitalized for reasons other than CAP. We measured 1-year mortality determined from the Medicare Beneficiary Entitlement file and the Social Security Administration. RESULTS: We identified 158 960 CAP patients and 794 333 hospitalized controls. Hospital mortality rates for the CAP cohort and hospitalized controls were 11.0% and 5.5%, respectively (P<.001). One-year mortality rates for the CAP cohort and hospitalized controls were 40.9% and 29.1%, respectively (P<.001). One-year mortality rates in hospital survivors of the CAP and control cohorts were 33.6% and 24.9%, respectively (P<.001). The difference in mortality between the CAP and control cohorts was not explained by underlying disease. Standardized against the general population, the risk of death for both cohorts decreased monthly but was still elevated 1 year after hospital discharge. The standardized mortality ratio was 2.69 (95% confidence interval, 2.47-2.93) for CAP patients and 1.93 (95% confidence interval, 1.79-2.08) for hospital controls. CONCLUSIONS: Almost half of all elderly patients admitted for CAP die in the subsequent year, with most deaths occurring after hospital discharge. The mortality is considerably higher than that of either the general population or a control population hospitalized for reasons other than CAP.

Aged↗
PubMed2003

Community-acquired pneumonia in the elderly.

CAP is traditionally considered a medical disease, and is managed with intravenous fluids and antibiotics on medical floors. Recent cost-containment efforts have shifted the provision of care to the outpatient settings, and only those with most severe disease and multiple comorbid illnesses are admitted to hospitals. Therefore, the proportion of hospitalized patients with severe CAP that need intensive care and life support is increasing. Furthermore, the incidence of severe CAP is also rising due to disproportionate growth of the elderly population that is most vulnerable to this deadly disease. Many of these elderly patients have advanced underlying diseases, and CAP might often be a terminal event superimposed on an underlying chronic debilitating illness. As ICU physicians, we need to be familiar with this disease, its complications, and its prognosis to provide intensive care in a timely and rational fashion in some patients, and refrain from life support in others. Just as prior efforts have sought to improve and standardize criteria for hospital admission, future efforts should aim to improve and standardize decisions regarding intensive care and life support in these very sick elderly patients. Future efforts in the management of CAP need to consider the postdischarge period where most deaths occur. Prevention is an important issue especially for those at high risk for CAP.

Aged↗
PubMed2003

Noninvasive monitoring of cardiac output during exercise by inductance cardiography.

INTRODUCTION/PURPOSE: Inductance cardiography is a noninvasive technique that monitors changes in cardiac output from an inductance plethysmographic transducer encircling the chest at the level of the heart. The method has been previously validated in supine patients at rest by comparisons to thermodilution. Our purpose was to investigate whether the technique can be employed during bicycle exercise. METHODS: We simultaneously measured cardiac output by inductance cardiography and by two gas exchange methods based on the Fick principle during upright cycle ergometry in healthy volunteers. RESULTS: In 11 subjects, comparisons of changes in cardiac output by inductance cardiography agreed well with values measured by carbon dioxide rebreathing during a steady-state exercise protocol. In 12 subjects, cardiac output changes measured by inductance cardiography and an oxygen uptake method agreed closely during a progressive ramp exercise protocol to exhaustion. The bias (mean difference to reference methods) and limits of agreement (+/-2 SD of bias) for estimation of relative changes in cardiac output by inductance cardiography were 1% +/- 21% in 67 comparisons to the carbon dioxide rebreathing technique, and 0% +/- 22% in 98 comparisons to the oxygen uptake method. CONCLUSION: In healthy subjects, inductance cardiography accurately and unobtrusively estimates changes in cardiac output during bicycle exercise in comparison to gas exchange methods.

Adult↗
PubMed2002

Hospitalized community-acquired pneumonia in the elderly: age- and sex-related patterns of care and outcome in the United States.

Community-acquired pneumonia (CAP) is a frequent cause of hospital admission and death among elderly patients, but there is little information on age- and sex-specific incidence, patterns of care (intensive care unit admission and mechanical ventilation), resource use (length of stay and hospital costs), and outcome (mortality). We conducted an observational cohort study of all Medicare recipients, aged 65 years or older, hospitalized in nonfederal U.S. hospitals in 1997, who met ICD-9-CM-based criteria for CAP. We identified 623,718 hospital admissions for CAP (18.3 per 1,000 population > or = 65 years), of which 26,476 (4.3%) were from nursing homes and of which 66,045 (10.6%) died. The incidence rose five-fold and mortality doubled as age increased from 65-69 to older than 90 years. Men had a higher mortality, both unadjusted (odds ratio [OR]: 1.21 [95% CI: 1.19-1.23]) and adjusted for age, location before admission, underlying comorbidity, and microbiologic etiology (OR: 1.15 [95% CI: 1.13-1.17]). Mean hospital length of stay and costs per hospital admission were 7.6 days and $6,949. For those admitted to the intensive care unit (22.4%) and for those receiving mechanical ventilation (7.2%), mean length of stay and costs were 11.3 days and $14,294, and 15.7 days and $23,961, respectively. Overall hospital costs were $4.4 billion (6.3% of the expenditure in the elderly for acute hospital care), of which $2.1 billion was incurred by cases managed in intensive care units. We conclude that in the hospitalized elderly, CAP is a common and frequently fatal disease that often requires intensive care unit admission and mechanical ventilation and consumes considerable health care resources. The sex differences are of concern and require further investigation.

Age Distribution↗