20 Jan 10
Posted in Mechanical ventilation at 0:52 by Laci
By D Frankenfield, S Alam, E Bekteshi, R Vender
Crit Care Med 2010;38:288-291
To develop and validate an equation to predict dead space to tidal volume ratio (Vd/Vt) from clinically available data in critically ill mechanically ventilated patients.
Design
Prospective, observational study using a convenience sample of patients whose arterial blood gas and respiratory gas exchange had been measured with indirect calorimetry.
Setting
Medical and surgical critical care units of a university medical center.
Patients
Adult, mechanically ventilated patients at rest with Fio2 ≤0.60 and no air leaks who had recent arterial blood gas recordings and end-tidal carbon dioxide concentration monitoring.
Intervention
Observational only.
Measurements and main results
Indirect calorimetry was used to determine carbon dioxide production and expired minute ventilation in 135 patients. Tidal volume and respiratory rate were recorded from the ventilator. End tidal carbon dioxide concentration, body temperature, arterial carbon dioxide partial pressure (Paco2), and other clinical data were recorded. Vd/Vt was calculated using the Enghoff modification of the Bohr equation (Paco2 − PECO2/Paco2). Regression analysis was then used to construct a predictive equation for Vd/Vt using the clinical data: Vd/Vt = 0.32 + 0.0106 (Paco2 − ETCO2) + 0.003 (RR) + 0.0015 (age) (R2 = 0.67). A second group of 50 patients was measured using the same protocol and their data were used to validate the equations developed from the original 135 patients. The equation was found to be unbiased and precise.
Conclusions
Vd/Vt is predictable from clinically available data. Whether this predicted quantity is valuable clinically must still be determined.
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15 Jan 10
Posted in ECMO, Mechanical ventilation at 1:40 by Laci
By T Muller, A Philipp, A Luchner, C Karagiannidis, T Bein, M Hilker, L Rupprecht, J Langgartner, M Zimmermann et al
Critical Care 2009, 13:R205
Mortality of severe acute respiratory distress syndrome in adults is still unacceptably high. Extracorporeal membrane oxygenation (ECMO) could represent an important treatment option, if complications were reduced by new technical developments.
Methods
Efficiency, side effects and outcome of treatment with a new miniaturized device for veno-venous extracorporeal gas transfer were analysed in 60 consecutive patients with life-threatening respiratory failure.
Results
A rapid increase of PaO2/FiO2 from 64 (48-86) mmHg to 120 (84-171) mmHg and a decrease of PaCO2 from 63 (50-80) mmHg to 33 (29-39) mmHg were observed after start of the extracorporeal support (p<0.001). Gas exchange capacity of the device averaged 155 (116-182) mL/min for oxygen and 210 (164-251) mL/min for carbon dioxide. Ventilatory parameters were reduced to a highly protective mode, allowing a fast reduction of tidal volume from 495 (401-570) mL to 336 (292-404) mL (p < 0.001) and of peak inspiratory pressure from 36 (32-40) cmH2O to 31 (28-35) cmH2O (p < 0.001). Transfusion requirements averaged 0.8 (0.4-1.8) units of red blood cells per day. 62% of patients were weaned from the extracorporeal system, and 45% survived to discharge.
Conclusions
Veno-venous extracorporeal membrane oxygenation with a new miniaturized device supports gas transfer effectively, allows for highly protective ventilation and is very reliable. Modern ECMO technology extends treatment opportunities in severe lung failure.
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13 Nov 09
Posted in Mechanical ventilation at 2:27 by Laci
By C Teixeira, N da Silva, A Savi, S Rios Vieira, L Nasi, G Friedman et al
Crit Care Med – published ahead of print
To evaluate the predictive value of central venous saturation to detect extubation failure in difficult-to-wean patients.
Design
Cohort, multicentric, clinical study.
Setting
Three medical-surgical intensive care units.
Patients
All difficult-to-wean patients (defined as failure to tolerate the first 2-hr T-tube trial), mechanically ventilated for >48 hrs, were extubated after undergoing a two-step weaning protocol (measurements of predictors followed by a T-tube trial). Extubation failure was defined as the need of reintubation within 48 hrs.
Interventions
The weaning protocol evaluated hemodynamic and ventilation parameters, and arterial and venous gases during mechanical ventilation (immediately before T-tube trial), and at the 30th min of spontaneous breathing trial.
Measurements and main results
Seventy-three patients were enrolled in the study over a 6-mo period. Reintubation rate was 42.5%. Analysis by logistic regression revealed that central venous saturation was the only variable able to discriminate outcome of extubation. Reduction of central venous saturation by >4.5% was an independent predictor of reintubation, with odds ratio of 49.4 (95% confidence interval = 12.1-201.5), a sensitivity of 88%, and a specificity of 95%. Reduction of central venous saturation during spontaneous breathing trial was associated with extubation failure and could reflect the increase of respiratory muscles oxygen consumption.
Conclusions
Central venous saturation was an early and independent predictor of extubation failure and may be a valuable accurate parameter to be included in weaning protocols of difficult-to-wean patients.
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08 Nov 09
Posted in COPD, Mechanical ventilation at 19:43 by Laci
By M Wildman, C Sanderson, J Groves, B Reeves, J Ayres, D Harrison, D Young and K Rowan
QJM 2009 102(6):389-399 http://qjmed.oxfordjournals.org/cgi/content/full/102/6/389
Decisions about the intensity of treatment for patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) are influenced by predictions about survival and quality of life. Evidence suggests that these predictions are poorly calibrated and tend to be pessimistic.
Aim
The aim of this study was to develop an outcome prediction model for COPD patients to support treatment decisions.
Methods
A prospective multi-centre cohort study in Intensive Care Units (ICU) and Respiratory High Dependency Units (RHDU) in the UK recruited patients aged 45 years and older admitted with an exacerbation of obstructive lung disease. Data were collected on patientsí characteristics prior to ICU admission, and on their survival and quality of life after 180 days. An outcome prediction model was developed using multivariate logistic regression and bootstrapping.
Results
Ninety-two ICUs (53% of those in the UK) and three RHDUs took part. A total of 832 patients were recruited. Cumulative 180-day mortality was 37.9%. Using data available at the time of admission to the units, a prognostic model was developed which had an estimated area under the receiver operating characteristic curve (ëcí) of 74.7% after bootstrapping that was more discriminating than the clinicians (P = 0.033) and was well calibrated.
Discussion
This study has produced an outcome prediction model with slightly better discrimination and much better calibration than the participating clinicians. It has the potential to support risk adjustment and clinical decision making about admission to intensive care.
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