Cardiac output measurement during exercise in COPD: A comparison of dye dilution and impedance cardiography.

INTRODUCTION: Impedance cardiography (IC) derived from morphological analysis of the thoracic impedance signal is now commonly used for noninvasive assessment of cardiac output (CO) at rest and during exercise. However, in Chronic Obstructive Pulmonary Disease (COPD), conflicting findings put its accuracy into question. OBJECTIVES: We therefore compared concurrent CO measurements captured by IC (PhysioFlow: COIC ) and by the indocyanine green dye dilution method (CODD ) in patients with COPD. METHODS: Fifty paired CO measurements were concurrently obtained using the two methods from 10 patients (FEV1 : 50.5 ± 17.5% predicted) at rest and during cycling at 25%, 50%, 75% and 100% peak work rate. RESULTS: From rest to peak exercise COIC and CODD were strongly correlated (r = 0.986, P < 0.001). The mean absolute and percentage differences between COIC and CODD were 1.08 L/min (limits of agreement (LoA): 0.05-2.11 L/min) and 18 ± 2%, respectively, with IC yielding systematically higher values. Bland-Altman analysis indicated that during exercise only 7 of the 50 paired measurements differed by more than 20%. When data were expressed as changes from rest, correlations and agreement between the two methods remained strong over the entire exercise range (r = 0.974, P < 0.001, with no significant difference: 0.19 L/min; LoA: -0.76 to 1.15 L/min). Oxygen uptake (VO2 ) and CODD were linearly related: r = 0.893 (P < 0.001), CODD = 5.94 × VO2 + 2.27 L/min. Similar results were obtained for VO2 and COIC (r = 0.885, P < 0.001, COIC = 6.00 × VO2 + 3.30 L/min). CONCLUSIONS: These findings suggest that IC provides an acceptable CO measurement from rest to peak cycling exercise in patients with COPD.

Quantitative evaluation of oligonucleotide surface concentrations using polymerization-based amplification.

Quantitative evaluation of minimal polynucleotide concentrations has become a critical analysis among a myriad of applications found in molecular diagnostic technology. Development of high-throughput, nonenzymatic assays that are sensitive, quantitative and yet feasible for point-of-care testing are thus beneficial for routine implementation. Here, we develop a nonenzymatic method for quantifying surface concentrations of labeled DNA targets by coupling regulated amounts of polymer growth to complementary biomolecular binding on array-based biochips. Polymer film thickness measurements in the 20-220 nm range vary logarithmically with labeled DNA surface concentrations over two orders of magnitude with a lower limit of quantitation at 60 molecules/microm(2) (approximately 10(6) target molecules). In an effort to develop this amplification method towards compatibility with fluorescence-based methods of characterization, incorporation of fluorescent nanoparticles into the polymer films is also evaluated. The resulting gains in fluorescent signal enable quantification using detection instrumentation amenable to point-of-care settings.

Calibration of densitometers for indicator dye dilution.

A systematic investigation was undertaken to determine which factors affect the calibration of a Gilford monochromatic densitometer used for recording indicator-dilution curves with indocyanine green. Calibration was not influenced by variation of withdrawal speeds from 6.4 to 20.6 cm3/min but varied with differing sampling systems. Variation in haemoglobin from 10 to 17.5 g-dl-1 or in haematocrit from 30 to 60% did not affect calibration. Calibration lines showed both curvature and hysteresis. The opitcal properties of indocyanine green were not affected by storage of diluted dye in the dark for 24 hours but were altered by the presence of contrast media used in angiography. No systematic error resulted from the substitution of stored ACD blood for patient's blood in calibration although random error was increased. Recommendations based on these findings are made for a simple calibration technique which avoids systematic error.

A computerised dichromatic earpiece densitometer for the measurement of cardiac output.

This study assesses a precalibrated dichromatic earpiece densitometer and microprocessor for the measurement of cardiac output by indocyanine green dye dilution. The measured cardiac output is compared with values of cardiac output simultaneously determined using a cuvette densitometer. The microprocessor computation of cardiac output agreed very closely with the cardiac output determined by manual calculation from the same dye dilution curves (standard deviation +/- 1.47%). The reproducibility of the earpiece densitometer (standard deviation +/- 5.2%) was virtually identical to that of the cuvette densitometer (+/- 5.3%). In a comparison of earpiece and cuvette densitometers for 60 measurements of cardiac output following pulmonary arterial injection of dye and for 50 measurements following femoral venous injection of dye, correlation coefficients were 0.83 and 0.78 and the standard deviations of the differences of simultaneous measurements were 7.2% and 8.3% respectively. The instrument offers an accurate reproducible and relatively noninvasive technique for measuring cardiac output.

Cardiac output measured by lithium dilution and transpulmonary thermodilution in patients in a paediatric intensive care unit.

OBJECTIVE: To compare the results of cardiac output measurements obtained by lithium dilution and transpulmonary thermodilution in paediatric patients. DESIGN: A prospective study. SETTING: Paediatric intensive care unit in a university teaching hospital. PATIENTS: Twenty patients (age 5 days-9 years; weight 2.6-28.2 kg) were studied. INTERVENTIONS: Between two and four comparisons of lithium dilution cardiac output (LiDCO) and transpulmonary thermodilution (TPCO) were made in each patient. MEASUREMENTS AND RESULTS: Results from three patients were excluded: in one patient there was an unsuspected right-to-left shunt, in two patients there was a problem with blood sampling through the lithium sensor. There were 48 comparisons of LiDCO and TPCO in the remaining 17 patients over a range of 0.4-6 l/min. The mean of the differences (LiDCO-TPCO) was -0.1 +/- 0.3 (SD) l/min. Linear regression analysis gave LiDCO = 0.11 + 0.90 x TPCO l/min (r2 = 0.96). There were no adverse effects in any patient. CONCLUSIONS: These results suggest that the LiDCO method can be used to provide safe and accurate measurement of cardiac output in paediatric patients. The method is simple and quick to perform, requiring only arterial and venous catheters, which will already have been inserted for other reasons in these patients.

Effects of the stable prostacyclin analogue iloprost on the plasma disappearance rate of indocyanine green in human septic shock.

OBJECTIVES: To evaluate the effect of the stable prostacyclin analogue iloprost on the plasma disappearance rate of indocyanine green (PDR) in patients with septic shock. DESIGN AND SETTING: A prospective clinical study in a university hospital intensive care unit. PATIENTS AND INTERVENTIONS: 20 patients in septic shock. Patients received iloprost infusion (1 ng/kg per minute) for 24 h. MEASUREMENTS AND RESULTS: PDR was determined by a femoral arterial fiberoptic catheter before, 1, 6, and 24 h after start and 1 h after end of iloprost infusion. PDR increased significantly 24 h after start of iloprost infusion (baseline: 13.9 +/- 1.7% vs. 18.6 +/- 2.2%/min) and decreased 1 h after end of infusion (13.7 +/- 1.7%/min; p < 0.002). There was no change in pHi, cardiac index, mean arterial pressure, heart rate, central venous pressure, or intrathoracic blood volume index. CONCLUSION: Administration of the stable prostacyclin analogue iloprost significantly increases PDR, indicating improvement in liver function.

Comparison of invasive and noninvasive measurements of indocyanine green plasma disappearance rate in critically ill patients with mechanical ventilation and stable hemodynamics.

OBJECTIVES: We studied the correlation between invasive (aortic fiberoptic) and noninvasive (transcutaneous sensor) measurements of indocyanine green (ICG) plasma disappearance rate (PDR) in critically ill patients. DESIGN AND SETTING: Prospective clinical study in a surgical intensive care unit of a university hospital. PATIENTS: 16 critically ill patients with adult respiratory distress syndrome (n = 8), sepsis/septic shock (n = 6), subarachnoid hemorrhage (n = 1), or severe head injury (n = 1). MEASUREMENTS AND RESULTS: We analyzed 16 pairs of simultaneous ICG PDR measurements. All patients were deeply sedated and mechanically ventilated. Each patient received a 4-F aortic catheter with an integrated fiberoptic and thermistor connected to a computer system for automatic calculation of invasive ICG PDR (PDRINV). An ICG sensor was also attached to the nose wing and connected to a DDG2001 analyzer for noninvasive measurement (PDRNINV). Linear regression analysis revealed PDRNINV = 0.98 PDRINV +0.11%/min (r = 0.94, p < 0.0001) with a mean bias of 0.2 +/- 2.0%/min. CONCLUSION: Noninvasive measurements of ICG PDR are very highly correlated with values derived from an invasive fiberoptic-based reference technique.

Video dilution technique. An accurate measure of blood flow during routine arteriography.

The video dilution technique for measuring blood flow consists of electronically and mathematically processing video-taped selective arteriograms to measure the flow in selectively catheterized arteries and to express this flow as a fraction of the flow in any reference artery. Flows were measured by video dilution and an electromagnetic flowmeter in ten dogs; the correlations were excellent. Video dilution flows were also measured in 105 patients. The technique is accurate, simple, and adds no risk to routine selective arteriography.

[Device for measuring microconcentrations of indicator dyes in the blood]. / Pribor dlia izmereniia mikrokontsentratsii krasitelei-indikatorov v krovi.

A device operating on the principle of spectrophotometry that allows it by using an auricular sensor to continually record changes in the microconcentration (up to 1 mg/1) of dyes-indicators (ueviridin, cardiogrin, indigocarmin) that are introduced in the human blood circulation system for the purpose of diagnosing affections of the liver, kidneys and heart, is described.