Biomedical subjects

M L Landsman

Publications and source records attributed to M L Landsman.

4 recordsLinked to original sources

PubMed1992

Comparison between New York Heart Association classification and peak oxygen consumption in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure secondary to either ischemic or idiopathic dilated cardiomyopathy.

To compare the value of the New York Heart Association (NYHA) classification and measurement of peak oxygen consumption (VO2) in the assessment of functional status and prognosis in patients with mild to moderate chronic congestive heart failure (CHF), 94 patients with clinically stable NYHA class II and III CHF were prospectively studied. In all patients, left ventricular ejection fraction was less than or equal to 40% (mean 22 +/- 9); 49 patients were in NYHA class II, and 45 were in NYHA class III. Mean peak VO2 was 17 +/- 5 ml/min/kg. During a follow-up period of 23 +/- 11 months, 21 patients died. The 1-, 2- and 3-year cumulative survival rates for the 94 patients were 88, 79 and 69%, respectively. Functional status, as assessed both by peak VO2 and NYHA classification, and left ventricular ejection fraction were significantly worse in the group of nonsurvivors. The most powerful independent predictor of mortality was peak VO2. Although mean peak VO2 was significantly higher in NYHA class II than in NYHA class III (20 +/- 4 vs 13 +/- 3 ml/min/kg, p less than 0.0001), categorization into subgroups on the basis of the attained peak VO2 revealed a marked discrepancy with the NYHA classification. Nevertheless, the survival curves of patients subdivided at a peak VO2 of 16 ml/min/kg showed a strong resemblance with survival curves of both NYHA classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1979

A fiberoptic reflection densitometer with cardiac output calculator.

A catheter-tip densitometer for indocyanine green is described consisting of a cardiac catheter containing optical fibers, an incandescent light source, a light detection unit and a processing unit. Half of the optical fibers guide the light to the blood at the tip of the catheter, the other half the back-scattered (reflected) light to the detection unit. In the detection unit the light is measured by two silicium barrier layer photocells after it has been split into two beams by a beam splitter. In the measuring channel the light passes an 800 nm filter before reaching the photocell. When fiberoptic catheters with glass fibers are employed, the other channel, used for compensation of non-specific effects such as blood flow variations, contains no filter, thus measuring light in a broad spectral band. It is shown that in this way compensation of flow effects may be about two times better than when a 920 nm filter is used. When using plastic optical fibers a 950 nm filter must be used, because above lambda = 850 nm plastic fibers transmit only a band around that wavelength (950 nm). At zero dye concentration the densitometer output or ratio of compensating and measuring photocell output R/R800 is almost insensitive to changes in haemoglobin concentration. When the blood contains dye, however, the influence of haemoglobin concentration is considerable. The densitometer output R/R800 is linearly related to dye concentration up to 50 mg . 1-1, the output R920/R800 up to 30 mg . 1(-1). The output R/R800 decreases with decreasing oxygen saturation; the slope of the calibration line, however, appears to be unaffected. The processing unit also contains an analog cardiac output calculator consisting of an integrator and a divider. Central dye dilution curves recorded from the pulmonary artery after injection of dye into the right atrium or a caval vein come down to the baseline. At this moment the reading of a digital voltmeter displaying the divider output calibrated in 1 . min-1 can be held and the reading taken.

Animals↗

PubMed1978

A fiberoptic reflection oximeter.

A catheter tip oximeter is described consisting of a cardiac catheter containing optical fibers, and incandescent light source, a light detection unit and a processing unit. Half of the optical fibers guide the light to the blood at the tip of the catheter, the other half the backscattered (reflected) light to the detection unit. The detection unit contains a dichroic mirror, transmitting most of the light with lambda less than 800 nm and reflecting most of the light with lambda greater than 900 nm, thus splitting the light into two beams. These pass through interference filters with nominal wavelengths of 640 and 920 nm respectively, and are focused on silicium barrier layer photocells. The photocell signals are amplified and fed into a divider giving the ratio of measuring (R640) and compensating (R920) photocell output. The relationship between log R640/R920 and oxygen saturation is represented by a slightly curved line. The relation may be linearized by subtracting a constant voltage from the divided output before taking the logarithm. The slope of the calibration line is dependent on the total haemoglobin concentration. Nonetheless an average calibration line can be used between 70 and 100% oxygen saturation. For 78 measurements of pig blood samples in this range (haemoglobin concentration between 96 and 161 g.1(-1)), the standard deviation of the difference between the fiberoptic oximeter and a Radiometer OSM1 oxygen saturation meter was 1.9% saturation, for 152 samples over the entire saturation range the standard deviation of the difference was 3.1% saturation. The influence of the flow velocity of blood on the light reflection depends on wavelength as well as on oxygen saturation. Therefore, complete compensation for the flow effect is not possible by simple means.

Animals↗

PubMed1976

Light-absorbing properties, stability, and spectral stabilization of indocyanine green.

The absorption spectrum of indocyanine green depends on the nature of the solvent medium and on the dye concentration. Binding to plasma proteins causes the principal peaks in the absorption spectrum to shift about 25 nm toward the higher wavelengths. The much greater influence on the spectrum of the dye concentration results from progressive aggregate formation with increasing concentration. Indocyanine green solutions therefore do not follow Lambert-Beer's law above 15 mg-I-1 (in plasma). Indocyanine green solutions in plasma and concentrated (1,000 mg-I-1) solutions in distilled water are stable for at least 4 h. In long-term experiments the optical density of indocyanine green solutions in plasma as well as in distilled water generally diminishes, even in the dark. On the 7th day a new absorption maximum starts to appear at gamma=900 nm, possibly caused by further aggregate formation leading to much larger particles. Spectral stabilization after injection of a concentrated solution into the blood is most rapid when the dye is dissolved in distilled water. Spectral stabilization slows down with decreasing temperature. As rapid spectral stabilization is essential in quantitative dye dilution studies, the practice of adding a albumin and/or isotonic saline solution to the injectate should be discontinued. When a 10 g-1(-1) aqueous solution of indocyanine green is used, spectral stabilization takes less than 1.5 a (at 37 degrees C), which is sufficiently fast for almost any application.

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