[Fiber optic sensor technology in the endotracheal tube]. / Faseroptische Sensorik im Endotrachealtubus.

The measurement of individual respiratory parameters in the vicinity of the lungs remains an unresolved problem in the areas of anesthesia and intensive care medicine. New technologies such as fibreoptic technology, which meet the extreme demands of medical sensor applications, and their innovative potential as a basis for the development of marketable products, appear promising. This is illustrated by the fundamental principles developed for a sensor-armed tracheal tube for on-line monitoring of ventilated patients.

New echocardiographic and angiographic methods for right atrial volume determination: in vitro validation and in vivo results.

Until now, right atrial (RA) volume calculation by means of two-dimensional echocardiography (2-DE) has only been attempted in a single plane: the apical four-chamber view. Our study reports a new method for RA volume calculation using two intersecting 2-DE views. For this purpose, silicone rubber casts of 19 human necropsy hearts were obtained and thin-walled natural rubber moulds of the RA casts were prepared. Totally filled with and immersed in water, the moulds could be visualized in the apical four-chamber view and an additional 2-DE plane, the latter corresponding to the subcostal view in vivo. In this view the vertical extension of RA could be estimated. Areas and lengths of RA were determined in the respective planes, and RA volume was calculated by applying the formula, area x length, to two intersecting planes. Finally, volume of the silicone casts was determined angiocardiographically (Angio) using a biplane method (30 degrees RAO, 40 degrees LAO-40 degrees hepatoclavicular). The true RA volume was 106 +/- 23 ml (mean +/- 1 SD) as determined by water displacement. Using Angio an excellent correlation was found: the calculated volume amounted to 106 +/- 23 ml; the difference was 5.5 +/- 4.8 ml (n.s.); Angio vol = 0.93 true vol + 7.77; r = 0.95; SEE = 7.4 ml. Volume determination from the apical four-chamber view of 2-DE using a monoplane disk method resulted in a mean volume of 62 +/- 17 ml. The mean difference to the true RA volume was 44 +/- 16 ml (p less than 0.001). When volume calculations were made using the biplane method, a value of 105 +/- 22 ml resulted. The mean difference to true volumes was 7.4 +/- 4.8 ml: y = 0.84x + 15.88; r = 0.91; SEE = 9.4 ml. In an in vivo study endsystolic RA volumes were calculated in a normal adult population (n = 40) from the same intersecting planes as in vitro. A normal value of 38 +/- 6 ml/m2 was found. In vivo validation using Angio showed a slightly higher normal value of 43 = 7 ml/m2. Thus, 2-DE is highly accurate in determining RA volume. In the in vitro as well as in the in vivo study the results of monoplane calculations are clearly inferior to a method which also takes account of the vertical extension of RA.

Hydrodynamic investigation of mechanical bileaflet valves.

For hydrodynamic comparison, 11 mechanical bileaflet valves have been perfused in a mock circulation system under pulsatile flow conditions. Six St. Jude Medical valves with different sizes from No. 21 to No. 31 and five Duromedics prostheses with corresponding sizes from No. 21 to No. 29 have been investigated. Flow, pressure, and orifice area were measured, while cardiac output was varied between 2 and 6 L/min. Insufficiency (I), maximal orifice area (Amax), mean orifice area (A), discharge coefficient (CD), performance index (PI), and efficiency index (EI) were determined. The St. Jude Medical valves show higher values of orifice area when compared with the Duromedics valves. For smaller valve sizes up to No. 25, the values of the orifice area are similar. The Duromedics valves show much lower values of insufficiency; thus, for small valve sizes, the Duromedics prosthesis seems to be superior. For larger valve sizes (No. 27, No. 29, and No. 31), a decision has to be made whether higher insufficiency and higher orifice area of the St. Jude Medical valve or lower insufficiency with lower orifice area is more acceptable.

[Comparative study of mechanical heart valves for implantation in mitral position]. / Vergleichende Untersuchung mechanischer Herzklappen zur Implantation in Mitralposition.

For hydrodynamic comparison of mechanical heart valves, three tilting disc valves (Björk-Shiley SD, Björk-Shiley CCD, Björk-Shiley Monostrut) and two bileaflet valves (St. Jude Medical, Duromedics) with annulus diameter dA = 31 mm were perfused in a mock circulation in mitral position. Flow, pressure, and orifice area were measured during pulsatile flow. Insufficiency, maximal orifice area, mean orifice area, performance index and efficiency index were calculated. The tilting disc valves show distinctly lower orifice areas than the bileaflet valves. The mean value of maximal orifice area Amax of the Björk-Shiley prostheses varies between 227.82 +/- 7.77 mm2 and 243.21 +/- 6.21 mm2. The mean value of Amax of the Duromedics prosthesis is 295.45 +/- 7.76 mm2 and that of the St. Jude Medical prosthesis is 477.43 +/- 11.32 mm2. The calculated mean orifice areas A of the bileaflet valves are also higher than those of the tilting disc valves. The mean values of A are: Björk-Shiley SD: 183.55 +/- 10.03 mm2; Björk-Shiley CCD: 206.30 +/- 8.62 mm2; Björk-Shiley Monostrut: 210.12 +/- 4.74 mm2; St. Jude Medical: 398.69 +/- 19.55 mm2; Duromedics: 262.90 +/- 6.84 mm2. The performance index PI is qualitatively identical with the values of the mean orifice area A because in this study only heart valves of the same size were investigated. For calculation of insufficiency I the entire reflux volume VR including closing volume VS and leakage volume VL was used, thus, insufficiency was also determined in intact prostheses. The values of insufficiency of the mechanical valves investigated are higher for the bileaflet valves than for the tilting disc valves.(ABSTRACT TRUNCATED AT 250 WORDS)

Results of a comparative in vitro study of Duromedics and Björk-Shiley monostrut mitral heart valve prostheses.

Two different mechanical heart valves with annulus diameters 21-29 mm, (five Björk-Shiley monostrut tilting disc valves and five Duromedics bileaflet valves) have been tested in pulsatile flow in the mitral position of a mock circulation. Reflux, pressure, and orifice area have been measured while cardiac output was varied between 2 and 6 1 min-1. Insufficiency, mean orifice area, discharge coefficient, and performance and efficiency indices have been calculated. Mean values of insufficiency for the Björk-Shiley monostrut valves varied between 4.8 and 17.2% while the corresponding values for the Duromedics valves were in the range 6.1-17.3%. Mean values for orifice areas of the Björk-Shiley monostrut valves increased with the larger valve sizes from 101.1 to 210.2 mm2; for the Duromedics valves the area range was 134.5-262.9 mm2. Because of the larger orifice areas the values of discharge coefficient and performance index for the Duromedic valves were higher than those for the Björk-Shiley monostrut valves. As the insufficiency of the two mechanical valves was similar, and the orifice area of the bileaflet valves was greater than that of the tilting disc valves, Duromedics valves gave higher valves for the efficiency index, which varied between 0.31 and 0.39; for Björk-Shiley monostrut valves the index varied between 0.24 and 0.28 under the same test conditions. This hydrodynamic in vitro comparison of mechanical heart valves showed that the Duromedics bileaflet valves were superior to the Björk-Shiley tilting disc valves.

[A new echocardiographic procedure for calculation of the accurate volume of the right atrium]. / Ein neues echokardiographisches Verfahren zur exakten Volumenberechnung des rechten Vorhofes.

The right atrial (RA) volume can be determined angiographically from two perpendicular projections. Up to now volume calculations by means of two-dimensional echocardiography (2-DE) have only been attempted in a single plane, the apical four-chamber view. Our study reports a new method for RA volume calculation using two intersecting cross-sectional echocardiographic views. For this purpose silicone rubber casts of 20 human necropsy hearts were obtained and thin walled natural rubber moulds of the RA casts were prepared. Totally filled with and immersed in water, the mouls could be visualized in the apical four-chamber view and an additional echocardiographic plane, the latter corresponding to the subcostal view in vivo. In this view the vertical extension of RA could be estimated. Areas and length of RA were determined in the respective planes and RA volume was calculated by applying the formula: - Area X Length - to two intersecting planes. Finally, the latex moulds were filled with diluted contrast agent and the volume was determined angiographically using a biplane disc method. Real volume of RA was 112 +/- 23 ml (mean +/- 1 SD). Angiographically, an overestimation resulted: the calculated volume amounted to 119 +/- 24 ml, the mean difference was 7 +/- 2 ml (p less than 0.001). The regression equation was y = 1.04 X + 2.34, r = 0.995, SEE = 2.3 ml. Volume determination from the apical four-chamber view using a monoplane disc method resulted in a mean volume of 62 +/- 17 ml. The mean difference to the real RA volume was 50 +/- 17 ml, p less than 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrodynamic test of bioprostheses in the mitral position.

With the described circulation simulator it is possible to simulate physiological values of pulse frequency, filling volume and pressure. Bioprostheses with pathological changes can be investigated in vitro under normal and under specific pathological in vivo circulation conditions. The criteria of classification of the effectiveness of bioprostheses are reflux volume, VR, insufficiency, I and maximal orifice area, A. As a result of the definition of insufficiency, even intact bioprostheses show insufficiency with regard to the closing volume. While the effectiveness of perforated bioprostheses can be clearly demonstrated by reflux volume and insufficiency, the regurgitation of a stenosed valve gives no meaningful statement as to its effectiveness. In this case, the orifice area, A, is a suitable criterion of the classification of effectiveness.