Biomedical subjects

K Forstner

Publications and source records attributed to K Forstner.

15 recordsLinked to original sources

PubMed1993

[Pulse oximetry in the air rescue service. 1: Quantitative detection of interfering factors on the method].

The introduction of pulse oximetric monitoring in prehospital emergency medicine considerably contributed to emergency patients' safety, stability and protection. As inherent in any method of measurement, certain factors can interfere with it and limit its practical application. The emergency helicopter service at Ulm, in a prospective study involving 400 patients, systematically collected data on these limiting factors and evaluated them. The index "S" was established to quantify the time lost due to malfunctioning. Within the study group, the index average was S = 0.269, that is 26.9% of measurement time was subject to interference. The major cause was motion artifacts (68%) sensor probe dislocation (15%), low perfusion (14%) and radiation (3%). Regarding the volume of time lost due to specific interfering factors, motion artifacts (61.8%) and low perfusion (25.5%) were dominant, followed by sensor probe dislocation (10.3%) and radiation (2.4%). Interference therefore, both in time and frequency was primarily due to motion artifacts and low perfusion. The conclusions from this study led to the evaluation of two methods by which the interfering factors could be reduced: 1. ECG-synchronisation of the pulse oximetric signal; 2. The use of adhesive sensors.--The degree of increase in pulse oximetric measurement stability achieved by these two methods will be investigated in part 2 of this study.

Aircraft↗

PubMed1993

[Pulse oximetry in the air rescue service. 2: Methods of increasing the stability of pulse oximetry measurements--ECG-synchronized pulse oximetry and adhesive sensors].

Pulse oximetric monitoring in air rescue service (rescue helicopter) is primarily influenced by motion artifacts (especially those of a passive nature), by low perfusion and by the problem of probe dislocation. In a prospective study involving 162 unselected emergency patients treated by the medical team of the emergency helicopter service "Christoph 22" (Ulm), we studied the possibility of reducing these adverse factors by applying available state-of-the-art technology, such as ECG-synchronization and adhesive probes. By applying the thus modified methods of monitoring, the interference factor was reduced to S = 0.056, that is only 5.6% of measurement time was adversely effected. The increase in measurement stability resulted from the reduction in number of described artifacts (motion artifacts and low perfusion), as well as from the reduction in duration of interfered measurement time. ECG-synchronization very effectively influenced the passive motion artifacts. Their frequency was reduced by the factor 8.2, respectively 42. An effective reduction in number of probe dislocations can be achieved by applying adhesive probes. The high costs of such probes presently limits their application. Radiation can be eliminated by redesigning the probe. ECG-synchronization of pulse oximetric signal has proved to be a method to reduce the artifacts frequently experienced in air rescue and has considerably contributed to the increase of emergency patient safety.

Aircraft↗

PubMed1992

[The elimination of carboxyhemoglobin--gender-specific and circadian effects].

We investigated sex-specific and circadian variations of carboxyhemoglobin (COHb) elimination in healthy volunteers. COHb elimination follows an exponential function with a baseline found in nonsmoking women at 1.72% and in nonsmoking men at 1.79% COHb saturation. During the day, the elimination half-life time (t1/2), determined by eleven hourly samples after stopping smoking was significantly (Wilcoxon-test, p less than .01) shorter in women (3.2 +/- .4 hours, mean +/- standard deviation, n = 7) than in men (4.5 +/- 0.4, n = 6). During the night, too, t1/2 calculated from 2-point measurements after the smoking halt was significantly (Wilcoxon-test, p less than .05) shorter in women (4.3 +/- 1.1, n = 4) than in men (8.0 +/- 1.6, n = 5). In men, t1/2 during the night was significantly longer (p less than .01, Wilcoxon-test) than during the day. The day/night difference may be caused by reduced alveolar ventilation during sleep. Less muscle mass and, therefore, less myoglobin as a depot for carbon monoxide may account for the shorter half-life time of carboxyhemoglobin in women. We conclude that these variations of COHb-elimination should be taken into account when a smoking halt is advised, for instance, preoperatively.

Carboxyhemoglobin↗

PubMed1991

[Carboxyhemoglobin in smokers and a preoperative smoking cessation].

The proportion of carbon monoxide-haemoglobin (COHb) in blood was determined before elective surgery on 50 patients (12 women and 38 men; mean age 39.5 [21-68] years) who were smoking at least 20 cigarettes a day, at two moments: during ad lib smoking and after a smoking halt of more than nine hours. 50 nonsmokers (25 women and 25 men; mean age 29.5 [20-48] years) served as controls. COHb proportion before smoking halt averaged 6.9 +/- 1.8%, after halt it averaged 3.8 +/- 1.1% (P less than 0.001). Individual values over 6% were found even after abstinence. COHb proportion in nonsmokers was 1.8 +/- 0.2% (nonsmokers vs. smokers: P less than 0.001 with and P less than 0.01 without smoking halt). The results show that measures to improve oxygen transport capacity, such as blood transfusion or oxygen breathing, are indicated early, especially in an emergency, in smokers and those with uncertain smoking habits. Smoking halt of at least nine hours should be recommended to all heavy smokers before elective surgery.

Adult↗

PubMed1991

[Carbomonoxyhemoglobin and methemoglobin in patients with and without a smoking history during ambulatory anesthesia. Consequences for the use of pulse oximetry].

Carboxyhemoglobin (COHb) and methemoglobin (MetHb) in venous blood were determined by oximetry in 1000 non-hospitalised preoperative patients. 370 of them were smokers (S), 630 non-smokers (NS). In addition, in five S we compared the oxygen saturation measured by pulse oximetry (SaO2, p) with that measured by in vitro oximetry (SaO2) and that calculated with reference to COHb (SaO2,korr). MetHb (0.66 +/- 0.21%, mean +/- standard deviation) was found to be of no relevance. COHb in S (5.12 +/- 2.25%, maximum 12.4%) was significantly higher than in NS (1.82 +/- 0.3%, range 0.9%-4.0%) and is therefore of importance in S for the oxygen transport and for the interpretation of SaO2, p, which overestimated SaO2 at a COHb level of 4.4 +/- 0.7% by 4.5 +/- 0.9%. The difference between SaO2, korr (calculated according to Forstner) differed from SaO2 by 0.66 +/- 0.5% only. We conclude that there is an indication for in vitro oximetry in non hospitalised smokers or cases of unknown smoking history. If oximetry is not available, both a reduction of O2-binding hemoglobin and an overestimation of SaO2 by pulse oximetry in an order of ten per cent should be taken into account. To compensate for dyshemoglobin fractions, pulse oximetry using more than two wavelengths is desirable.

Ambulatory Care↗

PubMed1991

[Respiratory disorders in trauma patients. Pulse oximetry as an extension of prehospital diagnostic and therapeutic possibilities].

The early diagnosis and adequate treatment of respiratory complications in trauma cases has a decisive influence upon the patients' posttraumatic development. Pulse oximetry enables us to evaluate and monitor the prehospital respiratory situation objectively for the first time. Within a prospective study conducted from October 1988 to October 1989 in 336 unselected, primarily traumatized, emergency patients rescued by our "SAR Ulm 75" helicopter team, to determine the possibilities and limitations of this method, we maintained continuous pulse oximetric monitoring in all cases. The practical applicability and functional stability of the pulse oximeters used were adequate. On-the-spot intubation was necessary in 45% of the patients (or they were intubated prior to our taking over). Oxygen inhalation by nasal cannula was needed in 55%. While not being decisive for immediate intubation, monitoring with a pulse oximeter does play an essential role in controlling respiratory therapy. In 32% of our cases, pulse oximetric monitoring permitted early adjustment of the respiratory therapy to meet the patients requirements. This method is of special value in disclosing life-threatening respiratory complications (9.3%) i.e., valve pneumothorax. Within a group with a high percentage of multiple traumas (27%) and thorax traumas (39%), this was of enormous assistance in the differential diagnosis. Level and rate of increase of oxygen saturation can be an indication of the severity of a thorax trauma. The limitations of pulse oximetric monitoring, especially those resulting from low peripheral perfusion in trauma cases (7 patients), are fairly rare.

Adult↗

PubMed1990