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Biomedical subjects

O Löfgren

Publications and source records attributed to O Löfgren.

10 recordsLinked to original sources
PubMed1979

Transcutaneous oxygen measurement in adult intensive care.

Transcutaneous oxygen measurement (PtcO2-measurement) gives by a non-invasive technique continuous information about central PO2. The method has as yet been tested mainly on newborns, and systematic studies of the applicability of the method on adults are still few. The current systematic study reports on consecutive PtcO2 measurements in 15 patients, all with indwelling arterial catheters: 13 of the patients were artificially ventilated; 5 patients had normal body structure and normal skin circulation; 5 patients were obese and had normal skin circulation; and 5 patients were hypothermic with a normal heart frequency or slight bradycardia. The Radiometer equipment TCM1 was used. The electrode surface tempertaure was 45.0 degrees C (within +/- 0.2 degrees C). The oxygen concentration in the inspired air was altered several times for all patients, and arterial samples were drawn at a stable PtcO2 level. On average, seven samples were drawn from each patient. The correlation between PtcO2 and PaO2 was highly significant in 4/5 patients, in both the "obese patient" group and the "normal patient" group. In the "hypothermic patient" group, the correlation between PtcO2 and PaO2 was highly statistically significant in 2/5 patients. The regression line between PtcO2 and PaO2 was calculated for each patient, and a mean regression line was obtained for each group. It was found that the regression line in the "obese patient" group was displaced to the right and parallel to the regression line in the "normal patient" group, while the regression line in the "hypothermic patient" group was less sloping and showed a higher intercept. The PtcO2 monitoring technique reliably reflects changes in the central oxygenation of adult intensive care patients. In some patients with decreased skin circulation, the relationship between PtcO2 and PaO2 seemed to be constant for the same patient, yielding statistically sifnificant correlations. However, the study cannot determine whether this would be true in all clinical situations; the relationship betwee PtcO2 and PaO2 should therefore be checked frequently when measruements are performed in patients with decreased skin circulation. The author's experience with the PtcO2 monitoring method in patients near death has been consistent with the obvious fact that the reliability of the method decreases with decreased skin circulation.

Adult↗
PubMed1979

Some characteristics of transcutaneously monitored oxygen partial pressure in normal newborns.

The transcutaneous oxygen partial pressure (PtcO2) was monitored in 50 healthy, normally and spontaneously delivered newborns. Measurements were performed during the first to fourth day of life. The electrode temperature was 44.5 degrees C. The mean PtcO2 level recorded during about 45 min was 9.2 kPa (S.D. 1.4) recorded from the minute-to-minute values. The PtcO2 level normally oscillated to a certain extent and the oscillations were closely related to the breathing pattern of the patient. When the patient fell asleep during measurement, the normal oscillating pattern was replaced by a "silent pattern". During crying, the PtcO2 level showed four main reaction aptterns. A decrease in the PtcO2 level could be observed during breast-feeding. One child, recently fed, vomited a small amount of breast milk after a short period of crying and apparently had a laryngospasm, shown by a sudden drop in the PtcO2 level without any other signs of discomfort. The study shows that PtcO2 (and thus also PaO2) very sensitively reacts to changes in activity. This implies that earlier used methods for determination of PaO2 might give values that are not representative for the steady state as the sampling method per se might influence the recorded PO2 value.

Breast Feeding↗
PubMed1979

Fetal breathing movements and maternal exercise.

Earlier statements that fetal breathing movements (FBM) are sensitive to changes in the fetal homeostasis prompted the study of the effect of maternal exercise on FBM and fetal heart rate. Forty women in the last trimester of gestation were subjected to a work load (80 W) for 5 min on a bed ergometer cycle; in 30 of them FBM were recorded by A-mode ultrasound, and in 10, the fetal heart rate was monitored by continuous ultrasound. Maternal blood pressure, pulse rate, blood pH and pCO2, and transcutaneous pO2 were also followed. The FBM showed a transient marked increase in incidence immediately after the end of the exercise. No changes in basal level or in baseline variability of the fetal heart rate were found in the recovery period after work. Some possible causes of the observed FBM alterations are discussed. The findings imply that, after this particular form of stress, FBM are a more sensitive indicator of the physiological state of the fetus than the fetal heart rate.

Adult↗
PubMed1979

Effects on fetal breathing movements of maternal challenges. Cross-over study on dynamic work, static work, passive movements, hyperventilation and hyperoxygenation.

Ten women in the last trimester of a normal pregnancy were subjected to five different loads in a cross-over study. Fetal breathing movements (FBM), fetal heart rate (FHR), maternal heart rate (MHR), and mean arterial pressure (MAP), maternal transcutaneously measured pO2 (Tc-pO2), and the energy supply to the Tc-pO2 electrode were recorded continuously before, during, and after the load. Maternal capillary pH and pCO2 were measured at three representative time points. The immediate responses of the incidence of FBM to the different challenges were: increase after dynamic work (bicycle test); no change after static work (isometric muscle contraction) and passive movements; decrease after hyperventilation and hyperoxygenation. FHR was unaffected by all challenges. The FBM incidence varied in parallel with pCO2 after dynamic work and hyperventilation and inversely with the Tc-pO2 rise caused by hyperoxygenation. Maternal pH was increased after passive movements (no change in FBM) and after hyperventilation (decreased incidence of FBM), FBM seem to be more sensitive to environmental changes than is the FHR. Mechanical stimuli to the uterus were not responsible for the augmentation of FMB seen after the bicycle test. The present observations reveal the multifactorial nature of the regulation of FBM, and support the role of CO2 as a major stimulator of breathing movements also in prenatal life.

Adult↗
PubMed1979

The influence of different electrode temperatures on the recorded transcutaneous Po2 level.

The technique of transcutaneous monitoring of oxygen partial pressure (PtcO2), first described in 1969, provided a new clinical possibility for continuous and noninvasive surveillance of changes in the oxygenation of the organism. To obtain optimal arterialization of the skin and thus a relieable recording, the electrodes used have been supplied with microheating elements. The electrode temperature used implies the risk of producing burns; this is especially true when the measurements are performed in patients with decreased skin circulation or in immature children with a thin and vulnerable skin. Thus, a careful choice of the electrode temperature is important in PtcO2 recording; a higher temperature is desirable for obtaining adequate arterialization, whereas a lower temperature is preferred for reducing the risk of burns. The electrode temperatures described for PtcO2 measurements range from 42--45 C. A systematic study with the Radiometer TCM 1 equipment showed that changing the electrode temperature influences the OtcO2 in a systematic way within the temperature range 43.0--45.0 C. The study also showed that simultaneous measurements obtained from two electrodes with different temperatures showed a highly parallel course and a comparable oscillating pattern within this temperature range. The results of the present study suggest that an electrode temperature of 44.5 C may be the most appropriate for this equipment in clinical applications with newborns.

Electrodes↗
PubMed1978

The effect of fibrin deposition on the sensitivity of the continuous monitoring pH electrode and on the recorded pH value: an in vitro study.

One of the problems concerning the continuous pH-monitoring technique is whether the relationship between pH measured by the electrode and pH in central and/or capillary fetal blood is constant. To test to what extent a fibrin clot deposited on the pH-electrode influenced the recorded value and the sensitivity of the electrode, the following in vitro study was performed. Fibrin was deposited on the pH-electrode by means of thromboplastin and fibrinogen, or by thromboplastin and whole blood. The deposition of a clot was verified by inspection of the electrode in a microscope. The time for stabilization of the recorded pH-value and the recorded pH-value was measured in standard calibration solutions before and after deposition of the fibrin clot and after decomposition of the fibrin clot by plasmin. FDP was measured in the decomposition solution. From the study it was obvious that the stabilization time of the electrode was considerably influenced by deposition of an "unphysiological" fibrin clot, less so if the clot was deposited by means of whole blood. The recorded pH-value was not influenced.

Electrodes↗
PubMed1978

Transcutaneous Po2 monitoring in neonatal intensive care.

The transcutaneous Po2 monitoring technique was applied in 20 newborns. The method proved reliable during hypoxemia, normoxemia and hyperoxemia, with a high correlation between Ptco2 and Pao2 in simultaneously obtained arterial samples. Although Ptco2 reliably reflects changes in Pao2, occasional arterial samples are still required for establishing the relationship between Ptco2 and Pao2, especially in patients with impaired circulation. When this relationship has been determined, the therapist may rely on the recorded Ptco2 level for hours, given that the energy supply required to maintain the electrode at a preset temperature level remains constant. A considerable difference between Ptco2 and Pao2 or a change in the energy supply level to the electrode may alert the therapist to check the patient's circulatory status. The Ptco2 technique is now fully developed and can be recommended for use in neonatal intensive care.

Blood Gas Analysis↗
PubMed1977

Monitoring of transcutaneous PO2 in the fetus and mother during normal labor.

Transcutaneous PO2 (tcPO2) measurement is a non-invasive method which gives continuous information about central PO2. The method has previously been testes primarily on newborns and adults, and reports on the applicability of the method on the fetus during labor are still scanty and restricted to case reports. This paper reports on a systematic study of intrapartum fetal and maternal tcPO2-monitoring. The material is comprised of 19 parturients, the majority being nulliparae. All fetal presentations were vertex. The tcPO2 recordings averaged one hour in duration (Tab. I). FHR was recorded simultaneously. In 12 cases the electrode was affixed with glue, and in 7 cases a suction device was used for fixation. The electrode was attached when the cervix was dilated 4 to 6 cm. The mean tcPO2 was 20 mm Hg in the beginning of the registration, and showed a small decline in level throughout labor reaching 14 mmHg at the end of the registration period (Fig. 5). These values are in good agreement with those found by other authors in previous investigations. In some of the present cases, very low tcPO2 values were recorded. The relevance of these low tcPO2 values is unclear, and it is impossible to determine to what extent these tracings have true physiological relevance versus might be due to technical factors.

Electrodes↗
PubMed1977

Transcutaneous monitoring of PO2 in different skin areas in the neonate and in the scalp of the fetus during labor - methodological and physiological observations.

The reliability and physiological significance of continuous non-invasive PO2 recording by means of skin electrodes was studied by comparing simultaneous tracings from different skin areas in a series of 40 newborns with normal labor and birth. A new measuring equipment - the Radiometer prototype unit TPM 1 - was used. In addition, the applicability of the method to the fetus was tested in a primary series of 11 labor cases. Certain technical and physiological factors that can influence the tracings were identified.

Electrodes↗