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Biomedical subjects

J Waaben

Publications and source records attributed to J Waaben.

29 records · Page 2Linked to original sources
PubMed1980

The ejector flowmeter as air/oxygen mixing device. An apparatus providing gas mixtures with adjustable oxygen content for high-flow humidification systems.

The ejector flowmeter is constructed for continuous removal of excess gas from anaesthetic circuits. This instrument can be used as an air/oxygen mixing device for high-flow humidification systems in wards where compressed air is not available. Pure oxygen is used as driving gas through the ejector. A nomogram has been constructed to show the relationship between oxygen driving pressure, inlet of air to the flowmeter, FIO2 and total outflow.

Air↗
PubMed1980

The closed co-axial analgesia system.

A twin-tube system for nitrous oxide analgesia in dental surgeries is described. The system is a non-polluting modification of the Mapleson A system, employing the principle of co-axial tubing introduced by Bain & Spoerel (1972). Active, continuous and calibrated gas removal takes place via the co-axial tubing by means of an ejector flowmeter. Investigation of the dynamic pressure excursions occurring at the nose-piece are fully compatible with normal breathing. Gas contamination of the dental environment can be reduced by at least 90%. The system described is safe and easy to handle. It is made of light-weight material and is adaptable to the equipment available. No rebreathing takes place when using a fresh gas inflow of 150 ml/kg body weight/min.

Air Pollution↗
PubMed1979

Method for continuous measurement of carbon dioxide output during anesthesia. An assessment.

Employing the Mapleson D circuit, a modified closed-circuit flow-through technique for the continuous measurement of carbon dioxide production (VCO2) was tested for accuracy and precision in a lung model. The recovery of carbon dioxide production was found to be between 90 and 110%, the maximized errors for a single estimate of carbon dioxide production were between +/- 4 and +/- 28%, with the highest errors at high gas flows and low carbon dioxide inputs. Accepting arbitrarily chosen limits of maximized errors of +/- 10%, it could be shown that the system did not work acceptably when the mean carbon dioxide concentration was below 1.5 vol.% within the fresh gas flow rates (2.2--7.7 1 min-1) and the range of minute ventilation (4--10 1 min-1) employed. The half-life of carbon dioxide washout varied between 41 and 138 s, thus limiting the suitability of the system for detecting changes in carbon dioxide output. The method may be used as an approximate monitor of VCO2 in anaesthetized patients, but cannot be regarded as sufficient for research purposes.

Anesthesia↗
PubMed1978

Accuracy of gas flowmeters determined by the bubble meter method.

THe accuracy of 15 oxygen and nitrous oxide flowmeter units in daily use was investigated using the bubble meter method. At preset oxygen flow rates of less than 1 litre min-1 unacceptable errors were found. At flow settings greater than 1 litre min-1 the deviations varied within closer limits, but the actural flows were inaccurate irrespective of the presettings and of the gas delivered, and independent of the indicator being adjusted to be opposite or between the graduation marks on the flowmeter.

Methods↗
PubMed1978

The ejector flowmeter: an evaluation of its accuracy.

The accuracy of five ejector flowmeters was assessed using three different gases and four flow-rates. A soap-bubble flowmeter was used for the calibaration. Significant variations were found between individual flowmeters and between different gas mixtures. No variation was found between the four different flowrates, indicating that the calibration is linear. The mean calibration factor was 84.8% +/- 4.1 (100% O2:87.4 +/- 3.4, 50% N2O/O2: 84.2 +/- 2.8, and 100% N2O: 83.0 +/- 4.6).

Anesthesia, Inhalation↗
PubMedDate not supplied

Effect of epidural analgesia on muscle amino acid pattern after surgery.

Free amino acids in muscle were studied before and 96 hours after skin incision in 14 patients undergoing elective hip replacement and allocated to general anesthesia or epidural analgesia (T10-S5) effective before incision and maintained with intermittent 0.5% bupivacaine during the first 24 postoperative hours. The general anesthesia group (n = 8) showed the characteristic changes in muscle amino acids, with increase of branched chain amino acids and phenylalanine and decreased glutamine, arginine and lysine, as well as raised plasma levels of cortisol and glucose. The epidural group (n = 6), contrastingly, showed no significant changes in plasma cortisol and glucose and an attenuated postoperative response in all amino acids, without significant difference from the preoperative values. Differences in postoperative muscle amino acid concentrations between the epidural and the general anesthesia group were significant as regards glutamine, valine and asparagine. These results suggest that post-trauma changes in muscle amino acids are predominantly mediated by afferent neurogenic stimuli and the secondary increase in catabolic hormones.

Aged↗