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Biomedical subjects

P K Andersen

Publications and source records attributed to P K Andersen.

At least 145 records · Page 8Linked to original sources
PubMed1979

Comparison of anti-pollution modifications of Mapleson A and D anaesthetic systems.

Hafnia A and Hafnia D anaesthetic systems are non-polluting modifications of the Mapleson A and D systems. The excess gas is vented in the Hafnia systems directly and continuously via a calibrated ejector flowmeter. Sixteen adult patients anaesthetized for abdominal surgery were ventilated and either Hafnia A or D systems at six different fresh gas flows. No difference between the Hafnia A and D systems could be demonstrated in the values of arterial carbon dioxide tension measured with the same fresh gas flow, despite gas flows in opposite directions.

Aged↗
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↗
PubMed1979

Arterial carbon dioxide tensions during anaesthesia with manual ventilation. A descriptive study of the effects of various non-polluting circuits.

In 660 supine, intubated and anaesthetized, healthy patients scheduled for various elective surgical procedures, the distribution of arterial carbon dioxide tension (PaCO2) was investigated during manual non-monitored ventilation. The study comprised six equal groups: group 1: ventilation with a circle circuit absorber system; group 2: ventilation with the Hafnia A circuit using a total fresh gas flow (FGF) of 100 ml . kg-1 . min-1; groups 3-6: ventilation with a Hafnia D circuit with fresh gas flows of 100, 80, 70 and 60 ml . kg-1 . min-1, respectively. The mean PaCO2's of the first three groups were situated in the lower range of normocapnia (the observations in the first group having the greatest total range), whereas the rebreathing (Hafnia A and D) circuits resulted in a clustering of observed data. Employing the rebreathing circuits, protection against hypocapnia can be achieved by lowering the fresh gas flow. The most satisfying result was obtained with the Hafnia D circuit with a fresh gas flow of 70 ml . kg-1 . min-1 resulting in normocapnia with a modest and limited spread towards hypo- and hypercapnia. FGF in excess of this level must be considered as wasted. The study indicates that corrections of fresh gas flows for age are superfluous. Use of relaxants and type of surgery had no influence on the observations.

Adolescent↗
PubMed1978

The negative pressure relief valve: pressure-flow relationships.

The scavenging of gases from anaesthetic circuits may present hazards to the patient. The negative pressure relief valve prevents the generation of subatmospheric pressures in the circuit as a result of a discrepancy between the fresh gas flow and the gas evacuation rate. The ideal valve will open at a small negative pressure, and immediately permit a high gas inflow. Leakage with positive pressure in the circuit and admixture of atmospheric air during spontaneous respiration must not occur. Six different valves were studied. Two membrane valves came nearest to fulfilling the ideal requirements.

Air Pollution↗