Untersuchungen zur künstlichen Beatmung bei der Maus (Mus musculus) mit dem UNO Micro-Ventilator®

In the present experimental essay the effect of controlled ventilation with the UNO Micro-Ventilator? (UMV) on the mouse is examined. The UMV is a pressure controlled and volume limited ventilation device with a sinus ventilation pattern and lowflow rebreathing of the respiration gas. Not only the impact of a preoxygenation is assessed but also the effect of different respiratory rates on mice of different weight. The assessment is made with blood gas analysis, circulatory parameters and histological examinations of the lungs. The animals can be assigned to nine groups: The non-preoxygenized animals are split up in six groups and the preoxygenized ones in two groups. Additionally, group H serves as histological control group. The non-preoxygenized animals of N100 are ventilated with a respiratory rate of 100 /min (n = 6), i.e. the animals of the N130 with 130 /min (n = 6). The animals in N100L (n = 8 settings) are non-preoxygenized, weigh between 25 and 38 grams and the respiratory rate is adjusted to 100 /min. The animals of the group N100S (n = 7) which weigh between 39 and 50 grams are not preoxygenized either. In P80L (n = 7, settings) the animals are ventilated with 80 /min, are preoxygenized, and their weight varies between 25 and 38 grams. Grouped in P80S (n = 7) are animals which weigh between 39 and 50 grams. Group H (n = 7, animals) was not ventilated and serves for the histological examination. To expose the animals to as little stress as possible they are premedicated to the intubation with the completely antagonizable injectable anesthesia medetomidine, midazolam, and fentanyl (MMF). With the beginning of the anesthesia with isoflurane (the concentration of the isoflurane is 2.7 vol.-%) the injectable anesthesia is antagonized with atipamezol, flumazenil, naloxone (AFN). The anesthesia lasts 100 minutes. The A. carotis of all ventilated animals is canulated in order to measure the blood pressure and take blood samples. Besides the blood gas results (pHa, pa CO2, paO2, BE, HCO3¯) the measured parameters are the blood pressure (in mmHg) and the heart rate (in beats /min). To ascertain the normal distribution the Kolmogorov-Smirnov test is carried out. The comparison between the groups is made with the distribution-free Mann-Whitney test. The level of significance is fixed at p < 0.05 (5 %). The mice of group N130 stay in the physiological sector with their blood gas results. Animals of group N100L show a respiratory acidosis. The preoxygenized P80L and P80S require a lower respiratory rate than non-preoxygenized animals independent of their weight. The medium arterial blood pressure of all groups sinks steadily while the heart rate increases at the same time. In the histological preparations of all groups including the control groups atelectasis, perivascular edemas, congestions and emphysemas can be seen. However, on what these pathological findings are based cannot be thoroughly explained. Therefore, mice should be preoxygenized 5 minutes prior to a ventilation. Thus, a respiratory rate of 80 per minute is sufficient for all weights. If not preoxygenized, a respiratory rate of 130 /min is suggested for animals up to 39 grams and approximately 110 /min for mice over 39 grams. With these settings the UNO Micro-Ventilator® is to be recommended for the ventilation of mice.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2003

Author dc:creator

• Römer, Dirk

Repository record source_url

https://edoc.ub.uni-muenchen.de/1777/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:1777