The working field technique proposed by Nouri 1977 (Fig. 6) gives a laminar upward flow, but it handicaps the neurosurgeon. Most important is the position of the critical zones in relation to the germ-free air because the air behind the nurse or the doctor is demonstrably contaminated. To avoid such contamination one can use a head piece (Fig. 7) like an astronaut (Weber, Stiihmer, and Meierhans 1973), which is uncomfortable and makes conversation difficult and an operation with the operating microscope impossible. The advantage is a very low degree of contamination and better cooling. zone of admission I I i I i zone of o'peration I y 'f q, I i I i I i zone of used air ', i i i ~_ _~ _ a -- -- ~--_ _~J ..:_ _ _ ..Z -- Fig. 8. Differentiation of zones of clean air and used (contaminated) air (Sattel, Peiper, Berendt) --------~_ _~ .... ~--> Fig. 9. Arrangement of persons, devices, and instruments, operation-table, and patient in relation to the first air We have to differentiate several zones in the operating room: admission of air (first air), the zone of action, and the zone of used air (Fig. 8). All things have to be arranged so that the most sensitive parts lie in the field of first air; in general the instrumentation table and the operation field have to lie in the first air zone (Fig. 9). Using jet stream supporting technique this field can be enlarged. Investigations have shown that a considerable decrease in the infection rate can be achieved. Using the clean room technique a working group in Switzerland (Weber, St~ihmer, and Meierhans 1971) found 1 infection in 350 operations; in Germany another group (Peiper, Sattel, and Schubert 1974) found 3 infections in 1272 opera- tions. Using a conventional technique the rate was at least three times greater. It is necessary to take care of the used air because epidemic problems may arise. However this is outside the scope of this paper, and wili not be discussed here. General Discussion The discussion dealt with the following topics. Its results are summarized. Classification of neurosurgical operating rooms: In general, neurosurgical theatres belong to class II of clean rooms. For long and difficult operations with open CSF space the highest requirements of clean room technique are thought to be necessary. Wearing helmets: Using pseudolaminar or laminar flow technique and respecting the arrangement of critical places in the first air there is no necessity for helmets, besides operations with the microscope would be impossible. Suction under the mask can give greater com- fort, and it certainly lowers the contamination rate. Evaluation of costs of clean room technique and risk of contami- nation: In evaluating expenses and prices against the advantages of clean-room-technique over the risk of infection, the use of pseudo- laminar or jet stream supporting-technique (Allander) seems to be 5ustified.
The conventional technique is insufficient because of turbulences with the high risk of contamination (for instance previ- ously sedimented germs). The administration of antibiotics cannot be considered as a solution to the problem of contamination. Evaluation of costs: The lowest costs will be brought about with the local technique. However, this handicaps the neurosurgeon. The total room laminar flow technique is the most expensive. The relation between the prices of Set stream supporting technique and laminar flow technique is 1 : 2-3. Risk of certain neurosurgicaI procedures: Using suction and air- drills neurosurgical procedures include a severe risk of contamination if the air is contarnined. So far, suction in operating rooms with con- ventional air conditioning systems seems to be most dangerous. With pseudolaminar and laminar flow techniques, and with proper place- ment of critical actions in the first air no additional risk arises. Movement of persons: Regarding the admission of particles and the possibility that every particle is a germ, at least a germ-carrier, less movement is needed. For instance, nurses can sit down.
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