. The goal of this study is an in vitro evaluation of thermal side-effects by the application of short sub- micro s CO(2) laser pulses in combination with an air-water spray on different types of bone tissue. A mechanically Q-switched CO(2) laser delivered 300 ns pulses at 9.6 micro m wavelength, which were focused down to a spot size of 440 micro m on the tissue (a corresponding energy density of 9 J/cm(2)). Bone samples (blocks from pig femur, rib, or cartilage) were moved through the beam repeatedly until 1-5 mm deep cuts were produced. An air driven water spray was applied to prevent the tissue dehydration. Subsequent visual and histological examinations revealed no carbonisation, melting traces or fissuring of the tissue. An extremely narrow, 2-6 micro m thick thermally altered layer was observed at the cut border in compacta and cartilage. No accumulation of the thermal damage occurred with increasing cut depth. Laser incisions in trabecular tissue were accompanied with a 100-200 micro m thick zone of thermal necrosis in bone marrow. The difference from compacta and cartilage can be explained considering the particular character of the spreading of the ablation products in the trabecular meshwork. Minor thermal side effects make the Q-switched and probably other short pulsed CO(2) laser systems interesting for hard tissue surgery.

In 6 normal and 7 obstructed excised human lungs the interrupter resistance (APTA, Jaeger Company) with an airway occlusion period of 100 ms was determined, by measuring the equivalent of the alveolar pressure at the end of the occlusion period. To check the pressure equilibration between the tracheal pressure and the alveolar space, catheters were put in the most peripheral layer of the lung. The lungs were ventilated in an artificial thorax. The airway resistance determined from the transbronchial pressure difference by the catheters was taken as a reference. Compared with the reference method, an overestimation of the airways resistance by the interrupter technique in normal lungs was found which was caused by an overshoot of the pressure equilibration during the occlusion period. In contrast, in severely obstructed lungs the pressure equilibration was not complete which led to an underestimation of the airways resistance by the interrupter technique. The best approximation of the airways resistance by the interrupter method was found in lungs with a low degree of obstruction.

Leiomyosarcomas in the mandible are extremely rare. The cases of a 40-year-old woman with a leiomyosarcoma in the mandible is reported. Diagnostic and therapeutic problems are discussed.

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Cones of malignant tumors are commonly known but only a few descriptions of cones in the head and neck area exist - as seen in a 91-year-old patient under our care. Cones of thymic and thyroid cancers are described in the literature. There are no descriptions of cones of head and neck squamous cell carcinomas. Metastases of squamous cell carcinoma in the head and neck area are very aggressive and have a high potential for vascular neogenesis. A vascular cone might be possible by vascular formation or by mechanical intrusion as described elsewhere.