THE EFFECT OF HIGHVERSUS LOW PRESSURE ON THE PNEUMATIZATION OF THE MASTOID CELLS AN EXPERIMENTAL STUDY

Abstract

It is generally- recognized that the extent of pneumatization of the mastoid cells may be genetically determined. On the other hand, otitis in infancy has been considered an inportant factor associated with underdeveloped mastoid cells. The author and T. Goto do not agree with this opinion and have believed that the development of the mastoid cells may be genetically determined.Recently T. Goto and S. Shibata have reported that there is a marked fibrosis in the lungs of skin divers and limited development of the mastoid cells. From these results they suspected that pressure might have some influence on the extent of pneumatization of the pneumatic cavities, the lungs, accessory sinuses and mastoid cells.The author has planned to study experimentally the effect of pressure upon the mastoid cells.For this experiment he constructed a pressure tank, in which constant pressure could be maintained at 3 atmospheres or at a pressure of 2/5 of an atmosphere. The oxygen was insufflated into the tank under constant pressure.The animals used for this experiment were young chickens 7 days old at the start of the experiment. The chicken has well-developed mastoid cells and its mastoid cells develope very quickly. The experiment was carried out on the two main groups, namely the high pressure group and the low pressure group. Chickens in each of the groups were placed in the tank for 2 hours daily. In each of these groups the observation was made at the end of 30 and 60 days on 15 chickens in each subgroup. During these experiments chickens have not shown any gross changes. The development of the chickens was not delayed compared with the control chickens.But the mastoid cells of each group were markedly underdeneloped. The septae of the air cells were thickend and the lumen of the-cells were decreased in size. The bight of the linning epithelial cells was increased and the subepithelial tissue was fibrous and thick. Residual cartilage tisstue was found. The microscopic appearance of the air cells in chickens exposed for 60 days to high and low pressures are similar. The normal process of development, in which leucocytes infiltrate the subepithelial tissue, macropgages cause bony resorption, and the epithelium proliferates causing an increase in pneumatization, is delayed.These findings indicate a delay in the development of the mastoid cells. The findings in the mastoid cells of chickens in the two groups were similar, whether they exposed to positive pressures or negative pressures. The animals exposed for the longer time period (60 days) revealed only a slightly increased limitation in the development of the development of the mastoid cells than seen at the end of 30 days.