Chronic hyperbaric oxygen therapy causes only minor ultrastructural changes in the human nasal epithelium

Hyperbaric oxygen (HBO) therapy is becoming increasingly popular in the treatment of several pathologies, namely in vascular diseases. It is generally considered to be innocuous, with few restrictions. Thus, patients subjected to HBO therapy breath saturated oxygen at an elevated pressure. Since the respiratory mucosa comes into contact with this altered inhaled air, we decided to use light and electron microscopy to investigate whether chronic HBO therapy causes significant changes in the nasal mucosa. For this, we obtained biopsies of the anterior portion of the lower nasal turbinate from two groups of 9 individuals under direct visual inspection. The first group had a diagnosis of tinnitus and was subjected to 15 sessions of 100 min-long HBO treatments, and the latter group comprised healthy volunteers not subjected to HBO therapy. The samples were processed for light and electron microscopy. We found that the turbinate mucosa of the HBO-treated group showed a moderate infiltration by leukocytes and an increase in the thickness of the epithelial basement membrane. By transmission electron microscopy (TEM), we observed that only a minority of the nasal epithelial cells presented alterations due to the HBO treatment; these alterations were focal and restricted to cilia. We conclude that chronic HBO treatment induces only minor alterations in the nasal mucosa and that these are likely to be reversible when treatment is discontinued.