Effects of a standard hyperbaric oxygen treatment protocol on pulmonary function

The prescription of hyperbaric oxygen (HBO) therapy for disorders not relat ed to diving is increasing. Pulmonary oxygen toxicity is well known, but th e effect of the cumulative oxygen exposure corresponding to a standard HBO treatment protocol has not been quantified before, Twenty patients (10 male) had 21 HBO treatments at a partial pressure of ox ygen of 240 kPa for 90 min daily, None had any previous lung disease and al l had normal chest radiography and lung function at the start of the study. Dynamic lung volumes, forced expiratory hows and the transfer factor of th e lung for carbon monoxide (TL,co) were measured before the HBO treatment, on days 7, 14 and 21 during treatment and then 3-4 weeks after treatment. Four patients (one male) reported nonproductive coughing during the last we ek of treatment. There was a progressive reduction in forced expiratory vol ume in one second (FEV1) (p<0.001), mean Forced mid-expiratory Bow rate (FE F25-75%) (p<0.001) and forced expiratory hows at 50 and 75% of forced vital capacity (FVC) expired during HBO treatment, The reduction in FEV1 on day 21 was 4.4+/-1.7% and in FEF25-75% 10.3+/-6.1%. Four weeks after treatment there was a partial normalization, There were no changes in FVC or peak exp iratory now (PEF). TL,CO was slightly reduced on day 21 of treatment only ( p<0.01) and fully normalized 1 month later, A reduction in small airways conductance is consistent with other studies w here total oxygen exposures have been below the limit causing toxic pulmona ry effects traditionally measured as a reduction in vital capacity, This ef fect is not considered to be of any clinical significance for patients trea ted with hyperbaric oxygen unless repeated treatment series are to be given .