Pulmonary function in men after repeated sessions of oxygen breathing at 0.25 MPa for 90 min.
OBJECTIVE
We wanted to evaluate the pulmonary effects of discontinuous oxygen breathing (15 min O2, 2 min air breaks, 15:2), at 0.25 MPa once a day for 90 min O2 (6 sequences) over 10 d. This sequence, which has never been evaluated, is currently used in our hyperbaric therapy center.


METHODS
Clinical and functional pulmonary status (questionnaire, spirometry, flow/volume loop, pulmonary diffusing capacity for carbon monoxide) was assessed in 10 non-smoking healthy volunteers after one exposure at 0.25 MPa consisting of 90 min of discontinuous oxygen breathing (15:2) and in 10 non-smoking patients who received a hyperbaric treatment consisting of 90 min of the same discontinuous O2 breathing (15:2) once a day over 10 d. The patients received daily intravenous methylprednisolone (1 mg x kg(-1)) and nicergoline (60 mg).


RESULTS
There were no respiratory symptoms in either group. As expected, for a single exposure of that duration, lung function did not change in volunteers; however, a significant decrease in maximal expiratory flows (MEF) at 50 (-15%) and 25% (-33%) of forced vital capacity (p < 0.05) without change in forced vital capacity (FVC) appeared in patients treated over 10 d.


CONCLUSIONS
Repetition of the 15:2 oxygen breathing sequence for 90 min once a day over 10 d led to greater flow limitation in peripheral airways than reported after continuous oxygen breathing of 210 min at 0.3 MPa which showed a 7% decrement in MEF50 and a 12% decrement in MEF25. No studies reporting these indexes were found in the 0.2-0.25 MPa range. Similar decrements in MEF50 and MEF25 with steady FVC have been reported after 14 d of daily hyperbaric therapy (0.24 MPa) with 30:5 sequence (-9% and -13%, respectively), 80% of the patients were symptom free. Similarily, our patients were all symptom free and remained so 1 yr after the study, hence, this toxicity is of weak clinical significance in subjects free of inflammatory lung diseases. HBO therapy, though safe, is not totally without effect on the lung.
Mialon
P
P
Pulmonary Function Test Unit, Department of Anesthesiology, Brest, France. mialon@univbrest.fr
Barthélémy
L
L
Michaud
A
A
Lacour
J M
JM
D000328:Adult; D005260:Female; D006801:Humans; D006931:Hyperbaric Oxygenation / Q000009:adverse effects*; D018496:Hyperoxia / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology; D013147:Spirometry; D014109:Total Lung Capacity / Q000502:physiology; D014797:Vital Capacity / Q000502:physiology