Infections and hyperbaric oxygen : new methods for highdose protocols and noninvasive measurements

Abstract: The scientific evidence of Hyperbaric Oxygen Treatment is despite the fact that the hyperbaric method has been in use since 1662 still under debate. At Karolinska University Hospital the method has been under the supervision of the department of anesthesia and intensive care since 1990. The number of treatments increased slowly and reached a total of approximately 3000 /year in 2008 (fig 1) although evidence of the efficacy slowly developed. The facility develops towards HBO for intensive care patients, a real challenge because of the demand for high technology in high-pressure and fire hazard surroundings. Infectious disorders such as severe soft tissue infections or postoperative neurosurgical infections have slowly developed to make a large part of the patients (fig 1). In 2005 a committee from Karolinska Institutet inspected the facility and identified among other things the lack of clinical research projects. My thesis was therefore started first with a description of one of our large patient groups (paper I) and with the aim to perform clinical research projects for severe soft tissue and neurosurgical infectious patients using prospective randomized protocols. The lack of evidence for the correct dosage of HBOT and the lack of non-invasive methods to measure oxygen content in tissues during treatment soon became evident. These issues made the efforts to construct conclusive prospective protocols seem premature and the focus of the thesis changed to help providing a solid basis for future HBO studies. We tested 2 non-invasive methods to monitor oxygen content in target tissues, NIRS and PPG, and developed a new method (HOPAN) to make it possible to treat intensive care patients according to patients’ demands without risk of DCS for attendants. NIRS measurements provided focus on soft tissues and PPG on bone tissues. NIRS (paper II) and PPG (paper III) have been tested with healthy subjects during NBO and HBO. NIRS was found to follow the inhaled oxygen within minutes. Using PPG technique we found individual changes in blood flow following the inhaled oxygen also within minutes. NIRS is a commercially available method though not yet approved for use in hyperbaric chambers. PPG equipments for clinical use are not yet available. To make it possible to test HBO doses with the focus on patient need instead of the conventional compromise between the attendants safety and patient need we constructed a protocol with nitrox breathing for attendants (HOPAN, study IV). In our retrospective evaluation the method we found the method to be safe for both patients and attendants. Both the tested non-invasive oxygen monitoring methods and the new HBO method will hopefully make a contribution to the development of good clinical prospective randomized research protocols.