Can hyperbaric oxygenation improve cognitive functioning in the organically impaired elderly?: a critical review

The present article reviews experimental investigation concerned with the effect of hyperbaric oxygenation upon cognitive functioning in the organically-impaired elderly. The conclusion of the Jacobs et al. studies was that hyperbaric oxygenation in cases of chronic organic brain damage (regardless of etiology) leads to improvement in cognitive functioning and general behavior on the ward. Goldfarb et al. (1972) found no evidence to support this conclusion. A critique of the above studies indicates several methodological weaknesses. First, there are serious reservations concerning the makeup of the samples employed in the Jacobs et al. (1969, 1971, 1972, 1973) investigations: it is highly uncertain that most of the Jacobs et al. subjects were suffering from moderate or severe chronic organic brain damage. One reason for the discrepancy between the Jacobs and Goldfarb studies is that the subjects in the later study were more deteriorated and perhaps not as amenable to hyperbaric oxygenation. Secondly, the Bender-Gestalt Test and Tien's Organic Integrity Test have not been validated in an elderly sample. The gain evidenced on the Stockton Geriatric Rating Scale (Jacobs et al., 1969, 1971, 1972) may have little practical significance, and since the data were pooled across groups, the so-called falloff effect could not have been measured. Third, and most significantly, the experimental designs employed in the Jacobs et al., the Goldfarb et al., and the Jacobs followup investigations have such serious shortcomings that the findings must be regarded as inconclusive. Such factors as experimenter attention, testing effects, and familiarity with the experimenter could account for the change in cognitive functioning. Further, in the case of the Jacobs et al. study, the ward personnel may have treated the control group differently after learning that they were expected to improve. Additionally, the subjects in the Jacobs et al. study (1969) themselves may have heard about this prognosis and may have become more interested in performing well on the psychological tests. Thuse, there is no unambiguous evidence that hyperbaric oxygenation was responsible for the changes or lack of changes in cognitive functioning in the samples presented in these studies.