The present study examined the neuropsychological profiles of 134 patients with end-stage pulmonary disease who were being evaluated as potential candidates for lung transplantation. The primary findings from this study indicated that the frequencies of impairment exhibited by the patient group on 8 out of 10 of the SRT variables differed significantly from the expected normalized population frequency distributions for these measures when one standard deviation below the mean was utilized as the criterion for impaired cognitive performances. However, when a Bonferroni-corrected alpha level (Winer, 1971
; .05/25 = .002) was used to correct for multiple comparisons, only three of the SRT variables’ frequencies of impairment remained significantly greater than the expected population frequency distributions. These SRT variables included: Immediate Free Recall, Long-term Retrieval, and Consistent Long-term Retrieval. Furthermore, as noted in , 46.43% of these patients with end-stage pulmonary disease exhibited impaired immediate recall of a list of “selectively presented,” unrelated words over successive (up to 12) trials, while 41.67% of these individuals displayed difficulties retrieving these words from memory, and 51.19% experienced impairments of their consistent/ uninterrupted retrieval of these words over trials.
These findings appear generally consistent with those obtained in smaller studies conducted by the present authors of patients with end-stage cystic fibrosis (Crews et al., 2000
), alpha-1-antitrypsin deficiency (Jefferson et al., in press
), and COPD (Crews et al., 2001
). The similarities between these past studies and the present one were not overly surprising given that the data (on a total of 69 patients) from our previous investigations were consolidated with data from 65 new cases to form the current patient sample.
In contrast to the frequencies of impairment exhibited by patients on the SRT Immediate Free Recall, Long-term Retrieval, and Consistent Long-term Retrieval variables, patients displayed lower rates of impairments on tasks assessing immediate (and delayed) free recall of contextual verbal material (i.e., WMS-R/III Logical Memory I and II subtests). These findings suggest more intact immediate (and delayed) free recall of contextual versus noncontextual/unrelated verbal material in this sample of patients with end-stage pulmonary disease.
The patients in this study also exhibited lower rates of impairment on subtests (i.e., WMS-R/III Visual Reproduction I and II) assessing immediate and delayed free recall of visual/figural material as compared to their rates of impairment on the SRT immediate and delayed free recall measures. These findings are suggestive of relatively more intact immediate (and delayed) visual/figural memory in this sample of patients as compared to their memory for noncontextual verbal material. It should also be noted that almost twice as many patients exhibited difficulties recalling visual/figural designs after 30 min (i.e., delayed recall) as compared to their recall immediately after presentation.
On another measure involving noncontextual verbal material (i.e., RAVLT), patients displayed lower frequencies of impaired immediate and delayed free recall as compared to their immediate and delayed memory performances on the SRT. This finding suggested that the SRT, as compared to the RAVLT, may be a more sensitive index of impaired immediate and delayed free recall of noncontextual verbal material in patients with end-stage pulmonary disease.
Although approximately 8–20% of the patients in the present study displayed impairments on measures (i.e., Trail Making Test, WCST) purported to be sensitive to executive functioning, no significant differences were found between the frequencies of impairment exhibited by this sample on these measures and the expected population frequency distributions, when one standard deviation below the mean was utilized as the criterion of impaired cognitive performance. Thus, the number of patients who displayed impairments of their cognitive processing speed, visuomotor scanning abilities, and cognitive flexibility/sequencing skills on the Trail Making Test was not significantly greater than would be expected in the “normal” population frequency distributions. Similarly, the proportions of the current sample that exhibited impaired maintenance of response strategies and concept formation/reasoning skills were also not significantly different from the expected population frequency distributions for the WCST.
On the MMPI-2/A, the mean profile of the patients with end-stage pulmonary disease revealed significant elevations on Scales 1 (Hypochondriasis) and 3 (Conversion Hysteria). The group’s mean MMPI-2/A clinical profile suggested that they acknowledged a diversity of somatic symptoms that likely worsened during times of stress (Graham, 1993
; Greene, 1991
). They also endorsed items suggestive of a reduced level of efficiency and complained of feeling weak, tired, and lethargic. Taken together, such profiles were not unexpected in patients who often experience multiple medical/physical complications secondary to their end-stage pulmonary disease. Individuals with these profiles may also be somewhat dependent and feel as if life is treating them unfairly (Greene, 1991
). They may utilize denial and repression in an attempt to cope and lack insight that psychological distress may be contributing to their difficulties (Graham, 1993
; Greene, 1991
). In contrast, these patients may be somewhat overcontrolled and present themselves as responsible and conforming (Graham, 1993
; Greene, 1991
). It should also be noted that the current sample’s mean MMPI-2/A profile was similar to our past studies of patients suffering from end-stage cystic fibrosis (i.e., 1–3–2 mean clinical profile; Crews et al., 2000
) and COPD (i.e., 1–3 mean clinical profile; Crews et al., 2001
). Furthermore, the MMPI-2 findings in this study appear to support the psychological findings of previous investigations involving patients with COPD that have found symptomatology such as reactive depressions, generalized dissatisfaction with life, and preoccupation with somatic complaints, as well as clinical elevations on the Hypochondriasis, Depression, and Hysteria scales of the MMPI (McSweeny et al., 1982
; Prigatano et al., 1984
In sum, the findings from this study revealed that this sample of patients with end-stage pulmonary disease exhibited significantly greater frequencies of neurocognitive impairment (as compared to the expected population frequency distributions) only on SRT tasks that particularly involve the “selective reminding,” retrieval, and immediate recall of an unrelated word list that is presented aurally. While it remains unknown whether these results are more strongly related to the sensitivity of the SRT (vs. other measures) to identify certain types of neurocognitive (i.e., verbal memory) dysfunction and/or if end-stage pulmonary disease somehow differentially impairs the functional brain system responsible for certain aspects of verbal memory to a greater degree than other cognitive systems, it is likely that patients’ neurocognitive test performances were negatively impacted by their progressive declines in pulmonary functioning and resulting chronic hypoxia (see Lezak, 1995
). Furthermore, as pulmonary disease advances, hypercapnea (increased blood carbon dioxide levels) may result secondary to ineffective exchanges of gases (Stuss et al., 1997
). Stuss et al. (1997)
have provided some data gathered from COPD patients suggesting that hypercapnea may have a more deleterious effect on neurocognitive functioning as compared to reduced oxygen delivery. Grant et al. (1982)
have also theorized that pulmonary disease patients may suffer from other diseases, which, in combination with their pulmonary disease, may compromise their cerebral functioning. Similarly, Prigatano et al. (1983)
have hypothesized that chronic pulmonary disease may enhance preexisting vascular disease and accelerate the aging process resulting in decreased cerebral blood flow and oxygen consumption and deficient neurocognitive performances. Finally, since psychological distress has been widely shown to negatively impact neurocognitive functioning (see Lezak, 1995
), patients’ neurocognitive deficits may have also been exacerbated by their reported levels of psychological distress as reflected in their elevated MMPI-2/A clinical profiles.
The findings from this study appear to have important implications for clinical practice. Although as a group, patients demonstrated their most frequent neurocognitive impairments on tasks involving immediate free recall and retrieval of noncontextual verbal material, notable numbers of patients also exhibited impairments on measures assessing contextual verbal and nonverbal memory, as well as on tasks purported to be sensitive to executive functioning. Thus, based on the diversity of neurocognitive and psychological dysfunctions observed in these patients, clinically, it appears important to obtain comprehensive neuropsychological evaluations on all patients with similar end-stage pulmonary diseases who are potential lung transplant candidates. Specifically, since such patients must be capable of complying with often complicated and changing medical treatments/medication regimens both pre- and post-transplantation, comprehensive neuropsychological evaluations may be beneficial in identifying individual neurocognitive strengths and weaknesses. In turn, individualized, remedial treatments/therapy strategies (e.g., education as regards memory enhancement techniques, placing information to be retained in a verbal or visual context depending on a particular patient’s most efficient learning strategies, providing concrete/simplified medical treatment directions) can be formulated for patients with identifiable neurocognitive difficulties to help them compensate for their deficiencies and to increase their compliance with medical treatments and medication regimens. Identification and treatment (e.g., via psychotherapy and/or psychotropic medication management) of patients with significant psychological distress is also important to enhance their overall senses of well-being and mental health and to maximize their levels of neurocognitive functioning.
Future research is required with similar patients with chronic pulmonary disease to examine the precise mechanisms that are involved in the neurocognitive impairments that were identified in this study. The potential changes in such patients’ neuropsychological functioning over time and the impact that various medical interventions/treatments and lung transplantation may have on their neurocognitive processes should also be studied.