Evidence for a subclinical involvement of the central nervous system in mild or moderate chronic respiratory insufficiency

Nineteen patients with mild or moderate chronic respiratory insufficiency, mean age, 63.3 y., have been investigated with pulmonary function tests, clinical examination and somatosensory (SEPs), visual (VEPs) and brainstem auditory (BAEPs) evoked potentials. Nineteen age and sex matched subjects acted as controls. None of the subjects had conditions known to affect the central nervous system (CNS). SEP N20 latency was significantly prolonged in 7 out of 19 patients and its mean value in the patients' group was significantly higher (21.02 vs 19.49 msec p <0.001). VEP P100 latency was prolonged in the patients' group in 16/38 and 15/38 eyes with spatial frequencies of 30' and 15' of arc respectively. The P100 mean value was also significantly prolonged in the patients' group for both eyes and spatial frequencies (108.08 vs 101.87 msec p <0.001 and 115.82 vs 107.63 msec p <0.001 for spatial frequencies of 30' and 15' respectively). No significant difference was evident with BAEPs. The data seem to support the hypothesis of a subclinical involvement of CNS in these cases, with preferential damage to the newer phylogenetic structures.