Decrement of the skin conductance response to repeated volitional inspiration.

OBJECTIVE: To examine response decrement of the recently reported inspiratory skin conductance response (SCR) [Lim CL, Seto-Poon M, Clouston PD, Morris JG. Sudomotor nerve conduction velocity and central processing time of the skin conductance response. Clin Neurophysiol 2003;114:2172-80]. METHODS: Twelve healthy adult volunteers performed 3 tasks (A) a control task of maintaining tidal breathing and then two randomized tasks, (B) a deep inspiration to a target oral pressure and (C) tapping with a finger. Each task was performed 30 times on cue every 20s in 3 runs with 5 min of rest between runs. The SCR, oral pressure, airflow, inspired volume and cue signal were recorded continuously and analysed offline. SCR amplitude was logarithmically transformed and then statistically analysed, using a linear mixed effects model, as a function of run number, trial number and absolute error between target and actual oral pressures. RESULTS: Inspiratory efforts elicited exponentially decreasing SCR amplitude with increasing trial number during each run (P < 0.0001). After adjusting for trial number, the mean SCR amplitude of the second and the third run were, respectively, 24.2 (95% CI (0.175, 0.336), P < 0.001) and 14.4% (95% CI (0.104, 0.200), P < 0.001) of the first run amplitude. CONCLUSIONS: Volitional deep inspiration reliably activates an SCR that exhibits response decrement with repetition, which may be habituation. SIGNIFICANCE: The volitional inspiratory SCR may assist in the assessment of sympathetic autonomic status in patients with peripheral afferent neuropathy.     

Avoidance behaviors in patients with implantable cardioverter defibrillators

BACKGROUND: Although the implantable cardioverter defibrillator (ICD) has become standard therapy for some malignant cardiac arrhythmias, the shocks delivered by the device are often experienced as aversive. Anecdotal accounts of patients avoiding specific objects or places raise the possibility that conditioned avoidance responses can be established in response to ICD shocks. OBJECTIVE: The objective of the study was to better understand the nature of avoidance behavior among ICD recipients and to examine the relevance of classical conditioning and cognitive models to ICD-related avoidance behavior. METHODS: A total of 143 recipients of ICDs completed an anonymous survey reporting on aspects of their experience with the ICD and whether they had begun avoiding specific places, objects, or activities since receiving an ICD. RESULTS: Fifty-five percent of respondents reported at least 1 category of avoidance since receiving an ICD. The frequency of reported avoidances was highest in activities (39%), followed by objects (27%) and places (17%), which were least avoided. There was no relationship between the reported experience of shocks and avoidance behavior, and little evidence for conditioned avoidance. CONCLUSION: Avoidance that is not medically recommended is common among patients with ICDs. This may have adverse effects on quality of life and perhaps the physical health of some patients. Cognitive models, rather than classical conditioning, seem to explain the majority of avoidance behavior reported in this sample. A brief educational intervention or regular participation in ICD support groups could help to dispel misinformation among patients and discourage inappropriate avoidance.