Teaching advanced life support skills.
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Cardiopulmonary Resuscitation↗
Biomedical subjects
W Riddle
Publications and source records attributed to W Riddle.
Short-term effects of electroconvulsive treatment on the uptake of 99mTc-exametazime into brain in major depression shown with single photon emission tomography.
Fifteen patients with major depression who were being treated with bilateral electroconvulsive treatment (ECT) were investigated before and 45 min after a single ECT using split-dose Single Photon Emission Tomography (SPET or SPECT) with 99mTc-Exametazime. All patients suffered from unipolar depressive illness and were rated on the Newcastle scale and with the 17-item Hamilton scale. They completed tests of orientation and verbal memory on the day of ECT. For comparison, verbal memory was also tested on the preceding day. The uptake of 99mTc-Exametazime was expressed relative to calcarine/occipital cortex. Significant decreases in tracer uptake were confined to the inferior anterior cingulate cortex. The changes were correlated with the severity of depressive symptoms and more weakly with decrements of memory function produced by ECT; there was no significant correlation with stimulus intensity or electroencephalographic measures of seizure duration.
Aged↗
The differentiation of major depression from dementia of the Alzheimer type using within-subject neuropsychological discrepancy analysis.
The method of comparing premorbid versus current intellectual ability has become established clinical practice in the differential diagnosis of dementia versus depression. Recently, Schlosser & Ivison (1989) suggested that the comparison of premorbid ability versus current memory function may offer a more sensitive method of assessing early dementia. In the present study, a variety of within-subject discrepancy analyses comparing premorbid estimates with current measures of memory and intellectual functioning were compared across three groups: patients with dementia of the Alzheimer type, patients with major depression and healthy controls. The results revealed that, while mean group differences were easily demonstrated, the overlap between Alzheimer and depressed patients was large. It is concluded that none of the simple neuropsychological discrepancy analyses examined in the present study can be recommended for use in clinical practice for the differential diagnosis of dementia from major depression.
Aged↗
A single photon emission computerised tomography study of regional brain function underlying verbal memory in patients with Alzheimer-type dementia.
Ten patients with Alzheimer-type dementia and nine age-matched normal controls were examined with SPECT, using split-dose 99mTc-labelled exametazime. The baseline condition involved repetition of the word 'yes' or 'no'. The activation condition involved recognition (indicated by a 'yes' or 'no') of words from a previously learned list presented along with distractor words. Patients who performed this task successfully were selected, and efforts were made to match the patients with controls according to their performance on the task, although this was not fully achieved. Uptake of 99mTc-exametazime was estimated at baseline and during the word-recognition task for predetermined regions of interest drawn from a standard neuroanatomical atlas. The baseline task appeared to normalise tracer uptake for frontal, temporal and parietal cortex in the patient group. However, during the recognition task, controls but not patients showed activation effects. These were most prominent in dorsolateral frontal cortex and adjacent anterior cingulate cortex. Among patients, successful performance was correlated with activation of dorsolateral frontal and parietal cortex on the left side. The results confirm the central role of frontal mechanisms in a recognition memory task. The study highlights some of the difficulties of using cognitive challenge tests in clinical groups.
Acoustic Stimulation↗
Status epilepticus after electroconvulsive therapy.
Status epilepticus is a rare complication of ECT. We describe a patient who suffered a prolonged seizure which required termination with intravenous diazepam. The status epilepticus was not accompanied by motor movements, and the diagnosis was made only because of simultaneous EEG monitoring. The incidence of status epilepticus after ECT may be underestimated.
Acetaminophen↗
Relation between respiratory neural output and tidal volume.
We recently described a model for the relation between respiratory neural and mechanical outputs (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 51: 963-1001, 1981). In this communication we utilize the model to address the following questions. 1) How sensitive is tidal volume (VT) to shape and timing of respiratory neural output (N)? 2) How effective are shape and timing characteristics of N in load compensation? 3) For a given VT, what is the most economical shape and timing of N? Using different values of passive respiratory mechanics, we generated the VT profiles associated with theoretical N waveforms having different shape and timing parameters. We found that 1) with normal mechanics VT is moderately sensitive to inspiratory time (TI) but not to shape of N, whereas with high resistance and short TI, VT is very sensitive to shape and timing; 2) changes in shape, within the physiological range, can serve as potent load-compensatory mechanisms; and 3) for a given VT, the most economical (lowest mean pressure) N pattern is one with a very short TI and a rising phase that is convex to time axis. This holds true even with high resistance.
Lung Volume Measurements↗
A model for the relation between respiratory neural and mechanical outputs. I. Theory.
A model for the conversion of respiratory neural output to mechanical output, and vice versa, is described. Neural output was expressed in terms of isometric pressure generated at passive functional residual capacity. The mechanical response time constant of respiratory muscle was assumed to be 0.06 s. The effect of volume and configuration on pressure output was modeled after the data of Grassino et al. (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 44: 829-839, 1978). Equations were developed to examine the effect of different configurational pathways during inspiration. We utilized Hill's hyperbolic force-velocity relation to model the effect of flow on pressure output. The pressure asymptote of the hyperbola was considered to be similar to that in other skeletal muscles (0.25 isometric pressure). The flow asymptote was derived from data obtained during maximal voluntary inspiration. A major feature of the model is the dependence of volume, configuration, and flow-related pressure losses on level of inspiratory activity. The practical effect of potential errors and the overall accuracy of the model are presented in the two succeeding communications.
Animals↗
A model for the relation between respiratory neural and mechanical outputs. II. Methods.
In the preceding communication we developed a model for the conversion of neural output to mechanical output. We were left with two qualitative uncertainties, namely, the relation between neural output and isometric pressure, and the behavior of inspiratory muscles during expiratory flow; and two quantitative uncertainties concerning the effect of configurational pathway on pressure output, and the slope of the pressure-flow relation. For each of the above uncertainties we made certain assumptions based on indirect evidence but defined reasonable error limits. In the present communication we describe the method of implementing the model and evaluate the significance, in terms of spirometric output, of possible errors in the assumptions. Volume and flow profiles were generated from different neural output profiles. Analysis was repeated when the different assumptions were systematically altered within the limits set by the previous theoretical analysis. We conclude that the pattern of inspiratory muscle activation during spontaneous breathing and the existence of several mechanical interactions within the respiratory system combine to render spirometric output fairly insensitive to most potential errors in our assumptions.
Biomechanical Phenomena↗
A model for the relation between respiratory neural and mechanical outputs. III. Validation.
In the preceding two communications we described a model for the relation between respiratory neural and mechanical outputs. In the present report we test the accuracy of the model in predicting volume and flow from occlusion pressure wave forms, and vice versa. We performed single-breath airway occlusions in 21 unconscious subjects and determined the time course of occlusion pressure. We also measured the passive properties of the respiratory system. The time course of volume and flow was predicted from the occlusion pressure wave forms, and the results were compared with the spontaneous breaths immediately preceding occlusion. Inspiratory duration, shape and amplitude of occlusion-pressure wave forms, and the passive properties of the respiratory system varied widely among subjects. There was good agreement between predicted and observed values in all cases. Except for some prolongation of inspiration (Hering-Breuer reflex), diaphragmatic activity did not change during occlusion. Since occlusion pressure is proportional to inspiratory activity, we conclude that the model described provides a good approximation of the relation between inspiratory activity and spirometric output.
Adolescent↗