Partnering for optimal respiratory home care: physicians working with respiratory therapists to optimally meet respiratory home care needs.

The need for respiratory care services continues to increase, reimbursement for those services has decreased, and cost-containment measures have increased the frequency of home health care. Respiratory therapists are well qualified to provide home respiratory care, reduce misallocation of respiratory services, assess patient respiratory status, identify problems and needs, evaluate the effect of the home setting, educate the patient on proper equipment use, monitor patient response to and complications of therapy, monitor equipment functioning, monitor for appropriate infection control procedures, make recommendations for changes to therapy regimen, and adjust therapy under the direction of the physician. Teamwork benefits all parties and offers cost and time savings, improved data collection and communication, higher job satisfaction, and better patient monitoring, education, and quality of life. Respiratory therapists are positioned to optimize treatment efficacy, maximize patient compliance, and minimize hospitalizations among patients receiving respiratory home care.

Comparison of six oxygen delivery systems for COPD patients at rest and during exercise.

Five different oxygen-conserving devices were tested in each of ten oxygen-dependent patients with COPD who had met the NOTT criteria for continuous oxygen use. They were tested on room air, their prescribed continuous oxygen flow and then on each of the five devices. The devices which delivered a bolus of oxygen during early inspiration or increased oxygen delivery as the respiratory rate increased did better than those devices which delivered oxygen at a normal flow rate during inspiration or a fixed portion of inspiration. In at least one of the subjects each device was associated with desaturation to less than 80 percent during a 12-min walk. It is concluded that oxygen-conserving devices vary in their ability to maintain SaO2 levels during exercise. It is recommended that a home oxygen evaluation include measurement of an exercise SaO2 utilizing the prescribed oxygen delivery system.

Excitatory amino acids and rod photoreceptor disc shedding: analysis using specific agonists.

L-Glutamate and L-aspartate stimulate photoreceptor disc shedding. In order to evaluate the possible involvement of a receptor, we examined the effects of specific excitatory amino acid agonists on rod photoreceptor disc shedding and neural retinal toxicity. Using eyecups from both Xenopus laevis and Rana pipiens, we found that kainate, quisqualate, and N-methyl-D-aspartate (NMDA) were all neurotoxic, but that kainate caused a more extensive inner retinal lesion. Kainate also caused disc shedding at concentrations as low as 10 microM; dihydrokainate, a structural analogue, was at least 100-fold less potent. In contrast, quisqualate induced disc shedding only at concentrations above 5.0 mM, and NMDA had no effect on disc shedding at any concentration examined. Our results suggest that excitatory amino acids act via a receptor of the kainate type to effect disc shedding. The mechanism in the retina or photoreceptor-pigment epithelial complex by which an excitatory amino acid receptor system influences disc shedding remains to be identified.

Effects of kynurenate and other excitatory amino acid antagonists as blockers of light- and kainate-induced retinal rod photoreceptor disc shedding.

Photoreceptor disc shedding in the retina involves detachment of discs from distal outer segments and phagocytosis of those discs by adjacent pigment epithelial cells. The disc-shedding process balances the continuous renewal of photosensitive membrane. In amphibians, rod disc shedding normally is light-stimulated. However, excitatory amino acids such as kainate stimulate disc shedding independent of a dark-light transition. Excitatory amino acid-induced disc shedding is accompanied by toxic changes within the retina. To evaluate the possible role of an endogenous excitatory amino acid in the regulation of light-evoked disc shedding, we examined the effects of excitatory amino acid antagonists on kainate-induced and light-evoked disc shedding and on retinal toxicity. Using eyecups from Rana pipiens, we found that kynurenate, D-O-phosphoserine, and cis-2,3-piperidine dicarboxylic acid (cis-PDA) all block both the neurotoxic and disc-shedding effects of kainate. Kynurenate and D-O-phosphoserine, but not cis-PDA, also block light-evoked disc shedding. Our analysis suggests that kynurenate blocks the mechanism by which light "triggers" disc shedding rather than directly inhibiting disc detachment and phagocytosis. The observation that cis-PDA antagonizes the effects of kainate, but not light, suggests that the receptor mediating the kainate effect on disc shedding may not be involved in the normal initiation of the response by light. In contrast, our data on kynurenate suggest that it antagonizes an endogenous mechanism involved in the normal control of disc shedding. Thus, analysis of the differences between cis-PDA and kynurenate as antagonists in the retina may yield important insight into the mechanism by which light initiates disc shedding.

Light-evoked and kainic-acid-induced disc shedding by rod photoreceptors: differential sensitivity to extracellular calcium.

In order to study the light and Ca2+ dependence of disc shedding by rod photoreceptors, we have used eyecups prepared from adult Rana pipiens frogs that had been kept in constant light for 4 days. Disc shedding was initiated by a treatment involving 1 hour of darkness followed by exposure to light or by treatment with kainic acid. Maximal L-evoked disc shedding occurred quickly (within 30-60 minutes) after light onset and could be triggered by brief (15 minutes) exposure to light. L-evoked disc shedding was completely blocked by omission of Ca2+ from culture medium or by treatment with 3mM Co2+ or 12 mM Mg2+ in the presence of Ca2+ (2 mM). The response was also blocked by the organic Ca2+ antagonist nifedipine. Experiments designed to distinguish between Ca2+ dependence of the dark- or light-dependent processes necessary for shedding suggest that voltage-sensitive channels mediate a Ca2+-dependent process involved in light-triggering. Kainic acid caused a dose-dependent stimulation of disc shedding under lighting conditions (continuous culture in light or darkness) that did not normally result in a significant response in the absence of the drug. Disc shedding induced by kainic acid was similar in time course and magnitude to that induced by light. However, kainic-acid-induced disc shedding was not inhibited by medium Ca2+ reduction or by the presence of Co2+. The latter observation suggests that kainic acid activates disc shedding directly, by-passing the Ca2+-dependent process involved in the L-evoked response. The Ca2+-dependent process may involve release of an effector of disc shedding that is mimicked by kainic acid.

An EEG study of visual attention in schizophrenic patients and normal controls.

This is a series of experiments examining the EEG, both at rest and in response to visual stimuli of varied complexity, in schizophrenics and normal controls. Subjects attended on several occasions. The resting EEG of patients was more activated than that of normals on all sessions, although only the patients showed diminished activation as a function of visits. The EEG of normals responded systematically on all occasions, but the patients showed similar response only under conditions of instructional set prescribing active stimulus appraisal. For both groups, subsequent stimulus recognition scores were correlated positively with EEG discrimination of stimuli during inspection. Within the patient group, several measures of pathology correlated both with recognition performance and several EEG parameters. Thus the present study draws together data demonstrating attentional deficit, heightened arousal, and reduced cortical variability in schizophrenics. Attention is drawn to methodological difficulties inherent in this type of study.

EEG correlates of eye contact and interpersonal distance.

The EEG of 18 male subjects was monitored while the subject gazed at the eyes of a male experimenter located 2, 4, 8, 16 or 32 ft from the subject. The experimenter either gazed directly at the subject or averted his eyes. EEG arousal was highest when the experimenter was at 2 ft and gazing into the subject's eyes. EEG arousal diminished as a function of distance, while arousal for direct gaze was always higher than for averted gaze, whatever the distance.

Stimulus complexity, EEG abundance gradients, and detection efficiency in a visual recognition task.

Occipital EEG was monitored while subjects inspected 27 projected patterns. The number (N) and variety (V) of elements in the patterns were varied systematically. There were three levels of N (6, 12 or 24 elements) and three levels of V (circles, squares or hexagons occupying all, one half or one third of the element locations for all levels of N). Subjects were instructed that they would be required in a post-test to recognize the patterns, among patterns which had not appeared; they were also informed that the patterns had been constructed according to a set of simple rules, but the nature of these rules was not made fully explicit. The EEG was quantified by means of low-frequency analysis, yielding measures of abundance (theta, alpha and beta) and mean dominant frequency. For the recognition task, nine stimulus items were embedded among 45 items. Recognition efficiency was measured by means of the signal detection theory discrimination index (d'). The results were as follows: (i) Both N and V were inversely related to alpha abundance (P less than 0-01); (ii) the strongest relationship between stimulus parameters and the EEG held for N and EEG beta activity (13-5-19-5 Hz;P less than 0-001), where again the EEG and N were inversely related; (iii) there was a significant (P less than 0-05) direct relationship between N and theta activity; (iv) contrary to prediction, mean dominant alpha frequency decreased as N increased; (v) d' correlated significantly with a number of effects for N, i.e. subjects who exhibited greatest EEG discriminability of items during exposure of the patterns, subsequently obtained the higher detection scores in the recognition task. The work described therefore demonstrates that only only do stimulus parameters have systematic effects upon brain activity as measured by the EEG, but that such effects have functional value and reflect aspects of efficiency. The results are fully compatible with arousal theory constructs relating physiological reactivity and performance.