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Biomedical subjects

R P Allen

Publications and source records attributed to R P Allen.

At least 55 records · Page 3Linked to original sources
PubMed1989

Absence of tolerance to the behavioral effects of methylphenidate in hyperactive and inattentive children.

To determine whether the behavioral benefits of methylphenidate in hyperactive and inattentive children decline during long-term treatment, we analyzed data from 108 hyperactive students who responded well to methylphenidate therapy for 3 to 10 years. Responders were identified by their consistent improvement from baseline on standard teacher rating scales. The therapeutically effective drug doses were corrected for body size and evaluated in relation to increasing age and treatment duration. Body size corrections included milligrams per kilogram, milligrams per kilogram to the 0.7th power, and milligrams per square meter of estimated body surface area. The major findings were that (1) the dose of methylphenidate, when adjusted for growth, did not change significantly during the 3 to 10 years of treatment; (2) the loss of a previously satisfactory response to methylphenidate treatment was uncommon (6%) and when present was related to middle school enrollment, male gender, noncompliance with medication, and lower than customary dosage; (3) the dose calculations that minimized the effects of growth with age were milligrams per kilogram to the 0.7th power and milligrams per square meter of estimated body surface area; and (4) the commonly used milligrams per kilogram dose consistently overcorrected for growth with advancing age.

Attention Deficit Disorder with Hyperactivity↗
PubMed1988

Nocturnal penile tumescence predicting response to intracorporeal pharmacological erection testing.

Although response to intracorporeal pharmacological erection testing has been proposed to determine the etiology of impotence, physiological criteria predicting this response have not been established and the literature includes conflicting results regarding which patients respond to pharmacological erection therapy. In this study 37 impotent patients underwent a diagnostic nocturnal penile tumescence evaluation (including measurements of rigidity, pulsations and bulboischiocavernosus muscle activity) and the results were correlated with subsequent response to intracorporeal pharmacological testing. Most but not all patients with psychogenic impotence and all with neurogenic impotence responded with good erections. For vasculogenic impotence response rate depended upon impairment severity determined from nocturnal penile tumescence measurements; none of the severe cases versus 90 per cent of the milder cases responded. The results indicate that response to intracorporeal pharmacological testing does not accurately distinguish psychogenic from organic impotence, is best for neurogenic impotence and worst for severe vasculogenic impotence, and can be predicted accurately by nocturnal penile tumescence measurements.

Adult↗
PubMed1988

Pressure controlled inverse ratio ventilation in severe adult respiratory failure.

Thirty-one patients with severe respiratory failure who were failing volume controlled conventional ratio ventilation were placed on pressure controlled inverse ratio ventilation (PC-IRV) for a total of 4,426 patient-hours. The PC-IRV resulted in a reduction of minute ventilation from 22 +/- 1.0 L/min (mean +/- SEM) to 15 +/- 0.7 L/min. Peak inspiratory pressure (PIP) was reduced from 66 +/- 2.3 cm H2O to 46 +/- 1.6 cm H2O and positive end expiratory pressures (PEEP) from 15 +/- 1.0 cm H2O to 2.5 +/- 0.5 cm H2O. Mean airway pressure increased from 30 +/- 1.7 cm H2O to 35 +/- 1.7 cm H2O. Oxygenation (PaO2) improved from 69 +/- 4.0 mm Hg to 80 +/- 4.5 mm Hg. The PaCO2 and arterial pH were not significantly changed. There were no significant changes in mean hemodynamic pressures. A lung compromise index (FIO2.PIP.10/PaO2) retrospectively distinguished between successful and unsuccessful PC-IRV episodes. These data suggest that PC-IRV can be successfully and safely implemented in critically ill patients with severe respiratory failure over prolonged periods of time resulting in significant improvement in oxygenation at lower minute volume, peak airway pressure and PEEP requirements.

Adolescent↗
PubMed1988

Locating and interviewing alcoholics 8 years after discharge from hospital.

An 8-year follow-up of 85 alcoholic men resulted in 93% interviewed or confirmed deceased. The location and interview techniques used to achieve this high completion rate are reported and the "location" of deceased subjects is discussed. A list of the agencies that might have information on the whereabouts of subjects is provided. The time course of data collection is analyzed. The characteristics of subjects lost under specific follow-up inadequacies or constraints are considered. Our findings can be used by program evaluators as a basis for decisions concerning the best use of their follow-up resources.

Adult↗
PubMed1987

Efficacy without tolerance or rebound insomnia for midazolam and temazepam after use for one to three months.

Midazolam (15 mg) was compared with temazepam (30 mg) in a randomized, double-blind, parallel group study. An initial screening period was followed by 3 days of placebo baseline, 4 to 12 weeks of nightly oral use of the medication and a 4-day placebo withdrawal period. One hundred seventy-five patients with chronic insomnia participated in this multicenter outpatient study. Because the elimination half-life of midazolam, a new trizolobenzodiazepine hypnotic, is short (1.3-2.2 hr) compared to temazepam's (12-16 hr), more problems with tolerance and rebound insomnia were expected to occur. Hypnotic efficacy (increased total sleep time, decreased wake time, and decreased sleep latency) was demonstrated for both medications over the entire 3-month period without the development of tolerance. In fact, if anything, efficacy increased with time on medication, suggesting possible facilitation or "inverse tolerance" effect. On withdrawal, sleep was improved compared with baseline, suggesting partial resolution of the insomniac condition rather than rebound insomnia. These effects were both statistically and clinically significant for midazolam, with 16% to 50% improvement in sleep measures. The results of this study suggest that patients with chronic insomnia may benefit from 30 to 90 days of treatment. A three-factor model that separates pharmacologic from behavioral and psychologic effects of hypnotics was proposed to explain these results in part.

Adolescent↗
PubMed1987

Emergency airway clot removal in acute hemorrhagic respiratory failure.

Three cases of respiratory failure and severe hypoxemia caused by blood clot obscuring the central airway are described. A technique to clear the airway using a no. 6 Fogarty balloon-tip embolectomy catheter inserted through a flexible fiberoptic bronchoscope was used in all three cases. Marked improvement and stabilization occurred while definitive therapy was undertaken.

Adult↗
PubMed1987

The characteristics of alcoholics frequently lost to follow-up.

In a follow-up of 85 alcoholic men, 93% were interviewed or confirmed deceased 8 years after discharge from hospital. The sample was also followed up at 1 and 3 years postdischarge. Follow-up rates of other published studies are discussed. Scales to assess difficulty of interview and difficulty of location were developed. Factor analysis revealed the differential characteristics of subjects defined as difficult to locate, difficult to interview or missing. Subjects who are difficult to locate, or who in the extreme case will go missing, tended to have poorer social functioning prior to intake and to be residentially unstable during the follow-up period, characteristics that tend to correlate with worse drinking outcome. Subjects who are unwilling to be interviewed tended to be residentially stable and show better interpersonal adjustment at follow-up. Less intensive location procedures would have resulted in data loss from those classified as difficult to locate. Less persuasive interview techniques would have resulted in data loss from those classified as difficult to interview. Early termination of the follow-up would also have resulted in data loss from the latter group. The distinct types of data biases that would be introduced by loss of information from each of the above subgroups are examined.

Adult↗
PubMed1986

Mortality and illness in male alcoholics: an 8-year follow-up.

An 8-year follow-up was conducted on a group of male alcoholics. Their mortality and illness records were examined. The number of observed deaths is 4.7 times that expected. The excess deaths appear to be due to causes frequently associated with alcoholism. Patient characteristics predictive of mortality are presented. Inpatient stays in general hospitals, for reasons other than alcoholism, totaled almost four times the duration expected. The relationships between drinking patterns and hospitalizations are studied. Clinical tests, which show improvement in response to abstinence, are suggested as positive reinforcers for patients in alcoholism treatment.

Adult↗
PubMed1983

Polysomnographic findings in dystonia musculorum deformans.

Twenty-five cases from the literature and four personal cases with dystonia musculorum deformans are described. The polysomnographic EEG findings of severely involved patients were characterized by over abundance of stage 2 sleep, with a characteristic pattern of spindle activity, increased latency to sleep, and reduced sleep efficiency. The similarities between these patients may underscore the importance of sleep spindles as a feature of the dystonia process and may be useful in the investigation of other basal ganglia disorders.

Adult↗
PubMed1983

The effects of protriptyline in sleep-disordered breathing.

The effects of therapy with the tricyclic antidepressant protriptyline were studied in 12 patients with hypersomnolence and moderately severe sleep apnea. After treatment there was no significant change in the duration or frequency of sleep-disordered breathing (SDB) during non-REM sleep, but there was an alteration in the breathing pattern characterized by a decrease in the amount of apnea during SDB events. Apnea, as a percent of disordered breathing time, fell from 60.4 +/- 27.2% to 35.5 +/- 26.7% (p less than 0.01) and was accompanied by a reduction in the peak fall in oxygen saturation from 16.2 +/- 6.2% to 9.2 +/- 4.7% (p less than 0.01). During REM sleep there was no change in the pattern, duration, or frequency of SDB, or reduction in the peak fall in oxygen saturation. However, there was a reduction in the amount of Stage REM sleep, thereby reducing the more severe SDB events (p less than 0.01) and further improving nocturnal oxygenation. In 10 of 12 patients, there was subjective improvement in daytime hypersomnolence, which was associated with an increase in median sleep onset time from 3.3 +/- 2.2 to 5.1 +/- 2.1 min (p less than 0.01). Although all patients developed mild side effects from the anticholinergic properties of protriptyline manifested by a dry mouth, 4 patients noted additional side effects including urinary hesitancy, mild constipation, and difficulty in maintaining an erection. One patient developed intolerable constipation that necessitated discontinuation of the drug. We conclude that protriptyline reduced daytime hypersomnolence and altered the pattern of SDB, thus improving gas exchange and oxygenation during sleep. Therefore, in selected patients with moderately severe obstructive sleep apnea, therapy with protriptyline is an alternative to surgical treatment with a tracheostomy.

Adult↗
PubMed1983

Computerized tomography in obstructive sleep apnea. Correlation of airway size with physiology during sleep and wakefulness.

Pathophysiologic changes during sleep in patients with obstructive apnea are often associated with alterations in upper airway function during awake periods. To determine whether these functional changes are related to abnormal airway structure, we performed computerized tomography (CT) in 20 awake patients with obstructive apnea and in 10 control subjects. The CT scan measurements of cross-sectional areas of the nasopharynx, oropharynx, and hypopharynx in apneic patients were significantly reduced (p less than 0.05) compared with those in the control subjects. Sites of obstruction varied, and apparent airway occlusion occurred in 6 patients. Reduced pharyngeal size correlated with increased sleep-disordered breathing rates (p less than 0.05), more severe nocturnal oxygen desaturation (p less than 0.05), and the presence of a saw-tooth pattern of flow-volume curves obtained during awake periods (p less than 0.05). Structural upper airway narrowing is detectable with CT in awake patients with obstructive sleep apnea.

Adult↗
PubMed1983

CT demonstration of pharyngeal narrowing in adult obstructive sleep apnea.

Sleep apnea is a major cause of daytime hypersomnolence. Among the proposed etiologies, focal obstruction of the airways at the level of the pharynx has been suggested but not proven. Using computed tomography, the cross-sectional area of the airway can be readily assessed. Thirty-three adults with clinically proven sleep apnea and 12 normal adults underwent systematic computed tomography of the neck. Significant airway narrowing was demonstrated in all the patients with obstructive sleep apnea, whereas no such narrowing was seen in the controls. In 11, the narrowing was at a single level, whereas in 22 patients two or more levels were affected. This study has shown that a structurally abnormal airway may serve as an anatomic substrate for the development of sleep apnea. On the basis of this evidence, uvulopalatopharyngoplasty has been performed in two patients with relief of symptoms in one.

Constriction, Pathologic↗
PubMed1981

Abnormal inspiratory flow-volume curves in patients with sleep-disordered breathing.

Although flow-volume curves are valuable in detecting extrathoracic airway obstruction, their role in testing patients with sleep-disordered breathing is undefined. To determine whether patients with sleep-disordered breathing have abnormal flow-volume curves consistent with variable extrathoracic obstruction, 60 subjects referred with suspected sleep disorders prospectively underwent spirometry and assessment of flow-volume curves. These tests were interpreted independent of the outcome of polysomnography. Fourteen of 35 subjects (40%) with sleep-disordered breathing had abnormal flow-volume curves consistent with variable extrathoracic airway obstruction, and 2 of 25 (8%) with no breathing disorder had extrathoracic obstruction (p less than 0.02). The presence of extrathoracic airway obstruction in subjects with mixed or obstructive sleep apnea did not correlate with age, the presence of snoring, excessive daytime hypersomnolence, obesity, or the severity of sleep apnea. Abnormal flow-volume curves were found more frequently in women who had no obvious structural upper airway abnormality. Because of the high specificity (92%) of the flow-volume curve, the finding of extrathoracic obstruction in patients with a history consistent with sleep-disordered breathing substantially increases the likelihood that sleep apnea is present.

Adult↗
PubMed1980

Effects of blunt cardiac trauma on coronary vasomotion, perfusion, myocardial mechanics, and metabolism.

Blunt injury to heart muscle can result in a variety of dysrhythmias and mechanical dysfunction. In the present studies of 24 open-chest, working swine hearts with controlled perfusion of the left anterior descending (LAD) coronary artery, changes in proximal and distal coronary vascular resistance (CVR), small-vessel perfusion (using radioactively-labeled microspheres), and regional and global mechanical function and metabolism (myocardial oxygen consumption [MVO2] and lactate extraction) were observed before and for 1 hour following a single impact involving the LAD artery. Trauma caused no spasm, thrombosis, hemorrhage, or laceration of the LAD artery but resulted in significant perfusion redistributions of small vessels. Within minutes of the impact, epicardial/endocadial flow ratios in the myocardial tissue perfused by the traumatized vessel increased (p < 0.005) and were associated with a significant decrease in the distal CVR (p < 0.001). In this same region, significant decreases were also observed in an index of regional work (p < 0.01), shortening (p < 0.005), MVO2 (p < 0.001), and per cent lactate extraction (p < 0.01). Also noted were declines in left ventricular (LV) pressure development and contractility (LV max dp/dt). The regional changes in flow patterns and function in general persisted throughout the course of perfusion. These data suggest that cardiac trauma can induce major changes in vasomotor tone and perfusion distributions of the coronary vasculature, and demonstrate how blunt cardiac-coronary trauma can result in some of the hemodynamic and electrocardiographic abnormalities previously reported.

Animals↗