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Biomedical subjects

R Harper

Publications and source records attributed to R Harper.

At least 109 records · Page 6Linked to original sources
PubMed1981

Tolerance of the liver to ischemia: an experimental study.

The experiments described in this study challenge the 20th century belief that the liver is particularly vulnerable to deprivation of its blood supply for appreciable periods of time. The authors studied the effects of 60 minutes of normothermic hepatic ischemia on 10 pigs. The hepatic artery and its collateral vessels were occluded and portal blood was diverted by a portojugular shunt. This produced a 90% reduction in liver blood flow as determined by xenon-127 washout. None of the animals died of liver failure. The ischemic insult did not produce jaundice in any of the animals and only minimal transient changes in liver enzymes occurred. The results suggest that the liver is capable of withstanding prolonged periods of ischemia.

Alanine Transaminase↗
PubMed1981

Monitoring hearing loss at United Airlines.

The airlines are a highly diversified industry. Their major concerns are in the safe transportation of passengers and cargo with on time arrival and departure of its aircraft at various locations throughout the world. The challenge the airlines face is in the development and administration of an effective hearing conservation program that will produce valid audiometry at all of its logistic operations and yet be economically feasible and practical. The methods and techniques used by United Airlines to develop and administer an effective hearing conservation program are presented here. Guidelines employing the OSHA Noise Exposure Standard were incorporated in the program requirements as set forth by the medical department.

Aircraft↗
PubMed1980

Respiration during the first six months of life in normal infants. III. Computer identification of breathing pauses.

The first objective of this study was to quantify computer-identified breathing pauses in excess of two sec duration in relation to sleep states. The second objective was to examine which respiratory variables at one wk and one month of age predicted total apnea at 2 and 3 months of age. Short apnea (2 to 5 sec) were abundant in recordings of normal infants during the first one-half year of life. Apnea between 6 and 9 sec should be considered normal, whereas apnea in excess of 9 sec occurred most frequently in the first wk of life and declined sharply thereafter. Recording duration substantially affected apnea counts. Apnea at later ages could not be reliably predicted from recordings during the first wk of life.

Apnea↗
PubMed1979

Respiration during the first six months of life in normal infants: II. The emergence of a circadian pattern.

The objective of the present study was to investigate the emergence of circadian patterns in respiratory rates. Twenty-five neurologically normal infants were monitored for 12-hours during the first week of life and at one, two, three, four and six months of age. Each minute of the recordings of EEG, eye movements, somatic activity, respiration, ECG and temperature was coded into Active sleep (AS), Quiet sleep (QS), Indeterminate (IN) and Awake (AW). The night was divided into four equal intervals and a computer program calculated the mean respiratory rate for each interval as a function of state and age. During the first week of life group means of respiratory rates increased linearly with each interval in all states. A circadian pattern with lowered respiratory rates between 10:00 p.m. and 1:00 a.m. emerged at different ages in different sleep states. This pattern was first seen at one month of age in AS and IN, and at three months in QS. It was also observed in AW at three months of age, suggesting that the circadian rhythm is not solely an expression of the sleep wakefulness cycle. Feeding patterns contributed to but did not explain these observations.

Age Factors↗
PubMed1978

Acute myocardial infarction in women. The influence of age on complications and mortality.

The prognostic implications of a past history of ischaemic heart disease, site of infarction, ectopic ventricular dysrhythmias (ventricular premature beats (VPB) more than one in 10 sinus beats, and/or ventricular tachycardia (VT), ventricular fibrillation (VF), atrioventricular blocks (AVB), bundle branch blocks (BBB)) and the occurrence of electrical and/or mechanical complications during stay in the Coronary Care Unit (CCU) were analysed in 154 women with definte (WHO Class 1) acute myocardial infarction, admitted sequentially to the CCU over a four-year period. The prognosis in these women was then compared with the prognosis in a group which represented the general male population in the CCU and an age-matched group of men. The results showed that the long-term prognosis in women with acute myocardial infarction is remarkably similar to age-matched groups of men.

Acute Disease↗
PubMed1978

Effect on survival after myocardial infarction of long-term treatment with phenytoin.

A prospective, randomised, open trial was performed in 150 patients to test for any beneficial effects on 2-year mortality of long-term antiarrhythmic therapy with phenytoin in patients with acute myocardial infarction. Patients were stratified according to age, sex, past history of myocardial infarction, and the presence of absence of electrical or mechanical complications in the course of acute infarction. They were then randomised to treatment or control groups (74 v. 76). The former received phenytoin in doses aimed at maintaining plasma phenytoin levels between 40 and 80 mumol/litre. All patients entered the study before discharge from the coronary care ward. Plasma phenytoin levels were in the therapeutic range in between 51 and 75 per cent of subjects at any follow up visit. There were 19 withdrawals from the treatment group, 10 of which were the result of side effects. There were 5 withdrawals from the control group. According to the original intention to treat, there were 18 deaths at 2 years in the treatment group and 14 deaths in the control group. There was no reduction in the incidence of instantaneous or sudden deaths. Deaths on treatment were not associated with a low phenytoin plasma level. Phenytoin treatment showed no beneficial effects on mortality and was associated with a high incidence of side effects.

Adult↗
PubMed1977

Estimation of ventricular refractoriness in man by the extra stimulus method.

The effective right ventricular refractory (EVRP) period was estimated in 24 patients using the extra stimulus technique. All patients were paced from the right ventricle at basic pacing intervals of 400, 500, 600 and 800 ms, respectively. In all patients the EVRP decreased when the basic pacing rate was increased. At the same basic pacing rate there was a wide variation in the EVRP between individual patients. Within an individual patient, however, providing the position of the pacing electrode remained stable, there was no significant variation in the EVRP when estimations were performed 15-30 min apart. Thus the technique can be used to assess the effect of a drug on the EVRP in an individual patient.

Adult↗
PubMed1976

Wenckebach phenomenon in the exit area from a transvenous pacing electrode.

An unusual type of exist block from a transvenous pacing electrode was recorded in a 63-year-old man with an acute inferior infarct and cardiogenic shock. The pacemaker artefact to QRS interval increased gradually till there was loss of capture. A gradual change from I:I pacing rhythm to 4:3 and 3:2 Wenckebach cycles was recorded. This was followed by a fixed 2:I pacemaker artefact to QRS block.

Electrocardiography↗
PubMed1976

Inhibition of demand pacemakers caused by potentials associated with inspiration.

A 69-year-old man with a permanent demand pacemaker and a unipolar electrode system had intermittent failure of pacing during deep inspiration. Pacing was not interrupted when the unit was switched to fixed rate mode by an external magnet. Thus, the problem was not caused by a change in electrode position or to a loose connexion. The likely cause was inhibition by non-cardiac potentials, possibly myopotentials associated with respiration.

Aged↗
PubMed1976

Learning theory and gestalt therapy.

This article discusses the theory and operations of Gestalt Therapy from the viewpoint of learning theory. General comparative issues are elaborated as well as the concepts of introjection, retroflextion, confluence, and projection. Principles and techniques of Gestalt Therapy are discussed in terms of learning theory paradigm. Practical implications of the various Gestalt techniques are presented.

Attitude of Health Personnel↗
PubMed1975

Establishment of the Melbourne mobile intensive care service.

As the majority of deaths after infarction occur in the first hour, a mobile intensive care ambulance service has been instituted in Melbourne to enable adequate care and early monitoring facilities. Initially the service was manned by doctors and ambulance officers, but currently each ambulance is manned by two specially trained officers. Over a 27-month period 52 patients have been resuscitated from ventricular fibrillation or ventricular standstill. Half of the patients had sustained a definite acute myocardial infarction and another 16 had probable but not proven myocardial infarction. Of the 52 patients, 31 survived to leave hospital and all patients known to be alive are leading active and useful lives. In spite of an initial fear that medical treatment might be overused or misused by the officers, this has not been the case, and only about 13% of patients have received drugs from the officers. This paper deals with the setting up, staffing and training of the ambulance service and reviews its results.

Adult↗
PubMed1975

X-linked recessive progressive combined variable immunodeficiency (Duncan's disease).

Of 18 boys in Duncan kindred, 6 died of a lymphoproliferative disease. They exhibited a subtle, progressive combined variable immunodeficiency disease characterised by benign or malignant proliferation of lymphocytes, histiocytosis, and alterations in concentrations of serum-immunoglobulins. Infectious mononucleosis occurred during or preceding terminal events in at least 3 of the cousins. Fever, pharyngitis, lymphadenomegaly, hepatosplenomegaly, atypical lymphocytosis, and a spectrum ranging from agammaglobulinaemia to polyclonal hyper-gammaglobulinaemia occurred. At necropsy, the thymus gland and thymic-dependent areas in the lymph-nodes and spleen were depleted of lymphocytes. Diffuse infiltrates composed of lymphocytes, plasma cells, and histiocytes, some containing erythrocytes, invaded the haematopoietic organs, viscera, and central nervous system. In addition, 2 half-brothers had lymphomas of the ileum and central nervous system. Approximately half the boys, including the half-brothers, were affected, and girls were spared, implying sex-linked recessive inheritance. Various lymphohistiocytoses resemble Duncan's disease, but it is distinctive from them in the mode of inheritance or by histiological characteristics. This study suggests that the Epstein-Barr virus or other viruses triggered the fatal proliferation of lymphocytes and that progressive attrition of T-cell functions allowed uncontrolled lymphoproliferation.

Adult↗
PubMed1975

The effect of therapeutic doses of lidocaine hydrochloride on the effective refractory period of the right ventricle in man.

The effect of lidocaine on the effective refractory period of the right ventricle (EVRP) was measured in 10 patients using the extra stimulus technique of progressive introduction of premature stimuli until a response could not be elicited. In four patients lidocaine produced a significant decrease in the EVRP, in a further four patients there was no change, and in the remaining two patients lidocaine produced a significant increase in the EVRP. The effect of the drug on the EVRP could not be correlated with the serum potassium levels. The reasons for the variable effect of lidocaine are attributed to the different action of lidocaine on different components of conduction within the ventricle.

Adult↗
PubMed1975

His bundle electrogram in patients with acute myocardial infarction complicated by atrioventricular or intraventricular conduction disturbances.

Seventy-two patients with acute myocardial infarction complicated by atrioventricular or bundle-branch block or a combination of both had His bundle electrogram studies performed during their stay in the coronary care unit. In 19 of the 72 patients a repeat His bundle electrogram was performed before discharge from hospital. These studies demonstrated that 30 of the 32 patients with atrioventricular block and narrow QRS complexes had a block above the origin othe His spike (proximal block). Eleven patients in this group had repeat His bundle electrograms performed before discharge and in 3 patients there was evidence of residual atrioventricular nodal dysfunction. Both the hospital and follow-up mortality in this group was low and there was no evidence to suggest that permanent pacing would benefit these patients. Of the 18 patients with bundle-branch block and a normal PR interval, 9 had prolongation of the HV interval, but there was no difference in mortality in patients with normal or prolonged HV intervals. Twenty-two patients with bundle-branch block also developed atrioventricular block. In 5 of these patients the site of the AV block was proximal and in 14 it was distal, while 3 patients had both proximal and distal block. The hospital mortality in those patients who progressed to second- or third-degree atrioventricular block was considerably higher than in those patients who remained in first-degree atrioventricular block.

Acute Disease↗
PubMed1975

Syncope in association with Prinzmetal variant angina.

A case of Prinzmetal variant angina with transient complete atrioventricular block and syncopal episodes following an anteroseptal myocardial infarction is described. The syncopal attacks were not prevented by demand cardiac pacing and were presumably caused by transient severe ischaemia of the left ventricle, with a consequent reduction in cardiac output. The left ventriculogram showed a large anterior dyskinetic area corresponding to the high grade proximal obstruction in the left anterior descending artery demonstrated by coronary angiography. All other coronary vessels appeared free of disease and it is suggested that the anginal episodes were caused by transient proximal segmental spasm of the right coronary artery. The anginal episodes were successfully prevented by a regimen of two-hourly coronary arterial vasodilator therapy.

Angina Pectoris↗