Biomedical subjects

T Aasen

Publications and source records attributed to T Aasen.

10 recordsLinked to original sources

PubMed2000

Static stabilometry and repeated testing in a normal population.

BACKGROUND: The purpose of the present study was to see if there is a learning effect of repeated static stabilometric testing, using a protocol suitable for testing postural control in narrow spaces, like hypo- and hyperbaric chambers. HYPOTHESIS: Static stabilometry testing under normobaric conditions is objective and reproducible. With repeated testing, a learning effect may be observed. METHODS: Four groups of healthy individuals were tested ten times under the same four acoustically and visually standardized and normobaric normoxic test conditions on a static balance platform. First, the subjects were asked to stand on a bare platform with the eyes open, thereafter with the eyes closed. This was repeated with a foam rubber mat placed on top of the balance platform. The time interval between the first and the last test sequence was 11 (10-13) days for the test subjects in group I (n = 22), 17 d for group II (n = 13), 31(28-36) days for group III (n = 15) and 115 (49-193) days for group IV (n = 10). RESULTS: Static stabilometry tests in a normal population are objective and reproducible. With repeated tests, a learning effect was observed. The learning effect was largest when standing on a foam rubber mat with eyes closed and when the time intervals between the tests were shortest. There was no difference in sway pattern or learning ability between tall and short test subjects, between subjects with heavy and light body weight or between the sexes.

Adult↗

PubMed1998

Effects of hypobaric hypoxia on postural control.

BACKGROUND: While the effects of accelerative forces on the vestibular system have been thoroughly investigated, the effects of hypobaric conditions on the postural system have attracted less attention. The purpose of the study was to investigate if postural control is affected by hypobaric hypoxia. HYPOTHESIS: Moderate hypobaric hypoxia may reduce postural control. METHODS: Subjective and multiple objective measurements of postural control with open and closed eyes were made in 16 military aircrew standing on a static balance platform before, during, and after exposure to an altitude chamber training profile with a maximum altitude of 25,000 ft. RESULTS: No subjective dizziness and no clinical unsteadiness were noted. However, significant changes in body sway were found at the balance platform during hypobaric exposure at 18,000, 14,000 and 8000 ft compared with the baseline registrations. The relative increase in sway movements was greater in the eyes open condition compared with the eyes closed condition, and significant for movements in the anteroposterior plane but not in the lateral plane. Most sway parameters returned to pre-exposure values on return to ground level. CONCLUSIONS: Acute hypobaric hypoxia, corresponding to the tested altitudes, influenced postural control primarily in the anteroposterior plane with eyes open. This is in agreement with other studies showing that vision is the first of the special senses to be altered by lack of oxygen.

Adult↗

PubMed1997

Procedure for estimating the correlation dimension of optokinetic nystagmus signals.

In this study, optokinetic nystagmus (OKN) is hypothesized to be controlled by a low-dimensional deterministic and possibly chaotic generator. A procedure for quantifying the presumably low-dimensional structure of the OKN signal, based on the Singular Spectrum Approach and the Grassberger--Procaccia algorithm for estimating the correlation dimension, v, is described. The procedure developed showed robustness against noise. Applying this method to OKN signals from 10 healthy subjects and 10 patients suffering from vertigo showed a statistically significant lower mean v value for the patients.

Adult↗

PubMed1997

[Chaos theory and otoneurologic diagnosis].

Current interpretation of signals obtained from ENG (electronystagmography) of patients suffering from vertigo is based on methods developed before computers became standard laboratory equipment. New signal processing methods, based on the use of fast computers, can increase our knowledge of the mechanisms involved in the regulation of the vestibular system. Preliminary results suggests that new analyzing tools from the field of chaos theory may yield information of clinical relevance. At present this would appear to be a promising approach to research in this field.

Humans↗

PubMed1995

Balance testing in saturation diving.

UNLABELLED: The literature is sparse and equivocal concerning the possible influence of hyperbaric exposure on postural control and the vestibular system. HYPOTHESIS: Deep heliox diving may influence postural control and the vestibular system. METHOD: Multiple objective measurements of postural control were made in four divers by means of a static balance platform before, during and after an onshore experimental saturation heliox chamber dive of 32 d duration. Saturation pressure was 4.6 MPa, corresponding to a depth of 450 m of seawater (msw). Downward excursions to 470 msw were also performed. Clinical ENT and otoneurological examination, including bithermal caloric vestibular testing with electronystagmography (ENG) was performed before and after the dive. RESULTS: Reduced postural control was detected by the balance platform test in all four divers from approximately 200 msw and deeper. Body sway showed a distinct increase during compression, reaching a maximum value during the bottom phase. The Romberg index was not suitable for describing shifts in postural stability. All sway parameters returned to pre-dive values after surfacing. Immediately post-dive, most caloric responses were reduced, compared to the pre-dive results. CONCLUSION: We conclude that deep heliox diving influences postural control and the vestibular system. Computerized stabilometry is a convenient and sensitive method of monitoring postural control during saturation diving. The path length of the center of pressure (COP) seems to be suitable as a monitoring parameter.

Adult↗

PubMed1993

Chaos theory applied to the caloric response of the vestibular system.

Developments in the field of nonlinear dynamics has given us a new conceptual framework for understanding the mechanisms involved in the regulation of complex nonlinear systems. This concept, called "chaos" or "deterministic chaos," has been applied to EKG, EEG, and other physiological signals, but not yet to the ENG signal. The underlying geometrical structure in chaotic dynamics is fractal (noninteger dimension), and calculating the fractal dimension of the electronystagmographic recording from caloric testing gave a dimension ranging from 3.3 to 7.7. This result demonstrates that the multidimensional vestibular system, with its numerous neurological pathways, can somehow reduce the degrees of freedom and give rise to an irregular dynamic low-dimensional behavior, which is associated with deterministic chaos.

Caloric Tests↗

PubMed1988

Non-caseating granulomas in patients with hematologic malignancies. A report of three cases.

Sarcoidosis or sarcoid-like lesions occurred in three patients with hematologic malignancies. In one patient, an overlap syndrome sarcoidosis/polycythemia vera was the most probable diagnosis. In the other two cases, the granulomas were probably secondary to myelofibrosis and Waldenström's disease, respectively. Recent epidemiological studies have failed to show a causal relationship between sarcoidosis and malignancy. The co-existence of sarcoidosis and malignancy is probably fortuitous, but non-caseating granulomas may occur secondary to malignant diseases.

Aged↗

PubMed1986

Smoking and giving of patient information by chest physicians.

A survey of the 115 members of the Norwegian Thoracic Society with a response rate of 94% yielded 17% smokers. Almost half of the smokers were cigar smokers only. Smoking was less prevalent among the younger physicians. All 83 physicians who answered the questionnaire recorded the smoking habits of their patients, and 99% of the doctors gave information to patients on the health hazards of smoking. However, only 22% of the physicians devoted more than 5 min to this work at each consultation. Physicians who were ex-smokers repeated questions on smoking habits and more often gave patients advice on drug treatment than non-smoking physicians.

Humans↗

PubMed1982

Efficacy of oral acyclovir in the treatment of initial and recurrent genital herpes.

A double-blind, randomised trial of acyclovir versus placebo was conducted in 31 patients with initial and 85 patients with recurrent genital herpes. 17 patients with initial and 42 with recurrent disease were treated with 200 mg acyclovir by mouth five times a day for 5 days, and the remaining patients received matching placebo. In patients with initial genital herpes shedding virus acyclovir significantly reduced the duration of viral shedding, itching, and pain, the time to crusting and complete healing, and new lesion formation compared with controls. In patients with recurrence disease acyclovir significantly reduced the duration of viral shedding, time to complete healing, and new lesion formation. The reported incidence of adverse events was similar in both acyclovir and placebo groups. Oral acyclovir is effective and well tolerated in patients with initial and recurrent genital herpes and can be used in outpatient therapy.

Acyclovir↗

PubMedDate not supplied

Symbolic dynamics applied to optokinetic nystagmus signals.

In this study symbolic dynamics is used to analyse the time evolution of the optokinetic nystagmus (OKN). The inter-saccadic nystagmus differences are transformed into a sequence of three equally numbered letters (symbols) which represents the temporal changes in the inter-saccadic signal: (a) a fall in the temporal change, (b) no changes and (c) a rise in temporal change. The complexity of the data series was then calculated as the entropy of the word length three probability distribution of the symbol sequence. The method was applied to OKN signals from ten healthy subjects and ten patients suffering from vertigo (four tests on each subject) and to 40 artificial white noise data series of the same length as the symbolic representation of the OKN data. Applying Student's t-test showed a statistically significant lower mean entropy value (p<0.05) for the patients.

Adult↗