Biomedical subjects

J Hellgren

Publications and source records attributed to J Hellgren.

17 recordsLinked to original sources

PubMed2002

Increased nasal mucosal swelling in subjects with asthma.

OBJECTIVE: The objective of this study was to evaluate nasal mucosal swelling with acoustic rhinometry in subjects with asthma and in healthy controls. METHODS: We examined 184 individuals with asthma and compared with 156 randomly selected controls outside the pollen season, where 144 subjects in the asthma group and 80 controls had a previous history of non-infectious rhinitis (NIR). Nasal mucosal swelling was assessed with acoustic rhinometry before and after nasal decongestion with oxymetazoline and was analysed for the crosssectional area (4cm from the nostril) and the volume between 3.3 and 4cm from the nostril. Symptom scores for nasal blockage, secretion, itching and sneezing were assessed on a 0-10 visual analogue scale as well as peak nasal inspiratory flow and spirometry. RESULTS: Before decongestion there was a decrease in the cross-sectional area at 4 cm (1.32 cm2 vs. 1.59 cm2, mean left + right P = 0.04) and in the volume (1.70 vs. 1.91 cm3 P = 0.03) in the asthma group compared with healthy controls. After decongestion there were no significant differences in cross-sectional area at 4cm (1.66 vs. 1.73cm2 P=0.32) or volume (2.12 vs. 2.24cm3 P=0.32). Combined nasal symptom scores were higher in the asthma group (1.8 vs. 0.8, P=0.0001) and peak nasal inspiratory flow was lower (119 vs. 124 L/min, P = 0.38) than the healthy controls. FEV1 (% predicted) was also lower in asthma group (84 vs. 93% P < 0.0001). CONCLUSION: We have been able to demonstrate an increased nasal mucosal swelling in a population sample of persons with asthma compared to healthy controls. These data support previous reports of a generalized airway inflammation in patients with asthma and suggest that acoustic rhinometry can be used to monitor the nasal mucosal swelling in these patients.

Adult↗

PubMed2002

Rhinitis increase the risk for adult-onset asthma--a Swedish population-based case-control study (MAP-study).

The aim of the study was to examine certain predictors, especially non-infectious rhinitis, and the risk for adult-onset asthma. A nested case-control study of adult-onset asthma was performed in a random sample from the general population (n = 15,813), aged 21 to 51 years. Cases for the study included subjects reporting physician-diagnosed asthma (n = 235) and controls (n = 2044) were randomly selected from the whole population sample. The case-control sample was investigated with a comprehensive respiratory questionnaire. Odds ratios were calculated stratified for sex, year of diagnosis and birth-year. Adult-onset physician-diagnosed asthma was associated with occurrence of non-infectious rhinitis before asthma onset (OR = 5.4, 95% CI 4.0-7.2), especially among smoking non-atopics (OR = 9.1, 95% CI 5.3-15.4). Smoking before asthma onset increased the risk for asthma (OR = 1.5, 95% CI 1.1-2.1). In conclusion, this population-based case-control study indicate that non-infectious rhinitis and current smoking, especially among non-atopics, are associated with increased risk for adult-onset asthma.

Adult↗

PubMed2001

Nasal symptoms among workers exposed to soft paper dust.

OBJECTIVES: To clarify whether occupational exposure to paper-dust is associated with an increased risk of non-infectious rhinitis. METHODS: Thirty-seven workers exposed to paper-dust in a soft-paper mill were compared with 36 unexposed controls. The study was performed under normal working conditions during the non-pollen season. Medical and occupational history was taken down in a comprehensive questionnaire and nasal symptoms were scored on a visual analogue scale (VAS). Pulmonary and nasal function was assessed by spirometry, acoustic rhinometry and peak nasal inspiratory flow. Nasal lavage was analysed for interleukin-8 (IL-8) and nasal transit time was monitored with the saccharine test. Concentrations of inhalable dust for each exposed subject during the day of the clinical study were measured with personal sampling devices. RESULTS: There was an increased prevalence of nasal blockage and crust formation among the exposed workers. However, there was no difference with regard to acoustic rhinometry, nasal transit time or nasal peak inspiratory flow. In the whole population, IL-8 in nasal lavage was higher among men than among women, 193 ng/l vs 132 ng/l, P = 0.006. There was also a positive trend (P = 0.01) with increasing nasal IL-8 going from non-smokers (122 ng/l), ex-smokers (126 ng/l) to current smokers (235 ng/l). CONCLUSIONS: We have found that occupational exposure to paper-dust is associated with symptoms of nasal blockage and nasal crusting. We find no objective signs of nasal inflammation, even among the subgroup with the highest current exposure.

Adult↗

PubMed1999

System identification of feedback in hearing aids.

The feedback problems of behind the ear (BTE), in the ear (ITE), and in the ear canal (ITEC) hearing aid categories have been investigated. All possible feedback paths (acoustical via vent, via tubing wall, mechanical, etc.) were converted to a single transfer function from the ear canal to the hearing aid microphone, here called the acoustic feedback equivalent (AFE). The attenuation of the AFE represents the maximum gain that can be used without the hearing aid starting to howl. Magnitude and phase responses of the AFE were identified on ten human subjects and on a Knowles ear manikin (KEMAR). The acoustic feedback via vent and leak between earmould and ear canal dominated the AFE. The transfer function from a reference point under the ear to the position of microphone of the different hearing aid categories was identified and used together with the AFE to calculate the maximum real ear aided gain (REAG) for the hearing aid categories. A model of the AFE, consisting of a fourth-order filter together with a delay, showed good agreement with the measured data.

Ear Canal↗

PubMed1999

Variations in the feedback of hearing aids.

Variations in the loop response of hearing aids caused by jaw movements, variations in acoustics outside the ear, and variations of vent size have been identified. Behind The Ear (BTE) and In The Ear Canal (ITEC) hearing aids were considered. The largest variations among the variations of the acoustics outside the ear, except when the hearing aid was partly removed, were found with the ITEC when a telephone set was placed by the ear. The variations of the loop response caused by changes in vent size were compared with the variations of a theoretical model of the feedback path. The theoretical model was also used to compare the feedback of different designs of the vent that gives the same acoustic impedance at low frequencies. The calculated feedback was less with the short vents (12 mm) than the long vents (24 mm).

Acoustics↗

PubMed1998

Clinical trial of a digital hearing aid.

A clinical trial of Oticon DigiFocus hearing aid was performed. The test aid was evaluated on 33 subjects with several years' experience as users of modern analog hearing aids. These aids were used as reference for the 1-month-long trial. The Abbreviated Profile of Hearing Aid Benefit (APHAB) showed a mean difference in benefit with superior ratings for the test aid concerning ease of communication, speech in reverberation and speech in background noise. The subjects' own aids were rated somewhat better concerning aversiveness of sounds, but this difference was not statistically significant. The Gothenburg Profile showed a statistically significant difference between the test aid and the reference aids in favour of the test aid. The difference was not most evident with regard to speech communication and the effects of hearing loss on social interactions. Sound quality ratings concerning clearness were significantly higher for the test aid. Speech recognition thresholds in noise were on average 0.7 dB better for the test aids when tested at speech levels 60 and 75 dB. The difference was statistically significant only at 75 dB. There was significant interaction between general preference and hearing aid type, indicating that overall sound quality was an important factor affecting the general preference for either the test aid or the reference aid. Twenty-three subjects generally preferred the test aid, six preferred their own aid and four stated no difference.

Adult↗

PubMed1998

Non-linear signal processing in digital hearing aids.

Three different non-linear digital signal processing algorithms were developed; LinEar, DynEar and RangeEar. All three provided individual frequency shaping via a seven-band low-power filterbank and compression in two channels. RangeEar and DynEar used wide dynamic range syllabic compression in the low-frequency (LF) channel, while LinEar used compression limiting. In the high-frequency (HF) channel, RangeEar used a slow-acting automatic volume control, while DynEar and LinEar used compression limiting. Wearable digital signal processing-based experimental instruments were used to evaluate the fitting algorithms under real world conditions with experienced hearing aid users. Evaluation included laboratory testing of speech recognition in noise and questionnaires on sound quality ratings. Results did not indicate one general good-for-all algorithm, but different algorithms resulting in preference and performance depending on the hearing loss configuration. Preference for any of the new algorithms could be predicted based on auditory dynamic range measurements. It was hypothesized that the different preferences were affected by different susceptibility to masking of HF sounds by amplified LF sounds.

Adult↗

PubMed1998

Nasal nitric oxide and its relationship to nasal symptoms, smoking and nasal nitrate.

Nitric oxide (NO) is produced in the nasal mucosa and in the paranasal sinuses. Increased nasal NO concentrations have been found in patients with asthma and/or rhinitis, and nasal NO has been suggested to be a marker of nasal inflammation. Measuring the stable end products of NO, nitrate and nitrite in nasal lavage fluid have been proposed as an indirect method for measuring NO concentration. The aim of this study was to measure nasal NO concentration, and to find out its relationship to nasal nitrate concentration and clinical parameters. 73 paper-mill workers were investigated with nasal and exhaled NO, nitrate in nasal lavage fluid and were given a respiratory questionnaire. Nasal air was sampled directly from a nasal mask and NO concentration was measured with a chemiluminescence analyser. Exhaled NO was measured with the subjects breathing tidal volumes and wearing nose clips. The nitric oxide metabolites were analysed as nitrate, after reduction of nitrite to nitrate. Smokers had lower nasal NO concentration (264 ppb) as compared to NO concentrations of 340 ppb among non-smokers (p = 0.02). There was no statistically significant relationship between nasal NO concentration and nitrate in nasal lavage fluid or nasal symptoms. Nasal NO concentration was significantly related to FVC (p = 0.047) and there was a relationship with borderline statistical significance (p = 0.06) to FEV1. In conclusion, we found no relationship between nitrate in nasal lavage and nasal NO, and neither of these were correlated to nasal symptoms or to nasal PIF. Nasal NO was significantly lower among smokers. Further controlled studies on subjects with rhinitis are needed, to evaluate the relation between nasal NO and nasal inflammation. In addition, there is also a need to develop methods for measuring nasal NO that minimise contamination from sinuses.

Adult↗

PubMed1997

A study of some current methods for assessment of nasal histamine reactivity.

The aim of this study was to investigate the reactivity of the nasal mucosa of patients with pollen allergy compared to healthy controls, when challenged with histamine outside the pollen season. Assessments were made with symptom score, acoustic rhinometry, nasal peak expiratory and inspiratory flow (NPEF and NPIF) and rhinomanometry in order to find the most sensitive method for the purpose. Twenty-one patients with seasonal allergic rhinitis and 20 healthy controls were challenged with histamine dihydrochloride in increasing concentrations (0.01, 0.1, 1.0 mg/ml) locally in the nose. Our results show no difference in mucosal reactivity between the patients and controls regardless of the method used. When comparing the methods we find that NPIF and NPEF are more sensitive to mucosal changes than the other methods we have studied.

Adult↗

PubMed1997

A digital filterbank hearing aid: predicting user preference and performance for two signal processing algorithms.

OBJECTIVE: In a series of experiments with a wearable binaural digital hearing aid, two hearing aid processing algorithms were compared. Both algorithms provided individual frequency shaping via a seven-band filterbank with compression limiting in the high-frequency channel. They differed in the processing of the low-frequency channel, using dynamic range compression for one (DynEar) and linear processing with compression limiting for the other (LinEar). In a pilot field test we found that LinEar/ DynEar preference based on use time could be predicted from auditory dynamic range data. For the subjects who preferred DynEar, the mean dynamic range was broader for low and mid frequencies and narrower for high frequencies, as compared with the LinEar preference subjects. These groupings were tested as predictors of user preference and performance in a main field test. DESIGN: The main study included 26 hearing aid users with symmetrical sensorineural losses. The algorithms were compared in a one-mo-long blind field test. A data logger function was included for objective recording of the total time each algorithm was used and how the volume controls were used. The preference was based on the time used for each algorithm and on subjective statements. Threshold signal-to-noise ratio (S/N-threshold) for speech was tested, and sound quality ratings were obtained through a questionnaire. We also tested the S/N-thresholds for the subjects' conventional (own) aids. RESULTS: The preference was correctly predicted by the dynamic range data on 12 out of 15 new cases. S/N-thresholds were lower for the preferred fittings compared with the nonpreferred fittings and with the subjects' own aids. In the questionnaire the preferred fittings were rated significantly higher in terms of overall impression and clearness. Because of the systematic way the DynEar-preference subjects adjusted the high-frequency DynEar gain, we speculate that upward spread of masking may have been a factor in preference and performance. Additionally, LinEar-preference subjects' preference and performance might have been influenced by excessive compression ratios with the DynEar processing in these cases. CONCLUSIONS: 1. Preference for DynEar versus LinEar depends on the auditory dynamic range. 2. S/N-thresholds for speech were better for the preferred fittings, which also were rated higher in terms of overall impression of sound quality and clearness.

Adult↗

PubMed1997

A digital filterbank hearing aid: three digital signal processing algorithms--user preference and performance.

OBJECTIVE: Three digital signal processing algorithms named RangeEar, DynEar, and LinEar were compared with regard to user preference and performance when a wearable digital filterbank hearing aid was used. All three algorithms provided individual frequency shaping via a seven-band filterbank. Compression was used in a low-frequency (LF) and a high-frequency (HF) channel. RangeEar and DynEar used wide dynamic range syllabic compression in the LF channel, whereas LinEar used compression limiting. In the HF channel, RangeEar used a slow acting automatic volume control, whereas DynEar and LinEar used compression limiting. The subjects had access to a manual volume control when using the LinEar or DynEar options. DESIGN: The study included 13 hearing aid users with symmetrical sensorineural losses. In a 1 mo long blind field test, the RangeEar algorithm was compared with the preferred algorithm from an earlier study, DynEar or LinEar. A data logger function was included for objective recording of the total time each algorithm was used and how the volume controls were used. The preference was based on the time used for each algorithm and from subjective statements. Threshold signal-to-noise ratio (S/N-threshold) for speech was tested, and sound quality ratings were obtained through a questionnaire. RESULTS: Of the 13 subjects, six preferred the RangeEar fitting and another four preferred the DynEar fitting. Two subjects preferred the LinEar fitting and one had equal preference for RangeEar and LinEar. The results from the questionnaire showed that the preferred fittings were rated higher concerning overall impression of sound quality and clearness, whereas the S/N for the speech test did not show any differences. Preferences, where stated, could be predicted from auditory dynamic range measurements in the LF and HF frequency ranges. The mean dynamic range was broader for low and narrower for high frequencies for those who preferred the RangeEar or DynEar fitting as compared with those who preferred the LinEar fitting. The preference between RangeEar and DynEar was predicted by differences in the HF range, with the narrower dynamic range for the DynEar preference subjects. CONCLUSION: Most subjects preferred the option of having a wide dynamic range syllabic compressor in the LF channel and having the overall gain in the HF channel adjustable, either manually (DynEar) or automatically (RangeEar).

Adult↗

PubMed1997

A digital filterbank hearing aid. Improving a prescriptive fitting with subjective adjustments.

Two fitting algorithms for linear hearing aids were compared using a wearable digital hearing aid in a one-month blind field test: a prescriptive method (POGO II) and a new algorithm, LinEar. Both used seven bands for frequency shaping, and two channel compression limiting. When fitting LinEar, the subjects individually adjusted the frequency response according to specified criteria. LinEar used a lower compression threshold setting than prescribed by POGO II. Eight subjects tested the two algorithms in a one-months blind field test as well as in the laboratory. The individual LF- and HF-gain adjustments of the frequency response in LinEar showed rather large variations compared to the POGO II prescription. Measures of S/N for speech did not show any significant differences between LinEar and POGO II, while overall sound quality ratings in laboratory and field test showed that LinEar was rated significantly higher than POGO II.

Adult↗

PubMed1995

The action of 5-HT on calcium-dependent potassium channels and on the spinal locomotor network in lamprey is mediated by 5-HT1A-like receptors.

5-HT has a powerful modulatory action on the firing properties of single neurons as well as on locomotor activity. In lamprey, 5-HT increases the neuronal firing frequency in spinal neurons by reducing the conductance in Ca(2+)-dependent K+ channels (KCa) underlying the slow afterhyperpolarization (sAHP), and it also lowers the burst frequency of the spinal locomotor network. To elucidate which type of 5-HT receptor mediates these effects, different specific receptor agonists and antagonists were applied during intracellular current clamp recordings and during NMDA-induced fictive locomotion in the lamprey spinal cord in vitro preparation. The 5-HT1A receptor agonist 8-OH-DPAT ((+/-)-8-hydroxy-dipropylaminotetralin hydrobromide), the 5-HT1 receptor agonist 5-CT (5-carboxyamidotryptamine maleate) and the 5-HT2 receptor agonist alpha-CH3-5-HT (alpha-methylserotonin maleate) all reproduced the actions of 5-HT at both the cellular and the network levels. The effects of all agonists were completely or partially blocked by the 5-HT1A and 5-HT2 receptor antagonist spiperone (spiroperidol hydrochloride) while selective 5-HT2 receptor antagonists were ineffective. The selective 5-HT1A receptor antagonist S(-)-UH301 (S(-)-5-fluoro-8-hydroxy-dipropylaminotetralin hydrochloride) also counteracted the effect of 5-HT on the sAHP. 5-HT3 and 5-HT4 receptor agonists and antagonists were without effects. The intracellular coupling mechanism was not sensitive to pertussis toxin nor to the cAMP dependent protein kinase blocker (Rp)-cAMPS.(ABSTRACT TRUNCATED AT 250 WORDS)

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1994

The reticulospinal glutamate synapse in lamprey: plasticity and presynaptic variability.

1. The glutamatergic synapses formed between the unbranched giant reticulospinal axons onto spinal neurons in lamprey offer a central vertebrate synapse in which the presynaptic element can be impaled with one or several microelectrodes, which may be used for recording as well as microinjection of different substances. To provide a basis for the use of this synapse in studies of release mechanisms, we have examined the use-dependent modulation of the synaptic response under conditions of conventional cell body stimulation, and during direct stimulation of the presynaptic axon. 2. To examine the stability of the mixed electrotonic and chemical reticulospinal excitatory postsynaptic potential (EPSP) over time, action potentials were evoked at a rate of 1 Hz for 800-1000 trials. In three out of seven synapses the chemical component remained at a similar amplitude, while in four cases a progressive decrease (up to 35%) occurred. The electrotonic component remained at a similar amplitude in all cases. 3. During paired pulse stimulation of the reticulospinal cell body (pulse interval 65 ms) the chemical EPSP component showed a net facilitation in all cases tested [from 0.64 +/- 0.35 to 0.89 +/- 0.48 (SD) mV, n = 13], while the peak amplitude of the electrotonic component was unchanged (1.37 +/- 0.68 and 1.36 +/- 0.66 mV, respectively). Recording of the axonal action potential during paired pulse stimulation showed that the width of the first and second action potential did not differ [1/2 width (2.48 +/- 0.39 ms and 2.48 +/- 0.42 ms, respectively; n = 8)]. 4. The degree of facilitation varied markedly between different synapses, ranging from an increase of a few percent to a two-fold increase (24 +/- 16% mean change of total EPSP amplitude, corresponding to 44 +/- 26% mean change of chemical EPSP amplitude). This type of variability was also observed in synapses made from the same unbranched reticulospinal axon onto different postsynaptic cells. 5. When paired pulse stimulation was applied to the reticulospinal axon in the very vicinity of the synaptic area (0.1-1 mm) a net depression of the chemical component occurred in 11 out of 19 cases, and in the remaining cases the level of net facilitation was lower as compared with cell body stimulation (range between +17 and -23% change of total EPSP amplitude; mean -5%; n = 19). 6. To test if the change of the EPSP plasticity during local stimulation correlated with an increased transmitter release, two microelectrodes were placed in the same reticulospinal axon at different distances from the synaptic area.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

8-channel digital filter bank for hearing aid use: preliminary results in monaural, diotic and dichotic modes.

A digital 8-channel signal processing system has been implemented using a TMS 320C25 signal processor. Tests with hearing-impaired subjects showed that the system allows a better fit to a specified frequency response than when using conventional aids with analog filtering. The filter bank has also been tested in dichotic listening experiments, where odd-number channels were fed to one ear and even-number channels to the other. The preliminary results on three hearing-impaired subjects in repeated tests of speech recognition in noise showed an improvement in the order of 2 dB in speech-to-noise ratio for 50% correct recognition as compared to the complete broadband signal presented diotically. Temporal splitting of the signal by periodically switching of the odd and even bands between left and right ears did not show any improvement.

Acoustic Stimulation↗

PubMed1992

Computer simulation of the segmental neural network generating locomotion in lamprey by using populations of network interneurons.

Realistic computer simulations of the experimentally established local spinal cord neural network generating swimming in the lamprey have been performed. Populations of network interneurons were used in which cellular properties, like cell size and membrane conductance including voltage dependent ion channels were randomly distributed around experimentally obtained mean values, as were synaptic conductances (kainate/AMPA, NMDA, glycine) and delays. This population model displayed more robust burst activity over a wider frequency range than the more simple subsample model used previously, and the pattern of interneuronal activity was appropriate. The strength of the reciprocal inhibition played a very important role in the regulation of burst frequency, and just by changing the inhibitory bias the entire physiological range could be covered. At the lower frequency range of bursting the segmental excitatory interneurons provide stability as does the activation of voltage dependent NMDA receptors. Spike frequency adaptation by means of summation of afterhyperpolarization (AHP) serves as a major burst terminating factor, and at lower rates the membrane properties conferred by the NMDA receptor activation. The lateral interneurons were not of critical importance for the burst termination. They may, however, be of particular importance for inducing a rapid burst termination during for instance steering and righting reactions. Several cellular factors combine to provide a secure and stable motor pattern in the entire frequency range.

Animals↗

PubMed1989

A physiological study of the monosynaptic reflex responses of cat spinal alpha-motoneurons after partial lumbosacral deafferentation.

In adult cats the whole S1 and rostral half of the L7 dorsal roots were cut on the left side of the spinal cord to produce a partial monosynaptic deafferentation of the ipsilateral alpha-motoneurons. Three, 6 or 12 weeks later, monosynaptic reflexes (MSRs) were recorded from the L6, L7 and S1 ventral roots or from various peripheral nerves during stimulation of the L6 and remaining parts of the L7 dorsal roots. Also, monosynaptic excitatory postsynaptic potentials (EPSPs) were recorded intracellularly in different types of medial gastrocnemius alpha-motoneurons of the L7 segment during stimulation of various hind limb muscle nerves. The right side with an identical acute deafferentation served as control. On the chronically lesioned side the MSRs were increased in size, also during post-tetanic potentiation. The monosynaptic EPSPs had increased amplitudes in all motoneuron types, but the relation in EPSP size between different motoneuron types as well as between different synergistic inputs remained largely unchanged. EPSP rise times were not changed, and aberrant monosynaptic connections from non-synergist muscles were not observed. It is concluded that the extent of reactive reflex changes may be related to both the number of vacant synaptic sites and the degree of functional synergism between the eliminated and remaining monosynaptic pathways. Possible underlying mechanisms are discussed.

Action Potentials↗