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Biomedical subjects

L G Olson

Publications and source records attributed to L G Olson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Emerging issues in sleep-disordered breathing.

Community studies of problems with breathing during sleep suggest that sleep-disordered breathing is a better general term than sleep apnoea. Male sex, increasing age and increasing neck size are the main factors differentiating people with from those without sleep-disordered breathing. The contribution of sleep-disordered breathing to morbidity has not been established. Future research should address the possible cardiovascular associations of sleep-disordered breathing, its impact on sleepiness in the community, and the cost-effectiveness of treatment.

Australia↗
PubMed1996

Nasal inflammation and chronic ear disease in Australian Aboriginal children.

OBJECTIVE: Chronic middle ear disease is common in Aboriginal children, and may be linked to nasal inflammation and Eustachian tube dysfunction. The pattern of nasal inflammation is unknown. The study reported here was performed to define the role of allergy and infection in causing nasal inflammation in Aboriginal children with chronic middle ear disease. METHODOLOGY: Thirty-one Aboriginal children aged between 3 and 7 years underwent clinical assessment, audiometry and allergy skin tests. Nasal swabs for bacterial culture and cytology were performed during the winter and again in spring to identify any seasonal variation. A randomized trial of nasal beclomethasone for 8 weeks was conducted in children with abnormal tympanometry to identify the effect of therapy upon nasal cytology. RESULTS: Twenty-six of the 31 children had abnormal tympanograms. Average hearing levels were reduced in nine children. Pathogenic organisms were isolated from most children: Streptococcus pneumoniae (82%), Haemophilus influenzae (79%), Moraxella catarrhalis (39%) and Staphylococcus aureus (29%). Eight of the 31 children (26%) were atopic. Nasal cytology disclosed a marked neutrophil infiltrate (80% of cells) during the winter, which fell significantly in spring to 52% of cells. Only two subjects had nasal eosinophilia of >10%. There was no effect of beclomethasone on nasal cytology. CONCLUSIONS: Chronic ear disease in Aboriginal children is associated with nasal inflammation, neutrophil infiltration and the presence of bacteria. These features suggest respiratory infection as the main cause of chronic nasal inflammation in Aboriginal children with middle ear disease. There is a seasonal variation in the severity of the nasal infiltrate, consistent with increased infections during winter. Despite a high prevalence of atopy, allergic nasal disease was uncommon.

Anti-Inflammatory Agents↗
PubMed1996

A community survey of insomnia in Newcastle.

This study aimed to estimate the prevalence of sleeping difficulty in an urban community and the frequency with which those with sleep difficulty seek medical care and use prescribed medication for sleep. Randomly selected persons aged over 16 years were invited to participate in a telephone survey. A total of 628 individuals was approached and 535 (85 per cent) were interviewed. Older subjects, women and those not in paid employment were overrepresented in the sample. Difficulty sleeping often or always was reported by 17 per cent of men and 25 per cent of women. Of subjects with difficulty in sleeping, 31 per cent had sought medical care. There was no difference between men and women in this regard. Use of prescription medication was reported by 20 per cent of men and 29 per cent of women with sleep difficulty.

Adolescent↗
PubMed1996

Vector expansion techniques for the inverse problem of electrocardiography: application to a realistic heart-torso geometry.

We have previously compared four numerical techniques utilizing both a homogeneous and inhomogeneous eccentric sphere model problem. In those studies we found that the Generalized Eigensystem approach generally gave superior performance over both truncated singular value decomposition and zero order Tikhonov regularization. In this paper we extend the comparison to the case of a realistic heart-torso geometry. With this model, the generalized eigensystem approach again provides superior performance as measured by both relative error and correlation coefficient.

Animals↗
PubMed1995

Using quality-control analysis of peak expiratory flow recordings to guide therapy for asthma.

OBJECTIVE: To compare the action points in published asthma management plans with those derived from quality-control analysis of peak expiratory flow recordings. DESIGN: Longitudinal observational study. SETTING: An ambulatory asthma education and management program in a tertiary care hospital. PATIENTS: 35 adults with asthma and exacerbation of asthma. MEASUREMENTS: Peak expiratory flow diaries and symptom recordings. RESULTS: Asthma action points from published asthma management guidelines had poor operating characteristics. The success rate was 35% when the action point was a peak expiratory flow rate less than 60% of the patient's best peak flow. The success rate improved to 88% when the action point was a peak expiratory flow rate less than 80% of the patient's best peak flow. Published action points had a high failure rate. Peak flow decreased to below the published action points during a stable period of asthma in 7% to 51% of patients studied. Action points defined using quality-control analysis did significantly better. A peak flow value less than 3 standard deviations below the patient's mean peak flow detected 84% of exacerbations and had a low failure rate (19%). Other quality-control tests had sensitivities of 91% and 71%. Quality-control action points could detect exacerbations up to 4.5 days earlier than conventional methods. CONCLUSIONS: Individualized action points can be derived for patients with asthma by applying quality-control analysis to peak flow recordings. These action points are more sensitive in detecting exacerbations of asthma and have fewer false-positive results. Action plans developed in this manner should be more useful for the early detection of deteriorating asthma.

Adrenal Cortex Hormones↗
PubMed1995

The effects of errors in assumed conductivities and geometry on numerical solutions to the inverse problem of electrocardiography.

In this paper we used a previously proposed model problem to examine the effects of inhomogeneities on four techniques for numerically solving the inverse problem of electrocardiography. The layered inhomogeneous eccentric spheres system contains three regions representing the lungs, muscle, and subcutaneous fat, and is numerically modeled using finite elements. We simulated both anterior and posterior spherical cap activation fronts. We examined inverse solutions based on zero order Tikhonov regularization, truncated singular value decomposition, our new generalized eigensystem approach, and a modification of the generalized eigensystem approach. The effects on the inverse solutions of geometrical errors, errors in the assumed conductivities, and homogeneous torso assumptions were examined.

Animals↗
PubMed1995

A community study of snoring and sleep-disordered breathing. Symptoms.

Four hundred forty-one subjects 34 to 69 yr of age were recruited from a random sample of the community. The sample was biased in favor of men, snorers, and subjects with subjective sleep complaints. They answered a questionnaire and were monitored in their homes for sleep-disordered breathing (SDB). This report concerns the presence of symptoms associated with the obstructive sleep apnea (OSA) syndrome in the subjects with SDB detected in this community sample. Most of the symptoms commonly recognized as occurring in OSA were associated with SDB in our sample: snoring that disturbed the sleep of other persons, reports of apnea, reports of gasping or choking sounds during sleep, and finding the bedclothes in disarray in the mornings had significant univariate associations with SDB. Nocturnal choking and morning headache were negatively associated with SDB. Excessive daytime somnolence (EDS) was reported by 41% of those with SDB, but it was also reported by 37% of snorers without SDB and by 37% of nonsnorers. We conclude that the symptoms seen in clinic patients with OSA also occur in subjects with SDB who have not presented for medical attention. Enumeration of these symptoms by questionnaire, however, is a poor test for OSA in the community. EDS was reported by a higher than expected proportion of subjects not affected by SDB, suggesting that causes of self-reported EDS other than SDB may be common.

Accidents, Traffic↗
PubMed1995

A community study of snoring and sleep-disordered breathing. Prevalence.

We conducted a study of the prevalence of sleep-disordered breathing in subjects derived from a random sample of the population. A total of 2,202 subjects 35 to 69 yr of age were approached. Four hundred forty-one answered a questionnaire concerning their sleep symptoms, general health, and habits such as alcohol consumption, and they were monitored for sleep-disordered breathing (SDB). The sample was biased in favor of snorers and those with other subjective sleep complaints. Fifty-six percent of the subjects were men. Of the 441 subjects 79 (17.9%) had SDB (more than 15 episodes of apnea or hypopnea per hour: respiratory distress index [RDI] > or = 15), 289 were snorers but had RDI < 15, and 73 were nonsnorers. The prevalence of SDB in this sample was therefore at least 3.6% (79 of 2,204). The minimum prevalence in men was 5.7%, and in women it was 1.2%. Logistic regression identified only male sex as an independent predictor of snoring without SDB (adjusted odds ratio [OR], 3.24; 95% CI, 1.33 to 7.82), body mass index (adjusted OR for an increase of 5 kg/m2, 0.95; 95% CI, 0.85 to 1.05), and alcohol consumption (adjusted OR for an increase of 10 g/day, 1.05; 95% CI, 0.84 to 1.37) were not significant predictors of snoring. The independent predictors of SDB among snorers were age (adjusted OR for an increase of 5 yr, 1.26; 95% CI, 1.08 to 1.47) and neck circumference (adjusted OR for an increase of 2 cm, 1.53; 95% CI, 1.16 to 2.00).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

A community study of snoring and sleep-disordered breathing. Health outcomes.

Four hundred forty-one subjects 34 to 69 yr of age were recruited from a random sample of the community. They answered a questionnaire and were monitored in their homes for sleep-disordered breathing (SDB). This report concerns the association between observed SDB and arterial hypertension and vascular disease. Hypertension was defined as self-report of a diagnosis of hypertension made by a physician, current treatment for hypertension, or a systolic pressure greater than 150 mm Hg or a diastolic pressure greater than 90 mm Hg. Coronary artery disease was defined by self-report of angina or myocardial infarction of "heart attack." There were few cases of stroke or claudication, and a category of "occlusive vascular disease" was defined by self-report of coronary artery disease or of "blocked arteries" or stroke. Subjects were classified as snorers (n = 289) or nonsnorers (n = 73) by self-report of regular snoring, and as having SDB (n = 79) if more than 15 abnormal respiratory events were recorded per hour of recording. There were significant increases in the prevalence of hypertension, coronary artery disease, and occlusive vascular disease from nonsnorers (26, 7, and 10%, respectively) through snorers (39, 12, and 17%) to subjects with SDB (57, 20, and 28%). The crude odds ratio for SDB versus nonsnorers was 3.8 (95% CI, 1.9 to 7.5) for hypertension, 3.5 (1.2 to 10.0) for coronary artery disease, and 3.7 (1.5 to 9.1) for occlusive vascular disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

The effects of noise and errors in heart size on numerical techniques for the inverse problem of electrocardiography.

In this study we examine the effects of both noise and geometrical errors on four numerical methods proposed for solving the inverse problem of electrocardiography. The heart-body system is modeled using an inhomogeneous eccentric sphere model. The cardiac source is modeled as a double layer spherical cap with either an anterior or posterior location. Epicardial potentials determined using the numerical techniques were compared with the analytically determin potentials in the presence of both noise and errors in assumed geometry.

Biomedical Engineering↗
PubMed1994

Consideration of narcolepsy in the differential diagnosis of chronic fatigue syndrome.

OBJECTIVE: To justify the inclusion of narcolepsy in the differential diagnosis of patients with chronic fatigue. CLINICAL FEATURES: We report three patients aged 17 (two women and one man) and one woman aged 45 who had been diagnosed as having chronic fatigue syndrome (CFS). They had no psychiatric illness. Their main problem was severe daytime sleepiness, presenting as "tiredness and fatigue". The history, sleep study and multiple sleep latency test suggested a diagnosis of narcolepsy. INTERVENTION: Treatment with methylphenidate resulted in complete resolution of symptoms in two patients and significant improvement in the other two. CONCLUSIONS: The differential diagnosis of CFS requires the exclusion of other conditions. If daytime sleepiness is a major complaint, other symptoms of narcolepsy should be sought and the diagnosis confirmed with sleep study and a multiple sleep latency test.

Adolescent↗
PubMed1994

A generalized eigensystem approach to the inverse problem of electrocardiography.

We develop a new approach to the ill-conditioned inverse problem of electrocardiography which employs finite element techniques to generate a truncated eigenvector expansion to stabilize the inversion. Ordinary three-dimensional isoparametric finite elements are used to generate the conductivity matrix for the body. We introduce a related eigenproblem, for which a special two-dimensional isoparametric area matrix is used, and solve for the lowest eigenvalues and eigenvectors. The body surface potentials are expanded in terms of the eigenvectors, and a least squares fit to the measured body surface potentials is used to determine the coefficients of the expansion. This expansion is then used directly to determine the potentials on the surface of the heart. The number of measurement points on the surface of the body can be less than the number of finite element nodes on the body surface, and the number of modes employed in the expansion can be adjusted to reduce errors due to noise.

Action Potentials↗
PubMed1993

A comparison of clinical assessment and home oximetry in the diagnosis of obstructive sleep apnea.

In order to determine whether measurement of arterial oxygen saturation (SaO2) could identify patients with obstructive sleep apnea (OSA), 98 consecutive patients referred for assessment of snoring and/or daytime somnolence were assessed clinically and then underwent both unsupervised oximetry in their homes and formal polysomnography. Clinical assessment identified patients with an apnea+hypopnea index (AHI) > or = 15 events per hour with a sensitivity of 79% and a specificity of 50%. Home oximetry analyzed by counting the number of arterial oxygen desaturations recorded was inferior to clinical assessment. For desaturations of 2% or more from baseline, desaturation index (DI) > or = 15 per hour identified patients with AHI > or = 15 with sensitivity 65% and specificity 74%; for 3% desaturations, sensitivity was 51% and specificity 90%; and for 4% desaturations, sensitivity was 40% and specificity 98%. From the oximetry data, the percentage of time spent at SaO2 below 90% (CT90) was also calculated. CT90 > or = 1% identified patients with AHI > or = 15 with sensitivity 93% and specificity 51%; for patients with AHI > or = 15 ultimately given nasal continuous positive airway pressure (CPAP), the sensitivity of a CT90 > or = 1% was 100%. We concluded that home oximetry with CT90 < 1% practically excludes clinically significant OSA. Conversely, home oximetry with DI > or = 15 for 4% desaturations makes OSA likely: the positive predictive value for OSA is 83% if the pretest probability of OSA is 30% and over 90% if the pretest probability is at least 50%.

Adult↗
PubMed1991

Disorders of movement and behaviour during sleep.

OBJECTIVE: To outline recently described movement disorders during sleep which are common and poorly recognised. DATA SOURCES: Computer-based literature search up to July 1990 (with the index terms sleep disorders, sleep myoclonus, nocturnal myoclonus, periodic movements in sleep, REM behaviour disorder and parasomnias) supplemented by a manual search through the references of papers obtained by computer search and a manual search through contents of the following journals: Sleep, Sleep Research, Neurology and Brain. DATA SYNTHESIS AND CONCLUSION: There is a group of common and poorly recognised movement disorders during sleep. The patient usually presents complaining of disturbed sleep, daytime somnolence and abnormal nocturnal behaviour. These conditions are susceptible to precise diagnosis and effective treatment.

Epilepsy↗
PubMed1991

Pressure-volume properties of the upper airway in man.

We report a method of measuring the static pressure-volume properties of the upper airway in unanesthetised humans. In 10 normal subjects the pressure in the upper airway was measured during aspiration of air in 10 ml decrements from 30-40 ml above resting volume to 30-40 ml below resting volume, with the glottis closed voluntarily and the oro-pharyngeal muscles relaxed. The pressure-volume properties of the upper airway were well described by the pressure-volume rate upper airway elastance (UAE, cmH2O/ml). The mean (+/- 95% CI) UAE measured at near total lung capacity and with the neck in neutral position for all runs in all subjects was 0.22 +/- 0.06 cmH2O/ml. When UAE was measured repeatedly on different days the greatest change observed was from a mean value of 0.17 cmH2O/ml on one day to 0.25 cmH2O/ml on another, and the standard deviation of the means from different days ranged from 0.01 to 0.04. Neither hypoxia (SaO2 80-85%) nor hyperoxic hypercapnia (PETCO2 65-75 mmHg) had any influence on UAE. Maximal extension of the neck did not affect UAE, but flexion of the neck was associated with a rise in UAE from a mean of 0.23 +/- 0.05 cmH2O/ml to a mean of 0.53 +/- 0.14 cmH2O/ml. UAE was not affected by the lung volume at which measurements were made. We conclude that upper airway pressure-volume properties can be measured non-invasively in man, and that in their linearity, reproducibility and lack of sensitivity to hypoxia and hypercapnia they resemble those of experimental animals.

Adult↗
PubMed1991

Mechanical properties of the rabbit upper airway during hypoxia and hypercapnia.

It has been suggested that the response of upper airway muscles to hypoxia may be different from the response of these muscles to hypercapnia. We therefore measured pulmonary ventilation and the mechanical properties of the isolated upper airway in 9 anesthetised rabbits during respiration of hypoxic and hypercapnic gas mixtures. Each animal was exposed to several levels of elevated inspiratory CO2 fraction, FICO2 (0.03 to 0.17) and depressed inspiratory O2 fraction, FIO2 (0.19 to 0.09). The steady-state ventilatory response, the tidal pressure in the upper airway (PTUA) and the upper airway elastance were measured under each condition. Straight lines were calculated by least squares regression relating pulmonary VT to FICO2 and FIO2 and PTUA to FICO2 and FIO2. The PTUA was estimated graphically at two levels of hypoxia and hypercapnia producing equal augmentation of VT. The ratio of PTUA during hypoxia to PTUA during hypercapnia was 1.06 +/- 0.21 (mean +/- 95% C.I.) at low VT and 1.15 +/- 0.25 at high VT. Elastance of the upper airway rose from 6.25 +/- 1.13 cmH2O/ml under control conditions to a maximum of 7.95 +/- 1.24 cmH2O/ml (P less than 0.05) during hypercapnia and to a maximum of 8.02 +/- 1.17 cmH2O/ml (P less than 0.05) during hypoxia. There was no difference between the mean (+/- 95% C.I.) change associated with hypercapnia (1.64 +/- 1.08 cmH2O/ml) and the mean change associated with hypoxia (1.77 +/- 1.26 cmH2O/ml). We concluded that hypoxia did not result in a greater change in upper airway mechanical properties than hypercapnia.

Animals↗
PubMed1991

Long-term nasal CPAP does not ameliorate obstructive sleep apnoea.

Fifty-seven patients with obstructive sleep apnoea (OSA) were treated for at least six months with nasal continuous positive airway pressure (CPAP). At follow-up, sleep studies were performed in which CPAP was not used for the first half of the night. We compared the severity of OSA at follow-up without CPAP to the severity of OSA during the patient's initial diagnostic study. Apnoea and hypopnoea index (AHI) fell from 41.4 +/- 7.5 (mean +/- 95% CI) to 34.8 +/- 7.9 (p = 0.06 by Wilcoxon test) and minimum oxygen saturation rose from 71.6 +/- 3.2 to 78.5 +/- 2.6 (p less than 0.001). Some of this change may have been due to reduced REM sleep in the follow-up study (10.5 +/- 2.1% Total Sleep Time vs 7.4 +/- 2.4% TST, p less than 0.05). Long-term nasal CPAP was not associated with any reduction of obesity (BMI before CPAP 31.9 +/- 1.0, after CPAP 31.7 +/- 1.0 (p = 0.39). Systolic arterial pressure fell (before CPAP 143.0 +/- 4.5 mmHg, after CPAP 136.3 +/- 4.6, p less than 0.05) but diastolic pressure did not (before CPAP 88.5 +/- 3.0 mmHg, after CPAP 85.6 +/- 2.9 mmHg, p = 0.11). We concluded that the effect of CPAP treatment for six or more months was a small fall in AHI and a small rise in minimum SaO2, but that this would be of marginal clinical significance, and may be artefactual.

Aged↗