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Biomedical subjects

K Hume

Publications and source records attributed to K Hume.

At least 19 recordsLinked to original sources
PubMed1998

Experimental separation of time of day and homeostatic influences on sleep.

The purpose of the present study was to evaluate the simultaneous effects on sleep of prior time awake (PRW) and time of day (TOD). Eight male subjects spent 13 days in an isolated sleep lab and had three 8-h baseline sleeps and then 18 4-h sleeps, distributed to provide three sleeps starting at 2400, 0400, 0800, 1200, 1600, and 2000. The three sleeps were preceded by 4, 8, and 12 h of PRW, respectively. ANOVA showed that TST and subjective sleepiness increased with PRW and with closeness to the trough of the circadian rhythm of rectal temperature, whereas sleep latency showed the opposite pattern, and rapid eye movement sleep (REM) latency strongly decreased with PRW and with closeness to the trough. Slow-wave sleep (SWS) increased with PRW, whereas SWS latency and final time awake decreased. REM sleep increased with closeness to the circadian trough, and time awake decreased. Multiple-regression analysis showed that REM latency was closely related to increased SWS in the first sleep cycle, reduced SWS latency, and increased PRW [a short PRW before sleep at noon yielded an extremely short (14 min) REM latency]. Sleep latency and final time awake showed almost exactly the same relationship to TOD and PRW. It is concluded that both homeostatic and circadian influences simultaneously affect sleep, that REM latency is very sensitive to the need for SWS, and that the circadian acrophase strongly interferes with sleep. It should be emphasized that the conclusions should not be extrapolated to longer (> 12 h) wake spans.

Analysis of Variance↗
PubMed1997

Good sleep--its timing and physiological sleep characteristics.

The present study used short sleep episodes to explore the relation between subjective sleep quality, timing and physiological content of sleep. Eight subjects participated in 18 4-h sleep episodes to provide 4, 8, and 12 h of prior time awake before bedtimes at six different times of day in a sleep laboratory insulated from environmental disturbances. The results were analysed by ANOVAs and multiple regression techniques. Subjective sleep quality, calmness of sleep, ease of falling asleep, ability to 'sleep through', number of awakenings, and sleep latency showed a significant pattern of 'better' sleep with increasing prior time awake and with closeness to the circadian minimum (nadir) of rectal temperature (morning hours). 'Ease of awakening' in contrast, 'decreased' with increasing time awake and with closeness to the nadir/ morning hours. Multiple regression analysis showed that subjective sleep quality was predicted by subjective calmness of sleep and ease of falling asleep, among the subjective measures, and by total sleep time (TST) and slow-wave sleep (SWS - stages 3+4) among the physiological sleep measures. The subjective ease of awakening was predicted by slow-wave sleep (negatively) and the circadian maximum of rectal temperature. The results indicate that the duration of wakefulness prior to sleep and the timing of sleep determine its physiological expression, which in turn determines its subjective impression.

Analysis of Variance↗
PubMed1996

Should infection control practitioners do follow-up of staff exposures to patient blood and body fluids?

BACKGROUND: The purpose of this study was to determine the efficiency of a joint infection control/occupational health program for the follow-up of accidental blood or bloody body fluid exposures in health care workers. METHODS: A comprehensive staff follow-up program for all blood exposures with known patient sources was initiated in 1989, consisting of patient follow-up by the Infection Control Department (risk assessment for hepatitis B virus [HBV] and [HIV] infection and obtaining of consent for HIV testing) and staff follow-up by the Occupational Health Department. In 1992 a mailed survey was conducted to examine exposure follow-up policies and responsibilities in large teaching hospitals across Canada. RESULTS: A total of 924 blood exposures with known patient sources were reported between January 1989 and December 1993. HIV and HBV screening was obtained for 67.9% and 87.6% of patients assessed as at low risk and 82.3% and 92.2% of those assessed as at high risk for infection, respectively. Two previously unknown HIV-seropositive patients were identified, one of whom had been classified as at low risk (one of 530 [0.19%] patients at low risk who underwent screening). Primary reasons for screening being missed were patient discharge (46.3%) or communication problems (18.0%). The requirement for informed written consent before HIV screening accounted for the difference in completed HIV and HBV screens. Results of the hospital survey indicated that 40.8% of Canadian hospitals follow up all patients who are involved in blood exposures; however, most hospitals still rely on the physician to obtain consent (87.6%). CONCLUSIONS: Use of ICPs to screen patients involved in staff blood exposures during regular hours may be the most efficient method of follow-up, particularly if supplemented by a backup team of health professionals on nights and weekends. Although screening all patients for HBV/HIV may detect patients with undisclosed high-risk behaviors, institutions must decide whether the practice is cost-effective in areas of low prevalence.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Circadian rhythm adjustment: difficulties in assessment caused by masking.

Measured circadian rhythms consist of endogenous (clock-driven) and exogenous (lifestyle-driven) components. The exogenous components cause difficulties of interpretation of phase and amplitude information. Such effects can be removed by "constant routines", but these protocols are restricted to the laboratory. By contrast, the process of "purification" of circadian rhythms uses the knowledge of an individual's normal lifestyle to separate a measured rhythm into its two components. This method has been shown to be practicable in a variety of circumstances and to provide a feasible alternative to constant routines.

Biological Clocks↗
PubMed1994

A field study of sleep disturbance: effects of aircraft noise and other factors on 5,742 nights of actimetrically monitored sleep in a large subject sample.

This field study assessed the effects of nighttime aircraft noise on actimetrically measured sleep in 400 people (211 women and 189 men; 20-70 years of age; one per household) habitually living at eight sites adjacent to four U.K. airports, with different levels of night flying. Subjects wore wrist-actimeters for 15 nights and completed morning sleep logs. A sample of 178 nights of sleep electroencephalograms (EEGs) were recorded synchronously with actigrams. The EEG was used to develop filters for the raw actigrams, in order to: (1) estimate sleep onset and (2) compare actigrams with aircraft noise events (ANEs). Actigrams, filtered to detect the onset of discrete movements, were able to detect 88% of all EEG-determined periods of interim wakefulness of > 15 seconds and periods of movement time of > 10 seconds. The main findings were: (1) actimetry and self-reports showed that only a minority of ANEs affected sleep, and, for most of our subjects, that domestic and idiosyncratic factors had much greater effects; (2) despite large between-site variations in ANEs, the difference between sites in overall sleep disturbance was not significant; (3) there was a diminished actimetric response to ANEs in the first hour of sleep and, apparently, also in the last hour of sleep; and (4) men had significantly more discrete movements than women and were more likely to respond to ANEs.

Adult↗
PubMed1994

The meaning of good sleep: a longitudinal study of polysomnography and subjective sleep quality.

The present study sought to investigate the meaning of subjectively good sleep, using a longitudinal and intraindividual design. Eight subjects slept in an isolation unit according to an irregular schedule of 6 h sleeps and 1 h naps, designed to give normal amounts of time in bed (1/3 of total), but variable sleep quality. Eight sleeps and eight naps were used for longitudinal simple and multiple regression analyses with standard polysomnographical sleep variables as predictors and subjective sleep quality as dependent variables. The results showed that subjective sleep quality (and related variables) was closely related to sleep efficiency, but not sleep stages. At least 87% efficiency was required for ratings of 'rather good' sleep. In addition, sleep quality ratings improved with closeness (of the awakening) to the circadian acrophase (17.00-21.00 hours) of the rectal temperature rhythm. The subjective ease of awakening differed from most other other variables in that it was related to low sleep efficiency. Objective and subjective homologues of sleep length and sleep latency showed high mean intraindividual correlations (r = 0.55 and 0.64, respectively). It was concluded that objective measures of sleep continuity were closely reflected in perceived sleep quality and that sleep quality essentially means sleep continuity.

Journal Article↗
PubMed1994

The subjective meaning of good sleep, an intraindividual approach using the Karolinska Sleep Diary.

The present experiment used an intraindividual design to investigate the meaning and measurement of "good sleep". Each of 16 subjects slept in an isolation unit according to a schedule (15 sleeps) designed to give variable quality of sleep. Self-rated sleep measures (from the Karolinska Sleep Diary) were obtained after each sleep and subjected to intraindividual regression analyses across time. Most subjective sleep measures showed a strong covariation across conditions. Subjective quality of sleep mainly involved variables of sleep continuity, in particular, perceived calmness of sleep and sleep efficiency. "Sleep quality," "calm sleep," "ease of falling asleep," and ability to "sleep throughout" the time allotted strongly covaried and formed an index of sleep quality. Self-rated ease of awakening deviated from the general pattern and was associated with poor sleep quality. So was reported dreaming (related to awakenings). It was concluded that most subjective sleep measures tend to covary across conditions and that "good sleep" is mainly a question of sleep continuity.

Adolescent↗
PubMed1993

Prolonged and multipatient use of prefilled disposable oxygen humidifier bottles: safety and cost.

OBJECTIVES: Multipatient use and prolonged use of prefilled disposable oxygen humidifier bottles (Aquapak 301, Respiratory Care, Inc., Arlington Heights, IL) were evaluated by performing microbiologic monitoring and a cost analysis on bottles used for varying numbers of patients and lengths of time. METHODS: Humidifiers were hung for a maximum of one month. Monitoring was conducted in 6 different nursing areas. Quantitative cultures were done for aerobes and Legionella. Reusable humidifier bottles also were monitored. RESULTS: Cultures were obtained from 1,311 disposable and 60 reusable humidifiers. No significant bacterial contamination was detected in the prefilled disposable oxygen humidifier units. Ten percent of the reusable bottles were contaminated by organisms associated with skin flora. CONCLUSIONS: Multipatient use and increased duration of use of disposable humidifiers result in cost savings without increasing patient risk. Restricted multipatient use of prefilled disposable oxygen humidifier bottles for a period of one month is a safe and cost-efficient practice.

Alberta↗
PubMed1993

Regulation of sleep and naps on an irregular schedule.

For many occupational groups there is an implicit requirement that sleep be taken according to very irregular schedules. The purpose of this study was to investigate the effects of an irregular sleep schedule on sleep and to determine if such effects could be attributed to the timing of sleep. Eight subjects slept in an isolation unit according to an irregular schedule comprising four 8-hour sleep periods, 12 6-hour sleep periods and 12 1-hour naps. The schedule was designed to give normal amounts of time (1/3 of total) in bed. Large variations in mean sleep efficiency (100-46%) were observed, which in individual cases frequently involved a complete absence of sleep. In 6-hour sleep periods the loss was due to an inability to maintain sleep, whereas in naps the loss was due to an inability to initiate sleep. The major causes of reduced sleep were short prior time awake and bedtime close to the circadian acrophase of rectal temperature (i.e. late afternoon). These two components accounted for 46% of the intraindividual variance of total sleep time (TST). TST increased by 9.2 minutes for each hour of prior time awake and by 10 minutes for each hour of deviation from the circadian acrophase of rectal temperature. Prior time awake also exerted a strong influence on slow-wave sleep (SWS), and circadian phase exerted a similar influence on rapid eye movement sleep. We concluded that irregular sleep patterns strongly affect sleep and that circadian and homeostatic influences are clearly discernible despite the irregularity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Sleep and circadian rhythms of temperature and urinary excretion on a 22.8 hr "day".

Two groups of subjects (total N = 6) were studied in an isolation chamber for a period of 3 weeks whilst living on a 22.8 hr "day". Regular samples of urine were taken when the subjects were awake, deep body temperature was recorded continuously and polygraphic EEG recordings were made of alternate sleeps. The excretion in the urine of potassium, sodium, phosphate, calcium and a metabolite of melatonin were estimated. Measurements of the quantity and quality of sleep were made together with assessments of the temperature profiles associated with sleep. In addition, cosinor analysis of circadian rhythmicity in urinary variables and temperature was performed. The 22.8 hr "days" affected variables and subjects differently. These differences were interpreted as indicating that the endogenous component of half the subjects adjusted to the 22.8 hr "days" but that, for the other three, adjustment did not occur. When the behaviour of different variables was considered then some (including urinary potassium and melatonin, sleep length and REM sleep) appeared to possess a larger endogenous component than others (for example, urinary sodium, phosphate and calcium), with rectal temperature behaving in an intermediate manner. In addition, a comparison between different rhythms in any subject enabled inferences to be drawn regarding any links (or lack of them) that might exist between the rhythms. In this respect also, there was a considerable range in the results and no links between any of the rhythms appeared to exist in the group of subjects as a whole. Two further groups (total N = 8) were treated similarly except that the chamber clock ran at the correct rate. In these subjects, circadian rhythms of urinary excretion and deep body temperature (sleep stages and urinary melatonin were not measured) gave no evidence for deterioration. We conclude, therefore, that the results on the 22.8 hr "day" were directly due to the abnormal "day" length rather than to a prolonged stay in the isolation chamber.

Adolescent↗
PubMed1987

Nosocomial infections on nursing units with floors cleaned with a disinfectant compared with detergent.

Nosocomial infections on eight acute care nursing units in a tertiary care hospital was compared between two 3-month periods in which floors were cleaned with either disinfectant or detergent. Personnel performing infection surveillance were unaware of the cleaning product used. Surface cultures from selected floor sites were obtained at 3 and 6 months to assess microbial contamination. The combined nosocomial infection rate for the eight wards did not differ between disinfectant (8.0/100 patient discharges) and detergent (7.1/100). For individual wards, a significant difference in nosocomial infection rate between the two periods was observed in only one ward, favouring the detergent. No differences in floor contamination were observed.

Alberta↗
PubMed1986

An outbreak of group A streptococcal bacteremia in an intensive care unit.

Admission of a patient with group A streptococcal cellulitis and bacteremia to the intensive care unit of a tertiary care teaching hospital was followed by two subsequent cases of group A streptococcal bacteremia with pneumonia in the unit. All streptococcal isolates were the same M- and T-type. Endotracheal intubation with respiratory ventilation was a risk factor for disease acquisition. The characteristics of onset of the two nosocomially acquired cases suggested that a staff member may have been, at least transiently, a streptococcal carrier, but no such carrier was identified. No further cases occurred subsequent to a period when all patients in the unit received antibiotics effective for group A streptococcal therapy.

Aged↗
PubMed1979

Abortion.

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Abortion, Induced↗