Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Motivation: The South-African deep level gold mining industry has adapted in many ways, as the pursuit for gold has led deep into the earth core, where rock face temperatures measure around 60°C. Ventilation adapted through engineering developments like refrigeration systems, creating cooler work environments to an extent. Despite these developments the risks of high ambient temperatures coupled with strenuous work and dehydration remains, leading to alternative methods of control that have to indicate whether employees have the necessary functional capacity to perform daily work tasks. Objectives: The objectives of this study were: to measure and compare the physiological effects of the tasks performed by workers in an underground mining environment; To measure the soundness of heart rate as a gauge of work stress in real-life work conditions, taking into account the stressors that influence it; to determine the efficacy of functional and physical work capacity assessments as a method of determining work readiness. Methods: A study group (n = 16) was chosen to represent the “most exposed” work population, all of whom have previously passed the functional work capacity and physical work capacity assessments. The assessments were repeated and the maximal oxygen uptake assessment was done. The participants were divided into two groups (n = 8) according to their work areas. Measurements were taken over a period of eight consecutive shifts. Each group was later divided into three groups as per the work they performed. Dehydration was determined through urine analysis and body weight changes. Heart rate was observed continuously through a heart rate monitor and oral temperature was measured on an hourly basis. Results: The shift durations seen during this study were much longer than the customary 8-hour work day. The mean HR results of group I, which was suspected of having the most strenuous work, were very similar to the results for group II and III. This group did, however, have the highest % heart rate ≥ 120 beats per minute and mean cumulative heart beats, group III having the lowest. All of the groups were found to be mildly dehydrated at the end of their shifts, the urine specific gravity indicating that the participants were generally already considerably dehydrated at the onset of the shifts. Group I was the only group whose mean heart rate had a statistically significant correlation (r ≥ 0.5) with % weight loss. There was a statistically significant (p ≤ 0.05) correlation between heart rate and mean oral temperature for all of the groups. The participants that passed the functional work capacity and physical work capacity assessments were found to have performed comparatively better during the real-time shifts than those that failed. Conclusions: Although there were several employees that had a high mean maximum heart rate, none of the mean heart rates were higher than the self-pacing rate of 110 beats per minute. This ability of self- pacing was seen in the way the participants were able to manage energy expenditure by alternating between heavy and lighter tasks. A great concern is the fact that all of the participants had a % weight loss (0.9 – 2.8% weight loss) indicative of mild dehydration after the shifts, on top of morning urine specific gravity samples (1.020 – 1.025) showing signs of considerable dehydration. Several correlations were found between the functional work capacity and physical work capacity assessments and maximum temperature, maximum heart rate and maximal oxygen uptake, suggesting a significant relationship between the real life situation and the homogenous laboratory setting. comparing the employees that passed the functional work capacity and physical work capacity assessment to those that failed, a marked difference was seen in their respective performances. The groups that passed had a lower mean heart rate and maximum heart rate and higher maximal oxygen uptake. It may, therefore, be concluded that the functional work capacity and physical work capacity assessments provide a valid evaluation of an individual’s work capacity and potential to cope with the varying demands of underground work. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013.

Healthcare practitioners, whom perform accurate sub-maximal exercise tests in healthy individuals, need to understand the physiological demands and normal cardiovascular (CV) responses with exercise. Exercise testing delivers valid information about the physiological systems of individuals that may identify healthy individuals at risk of developing future cardiovascular disease (CVD). Exercise is a common way to assess physiological stress experienced by an individual, because CV abnormalities that are not present at rest, can be elicited during exercise testing and be used to determine the adequacy of cardiac function. Cardiovascular markers like, resting heart rate (HR) and systolic blood pressure (SBP) have been used as simple non-invasive and useful biomarkers of the fundamental status of blood circulation and the CV system in healthy individuals. Studies have contributed to exercise under sub-maximal and maximal stress testing. Modern- day literature lacks information on the safe HR and SBP responses to an increase in workload during a sub-maximal exercise protocol in healthy individuals. Consequently, the first purpose of this study was to identify the current evidence in the literature on CV response during a sub-maximal incremental exercise protocol. Different protocols and modalities contribute to various CV responses over a wide age group and gender. Heart rate and SBP increases in a linear fashion with an increase in workload, irrespective of protocol and modality. The amount of this increase, or the response of these markers, is still a grey area in the literature, especially in healthy individuals. The second purpose of this study was to analyse the HR and SBP response in healthy adults during a sub-maximal incremental exercise test, with an increase in workload (watt). The systematic review found mean changes from baseline for HR and SBP to be 75.7% and 63.5% respectively, on bicycle protocols (N = 3). The treadmill protocols (N = 2) found similar mean changes from baseline of 113.3% for HR and 36.1% for SBP. Descriptive measures as well as Linear regression analyses were performed, using Generalised estimated equations (GEE). An independent t-test was used to compare the males with the female participants: HR and SBP response to an increase in workload (watt). GEE adjustments were made for age, body mass index (BMI) and workload (watt). Significant difference levels were set at p ≤ 0.05. The present once-off subject availability results revealed that male subjects were heavier and taller than their female counterparts (p ≤ 0.05). They also had a noteworthy higher SBPrest, as well as BMI (p ≤ 0.05). The results from the GEE analyses we presented prediction equation, with all variables significant, except for the BMI (p = 0.972 females; p = 0.169 males). In conclusion, the literature review indicated a lack of information on the HR and SBP response with workload in healthy adults. It is advised that further research is needed to test the prediction equations in healthy individuals to determine the validity and reliability. They need to be tested in a controlled clinical environment, where the participants are monitored more thoroughly. By putting these predicted equations to the test, healthcare practitioners will be able to identify an exaggerated HR and SBP response with an increase in workload. If the individual’s response is exaggerated, the healthcare practitioner can intervene to prevent future cardiovascular events. / Thesis (MSc (Biokinetics))--North-West University, Potchefstroom Campus, 2013

Motivation: The South-African deep level gold mining industry has adapted in many ways, as the pursuit for gold has led deep into the earth core, where rock face temperatures measure around 60°C. Ventilation adapted through engineering developments like refrigeration systems, creating cooler work environments to an extent. Despite these developments the risks of high ambient temperatures coupled with strenuous work and dehydration remains, leading to alternative methods of control that have to indicate whether employees have the necessary functional capacity to perform daily work tasks. Objectives: The objectives of this study were: to measure and compare the physiological effects of the tasks performed by workers in an underground mining environment; To measure the soundness of heart rate as a gauge of work stress in real-life work conditions, taking into account the stressors that influence it; to determine the efficacy of functional and physical work capacity assessments as a method of determining work readiness. Methods: A study group (n = 16) was chosen to represent the “most exposed” work population, all of whom have previously passed the functional work capacity and physical work capacity assessments. The assessments were repeated and the maximal oxygen uptake assessment was done. The participants were divided into two groups (n = 8) according to their work areas. Measurements were taken over a period of eight consecutive shifts. Each group was later divided into three groups as per the work they performed. Dehydration was determined through urine analysis and body weight changes. Heart rate was observed continuously through a heart rate monitor and oral temperature was measured on an hourly basis. Results: The shift durations seen during this study were much longer than the customary 8-hour work day. The mean HR results of group I, which was suspected of having the most strenuous work, were very similar to the results for group II and III. This group did, however, have the highest % heart rate ≥ 120 beats per minute and mean cumulative heart beats, group III having the lowest. All of the groups were found to be mildly dehydrated at the end of their shifts, the urine specific gravity indicating that the participants were generally already considerably dehydrated at the onset of the shifts. Group I was the only group whose mean heart rate had a statistically significant correlation (r ≥ 0.5) with % weight loss. There was a statistically significant (p ≤ 0.05) correlation between heart rate and mean oral temperature for all of the groups. The participants that passed the functional work capacity and physical work capacity assessments were found to have performed comparatively better during the real-time shifts than those that failed. Conclusions: Although there were several employees that had a high mean maximum heart rate, none of the mean heart rates were higher than the self-pacing rate of 110 beats per minute. This ability of self- pacing was seen in the way the participants were able to manage energy expenditure by alternating between heavy and lighter tasks. A great concern is the fact that all of the participants had a % weight loss (0.9 – 2.8% weight loss) indicative of mild dehydration after the shifts, on top of morning urine specific gravity samples (1.020 – 1.025) showing signs of considerable dehydration. Several correlations were found between the functional work capacity and physical work capacity assessments and maximum temperature, maximum heart rate and maximal oxygen uptake, suggesting a significant relationship between the real life situation and the homogenous laboratory setting. comparing the employees that passed the functional work capacity and physical work capacity assessment to those that failed, a marked difference was seen in their respective performances. The groups that passed had a lower mean heart rate and maximum heart rate and higher maximal oxygen uptake. It may, therefore, be concluded that the functional work capacity and physical work capacity assessments provide a valid evaluation of an individual’s work capacity and potential to cope with the varying demands of underground work. / Thesis (MSc (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2013.

Current monitoring tools in the intensive care units focus on displaying physiologically monitored parameters (e.g. vital signs such as heart rate, respiratory rate and blood pressure) at the present moment. Added clinical utility can be found by analyzing how the conditions of a patient evolve with time, and automatically relating that dynamics to population trends. Variability analysis consists of monitoring patterns of variation over intervals in time of physiological signals such as heart rate and respiratory rate. Given that illness has been associated in multiple studies with altered variability, most commonly lack of variation, variability monitoring represents a tool whose contribution at the bedside still needs to be explored. With the long term objective of improving care, this thesis promotes the use of variability analysis through three distinct types of analysis: facing the technical challenges involved with the dimensionality of variability analysis, enhancing the physiological understanding of variability, and showing its utility in real world clinical applications. In particular, the contributions of this thesis include: the review and classification into domains of a large array of measures of variability; the design of system and methods to integrate multiple measures of variability into a unique score, called composite measure, bringing relevant information to specific clinical problems; the comparison of patterns of heart rate variability during exercise and sepsis development, showing the inability of single measures of variability to discriminate between the two kinds of stressors; the analysis of variability produced from a physiologically-based model of the cardiovascular system, showing that each single measure of variability is an unspecific sensor of the body, thereby promoting multivariate analysis to the only means of understanding the physiology underlying variability; the study of heart rate variability in a population at high risk of sepsis development, showing the ability of variability to predict the occurrence of sepsis more than 48 hours in advance respect to the time of diagnosis of the clinical team; the study of heart and respiratory rate variability in intubated intensive care unit patients, showing how variability can provide a better way of assessing extubation readiness respect to commonly used clinical parameters. Overall, it is hoped that these novel contributions will help promoting bedside applications of variability monitoring to improve patient care.

In der Literatur steht die Herzfrequenz (HF) in engem Zusammenhang mit dem Sauerstoffverbrauch und dem Energieumsatz sowohl von Menschen als auch von verschiedenen Tierarten. In der vorliegenden Arbeit sollte die Hypothese überprüft werden, ob Kühe mit einer hohen Milchleistung und einer hohen Energieaufnahme eine höhere HF infolge eines leistungsabhängig höheren Sauerstoffverbrauchs als niedriglaktierende Tiere haben. So könnte die HF als Indikator für quantitative Veränderungen des Energieumsatzes sowohl für die Einzelkuh als auch auf Bestandsebene genutzt werden. Material und Methoden In vorliegender Untersuchung wurde die HF von 32 Milchkühen der Rasse Deutsche Holstein gemessen. Die Herde erhielt während der Versuche betriebseigenes Grundfutter sowie Maisschrot, Sojaextraktionsschrot und Milchleistungsfutter II. Die tägliche Futter-, Energie- und Proteinaufnahme wurde bestimmt. Die HF-Messung der Kühe erfolgte in zwei Abschnitten. Abschnitt A: Bei 23 Kühen, unterteilt in unterschiedliche Reproduktions- und Leistungsstadien, wurde an fünf aufeinanderfolgenden Tagen die HF erfasst. Abschnitt B: Bei elf Einzeltieren wurde vom 6. bis 101. Laktationstag (LT) die HF in regelmäßigen Abständen alle 14 Tage und an drei aufeinanderfolgenden Tagen gemessen. Den Tieren wurde hierzu ein Polar Equine RSCX800 Science® Gurt mit integrierten Elektroden, ein dazugehöriger Sender und ein Empfänger (Polar Uhr RS800®) angelegt. Die HF wurde einmal pro Minute gespeichert und alle 24 h in das Computerprogramm Polar Pro Trainer Equine Edition 5® übertragen. Folgende weitere Daten wurden erhoben: Stalltemperatur, relative Luftfeuchtigkeit des Stalles, Body Condition Score, Körpermasse, Körperinnentemperatur, tägliche Milchmenge, Milchfett-, Milcheiweiß- und Milchharnstoffgehalt. Ergebnisse Abschnitt A: Die trockenstehenden Kühe hatten eine HF von 83±8 Schlägen/min, die laktierenden Kühe wiesen mit steigender Milchleistung (24,0; 37,1 und 47,7 kg fett- und eiweißkorrigierte Milch) HF-Werte von 84±3, 85±6 und 87±2 Schlägen/min auf. Abschnitt B: In den ersten 100 Tagen der Laktation verhielt sich die HF mit steigendem LT wie folgt: LT 8: 86±9 Schläge/min, LT 22: 86±11 Schläge/min, LT 36: 87±11 Schläge/min, LT 52: 83±10 Schläge/min, LT 66: 83±10 Schläge/min, LT 81: 83±10 Schläge/min, LT 95: 85±8 Schläge/min. Weder in Abhängigkeit von der Leistung (p=0,75) noch in Abhängigkeit vom LT (p=0,81) waren signifikante Unterschiede der HF zu verzeichnen. Die HF der trockenstehenden Kühe variierte im Vergleich zur HF der laktierenden Tiere nicht. Während ihres 24 h-Verlaufs unterlag die HF aller Gruppen einer großen Variation. Es war zu Ruhezeiten der Tiere eine leistungsabhängige Abstufung der HF zu erkennen. Die Umgebungstemperatur hatte in dieser Untersuchung keinen Einfluss auf die HF (r=0,01; p=0,95). Einen signifikanten negativen Zusammenhang gab es zwischen der HF und dem Alter der Tiere (r=-0,44; p<0,01). Dieser führte am 22. LT zu einem signifikanten Unterschied der HF der erstlaktierenden Kühe im Vergleich mit der HF der älteren Tiere (p=0,04). Ein hoher und signifikanter Zusammenhang konnte zwischen der HF und dem Graviditätstag der trockenstehenden Kühe gezeigt werden (r=0,83; p=0,04). Die Tiere, die sich in einer negativen Energiebilanz befanden, neigten in dieser Untersuchung zu einer niedrigeren HF als die Kühe mit einer positiven Energiebilanz. Schlussfolgerung Telemetrische Systeme gewinnen beim Monitoring von Gesundheitsproblemen und Stoffwechselparametern eines Milchviehbestandes zunehmend an Bedeutung. Die HF kann hier jedoch nicht eingesetzt werden, da sie als Indikator für quantitative Veränderungen des Energieumsatzes weder für die Einzelkuh noch auf Bestandsebene geeignet ist. Nach vorliegenden Ergebnissen haben Kühe mit einer höheren Milchleistung und einer höheren Energieaufnahme keine höhere HF. / Previous studies have revealed a close relationship between heart rate (HR) and energy expenditure in humans and some other animal species. The present study examined whether dairy cows with a higher milk yield and greater energy intake have a higher HR due to greater oxygen consumption. HR might serve as an indicator of quantitative changes of energy expenditure in an individual or in a group of dairy cows at the herd level. Materials and methods The HRs of 32 dairy cows of the German Holstein breed were measured. The cows received forages and fresh beet pulp in combination with ground corn, soybean extracts, and a concentrate during the study. Daily feed, energy, and protein intake were determined. HR measurement was performed in two blocks. In Block A, cows were divided into four groups that differed in reproductive state and milk yield, and HR was measured for five consecutive days. In Block B, every 14 days, HR was recorded for three consecutive days in 11 cows from 6 to 101 days in milk (DIM). A Polar Equine RSCX800 Science® belt with integrated electrodes, a transmitter, and a receiver (Polar RS800®) was applied to the animals. HR was recorded once a minute and transferred every 24 h to the software Polar Pro Trainer Equine Edition 5®. The following data were also collected: stable temperature, stable relative humidity, body condition score, body weight, body temperature, daily milk yield, milk fat, milk protein, and milk urea. Results In Block A, dry cows had a HR of 83±8 beats/min, and lactating cows with increasing milk yield (24.0, 37.1, and 47.7 kg energy-corrected milk) showed HRs of 84±3, 85±6, and 87±2 beats/min, respectively. In Block B, the HRs were as follows: 8 DIM: 86±9 beats/min, 22 DIM: 86±11 beats/min, 36 DIM: 87±11 beats/min, 52 DIM: 83±10 beats/min, 66 DIM: 83±10 beats/min, 81 DIM: 83±10 beats/min, 95 DIM: 85±8 beats/min. There was not a significant difference in the HR according to milk yield (p=0.75) or days of lactation (p=0.81). The HR of dry cows did not differ from that of lactating cows. There was a large variation of HR in all groups during the day. During resting times, HR of the high-yielding cows tended to be higher and HR of the dry cows tended to be lower than the HR of the other groups. The ambient temperature had no influence on HR in this study (r=0.01, p=0.95). There was a significant negative correlation between HR and a cow’s age (r=–0.44, p<0.01). The HR of primiparous cows was higher than that of multiparous cows, but the difference was only significant when cows were 22 DIM (p=0.04). A high and significant correlation was found between HR and pregnancy status (r=0.83, p=0.04), with HR increasing during pregnancy. Dairy cows with a negative energy balance tended to have a lower HR than cows with a positive energy balance. Conclusion Telemetry systems have become increasingly important in monitoring health problems and the parameters of energy metabolism in dairy herds. The results of this study indicate that HR cannot be used as a monitoring tool, because HR is not a suitable indicator of quantitative changes of energy expenditure either at the individual or herd level. According to the results of this study, dairy cows with a higher milk yield and greater energy uptake do not have a higher HR.

Syfte och frågeställningar Syftet med den här studien var att undersöka den aeroba fysiska aktivitetsnivån hos gymnasieungdomar på Bygg- och anläggningsprogrammet under skoldagar som innehöll teorilektioner, praktiska lektioner, idrottslektioner och raster. Frågan som ställdes var: Hur ser den fysiska aktivitetsnivån ut under teorilektioner, praktiska lektioner och lektioner i idrott och hälsa samt under raster hos gymnasieelever på Bygg- och anläggningsprogrammet. Metod I studien deltog 9 pojkar i åldern 16 år, längd 174-192cm och vikt 51-91kg. Den test som genomförts är 5 Minuters Pyramid Test (5MPT) och registrering av aerob fysisk belastning gjordes med hjärtfrekvensmätningar. 5MPT är ett skytteltest som är fem minuter långt, där försökspersonen tar sig fram och tillbaka mellan två stolpar och så snabbt som möjligt passerarfram och tillbaka över en vertikal pyramidformad trappramp (sträcka 5,5 meter). Antalet vändor, skattad ansträngning samt hjärtfrekvens (HF) registrerades. Utvecklad power (effekt) erhölls genom produkten av kroppsmassa, gravitation, antal vändor, höjd på högsta plinten (0,53 m) dividerat med total tiden i 5MPT. Utifrån 5MPT kunde beräknad VO2 max samt Power/kg (W/kg) beräknas för försökspersonen. Testet med hjärtfrekvensregistrering gick till så att eleverna under en skolvecka hela skoldagen bar en pulsklocka med förtejpad urtavla och ett elektrodbälte. De tryckte på händelsemarkering vid rast och när lektionen startade igen. Eleverna förde dagbok där de beskrev vad de gjort under dagen.  Resultat För samtliga försökspersoner kan man se en genomgående trend avseende fysisk belastningsnivå uttryckt som hjärtfrekvens vilket syns i följande resultat. Den högsta pulsen uppnåddes under idrottslektionerna med en genomsnittlig hjärtfrekvens på ca 140 slag/min, den näst högsta under de praktiska lektionerna med 94 slag/min. Därnäst följde rasterna med 83 slag/min och lägst utslag visades under teorilektionerna med en genomsnittlig hjärtfrekvens på ca 80 slag/min. Försökspersonerna utnyttjade ca 30 % av sin maximala syreupptagningsförmåga under de praktiska lektionerna. Slutsats Den här studien har visat att det är under undervisningen i idrott och hälsa och delvis på de praktiska lektionerna som en högre aktivitetsnivå mätt i hjärtfrekvens kan noteras hos försökspersonerna. Studien indikerar också att försökspersonerna utsätts för relativt hög fysisk belastning. Ca 30 % av den maximala syreupptagningsförmågan utnyttjas vid en skoldag med praktiska lektioner. / Aim The aim of the study was to investigate the aerobic physical activity level of high school students who study to become building workers during school days which consist of theory classes, practical classes, physical education classes and pauses. The question to be answered was: How was the aerobic physical activity level during theory classes, practical classes, physical education classes and pauses for high school students in a program for building workers. Method In this study participated 9 boys aged 16, length 174-192 cm and weight 51-91 kg. The test that has been carried out was 5 Minutes Pyramid Test (5MPT). In addition heart rate was measured during the school day. The 5MPT is a 5-minute-shuttle test, in which the participant moves back and forth in a short interval (5.5 m) over boxes (highest height 0.53 m) formed like a pyramid. Power in the pyramid test (5MPT POWER) was calculated as the product of numbers of laps, body mass, gravity and highest box level divided by time. From 5 MPT VO2 max and Power/kg (W/kg) were calculated for the participants. The participant’s heart rates were measured during a week the whole school day by means of a heart monitor with the monitor display taped over and an electrode belt. They pushed a button on the clock to mark when they had pauses and when the classes started again. The participants wrote in a diary what they had done during each day. Results The results show that for each of the participants the same trend considering aerobic physical load level expressed in heart rate in the following results. The highest pulse rate was obtained during the physical education lessons 140 beats/min followed by practical lessons 94 beats/min, pauses 83 beats/min and theory lessons 80 beats/min. The participants are using approximately 30 % of their maximal oxygen uptake during a day with practical lessons. Conclusions This study shows that it is during physical education lessons and to some extent during practical lessons in building construction, a higher activity level measured in heart rate can be noticed in the participants. The study indicates that the participants are exposed to a relative high physical workload. Roughly 30 % of maximal oxygen uptake is used during a day of practical lessons.

BACKGROUND: In children, sleep-related airway obstruction by large tonsils and adenoids can cause obstructive sleep apnea (OSA). OSA may lead to poor growth, developmental delay, behaviour or learning problems. Recent evidence also suggests that children with OSA may develop cardiovascular complications, the mechanisms perhaps involving hypoxemia, the autonomic nervous system, apneas, and arousals. Surgical removal of tonsils and adenoids (adenotonsillectomy (T&A)) usually cures pediatric OSA. To diagnose OSA at all levels of severity, polysomnography is currently the best approach. The McGill Oximetry Score (MOS) is a validated measure based on nocturnal pulse oximetry. An abnormal MOS has a 97% positive predictive value at detecting moderate-severe OSA. Because the MOS was devised by measuring frequency of desaturations (&lt;90%) and numbers of clusters of desaturations, it is not accurate at detecting OSA in children who do not have such drops in oxygen saturation. Accordingly, other measures applicable to a wider spectrum of children should be assessed. These measures should be simpler, less cumbersome, cheaper, and more accessible than polysomnography. / OBJECTIVES: To study alternative approaches that may be used to identify moderate-severe OSA in children, two studies were conducted. We examined one subjective measure - the OSA-18 parent questionnaire - and two objective measures - pulse rate and pulse rate variability. For the OSA-18 study, the goal was to determine whether it would accurately detect children with moderate-severe OSA as indicated by an abnormal MOS. For the pulse rate and pulse rate variability study, the goal was to determine if either or both would decrease after treatment with T&A for children with moderate-severe OSA. / METHODS: For the OSA-18 study, we used a cross-sectional design that included children 1-18 years old referred to a pediatric sleep laboratory for evaluation of suspected OSA. Alongside data from the OSA-18, we analyzed demographic and medical data (from a parent questionnaire) and information regarding adenotonsillar hypertrophy. We estimated sensitivity, specificity, positive and negative predictive values as well as receiver operating curves of the OSA-18 in detecting an abnormal MOS. We also conducted univariate and multivariate logistic regression analyses, using the MOS as the dependent variable and the OSA-18 score and others (age, gender, comorbidities, race) as independent variables. For the second study, we used a retrospective before-after design to compare pulse rate and pulse rate variability as measured by nocturnal pulse oximetry pre- and post-T&A of otherwise healthy children 1-18 years old with moderate-to-severe OSA. / RESULTS: For the OSA-18 study, we studied 334 children (58% male, mean age 4.6 +/- 2.2 years). The OSA-18 had a sensitivity of 40% and a negative predictive value of 73% for detecting an abnormal MOS. In addition, the area under the receiver operating curve was 0.611. While controlling for other independent variables in the logistic regression model, for each unit increase in the OSA-18 Score, the odds of having an abnormal MOS were increased by 2%. However, for each increase in age of 1 year, the odds of having an abnormal MOS were decreased by 17%. In the pulse rate and pulse rate variability study, 25 subjects (88% male; mean age 4.3 +/- 3.6 years) were enrolled. Following T&A, pulse rate and pulse rate variability decreased in 21 of 25 and 23 of 25 children, respectively. Mean pulse rate dropped from 99.7+/-11.2 to 90.1+/-10.7 bpm, p&lt;0.001; age-standardized pulse rate (z-score) from 0.8 (0.4, 1.5) to 0.4 (0, 0.9), p=0.04). Pulse rate variability, as measured by the standard deviation of the pulse rate decreased from 10.3 +/- 2.1 to 8.2 +/- 1.6 bpm, p&lt;0.001. As well, OSA symptomatology, parental concern about breathing during sleep and the MOS all improved. / CONCLUSIONS: Based on the first study we conclude that among children referred to a sleep laboratory, the OSA-18 does not accurately detect which children will have an abnormal MOS. The OSA-18 should not be used in place of objective testing to identify moderate-severe OSA in children. However, from the second study we conclude that measures of the autonomic nervous system such as pulse rate and pulse rate variability, as measured by pulse oximetry, decreased following surgical treatment of moderate-severe OSA. The results of this study potentially serve as important data for further work that would determine the accuracy of pulse rate and pulse rate variability measures and their diagnostic usefulness for OSA at all levels of severity.

Diss. (sammanfattning) Linköping : Univ., 2002. / Härtill 5 uppsatser.

Diss. (sammanfattning) Linköping : Univ., 2004. / Härtill 5 uppsatser.