Factors affecting daytime function in the sleep apnoea/hypopnoea syndrome

The sleep apnoea/hypopnoea syndrome (SAHS) is characterised by repetitive upper airway obstructions during sleep, which lead to recurrent hypoxaemia and brief arousals from sleep. SAHS patients suffer from excessive daytime sleepiness (EDS), cognitive impairments and decreased psychological well -being. Previous studies have examined relationships between the nocturnal events of SAHS and a limited number of daytime function measures, frequently in small, non -consecutive patient samples. Relationships found have been either weak or non -significant. This thesis examines the relationships between a wide range of nocturnal sleep and breathing variables and daytime function. Additionally, this thesis examines the use of subjective and objective measures of daytime sleepiness, to determine which tests provide the most useful information for SAHS patients.A pilot study found that neither the 103 patients' nor their partners' Epworth rating of sleepiness were strong predictors of SAHS severity. In 150 patients with a wide range of SAHS severity, relationships between nocturnal events and daytime function were examined using newer definitions of arousal and measures of sleep continuity. A broad battery of daytime tests were used including the maintenance of wakefulness test (MWT) and the short form (SF) -36. Unlike previous studies, all correlations were controlled for age and awake oxygen saturation, known to influence the variables measured. The current study also examined these correlations in an unselected patient sample with a range of disease severity. The study found a lack of strong relationships between conventional nocturnal sleep and breathing variables and daytime function. Few baseline variables significantly predicted CPAP use.Daytime function measures were compared within the 150 patients. The multiple sleep latency test (MSLT) and the MWT displayed a moderate, discordant relationship. Measures of cognitive function, psychological well -being and subjective sleepiness ii better related to the MWT than MSLT, suggesting that the MWT may be a more useful tool in assessing functional impairment in sleep apnoea.A randomised cross -over study, on 12 SANS patients, compared daytime sleepiness measured following a night's sleep at home (as performed in this thesis) versus a night in the sleep centre (standard protocol). Preliminary results indicated that daytime sleepiness, as measured by the MSLT and MWT, was not significantly different between the two study limbs. This suggests that the non -standard method of conducting the MSLT and MWT in this thesis does not explain the lack of correlational relationships between nocturnal measures and daytime sleepiness.The studies presented in this thesis demonstrate a lack of identified factors affecting daytime function in a group of unselected SANS patients. This may be due to inter - individual patient variability. Also, more sophisticated nocturnal SANS measures should be examined, as should more `real -life' daytime assessments, such as ambulatory EEG recorded during a patient's normal daily routine

Non-invasive respiration monitoring by thermal imaging to detect sleep apnoea

Accurate airflow measurements are vital to diagnose apnoeas; respiratory pauses occurring during sleep that interrupt airflow to the lungs. Apnoea diagnosis usually requires an overnight polysomnography during which numerous vital signs are monitored, including respiratory rate and airflow. The current gold standard in respiration monitoring is a nasal pressure sensor which is placed inside the nostrils of the patient and through which the airflow is measured. Due to the contact nature of the sensor, it is often refused or removed during polysomnography, especially in the case of paediatric patients. We have found that around 50% of children refuse the use of nasal prongs due to its in-vasiveness, and of those that accepted it, 64% removed the sensor over the course of the polysomnography. We evaluated a non-contact method to monitor respiration by developing infrared thermal imaging, whereby temperature fluc-tuations associated with respiration are measured and correlated with airflow. A study was carried out on a sample of 11 healthy adult volunteers whose res-piratory signals were recorded over four simulated apnoea scenarios. The res-piratory signal obtained through thermal imaging was compared against the gold standard nasal pressure sensor. In 70% of cases, apnoea related events were well correlated with airflow sensor readings. In 16% of recordings the subject’s head position did not allow correct identification of the region of interest (i.e. the nostrils). For the remaining 14% of cases there was partial agreement between the thermal measurements and airflow sensor readings. These results indicate thermal imaging can be valuable as a detection tool for sleep apnoea, particularly in the case of paediatric patients

Exploratory study to evaluate respiratory rate using a thermal imaging camera

Background: Respiratory rate is a vital physiological measurement used in the immediate assessment of unwell children and adults. Convenient electronic devices exist for measurement of pulse, blood pressure, oxygen saturation and temperature. Although devices which measure respiratory rate exist, none has entered everyday clinical practice for acute assessment of children and adults. An accurate and practical device which has no physical contact with the patient is important to ensure readings are not affected by distress caused by the assessment method. Objective: To evaluate the use of a thermal imaging method to monitor respiratory rate in children and adults. Methods: Facial thermal images of adult volunteers and children undergoing elective polysomnography were included. Respiration was recorded for at least two minutes with the camera positioned one metre from the subject's face. Values obtained using the thermal imaging camera were compared with those obtained from contact methods such as nasal thermistor, respiratory inductance plethysmography, nasal airflow and End Tidal Carbon Dioxide (CO2). Results: A total of 61 subjects, including 41 adults (age range 27 to 46 years) and 20 children (age range 0.5 to 18 years) were enrolled. The correlation between respiratory rate measured using thermal imaging and the contact method was r=0.94. Sequential refinements to the thermal imaging algorithms resulted in the ability to perform real-time measurements and an improvement of the correlation to r=0.995. Conclusion: This exploratory study shows that thermal imaging derived respiratory rates in children and adults correlate closely with the best performing standard method. With further refinements, this method could be implemented in both acute and chronic care in children and adults

A Novel, Contactless, Portable “Spot-Check” Device Accurately Measures Respiratory Rate

Respiratory rate (RR) is an important vital sign used in the assessment of acutely ill patients. It is also used as to predict serious deterioration in a patient's clinical condition. Convenient electronic devices exist for measurement of pulse, blood pressure, oxygen saturation and temperature. Although devices which measure RR exist, none has entered everyday clinical practice. We developed a contactless portable respiratory rate monitor (CPRM) and evaluated the agreement in respiratory rate measurements between existing methods and our new device. The CPRM uses thermal anemometry to measure breath signals during inspiration and expiration. RR data were collected from 52 healthy adult volunteers using respiratory inductance plethysmography (RIP) bands (established contact method), visual counting of chest movements (established non-contact method) and the CPRM (new method), simultaneously. Two differently shaped funnel attachments were evaluated for each volunteer. Data showed good agreement between measurements from the CPRM and the gold standard RIP, with intra-class correlation coefficient (ICC): 0.836, mean difference 0.46 and 95% limits of agreement of -5.90 to 6.83. When separate air inlet funnels of the CPRM were analysed, stronger agreement was seen with an elliptical air inlet; ICC 0.908, mean difference 0.37 with 95% limits of agreement -4.35 to 5.08. A contactless device for accurately and quickly measuring respiratory rate will be an important triage tool in the clinical assessment of patients. More testing is needed to explore the reasons for outlying measurements and to evaluate in the clinical setting

Thermal imaging method for measurement of respiratory rate

Background: Monitoring respiratory rate (RR) is an important task for medical diagnosis that is neglected due to complexities in performing it. Current methods require the sensing device to be attached to the subjects' body thereby constraining or causing them discomfort and thus potentially affecting the breathing rate. We have developed a noncontact method for RR monitoring using a thermal camera.Method: Algorithms to capture images and detect the location of the face in each image were developed. The amount of emitted infrared radiation was then determined and signal processing techniques were then utilised to obtain the respiration rate in real time. A FLIR A40 thermal camera was used in this study. The evaluations were conducted against five existing contact based methods. Results: Tests were conducted on 51 adults (mean age 35.7) and 20 children (mean age 6.4 years). Mean RR (thermal imaging) 14.8 per minute; (chest and abdominal band) 14.8 per minute in adults. The correlation coefficient was 0.88 - 0.998 in adults and 0.578 – 0.999 in children depending on the method used. Figure 1 shows a respiration signal for a child obtained during the evaluation

Development of the ’BreathEasy’ contactless portable respiratory rate monitor (CPRM)

Background: Respiratory rate (RR) is a vital physiological measurement used in the immediate assessment of acutely ill patients. It is used as a predictor of serious deterioration in a patient's clinical condition. Convenient electronic devices exist for measurement of pulse, blood pressure, oxygen saturation and temperature. Although devices which measure RR exist, none has entered everyday clinical practice. We have developed a contactless portable respiratory rate monitor (CPRM). We aimed to measure agreement with existing methods of RR measurement.Method:RR data were collected from 33 adult volunteers using respiratory impedance plethysmography (RIP) bands (established contact method), visual counting of chest movements (established non-contact method) and the CPRM (new method), simultaneously. Two to three data sets were collected for each volunteer.Results:Data showed good agreement between measurements from the CPRM and the gold standard RIP with limits of agreement -4.6 – 7.8

Medical Devices for Measuring Respiratory Rate in Children: a Review

Respiratory rate is an important vital sign used for diagnosing illnesses in children as well as prioritising patient care. All children presenting acutely to hospital should have a respiratory rate measured as part of their initial and ongoing assessment. However measuring the respiratory rate remains a subjective assessment and in children can be liable to measurement error especially if the child is uncooperative. Devices to measure respiratory rate exist but many provide only an estimate of respiratory rate due to the associated methodological complexities. Some devices are used within the intensive care, post-operative or more specialised investigatory settings none however have made their way into the everyday clinical setting. A non-contact device may be better tolerated in children and not cause undue stress distorting the measurement. Further validation and adaption to the acute clinical setting is needed before such devices can supersede current methods

Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints

Purpose: The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints. Methods: In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk1) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day1) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥7 days and preceded by a 7-night familiarisation trial. Results: Polysomnography showed less awakenings with CP than CON (21.3±9.7 vs. 29.3±13.8 counts, respectively; P=0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3±1.5 vs. 1.9±0.6 counts, respectively; P=0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.0±0.00 vs. 0.97±0.05 AU, respectively; P=0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P>0.05). Conclusion: CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints