The Centre for Respiratory Failure and Sleep Disorders is collaborating with the David Read Laboratory at the University of Sydney in a major research program. Experiments with animals are being undertaken to investigate various mechanisms operating in sleep apnoea. These include studying an obese pig model with obstructive sleep apnoea, isolated neonatal rat brain preparation and also rats exposed to cocaine in utero.

The Department of Respiratory Medicine is also examining the link between sleep apnoea and levels of plasma cytokines. Cytokines are cells that relay messages between the body's immune cells. They also have a role in stimulating hormone secretion and are involved in the regulation of sleep. Cytokines can be produced by body fat and we are investigating whether some people with marked obesity generate larger amounts of cytokines, which in turn cause sleepiness.

The Department is working on a project where data from an obese mouse model has recently shown a role for a potentially stimulatory effect on respiration by the metabolic protein leptin, produced from body fat. Leptin is normally involved in the regulation of body fat stores. We have found evidence that resistance to the effects of leptin may promote development of respiratory failure during sleep.

We are also continuing our association with the Swedish Obese Subjects study. Data gathered from this controlled trial has shown that surgical weight loss is strongly associated with a reduction in sleep apnoea symptoms when compared with controls.

In association with Metabolism and Obesity Services, we are also evaluating sleep apnoea outcomes in patients undergoing lap band stomach surgery for severe obesity.

The Centre for Respiratory Failure and Sleep Disorders is conducting a program that will determine the characteristic patterns of sleep apnoea in women. This work has demonstrated that women's respiratory reflexes are different from those of men. These differences are particularly related to women's blood pressure responses to oxygen deficiency and their menstrual cycle. Our research indicates that the health effects of sleep apnoea may vary according to menstrual cycle, and so it may be important to study women in the second half of their menstrual cycle to get a better picture of the total effect of sleep apnoea on their body.

Noise from road traffic is an increasing problem in the Sydney area. Traffic volume on certain roads is increasing at night and is becoming a community concern. The Department of Respiratory Medicine is undertaking a pilot study to examine the impact of traffic noise on sleep and daytime performance.

Using an activity monitor (a small watch-like device that measures body movement) as an index of sleep disturbance, we have exposed individuals in their own homes to artificial 'traffic noise' generated by computers. We then compared results with the results from control periods. Results show that traffic noise at a level equivalent to some of the busier Sydney roads at night will lead to sleep disturbance and reduction in daytime vigilance, impaired mood and other psychological problems.

In another study examining the effects of sleep disturbance, the Department has commenced a pilot study looking at brain scans showing changes in brain metabolism in patients with sleep apnoea and in control subjects. The study aims to determine which patients with sleep apnoea are more vulnerable to impaired brain function and reduced driving performance. A computer-based night driving simulator has been developed for use in the study. This study is being conducted in conjunction with the Department of Radiology at St. Vincent's Clinic and the Department of Biochemistry at the University of Sydney.

We are extending this work to include an investigation of truck drivers. We will examine the prevalence of sleep apnoea and how it relates to other aspects of health and driving behaviour. These studies are being conducted in association with the Transport Workers Union and the Department of Roads and Transport. Early results show a higher than average prevalence of sleep apnoea in truck drivers.

We are also examining the impact of sleep loss in people working in the gambling industry. Workers in this industry have never been investigated and yet they are also exposed to unusual work hours and conditions. We have shown that there is a higher than expected level of sleep impairment in this group of workers, in part caused by workers having multiple jobs over different hours of the day.

The Centre for Respiratory Failure and Sleep Disorders is continuing its research into the development of a diagnostic mattress which can detect normal and abnormal breathing movements and sounds. Such a device would have a range of uses including constant monitoring of respiratory status, foetal movements in pregnancy and even in the assessment of cardiac failure.

Over the past fifteen years, the Centre for Respiratory Failure and Sleep Disorders has been ventilating patients with acute and chronic respiratory failure using non-invasive continuous positive airway pressure (CPAP). Initially a research activity, this therapy has now been extended to the management of patients in the Emergency Department and Intensive Care Unit. This has led to the development of a range of low cost portable pressure support ventilators that patients can use at home to support their breathing during sleep.

The Centre's current research projects include comparing the effects of using a full face mask with nasal masks in these patients. We are also testing a range of new 'intelligent' ventilators, which are capable of adjusting ventilation automatically according to patient need.

The Department of Respiratory Medicine is examining the matching of ventilation and blood flow in the lungs before and after long term CPAP therapy in patients with obstructive sleep apnoea. These are the first studies to report the detailed exchange of oxygen and carbon dioxide in patients with this condition. We have found an abnormal degree of inequality in ventilation and blood flow matching, which appears to be improved by CPAP therapy. This suggests that this treatment not only holds the upper airway open, but also improves the efficiency of the lungs.

The Department is also looking at the effects of oxygen and CPAP (non-invasive ventilation) on Cheyne Stokes respiration. Results so far indicate that non-invasive ventilation is superior to the other forms of therapy in treating this condition.

We are also commencing a controlled study which will investigate the impact of upper airway surgery on snoring and sleep apnoea.

The Department of Anaesthetics is investigating the basic physiology in those patients who have sleep apnoea and who need to have anaesthesia for an operation. From an anaesthetics perspective, these patients have either a central nervous system or peripheral cause for their sleep apnoea. Both forms have complications with anaesthesia.

Anaesthetic drugs work by depressing cortical neurones to cause anaesthesia. They also depress the activity of the mid-brain neurones that control spontaneous respiration by reducing their spontaneous activity. Thus if these neurones are already malfunctioning (as in central sleep apnoea) or need to be more highly responsive to maintain respiration (as in peripheral sleep apnoea) there will be complications during anaesthesia, as well as in the recovery from anaesthesia. In addition, the neuronal depression effect of the stronger analgesic drugs means there are continuing risks into the post-operative period for those patients who require these drugs.

The current focus of this study is on identifying the mechanism of disruption to sleep which occurs following anaesthesia. We are also interested in determining the timing of complications, and the nature of the complications that arise at different times in patients with sleep apnoea. For example, the complications encountered during anaesthesia differ from those of the recovery phase, which are different again from those in the post-operative period. The aim of this research is to obtain fundamental knowledge of the mechanisms of sleep and respiratory control during and after an operation, in order to reduce complications and improve the management of patients who suffer from sleep apnoea and require anaesthesia for surgery.

Our plans for future study include examining the effects of different anaesthetic agents on central respiratory drive and looking at how the distribution of drugs through the body, and their metabolism and excretion, affects this respiratory drive.