Almost exactly 30 years after the publication of his pioneering paper on positive airway pressure for sleep apnoea (PAP) in The Lancet, Colin Sullivan continues to extend the boundaries of sleep medicine. In those three decades, PAP has gone from an obscure treatment available to few to an effective, portable treatment that has improved the sleep, and thus lifestyles, of millions worldwide.

From a family of tradesmen, Sullivan and his two brothers were constantly inventing and building new things. It was a theme that would resonate throughout his life. After completing medical studies at the University of Sydney, Sullivan went on to specialise in respiratory medicine at Sydney’s Royal Prince Alfred Hospital where he met mentor David Read, an expert on sudden infant death syndrome. They postulated that this syndrome might be caused by a breathing defect and this work piqued Sullivan’s interest in sleep science. During his research Sullivan and long-time friend and colleague Michael Hensley dug up papers that referred to the condition sleep apnoea; they realised that one of their adult patients had the condition, and set about working out what caused it and how to treat it.

Read recommended that Sullivan join University of Toronto Professor Eliot Phillipson to do postdoctoral work, including research on the sleeping pattern of specially trained dogs. “3 years of intensive study followed, looking at how breathing affected sleep, dreams, and responses. Leading to the important conclusion that failure of arousal during sleep was a key response lost during some patients with breathing problems”, Sullivan told The Lancet. Then, in 1979, Sullivan returned to the University of Sydney as a senior lecturer in respiratory medicine, where he remains today, and physician at the Royal Prince Alfred Hospital. By then, his focus was on sleep medicine, a specialism that had only a handful of specialist centres around globally. To investigate patients with suspected sleep apnoea, he borrowed a portable trolley with an array of biological amplifiers and other technology that Read was using to study babies. Those early studies involved much work through the night with Sullivan monitoring patients himself. But momentum built, more equipment was procured, and space was found in his university complex to properly study patients. Among the indicators studied were breathing rate, chest expansion, air pressure, and vital signs. “A key moment was the advent of the pulse oximeter to measure oxygen levels”, says Sullivan.

While initially only a few patients with sleep apnoea were discovered, an article on the subject in The Sydney Morning Herald prompted hundreds of phone calls to Sullivan’s team from people who thought they had the condition. Today, an estimated 9% of men and 5% of women have some form of sleep apnoea. Patients can appear well, but in sleep, they are choking, in some cases up to 500 times per night. Sufferers can end up falling asleep during daytime, including at the wheels of cars, and are at higher risk of hypertension and cardiovascular disease. “There will have been many cases of death recorded as arrhythmia or cardiovascular diseases that were actually sleep apnoea”, says Sullivan.

Sullivan and his team undertook experiments with dogs on airway obstruction, and created a mask for use on human patients. Air pressure was controlled with a circuit that raised pressure until passive obstruction of the airway was cleared. His first test patient was a 43-year-old construction worker who did not want a tracheostomy—back then the only treatment. At very low pressures, PAP cleared the man’s airway and allowed him to sink into a deeper sleep, as well as being sleep-free the next day. An elated Sullivan tried the technique on four other patients, and these findings formed the basis for his 1981 Lancet paper.

Yet even then, he considered PAP as a rescue therapy to delay or avoid tracheostomy, rather than a cure in itself. It was only when a patient requested a PAP device for selftreatment at home that Sullivan realised the potential of a mass-produced portable device. He patented his device, and joint-founded the company ResMed in Australia. By 1989, some 1000 patients in Australia alone were using home-based devices. Soon after the first early successful treatment of sleep apnoea, Sullivan extended the method to provide positive pressure ventilation during sleep in patients with severe respiratory failure in diseases such as emphysema, work that led to the now widespread use of this method. Much early work on the efficacy of PAP was done by Professor Sir Neil Douglas of Edinburgh University. Douglas, who is Chair of the UK’s Academy of Medical Royal Colleges, says that Sullivan “is the towering figure internationally in his field. Colin’s intellect is the most impressive that I have encountered in my career and his contributions to respiratory science and patient care have been immense”.

Another key area of Sullivan’s current research is using PAP to reduce sleep apnoea and resultant hypertension in sleeping pregnant women, with the theory that this will improve fetal wellbeing, and thus improve maternal and child morbidity and mortality outcomes. Hensley, a sleep medicine specialist and Professor of Medicine at the University of Newcastle, Australia, says: “Colin is a giant without equal in the field of sleep and breathing. In the 35 years that I have been a respiratory and sleep physician there has hardly been a day when I have not been influenced in my diagnosis or treatment by his work.”