[5] Guilleminault persuaded cardiologists John Shroeder and Ara Tilkian to spend nights in the hospital's clinical research center monitoring the systemic and pulmonary arterial blood pressure in sleeping patients.
In addition, he described the presence of OSAS in children, demonstrating its association with learning and attention problems along with cardiovascular derangements.
[10] Following this work, he went on to describe the presence of elevated upper airway resistance in children in 1982, emphasizing the symptoms of attention deficit, hyperactivity, and abnormal behavior during wakefulness and sleep, learning disabilities and sleepwalking, sleep terrors and enuresis that accompanied this form of sleep-related breathing disorder;[11] he described the same syndrome in adults and penned the term "upper airway resistance syndrome" (UARS) in adults.
[12] Finally, working in collaboration with Dr. William C. Dement, Guilleminault established the Apnea–hypopnea index (AHI), which is still in use today to characterize the presence and severity of sleep apnea.
He authored over seven hundred and forty (743) articles in peer-reviewed medical journals and won several awards for his research in the field of sleep medicine.