 More than two-thirds of patients undergoing surgery have sleep apnea, a chronic condition in which people stop breathing for short periods while asleep. And yet, sleep-disordered breathing has never been studied as a risk factor for complicating general anesthesia. A team of Japanese researchers suspected sleep apnea might make the process more difficult. After all, if someone were to experience apnea symptoms while under anesthesia, they might not get enough oxygen, and it could be dangerous. To investigate the issue, the group recruited patients with scheduled surgeries to test for sleep problems and track the efficiency of anesthesia. Before surgery, patients took part in a sleep study to see if they had sleep apnea or other sleeping problems. In obstructive sleep apnea, the airway becomes blocked, and a person will stop breathing temporarily. Over the course of a night, this might happen hundreds of times, disrupting sleep and raising the risk of heart disease. Other conditions also involve pauses in breathing that reduce the quality of shut-eye and increase cardiovascular risk. In the end, researchers identified about 40 people with varying degrees of disordered sleep. Another 40 people without apnea served as controls. During each patient's scheduled surgery, anesthesiologists injected general anesthetics and then used a one-handed technique to open the airway and secure a face mask for mask ventilation with a constant ventilator setting. Researchers monitored the success of the mask ventilation by measuring the tidal volume or the amount of air exhaled. Low volumes may indicate that patients are not getting enough oxygen, a potentially life-threatening event. The team found that patients with sleep-disordered breathing did exhale less air than control patients, but they were also heavier. After controlling for obesity, the difference in tidal volume was not significant. However, when the researchers compared the 20 most severe patients with controls, there was a significant reduction in tidal volume, suggesting mask ventilation during anesthesia is more challenging for these patients. Fortunately, the use of a two-handed mask procedure was usually able to increase the efficiency of the technique, although not always, particularly for obese patients and those who began to hit the limit of the amount of air they could exhale. The results indicate it might be useful for patients to be screened for sleep apnea prior to surgery and for anesthesiologists to try the two-handed approach with at-risk patients from the beginning. Future work exploring ways to identify and fix mask ventilation problems more quickly would also make general anesthesia safer for everyone.