We introduce change in pulse transit time (change in PTT: noninvasive intrathoracic pressure monitoring) as a new monitoring test of sleep apnea syndrome, which is being developed for clinical application. In addition, we report the kinetics of cardiogenic oscillation (CGO: noninvasive upper airway obstruction monitoring), which was published in this journal in 2003, and the response of the upper airway in clinical practice (under an endoscope). We also review diaphragmatic movement by abdominal echography (respiration generator monitoring).