Original recordings of the respiratory belt signal (Resp), thoracic basal impedance (Z0), electrocardiogram (ECG), arterial blood pressure (AP), oxygen saturation (SpO2) as measured at the finger, and muscle sympathetic nerve activity (MSNA) in 1 diver. Note that the deflections in the top traces are caused by involuntary breathing movements during the struggle phase of apnea. These movements do not cause external gas exchange.