- Figure 5
Effect of Obstructive Apneas on Stroke Volume in a Patient with Heart Failure
FIG. 5: What are the cardiac consequences of negative intrathoracic pressure? This Figure shows tracings from a patient with cardiomyopathy and OSA, who participated in a study at our center.[2] Again, there are episodes of paradoxical motion of the rib cage and abdomen during the apnea, with SaO2 falling during each of these episodes. Just above the SaO2 tracing are two blood pressure tracings measured by digital photoplethysmography (Portapres; Finapres Medical Systems), which calculates beat-to-beat stroke volume using a proprietary algorithm.
The Figure shows a ventilatory period, after which the patient begins to experience obstructive apnea and there is a progressive fall in stroke volume accompanied by a progressive fall in blood pressure (presumably due to that fall in stroke volume). Then at the end of the apnea the patient wakes, the airway opens, and blood pressure and stroke volume rise again.
This indicates that obstructive apneas in a patient with heart failure cause very substantial reductions in stroke volume and accompanying reductions in blood pressure, followed at the end of the event with blood pressure and stroke volume rising again.
References
Yumino D, Kasai T, Kimmerly D, et al. Differing effects of obstructive and central sleep apneas on stroke volume in patients with heart failure. Am J Respir Crit Care Med. 2013;187:433–438.
