FIG. 23:  This Figure illustrates the case of a patient with Op-CSA who demonstrated cyclical CSA and who was tried with oxygen, CPAP, and ASV.^[14] The patient had an excellent response with oxygen (Panel A), with normalization of the SPO₂ and elimination of CSA.  On the other hand, CPAP (Panel B) was completely ineffective, failing to reduce with OSA as expected, or CSA.  Finally, ASV (Panel C) was also ineffective.  ASV eliminated apneas, largely based on the backup rate, which was the factor in depressed efforts, but the ASV machine was oscillating, delivering pressures throughout the night.  In CSR (where ASV has shown success), or in cases of high loop gain, the ASV does not typically work very hard.  It may oscillate pressures initially, to correct for the high loop gain, but it should eventually stabilize the respiratory system so that the pressure support algorithm usually does not need to be activated for the rest of the study.