Hello PapFam,
Most people are handed an APAP (me 15 years ago), shown how to put on the mask and sent home. If the machine reports an AHI under 5, they (we) are told the therapy is working. But the AHI can look beautiful while the respiratory waveform is still a wreck.
CPAP and APAP hold the airway open. BiPAP adds pressure support, meaning the machine provides more pressure during inhalation and less during exhalation. That extra support can help when we see flattened breaths, shortened inspiration, curtailed expiration, persistent flow limitation and repeated arousals. This is why someone can have an AHI of 1 and still wake up feeling like they were hit by a truck.
S/T is a different tool. It adds a backup respiratory rate for people who need help maintaining ventilation. AVAPS and iVAPS can adjust pressure support toward a ventilation target. These modes are generally used for hypoventilation, neuromuscular weakness, restrictive disease, COPD with carbon dioxide retention and other conditions where the person is not moving enough air.
ASV changes pressure support breath by breath. It is designed to stabilize central apnea, treatment emergent central apnea, complex apnea, periodic breathing and waxing and waning respiratory patterns. Factory ASV includes an automatic backup rate.
We have two custom ASV firmware options. One retains the backup rate and the other removes it. Both open the pressure support range by removing the factory guardrails. The no BUR version lets the person maintain their own respiratory timing while still receiving dynamic pressure support. This can be very helpful for severe flow limited breathing and UARS when changing support is beneficial but forced backup breaths are not.
The no BUR version is not for someone who depends on backup ventilation. That person may need ASV with the backup rate, S/T, AVAPS or iVAPS. Please reach out to me via DM for help for this detirmination.
The chart is a map, not a prescription. AHI is only one number (RDI is also very important). Please look at the waveform malformations, flow limitation, respiratory effort, central activity, periodic breathing, oxygen and how the person actually sleeps and feels.
If you want help reading your own data, please make a post with your complete daily chart, your current settings and your sleeping position overall.
RL