Posted by Craig on March 27, 2002 at 16:16:08:In Reply to: pickwickian patient posted by steve on February 13, 2002 at 02:54:37:
On of the keys with Bilevel positive pressure therapy is that the EPAP should be greater than the "apnea threshold." commonly, BiPAP senses inspiration by a decrease is pressure of system which it interprets as the patient "pulling in air." It uses this as a signal to increase the pressure form the EPAP to the IPAP.
Unfortunately, if you have full airway occlusion (apnea) respiratory effort does "pull in air" and signal the BiPAP machine to deliver the higher IPAP set pressure level.
So even though with the settings of 22/7 mm Hg you are theoretically providing the patient with a "pressure support" of 15 mm Hg, he may not be receiving this pressure support because he cannot trigger the machine. (7 mm Hg may not be enough to prevent full airway closure on this 400 lb man.)
His persistant desaturations may be from both the incompletely treated OSAs and the incompletely treated OAHs.
Before abandoning BiPAP, I would try:
1. Repeat titration to ensure that the EPAP pressure is above the "apnea threshold."
2. Placement of a back up rate on the BiPAP to ensure that he does get the pressure assistance.Remember that is Noninvasive positive pressure fails, there are other options:
1. ENT surgery (including going straight to tracheostomy with the severity of his desaturations or other surgeries with the plan that BiPAP may be required in addition.)
2. Dental prosthetic (to be used in addition to the BiPAP therapy. Combining the modalities to open the airway to more effectively delivery the "pressure support.")