1. permissive hypercapnia improves peripheral circulation and prevent lung damage, it also stimulate ventilation

2. more important avoid any use of opioids during anesthesia or sedation by using sympathetic block by locoregional or systemic drugs.

Yes. Vibroacoustic stimulation (Whole bode vibration) using MULTIVIB mattress and amplitude varied frequencies will often improve breathing difficulties. As VAT is non invasive it can be used simultanepously with other approaches. I have made special frequencies for lung issues. Duratkion of session : 23 min. No known adverse side effects. Can be used multiple times daily for as long as needed. Effective frequency area is 50 - 70 Hz.

Intravenous aminophylline use or manual compression of laryngospasm notch can stimulate ventilation for a short time.

For those of you who maybe interested in holistic medicine, some anaesthetist use in animal an acupuncture point which, apparently may help with ventilation: GV 24...but it seems they use to stimulate breathing during recovery from anaesthesia, while weaning from the ventilator...not sure it will halp in terms of increasing ventilation in an alrady breathing aptient.

Very curious and unusual question, consequence of this very useful discussion because it is a matter of very  intriguing!