Your inspiratory flow during this period where there is no apparent chin-tucking, has characteristic mild flow limitation which is described in this wiki article
http://www.apneaboard.com/wiki/index.php...limitation You are achieving normal tidal volume in a normal inspiratory period, but there is some slowing of the inspiratory flow. This is not something we need to correct, but inspiratory flow might be further rounded by higher pressure support of a longer duration of IPAP pressure. We cannot tell from your chart what the mask pressure is doing, and whether the plateau or decline in peak flow is related to a drop in IPAP pressure or restriction in the airway.
Where flow limitation is more severe, we normally resolve flow limitation by using additional pressure support, however you have expressed concerns about using higher pressure or pressure support. Your inspiratory flow curve often shows a good strong initial flow increase to a sharp peak followed by a decrease in flow with no secondary or tertiary flow peaks. This suggests as you approach peak flow rate, your inspiratory effort rapidly diminishes and inspiratory flow declines until you expiration begins. During chin-tucking, we would see much greater flow limitation as inspiratory flow is squashed by the obstruction. You can see an example of this looking at your 12/10/22 chart closeup at 20:10:30.
Some studies have attempted to classify flow limitation
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4688581/ and your flow is described as a Type 4 Flow Limitation where there is a peak during the initial phase followed by a plateau. This suggests initial effective phasic upper airway dilation with a slowing of inspiratory flow. This is a borderline FL and may not interfere with normal respiratory volume or effort.
Table 1
Classes of inspiratory flow shapes.
Class Description Interpretation Flow limitation
1 Sinusoidal Normal inspiration No
2 Two peaks during inspiration Upper airway reopening after initial collapse Yes
3 Three or more (tiny) peaks Soft-tissue vibration during inspiration Yes
4 Peak during the initial phase followed by a plateau Initial opening indicates effective phasic upper airway dilation Yes/No
5 Peak at midinspiration with plateau on both sides Significance uncertain; intensive phasic muscle activity at midinspiration (?) Yes
6 Peak during late phase preceded by a plateau Marked tracheal traction support during lung inflation Yes
7 Plateau throughout inspiration Collapse of noncompliant upper airway Yes