Flat tops mean there is airflow restriction in those breaths.
CAs show up as just a flat line as you are not breathing during one or trying too even though your air way is open.
OAs are usually flat line also but if you were watching yourself you would see you are trying to breath but your airway is obstructed
Not sure if pointy tops are better than rounded tops or vice versa myself LOL.
Think of what would happen if you were trying to breathe through a narrow soda straw. You'd start to inhale, but you'd quickly reach a point where the airflow can't get any higher, and you'd inhale at that rate for the rest of your breathing cycle. Your airflow graph looks like rectangular with a flat top.
Without the soda straw, your airflow rate will start slow, go higher, reach a peak, then drop off during the inhale cycle. Your airflow graph looks sort of like a rounded mountain top.
Flow limitations take many shapes due to the complicated nature of your respiratory system, but the basic idea of a square top vs. a sine wave is the simplest way to look at it.
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If it's midnight and a DME tells you it's dark outside, go and check it yourself.