If the vapor we're breathing in is 90+% THC then why aren't I getting a stronger effect right on the inhale? I've seen concentrate hits on youtube, and how people react to those. If a vapor hit is almost pure THC, then the difference has to be a matter of volume and not concentration; that we aren't saturating our lungs with enough vapor.
From what I understand significance of depth kind of comes from an understanding of how your lungs are moving oxygen from the air into your blood. When you're sitting down and not moving, your blood pressure is lower and all those tiny tiny capillaries in your lungs aren't being filled near the middle and top (against gravity). There is more blood near the bottom of your lungs than near the top, creating a higher potential for gas exchange deeper. Breathing using your diaphragm is actually what we are supposed to be doing; it brings the air in more evenly and straight down. Breathing from your chest is inefficient in comparison.
To focus on breathing using your diaphragm, breath in "from your stomach," and attempt to keep your chest relatively still. On the exhale, flex your abdominal muscles. This strengthens your diaphragm, allowing you to create more force on your inhale. Abdominal breathing is widely recommended to increase oxygen absorption so it makes sense that it'd help here.
I tried combining these factors yesterday. Prior to the first hit on the tube I took a few good deep breaths of air. It gives me peace of mind taking in a good amount of oxygen before the vapor. With the Zap I've just been taking a very long slow drawn out hit but immediately after I clear the tube I use my diaphragm to inhale as much air as possible, creating as much force on the inhale as I can. The extra air and the force should in theory push the vapor further down in your lungs where there is more potential for gas exchange.
Yesterday, the first hit on the 2nd stem of the session with this method was something I've never experienced before. Entire body was buzzing immediately, and my vision almost went out completely. I exhaled after maybe 10 seconds and let out much less vapor than I was accustom to seeing after that duration. I got a little nervous about the vision. I didn't have any headache afterwards, which would have been a sign of a lack of oxygen.
These are all just my thoughts. Hopefully someone else can enlighten me further on my observations.
Have to agree with Progress; it's not exactly relaxing trying to create a lot of force on that inhale. But now you have me thinking that I was hyperventilating and that is why the effect was greater. I think was doing more of a focused breathing, but I guess it'd accomplish the same result to a degree. Do you know how hyperventilation increases absorption? By just allowing you to take a longer hit?