What would a vq scan tell the doctor about air flow through the second part of the long?

About ventilation an: V/q scan can help to diagnose or rule out pulmonary embolism.Sometimes it is used to check before lung surgery to predict post op lung function.

Air flow: A VQ scan looks at ventilation, and perfusion(blood flow) to the lungs. In the ventilation scan, a patient will be asked to breath in either a fine mist, or a gas (xenon). The pattern on the image gives information about how well the lungs are ventilating and looks to see if there are areas which are not getting air. If the gas was used, we also get information about air trapping.

I'm not sure: What the "second" part of the lung" is, but you can gain a fair amount of information regarding lung function with any v/q technique. It's how you use that info that counts. The test is designed to look for blood clots, but can be used to determine air trapping, candidates for surgery, and functional status.