Michael Tallhamer, MSC, DABR
You may be seeing the results in different body mechanics due to different types of breathing during the breath hold
i.e. Diaphragmatic (belly), Thoracic (chest expansion minimal diaphragm drop), Clavicular (upper lung only) or Paradoxical (chest compression during breath) breathing.
You may need to do additional breath coaching with these patients to ensure they are taking the same type of breath as during CT.
A good practice is to tell them to take a slow breath in through their nose until the naturally stop breathing (filling their lung volume without a gasping style breath). Then when they reach max inhale stop there. This requires very minimal effort, fills the lung volume more completely, helps them hold their breath longer, and requires no additional muscle exertion to help keep the breath in.
In that position you can then instruct them to fill “a little bit more” or “let a little out” to dial in the anatomy without fear of them not being able to accommodate as this is a fairly comfortable position for them and with a little extra effort they should be able to accommodate either request.
Hope that helps.