When hooked up to machine for a bypass one's heart and lungs are not doing anything and this can cause some debilatation of the lung functionality. Also, a patient can be put at a risk for pneumonia or other respiratory problems. Sometimes a lung will collapse and requires breathing exercises to get the lungs working properly. With that ruled out, it may be the sob is part of the recovery process.
My brother-in-law had shortness of breathe and told it was normal after bypass, the lungs are healing and must get build back up. There is some deconditioning associated with a hospital stay and takes time, walking everyday a little helps. Your husband should have had exericises that was done to help increase the lungs capacity and strength.
Hope this helps, and thanks for sharing. Take care,
Ken
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