in these conditions the best thing would be regular suctioning of tracheostomy
tube. but if it is really unmanageable then you can try some transdermal patch
of scopolamine available only on doctor's prescription. you can ask your surgeon about this and if he thinks appropriate, you can get it advised.
another thing you can do is using a mucolytic agent
like guaifenecin or ambroxol nebulization to thin down the secretions so that they can be taken out easily, but only after discussing with your doctor.
and chest physiotherapy
is the best way to keep the airway patent and this also helps in recruitment of collapsed lungs.
hope my advice helps you
Dr. Amit Kumar