Tremors in GBS

Hi,

My father (65yo) has been diagnosed with a rather severe case of GBS about 7 weeks ago. As described in numerous cases I have read, his situation deteriorated during the first 2-3 weeks; paralysis spread quickly from the lower limbs to full paralysis excluding some movement in the shoulders and face, and respiratory failure. He was put on mechanical ventilation at the ICU within a week from hospital admission and is still there; after the first 3 weeks his situation has stabilized, and in the last week we even see some improvement (better facial muscle control, fewer extreme blood pressure fluctuations). His only complication until now was pneumonia that has resolved about 3 weeks ago with antibiotics.

In the last 48 hours he has started to shake involuntarily in the muscles where he still has some control: shoulders, upper chest and face; this causes tremor in the entire upper body. His temperature is climbing (37.5c, going up slowly) and so is HR (this evening 120, his normal is 75-85). Finally, his breathing changed mode: form being dependent on machine ventilation only (16 per minute, 0.550 volume) he now takes 20-25 breathes overall (SIMV mode - 16 machine breathes and 5-10 assisted ones), but still with a volume of ~10 liters/minute. Doctors dismiss all this as nervousness, but together with other symptoms such as memory loss (does not remember in the evening that he was visited at noon etc), I find it concerning. Also, maybe it is just my feeling but the "weekend ICU doctors" seem to be less professional than the regular ones, they are interns, not neurologists, and you can see their inexperience in the little things (like finding a vein).
Having said all this, the tremors result in substantially more bodily movement than was exhibited before, and my father does not complain about pain (at least not more than usual).

Are the tremors related to the recovery process? If not, what can be the underlying cause? How important is it to have a "regular" amount of breathes (say, about 15/minute with a volume of 600ml each) and not many shallow ones? Is there anything particular I should be on the watch for?

Thanks!!
P