Question: my mother in addition to having chronic fibrosing hypersensitive pneumonitis has hypoventilation with sleep apnea.
The cause of the hypoventilation is unknown, but it leads to respiratory type 2 failure for which she needs a non-invasive ventilator at night to overcome this condition. She is borderline obese. She also has controlled hypothyroid. The CHP means that she needs some oxygen, but she doesn't need much (ie only 0.5litre/ minute). When she was initially prescribed oxygen it was given as 2 litres/ minute. This I believe tipped her into frequent acidotic states (ie. she was drowsy, started hallucinating etc). She was frequently taken into hospital for this where instead of reducing the oxygen federate, the ventilator settings were continually adjusted upwards. In addition, during this time she suffered from severe restless legs during the night which was not diagnosed.

1) Could restless legs have caused the acidotic state. ie, the frequent bouts of restlessness caused by legs beating cause her sufficient fatigue such that hypoventilation became even more severe.
2) It is noted by junior doctors that by reducing the oxygen federate, mums condition actually improved which suggests that reducing oxygen has some effect in the chemoreceptors. I read somewhere that excessive oxygen reduces the drive to breath. However, they still continued to adjust the ventilator settings upwards.
3) Eventually, the oxygen was reduced to the present 0.5litres/ minute. Nonetheless, the acidosis still continued, due to I believe the restless legs.
4) Eventually, it was me that discovered the restless legs and also discovered that only small doseages of ropinrole almost eradicated the restless legs. Since then there has been no acidosis recorded.
Therefore my question is:
a) does excessive oxygen of 2litres/ minute which is 4 times the required amount could have led to the frequent acidosis states
b) is it also possible that restless legs significantly contributed to acidosis, due to the fatigue caused by the syndrome
c) how dangerous is the acidosis condition and to what extent are pulmonary consultants aware that excessive oxygen of only 2 litres/ minute could lead to acidosis. There must be a proper way of assessing the correct doseage of oxygen rather than leaving the patient to suffer with frequent acidosis and then just making continuous adjustments to the ventilator which makes a temporary difference within a hospital environment. Please highlight what the correct way of arriving at the correct oxygen level for person with my mothers condition. Would a sleep study have helped to identify the correct doseages. This I am suggesting because I am aware th hypoventilation

You have not the answered the main question, which is

can excessive oxygen which in this was 2litres/ minute could be the cause of
frequent acidosis. If you have copd, excessive oxygen can cause acidosis.
However, in this case it is an ILD which drives the hypoxia, I agree, but even in
this case, could the excessive oxygen cause the acidosis. I read somewhere the
increased oxygen reduces the respiratory drive. this combined with the sleep
apnea would lead to acidosis.

you have also said that restless leg syndrome does not cause acidosis. However,
is it not possible that the secondary effects caused by very severe restless leg syndrome (which initially could also be due to peripheral hypoxia) could cause fatigueness of the thoriac muscles, and therefore increase hypoventilation

Although 2 litres/ minute is not high flow.

The important point is if 0.5litres/ minute is enough to give a rest saturation of 94% or above, why give 2 litres/ minute.

Mum's condition is such that she de-saturates on exertion, ie whilst walking and whilst sleeping due to the apnea, which is why she needed the oxygen. The 0.5 litres/ minute is sufficient for her to compensate during sleep.

What I find troubling about your answer, is that you say that 2litres/ minute is given routinely. So although this be suitable for a vast number of patients, in mum's case due to her 'hypoventilation' which I believe could also be true during
awake periods, it would be necessary to be very careful with the oxygen. You have not mentioned the effects of hypoventilation.

How would you test for hypoventilation during the awake and sleep periods. Is this simply the blood gas tests?

You say the worsening sleep apnea would lead to restless legs, which would suggest that mechanical ventilation has not been properly corrected. Although, this could be a conclusion that could be drawn, except that

the etiology of restless leg syndrome is multi-faceted and neurological. If mum already had long standing problems with restless legs then the above is not true. What actually has happened is that on administration of the drug ropinrole, the restless legs have been compensated for. Ever since the administration of such a drug three years ago, the problem of acidosis has not come up on any hospital admission.

This suggests to me, that the sleep apnea has not worsened and that ventilation
without taking into account restless legs (ie compensating for) would have continued to lead to restless legs, although it is not clear how restless legs on its
own affects ventilation. I believe it could be a neurological thing which affected
respiratory drive and hence the hypoventilation, but this is just a belief,
based on my observations. I'm not a medic