COPD exacerbation, very severe COPD with hypoxemia at low altitude (FEV1/FVC <0.7, FEV1 <40% predicted, oxygen saturation on room air <92% at 750 m).
Comorbidities such as uncontrolled cardiovascular disease, i.e., unstable systemic arterial hypertension, coronary artery disease; previous stroke; OSA; pneumothorax in the last 2 months.
Internal, neurologic, rheumatologic or psychiatric disease including current heavy smoking (>20 cigarettes per day)
Known renal failure or allergy to acetazolamide and other sulfonamides

NCT03177811_exc_T1
Condition
COPD exacerbation
NCT03177811_exc_T2
Condition
COPD
NCT03177811_exc_T3
Qualifier
very severe
NCT03177811_exc_T4
Condition
hypoxemia
NCT03177811_exc_T5
Qualifier
low altitude
NCT03177811_exc_T6
Measurement
FEV1/FVC
NCT03177811_exc_T7
Value
<0.7
NCT03177811_exc_T8
Measurement
FEV1
NCT03177811_exc_T9
Value
<40% predicted
NCT03177811_exc_T10
Measurement
oxygen saturation
NCT03177811_exc_T11
Qualifier
room air
NCT03177811_exc_T12
Value
<92% at 750 m
NCT03177811_exc_T14
Condition
Comorbidities
NCT03177811_exc_T15
Condition
cardiovascular disease
NCT03177811_exc_T16
Qualifier
uncontrolled
NCT03177811_exc_T17
Condition
systemic arterial hypertension
NCT03177811_exc_T18
Qualifier
unstable
NCT03177811_exc_T19
Condition
coronary artery disease
NCT03177811_exc_T20
Condition
stroke
NCT03177811_exc_T21
Qualifier
previous
NCT03177811_exc_T22
Condition
OSA
NCT03177811_exc_T23
Condition
pneumothorax
NCT03177811_exc_T24
Temporal
in the last 2 months
NCT03177811_exc_T27
Condition
psychiatric disease
NCT03177811_exc_T28
Condition
rheumatologic disease
NCT03177811_exc_T29
Condition
neurologic disease
NCT03177811_exc_T30
Condition
Internal disease
NCT03177811_exc_T31
Observation
heavy smoking
NCT03177811_exc_T32
Multiplier
>20 cigarettes per day
NCT03177811_exc_T33
Condition
renal failure
NCT03177811_exc_T34
Condition
allergy
NCT03177811_exc_T35
Drug
acetazolamide
NCT03177811_exc_T36
Drug
sulfonamides