Table 3

Main differences between unilateral and bilateral diaphragmatic paralysis

Unilateral diaphragmatic paralysisBilateral diaphragmatic paralysis
SymptomsUsually asymptomatic
Possible dyspnoea on exertion and limited ability to exercise
Occasionally dyspnoea when supine
Unexplained dyspnoea or recurrent respiratory failure
Considerable dyspnoea at rest, when supine, with exertion, or when immersed in water above their waist
Fatigue, hypersomnia, depression, morning headaches and frequent nocturnal awakenings
Subsegmental atelectasis and infections of the lower respiratory tract
PFTVC ∼75% predicted
VC ∼55–65% predicted when supine
FRC usually preserved
TLC usually preserved
VC ∼50% predicted
VC ∼30–50% predicted when supine
TLC ∼70–79% predicted (mild restriction)
TLC ∼30–50% predicted (moderate-to-severe restriction)
RV >predicted
RMEMIP ∼30–60% predicted
SNIP ∼30–60% predicted
MIP <30% predicted
SNIP <30% predicted
Threshold values to suspect diaphragmatic weakness:
MIP or sniff Pdi or Pdi,max ≤80cmH2O in men, ≤70cmH2O in women
SNIP ≤70cmH2O in men, ≤60cmH2O in women

RME: respiratory muscles evaluation. Please refer to the text for more details.