| Unilateral diaphragmatic paralysis | Bilateral diaphragmatic paralysis |
Symptoms | Usually 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 |
PFT | VC ∼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 |
RME | MIP ∼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 ≤80 cmH2O in men, ≤70 cmH2O in women SNIP ≤70 cmH2O in men, ≤60 cmH2O in women |