Assessment of Pulmonary Restriction in Cervical Spinal Cord Injury: A Preliminary Report

Objective: To compare the prevalence of pulmonary restriction on the basis of a vital capacity (VC) below the lower limit of normal (LLN) and a normal or high forced expiratory volume in I second (FEV1)/VC ratio with the criterion standard of total lung capacity (TLC) less than LLN in individuals with spinal cord injury (SCI) and able-bodied (AB) controls. Design: Method comparison with criterion standard. Setting: University research center. Participants: Individuals with cervical SCI (n=12; injury level. C5-7) and AB controls (n=12) matched for age, stature, and body mass. Interventions: None. Main Outcome Measures: TLC via plethysmography; FEV1, and VC via spirometry; and maximum inspiratory and expiratory pressures (P-1max and P-Emax). Results: All participants with SCI exhibited a VC less than LLN and a normal-to-high FEV1/VC ratio, whereas significantly fewer (8 of 12) participants with SCI exhibited a TLC less than LLN (P=.046). For the AB group, no participant exhibited a VC or TLC less than LLN. Percent-predicted VC was lower than the percent-predicted TLC in SCI (P=.013), whereas percent-predicted VC was higher than percent-predicted TLC in AB controls (P=.001). Percent-predicted P-1max was higher than P-Emax in SCI (P=.001) but not AB controls (P=.146). Conclusions: A VC less than LLN with a normal-to-high FEV1/VC ratio does not accurately predict pulmonary restriction in cervical SCI. When using spirometry to infer pulmonary restriction in cervical SCI, we recommend using a VC below 60% of the AB predicted value.