Pulmonary function and sleep disordered breathing in patients with traumatic tetraplegia: a longitudinal study

The purpose of this study was to determine longitudinal changes in nocturnal blood gas tensions in individuals with stable traumatic tetraplegia. Ten individuals initially evaluated at least 6 months postinjury were reevaluated 5 years later. When initially evaluated, all the patients had normal daytime blood gases. Six (60%), however, had nocturnal oxyhemoglobin desaturations (dSATs) below 90%, 3 (30%) had mean nocturnal oxyhemoglobin saturation (SAT) below 90% for 10% or more of at least 1 hour, and 4 had maximum end-tidal carbon dioxide tensions (EtCO2) greater than 45mmHg. At 5-year follow-up evaluation, then a mean of 11.6 +/- 5.7 years postinjury, the vital capacities (VCs) of these individuals had improved significantly by a mean of 1242 +/- 545mL without treatment, and daytime blood gases were still normal for 9 out of 10 patients. Five of the individuals (50%), however, had an increased number of transient nocturnal dSATs and 8 of 9 (88%) re-studied by capnography were hypercapnic. We conclude that nocturnal dSAT and hypercapnia appear to be common in tetraplegia and may increase as the patient ages, despite significant increases in VC. Oximetry and capnography are useful in diagnosing nocturnal dSAT and in monitoring treatment.