C72-30 Association of Exercise-induced Desaturation With Diffusion Capacity Amongst Different Respiratory Disorders

Abstract Rationale Pulmonary function tests (PFTs) are comprised of several measurements including the diffusing capacity of the lungs for carbon monoxide (DLCO), an indicator of gas transfer which variably predicts poor prognoses depending on the underlying disease. Desaturation studies measure capillary oxygen saturation during exercise. Patients who experience exercise-induced oxygen desaturation may experience a mortality benefit from ambulatory oxygen supplementation depending on their disease. There are few data on the relationship between PFTs and oxygen desaturation in patients with advanced lung disease. One study found that a DLCO of 55% of normal was moderately predictive of oxygen desaturation but suffered from very small sample size and inclusion of primarily ILD patients (Kaminsky et al.; 2007). Methods This retrospective cross-sectional study examined the association between oxygen desaturation during exercise and DLCO in 600 patients being evaluated in an outpatient chest clinic. 196 patients with complete PFTs and a desaturation study done within a period of 6 months were included. We evaluated associations between exercise-induced oxygen desaturation and DLCO within 3 subgroups of lung disease (normal, restrictive, and obstructive) as determined by PFTs. Additionally, secondary analyses examined associations between DLCO and PFTs (FVC, RV, TLC, FEV1/FVC, FEV1). Results Of the 196 patients, 43 (22%) demonstrated normal lung function by PFTs, compared with 102 (52%) with restrictive and 51 (26%) with obstructive lung physiology. Higher DLCOs were significantly negatively associated with reduced oxygen desaturation during exercise. After adjusting for confounders, each 1-liter increase in DLCO was associated with a 0.14% smaller desaturation (95% CI: -0.212 to -0.067, p 0.001). We found a statistically significant relationship between DLCO and desaturation (Figure 1; r = -0.35, p 0.001). This relationship was not significantly different amongst lung disease subgroups. Higher DLCO values were significantly associated with greater lung volumes and airflow measures, including FVC, RV, TLC, and FEV1. Conclusions This study confirms a significant correlation between reductions in DLCO and the degree of oxygen desaturation during exercise, regardless of underlying lung disease classification. These results support using DLCO not only as an indicator of gas transfer, but also as a predictor of exercise-induced oxygen desaturation that would require supplemental oxygen. This may obviate the need to perform desaturation studies for certain patients in the future. This abstract is funded by: None