SESSION TYPE: Physiology/PFTs/ Rehabilitation Posters
PRESENTED ON: Wednesday, October 24, 2012 at 01:30 PM - 02:30 PM
PURPOSE: Diffusion across the blood-gas barrier is one of the parameter used to assess the lung function. There is no consensus about the use of DLCO or DLCO/VA to measure diffusion capacity of the lung. Alveolar-arterial gradient (A-a gradient) is an indirect measurement of diffusion. We conducted retrospective analysis to study the relationship of DLCO and DLCO/VA with the Alveolar-arterial gradient.
METHODS: We retrospectively collected the data of pulmonary function test (PFT). Data were collected for the patients with acceptable arterial blood gas analysis (ABG). Δ A-a gradient was calculated by subtracting calculated A-a gradient from expected A-a gradient for age. DLCO and DLCO/VA were graded as mild, moderate and severe if values were 61-80%, 41-60% and ≤ 40% of predicted respectively. Δ A-a gradient was graded as 10-20, 20-30 and >30.
RESULTS: 195 patients met the inclusion criteria. 98 (50.3%) of patients were female. Age range included 21-93 years with mean age of 57.45 years. Majority of the patients (79.5%) were African American. Mean % predicted DLCO (DLCO %) was 63.29 and mean % predicted DLCO/VA (DLCO/VA %) was 84.72. Mean Δ A-a gradient was 14.05. 28 patients (14.4%) had DLCO higher than DLCO/VA and 163 (83.6%) had DLCO lower than DLCO/VA. Reduction in DLCO% was mild in 51, moderate in 46 and severe in 44 patients. Reduction in DLCO/VA% was mild in 41 patients, moderate in 29 patients, severe in 12 patients. Δ A-a gradient was between 10 and 20 in 76 patients (39%), between 20 and 30 in 78 (40%) patients and more than 30 in 41 (21%) patients. For Δ A-a gradient between 10-20- only 31.6% of patients with had normal DLCO as compared to 68.4% with normal DLCO/VA. Similarly for Δ A-a gradient between 20-30- only 28.2% of patients had normal DLCO as compared to 60.3% patients with normal DLCO/VA. For Δ A-a gradient of >30- only 19.5% of patients with had normal DLCO as compared to 34.1% with normal DLCO/VA. P values for Chi square test for all these results were <0.05.
CONCLUSIONS: Our study shows that DLCO/VA has statistically significant higher false normal rate when A-a gradient is increased as compared to DLCO.
CLINICAL IMPLICATIONS: Our study suggests that DLCO should be used preferentially for grading the severity of diffusion abnormalities.
DISCLOSURE: The following authors have nothing to disclose: Setu Patolia, Saurav Pokharel, Neerja Gulati, Rakesh Vadde, Muhammad Perwaiz, Dharani Narendra, Swati Patolia, Frances Schmidt, Danilo Enriquez, Joseph Quist
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