ABSTRACT
OBJECTIVES: Determine the prevalence of suboptimal peak inspiratory flow rate (PIFR) and associated patient characteristics and compare PIFR measurements obtained with spirometry and In-Check DIAL® device in ambulatory patients with COPD. METHODS: Patients underwent PIFR measurement with In-Check DIAL® device and pulmonary function testing with calibrated equipment. Group characteristics and lung function were compared for patients with suboptimal (≤ 60 L/min) and optimal (> 60 L/min) PIFR. Receiver operating curve analysis determined the best maximal forced inspiratory flow (FIF max) value in identifying optimal PIFR by gender and height. RESULTS: From July 1, 2016 to January 31, 2018, a total of 303 patients with chronic obstructive pulmonary disease (COPD) had PIFR and pulmonary function measurements. Group mean age was 65.5 ± 11.3 years with equal gender distribution. Suboptimal PIFR was observed in 61 (20.1%) patients. A significant correlation was observed between PIFR and FIF max, inspiratory capacity and residual volume (RV) to total lung capacity (TLC) ratio. In the suboptimal PIFR group, mean FIF max measured by spirometry was significantly less compared with the optimal PIFR group; 178.5 ± 56.9 L/min and 263.4 ± 89.9 L/min, respectively (p<0.0001). Receiver operator curve analysis of FIF max to identify an optimal PIFR yielded an area under the curve of 0.79. Males < 65 inches had a suboptimal PIFR in 16.7 % of the male cohort, while females < 65 inches had a suboptimal PIFR in 27.4 % of the women. CONCLUSIONS: Suboptimal PIFR was present in 1 in 5 stable patients with COPD and was more frequent in short statured females. Spirometry determined FIF max was associated with PIFR based on gender and height.
ABSTRACT
An essential step in understanding the molecular basis of protein-protein interactions is the accurate identification of inter-protein contacts. We evaluate a number of common methods used in analyzing protein-protein interfaces: a Voronoi polyhedra-based approach, changes in solvent accessible surface area (DeltaSASA) and various radial cutoffs (closest atom, Cbeta, and centroid). First, we compared the Voronoi polyhedra-based analysis to the DeltaSASA and show that using Voronoi polyhedra finds knob-in-hole contacts. To assess the accuracy between the Voronoi polyhedra-based approach and the various radial cutoff methods, two sets of data were used: a small set of 75 experimental mutants and a larger one of 592 structures of protein-protein interfaces. In an assessment using the small set, the Voronoi polyhedra-based methods, a solvent accessible surface area method, and the closest atom radial method identified 100% of the direct contacts defined by mutagenesis data, but only the Voronoi polyhedra-based method found no false positives. The other radial methods were not able to find all of the direct contacts even using a cutoff of 9A. With the larger set of structures, we compared the overall number contacts using the Voronoi polyhedra-based method as a standard. All the radial methods using a 6-A cutoff identified more interactions, but these putative contacts included many false positives as well as missed many false negatives. While radial cutoffs are quicker to calculate as well as to implement, this result highlights why radial cutoff methods do not have the proper resolution to detail the non-homogeneous packing within protein interfaces, and suggests an inappropriate bias in pair-wise contact potentials. Of the radial cutoff methods, using the closest atom approach exhibits the best approximation to the more intensive Voronoi calculation. Our version of the Voronoi polyhedra-based method QContacts is available at .
