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Table 2 Parameters of capnographic measurements

From: Diagnostic accuracy of capnovolumetry for the identification of airway obstruction – results of a diagnostic study in ambulatory care

Parameter   Presence of airway obstruction  
All (n = 1287) No (n = 916) yes (n = 371) Comparison between groups (p-value)
Slope phase 2, s2 (g/mol*l) 2.89 (2.12; 3.81) 3.04 (2.23; 3.92) 2.59 (1.85; 3.43) < 0.001
Slope phase 3, s3 (g/mol*l) 0.17 (0.10; 0.30) 0.16 (0.09; 0.27)) 0.21 (0.12; 0.34) 0.001
log(s3) −0.72 (−0.92; − 0.49) −0.74 (− 0.96; − 0.54) −0.64 (− 0.85; − 0.44) < 0.001
Ratio s3/s2 0.06 (0.04; 0.10) 0.05 (0.03; 0.09) 0.09 (0.05; 0.14) < 0.001
log(s3/s2) −0.96 (−1.05; − 0.82) − 1.00 (− 1.10; − 0.85) − 0.85 (− 1.00; − 0.72) < 0.001
alpha between s2 and s3 (°) 122.0 (116.0; 130.0) 120.5 (115.0; 127.0) 128.0 (119.0; 135.0) < 0.001
Volume phase 2 (ml) 108.0 (91.0; 128.0) 109.0 (91.0; 129.0) 106.0 (89.0; 127.0) 0.134
Volume phase 3 (ml) 537.0 (392.0; 783.0) 522.5 (373.0; 751.8) 599.0 (432.0; 858.0) 0.002
Area/volume phase 2 (g/mol) 0.28 (0.24; 0.32) 0.27 (0.23; 0.31) 0.29 (0.25; 0.34) < 0.001
Area/volume phase 3 (g/mol) 0.06 (0.05; 0.08) 0.05 (0.04; 0.07) 0.08 (0.06; 0.10) < 0.001
  1. The table shows median values and quartiles. The groups were compared with each other using the Mann-Whitney-U-test. For the explanation of parameters see Fig. 1. log(s3) is the logarithm (base 10) of the parameter s3, log(s3/s2) the logarithm (base 10) of the ratio s3/s2. Before taking the logarithm, the values of 0.03 and 0.05, respectively, were added to the parameter values in order to account for zero values and achieve a distribution being as close to normal as possible. The groups were statistically significantly different from each other in all parameters except volume phase 2