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Table 2 Patient characteristics of development set and validation set

From: Ultrasound assessment of the rectus femoris in patients with chronic obstructive pulmonary disease predicts poor exercise tolerance: an exploratory study

  Development set Validation set P value
n 108 46  
Age 64 (41–81) 65 (54–83) 0.62
Sex/male (%) 75 (69) 33 (72) 0.926
FEV1 (L) 1.54 (0.45–3.1) 1.63 (0.63–2.9) 0.424
FEV1%pred 58.12 (15.8–99.5) 62.38 (30.1–110.6) 0.263
FVC (L) 2.79 (0.98–5.21) 2.82 (0.92–4.75) 0.852
FVC% pred 80.14 (34.4–119.6) 82.72 (49.2–123.8) 0.671
FEV1/FVC 54.00 (31–68.59) 57.16 (32–68.98) 0.082
RV (L) 4.12 (1.97–7.31) 3.90 (1.34–6.43) 0.608
TLC (L) 6.55 (3.88–9.84) 6.14 (3.52–8.72) 0.316
RV/TLC (%) 75.58 (39–242.4) 68.53 (31–149.2) 0.522
BMI (kg/m2) 24.10 (11.3–37.3) 23.48 (17.2–30) 0.357
FFMI (kg/m2) 17.09 (9.5–23.8) 16.78 (11.8–19.3) 0.461
Height (cm) 165.42 (141–180) 165.40 (147–177) 0.991
Weight (Kg) 65.84 (26.7–110.4) 63.26 (40.2–90.3) 0.323
mMRC 2 (0–4) 2 (0–4) 0.599
CAT 15 (0–37) 14 (0–36) 0.804
RFthick (cm) 5.48 (4.51–6.97) 5.41 (4.5–6.96) 0.515
RFcsa (cm2) 7.06 (6.01–8.22) 7.03 (6.06–8.28) 0.78
6MWD (m) 370.8 (108–554) 365.9 (177–510) 0.721
QMS (kg) 42.89 (21.55–68.1) 42.94 (24.2–65.05) 0.986
  1. FEV1, Forced Expiratory Volume in the first second; FEV1% pred, FEV percentage predicted; FVC, forced vital capacity; FVC% pred, FVC percentage predicted; RV, residual volume; TLC, total lung capacity; BMI, body mass index; FFMI, fat-free mass index; CAT, COPD Assessment Test; 6MWD, 6-min walk distance; QMS, quadriceps muscle strength