Skip to main content

Table 1 Baseline patients characteristics in the unmatched and propensity score-matched groups

From: Outcomes after helicopter versus ground emergency medical services for major trauma--propensity score and instrumental variable analyses: a retrospective nationwide cohort study

  Unmatched groups Matched groups
HEMS GEMS SD, % HEMS GEMS SD, %
n = 4128 (%) n = 17158 (%) n = 3980 (%) n = 3980 (%)
Age, years
 15 - 55 1586 (38.4) 6923 (40.3) 2.5 1536 (38.6) 1516 (38.1) -2.3
 56 - 64 708 (17.2) 2740 (16.0) 4.3 681 (17.1) 697 (17.5) 4.1
  ≥ 65 1834 (44.4) 7495 (43.7) -5.8 1763 (44.3) 1767 (44.4) -0.8
Sex male 3143 (76.1) 11906 (69.4) 16.4 3016 (75.8) 3039 (76.4) -1.2
Systolic blood pressure, mm Hga
  < 90 318 (7.7) 1120 (6.5) 5.9 309 (7.8) 315 (7.9) 2.7
 90 to 109 444 (10.8) 2078 (12.1) -2.6 436 (11.0) 456 (11.5) 1.0
  ≥ 110 2146 (52.0) 10614 (61.9) -23.9 2107 (52.9) 2105 (52.9) -1.2
 missing 1220 (29.6) 3346 (19.5) 26.0 1128 (28.3) 1104 (27.7) -0.9
Heart rate, beats/mina
  < 60 228 (5.5) 817 (4.8) 3.6 221 (5.6) 241 (6.1) -2.9
 60 to 99 2048 (49.6) 10144 (59.1) -21.8 2015 (50.6) 2109 (53.0) 1.2
  ≥ 100 851 (20.6) 3862 (22.5) -2.7 835 (21.0) 746 (18.7) 1.2
missing 1001 (24.2) 2335 (13.6) 29.0 909 (22.8) 884 (22.2) -1.0
Respiratory rate, breaths/mina
  < 10 or > 29 781 (18.9) 3030 (15.0) 10.2 770 (19.3) 743 (18.7) 0.8
 10 to 29 1818 (44.0) 13175 (65.3) -42.5 1805 (45.4) 1822 (45.8) -0.6
 missing 1529 (37.0) 3971 (19.7) 38.3 1405 (35.3) 1415 (35.6) 0.2
Japan Coma Scalea
 Grade 0 (alert) 913 (22.1) 4453 (26.0) -11.1 912 (22.9) 925 (23.2) 0.2
 Grade 1 (delirium) 925 (22.4) 5443 (31.7) -21.5 924 (23.2) 946 (23.8) 0.7
 Grade 2 (sommolence) 422 (10.2) 1788 (10.4) 0.7 420 (10.6) 398 (10.0) 2.6
 Grade 3 (coma) 901 (21.8) 4185 (24.4) -3.4 899 (22.6) 887 (22.3) -2.6
 missing 967 (23.4) 1289 (7.5) 43.9 825 (20.7) 824 (20.7) 0.0
Preexisting medical conditions
 Neurological diseases 373 (9.0) 2367 (13.8) -18.6 371 (9.3) 343 (8.6) 0.3
 Cardiovascular diseases 892 (21.6) 3676 (21.4) -6.4 858 (21.6) 853 (21.4) 1.2
 Respiratory disease 180 (4.4) 589 (3.4) 3.6 170 (4.3) 165 (4.1) 0.5
 Digestive diseases 274 (6.6) 1231 (7.2) -5.0 268 (6.7) 261 (6.6) 2.9
 Metabolic disease 407 (9.9) 1771 (10.3) -5.2 393 (9.9) 386 (9.7) 0.7
 Others 327 (7.9) 1116 (6.5) 0.7 301 (7.6) 271 (6.8) 0.0
Mechanism of injury
 Automobile crash 815 (19.7) 2085 (12.2) 23.8 752 (18.9) 756 (19.0) 0.0
 Motorcycle crash 618 (15.0) 2613 (15.2) 3.2 608 (15.3) 631 (15.9) -1.4
 Bicycle crash 270 (6.5) 2129 (12.4) -15.9 270 (6.8) 271 (6.8) 1.2
 Pedestrian traffic accident 294 (7.1) 1559 (9.1) -3.9 289 (7.3) 294 (7.4) 0.0
 Other vehicle 44 (1.1) 122 (0.7) 4.5 41 (1.0) 40 (1.0) 1.0
 Fall from high place or Stairs 1418 (34.4) 6366 (37.1) 1.5 1391 (34.9) 1366 (34.3) -0.4
 Machine injury 61 (1.5) 98 (0.6) 9.3 50 (1.3) 47 (1.2) -0.9
 Falling object or Explosion 100 (2.4) 283 (1.6) 6.7 98 (2.5) 89 (2.2) 0.0
 Compression injury 175 (4.2) 368 (2.1) 13.1 155 (3.9) 165 (4.1) 1.1
 Train 16 (0.4) 163 (0.9) -5.2 16 (0.4) 15 (0.4) 0.0
 Sports 96 (2.3) 182 (1.1) 10.5 91 (2.3) 91 (2.3) 0.7
 Other blunt injury 90 (2.2) 322 (1.9) 3.7 88 (2.2) 98 (2.5) -0.7
 Penetrating 62 (1.5) 336 (2.0) -2.4 62 (1.6) 55 (1.4) 0.0
 missing 69 (1.7) 532 (3.1) -7.8 69 (1.7) 62 (1.6) 0.0
Injury distribution with AIS ≥ 3
 Head 1963 (47.6) 9357 (54.5) -18.9 1916 (48.1) 1902 (47.8) -1.0
 Face 84 (2.0) 263 (1.5) 3.9 81 (2.0) 76 (1.9) 0.0
 Neck 24 (0.6) 115 (0.7) -1.4 24 (0.6) 21 (0.5) 1.4
 Chest 2294 (55.6) 8183 (47.7) 22.8 2197 (55.2) 2153 (54.1) 0.0
 Abdomen 552 (13.4) 1686 (9.8) 13.7 521 (13.1) 512 (12.9) -0.3
 Spine 916 (22.2) 2969 (17.3) 11.9 862 (22.5) 862 (21.7) 1.2
 Extremity 1208 (29.3) 4270 (24.9) 13.7 1144 (28.7) 1092 (27.4) 0.7
 Skin 8 (0.2) 26 (0.2) 3.3 7 (0.2) 8 (0.2) 0.6
Injury Severity Score
 16 to 24 1792 (43.4) 8685 (50.6) -19.7 1750 (44.0) 1817 (45.7) -4.4
 25 to 34 1421 (34.4) 5700 (33.2) 5.3 1370 (34.4) 1359 (34.1) 2.9
  ≥ 35 915 (22.2) 2773 (16.2) 19.2 860 (21.6) 804 (20.2) 2.0
Accident day
 Working day 2876 (69.7) 12343 (71.9) -5.3 2780 (69.8) 2745 (69.0) 1.9
 Weekend 1252 (30.3) 4815 (28.1) 5.3 1200 (30.2) 1235 (31.0) -1.9
  1. a recorded pre-hospital vital signs
  2. Total may not become 100% due to rounding off
  3. HEMS helicopter emergency medical services, GEMS ground emergency medical services, SD standardized difference, AIS abbreviated injury scale