Predicting prolonged postoperative ileus in gastric cancer patients based on bowel sounds using intelligent auscultation and machine learning

Table 2 Characteristics of patients in the training, internal validation and external validation groups, n (%)

Variable	Overall (N = 120)	Training (N = 84)	Validation (N = 36)	P value
Age (years)				0.291
≥ 70	40 (33.3)	25 (29.8)	15 (41.7)
< 70	80 (66.7)	59 (70.2)	21 (58.3)
Gender				0.291
Male	80 (66.7)	59 (70.2)	21 (58.3)
Female	40 (33.3)	25 (29.8)	15 (41.7)
BMI (kg/m2)				0.768
< 18.5	16 (13.3)	10 (16.7)	6 (8.3)
> 18.8 < 25	82 (68.3)	58 (18.1)	24 (18.8)
> 25	22 (18.4)	16 (65.3)	6 (72.9)
Smoking				0.078
Yes	46 (38.3)	37 (40.0)	9 (25)
No	74 (61.7)	47 (60.0)	27 (75)
Drinking				0.345
Yes	21 (17.5)	17 (20.2)	4 (11.1)
No	99 (82.5)	67 (79.8)	32 (88.9)
Hypertension				0.05
Yes	33 (27.5)	28 (33.3)	5 (13.9)
No	87 (72.5)	56 (66.7)	31 (86.1)
Diabetes				0.581
Yes	11 (9.2)	9 (10.7)	2 (5.6)
No	109 (90.8)	75 (89.3)	34 (94.4)
Previous abdominal surgery				0.885
Yes	26 (21.7)	19 (22.6)	7 (19.4)
No	94 (78.3)	65 (77.4)	29 (80.6)
Anemia				1
Yes	44 (36.7)	31 (36.9)	13 (36.1)
No	76 (63.3)	53 (63.1)	23 (63.9)
Hypoproteinemia				0.135
Yes	22 (18.3)	12 (14.3)	10 (16.8)
No	98 (81.7)	72 (85.7)	26 (72.2)
Preoperative potassium				1
Normal	108 (90.0)	76 (90.5)	32 (88.9)
Abnormal	12 (10.0)	8 (9.5)	4 (11.1)
Emergency surgery				0.444
Yes	3 (2.5)	1 (1.2)	2 (5.6)
No	117 (97.5)	83 (98.8)	34 (94.4)
Preoperative bowel preparation				0.784
Yes	114 (95.0)	79 (94.0)	35 (97.2)
No	6 (5.0)	5 (6.0)	1 (2.8)
Tumor size (cm)				0.693
< 5	76 (63.3)	52 (61.9)	24 (66.7)
≥ 5 < 10	36 (30.0)	27 (32.1)	9 (25.0)
≥ 10	8 (6.7)	5 (6.0)	3 (8.3)
Tumor site				0.627
Cardiac	21 (17.5)	13 (15.5)	8 (22.2)
Body	63 (52.5)	46 (54.8)	17 (47.2)
Antrum	36 (30.0)	25 (29.8)	11 (30.6)
Stage cTNM				0.537
0	17 (14.2)	11 (13.1)	6 (16.7)
I	20 (16.7)	13 (15.5)	7 (19.4)
II	32 (26.7)	25 (29.8)	7 (19.4)
III	43 (35.8)	28 (33.3)	15 (41.7)
IV	8 (6.7)	7 (8.3)	1 (2.8)
Surgical method				0.858
Open	33 (27.5)	24 (28.6)	9 (25)
Laparoscope	87 (72.5)	60 (71.4)	27 (75)
Range_of_excision				0.427
Distal	21 (17.5)	17 (20.2)	4 (11.1)
Proximal	53 (44.2)	37 (44.0)	16 (44.4)
Total	46 (38.3)	30 (35.7)	16 (44.4)
Operation time (min)				1
< 275	63 (52.5)	44 (52.4)	19 (52.8)
≥ 275	57 (47.5)	40 (47.6)	17 (47.2)
Anesthesia time (min)				0.803
< 365	43 (35.8)	29 (34.5)	14 (38.9)
≥ 365	77 (64.2)	55 (65.5)	22 (61.1)
RTBS (h)				0.144
< 15	92 (76.7)	68 (81.0)	24 (66.7)
≥ 15	28 (23.3)	16 (19.0)	12 (33.3)
NBS (cpm)				1
≥ 2.436	48 (40.0)	34 (40.5)	14 (38.9)
< 2.436	72 (60.0)	50 (59.5)	22 (61.1)
BSVA (dB)				0.964
< 44.793	88 (73.3)	61 (72.6)	27 (75.0)
≥ 44.793	32 (26.7)	23 (27.4)	9 (25.0)
FBS (Hz)				1
< 461.560	36 (30.0)	25 (29.8)	11 (30.6)
≥ 461.560	84 (70.0)	59 (70.2)	25 (69.4)

NBS: Number of bowel sounds; BSVA: Bowel sound vibration amplitude; FBS: Frequency of bowel sounds; RTBS: Recovery time of bowel sounds; BMI: Body mass index.