Table 1.

Preoperative Patient Characteristics

	Before PS Matched				After PS Matched
	Historical Control Group	Technical Improvement Group	P -value	SMD	Historical Control Group	Technical Improvement Group	P -value	SMD
N	177	281			143	143
Age	62.10±7.72	62.98±7.56	0.147	−0.114	62.89±7.19	62.80±7.90	0.757	0.012
BMI	26.17±3.02	25.89±2.87	0.329	0.092	26.13±3.11	25.98±2.83	0.707	0.047
Female Sex	46 (26.0)	59 (21.0)	0.216	0.114	32 (22.4)	32 (22.4)	>0.999	0
Hypertension	117 (66.1)	181 (64.4)	0.712	0.036	95 (66.4)	97 (67.8)	0.801	−0.03
Diabetes	59 (33.3)	96 (34.2)	0.855	−0.018	47 (32.9)	51 (35.7)	0.618	−0.059
Smoking	44 (24.9)	77 (27.4)	0.548	−0.059	34 (23.8)	33 (23.1)	0.889	0.016
Stroke	16 (9.0)	23 (8.2)	0.75	0.03	13 (9.1)	10 (7.0)	0.514	0.073
COPD	8 (4.5)	7 (2.5)	0.235	0.098	2 (1.4)	3 (2.1)	>0.999	−0.034

Abbreviations: PS, propensity score; BMI, Body Mass Index; COPD, chronic obstructive pulmonary disease.