Objective:To explore the epidemiological characteristics and treatment outcomes of patients with inhalation injuries combined with total burn area less than 30% total body surface area (TBSA).Methods:A retrospective observational study was performed on medical records of 266 patients with inhalation injuries combined with total burn area less than 30%TBSA who were admitted to the First Affiliated Hospital of Naval Medical University from January 2008 to December 2016 and met the inclusion criteria. The following statistical data of the patients were collected, including gender, age, injury site, injurious factors of inhalation injury, degree of inhalation injury, combined total burn area, tracheotomy, time of tracheotomy, mechanical ventilation, whether stayed in intensive care unit (ICU) or not, microbial culture results of bronchoalveolar lavage fluid, length of hospital stay, length of ICU stay, mechanical ventilation days, and respiratory tract infections. Single factor and multivariate linear regression analysis were used to screen out the risk factors impacting the length of hospital stay, length of ICU stay, and mechanical ventilation days of patients. Single factor and multivariate logistic regression analysis were used to screen out the risk factors impacting respiratory tract infections of patients.Results:The 266 patients included 190 males and 76 females, with the majority age of above or equal to 21 years and below 65 years (217 patients). The major injury site was confined space. The major factor causing inhalation injury was hot air. Mild and moderate inhalation injuries were more common in patients. The combined total burn area was 9.00% (3.25%, 18.00%) TBSA. In 111 patients who had tracheotomy, most of them received the procedures before being admitted to the First Affiliated Hospital of Naval Medical University. The length of hospital stay of patients was 27 (10, 55) days. The length of ICU stay of 160 patients who were hospitalized in ICU was 15.5 (6.0, 40.0) days. The mechanical ventilation days of 109 patients who were conducted with mechanical ventilation were 6.0 (1.3, 11.5) days. A total of 119 patients were diagnosed with respiratory tract infections, with 548 strains including 35 types of pathogens isolated, mainly Gram-negative bacteria. Single factor linear regression analysis showed that age, injurious factors of inhalation injury, combined total burn area, degree of inhalation injury (moderate and severe), tracheotomy, mechanical ventilation, and respiratory tract infections were the factors impacting the length of hospital stay of patients ( β=-0.198, -0.224, 0.021, 0.127, 0.164, -0.298, 0.357, 0.447, 95% confidence interval (CI)=-0.397--0.001, -0.395--0.053, 0.015-0.028, 0.009-0.263, 0.008-0.319, -0.419--0.176, 0.242-0.471, 0.340-0.555, P<0.1). Multivariate linear regression analysis showed that with mechanical ventilation and respiratory tract infections were the independent risk factors impacting the length of hospital stay of patients ( β=0.146, 0.383, 95% CI=0.022-0.271, 0.261-0.506, P<0.05 or P<0.01). Single factor linear regression analysis showed that injurious factors of inhalation injury, combined total burn area, degree of inhalation injury (moderate and severe), tracheotomy (no tracheotomy and prophylactic tracheotomy), mechanical ventilation, and respiratory tract infections were the factors impacting the length of ICU stay of patients ( β=0.225, 0.008, 0.237, 0.203, -0.408, -0.334, 0.309, 0.523, 95% CI=0.053-0.502, 0.006-0.010, -0.018-0.457, -0.022-0.428, -0.575--0.241, -0.687--0.018, 0.132-0.486, 0.369-0.678, P<0.1). Multivariate linear regression analysis showed that with respiratory tract infections was the independent risk factor impacting the length of ICU stay of patients ( β=0.440, 95% CI=0.278-0.601, P<0.01). Single factor linear regression analysis showed that injury site, injurious factors of inhalation injury (smoke and chemical gas), combined total burn area, degree of inhalation injury (moderate and severe), tracheotomy (no tracheotomy and prophylactic tracheotomy), and respiratory tract infections were the factors impacting mechanical ventilation days of patients ( β=-0.300, 0.545, 0.163, 0.005, 0.487, 0.799, -0.791, -0.736, 0.300, 95% CI=-0.565--0.034, 0.145-0.946, 0.051-1.188, 0.001-0.009, 0.127-0.847, 0.436-1.162, -1.075--0.508, -1.243--0.229, 0.005-0.605, P<0.1). Multivariate linear regression analysis showed that smoke inhalation, severe inhalation injury, and respiratory tract infections were the independent risk factors impacting mechanical ventilation days of patients ( β=0.210, 0.495, 0.263, 95% CI=0.138-0.560, 0.143-0.848, 0.007-0.519, P<0.05 or P<0.01). Single factor logistic regression analysis showed that age, injury site, combined total burn area (10%-19%TBSA and 20%-29%TBSA), degree of inhalation injury (moderate and severe), tracheotomy (prophylactic tracheotomy and no tracheotomy), and mechanical ventilation were the factors impacting respiratory tract infections of patients (odds ratio=1.079, 0.815, 1.400, 1.331, 1.803, 1.958, 0.990, 0.320, 3.094, 95% CI=0.840-1.362, 0.641-1.044, 1.122-1.526, 1.028-1.661, 1.344-2.405, 1.460-2.612, 0.744-1.320, 0.241-0.424, 2.331-4.090, P<0.1). Multivariate logistic regression analysis showed that with mechanical ventilation was the independent risk factor impacting respiratory tract infections of patients (odds ratio=4.300, 95% CI=2.152-8.624, P<0.01). Conclusions:The patients with inhalation injuries combined with total burn area less than 30%TBSA are mainly young and middle-aged males. Smoke inhalation, degree of inhalation injury, with mechanical ventilation and respiratory tract infections are the factors that affect the outcomes of patients with inhalation injuries combined with total burn area less than 30%TBSA. Additionally, prophylactic tracheotomy shows its potential value in reducing respiratory tract infections in patients with moderate or severe inhalation injuries.