Factors influencing on-scene time in a rural Norwegian helicopter emergency medical service: a retrospective observational study

Table 2 Factors affecting on-scene time (linear mixed effect model)

Predictor	Unadjusted model N = 1605			Fully adjusted model N = 1597			Final model^b N = 1599
Predictor	B	95% CI	p-value	B	95% CI	p-value	B	95% CI	p-value
Year in study period^a	−0.31	(−0.60, −0.01)	0.040	−0.43	(−0.72, −0.14)	0.004	−0.42	(−0.67, −0.16)	0.001
Daylight (yes)	0.00	(−0.84, 0.83)	0.992	0.34	(−0.39, 1.06)	0.367	–	–	–
Age	−0.01	(−0.03, 0.01)	0.310	0.03	(0.01, 0.05)	0.008	0.03	(0.01, 0.05)	0.005
Male gender (yes)	−0.16	(−1.04, 0.71)	0.713	−0.26	(−1.02, 0.50)	0.505	−0.26	(−1.02, 0.50)	0.504
Trauma (yes)	1.96	(1.04, 2.87)	<0.001	1.61	(0.59, 2.63)	0.002	1.60	(0.58, 2.62)	0.002
NACA score	3.88	(3.25, 4.51)	<0.001	1.44	(0.77, 2.11)	<0.001	1.44	(0.78, 2.11)	<0.001
Glasgow Coma Scale	−0.70	(−0.82, −0.58)	<0.001	0.02	(−0.14, 0.17)	0.838	0.02	(−0.14, 0.17)	0.846
Treatment prior to HEMS (yes)	−1.12	(−2.00, −0.23)	0.014	−1.68	(−2.46, −0.90)	<0.001	−1.68	(−2.46, −0.90)	<0.001
Experience (years as specialist)	−0.06	(−0.19, 0.08)	0.409	0.01	(−0.14, 0.15)	0.921	–	–	–
Analgesics (yes)	5.68	(4.86, 6.49)	<0.001	3.06	(2.24, 3.87)	<0.001	3.07	(2.25, 3.88)	<0.001
Intubation (yes)	12.41	(11.22, 13.60)	<0.001	9.75	(8.09, 11.41)	<0.001	9.71	(8.05, 11.37)	<0.001
Helicopter transport (yes)	1.68	(0.51, 2.86)	0.005	3.51	(2.40, 4.61)	<0.001	3.54	(2.44, 4.65)	<0.001

Patients with a NACA score of 4–6 and acute myocardial infarction, stroke, head injury, or penetrating torso injury (N = 1605) were included. ^aYear in study period refers to year 1–5 of the period from 2009 to 2013. ^bVariables chosen for final model included multivariate regression analyses of variables that differed significantly, in addition to age and gender. The fully adjusted model is an intermediate calculation step to select factors for the final model. Estimates were adjusted for HEMS base, and the individual physician was used as a random effect. B = unstandardized coefficient in the regression model (minutes per unit of predictor). Positive values are associated with increased on-scene time. Fully adjusted model is an intermediate calculation step to select factors for final model. Missing values: 6 for age and 2 for daylight. OST was missing in 37 (2.3%) of the 1642 identified missions in the four included subgroups

ISSN: 1757-7241