Table 1.

Characteristics of study patients, comparing successful helmet CPAP treatment vs. failure

	All patients N = 306	Successful helmet CPAP treatment N = 159	Helmet CPAP failure N = 147	P value
Age, years	67 [58–76]	62 [54–70]	71 [63–79]	< 0.001*
Sex male, n. (%)	236 (77)	121 (76)	115 (78)	0.685
Body mass index, kg/m2	26 [24–30]	26 [24–30]	25 [24–30]	0.631
Any comorbidity, n. (%)	228 (74)	99 (62)	129 (88)	< 0.001*
Hypertension, n. (%)	159 (52)	69 (43)	90 (61)	0.002*
Comorbidities, n	1 [0–2]	1 [0–2]	2 [1–3]	< 0.001*
Clinical Frailty Scale	3 [2–4]	2 [2, 3]	3 [2–5]	< 0.001*
Symptoms onset to hospital admission, days	7 [4–10]	7 [5–10]	7 [4–10]	0.464
Hospital admission to oxygen therapy failure, days	1 [0–2]	1 [0–3]	0 [0–2]	0.001*
Do not intubate (DNI) order, n (%)	130 (42)	37 (23)	93 (63)	< 0.001*
White blood cells, n*103/µL	7.38 [5.58–10.11]	7.03 [5.65–8.4]	7.71 [5.35–11.28]	0.052
Platelets, n*103/µL	202 [153–260]	213 [164–265]	183 [142–256]	0.027
C-reactive protein, mg/L	109 [50–172]	86 [39–131]	144 [67–207]	< 0.001*
Procalcitonin, ng/mL	0.29 [0.13–1.05]	0.2 [0.11–0.63]	0.44 [0.2–1.42]	0.001*
Lactate dehydrogenase, U/L	420 [332–524]	369 [313–477]	475 [375–589]	< 0.001*
Creatinine, mg/dL	1 [0.8–1.3]	1 [0.8–1.1]	1.1 [0.9–1.5]	< 0.001*
Urea, mg/dL	39 [28–61]	32 [25–44]	50 [33–84]	< 0.001*

Univariate analysis of the association of relevant characteristics with CPAP failure. Data regarding the study population (All patients), the subgroup of patients successfully treated by helmet CPAP (Successful helmet CPAP treatment) and the subgroup of patients failing the helmet CPAP treatment (either intubated or non-survivors, depending on their ceiling-of-care status) are reported in the table

*Indicates persistence of statistically significant differences after Bonferroni correction for multiple comparisons (p < 0.003).