Length of stay, duration of mechanical ventilation, mortality, and acute kidney injury in acute respiratory failure requiring endotracheal intubation

Table 1 Characteristics of patients in the study population, n (%)

Characteristic	Study group
Female gender	39 (29.7)
Age, years	67.3 ± 1.2
APACHE score	21.4 ± 0.7
COVID-19	65 (49.6)
Comorbidities	115 (87.7)
Diabetes mellitus	43 (32.8)
COPD	23 (17.6)
Immunosuppression	29 (22.1)
Coronary disease	28 (21.4)
Heart failure	13 (9.9)
Chronic renal failure	7 (5.3)
Acute kidney injury	71 (54.2)
Duration of mechanical ventilation, days	16.2 ± 1.4
Length of stay, days	20.1 ± 1.6
Survival rate	41 (31.3)

APACHE: Acute physiology and chronic health evaluation; COVID-19: Coronavirus disease 2019; COPD: Chronic obstructive pulmonary disease.

Table 2 Comparison of epidemiological and respiratory/arterial blood gases data amongst survivors, n = 41, and non-survivors, n = 90, n (%)

Characteristic	Survivors	Non-survivors	P value
Age, years	61.8 ± 2.7	70 ± 1.2	0.009
Sex
Female	11 (28.2)	28 (71.8)	0.619
Male	30 (32.6)	62 (67.4)
Comorbidities
No	10 (62.5)	6 (37.5)	0.004
Yes	31 (27)	84 (73)
APACHE score	18 ± 1.1	23 ± 0.9	0.001
CVC days	20.3 ± 4.1	16.1 ± 1.3	0.563
Medical admission
No	16 (53.3)	15 (46.7)	0.004
Yes	25 (25.3)	75 (74.7)
COVID-19
No	32 (49.2)	33 (50.8)	< 0.001
Yes	9 (13.6)	57 (86.4)
PaO2/FiO2	177.5 ± 10	128.4 ± 5.2	< 0.001
PaO2, mmHg	99.5 ± 5.2	87.8 ± 2.3	0.001
PaCO2, mmHg	38.4 ± 1.6	45.1 ± 1.2	0.05
pH	7.36 ± 0.01	7.3 ± 0.01	0.002
Lactate, mmol/L	3 ± 0.4	3.4 ± 0.4	0.413
Ppeak, cmH2O	31.4 ± 1.2	38.7 ± 1.1	< 0.001
PEEP, cmH2O	10 ± 0.5	12.6 ± 0.4	< 0.001
RR, breaths/minute	23.7 ± 0.7	26.5 ± 0.7	0.001
MV, L	10.3 ± 0.3	11 ± 0.3	0.05

APACHE: Acute physiology and chronic health evaluation; CVC: Central venous catheter; COVID-19: Coronavirus disease 2019; PaO₂: Arterial oxygen partial pressure; FiO₂: Fraction of inspired oxygen; PaCO₂: Arterial carbon dioxide partial pressure; Ppeak: Peak airway pressure; PEEP: Positive end-expiratory pressure; RR: Respiratory rate; MV: Minute ventilation.

Table 3 Correlation of categorical variables with length of stay and duration of mechanical ventilation amongst survivors, n = 41

Characteristic	Length of stay for survivors	P value	Duration of mechanical ventilation for survivors	P value
Sex
Female	20.1 ± 5.4	0.7	11.7 ± 3.7	0.8
Male	23.8 ± 5.2		17.5 ± 4.2
Comorbidities
No	32.4 ± 12	0.7	23 ± 9	0.4
Yes	19.7 ± 3.7		14 ± 3
Medical admission
No	18.7 ± 7.7	0.025	13 ± 5.5	0.1
Yes	25.5 ± 4.5		18 ± 4
COVID-19
No	18.7 ± 4.5	0.009	12.6 ± 3.2	0.009
Yes	37.3 ± 8		28 ± 8.4

COVID-19: Coronavirus disease 2019.

Table 4 Correlation of continuous variables with length of stay and duration of mechanical ventilation amongst survivors, n = 41

Characteristic	Length of stay for survivors (r)	P value	Duration of mechanical ventilation for survivors (r)	P value
Age	-0.4	0.02	-0.4	0.01
APACHE score	0.07	0.7	0.03	0.8
CVC days	0.99	< 0.001	0.96	< 0.001
PaO2/FiO2	0.3	0.3	-0.3	0.1
PaO2	-0.1	0.5	-0.2	0.3
PaCO2	0.17	0.3	0.1	0.4
pH	-0.02	0.9	0.1	0.5
Lactate	-0.15	0.4	-0.01	0.5
Ppeak	0.3	0.05	0.32	0.04
PEEP	0.2	0.2	0.2	0.2
RR	0.4	0.02	0.36	0.02
MV	0.3	0.1	0.3	0.1

APACHE: Acute physiology and chronic health evaluation; CVC: Central venous catheter; PaO₂: Arterial oxygen partial pressure; FiO₂: Fraction of inspired oxygen; PaCO₂: Arterial carbon dioxide partial pressure; Ppeak: Peak airway pressure; PEEP: Positive end-expiratory pressure; RR: Respiratory rate; MV: Minute ventilation.

Table 5 Correlation of epidemiological and respiratory/arterial blood gases data with occurrence of acute kidney injury, n (%)

Characteristic	No AKI, n = 60	AKI, n = 71	P value
Age, years	65.4 ± 2	69 ± 1.5	0.18
Sex
Female	14 (35.9)	25 (64.1)	0.14
Male	46 (50)	46 (50)
Comorbidities
No	10 (62.5)	6 (37.5)	0.15
Yes	50 (43.6)	65 (56.5)
APACHE score	19.5 ± 1	23 ± 1	0.007
CVC days	14.7 ±1.9	19.8 ± 2.3	0.03
Medical admission
No	19 (63.3)	12 (36.7)	0.04
Yes	41 (41.4)	59 (58.6)
COVID-19
No	40 (61.5)	25 (38.5)	< 0.001
Yes	20 (30.3)	46 (69.7)
PaO2/FiO2	150.5 ± 8.6	138.1 ± 5.8	0.4
PaO2, mmHg	88.8 ± 3.6	93.7 ± 3	0.3
PaCO2, mmHg	42.7 ± 1.5	43.4 ± 1.5	0.8
pH	7.33 ± 0.01	7.31 ± 0.01	0.2
Lactate, mmol/L	3.3 ± 0.4	3.2 ± 0.4	0.5
Ppeak, cmH2O	34 ± 1.5	38.4 ± 1	< 0.001
PEEP, cmH2O	10.7 ± 0.5	12.7 ± 0.4	0.001
RR, breaths/minute	24.6 ± 0.8	26.6 ± 0.7	0.02
MV, L	10.4 ± 0.3	11 ± 0.3	0.2

AKI: Acute kidney injury; APACHE: Acute physiology and chronic health evaluation; CVC: Central venous catheter; COVID-19: Coronavirus disease 2019; PaO₂: Arterial oxygen partial pressure; FiO₂: Fraction of inspired oxygen; PaCO₂: Arterial carbon dioxide partial pressure; Ppeak: Peak airway pressure; PEEP: Positive end-expiratory pressure; RR: Respiratory rate; MV: Minute ventilation.

Table 6 Variables that were independent predictors of mortality after binary logistic regression analysis

Variable	Regression coefficient	SE	P value	Odds ratio	95%CI
Age	0.039	0.023	0.089	1.039	0.994-1.087
Comorbidities	-3.271	1.092	0.003	0.038	0.004-0.323
APACHE score	0.222	0.057	< 0.001	1.248	1.116-1.395
Medical admission	1.634	0.889	0.066	5.125	0.897-29.272
COVID-19	-1.965	0.936	0.036	0.140	0.022-0.879
PaO2/FiO2	0.007	0.007	0.370	1.007	0.992-1.021
PaO2	-0.024	0.013	0.071	0.977	0.952-1.002
PaCO2	0.087	0.040	0.030	1.091	1.009-1.181
pH	-0.915	4.229	0.829	0.401	0.000-1592.550
Ppeak	0.150	0.060	0.013	1.162	1.033-1.308
PEEP	0.260	0.134	0.053	1.296	0.997-1.686
RR	0.395	0.172	0.022	1.484	1.033-1.308
MV	-0.001	0.000	0.017	0.999	0.999-1.000

SE: Standard error; CI: Confidence interval; APACHE: Acute physiology and chronic health evaluation; COVID-19: Coronavirus disease 2019; PaO₂: Arterial oxygen partial pressure; FiO₂: Fraction of inspired oxygen; PaCO₂: Arterial carbon dioxide partial pressure; Ppeak: Peak airway pressure; PEEP: Positive end-expiratory pressure; RR: Respiratory rate, MV: Minute ventilation.

Table 7 Variables that were independent predictors of acute kidney injury after binary logistic regression analysis

Variable	Regression coefficient	SE	P value	Odds ratio	95%CI
APACHE score	0.096	0.030	0.001	1.101	1.039-1.166
CVC days	0.017	0.013	0.198	1.017	0.991-1.044
Medical admission	0.489	0.598	0.414	1.630	0.505-5.260
COVID-19	-1.743	0.657	0.008	0.175	0.048-0.635
Ppeak	0.008	0.028	0.786	1.008	0.953-1.065
PEEP	0.075	0.076	0.326	1.077	0.929-1.250
RR	-0.014	0.039	0.713	0.986	0.913-1.064

SE: Standard error; CI: Confidence interval; APACHE: Acute physiology and chronic health evaluation; CVC: Central venous catheter; COVID-19: Coronavirus disease 2019; Ppeak: Peak airway pressure; PEEP: Positive end-expiratory pressure; RR: Respiratory rate.