
==== Front
West J Emerg Med
West J Emerg Med
WestJEM
Western Journal of Emergency Medicine
1936-900X
1936-9018
Department of Emergency Medicine, University of California, Irvine School of Medicine

10.5811/westjem.17975
wjem-25-325
Critical Care
Brief Research Report
Emergency Department SpO2/FiO2 Ratios Correlate with Mechanical Ventilation and Intensive Care Unit Requirements in COVID-19 Patients
SpO2/FiO2 Ratios Correlate with Mechanical Ventilation and ICU Requirements
Zhang et al.
Zhang Gary MD *
Burla Michael J. DO *†§
Caesar Benjamin B. MD *
Falank Carolyne R. PhD *
Kyros Peter MD *
Zucco Victoria C. BS *
Strumilowska Aneta BS ‡
Cullinane Daniel C. MD *
Sheppard Forest R. MD *
* Maine Medical Center, Department of Surgery, Portland, Maine
† Southern Maine Healthcare, Department of Emergency Medicine, Biddeford, Maine
‡ University of New England College of Osteopathic Medicine, Biddeford, Maine
§ Tufts School of Medicine, Boston, Massachusetts
Address for Correspondence: Michael J. Burla, DO, Southern Maine Health Care, Department of Emergency Medicine, Southern Maine Health Care, 1 Medical Center Dr, Biddeford, ME 04005. Email: Michael.burla@Mainehealth.org
01 5 2024
18 4 2024
25 3 325331
31 3 2023
08 1 2024
10 1 2024
© 2024 Zhang et al.
2024
https://creativecommons.org/licenses/by/4.0/ This is an open access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) License. See: http://creativecommons.org/licenses/by/4.0/

Background

Patients with coronavirus 2019 (COVID-19) are at high risk for respiratory dysfunction. The pulse oximetry/fraction of inspired oxygen (SpO2/FiO2) ratio is a non-invasive assessment of respiratory dysfunction substituted for the PaO2:FiO2 ratio in Sequential Organ Failure Assessment scoring. We hypothesized that emergency department (ED) SpO2/FiO2 ratios correlate with requirement for mechanical ventilation in COVID-19 patients. Our objective was to identify COVID-19 patients at greatest risk of requiring mechanical ventilation, using SpO2/FiO2 ratios.

Methods

We performed a retrospective review of patients admitted with COVID-19 at two hospitals. Highest and lowest SpO2/FiO2 ratios (percent saturation/fraction of inspired O2) were calculated on admission. We performed chi-square, univariate, and multiple regression analysis to evaluate the relationship of admission SpO2/FiO2 ratios with requirement for mechanical ventilation and intensive care unit (ICU) care.

Results

A total of 539 patients (46% female; 84% White), with a mean age 67.6 ± 18.6 years, met inclusion criteria. Patients who required mechanical ventilation during their hospital stay were statistically younger in age (P = 0.001), had a higher body mass index (P < .001), and there was a higher percentage of patients who were obese (P = 0.03) and morbidly obese (P < .001). Shortness of breath, cough, and fever were the most common presenting symptoms with a median temperature of 99°F. Average white blood count was higher in patients who required ventilation (P = <0.001). A highest obtained ED SpO2/FiO2 ratio of ≤300 was associated with a requirement for mechanical ventilation. A lowest obtained ED SpO2/FiO2 ratio of ≤300 was associated with a requirement for intensive care unit care. There was no statistically significant correlation between ED SpO2/FiO2 ratios >300 and mechanical ventilation or intensive care unit (ICU) requirement.

Conclusion

The ED SpO2/FiO2 ratios correlated with mechanical ventilation and ICU requirements during hospitalization for COVID-19. These results support ED SpO2/FiO2 as a possible triage tool and predictor of hospital resource requirements for patients admitted with COVID-19. Further investigation is warranted.
==== Body
pmcINTRODUCTION

The coronavirus 2019 (COVID-19) pandemic profoundly impacted hospital systems worldwide. Identifying patients presenting with COVID-19 in the emergency department (ED) at greatest risk for requiring mechanical ventilation or intensive care unit (ICU) care is of paramount importance since this would facilitate more efficient allocation of limited medical resources. Severe COVID-19 infection can be life-threatening and is associated with significant hypoxemia and the development of acute respiratory distress syndrome (ARDS).1,2 Identifying early predictors of respiratory failure and ICU need is vital both for patient care and logistics in the setting of a global pandemic with limited ICU resources.

The pulse oximetry/fraction of inspired oxygen (SpO2/FiO2 ratio) has previously been used as a predictor of high-flow nasal cannula failure, need for intubation, and mechanical ventilation.3 The SpO2 value has been demonstrated to be a reliable surrogate for partial pressure of oxygen in the arterial blood (PaO2),4,5 and the SpO2/FiO2 ratio does not require any blood tests. The SpO2/FiO2 ratio is a non-invasive assessment of respiratory dysfunction that can be quickly obtained at the bedside. Measured at the time of presentation, the SpO2/FiO2 ratio has been demonstrated to be an independent indication of ARDS development.6 The ability to quickly determine required level of care for vulnerable patients is essential to prevent poor outcomes, particularly in resource-limited environments. The COVID-19 pandemic led to ED crowding and a decrease in ventilator and ICU availability.7 A validated prognostic indicator tool akin to the systematic inflammatory response syndrome or Sequential Organ Failure Assessment criteria for sepsis8 is vital for ED use to identify COVID-19 patients at highest risk of ventilator and ICU need. The SpO2/FIO2 ratio predictive value has previously been validated in ARDS,6 and early measurement may serve as an indicator and triage tool in COVID-19 with regard to respiratory failure/ventilation risk and ICU need.

Our objective in this study was to evaluate ED SpO2/FIO2 ratios in COVID-19 patients and correlate them with subsequent respiratory failure, necessitating the need for ICU level of care and/or mechanical ventilation during hospitalization. Use of this ratio may help hospital systems more efficiently use resources and effectively prepare for a patient’s need for ICU care or mechanical ventilation.

MATERIALS AND METHODS

Study Design and Participant Selection

This was a retrospective study that evaluated admission encounters from both Maine Medical Center (MMC) and Southern Maine Health Care (SMHC). These institutions work closely together, with MMC being the region’s tertiary care center with over 70,000 annual ED visits and a total of 45 multipurpose ICU beds. The SMHC is a community hospital within close proximity to MMC, averaging ≈55,000 total ED visits and nine ICU beds. COVID-19 patients who were ≥18 years old and required admission to either hospital met inclusion criteria. Encounters were collected between March–December 28, 2020; thus, no patients had been vaccinated against COVID-19. Patients were excluded if they did not require admission. This study was performed under approval of the institutions’ review boards.

Data Variables

We performed retrospective chart review to identify patient demographics, diagnoses, level of hospital care, and hospital outcomes data from electronic health records. The FiO2 values were calculated using nasal cannula flow rate.9 We recorded the patient’s lowest and highest SpO2 and FiO2 values in the ED and calculated SpO2/FiO2 ratios.

Outcomes

The primary outcome was the need for mechanical ventilation. Secondary outcomes included ICU level of care, ventilator days, in-hospital complications, escalation of care following initial triage, ICU length of stay (LOS), hospital LOS, and in-hospital mortality.

Analysis

We analyzed data using RStudio 2020 (RStudio Inc, Boston, MA). Descriptive statistics were presented as frequency and percentage. Normally distributed continuous data were reported as mean with SDs, and ordinal non-normally distributed continuous data were described with medians with interquartile ranges. We used multivariable logistic regression to assess the association between either low or high SpO2/FiO2 ratios within the ED, anticoagulation use, asthma, coronary artery disease (CAD), congestive health failure (CHF), chronic obstructive pulmonary disease (COPD), diabetes, hyperlipidemia, hypertension, and gastroesophageal reflux disease (GERD), or the need for mechanical ventilation, adjusted for age and body mass index (BMI). Bivariable analysis of categorical variables was done using the χ2 test, and nonparametric variables by the Kruskal-Wallis test. Regression models controlled for both age and BMI.

RESULTS

A total of 539 patients, with a mean age 67.6 ± 18.6 years, met inclusion criteria. Patients were stratified into two cohorts based on the need for mechanical ventilation (Table 1). As shown in the table, patients who required mechanical ventilation during their hospital stay were statistically younger in age (P = 0.001), had a higher BMI (P < .001), and there was a higher percentage of patients who were obese (P = 0.03) and morbidly obese (P < .001). Shortness of breath, cough, and fever were the most common presenting symptoms, with a median temperature of 99°F. The average white blood count was higher in patients who required ventilation (P = <0.001) (Table 1). Patients requiring mechanical ventilation had higher diagnoses of ARDS (P < .001), pneumonia (P < .001), shock (P < .001), respiratory and renal failure (P < .001), and worse hospital outcomes with an in-hospital mortality of 32% vs 8% (P < .001) and a median hospital LOS of 17.5 vs 6 days (P < .001).

Table 1. Baseline characteristics of patients with coronavirus 2019.

Demographic data	Mean ± SD, median, range or n (%)		
Not mechanically
ventilated n = 451	Mechanically
ventilated n = 88	
P-value	
Age (median, IQR)	72, 26	66, 19.75	0.001	
BMI (median, IQR)	28.9, 9.4	32.3, 10.9	<.001	
Gender				
 Female	217 (48%)	31 (35%)	0.03	
 Male	234 (52%)	57 (65%)	0.03	
Race				
 Asian	11 (2%)	5 (6%)	0.03	
 Black	31 (7%)	5 (6%)	0.73	
 Native Hawaiian or other Pacific Islander	1 (0.2%)	0 (0%)	0	
 Unknown/not reported	2 (0.4%)	2 (2%)	0.003	
 More than one race	3 (0.6%)	0 (0%)	0.47	
 White	397 (88%)	73 (83%)	0.20	
 Other	6 (1%)	3 (3%)	0.13	
Ethnicity				
 Hispanic or Latino	9 (2%)	3 (3%)	0.56	
 Not Hispanic or Latino	440 (98%)	84 (95%)	0.10	
 Unknown/not reported	2 (0.4%)	1 (1%)	0.46	
Origin				
 Home	282 (63%)	54 (61%)	0.72	
 Nursing home	61 (14%)	9 (10%)	0.31	
 Skilled nursing home	31 (7%)	0 (0%)	0.01	
 Rehab	1 (0.2%)	2 (2%)	0.03	
 Other*	76 (17%)	23 (26%)	0.05	
Comorbid conditions				
 Alcohol use	23 (5%)	8 (9%)	0.14	
 Anticoagulation therapy	52 (12%)	13 (15%)	0.44	
 Asthma	66 (15%)	14 (16%)	0.81	
 Cerebrovascular accident	41 (9%)	4 (5%)	0.22	
 COPD	71 (16%)	16 (18%)	0.64	
 Chronic heart failure	67 (15%)	13 (15%)	1	
 Chronic kidney disease	73 (16%)	12 (14%)	0.64	
 Cancer	57 (13%)	9 (10%)	0.44	
 Coronary heart disease/heart failure	105 (23%)	19 (22%)	0.84	
 Current smoker	30 (7%)	2 (2%)	0.08	
 Dementia	75 (17%)	5 (6%)	0.01	
 Diabetes mellitus	156 (35%)	38 (43%)	0.15	
 GERD	132 (29%)	26 (30%)	0.85	
 Myocardial infraction	39 (9%)	5 (6%)	0.36	
 Hypertension	282 (63%)	57 (65%)	0.72	
 Hyperlipidemia	222 (49%)	49 (56%)	0.23	
 Morbidly obese	14 (3%)	11 (13%)	<.001	
 Obese	81 (18%)	25 (28%)	0.03	
Presenting symptoms				
 Fever	176 (39%)	34 (39%)	1	
 Myalgia	72 (16%)	15 (17%)	0.82	
 Arthralgias	21 (5%)	2 (2%)	0.22	
 Headache	50 (11%)	4 (5%)	0.09	
 GI symptoms	140 (31%)	17 (19%)	0.02	
 Cough	229 (51%)	54 (61%)	0.09	
 Shortness of breath	253 (56%)	57 (65%)	0.12	
 Other	233 (52%)	43 (49%)	0.61	
Average temperature in the ED ± SD (Fahrenheit)	97.1 ± 12.4, 99.1, 7.3–104.5	98.1 ± 10, 99, 37–103	0.48	
WBC count in the ED (median, IQR)	6.2, 4.7	8, 7.4	<.001	
Diagnoses				
 ARDS	24 (5%)	57 (65%)	<.001	
 Pneumonia	183 (41%)	60 (68%)	<.001	
 Neurological diagnoses	128 (28%)	40 (45%)	0.002	
 Renal diagnoses	129 (29%)	55 (63%)	<.001	
 Liver diagnoses	44 (10%)	23 (26%)	<.001	
 Heart diagnoses	168 (37%)	56 (64%)	<.001	
 Pulmonary diagnoses	280 (62%)	69 (78%)	0.004	
 Shock	10 (2%)	46 (52%)	<.001	
 Respiratory failure	153 (34%)	75 (85%)	<.001	
 Renal failure	29 (6%)	22 (25%)	<.001	
ICU				
 Patients who required ICU care at any point	75 (17%)	84 (95%)	<.001	
 Required more than one ICU admissions	2 (0.4%)	6 (7%)	<.001	
 ICU LOS (median, IQR)	2, 3	13, 16	<.001	
Intubated				
 Patients who were intubated	0 (0%)	84 (95%)	<.001	
 Days intubated	n/a	2, 4		
 Non-procedure based intubation	0 (0%)	51 (58%)	<.001	
Mechanical ventilators				
 Ventilator days (median, IQR)	n/a	9, 13		
 Required reintubation	n/a	7 (8%)		
 Escalation of care from initial triage	60 (13%)	56 (64%)	<.001	
 Hospital LOS (median, IQR)	6, 6	17.5, 19	<.001	
Discharge disposition				
 Home or self-care	193 (43%)	8 (9%)	<.001	
 Home with services	97 (22%)	17 (19%)	0.53	
 Hospice/palliative care unit	11 (2%)	1 (1%)	0.52	
 Mental health/psychiatric hospital	8 (2%)	0 (0%)	0.18	
 Nursing home	17 (4%)	1 (1%)	0.16	
 Other	62 (14%)	34 (39%)	<.001	
 Rehab	15 (3%)	24 (27%)	<.001	
 Skilled nursing facility	48 (11%)	3 (3%)	0.02	
 In-hospital mortality	36 (8%)	28 (32%)	<.001	
* Other includes homeless, transfers in, group home, Primary care physician follow up, mental health facility.

BMI, body mass index; IQR, interquartile range; COPD, chronic obstructive pulmonary disease; GERD, gastroesophageal reflux disease; WBC, white blood count; ED, emergency department; ARDS, acute respiratory disease syndrome; GI, gastrointestinal; ICU, intensive care unit; LOS, length of stay.

The SpO2/FiO2 ratios in the ED and their associations with mechanical ventilation or need for ICU care are presented in Table 2. A highest obtained ED SpO2/FiO2 ratio of 300 or below was statistically associated with a requirement for mechanical ventilation during hospitalization. A lowest obtained ED SpO2/FiO2 ratio of 300 or below was statistically associated with a requirement for ICU care during hospitalization. There was no statistically significant relationship between ED SpO2/FiO2 ratios above >300 and mechanical ventilation or ICU level of care.

Table 2. SpO2/FiO2 ratios and their association with intensive care unit or mechanical ventilation needs.

Variable SpO2/FiO2 ratios*	No mechanical
ventilation N (%)	Required mechanical
ventilation N (%)	
95% CI	
OR	
P-value	
Lowest ED SpO2/FiO2						
 0–100	18 (4)	13 (18)	2.4–10.9	5.1	<.001	
 101–200	5 (1)	3 (4)	0.75–12.6	3.1	0.05	
 201–300	37 (9)	14 (20)	1.2–4.7	2.4	0.005	
 301–400	113 (27)	19 (27)	0.6–1.8	1.0	0.86	
 401–500	251 (59)	22 (31)	0.2–0.5	0.31	<.001	
Highest ED SpO2/FiO2						
 0–100	7 (2)	7 (10)	2.2–19.2	6.5	<.001	
 101–200	4 (1)	3 (4)	1.0–21.2	4.6	0.05	
 201–300	14 (3)	11 (15)	1.7–8.1	3.7	0.002	
 301–400	106 (25)	20 (28)	0.72–2.2	1.3	0.47	
 401–500	293 (69)	30 (42)	0.2–0.6	0.3	<.001	

Variable SpO2/FiO2 ratios*	
No ICU admission N (%)	ICU admission
N (%)	
95% CI	
OR	
P-value	
Lowest ED SpO2/FiO2						
 0–100	8 (2)	23 (17)	3.8–20	8.8	<.001	
 101–200	1 (0.3)	7 (5)	2.3–158	19.2	<.001	
 201–300	27 (8)	24 (18)	1.4–4.5	2.5	0.001	
 301–400	94 (26)	36 (26)	0.6–1.5	0.93	0.66	
 401–500	228 (64)	47 (34)	0.2–0.5	0.32	<.001	
Highest ED SpO2/FiO2						
 0–100	3 (1)	11 (8)	2.8–10	10.3	<.001	
 101–200	0 (0)	7 (5)	2.3–19	19.2	<.001	
 201–300	11 (3)	14 (10)	1.3–2.8	2.80	0.01	
 301–400	88 (25)	38 (28)	0.78–1.2	1.21	0.66	
 401–500	256 (72)	67 (49)	0.26–0.39	0.39	<.001	
* For patients who had ED SpO2/FiO2 values.

CI, confidence interval; OR, odds ratio; ED, emergency department; ICU, intensive care unit.

Chronic obstructive pulmonary disease was a confounding factor for COVID-19 patients who required mechanical ventilation (adjusted R2 value = 0.1132; P < .001). No statistically significant associations were identified between the following co-morbidities: anticoagulation use; asthma (adjusted R2 = 0.096, P = 0.75); CAD (adjusted R2 = 0.102; P = 0.07); CHF (adjusted R2 = 0.096; P = 0.95); diabetes (adjusted R2 = 0.10; P = 0.07); hyperlipidemia (adjusted R2 = 0.11; P = 0.08); hypertension (adjusted R2 = 0.096; P = 0.58); and GERD (adjusted R2 = 010; P = 0.28) for the requirement of mechanical ventilation.

DISCUSSION

This study demonstrated that the highest obtained ED SpO2/FiO2 ratio of 300 or below correlated with the need for mechanical ventilation during hospitalization. Additionally, a lowest obtained ED SpO2/FiO2 ratio of 300 or below was associated with a requirement for ICU-level care. Although COPD was a confounding factor for patients requiring mechanical ventilation, other co-morbidities were not independently associated with higher rates of mechanical ventilation and the ED SpO2/FiO2. This suggests that the SpO2/FiO2 ratio can be used as a prognostic indicator to stratify severity of illness in patients with COVID-19 during their initial evaluation in the ED. Since the SpO2/FiO2 ratio is non-invasive and can be quickly obtained and trended during a patient’s evaluation, this ratio could be an important factor in patient triage and disposition.

Multiple prognostic indicators have been proposed in the previous literature to help stratify ARDS severity and predict outcomes.10–13 The PaO2:FiO2 (P:F) ratio is a widely used measure of ARDS severity; however, multiple studies have shown that the P:F ratio is not an independent predictor of mortality.10–13 Another prognostic tool, the oxygenation index, (OI [FIO2/PaO2 × mean airway pressure × 100]) has been demonstrated to be an independent risk factor for mortality in adults with ARDS,11,12 but it requires mechanical ventilation and arterial blood gas analysis for calculation. Oxygen saturation index (OSI [FIO2 × mean airway pressure × 100)/SaO2]) is a measure that correlates to OI and is an independent predictor of clinical outcomes.12 Although OSI calculation does not require blood analysis, it still requires mechanical ventilation. Another prognostic tool, the Lung Injury Prediction Score (LIPS), has applicability in the ED.13 However, the LIPS tool requires a detailed past medical history (e.g, alcohol use disorder) and the patient’s pH, requiring a blood gas. Although all these tools provide some prognostic value, each has limitations, resulting in barriers to deployment for triaging patients in the ED.

In contrast, the SpO2/FiO2 ratio requires no blood tests and is quickly and easily obtained at the bedside. Measured at the time of presentation, it has been shown to be an independent indication of ARDS development.6 This study suggests that the SpO2/FIO2 ratio may offer an estimate of disease severity in patients with COVID-19 before progression to overt respiratory failure, serving as a triage tool to identify those at greatest risk for needing mechanical ventilation and critical care. The SpO2/FiO2 ratio can be used as a tool or part of a protocol to assess whether a patient meets transfer criteria within a hospital system. Many regional health systems operate under a “hub and spoke” model where a large central institution supports a network of smaller hospitals. Rapid identification of patients at risk for decompensation and with need for higher level care would facilitate access to limited critical care resources while also decreasing the incidence of over-triage to the hub hospital.

LIMITATIONS

The study is retrospective with inherent limitations in controlling confounding variables. The cohort was limited to one hospital system, and thus cannot account for practice variations in other healthcare systems. The hospitals evaluated in this study may have had different criteria for ICU admission. Additionally, FiO2 values were based largely on nasal cannula flow rates; limiting to high flow nasal cannula would permit more accurate FiO2 but would also limit applicability. At the time of data collection, no patients were vaccinated, thus limiting the applicability of findings to populations with some form of COVID-19 vaccination.

CONCLUSION

In summary, ED SpO2/FiO2 ratios correlate with mechanical ventilation and ICU requirements during hospitalization for COVID-19 infection. These results support ED SpO2/FiO2 as a triage tool and predictor of hospital resource requirements for patients admitted with COVID-19. Further study is required with a prospective analysis assessing accuracy of the SpO2/FiO2 ratio in predicting mechanical ventilation and need for ICU-level care.

Section Editor: Christopher Tainter, MD

Full text available through open access at http://escholarship.org/uc/uciem_westjem

Conflicts of Interest: By the WestJEM article submission agreement, all authors are required to disclose all affiliations, funding sources and financial or management relationships that could be perceived as potential sources of bias. This work was supported in part by the Northern New England Clinical and Translational Research grant U54GM115516. There are no conflicts of interest or other sources of funding to declare.
==== Refs
REFERENCES

1. Arentz M Yim E Klaff L et al . Characteristics and outcomes of 21 critically ill patients with COVID-19 in Washington State. JAMA. 2020;323 (16 ):1612–4.32191259
2. Bellani G Laffey JG Pham T et al . Epidemiology, patterns of care, and mortality for patients with acute respiratory distress syndrome in intensive care units in 50 countries. JAMA. 2016;315 (8 ):788–800.26903337
3. Roca O Caralt B Messika J et al . An index combining respiratory rate and oxygenation to predict outcome of nasal high-flow therapy. Am J Respir Crit Care Med. 2019;199 (11 ):1368–76.30576221
4. Bilan N Dastranji A Ghalehgolab Behbahani A . Comparison of the SpO2/FiO2 ratio and the PaO2/FiO2 ratio in patients with acute lung injury or acute respiratory distress syndrome. J Cardiovasc Thorac Res. 2015;7 (1 ):28–31.25859313
5. Rice TW Wheeler AP Bernard GR et al . Comparison of the SpO2/FIO2 ratio and the PaO2/FIO2 ratio in patients with acute lung injury or ARDS. Chest. 2007;132 (2 ):410–7.17573487
6. Festic E Bansal V Kor DJ et al . SpO2/FiO2 ratio on hospital admission is an indicator of early acute respiratory distress syndrome development among patients at risk. J Intensive Care Med. 2015;30 (4 ):209–16.24362445
7. Sandhu P Shah AB Ahmad FB et al . Emergency department and intensive care unit overcrowding and ventilator shortages in us hospitals during the COVID-19 pandemic, 2020–2021. Public Health Rep. 2022;137 (4 ):796–802.35642664
8. Zhao C Xin MY Li J et al . Comparing the precision of the pSOFA and SIRS scores in predicting sepsis-related deaths among hospitalized children: a multi-center retrospective cohort study. World J Emerg Med. 2022;13 (4 ):259–65.35837567
9. Markovitz GH Colthurst J Storer TW et al . Effective inspired oxygen concentration measured via transtracheal and oral gas analysis. Respir Care. 2010;55 (4 ):453–9.20406513
10. Ware LB . Prognostic Determinants of acute respiratory distress syndrome in adults: impact on clinical trial design. Crit Care Med. 2005;33 (3 Suppl ):S217–22.15753731
11. Gajic O Afessa B Thompson BT et al . Prediction of death and prolonged mechanical ventilation in acute lung injury. Crit Care. 2007;11 (3 ):R53.17493273
12. DesPrez K McNeil B Wang C et al . Oxygenation saturation index predicts clinical outcomes in ARDS. Chest. 2017;152 (6 ):1151–8.28823812
13. Elie-Turenne MC Hou PC Mitani A et al . Lung injury prediction score for the emergency department: first step towards prevention in patients at risk. Int J Emerg Med. 2012;5 (1 ):33.22943391
