aCCI	Age-adjusted Charlson comorbidity index
AECOPD	Acute exacerbation of chronic pulmonary obstructive disease
AUC	Area under the curve
BAP-65	BAP-65 Score for Acute Exacerbation of COPD
BLS	Basic life support
BUN	Blood urea nitrogen
CI	Confidence interval
COPD	Chronic obstructive pulmonary disease
CURB-65	CURB-65 Score for Pneumonia Severity
DBP	Diastolic blood pressure
ED	Emergency department
EMT	Emergency medical technicians
ERN	Emergency registered nurse
EWS	Early Warning Scores
FiO2	Fraction of inspired Oxygen
GCS	Glasgow coma Scale
HR	Heart rate
HzR	Hazard ratio
ICU	Intensive care unit
IMV	Invasive mechanical ventilation
IQR	Interquartile ranges
M1Y	One-year mortality
M2Y	Two-year mortality
MBP	Medium blood pressure
NEWS2	National Early Waring Score 2
NIMV	Noninvasive mechanical ventilation
PAHO-WHO	Pan American Health Organization
PEMS	Prehospital Emergency Medical Services
qCSI	Quick COVID-19 Severity Index
qSOFA	Quick Sequential [Sepsis-related] Organ Failure Assessment
RD	Respiratory disease
RI	Respiratory infections
ROC	Receiver operating characteristic
RR	Respiratory rate
SACYL	Castilla y León Public Health System
SBP	Systolic blood pressure
SpO2	Peripheral oxygen saturation
STROBE	STrengthening the Reporting of OBservational studies in Epidemiology
TT	Temperature