TTI	transthoracic impedance
SD	standard deviation
Hb	hemoglobin
AA	anterior-anterior
AL	anterior-lateral
AP	anterior-posterior
vf	ventricular fibrillation
vt	ventricular tachycardia
va	ventricular arrhythmia
af	atrial fibrillation
aa	atrial arrhythmia
BSA	body surface area
PEEP	positive end-expiratory pressure
BMI	body mass index
CHF	congestive heart failure
COPD	chronic obstructive pulmonary disease