Stuff for Nurses

1. Blood Gases
BLOOD GASES Normal Values
Arterial (Sea Level) pH 7.35-7.45 PaO2* 80-100 mm Hg PaCO2 32-48 mm Hg HCO3 22-26 mEq/
L O2 saturation > 95%
*In a patient > 60 years old, PaO2 is equal to 80 mm Hg minus 1 mm Hg for every year over 60.
Expected PaO2 = FIO2 × 5.
Interpreting Arterial Blood Gases (ABGs)
1 Check pH ↑ = Alkalosis; ↓ = acidosis
2 Check PaCO2 ↑ = CO2 retention (hypoventilation); respiratory acidosis or compensating for metabolic
alkalosis ↓ = CO2 blown off (hyperventilation); respiratory alkalosis or compensating for metabolic
acidosis
3 Check HCO3 ↑ = Nonvolatile acid is lost; HCO3 gained (metabolic alkalosis or compensating for
respiratory acidosis) ↓ = Nonvolatile acid is added; HCO3 is lost (metabolic acidosis or compensating for
respiratory alkalosis)
4 Determine imbalances
Definition and Sources of Variation in ECG Waveforms and Intervals* Description Normal Duration
(sec) Source of Possible Variation
Definition and Sources of Variation in ECG Waveforms and Intervals* Description Normal Duration (sec)
Source of Possible Variation
P wave Represents time for the passage of the electrical impulse through the atrium causing atrial
depolarization (contraction); should be upright 0.06-0.12 Disturbance in conduction within atria
PR interval Measured from beginning of P wave to beginning of QRS complex; represents time taken for
impulse to spread through the atria, AV node and bundle of His, the bundle branches, and Purkinje
fibers, to a point immediately preceding ventricular contraction 0.12-0.20 Disturbance in conduction
usually in AV node, bundle of His, or bundle branches but can be in atria as well
QRS interval Measured from beginning to end of QRS complex; represents time taken for depolarization
(contraction) of both ventricles (systole) < 0.12 Disturbance in conduction in bundle branches or in
ventricles
ST segment Measured from the S wave of the QRS complex to the beginning of the T wave; represents
the time between ventricular depolarization and repolarization (diastole); should be isoelectric (flat)
0.12 Disturbances usually caused by ischemia or infarction

2. T wave Represents time for ventricular repolarization; should be upright 0.16 Disturbances usually
caused by electrolyte imbalances, ischemia, or infarction
QT interval Measured from beginning of QRS complex to end of T wave; represents time taken for entire
electrical depolarization and repolarization of the ventricles 0.34-0.43 Disturbances usually affecting
repolarization more than depolarization and caused by drugs, electrolyte imbalances, and changes in
heart rate