What is the formula for functional residual capacity (FRC)?
FRC = expiratory reserve volume + residual volume.
What does FRC represent?
It is the volume of air in the lungs after normal expiration, measured by either gas dilution or body plethysmography.
What factors can increase FRC?
Standing position, Asthma/COPD, PEEP/CPAP.
What factors can decrease FRC?
Supine position, Obesity, Pregnancy, Restrictive lung disorders, General anaesthesia.
What is SvO2, and what is a normal value?
SvO2 is obtained from a pulmonary artery catheter and measures the end result of O2 consumption and delivery, containing blood from both the SVC and IVC. The normal range is approximately 65–70%.
What causes an increase in SvO2?
↑ SvO2 can be caused by:
1. ↑ O2 delivery (e.g., ↑ FiO2, hyperbaric O2)
2. ↓ O2 extraction (e.g., hypothermia, general anaesthetic, neuromuscular blockade)
3. ↑ Flow states (e.g., sepsis, thyrotoxicosis, severe liver disease)
What causes a decrease in SvO2?
↓ SvO2 can be caused by:
1. ↓ O2 delivery (e.g., shock states, hypoxemia, anaemia)
2. ↑ O2 extraction (e.g., hyperthermia, shivering, pain, seizures)
3. Decreased Cardiac Output
