R: V/Q Mismatch Flashcards
V/Q Mismatch
minute ventilation
Respiratory Rate (how fast you breath) X Tidal Volume (how deeply you breath)
determines determines hypoventilation or hyperventilation
V/Q Ratio
amount of air that reaches your lungs over amount of blood flow in the capillaries
2 Types of V/Q
Shunt: Perfusion of poorly ventilated alveoli
Dead Space: Ventilation of poorly perfused alveoli
Oxygenation changes what
PaO2
Ventilation changes what
PaCO2
V/Q mismatch exists when what
there is an imbalance between ventilated alveoli and good blood flow through the alveolar capillaries
V/Q mismatch: Shunt
Occurs when there is adequate blood flow/perfusion, but NOT ENOUGH VENTILATION
A shunt can be two types of what
Absolute (zero)
Relative (small amount of ventilation)
Conditions that can cause shunt
- Pneumonia and pulm edema (alveoli filled with fluid)
- Tissue trauma (alveolar wall swelling)
- Atelectasis (collapse of alveoli from failure to expand) * most common
- Mucus plugging
- Pulmonary arteriovenous fistulas
- Pulmonary Hypertension
V/Q Mismatch; Dead Space
Dead space has ventilation but POOR PERFUSION, in which oxygen cannot enter blood stream
Two types of deadspace
Anatomic: fixed by anatomy, areas in resp tract with O2 but no blood flow (trachea, bronchus, nasopharynx, bronchioles)
Physiologic: Alveoli is ventilated but not enough blood flow to carry the O2 to the organs
V/Q ratio higher than pt norm =
decreased perfusion = deadspace
V/Q ratio lower than pt norm =
decreased ventilated alveoli = shunt
can we change anatomic dead space
what is the highest dead space for baby at an ideal body weight
not really - on average a baby will have dead space. The highest dead space is 3mL/kg ideal body weight
how to estimate anatomic dead space
pt body weight x 3mL/kg
pt weighs 2kg
so pt anatomical dead space = 6mL
