Cardio

10/25/99

 

V/Q

• Ideally would like 2/2 (2 parts air and 2 parts blood)
• Actually have about 0.8 ratio
• Always have a V/Q imbalance
• Upper part of lung has more V than Q
• 3/2 ratio (larger ratio)
• Increased the V/Q
• Also referred to a high V/Q in the higher part of the lungs
• Lower parts of the lungs
• Has more blood
• Little V and a lot of Q
• 2/3 ratio (smaller)
• Decreased V/Q
• Also referred to a low V/Q
• Middle part of the lungs
• Close to having a balanced V/Q
• If you develop a high or low V/Q overall, you die
• The high V/Q of the upper part and the low V/Q of the lower part equal each other out
• If the entire lung becomes high or low, the person is in trouble
• The body would drain everything else to keep energy going to the lungs to keep the V/Q balanced
• Theoretical units
• Normal unit—equal amount of air and blood
• Deadspace unit—normal amount of air and decreased blood
• Anemia, embolism, heart attack
• Anything that keeps blood from the lungs
• Have decreased the Q
• From 2/2 to 2/1
• Increased the V/Q
• Increasing physiological Deadspace through increasing alveolar deadspace
• This occurs normally in the upper lungs
• Shunt Unit
• Decreased air, plenty of blood (normal Q)
• Decreased V
• Obstructive and restrictive lung diseases
• Sick lungs (lung disease)
• From 2/2 to ½
• Decreased V/Q
• Normally seen in the lower lobes
• Can shunt the blood to other areas of the lung to be used
• What is happening to deadspace? It is staying the same (there is no wasted air b/c there is no air)
• Blood is wasted here
• Shunted blood is blood that returns to the left side of the heart w/high quantities of reduced hemoglobin
• This is the same as venous add mixture
• Makes up about 2% of the blood
• Anything over 4% is considered pathological
• Silent Unit
• Decreased air and blood
• Part of a lobe removed
• Tension pneumothorax—collapsed lung—presses on air and blood supply
• Hear nothing over an area of collapsed lung w/a stethoscope

 

VA/Q imbalance

• ­ Physiological dead space—high V/Q (wasted air)
• Lung apex—upright posture—high V/Q
• Restrictive pulmonary ds—low V/Q
• Obstructive pulmonary disease—low V/Q
• Alveolar dilatation*
• Low V/Q
• Atelectasis—collapse of acinus
• Lung disease
• Pulmonary emboli—high V/Q
• Chronic pulmonary hypertension—could argue either way
• Primary==Drug abuse; vascular supply constricted—high V/Q
• ­ Raw—airway resistance
• V is depressed
• Obstructive disease will cause this

 

	Predicted valves	Pt A	Pt B
FVC Forced vital capacity	4.0L	3.5L	2.9L
FEV Forced expiratory volume in 1 sec	3.5L	3.1L	1.5L
FEV1/FVC	81%	88% ¯ Raw—restrictive	55%--­ Raw—obstructive
TLC Total lung capacity	5.0L	4.2L inhale problem, ¯ compliance	6.5L large lungs—trapped air; exhale problem ­ compliance, ¯ recoil
RV Residual volume	1.0L	0.7L	3.6L

 

Which is obstructive?  Pt B

Which is restrictive? Pt A

What is the V/Q of each? ¯ V/Q in both

Which is hypoventilated? Both

In which would hypoxemia (¯ O2) / hypercapnia (­ CO2) result? Both

In which would venous admixture (shunted blood) occur? Both

Which one is a dead space unit?  Neither

Which one is a silent unit? Neither

Which one is a shunt unit? Both

Which one will demonstrate increased physiological dead space? Neither, there is no wasted air

Which will reduce SaO2? Both

In which will O2 dissociation shift to the left (more alkaline)? Neither, both will shift to the right (more acidic)

In which would an Atelectasis be most likely? Pt A

            Pneumonia? Pt A

            COPD? Pt B

Why is vital capacity reduced in "A"? "B"?

            Vital Capacity is IRV, TV, and ERV

            In restrictive—can't inhale, ¯ VC (all volumes)

            In obstructive, ­ RV which eats the VC

In which example would hyperventilation be most likely? Neither