Resp 2 Flashcards
Equation for Law of Laplace
P = (2T)/r
Tendency to collapse on ______ as radius decreases
Expiration
______ alveoli have low collapsing pressure and are easy to keep open. ______ alveoli have high collapsing pressure and are more difficult to keep open.
Large; small
Surfactant is composed of:
Phospholipid, proteins, & Ca
Acts as surface tension reducer by disrupting the intermolecular forces (hydrogen bonds) b/w water molecules of liquid
Act like detergent
Surfactant
Reduction in surface tension _____ compliance
Increases
What lecithin-to-sphingomyelin (L/S) ratio in amniotic fluid indicates fetal lung maturity
> 2:1
Synthesis of surfactant starts when?
24 weeks of gestation; almost always present at week 35
Symptoms of neonatal respiratory distress syndrome d/t lack of surfactant
Atelectasis
Difficulty reinstating lungs (d/t decreased compliance)
Hypoxemia (d/t decreased V/Q)
Tx for neonatal respiratory distress syndrome
Maternal steroid shots before birth (speeds up formation of surfactant)
Artificial surfactant to infants by inhalation
Airflow (Q) =
Pressure gradient/ airway resistance (R)
Resistance to flow (R) =
(8 n L)/ pie r 4
8 (viscosity of inspired gas) x length of airway/ pie radius to the 4th power
Poiseuille’s equation says air flow is:
Directly proportional to the pressure gradient, and pie radius to the 4th power
Inversely proportional to 8 x the viscosity and Length
_____ lung volumes are associated w/ less radial traction and increased airway resistance
Low
_____ lung volumes are associated with greater radial traction and decreased airway resistance
High
Major site of airway resistance
In the medium-sized bronchi
Why do the smallest airways not offer the highest resistance?
B/c of their parallel arrangement
Work of inspiration:
Compliance work (50%)
Tissue resistance work
Airway resistance work
The volume inspired or expired with each normal breath
Tidal volume
the volume that can be inspired over and above the tidal volume (used during exercise)
Inspiration Reserve Volume
The volume that can be expired after the expiration of tidal volume
Expiratory Reserve Volume
The volume that remains in the lungs after a maximum expiration
Cannot be measured by spirometry
Residual Volume
How is residual volume measured?
Helium Dilution Method
The sum of tidal volume, inspiration reserve volume, & expiratory reserve volume
“Everything but the residual volume”
Vital capacity
Inspiration capacity =
TV + IRV
The volume remaining in the lungs after a tidal volume is expired
Functional Residual Capacity
FREC =
ERV + RV
The volume in lungs after a maximum inspiration
The sum of all 4 volumes
Total lung capacity
prevents large SWINGS of PO2 by acting as a bufffer
FRC
FRC is reduced by:
Supine position
Obesity
Pregnancy
Anesthesia
FRC increases by:
PEEP, CPAP
Increased airway resistance- asthma
Allows for more time (up to 10 min) for airway manipulation
Preoxygenation/Denitrogenation before anesthetic induction provides reservoir of O2 by filling FRC with 100 % O2
The volume of air that can be forcible expired as hard and as rapid as possible after taking maximum inspiration
Forced vital capacity (FVC)
Forced Expiratory Volume in 1st second/ Forced Vital Capacity
4/5 = 80%
In obstructive lung diseases such as asthma & COPD, the FEV1/FVC is ________
Decreased
In restrictive lung diseases such as pulmonary fibrosis, pneumothorax, scoliosis, myasthenia gravis, or ALS, FEV1/FVC is _______
Normal or increased
Poor lung expansion can be seen in _____ toxicity
Bleomycin (anti cancer)
Decreased BP and decreased PCWP =
Hypovolemic shock, give fluid
Decreased BP, increased PCWP =
Failing heart/cardiogenic shock, give inotropes
PCWP measures?
Left atrial pressure. Normally 10 mmHg
Right atrium pressure
< 5 mmHg
Right ventricle pressure
<25 / <5 mmHg
Left atrium pressure
< 12 mmHg
Left ventricle pressure
< 150/ 10 mmHg
Pulmonary trunk pressure
< 25/10 mmHg
Aortic pressure
< 150/90 mmHg
PCWP
< 12 mmHg
Pulmonary artery pressures
25/8
Mean = 15
Capillary = 7
In the pulmonary circulation, compliance is ______ and resistance is _______
Higher; lower
Why does alveolar hypoxia cause vasoconstriction in the lungs?
To divert blood away from poorly ventilated regions towards well-ventilated regions of lung. Decrease shunting of blood
Why is fetal pulmonary vascular resistance very high
D/t hypoxic vasoconstriction/ decreased blood flow
What happens with global hypoxia (breathing in thin air at high altitude)?
Vasoconstriction of entire lungs > pulmonary HTN > RVF
PVR =
((Pulm artery pressure - PCWP)/ CO ) x 80
PA > Pa > Pv
Zone I
Pa > PA > Pv
Zone II
Pa > Pv > PA
Zone III
Distribution of pulmonary blood flow is uneven d/t
Effect of gravity
When supine, pulmonary blood flow is
Nearly uniform throughout the lung
When standing, blood flow is lowest at _______ and highest at _____
Apex (zone 1); base (zone 3)
Factors that expand West Zone 1:
Decreased PA pressure (shock) pulm hypotension
Increased Alveolar pressure (PEEP)
Occlusion of blood vessel (pulmonary embolism)
Factors that reduce West Zone 1:
Increased PA pressure (pulm hypertension)
V/Q ratio is highest (3) at ____ and lowest (0.8) at ____
Apex; base
If the airways are completely blocked (ventilation 0), but blood flow is normal, the V/Q is? Which is called?
0; right-to-left shunt
If the blood flow is blocked, but the ventilation is normal, the V/Q is? Which is called?
Infinite; dead space
100% O2 will improve which type of V/Q mismatch?
Blood flow obstruction
