Lectures 9 & 10: Pulmonary (Exam II) Flashcards
What is atmospheric pressure?
760mmHg or 1atm
What is PIP?
- Pleural Pressure = -5cmH₂O
What is PA?
What does it normally measure?
Alveolar pressure = -1(inspiration) to +1(expiration) cmH₂O normally.
What is PEL ?
Elastic recoil pressure: the tendency of the inflated lung to recoil back from its inflated state to a deflated state.
(+5 cmH₂O)
What is another term for PEL?
PER
What is a transmural pressure?
The difference of two pressures that have a wall separating them.
What is the formula for PTP (Transpulmonary Pressure)?
PTP = PA - PIP
If cut, what would occur to the ribs? Why?
Ribs would pop out due to the elastic forces of the cartilage and intercostal muscles.
Given PA= 0 and PIP = -5, what would PTP be?
PTP = PA - PIP
PTP = 0 - (-5) = +5 cmH₂O
A pneumothorax would cause what pressure to disappear?
PIP
When do the lungs start to degrade?
At 20yrs old
Which of the following lung volume/capacity diagrams would be indicative of someone standing and which would be indicative of someone laying supine? Why?
- Left is standing:
- Right is supine: supine will ↑abdominal pressure on the diaphragm and reduce FRC.
Why is pre-oxygenation so important for induction?
Supine positioning decreases FRC. Pre-oxygenation counteracts this loss of FRC.
What would be indicated by 2 on the figure below?
VT = 0.5L
What would be indicated by 1 on the figure below?
What is this?
- Inspiratory Reserve Volume (IRV) = 2.5L
- The inspiratory capability of the patient beyond VT.
What would be indicated by 11 on the figure below?
How would this be calculated?
- Inspiratory Capacity (IC) = 3L
- IRV + VT = IC
What would be indicated by 5 on the figure below?
Maximal Inspiration
What would be indicated by 3 on the figure below?
What is this?
- Expiratory Reserve Volume (ERV) = 1.5L
- The amount of air that can be exhaled purposefully by using the abdominal muscles to push up on the diaphragm.
What would be indicated by 9 on the figure below?
What is this and how is it calculated?
- Vital Capacity (VC) = 4.5L
- VC = IRV + VT + ERV
- This is the “working volume” of the lungs (the total amount of air we are capable of moving).
What would be indicated by 6 on the figure below?
Point of maximal expiration
At what point would there no longer be any air in the lungs at all?
7
What would be indicated by 4 on the figure below?
What is this?
- Residual Volume (RV) = 1.5L
- Air left in the lungs after maximal expiration (This can’t be exhaled out)
What would be indicated by 10 on the figure below?
What is this and how is it calculated?
- Functional Residual Capacity (FRC) = 3L
- FRC = ERV + RV
- This is the amount of air the lungs as a baseline
What lung volume/capacity keeps the lungs open and is a buffer against periods of apnea?
FRC
What would be indicated by 12 on the figure below?
What is this and how is it calculated?
- Total Lung Capacity (TLC) = 6L
- The total volume of both lungs at their max.
- TLC = IC + FRC
As one gets older, the loss of ____ necessitates the increasing of expiratory time.
PER
How long is a typical respiratory cycle?
How long is inspiration?
Expiration?
- 5 seconds
- 2 seconds
- 2 seconds
There’s supposed to be a 1 second pause in-between inspiration and expiration.
What is depicted below?
VT during a respiratory cycle
What is depicted in the figure below?
Intrapleural Pressure (PIP) in cmH₂O during the respiratory cycle.
What causes the change in chest pressure at 2 seconds in the figure below?
Diaphragm relaxation.
What is depicted in the figure below?
Airflow in L/s during the respiratory cycle
What is depicted in the figure below?
Alveolar pressure (PA) in cmH₂O during the respiratory cycle.
Describe what is occurring the figure below.
Changes in FRC according to positional change.
If during an expiration the PTP = -7 cmH₂O then what would PEL equal?
+ 7 cmH₂O
What will occur when PER is greater than PIP?
Lungs will recoil back to baseline
When is PA a positive number?
During expiration
When would PA = 0 cmH₂O ?
At the end of expiration
As PIP decreases (becomes increasingly negative) so does ______.
Why is this?
- PA
- Negative intrapleural pressure causes expansion, pulling out the alveoli and making the alveolar pressure negative as well, thus drawing in fresh air.
When does the most negative PA occur?
What is the the most negative PA?
PA = -1 cmH₂O at 1second of inspiration.
When does the fastest inspiratory airflow occur?
At 1 second of inspiration = most negative PA = greatest inspiratory flow.
What lung zone is depicted by 1 in the figure below?
What pressures would be exhibited by this lung?
- Zone 1
- PA > Pa > Pv
How much blood flow is seen in a Zone 1 lung? Who has Zone 1 lungs?
- Very little to no blood flow. Zone 1 lungs are a pathologic condition.
What lung zone is depicted by 2 in the figure below?
What pressures would be exhibited by this lung?
- Zone 2
- Pa > PA > Pv
What lung zone is depicted by 3 in the figure below?
What pressures would be exhibited by this lung?
- Zone 3
- Pa > Pv > PA
What lung zone exhibits pulsatile blood flow?
What lung zone exhibits non-pulsatile continuous blood flow?
What is the reasoning for the difference?
- Pulsatile = Zone 2
- Continuous = Zone 3
- Gravity: ↑ pressure = ↑ perfusion
What lung zone is depicted by 1 in the figure below?
Zone 4
What causes the decrease in blood flow at the very bottom of the lung depicted by the red circle in the figure below?
- Zone 4 decreased blood flow occurs from compression from the lung above as well as the diaphragm.
What would occur with alveolar capillaries during inspiration?
↑ capillary length & ↓ capillary diameter = ↑ alveolar vascular resistance
What would occur with alveolar capillaries during expiration?
↓ capillary length & ↑ capillary diameter = ↓ alveolar capillary resistance.
What would occur with extra-alveolar vessels during inspiration?
↑ vessel diameter = ↓ extra-alveolar vascular resistance
What would occur with extra-alveolar vessels during expiration?
↓ vessel diameter = ↑ extra-alveolar vascular resistance.
At what volume does the lowest pulmonary vascular resistance occur?
Lowest PVR occurs at FRC
At what volume does the highest pulmonary vascular resistance occur?
Highest PVR occurs at Residual Volume (RV)
At what volume is alveolar volume at its greatest?
TLC (Total lung capacity)
At what volume is extra-alveolar volume at its greatest?
RV (Residual volume)
What general relationship do pulmonary blood flow and PVR have?
Inverse (ex. ↑blood flow = ↓PVR)
Which of the following graphics below is indicative of recruitment?
Distension?
How do recruitment and distension of pulmonary vasculature result in decreased PVR?
- Recruitment = more parallel pathways
- Distension = ↑ vessel diameter
What conditions/agents/hormones/etc will cause a increase in PVR?
- SNS neurotransmitters (NE, Epi, α-agonists, etc.)
- Inflammatory mediators
- Alveolar hypoxia
- Alveolar hypercapnia
- Acidotic mixed venous blood
What inflammatory mediators will increase PVR?
- Thromboxane
- Angiotensin
- Histamine
What conditions/agents/hormones/etc will decrease PVR?
- PSNS activity
- ACh
- β-agonists
- PGE1
- PGI2
- Nitric Oxide
- Bradykinin
What effect does acetylcholine have on the lungs?
- Blood vessel dilation (↓PVR)
- Airway constriction
What is the partial pressure of O₂ in dry atmospheric air?
159mmHg
O₂ pressure = 760mmHg x [.21]
What is the formula for partial pressure?
Partial pressure = total pressure x [gas]
What is the partial pressure of 100% humidity? Why does this matter?
47 mmHg : important due to displacing effect on other gasses.
Calculate the partial pressure of inspired humidified O₂ .
PIO₂ = FIO₂ (PB - PH₂O )
PIO₂ = 0.21 (760mmHg - 47mmHg)
PIO₂ = 150 mmHg
What would occur with intra-alveolar O₂ and CO₂ levels if a blocked airway was overcome with 100% FiO₂ and positive pressure?
↑O₂ & ↑CO₂ from “trapping”.
What would normal PAO₂ be?
Why not 150mmHg as this is what’s being delivered?
PAO₂ = 100mmHg due to O₂ absorption into the vasculature.
What is normal PvCO₂?
What is normal PaCO₂?
- PvCO₂ = 45mmHg
- PaCO₂ = 40mmHg
How much CO₂ is delivered to the alveolus via the airways?
What is normal PACO₂?
Why is this?
- 0 mmHg
- 40mmHg
- CO₂ extraction from blood vessels to alveolus for exhalation.
If normal O₂ delivery to the tissues is 20mLO₂/dL and the normal return is 15mLO₂/dL then ΔmLO₂ = 5 mLO₂/dL.
What would the the ΔmLCO₂ be in a normal healthy person?
Why the discrepancy?
4.5 mLCO₂ due to increased hydrophilicity of CO₂.
What would occur with a very negative PISF in the pulmonary interstitium?
Flash Pulmonary Edema
What conditions were discussed in class that can cause pulmonary edema?
Why would each do so?
- LV failure causes ↑PCAP = pulm edema
- Colloid loss causes ↓ πCAP = pulm edema
What does Q typically mean?
Blood flow (perfusion)
What is Kf?
What is it used for?
- Capillary Filtration Coefficient.
Describes how permeable the capillaries are. - Kf is used to convert mmHg to blood flow.
What is the Starling Capillary Equation?
Qf = Kf [(PCAP - PISF) - σ(πCAP - πISF)]
An increase in Kf would correlate with an increase in _______ _________.
capillary permeability
What is HPV (hypoxic pulmonary vasoconstriction) ?
Mechanism by which poorly ventilation portions of the lung are vascularly bypassed through arterial constriction.
Where in the figure below does HPV occur?
How can HPV contribute to right ventricular heart failure?
HPV will vasoconstrict thus increasing PVR = increased RV afterload.
What concept is being described with the diagram in the figure below?
Alveolar size contrasted with blood vessel dilation/perfusion.
Where would we expect greater air flow to occur in the diagram below? (assume an inspiration from FRC)
Why?
Alveoli in apex are more full, therefore air will preferentially fill the bottom portion of the lung.
Where would we expect greater air flow to occur in the diagram below? (assume an inspiration from RV)
Why?
Positive PTP at the base of the lungs would cause air to preferentially fill the apex of the lung prior to the base.
What pulmonary homeostatic mechanism prevents underutilized perfusion to underventilated arteries?
HPV (Hypoxic Pulmonary Vasoconstriction)
When exercising, is it better to increase respiratory rate or depth of breathing to ensure adequate O₂ inhalation?
Why?
Depth of breathing: this is because VA is increased with no wasted air on VD.
In the picture below, what is denoted by:
- 150mls?
- 350mls?
- VD = Dead space volume = 150 mLs
- VA = Alveolar gas volume = 350mLs
What does n represent in our pulmonary equations?
n = breaths per min
How many breaths per minute are taken under normal conditions?
12bpm
What is V̇T?
- V̇T = volume of air inhaled every minute by the lungs.
- V̇T = (n)VT = 6L
How can alveolar minute volume be calculated?
V̇A = V̇T - V̇D
4200mLs = 6000mLs - 1800mLs
What is VE and what is it used for?
VE = minute expiration volume: used to approximate V̇T
V̇T = _____ = VT x n
VE
What percentage of TLC is RV usually?
20%
At which of the following transpulmonary pressures would you expect to find the easiest to fill alveolus (at FRC)?
A. PTP = 0-10 cmH₂O
B. PTP = 10-20 cmH₂O
C. PTP = 20-30 cmH₂O
D. PTP = 30-40 cmH₂O
A. PTP = 0-10 cmH₂O
Where would you expect to find a more positive PIP in the lungs?
Base
Where would you expect to find a more negative PIP in the lungs?
Apex
Where would you expect to find a higher PTP in the lungs?
Apex
Where would you expect to find a lower PTP in the lungs?
Base
Two circles are indicated below, which of these would be indicative of a higher lung compliance?
Green circle (steeper curve)
Would a PTP of 30 cmH₂O be more or less compliant than a PTP of 10 cmH₂O?
30 cmH₂O is less compliant than 10 cmH₂O.
Inspiration from FRC means air goes to the _____ of the lung preferentially.
base
Inspiration from RV means air goes to the _____ of the lung preferentially.
apex/top
Where is the intrapleural pressure located?
If you were to point to an exact space where the negative PIP is located, where is that?
In-between the visceral and parietal pulmonary pleura.
How is alveolar pressure calculated?
PA = PIP + PER
How is transmural pressure calculated?
PTP = PA - PIP
Ex. PTP = 0 - (-5) = +5
