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What is the Tidal Volume?
The amount inspired or amount expired in a normal resting breath
What is the inspiratory reserve volume?
Volume you can inspire beyond the tidal volume
What is the expiratory reserve volume?
Volume you can expire beyond the tidal volume
What is the Vital Capacity? Give 2 definitions.
1. Volume difference between maximum inspiration and maximum expiration.

2. Vital Capacity (VC) = Tidal Volume (TV) + Inspiratory Reserve Volume (IRV) + Expiratory Reserve Volume (ERV)
What is the Residual Volume?
Volume remaining after complete expiration.
What is the functional residual capacity?
Expiratory Reserve Volume + Residual Volume
What is the Total Lung Capacity?
Vital Capacity + Residual Volume
What are the 2 structures and the 3 compartments in the "2-structure 3-compartment" model?
2 structures
  • Lungs
  • Chest wall
3 compartments
  • Alveoli
  • Intrapleural space
  • Atmosphere
What are the natural tendencies of the lungs and the chest wall?
  • Lungs: Recoil inward
  • Chest wall: Recoil outward
What 2 forces contribute to the Elastic recoil of the lungs?
1. Elasticity of cells and ECM in lung tissue
2. Surface tension in alveoli
What 2 forces contribute to the Elastic recoil of the chest wall?
1. Tendency for ribs to spring outward
2. Resting tension of the muscle of respiration
What is the transpleural pressure equation?
Ptp = Palv - Ppl
What is the transpleural pressure (Ptp) at rest (at FRC)?
+5cm H2O
Describe 5 steps in inspiration
1. Inspiratory muscles contract
2. Increased volume in chest lowers pressure in pleural space
3. Alveoli and lungs inflate due to increased transpleural pressure
4. Alveoli expand and pressure drops below atmospheric pressure causing air to enter alveoli
5. Air pressure in alveoli eventually equals with atmospheric pressure
What are the quiet/forced inspiratory muscles?
Quiet:
  • Diaphragm
  • External intercostals

Forced:
  • Diaphragm
  • External intercostals
  • Accessory muscles 
What are the quiet/forced expiratory muscles?
Quiet
  • Passive (no muscles)
Forced
  • Abdominal muscles
  • Internal intercostals
  • Neck/back muscles
Name the conducting airways (4). What is the function of the conducting airways?
Airways:

Trachea → Bronchi → Bronchioles → Terminal bronchioles

Function: Conduct air
Name the structures of the respiratory zone (3). What do these contain and what is the function?
Structures:

Respiratory bronchioles → Alveolar ducts → Alveolar sacs

They contain alveoli which function in gas exchange.
Muscular contraction during inspiration provides the force necessary to overcome the what 4 resistances?
Inward elastic recoil of the lungs
  • 1. Surface area tension (alveoli)
  • 2. Elastic tissue (cells, ECM)
Frictional resistance
  • 3. Airflow resistance
  • 4. Tissue resistance
What happens to cells and ECM in Emphysema? How does this affect elasticity?
Loss of elastic in cells and ECM.

Elastic recoil
What happens to cells and ECM in Pulmonary Fibrosis? How does this affect elasticity?
Collagen deposition in cells and ECM.

↑ Elastic recoil
What is effect of emphysema on lung filling, and on RV/FRC/TLC?
Lungs are easier to fill, but are prone to airspace collapse

RV/FRC/TLC
What is effect of fibrosis on lung filling, and on RV/FRC/TLC?
Lungs are harder to fill

↓ RV/FRC/TLC
What 2 effects does surface tension of alveoli have?
  • ↑ inward elastic recoil
  • ↑ alveolar instability
What effect does pulmonary surfactant have on surface tension?
Pulmonary surfactant →  ↓ Surface tension

Surfactant interrupts hydrogen bonding and reduces surface tension, thereby reducing inward elastic recoil and stabilizing alveoli
What are 2 symptoms in Neonatal Respiratory Distress Syndrome?
No surfactant, so:
  • 1. Difficult to inflate lungs (alveoli collapse easily)
  • 2. Atelectasis 
What is compliance?
Essentially how easy it is to expand the lung.
  • ie. Amount of volume change per unit of pressure
Emphysema
Fibrosis
What 2 factors affect airway resistance?
  • Airway diameter
    ↓diameter → ↑resistance

  • Pattern of airflow
    Laminar →  ↓resistance
    Turbulent  → ↑resistance
What is the normal shape of the compliance curve?
Curvilinear
What is minute ventilation? Give an equation. How much air is this usually?
Volume of air moved in or out of the lungs per minute (Includes alveolar and dead space)

= Tidal Volume x Respiratory Rate

About 6.0 L/min
What is alveolar ventilation? Give an equation. How much air is this usually?
Volume of air breathed per minute that reaches alveoli and participates in gas exchange

= Alveolar Volume x Respiratory rate

About 4.2 L/min
What is dead space ventilation? Give an equation. How much air is this usually?
Volume of air breathed per minute that does not participate in gas exchange.

= Anatomic dead space (conducting airways) + Alveolar dead space (air reaching alveoli that does not participate in gas exchange)
What is physiological dead space?
Physiological dead space = Anatomic dead space + Alveolar dead space

Anatomic DS: 150ml
Alveolar DS: 25ml
How much O2 (mmHg) and CO2 (mmHg) are in the dry air?
O2: 160 mmHg
CO2: 0 mmHg
How much O2 (mmHg) and CO2 (mmHg) are in the inspired air?
O2: 150 mmHg
CO2: 0 mmHg
How much O2 (mmHg) and CO2 (mmHg) are in the alveolar gas?
O2: 100 mmHg
CO2: 40 mmHg
How much O2 (mmHg) and CO2 (mmHg) are in the mixed venous blood?
O2: 40 mmHg
CO2: 46 mmHg
How much O2 (mmHg) and CO2 (mmHg) are in the arterial blood?
O2: 95 mmHg
CO2: 40 mmHg
What is the vapour pressure of water (PH2O) in the atmosphere at sea level?
47 mmHg
Gas exchange is dependent upon what 3 things?
  • Ventilation
  • Perfusion
  • Diffusion
What is end-capillary equilibration?
Point at gas exchange where:

PaO2 = PAO2
and
PaCO2 = PACO2
What do Big A and Little a mean?
A = alveolar
a = arterial
What is the alveolar ventilation equation? What does it mean?
PaCO2 = VCO2  ⁄ VA
 

Arterial CO2 = CO2 production rate / avelolar ventilation rate
What happens to total cross sectional area as the air transitions from conducting zone to respiratory zone?
It increases signficantly
What happens to resistance as the air transitions from conducting zone to respiratory zone? Why?
The resistance goes down in the respiratory zone.

Even though airway resistance increases as radius decreases, there is so much more cross sectional area (in the respiratory zone) that overall resistance goes down .
What is FEV1 / FVC ratio? What do increased or decreased levels mean?
Volume of forced expired air (in 1 second) / Forced vital capacity.

88% Restrictive disease (eg. fibrosis)

Normal: 80%

 65% Obstructive disease (eg. Asthma)
What is the FEF (25%-75%)? What does it mean?
From Forced Inspiration, it is the rate that lungs are emptied during expiration measured from 25% volume expired, to 75% volume expired.

Decreased levels indicate obstructive airway disease, particularly of the small airways.
What is a typical level for PaCO2 in a healthy individual?
38-42 mmHg
What is hypoventilation?
Decreased ventilation to a level less than what is required to maintain metabolic requirements.

Results in hypercapnia (increased PaCO2)
What is hyperventilation?
Increased ventilation to a level that is higher than what is needed to maintain metabolic requirements.

Results in hypocapnia (Decreased PaCO2)
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