Respiratory Physiology Flashcards
What respiratory cell
produces protective
glycosaminoglycans and
metabolizes air-borne toxins?
Clara cells (Club Cells)
What respiratory cell
removes particles trapped in
the alveoli?
Dust cells (Alveolar
Macrophages)
What respiratory cell
comprises 96-98% of the
alveoli surface area?
Type I Pneumocyte
For gas exchange
Why is pulmonary flow less
than the systemic flow?
because about 2% of the
systemic cardiac output
bypasses the lungs
The pulmonary circulation has lower pressure and lower resistance than the systemic circulation
This refers to the air in the
conducting zones that do not
undergo gas exchange:
Anatomic Dead Space
Air from the Nose to Terminal Bronchioles (150 ml)
This air space is normally
equal to the anatomic dead
space volume:
Physiologic Dead Space
Anatomic (150mL) + Alveolar Dead Space (0mL)
The formula for minute ventilation:
Tidal volume x breaths/min
The formula for alveolar ventilation:
(tidal volume – physiologic dead space) x breaths/min
Lung volume and Capacity: Amount of air inhaled or exhaled during the relaxed state
Tidal Volume
Normal Value: 500mL divided into: anatomic dead space (150mL) respiratory unit of the lung (350mL)
Lung volume and Capacity:
Remaining air in the lungs after maximal exhalation
Residual Volume
Lung volume and Capacity:
Maintains oxygenation in between breaths
Residual Volume
Lung volume and Capacity: air
in the lungs after expiring tidal volume
Functional Residual Capacity
Marker of lung function
Lung volume and Capacity:
alveolar pressure = atmospheric pressure
Functional Residual Capacity
Marker of lung function
Compute for the ERV:
Vital Capacity – 5L
Tidal Volume – 0.5L
Ins. Capacity – 3.5L
FRC – 2.5”
1.5 L
ERV = Vital capacity minus inspiratory capacity
FRC in patients with
obstructive lung diseases:
High
FEV1/FVC in patients with restrictive lung diseases:
Normal or high
FEV1/FVC in patients with obstructive lung diseases:
Low
What is the primary drive to breathe in COPD patients?
Hypoxic Drive
Low PaO2 stimulating peripheral
chemoreceptors.
Hypercapnic drive is blunted due to compensated respiratory acidosis
What is the main muscle active during normal inspiration?
Diaphragm
Forced Inspiration: External Intercostals,
Accessory Muscles: SCM, Anterior Serrati, Scalene, Alae Nasi, Genioglossus, Arytenoid
What is the main muscle active during normal expiration?
None – Passive normal expiration
Forced Expiration: Internal Intercostals, Abdominal muscles (Rectus Abdominis, Internal and External Oblique, Transversus Abdominis)
This refers to the distensibility of the lungs and chest wall:
Compliance
Where in the pressure-volume
curve is compliance the highest?
Middle range pressures
Complete: Lungs have the
natural tendency to _____ as to
the chest wall’s tendency to __
Collapse; Expand
According to the Law of Laplace, why are pre-term babies prone to high collapsing pressure?
due to: Smaller alveolar radius
Lack mature surfactant
Collapsing pressure is DIRECTLY
proportional to the surface tension and INVERSELY proportional to the alveoli radius
What is the main component of surfactant?
Water
What is the active component of surfactant?
DPPC (Dipalmitoyl Phosphatidylcholine)
What formula is the basis for
airway resistance?
Poiseuille Law
Resistance is DIRECTLY proportional to blood viscosity and vessel length, while INVERSELY proportional to vessel radius
What is the effect of the sympathetic nervous system on the bronchial smooth muscles?
Bronchodilation
What is the effect of histamine
on the bronchial smooth muscles?
Bronchoconstriction
What is the effect of hypoxia on the pulmonary vascular bed?
Vasoconstriction
Shunts blood away from unventilated areas of the lung, where it would be wasted
What is the partial pressure of
oxygen in the mixed venous blood?
40 mmHg
Dry inspired air: 160 mmHg
Humidified Tracheal Air: 150 mmHg
Alveolar Air: 100 mmHg
Systemic Arterial Blood: <100 mmHg
What happens before inspiration (breathing cycle)?
Intrapleural pressure is negative, alveolar pressure = 0
What happens during inspiration (breathing cycle)?
Intrapleural pressure becomes more negative, alveolar pressure becomes more negative
What type of gas exchange where gas equilibrate with the pulmonary capillary near the start of the pulmonary capillary?
Perfusion-limited Gas Exchange
N2O, O2, CO2 under normal conditions
What are examples of substances that undergo diffusion-limited gas
exchange?
CO and O2 during strenuous exercise and disease states
(emphysema, fibrosis)
Gas Does NOT equilibrate even until the end of the pulmonary capillary
How is oxygen transported
98% of the time?
98%: transported via hemoglobin (Hgb) 2%: transported freely dissolved in plasma
What is the composition of adult hemoglobin (chains)?
2 alpha & 2 beta chains
Fetal Hemoglobin (HbF): 2 alpha & 2
gamma chains
What is this phenomenon
where binding of the first O2
molecule increases affinity for
the second O2 molecule and so
forth?
Positive Cooperativity
(O2-HgB DISSOCIATION CURVE)
In the O2-Hg dissociation curve, what are the factors that shift the curve to the right?
Carbon DIOXIDE, Acidosis (Bohr Effect), 2,3 BPG, Exercise & Temperature
In the O2-Hg dissociation curve, what happens to the P50 and oxygen affinity, respectively, when the curve shifts to the right?
P50 increases; affinity decreases
In the O2-Hg dissociation curve, what happens to the oxygen binding (with hemoglobin) when the curve shifts to the left?
Increased binding of O2 with Hgb
This refers to decreased tissue PO2:
Hypoxia
Not always caused by hypoxemia
This refers to decreased arterial PO2:
Hypoxemia
Will lead to hypoxia
What are the two causes of
hypoxemia with a decreased
PaO2 but NORMAL A-a gradient?
High Altitude
Hypoventilation
Decreased PaO2 with High A-a gradient: V/Q defect, diffusion defect, right-to-left shunt
What are the three ways the body transports CO2?
70%: HCO3-
23%: CarbaminoHgb
7%: freely-dissolved in plasma
In the CO2 transport, what is
the principal buffer in the interstitial fluid?
Carbonic Acid
What is the effect of low PAO2
on pulmonary arteries?
Vasoconstriction
What is the PO2 and PCO2
level in patients with high V/Q?
high PO2, low PCO2 (e.g., lung apex)
Normal V/Q Ratio: 0.8
Low V/Q: low PO2, high PCO2 (e.g., lung base)
What is the V/Q of a patient
with blood flow obstruction?
V/Q = Infinite (Dead Space) like pulmonary embolism
V/Q = Zero or Shunt (e.g., R-L shunt, airway obstructions)
Respi-Control Center: Generates basic rhythm for breathing, for normal and/or resting inspiration
DRG
Respi-Control Center: for forced inspiration and expiration (overdrive mechanism)
VRG
Respi-Control Center: Effect of pneumotaxic center on the respiratory rate
Increase RR
Location: Upper Pons
Shortens time for inspiration → ↑ RR
Respi-Control Center: What does the apneustic center do with the inspiration time?
Prolongs inspiration time
Location: Lower Pons
This, decreases RR
The central chemoreceptors respond DIRECTLY to which
factor that increases the RR?
CSF H+
The peripheral chemoreceptors respond MAINLY to which factor to
increase the RR?
PaO2 <60mmHg
Location: Carotid and Aortic Bodies
In a high altitude, what happens to the Alveolar and Arterial PO2?
Decreases
Increases: RR, arterial pH, HgB, 2,3 BPG, pulmonary vascular resistance
What happens to the arterial
PO2 and PCO2 during exercise?
No change
Increases: O2 Consumption, CO2 Production, RR, Venous PCO2, Pulmonary Blood Flow
Decreases: Arterial pH (strenuous exercise due to lactic acidosis)
