Lung Ventilation & Compliance Flashcards
RDS
Respiratory Distress Syndrome
What is the worry about a premature newborn’s respiratory system?
Surfactant deficiency (difficult to breath)
Anatomic vs. Alveolar Dead Space
Anatomic: air resides in the conducting airways
Alveolar: amount of wasted ventilation (blood supply blocked; ventilation greater than perfusion)
If tidal volume is 500 mL, how much is anatomic dead space
150 mL
In healthy lungs, Physiologic Dead Space should be nearly equivalent to…
Anatomic Dead Space (minimal alveolar dead space)
What can contribute to Alveolar Dead Space
- Obstruction to blood flow (embolism)
2. Ventilation is greater than the perfusion can handle
What two resistances must be overcome during ventilation?
Chest Wall resistance
Airway resistance
Why is positive end expiratory pressure (PEEP) important during lung ventilation?
It is hard to inflate a completely deflated lung, so always ensuring a positive pressure in the lungs helps keep alveoli somewhat open, and thus ease ventilation efforts
Elastic recoil assists in (inflation/deflation)
Deflation
Compliance assists in (inflation/deflation)
Inflation
What two factors help determine how hard/easy it is to fill your lungs with air (Lung Compliance)?
Elastic recoil Surface tension (surfactant)
According to LaPlace’s Law, the smaller the bubble the ________ the pressure has to be to support the surface tension
higher (P= 2T/r)
Why is surface tension important for alveoli?
their thin walls and short radii at end-expiration make them susceptible to collapse as a result of surface tension. If large and small alveoli were connected via a common airway, the higher pressure in the smaller alveolus would force air into the larger alveolus, and the small alveolus would collapse
Surfactant is a mixture primarily made up of..
phospholipids (90%); majorly DPPC
- other 10% with proteins including surfactant proteins
Pulmonary surfactant is made by what cell?
Alveolar Type II cells (cuboidal cells at alveolar septa)
Pulmonary surfactant metabolism disorders are treated with surfactant replacement therapy, but not cured by it (True or False)
True; only a lung transplant can cure
Interconnecting walls stabilize neighboring alveoli. In effect neighboring alveoli tug on each other to prevent collapse of any single alveolus, and also help each other open up during inspiration
Alveolar Interdependence
Lung disease where the breakdown of lung connective tissue causes decreased elastic recoil. These lungs have very high compliance: they are very easy to inflate, but have very little elastic recoil necessary for a passive expiration, thus a large FRC (Emphysema or Fibrosis)
Emphysema
Lung disease where the lung connective tissue is thickened by the pathologic deposition of tough fibrotic tissue. The result is a very stiff lung, with a low compliance that is difficult to inflate. (Emphysema or Fibrosis)
Fibrosis
puncture of the chest wall and/or visceral pleura allowing entry of air into the pleural space, disrupting the lung-chest coupling and therefore blocks mechanical energy transfer. This increases work of breathing.
Pneumothorax
In healthy individuals, total body O2 consumption at rest is about
5% or less
What might increase one’s work of breathing
Exercise Obesity Pulmonary Fibrosis (reduced compliance) RDS Obstructive diseases
The total volume of the lungs that does not participate in gas exchange is known as
physiological dead space
The ______ the hydrophobicity of the medium in contact with water, the _______ the surface tension
greater; greater
Most gases are very _________ than water
hydrophobic
What surfactant proteins are essential for formation of the surfactant layer?
SPB and SPC
What surfactant proteins are members of the collectin family and are active in lung defense?
SPA & SPD
What is the organelle that secretes surfactant in type II alveolar cells?
lamellar bodies
In the alveolus, a phospholipid monolayer of surfactant exists at the ________
air-liquid interface
Polar lipid heads face towards______, and hydrophobic lipid tails stick into _____
alveolar liquid; gas phase
During alveolar expansion (inspiration), what happens to the SA, phospholipid molecules, water molecules, and surface tension?
- SA: increases
- Phospholipid: more separated
- Water molecule: exposed more to air
- Surface tension: increases
During alveolar compression (expiration), what happens to the SA, phospholipid molecules, water molecules, and surface tension?
- SA: decreases
- Phospholipid: more complete/closer
- Water molecule: less exposed to air
- Surface tension: decreases
Alveolar interdependence increases the compliance of the lung especially during ______
expiration when alveoli becomes smaller
What two types of compliance contribute to the work needed for ventilation?
- Lung Compliance
- Chest Compliance
- Lung Compliance + Chest Compliance = Total Compliance
What factors can decrease chest wall compliance?
- obesity
- musculoskeletal disorders affecting rib cage
- fibrothorax (scarring or fibrosis of the pleural space)
The concept in which the efficient transfer of energy from one component to the other component decreases the work of breathing.
- Energy released from the lung and transferred to the ribs/chest wall OR vise versa
See-saw exchange of mechanical energy
In emphysema, the lung elastance is ______ due to destruction of lung elastin fibers. FRC is ________
reduced; increased (larger volume of air present in the lungs at the end of passive expiration)
Pneumothorax disrupts _______ that decreases the work of breathing in normal lung?
mechanical coupling of the lung and chest wall (mechanical exchange of energy)
