Pulmonary Mechanics I Flashcards
The lung is a negative or positive pressure pump?
Negative - inflates due to a drop of intrapleural P outside the lung
-instead of inc in P w/in lung
What is the function of the external intercostals?
- inspiration during active breathing during exercise
- Lifts ribs up and forward
- Increases anterior-posterior dimension of chest cavity
What is the function of the diaphragm?
- Primary muscle of inspiration
- When it contracts - increases volume of chest cavity
Name some accessory muscles of inspiration?
- Sternomastoid - lifts sternum
- Scalene - lifts upper ribs
others in the face, neck, head
What is the function of the internal intercostals?
- involved in passive expiration
- lowers the ribs
Name some abdominal muscles, involved in expiration?
- Rectus abdominus
- External and internal obliques
- transversus abdominus
What is eupnea?
Normal breathing at a rate of 7.5 mL/min
- active inspiration, passive expiration
- usually only diaphragm for inspiration
What is hyperpnea?
-active breathing during exercise - up to 120ml/min
-inspiration is aided by the external intercostals
-expiration is aided by internal intercostals
& major abdominal muscles
-BOTH inspiration and expiration are active
What is tachypnea?
When breathing is more rapid than normal
What is hypoventilation?
- not breathing enough
- leads to alveolar hypoxia and hypercapnea respiratory acidemia
- -too much CO2 present
What can cause hypoventilation?
Muscular dystrophy or respiratory muscle paralysis
What is hyperventilation?
Breathing faster than required for oxygenation
- alveolar hypocapnea, repiratory alkalosis
- CO2 is below normal range
What can cause hyperventilation?
anxiety or a panic attack
What is the relationship between alveolar pressure and atmospheric pressure during inspiration? during expiration?
- Inspiration - Palv < P atm
2. Expiration - Palv> Patm
What is the goal of an esophageal balloon?
To measure Ppl (intrapleural P)
What is transmural chest wall pressure equal to? What does the value tell us?
Pc = Ppl - Patm
-sets degree of inflation of the chest wall
When is the transmural chest wall pressure negative?
At rest
What is transmural lung pressure equal to? What does the value tell us?
Pl = Palv - Ppl
-sets degree of inflation for the lung
What is total transmural P equal to?
Pt = P alv - Patm = Pc + Pl
When does total transmural P equal zero?
At equilibrium when all muscles are relaxed
Pc = -Pl
What does a spirometer measure? How is it performed?
- Compliance
- inspires then holds breath with glottis open and breaths out
What is the equation for compliance?
Change in volume / change in transmural P
same as:
change in volume / change in Palv
What is FRC?
Lung volume when Pt = 0
- occurs at end expiratory position
- value is 36% of the vital capacity
What forces exist with large lung volumes or Pc>0?
-Elastic recoil of :
Lungs
Chest wall
-Both point inwards
-provide passive expirationWhat forces exist when lung is expanded to resting position of chest wall or Pc =0?
-Only elastic force of the lung opposes inspiration
What forces exist at FRC - Pc =-Pl (Pc<0)?
- outward elastic recoil of wall
- inward elastic recoil of lung
-equilibrium
What is occuring during emphysema?
- alpha antitrypsin usually inhibits neutrophilic proteases
- smoke inhibits alpha antitrypsin
- compliance is elevated - so are FRC, TLC
- exhalation is difficult
What is Pneumoconioses?
- inhalation of dust
- formation of granulomas, fibrous tissue
- decreased compliance
- inhalation is difficult
A saline filled alveoli has eliminated surface tension and therefore has what effect on compliance?
Increased compliance
What is the purpose of surfactant?
Lowers surface tension and increases compliance
What is atelectasis?
partial collapse of the lung
Smaller bubbles have decreased or increased pressure?
Increased - due to smaller radius
Describe a small and large bubble with surfactant?
- equal pressures
- smaller bubble - inc P due to smaller r
- larger bubble - inc surface tension
- less surfactant per unit area
What forces exist during forced expiration, at lung volumes below FRC?
-only one is expansive force of lungs outwards
