Topic 13: Respiratory Physiology Flashcards
(21 cards)
What are the 3 processes involved in exchange of air?
- Pulmonary ventilation
a) inspiration
b) expiration - External Respiration
- Internal Respiration
What is Boyle’s law?
Gas volume is inversely proportional to pressure, provided the temp and the # of gas molecules remain constant (ie. only the space changes)
⬆️gas volume = ⬇️pressure
⬇️gas volume = ⬆️pressure
What are the pressures involved with pulmonary ventilation?
Atmospheric pressure
Intrapulmonary pressure
> p. inside lungs
Intrapleural pressure
> fluid p. in pleural cavity
What determines the stretch in lungs?
• Compliance = effort needed to stretch lungs; low = much effort
• Recoil = ability to return to resting size after stretch
- both = result of elastic CT + surfactant
What are the types of pulmonary ventilation?
Quiet inspiration
Forced inspiration
Quiet expiration
Forced expiration
What happens during quiet inspiration?
i. Diaphragm , external intercostals contract, which ⬆️volume of thoracic cavity
ii. Lungs resist expansion, therefore Pip ⬇️ (756 ⇒ 754 mmHg)
iii. The higher pressure difference between Ppul and Pip pushes
lungs outward ⇒ lungs expand, therefore Ppul ⬇️ (760 ⇒ 758 mmHg)
iv. Air moves in down P gradient (until Ppul = Patm)
What occurs during forced inspiration?
Involves diaphragm, external intercostals and sternocleidomastoids, pectoralis minors, scalenes contract (∴ active). ⇑ vol of thoracic cavity ∴ pressure gradient ⇑, more air in
What occurs during quiet expiration?
• relax muscles ⇒ lungs to resting size ∴ ⇓ thoracic cavity size (passive process)
• volume ⇓ Pip ⇑ (754 ⇒756 mmHg)
• ∴ Ppul ⇑ (760 ⇒ 762 mmHg) ⇒ air moves out down pressure gradient
What determines airway resistance?
- Asthma, bronchitis, emphysema increase airway resistance (R)
~> more difficult to expire than to inspire - inspiratory mechanics open airways/expiratory close airways
- SNS - dilates bronchiolar smooth muscle (bronchodilation)
- PSNS – contracts it (bronchoconstriction)
How is respiratory volume measured?
What does 1 respiration consist of?
Measured with a spirometer
1 inspiration & 1 expiration
What are the different types of respiratory volumes?
a) Tidal Vol. (TV): volume inspired during quiet respiration OR volume expired during quiet respiration (~500ml)
b) Inspiratory Reserve Vol. (IRV): excess volume over TV taken in on a max (deepest) inspiration (~3000ml)
c) Expiratory Reserve Vol. (ERV): excess air over TV pushed out on maximum expiration (~1200ml)
d) Residual Vol. (RV): volume of air in lungs after max expiration (~1200 ml)
e) Minute Respiratory Vol. = Tidal Vol. x Respiratory Rate
e.g. = 500mL x 12 breaths/min
= ~ 6 L/min (on average)
f) Forced Expiratory Vol. in 1 second (FEV1): volume expired in 1 second, with max effort, following max inspiration
Respiratory capacities are a combination of 2 or more volumes. Break them down
a) Inspiratory Capacity (IC)
= TV + IRV
b) Vital Capacity (VC)
= TV + IRV + ERV
~> largest volume in/out of lungs
c) Total Lung Capacity (TLC)
~> max amount lungs can hold
= TV + IRV + ERV + RV (=VC + RV)
Forced Expiratory Vol. (FEV1) is measured while measuring vital capacity (VC) and expressed as % VC (usually FEV1 = ~80% VC). These measurements allow for the diagnoses of what?
- Obstructive Disorders
-e.g. emphysema, asthma, cystic fibrosis
-hard to expire = ⬆️resistance
-∴ high RV, low VC, FEV1 < 80% VC - Restrictive Disorders
-e.g. scoliosis, pneumothorax
-restrict lung expansion
-hard to inspire
-∴ IC low, VC low, FEV1 low (but FEV1 = 80% VC)
This involves diffusion of O2 from blood into ISF and cells, and diffusion of CO2 from the cells into ISF and then the blood
Internal respiration
What prevents the lungs from collapsing?
a) Pip is always below Ppul
• pneumothorax = air into pleural cavity
~> Patm = Ppul = Pip
∴ lungs collapse, thoracic wall expands
b) Presence of surfactant
• = lipoprotein/phospholipid mixture
~> in watery film coating alveoli - ⇓ surface tension
~> allows easier stretch of lungs (⇑ compliance)
~> prevents alveolar collapse
• respiratory distress syndrome
~> newborns < 7 months gestation
~> inadequate surfactant ∴ alveoli tend to collapse (low compliance)
~> ∴ effort high ⇒ exhaustion, death
Describe some properties of intrapleural pressure
• always < Ppul
• usually < Patm = ~4 mmHg less = 756mmHg (at rest)
•Pip is usually lower than Patm b/c the thoracic (chest) wall expands outward, and the lungs recoil inward, but are held together by the pleural fluid
External respiration involves the exchange of O2 and CO2 between the blood and alveoli. What aids this exchange?
a) thin respiratory membrane (2 cells and basement membrane)
b) large surface area - capillaries, alveoli
> RBC move single file through capillaries ∴ max RBC exposure to gases
c) blood velocity ⬇️compared to gas diffusion rates (so RBCs have time to pick up/release gases)
What is the partial pressure of gasses?
The pressure exerted by a single gas in a mixture of gases
O2 is carried by binding to hemoglobin 98.5% of the time. How is the rest of the O2 transported?
Dissolved in plasma
a) At lung capillaries (ext. resp)
- O2 moves from high pressure in lungs to low pressure in capillary
b) At tissue capillaries (int. resp)
- diffuses: capillary ~> ISF ~> cell
True or false: each hemoglobin can bind 6 O2 molecules
False. Hemoglobin can bind 4 O2 molecules
What are the 3 ways CO2 is carried?
- Dissolved in plasma - 8%
a) at lungs (external)
b) at tissues (internal) - Bound to hemoglobin - 20%
- As bicarbonate ions - 72%
a) in RBC at tissues
b) in RBC at lungs
