Resp 2- Dynamic breathing Flashcards
What are the dynamic forces of breathing?
Resistance/ flow/ turbulence
where is the most resistance in the breathing airways?
in the trachea (90%) as this might have the largest diameter however there is only one compare to the cumulative diameter in the alveoli sac.
what is poseuille’s law ?
Flow = change in pressure x pie x radius^4 / 8 x viscosity x tube lenght
Flow = (change in pressure) / (Resistance)
what does poiseuille’s law suggest ?
Smallest tubes wwould have the largest resistanc however bc there are so many in the lungs the cumulative resistance is lower.
what factors determin resistance?
- Lung volume/ braching
- Bronchiolar smooth muscle tone
- density and viscosity of gases- Affected by altitude/ different environment (viscosity) / laminar flow (gas density)
Name 4 facors that reduce bronchiolar smooth muscle tube radius?
- Parasympathetic activity
- ACh
- irritants- smoke/ allergens
- Decreased alveolar PCO2
name 4 factors that increase bronchiloar smooth muscle tubes?
- Sympathetic activity
- Pulmonary strech
- NAdr
- Adr (salbutamol)
what is asthma and resistance ?
it is hyper senstivity of airway smooth muscle contraction thickening the bronchial smooth muscle
how is asthma linked to resistance and breathing ?
convective gas flow in the lungs is less efficient
Gas flow slows to the molecular diffusion rate in the upper ariways resultsi in poor gas exhange in the respiratory acinus.
Gas fails to reach the distal region in the respiratory zone cause alveolar pCO2 to rise
lungs ceases to oxygenate blood efficiently due to reversal of the proper alveolar bohr and haldane effects.
what happens to airways resistance during inhalation ?
Airway resistances falls as gas flows and lung volume increases becase airways expand physically
what is the role of the upper airways during exhalation ?
The resistance in the upper airways helps to eep aiway pressure high to mazimise gas movement out of alveoli
what is Transmural pressure ?
the difference between alveolus and intraplural space pressure.
when does inspiration occur?
when intraplural pressure falls below 5cmH2O as chest cavity expands.
airway pressure < than external atmosphereic pressure.
transmural presure is the greatest in conducting airways and smallest in the alveolar respiratory zone during inspiration.
this causes a greate force to allow gas to move into the lungs
movement of air is therefore HIGH to LOW !!!
What happens at End inspiration?
gas movement sdtops a lungs reach the miximal distension.
airway pressure is back to 0cm H2O
intraplural pressure returns to -5cm H20
what happens at expiration to intraplural pressure and alvola pressure
resp muscles relax and lungs deflate bc of elastic recoil.
intraplural pressure and alvolar pressure is postive due to elastic recoil. alvolar pressure> intraplural pressure in the lavolar resp zone/
gas moves from resp to conducting zone there is alot os resistance in the upper aireways.
alervolar pressure falls below intraplural pressure.
dirivng force for the air then is at the lower airways.
what is pursed lips breathing COPD?
raises air pressure above intraplural pressure along the entire lenght of the aiways.
sitting hunched abodmen is forced into lower portions of the lunsg and the lips creates maximal resistance.
Therefore lower lunsg compressed and airway pressure exceeds intraplural pressure.
what is COPD characterised by?
the increased resistance to air flow.
how can the blue puffer be identified ?
alveoli destruction
reduced surface area
reduced elasticity
define work of breathing ?
to overcome elastic and non elastic resistance
