Dynamic Mechanics of Breathing Flashcards
What two zones is the lung split into?
Conducting zone-branching
Transit and Respiratory Zone- Alveoli and sacs
Why is the lungs not that effective?
Gas has to move in and out through the same set of tubes that deliver gas to the alveolar
Provides resistance
Even though the tubes are small and generatate a lot of resistance. What can be said about the cumalative resistance?
Its lower due to the amount of tubes
Whatv are the factors that determine resistance?
Lung volume and branching
Bronchiolar smooth muscle tone
Density and viscosity of gas
What is bronchiolar smooth muscle?
Smooth muscle that lines upper airway and influences tube radius.
Consequences for altering gas flow in the airways
How is the bronchiolar tibe radius decreased?
- Parasympathetic activity
- Ach neurotransmission
- Irritants (smoke, allergens)
- Decreased alveolar PCO2
How is the bronchiolar tube radius increased?
- Sympathetic activity
- Pulmonary stretch
- NAdr (neutral to week)
- Adr
What diseases are linked to resistance?
Asthma COPD
Describe an asthmatic airway
Narrowed airway
Increased airway in smooth muscle
Describe an asthmatic airway during an asthma attack
Constricted airway
Contracted airway in smooth muscle
Describe what happens during an asthma attack
Allergic inflammation of the airways
Hyper-reactivity of airway smooth muscle contraction
Bronchial smooth muscle thickening
What does contraction of parabronchial smooth muscle do?
Raises upper airway resistance
What raises the convection of the lung?
Deep and fast breathing
Describe the workings of an asthmatic lung compared to a healthy lung
- Oxygen slows to its molecular velocity in the lung much quicker than a regular lung causing poor gas exchange
- Gas fails to penetrate to distal regions of respiratory zone causing alveolar pCO2 to rise
- Lung ceases to oxygenate Hb efficiently due to reversal of proper alveolar Bohr and haldnae effects
Where does the asthmatic wheeze come from?
Laminar flow
Complicated by dichotomous branching- Eddies and turbulence
How is airway resistance measured?
Whole body Plethysmography
During inhalation, what happens to airway resistance as gas flow and lung volume increase?
Falls
During exhalation, the resistance of the upper airways helps to keep what?
Pressure high to maximise gas movement out of alveoli
What does exhalation work against?
Smooth muscle contraction and upper airway resistance
What is COPD characteriased by?
Increased resistance to air flow
Might be caused by mucus in the airways
Describe the ‘blue puffer’ in patients with COPD
1)Alveoli destruction
2)Reduced surface area
3)Reduced elasticity
Patient oxygenation is poor (hence blue)
Why would patients with COPD breath with pursed lips?
Maintaining airway pressure high all the way through conducting zone through lung
Using dynmaic compression to raise airway pressure that allows to clear the lung of gas from lower airways
Energetically exhausting
What is meant by work of breathing?
To overcome elastic and non elastic resistances
What is the work of inspiration?
Energy input required to overcome elastic component and energy input required to overcome surface tension
What is meant by work of expiration?
Energy input to overcome airway and tissue resistance
Where is the energy expended during panting breathing pattern?
Inhalation- Surface tension
Exhalation- Dynamic compression upper airway resistance
Where is the energy expended during deep breathing (athlete before race)?
Inhalation- Elastic component
