Pulmonary Mechanisms II Flashcards
What takes up more time in the respiration cycle….inhalation or exhalation?
Exhalation takes longer
When you inhale, does Ppl increase or decrease?
It decreases (becomes more negative)
Explain the shape of the flow and Palv curves for the dynamics of breathing
The shape of the curves are identical. Flow parallels Palv.
Why does the volume of the lung increase?
Because of an increase in transmutation pressure
What does maximum floe correspond to?
Minimum Palv at mid-inspiration and maximum Palv at mid-expiration
What sets the lung volume?
Transmutes pressure across the lung
When does Ppl reach a minimum?
End of inspiration
1 mm Hg= ?
1.36cm
What is FRC?
The lung volume when Pt equals zero
When is the lung at FRC?
At the end expiratory position
At FRC, Pc= ?
Pc= Pl
At what percent vital capacity does the mechanical equilibrium position fall?
It falls at 36% vital capacity
At volumes below the FRC, what force provides the dominant driving force for the lung to return back to FRC?
The expansive force of the chest wall
What does normal functioning of the lung depend on?
The proper passive elastic properties of the lung and chest wall
What is static compliance?
This determines what particular volume the lung and chest wall will assume for a given tans mural pressure when the elastic vessels are at mechanical equilibrium with no moving air
How is compliance estimated ?
From the inverse slope of a pressure-volume curve
When a weight is placed on a spirometer that is in used, what values increase and what values decrease?
The change in Palv will increase, the change in Vlung will increase, and the change in Vsp will decrease
Why does Ppl increase during measurement of chest wall compliance with a spirometer?
It increases because chest muscles are relaxed against a weighted spirometer
What is dynamic compliance?
An attempt to measure the lung compliance during breathing.
What does an decrease in dynamic compliance indicate?
it indicates increased airway resistance
How is dynamic compliance obtained?
It is obtained from changes in pressure and volume for both end inspiration and end expiration
When will dynamic compliance agree with static compliance?
If equilibrium is attained at end inspiration and end expiration
In a normal individual, does Dynamic compliance change much from breath do breath?
No it does not
Why does the ideal laminar flow equation only give limited qualitative appreciation of the relative importance of a few variables that affect airway resistance?
Because airways are not rigid tubes with uniform diameter, but are dispensable and compressible branching tubes with irregular bores
Where is flow laminar? Where is is turbulent?
At is laminar at the trachea but turbulent at each bifurcation
What is the breakdown of resistance to breathing?
Tissue resistance= 20%
Airway resistance= 80%
What is the breakdown of airway resistance?
Small airways= 10%
Trachea and bronchi=15%
Glottis= 25%
Nose or mouth= 50%
In bronchitis, what is a main site of resistance, that is not normally a major player?
Bronchioles
When is frictional resistance present?
Only during motion (of air)
Why does resistance decrease in the small airways?
Because of all the parallel pathways (increase of cross sectional area)
Resistance ___________ as lung volume ____________.
Decreases
Increases
Does epinephrine increase or decrease airway resistance?
Decrease
Explain the mechanism of how epinephrine decreases airway resistance
1- epi binds with high affinity to beta 2 receptors
2- increase in cAMP
3- protein kinase A is stimulated
4- PKA phosphorylation myosin light chain kinase
5- decreases sensitivity to MLCK for Ca- Calmodulin
6- inhibited binding of myosin CRO’s bridges to actin
7- dilated bronchi and bronchioles result and resistance is reduced
8- beating is enhanced
Is there neural innervation of bronchial smooth muscle?
Yes, but it is sparse
How are bronchial smooth muscles dilated?
Epinephrine acting on beta 2 receptors
How are bronchial smooth muscles contracted?
Through the vagus nerve (Ach) on M receptors
Does histamine bronchoconstrict or brochodilate?
It bronchiconstricts
What increases resistance in asthma?
Inflammatory swelling of bronchial mucosa
What is PEEP?
Positive end-expiratory pressure
Does PEEP increase or decrease in patients on ventilators?
It decreases
How are IVPF curves constructed?
They are constructed from simultaneous measurements of flow rates, lung volumes and alveolar pressures during a series of forced expirations, each more rapid and vigorous than the preceding one until maximal effort is made
What do IVPF curves show?
At low volumes, increasing the driving pressures leads to a maximal flow rate and that the maximal flow rate increases lung volumes
