Cardioresp mechanics Flashcards
What is inspiration?
The process that facilitates the movement of air to enter into the lungs
What is expiration?
Process that causes air to be expelled from the lungs
What are the two main muscle groups for inspiration?
Diaphragm
External intercostal muscles
What comprises a respiratory cycle?
One sequence of inspiration and expiration
During inspiration what happens to the diaphragm?
Diaphragm contracts, pulls inferiorly towards the abdominal cavity resulting in a larger thoracic cavity-> Increases volume subsequently decreases the intrathoracic pressure
What happens to the external intercostal muscles during inspiration?
Contracts
Ribs move outwards and upwards, causing ribcage expansion to increase the thoracic cavity volume
Lung stretches and expands, decreasing the inter alveolar pressure, the pressure gradient enables air to move into the lungs
How happens during expiration?
Expiration is passive
Elasticity of the lung tissues causes lung recoil -> Diaphragm and intercostal muscles relax following inspiration
Thoracic cavity and lungs decrease volume to increase the interpulmonary pressure > atmospheric pressure.
Pressure gradient causes air to leave lungs
What is the protocol for conducting a pulmonary function test?
1) Patient wears nose clip
2) Patient wraps lips rounds mouthpiece
3) Patient completes at least one tidal breath
4) Patient inhales steadily to total lung capacity
5) Patient exhales as hard and fast as possible
6) Exhalation continues until residual volume is reached
7) Patient immediately inhales to TLC
8) Visually inspect performance and volume time curve,
In obstructive diseases in which direction does displacement occur along the x-axis of normal flow volume loops?
Left displacement
In restricted diseases in which direction does x-axis directional displacement occur on a pressure flow volume loop?
Right displacement
What are the main features on an obstructive pressure flow volume loop?
Indentation (coving) on pressure volume loop.
The expiration curve is indented
The TLC is minimally changed
In restrictive disease why is the pressure volume loop narrower?
Restrictive diseases reduces the capacity within the lungs
In an extrathoracic obstruction which curve is blunted?
The inspiratory curve is bounded
Why is the inspiratory curve blunted for an extra-thoracic obstruction?
Inspiration displaces tumour, obstruction favourable in the direction that covers the trachea
EXPIRATION NORMAL
Impedes airflow into the lungs
A blunted expiratory curve in a flow volume loop is associated with which type of obstruction?
Intrathoracic obstruction
Why is there expiratory blunting in an intrathoracic obstructionβ?
Does not impeded inspiration however expiration is significantly reduced, forced expiration obstructs airflow
How does COPD affect flow volume loops?
COPD curve shifted to the left, considering the lungs are filled with air initially -> Greater residual volume
Narrower airways β> Lower peak, & coving of curve
What is Poiseuilles law? (Equation)
πΉπππππππππ= ππΌπ/(π π^π )
What relationship can be established between resistance and radius?
Considering that length and viscosity of liquid is constant, it can be assumed that resistance is inversely proportion to (Radius)^4
What is the relationship established for Boyleβs Law?
Pressure of a gas is inversely proportional to its volume
How are small airway radii compensated in terms of airflow?
Smaller the calibre of airways, radius is reduced ο Greater resistance. However it is important to consider flow ο low flow through a small tube, and high flow through large tube ο Greater resistance in high flow environment.
How does the trachea accommodates for reduced radius?
Trachea bifurcates into primary bronchi ο Bronchioles ο Flow significantly decreases (accommodating reduced radius) ο minimises resistance.
Which airway generation results in peak resistance?
Fourth generation
What is conductance?
Ability for airways to conduct and enable air to pass through, this increases with increasing lung volume - decreases resistance
During inspiration how does resistance decrease?
During inspiration intrathoracic and and airway expansion occurs - airway radius increases therefore decreasing resistance
Which muscle regulates the diameters and resistance of arterioles and small arteries?
Smooth muscle
What happens to pressure across circulation?
The pressure declines across the circulation due to vicious (frictional) pressure losses) - small arteries and arterioles present majority of resistance to flow.
What is the MAP calculation relating cardiac output?
MAP = CO X PVR
What are the assumptions for equating mean arteriole pressure with cardiac output x PVR?
Laminar flow
Rigid vessels
Right atria, pressure is negligible
Blood can be directed by specific contraction and relaxation of the blood vessels that supply particular vascular bed required
What are the three main variables of blood flow resistance?
Fluid viscosity (n): Not fixed but in most physiological conditions, this remains approximately constant Length of the tube (Fixed) - length of blood vessels remains constant Inner radius of tube (R), variable, and the main determinant of resistance