Ventilation Flashcards
Minute ventilation
Volume of air expired per minute
Respiratory rate
Frequency of breathing per minute
Rf
Alveolar ventilation
Volume of air reaching respiratory zone per minute
V(alv)
= Breathing frequency x (Tidal volume- physiological dead space)
Respiration
Process of generating ATP either with excess of oxygen (aerobic) or shortfall (anaerobic)
Anatomical dead space
Capacity of airways incapable of undertaking gas exchange
Alveolar dead space
Capacity of the airways that should be able to undertake gas exchange but cannot (e.g. hypoperfused alveoli- not enough blood flow)
Physiological dead space
Sum of alveolar and anatomical dead space
Hypoventilation
Deficient ventilation of the lungs; unable to meet metabolic demand (increased PCO2 – acidosis)
Hyperventilation
Excessive ventilation of the lungs atop of metabolic demand (results in reduced PCO2 - alkalosis)
Hyperpnoea
Increased depth of breathing (to meet metabolic demand)
Hypopnoea
Decreased depth of breathing (inadequate to meet metabolic demand)
Apnoea
Cessation of breathing (no air movement)
Dyspnoea
Difficulty in breathing
Bradypnoea
Abnormally slow breathing rate
Tachypnoea
Abnormally fast breathing rate
Orthopnoea
Positional difficulty in breathing (when lying down)
Tidal Volume
Effect of exercise?
Amount of air breathing in and out per breath
Increased tidal volume
Inspiratory reserve volume
Amount of extra air you can get in after taking in a normal breath
Expiratory reserve volume
Amount of extra air you can get out after breathing out normally
Residual volume
Benefit?
Amount of air left after complete forced exhalation
Airways are moist+ will stick together if there is no residual volume= diffucult to seperate again
Difference between volumes + capacities
Volumes don’t overlap
Adding volumes together= capacities
Vital capacity
Importance
IRV+ TV+ ERV
Measure of how much air you can adjust and influence
Possible to measure this
Functional residual capacity
ERV+ RV
Amount of air left in lungs after a normal expiration
Inspiratory capacity
IRV+ TV
Amount of air you can bring in from the ‘neutral position’
Total lung capacity
IRV+ TV+ ERV+ RV
Factors that affect lung volumes+ capacities?
Body size Sex (Males= larger) Disease (pulmonary, neurological) Age Fitness (Innate (more signficant), training)
Dead space components
What leads to decreased dead space?
What leads to increased dead space?
Anatomical dead space
16 generations (bifocations)
No gas exchange
Typicaly 150 mL in adults at FRC
Alveolar dead space Alveoli without blood supply No gas exchange 0 mL in adults Called alveolar dead space
Tracheostomy= decreased dead space
Anaesthetic circuit= increased dead space
Poiseuille’s Law
Resistance= (8ƞl)/ 𝜋𝑟⁴ ƞ= Viscosity of inspired gas l= length of airway r= radius of airway At higher pressures, can't use a snorkel
Boyle’s Law
P(gas) is proportional to 1/ V(gas)
Increase pressure= decrease volume in lungs
Tidal breathing process
Forces?
Units of measurement for pressure
- At start, functional residual capacity in lungs
- Inspiratory muscles contract= pulls lung tissue apart
- Creates negative pressure= lower alveolar pressure
- Creates pressure gradient= generates flow until pressures balance out (at 0cm of water)
Ambient pressure= 0cm of water - Removal of inspiratory effort= lungs recoil+ compress air= pressure becomes more positive
- Lower ambient pressure= creates pressure gradient= generates flow from lungs to outside
Graph of tidal breathing
P(alv) and change in alveolar volume over time
(slide 11, lecture 3)
-
Chest-wall relationship
When are the forces at equilibrium?
Inspiration?
Expiration?
Chest wall= tendency to spring outwards
Lung= tendency to recoil inwards
At end-tidal expiration (functional residual capacity)
Inspiration= inspiratory muscle effort+ chest recoil> lung recoil
Expiration= chest recoil< lung recoil+ expiratory muscle effort
Chest-wall anatomy
Lungs surrounded by?
Inner surface of the chest wall covered by?
In between? Contains?
Layers?
Ribcage+ lung tissue= anatomically linked by pleural space
Lungs surrounded by visceral pleural membrane
Inner surface covered by parietal pleural membrane
In between= pleural cavity (gap between pleural membranes)= FIXED volume, contains protein-rich pleural fluid
Skeletal muscle, skeleton, parietal pleura, visceral pleura, lung
Haemothorax
Intrapleural vessel bleeding inside lung= compresses lung= less space to expand and fill with air= harder to breathe
Pneumothorax
Perforated lung/ chest wall: allows air from outside/ inside lung/ blood into the space because the space is a partial vacuum= impairs lung function
(like a smaller lung in the same chest cavity)
Generating airflow- 2 ways
Eg?
Negative pressure breathing: P(alv)< P(atm) (P(alv) is reduced), normal
Positive pressure breathing: P(atm) > P(alv) (P(atm) is increased), mechanical ventilation, CPR
Three compartment model
At rest?
Transmural pressures?
At rest:
Alveolar pressure P(alv)= 0cmH20
Atmospheric pressure P(atm) (unless CPR/ ventilator)= 0cmH20
Intrapleural pressure P(pl)= typically -5cmH20 at rest, under negative pressure because of chest recoiling outwards and the lung recoiling inwards which creates tension.
Transpulmonary pressure P(TP)= P(alv)- P(pl)
Transthoracic pressure P(TT)= P(pl)- P(atm)
Transrespiratory pressure P(RS)= P(alv)- P(atm), dictates air flow: positive= air flows out, negative= air flows in, 0=rest
How is the mechanics of ventilation achieved?
Diaphragm= pulling force in one direction (syringe)
Respiratory muscles= Upwards+ outwards swinging force (bucket handle)
X-axis= pressure (cmH20) Y-axis= volume (L)
Draw graph of Independent chest wall Intact Lung Independent lung (slide18, lecture 3), label FRC, TLC, wall, Neutral postion of lung, Neutral position of chest, RV
If lungs= intact+ working, where on graph are you?
0 pressure, 3L volume
Intact lung= sigmoid shaped: middle of volumes= amount volume that changes per unit pressure= more signficant that at extremes, because less effort to change things
e.g. deep breath at 95%lung capacity= harder to breath in
Intact lung= product of independent chest wall+ indepedent lung
Types of pulmonary function tests
Volume time curve
Peak flow
Volume time curve Produced with what equipment? Protocol X axis, Y axis? Normal shape of curve
Spirometry Noseclip Inhales to TLC Wraps lips around mouthpiece Exhales as hard+ fast as possible Exhalation continues until RV= reached/ 6 seconds passed X axis= Time (s), Y axis= Volume (L) Increase sharply at beginning, plateau
Measurements to find on volume-time curve
Effect of restrictive disorder?
Effect of obstructive disorder?
FVC= forced vital capacity, highest volume on curve, empty lungs as quickly as possible, restrictive disorder has a much lower value
FEV1= Forced expiratory volume, volume expired in 1 second, obstructive disorder has a much lower value but restrictive doesn’t
FET= Forced expiratory time (don’t need to know much, it’s how long it took for plateau to start)
FEV1/FVC ratio compares how much air is coming out in 1 second
Peak expiratory flow rate (L/min)= steepest part of graph
Peak flow
Protocol
Used for?
X axis, Y axis?
Noseclip Inhales to TLC Wrap lips round mouthpiece Exhale as hard+ fast as possible- don't have to reach RV Repeat twice+ take highest measurement Monitors asthma Peak expiratory flow rate(L/min)
Flow-volume loop Draw one (slide22, lecture 3) Effect of mild obstructive disease? Effect of severe obstructive disease? Effect of restrictive disease? (slide23, lecture 3) Effect of variable extrathoracic obstruction? Effect of variable intrathoracic obstruction? Effect of fixed airway obstruction?
COPD (Mild Obstructive disease): curve has moved upwards because lungs are larger in COPD (Surface area goes down but overall volume increases), peak is lower, coving because by the time you’ve emptied ¾ of your air the air moves through the small airways which has mucus and bronchoconstriction giving a lower flow rate
Sever Obstructive Disease: As COPD gets worse, everything is exaggerated (vital capacity, coving, total volume increases, peak expiratory flow rate down)
Restrictive: lower volumes and less access to air, peak is lower or the same (NOT SHOWN ABOVE), filling problem not a moving gas problem
VEO: Expiratory curve is fine but inspiratory curve is blunted, still get enough air in but at a slower rate
VIO: Inspiratory curve is fine but expiratory curve is blunted
FAO: Like you’re compressing the tube
How might recovery from serious burns affect lung volumes/capacities?
Most volumes and capacities reduced
Scar tissue formation= less elastic, restricting expansion of the chest at most volumes
How does intrapleural pressure change at the start of tidal inspiration?
Small decrease
At start of tidal, pulls the parietal pleural membrane away from the lung
Increases partial vacuum in the intrapleural space
