Week 1 Compliance, Resistance and WOB VQ missmatch Flashcards
TV
Define
How much is it
how is it calculated
Tidal volume
Volume air inspired and expired with a normal breath
500ml
Tv=Total dead space(VD) + Alveolar volume (VA)
ERV &; RV
Define
Expiratory reserve volume
extra air that can be expired after normal tidal expiration
1200ml
Residual volume
Vol of air remaining after max expiratory effort(ERV)
RV=FRC + ERV or RV=TLC-VC
IRV
Define
How much is it
Inspiratory reserve volume
Extra air that can be inspired after normal tidal inspiration
3000 ml
VC
Vital capacity
Volume of gas that can be expired following maximal inspiration (Deep breath+ deep inhale)
TLC
Define
How is it calculated
Total lung capacity
Gas contained within lungs at end of max inspiration
Total amount air that lungs can hold
RV+ERV+TV+IRV
FRC & IC
Define each
Give calculation for each
(FRC) Functional residual capacity
Volume of gas remaining in lungs at the end of normal exhalation
FRC= Expiratory reserve volume+Residual volume
(IC) Inspiratory capacity
Max volume of gas that can be inspired from resting end-expiratory level (of normal breathing)
IC= Inspiratory reserve volume + Tidal volume
Define VE
How is it calculated
(VE) Expired total ventilation= Tidal volume X frequency
VA
Define
What does it mean
How is it calculated
Alveolar ventilation (Actual vol ventilated per min)
VA = (VT-VD) x f
=(Tidal volume - Total dead space) x frequency
VD
Define
What is it’s significance
Total dead space/Physiologic dead space
volume of gas that does not eliminate co2
composed of:
Anatomical dead space and Alveolar dead space
Anatomical dead space
Define
How big is it?
The volume of the conducting airways (eg trachea ect)
approx 150 ml
Alveolar dead space
Define
Ventilated alveoli which are NOT perfused or relatively underperfused with blood. (t/f no gas exchange)
List 5 basic functions of the lung
Gas exchange Defence against invading microorganisms Resevoir of blood Filtering blood Metabolism
Define partial pressure
The pressure exerted by a gas on the walls of it’s container. Dependant on temp & # molecules
PaO2
Partial pressure of oxygen in arterial blood
PAO2
Partial pressure of oxygen in Alveolar gas
PaCO2
Partial pressure of CO2 in arterial blood
PACO2
Partial pressure of CO2 in Alveolar gas
List 3 main metabolic functions of the lung
Synthesis
Biological activation
Inactivation
Where do the majority of metabolic processes occur in the lungs?
Endothelial cellWs in the lung’s vascular bed
What substances does the lung synthesise?
Phospholipids ( components of pulmonary surfactant)
Proteins (collagen & elastin)formstructural framework
What molecules are activated in the lung?
Polypeptide: Angiotensin I is converted to AngiotensinII by ACE (angiotensin converting enzyme)
AngiotensinII is a BP regulator
What substances are inactivated in the lung?
Bradykinin is inactivated by
ACE(angiotensin converting enzyme)
Prostaglandins from E&;F groups released from damages tissues are also broken down
List 3 forces
Respiratory muscles must overcome for respiration
ELASTIC RECOIL (of the chest wall and lungs)
FRICTIONAL RESISTANCE
(lungs&chest wall + airways to flow of air)
INERTIA (Negligable)
Elastic recoil is one of 3 forces that must be overcome for respiration
Explain elastic recoil of chest wall
Explain elastic recoil of lung
Elastic recoil of chest wall connective tissues:
Diaphagm, Abdomen, Ribcage joints
Elastic recoil of lung:
Surface tension of lungs & elastic fibres of lungs
Pulmonary resistance is usually 2 main types. Give percentages for the prevalence of each
Lung or chest wall tissue or airways to flow or air
Pulmonary resistance is:
20% Pulmonary tissue resistance
80% Airway resistance
As lung volume increases with inspiration what happens to the zone of Apposition?
What is it?
It Decreases.
Insert photo
At very low lung volumes(When you’ve taken a deep breath out) what kind of pressure may the lower rib cage be exposed to?
Intra-abdominal pressure rather than pleural pressure
List the muscles involves in inspiration and expiration
*** edit this with more info
Inspiration:
Parasternal muscles, scalenes- ^ AP diameter
Diaphragm, lower intercostals- ^ Lat expansion
Accessory muscles recruited in heavy breathing
Expiration:
Rectus abdominus,internal and external obliques, transversus abdominus
Define the concept of hysteresis in terms of lung pressure.
The nonlinear pressure-volume curve of the lung in which transpulmonary pressure at a given volume during inflation is LESS than the transpulmonary pressure at the same volume during exhalation.
Define compliance and elastic recoil
Compliance:The ease at which the lung is stretched to expand
Compliance= change in V/ change in Pressure
* insert picture of pressure volume curve
Elastic recoil: Tendency for lung to return to resting volume after distention
INVERSELY PROPORTIONAL
what do the following stand for?
CL & Ccw
CL - lung compliance
Ccw-Chest wall compliance
What does Ppl stand for
What is it’s value?
Intrapleural pressure
Pressure in the thin space b/n the visceral and parietal pleura.
usually more negative at top of lung and less neg at bottom, unless low lung volume or on artificial ventilation
Usually -5 cmH20 at end expiration
(subatmospheric)
What does PA stand for?
small A
Alveolar pressure
Pressure inside the Alveoli
Usually 0cm H2O at end expiration
(same as atmospheric pressure)
What does Ptm (capitals) stand for?
There are 2 types list them
Transmural pressure:The pressure diff across airway or lung wall
> Transpulmonary pressure-diff b/n inside and outside lung
> Transairway pressure- diff pressure b/n airway opening and alveolus. Important to keep airways open
Transpulmonary pressure
How is it calculated?
PA - Ppl Distending pressure
The difference in pressure b/n inside and outside of the lung (always positive)
Transairway pressure
Define
How is it calculated?
PAW - Ppl
transairway pressure is the pressure difference (gradient) between the airway opening and the alveolus. this is the pressure gradient required to produce airflow in the conductive airways, and therefore represents the pressure that must be generated to overcome airway resistance
Explain the pressure changes that occur during inspiration that allow the lungs to fill with air
At End expiration
Pal= atmospheric pressure= 0cm H2O t/f no airflow
Ppl= subatmospheric = -5 cm H2O
Transmural pressure= 0- (-5) = +5
During Inspiration
Ppl= -8 cm H20
Pal= -1 cm H20 = below atmospheric pressure t/f air in
Transmural pressure= -1 - (-8) = +7
List 3 factors responsible for keeping the alveoli open
Surfactant- reduces surface tension
Interdependance
Functional Residual capacity- Resting lung volume
List 5 factors that Affect compliance
Lung volume Surfactant Pulmonary blood flow Age Disease
How does lung volume affect compliance?
The greater the volume the lower the compliance
eg compliance is better at RV than TLC
Compliance is the pressure volume curve. Blowing up a balloon LOW COMPLIANCE at lowest and highest volume.
How does Surfactant affect compliance?
Reduces surface tension
low ST> increased lung compliance (expansion) t/f –reduces muscular effort of breathing
Reduces elastic recoil of lungs at low volume (Preventing collapse)
As alveoli become smaller surfactant molecules are squeezed together lowering the surface tension t/f smaller alveoli are easier to inflate
*Prem babies b4 30 weeks, no surfactant t/f stiff lungs (not compliant)
How does pulmonary blood flow affect Compliance?
Increased capillary blood flow> decreased lung compliance.
Left heart failure can lead to Acute pulmonary Oedema which > decreased lung compliance
How does Age affect compliance
Decreased chest wall compliance(joint ROM)
Increased lung compliance (reduced elasticity)
What diseases lead to Increased lung compliance?
OBSTRUCTIVE LUNG DISEASE- floppy lungs
Emphysema -destroyed elasticity
Floppy airways close early
What diseases lead to decreased lung compliance?
RESTRICTIVE LUNG DISEASE- stiff lungs
FIbrotic lung disease
Collapsed alveoli
Obesity
What diseases lead to decreased chest wall compliance?
Musculoskeletal disorders
Obesity
Effect of increased compliance
Effect of decreased compliance
e.g restrictive lung disease
Increased lung compliance
Less elastic support
Early airway closure
Reduced airway diameter- increased resistance to flow
Decreased lung & CW compliance
Decreased airflow
t/f preferential ventilation of compliance lung units
Define closing capacity
Define closing volume
Closing capacity(CC)= lung volume at which some of the small airways begin to close
Closing volume(CV)= Closing capacity- Residual volume
What does CC and CV stand for?
Closing capacity
Closing volume
List 4 factors that affect airflow resistance
Character of an airway (length& diameter)
Pattern of airflow
Density and viscosity of gas
Lung volume
How does the character of airways affect the airflow resistance?
^ length of tube > ^ resistance
^ length by 1.5 > ^ resistance x 2
Decreased diameter > ^ resistance
decreased radius by 0.5 > ^ resistance x 16
Peak airway resistance occurs in BRONCHUS decreasing as you go down the tract.
low trachea,high bronchus, decreasing as you go on.
Describe the causes of airway narrowing
there are 3 main categories
Within the airway lumen
partial occlusion by secretions or foreign material
e.g. chronic bronchitis
In the lumen wall -hypertrophy of mucous glands -odema of bronchial walls -Contraction of smooth mms (asthma)
Outside the airway -loss radial traction due to destroyed lung parechyma (floppy airways) -lung compression -Peribronchal odema
How does the pattern of airflow affect airflow resistance?
Laminar (terminal bronchioles) min resistance
Turbulent-(eg due to sputum) greatest resistance
Transitional (Nose glottis, carina) great resistance
How does lung volume affect airflow resistance?
Airways more distended(open) at higher lung volumes
Low lung volumes-airway closure will occur which leads to increased resistance
Low V= high resistance High V= low resistance
Think how ppl w COP will hyperinflate on purpose
Explain the difference between static and dynamic hyperinflation
Static hyperinflation:occurs at rest due to floppy airways leading to early airway closure t/f gas trapping.
Also
Increased resistance (from floppy airways)
decreased expiratory flow& ^ expiratorytime (splinting)
Dynamic hyperinflation: Compensatory mechanism to overcome airway resistance.
Normally RR & TV increase during excercise. but coz lungs are hyperinflated only RR can increase.
Patient also spends LESS time in expiration (^ FRC)
to hyperinflate coz ^ Vol decreases airway resistance.
What are the affects of increased airway resistance
Increased resistance
-Decreased airflow
t/f Preferential ventilation of low resistance lung units
-Dynamic hyperinflation
List the main causes of hypoxemia
Ventilation perfusion missmatch **
Hypoventilation
Difusion abnormalities
Shunt
What does V and Q stand for?
What is an ideal VQ relationship
What is a normal VQ relationship
V= ventilation
Q=Perfusion
Ideal V/Q= 1
Normal V/Q= 0.8
What does
Dependent
Non Dependent
mean interms of lungs
Describes the position of the lung in relation gravity
Standing- Upper lobes non dependent
lower lobes dependant
Explain perfusion and ventilation in the dependent lung section
Of a Normal person
DEPENDENT
Preferential perfusion
- high hydrostatic pressure (gravity) capilliaries filled
- alveoli compressed t/f no capillary collapse
Preferential ventilation
- compressed alveoli (low volume) t/f high compliance
- Intrapleural pressure less negative
- t/f low transpulmonary pressure (distending pressure)
- in sidelying abdominal contents fall onto dependent side of diaphragm putting it on stretch t/f stronger contraction
NON DEPENDENT
Well expanded alveoli
low compliance
more neg intraplural P, high transpulmonary P
high recoil pressure
high V t/f compressed capillaries & low perfusion
Breathing at low lung volumes
or being mechanically ventilated
- expand on this if nescessary
POS PRESSURE SYSTEM
Preferential ventilation to Non-Dependent areas
Lungs not well expanded(Low compliance)
Lungs So uninflated that airway closure occurs in dependent areas.
What is it called when there is a HIGH V/Q ratio
What is it called when there is a LOW V/Q ratio
High V/Q ratio- high ventilation, low perfusion
=SHUNT blood entering arterial system without passing through ventilated areas of lung
Low V/Q ratio- low ventilation, high perfusion
=DEAD SPACE
If an individual is hypoxemic with LEFT SIDED pnuemonia which side would you lie them on and why?
Lie them on their good RIGHT side. So that their good right side is in the dependant position and is preferentially ventilated
