Respiratory system Flashcards
What are the two zones of the lungs?
1) The Conducting Zone
2) The Respiratory ZOne
What is the conducting zone?
Transport of air only
-Flow slows as air approaches the bronchioles
What is the average total ventilation?
7500ml air per min
-around 15 breaths per minute
What is the equation for alveolar ventilation?
Alveolar ventilation = (Tidal Volume - Volume in Anatomical Dead Space) x Breaths per minute
Alveolar ventilation / Pulmonary blood flow = approx 1
Va = (VCo2 / PACo2) x K
- If alveolar ventilation is maintained while PCo2 increases, PACo2 would have to increase which will increase the amount of Co2 in the blood
- If someone is hyperventilating while resting, the VCo2 would remain the same as no exercise takes place
How to measure ventilation? equation
Ve = Vt n = dVt/dt
Minute ventilation = Tidal Volume x Breathing Frequency
What is the anatomical deadspace?
Conducting airways of the lung but do not exchange gas with the blood supply
How do you measure the concentration of CO2 in expired gas?
VCo2 = Ve x FeCo2
Volume of Carbon Dioxide = Alveolar ventilation x Alveolar Co2 Fraction
What is the atmospheric pressure in atmospheres and mmHg (Torr)?
1 atmosphere
760mmHg or 760Torr
What is the partial pressure of oxygen in the atmosphere?
PO2 in atmosphere = 0.21 (21% in atmosphere) x 760mmHg = 160mmHg
What is the partial pressure of water at body temperature?
47mmHg
So using the PH2O we can work out the amount of dry air and therefore PO2 in the body?
760mmHg - 47mmHg = 713mmHg
713mmHg x 0.21 = 150mmHg
-This is a main reason for the recalibration of the cortex every time it is used
What is dissolved oxygen linearly proportional to?
The partial pressure of oxygen, known as epsilon (wirtten as greek symbol epsilon)
What is the calculation for epsilon?
Epsilon = 0.0031ml O2 / (100ml blood x mmHg)
This means that at 100mmHg, 0.31ml of Oxygen per 100ml blood is carried by the plasma
PLASMA, not total blood because you have haemoglobin carrying capabilities to add
What are the 2 types of Haemoglobin?
Haemoglobin A - accounts for 97% of Hb in adults
Haemoglobin F - dominant form of Hb in fetus and less than 6 month after birth (this Hb has a much higher affinity of oxygen)
What is the purpose of the severinghaus equation?
Calculates how much oxygen binds at certain pressures
What is the severinghaus equation?
CaO2 = (phi x So2) + (epsilon Po2)
Carrying capacity of Oxygen = (phi x carrying capacity of Hb) + (epsilon x partial pressure of O2)
Phi = oxygen carrying capacity of Hb
What happens when you give a patient total oxygen?
The plasma carrying capacity of oxygen will increase far greater than the carrying capacity of oxygen
What are the factors affecting Oxygen Dissociation Curve?
- pH through increased H+ ion concentration (acidic)
- Temperature
- PCo2 increase
- DPG increase
During exercise, muscle will have a higher lactic acid present, increased CO2 and it will get hot so will all affect the Oxygen Diss Curve, would shift left to increase oxygen in muscles to help meet demand
How is carbon dioxide transported?
- Dissolved CO2 in plasma
- Bicarbonate (forms carbonic acid)
- Carbaminohaemoglobin compound
What are the characteristics of the CO2 Dissociation Curve?
- Similar to ODC but much more linear
- Shift to the right governed by oxygen saturation of Hb
- greater CO2 carrying capacity at lower oxygen saturation
- Different effects in lungs and tissues
How does ventilation change through exercise?
At low intensity, there are increases in tidal volume
At high intensity respiration rate also increase
What are the average
max ventilation rates in small and large adults?
Small Adult: 100L/min
Large Adult : 200L/min
What is the equation for volume of CO2 expired?
VCo2 = Ve x FeCo2
Volume of Carbon Dioxide = Volume expired x Fraction expired that is CO2
What are the values of Oxygen consumption at rest, exercising or elite athlete?
rest - 300ml/min
exercising - 3000ml/min
elite athlete - 6000ml/min
What happens to VO2 during exercise?
- Increase in Vo2 increases linearly with work rate
- point where the Vo2 plateaus is Vo2MAX
- any additional metabolic demand above Vo2MAx must be satisfied with anaerobic metabolism
What is the relationship between Vo2 and ventilation?
- Increases linearly with Vo2/Work rate
- Increases more rapidly at higher Vo2
- Caused by increase in lactic acid where H+ ions stimulate breathing
What is the relationship between Vo2 and cardiac output?
- increases linearly with Vo2/work rate
- Only about a quarter of the increase in volume expired
What is an equation for Vo2 and cardiac output?
Vo2 = Q. (CaO2 - CvO2)
Volume of oxygen = cardiac output x A-V diff
- So to increase Vo2, you can increase either Cardiac Output or A-V Diff
- Means not only cardiac output is responsible for Vo2
What is an equation for Vo2 and ventilation?
Vo2 = V.e (FiO2 - FeO2)
Volume of Oxygen = Minute ventilation x (inspired-expired difference)
- Increasing ventilation is the only way to increase Vo2
- Inspired-expired differences won’t change unless your are breathing from an oxygen tank
What are limitations for performance athletes?
- Cardiovascular system outstrips pulmonary system, caused by an increasing gap between alveolar and arterial Po2
- Alveolar Po2 continues to increase with work load but arterial PO2 declines
- Arterial blood oxygen saturation decreases as VO2MAX approached, going from between 97-99% saturation to 95% saturation
What are the causes of arterial desaturation?
1) Ventilation perfusion rate is no longer 1
2) Arterial venous shunting - blood bypassing the alveoli
3) Incomplete equilibrium between alveolar gas and capillary blood
