Phys- Ventilation/Lung Volumes Flashcards
5 steps of respiration
- Ventilation
- Diffusion of O2 and CO2 between alveoli and pulmonary capillaries
- Transport of O2 and CO2 through pulmonary and systemic circulations via bulk flow (high to low pressure)
- Diffusion of O2 and CO2 between blood and tissue
- Cell utilization of O2 and production of CO2
Tidal volume:
Definition and normal value
Volume of air inhaled and exhaled in one breath
500 ml
Equation Vt
Vt = volume in alveoli + volume in airways
IRV:
Definition and normal value
Max volume that can be inspired in addition to tidal volume
3 L
ERV:
Definition and normal value
Max volume that can expired in addition to tidal vol
1.2 L
Residual volume
Definition and normal value
Volume in lungs after max expiration
1.2 L
FRC:
Definition and normal value
What’s left in lungs after NORMAL Vt; “equilibrium volume”
2.5 L
FRC equation
ERV + RV
1.2L + 1.2L = 2.4L
VC:
Definition and normal value
Volume expired after max inspiration
4.7 L
VC equation
IC + ERV
Vt + IRV + ERV
IC:
Definition and normal value
The maximal volume that can be inspired
3.5L
IC equation
Vt + IRV
0.5+3 = 3.5L
TLC:
Definition and normal value
All air in lungs
6 L
TLC equation
VC + RV
Vt + IRV + ERV + RV = 0.5 + 3 + 1.2 + 1.2 = 6L
FVC:
Definition and normal value
Volume of air forcibly exhaled after max inspiration
5 L
FVC equation
Vt + ERV + IRV
0.5 + 1.2 + 3 = 4.7 L
FEV1:
Definition and normal value
Volume of air forcibly expired in 1 sec
80% of FRC (2.5L), so 2L
Three lung volumes/capacities NOT measured by spirometry
RV, FRC, TLC
(RV is the air left after max expiration, so it can’t be measured. Since RV is a component of TLC and FRC, they can’t be measured either)
2 methods to measure RV, TLC, and FRC
He dilution and body plethysmography
FEV1/FRC > 80%
Restrictive lung disease (can’t get air in so FRC decreases»_space; FEV1)
FEV1/FRC < 80%
Obstructive lung disease (can’t get air out, so FEV1 decreases»_space; FRC)
What is anatomic dead space? Normal volume?
Conducting airways where no gas exchange occurs due to lack of alveoli; 150 ml
What are the conducting airways?
Trachea to terminal bronchioles
What is alveolar dead space?
Alveoli that are ventilated but not perfused
Increased alveolar dead space is always:
Pathologic
What is physiologic dead space?
Sum of volume of anatomic and alveolar dead space
How to estimate anatomic dead space
Lean weight in pounds
When should you measure alveolar air?
End expiration; the air at the beginning of exhalation contains air from anatomic dead space which will have same composition as atmospheric air
Minute ventilation equation
Vm = Vt * RR
Normal Vm
Vm = 500 * 15 = 7500 ml/min
Exercise Vm
Vm = 2000 * 20 = 40000 ml/min
Vm at exercise:Vm at rest
40,000:7500 = 5.3 fold increase in Vm during exercise
VA equation
VA = (Vt - Vds) * RR
Normal VA
VA = (500 - 150) *15 = 5250 ml/min
VA during exercise
VA = (2000 - 150) * 15 = 37,000 ml/min
VA during exercise:VA at rest
37,000:5250 = 7 fold increase in VA during exercise
Why does alveolar ventilation increase more during exercise than does minute ventilation?
Dead space decrease as a % of minute volume
Which is more important for increasing alveolar ventilation: breathing rate or depth?
Depth (increase amount of air reaching alveoli)
Normal pulmonary capillary blood volume
70 ml
Px =
Px = Total pressure of mixture * % gas x in mixture
Dalton’s Law
Pressure =
F/A
Normal atmospheric pressure
760 mmHg
PAO2=
ALVEOLAR GAS EQUATION!!
PAO2 = PIO2 - PACO2/R
R =
Respiratory quotient
CO2 produced/O2 consumed
Normal R value? What does this mean?
0.8
Changes in alveolar ventilation will affect O2 consumption more than CO2 production
What happens to PAO2 when R decreases to 0.6?
Decreases
R decreased means O2 consumption increases and PACO2/R increases = decreased PAO2
Pleural pressure of -4 = ___ mmHg
756
Boyle’s Law
P1V1 = P2V2
pressure and volume are inversely related
What determines air flow into or out of lungs?
Transrespiratory pressure
Ptr =
Ptr = Palv - Patm
What determines the inflation of the lungs?
Transpulmonary pressure
Ptp =
Ptp = Palv - Pip
___ pressure is always negative because:
Intrapleural; the chest wall wants to spring out while the lungs want to collapse, creating a negative pressure
How do you measure intrapleural pressure?
Estimated using esophageal pressure
When is transrespiratory pressure 0?
After a forced expiration/when breathing has stopped
At the end of a forced expiration, intrapleural pressure is -4. What balances this?
Elastic recoil of lung