Ventilation (from resources) Flashcards
Define the following terms:
PaO2
PAO2
PA/Palv
Pao
Vd
Vt
PaO2: arterial partial pressure of O2
PAO2: alveolar partial pressure of O2
PA/Palv: alveolar pressure
Pao: pressure at mouth opening
Vd: dead space
Vt: tidal volume
Define the following terms:
PaCO2
PACO2
CaO2
DO2
PAP
PaCO2: arterial partial pressure of CO2
PACO2: alveolar partial pressure of CO2
CaO2: content of oxygen in arterial blood
DO2: oxygen delivery
PAP: pulmonary artery pressure
Define diffusion and state by which law it’s dictated.
The process of a liquid or gas moving from an area of higher concentration to an area of lower concentration to create equilibrium. Graham’s law.
How many mL of Vt should be given for every mL of dead space
3mL. 3:1 ratio of Vt:Vd is important so we don’t just move dead space air back and forth.
What is PIP and where is it measured
Peak Inspiratory Pressure is a combination of PEEP, airway resistance (coughing, asynchrony, ETT size) and target pressure setting
It is measured at the flow sensor (pressure at the mouth) during inspiration
What is Pplat an indication of and where is it measured
Plateau pressure is an indication of lung compliance, where if it is high then pt’s lung compliance is an issue
It is measured at the end of an inspiration (with hold) and should be < 30cmH2O
What is Driving Pressure (ΔP on Hamilton)
The difference between Pplat and PEEP and should be < 15 cmH2O
It’s the pressure required to keep alveoli open
List controls for ventilation
Vt
Pressure control
Pressure support
I:E ratio
List controls for Oxygenation
Oxygen (FiO2)
PEEP
A shift in the oxygen-hemoglobin dissociation curve to the _____ will = an increase in hemoglobin’s affinity for oxygen, a shift to the ____ will decrease affinity and release oxygen to the tissues more readily.
Left, Right
What is the V/Q ratio in the 3 different zones of the upright lung?
a) Upright zone 1 (apex)
b) Upright zone 2 (mid)
c) Upright zone 3 (base)
a) V>Q (more alveoli, narrower blood vessels)
b) V/Q 1:1 (blood vessels & alveoli at maximal size)
c) V
Describe tidal volume (Vt) and state it’s average value
Volume of air entering or leaving lungs during a single breath, ~300-500mL (6-8 mL/Kg)
Describe inspiratory reserve volume (IRV) and state it’s average value
Extra volume of air that can be maximally inspired over and above the typical tidal volume, ~1900-3300mL
Describe inspiratory capacity (IC) and state it’s average value
Maximum volume of air that can be inspired at the end of a normal expiration, ~2400-3800mL (IC = IRV + Vt)
Describe expiratory reserve volume (ERV) and state it’s average value
Extra volume of air that can be actively expired by maximal contraction beyond normal volume of air after a resting tidal volume, ~700-1200mL
Describe residual volume (RV) and state it’s measurement
Volume of air remaining in the lungs after maximal expiration, indirectly measured by FRC-ERV
Describe total lung capacity (TLC) and state it’s average value
The sum of all volumes, it’s the maximum volume of air the lungs can accommodate after maximum inspiration (Vt+IRV+ERV+RV), ~4-6L
Describe vital capacity (VC) and state it’s average value
The total amount of air exhaled after maximal inhalation (VC=Vt+IRV+ERV), ~4800mL. VC should be ~3x greater than Vt for effective cough.
Describe functional residual capacity (FRC) and state it’s average value
The amount of air remaining int he lungs at the end of a normal exhalation (FRC = RV + ERV), ~1800-2200mL. In COPD FRC is increased, can be up to 80% of TLC
What is the difference between intrapulmonary and extrapulmonary shunts?
Intrapulmonary is usually alveoli filled with pus or fluids unable to participate in gas exchange, while extrapulmonary shunts (aka right-to-left shunt) bypasses lungs due to a cardiac defect (eg. ventricular septal) or a fistula
What are the three types of dead space?
Anatomical: conducting airways, ~150mL in adults
Mechanical: anything added to the vent circuit (extender, ETCO2 adapter, HME, suction, etc.)
Physiologic: functional alveoli that are inadequately perfused
What is the normal percentage of dead space (Vd) to tidal volume (Vt)?
30%. The % increases as Vt decreases, that’s why we can’t ventilate at <4mL/Kg - we would then only be moving dead space air back and forth
What are the two factors determining lung compliance?
- Stretchability of the lung’s elastic fibres
- Surface tension within alveoli (no surfactant = high surface tension = collapse, collapsed alveoli resist expansion resulting in low compliance)
Describe the 3 sections of the lung pressure-volume curve.
- The lower portion indicates the increased pressure required to open the alveoli (recruitment), big pressure = small changes in volume
- Middle portion = optimal compliance (alveoli are open, small changes in pressure = big changes in vol)
- Upper portion = low compliance due to overstretch, wasted pressure as it doesn’t change volume
