Breathing Circuits Flashcards
2 types of Dead space
Anatomic
Physiological
Tidal volume (Vt) - in the adult male.
volume of air inspired or expired with each normal breath -
Normal TV in adult male
about 500 cc
Inspiratory Reserve Volume–>
volume of air that can be inspired over and above the normal VT when the person inspires with full force
Normal IRV
about 3000 cc.
Expiratory reserve volume (ERV) -
maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration
Normal ERV
about 1100 cc.
Residual Volume (RV) -
volume of air remaining in the lungs after the most forceful expiration
Normal RV is
about 1200 cc.
What is a capacity?
It is a combination of 2 or more volumes
Inspiratory capacity =
VT + IRV = amount of air a person can breathe in. beginning at the normal expiratory level and distending the lungs to the maximum amount.
Normal Inspiratory Capacity
about 3500 mL
FRC (functional residual capacity) =
ERV + RV. The amount of air that remains in the lungs at the end of normal expiration
Normal FRC
About 2300 mL
VC vital capacity equals the ______
inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume.
Vital Capacity is the
maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent
What is a normal capacity ?
about 4600 mL
TLC total lung capacity =
VC + RV
TLC definition
The maximum volume to which the lungs can be expanded with the greatest possible effort (about 5800 cc); it is equal
Normal TLC
5800 ml
Formula for VE (minute ventilation)
TV x RR
IRV + VT + ERV =
VC
VC + RV =
TLC
ERV + RV =
FRC
IC + ERV =
VC
IC + FRC
TLC
PaO2
Partial pressure of Oxygen in arterial blood
PAO2
Partial pressure of Oxygen in ALVEOLAR GAS
PACO2
Partial pressure of CO2 in ALVEOLAR GAS
PAH2O
Partial pressure of H2O in ALVEOLAR GAS
Closed Circuit system
Reservoir
Rebreathing
Examples
Yes
Yes
Circuit with APL valve closed
Open Circuit system
Reservoir
Rebreathing
Examples
No
No
Open drop
SEMI- Open Circuit system
Reservoir
Rebreathing
Examples
Yes
No (APL valve open)
Non-rebreathing circuit OR Circle at HIGH FGF (>Ve)
SEMI- CLOSED Circuit system
Reservoir
Rebreathing
Examples
Yes
Yes PARTIAL (APL partial open)
CIRCLE AT LOW FGF (
NonRebreathing systems Characteristics
Highly dependent on fresh gas flow
No unidirectional valves
No CO2 absorber
Little resistance to breathing
Gas flows for Bain/ Mapleson D
FGF 2-3 * VE or 5 l/m, whichever is greater
Advantages of the circle systems
- .constant inspired concentrations
- conserve respiratory heat and humidity
- useful for all ages (may use down to 10 kg, about one year of age, or less with a pediatric disposable circuit)
- useful for closed system or low-flow
- low resistance (less than tracheal tube, but more than a NRB circuit)
Circle disadvantage
- increased dead space
2. malfunctions of unidirectional valves
Circuit still being used in
Mapleson
Preoxygenation patients
DE-NITROGEN
Residual VOLUME –>
Severe SCOLIOSIS
Low Inspiratory Reserve volume
NO INSPIRATORY RESERVE , Partially inflated lung on one side, low volume
FRC fast desaturation
