Unit 1 Flashcards
TPP
Transpulmonary pressure= alveolar pressure - intrapleural pressure
Alveolar pressure: negative on inspiration, positive on expiration
Intrapleural pressure: always positive
Vital capacity needed for effective cough
15 ml/kg
Dead space mL
2 mLkg
150 mL in 70 kg patient
Minute ventilation
Abbreviated by VE
TV x RR
Alveolar ventilation
Abbreviated by VA
(TV-dead space) x RR
Relationship between alveolar ventilation and CO2 production and PaCO2
Proportional to CO2 production
Inverse to PaCO2
Bohr equation
Vd/Vt=(PaCO2-PeCO2)/PaCO2
PeCO2-partial pressure of CO2 in exhaled gas, not the same as ETCO2
Vd/Vt
Fraction of tidal volume contributing to dead space
ML/kg of dead space in spontaneous ventilation
2 mL/kg
Vd/Vt in spontaneous ventilation
150mL/450mL=0.3
Mechanical ventilation Vd/Vt
0.5
Mechanical ventilation increases ventilation to perfusion
Normal V/Q ratio
Ventilation =4 L/min
Perfusion= 5 L/min
V/Q=0.8
V/Q at apex and base of lun
Increased at apex
Decreased at base
Compliance
Change in volume/change in pressure
0 V/Q ratio
Shunt
No ventilation
Infinity V/Q
Dead space
No perfusion
Cylinder Law of Laplace
Tension= pressure x radius
Ex: blood vessels
Spherical Law of Laplace
Tension= (pressure x radius)/2
Ex: alveoli, heart ventricles
Surfactant production begins and matures
Begins: 22-26 weeks
Mature: 35-36 weeks
Zone 1
PA > Pa> Pv
Dead space
Not in a normal lung
Bronchioles constrict to decrease the dead space
Zone 2
Pa>PA>Pv
Waterfall
Blood flow proportional to Pa-PA
Zone 3
Pa>Pv>PA
Shunt
Better perfused than ventilated
Hypoxic pulmonary vasoconstriction to decrease shunt
Zone 4
Pa>Pinterstitial>Pv>PA
Pulmonary edema
Alveolar oxygen
FiO2 x (Pb-PH2O)- (PaCO2/RQ)
Pb=barometric pressure
PH2O= humidity of inhaled gas (assumed 47 mmHg)
RQ= respiratory quotient (0.8)
Respiratory quotient
Carbon dioxide production/oxygen consumption
200mL/min / 250mL/min
Assumed 0.8
RQ changes
RQ >1= lipogenesis (overfeeding)
RQ 0.7+ lipolysis (starvation)
A-a gradient
PAO2-PaO2
On RAis 15mmHg
IRV
3000 mL
VT
500 mL
6-8 mL/kg
ERV
1100 mL
RV
1200 mL
CV
Variable
TLC
5800 mL
IRV + TV + ERV + RV
VC
4500 mL
60-70 mL/kg
IRV + TV + ERV
IC
3500 mL
IRV + TV
FRC
2300 mL
35 mL/kg
RV + ERV
CC
Variable
RV + CV
Functional residual capacity
35 mL/kg
Decreased leads to increased zone 3
Closing capacity with aging
Cc equals FRC under GA @ 30
Supine @ 44
Standing @ 66
Closing capacity
Closing volume + residual volume
Closing volume
Volume above RV where small airways close during expiration
Happens when pleural pressure > airway pressure
O2 carrying capacity
CaO2= (1.34 x Hbg x SaO2) + (PaO2 + 0.003)
How much O2 is dissolved in blood
O2 delivery
DO2= CaO2 x CO x 10
How fast O2 is delivered to the tissues
O2 consumption
VO2= CO x (CaO2-CvO2)
Approximately 3.5 mL/kg/min, 250 mL/min
Normal Hgb and Hct
Male: 15g/dL and 45%
Female: 13g/dL and 39%
P50 left shift
Increased infinity (Left=love)
Decreased temp Decreased 2 3 DPG Decreased CO2 Decreased H+ Increased pH Hgbmet HgbCO HgbF
P50 right shift
Decreased affinity (R=release)
Increased temp Increased 23 DPG Increased CO2 Increased H+ Decreased pH
Where P50 occurs normally
26.5 mmHg partial pressure of oxygen
PaCO2 changes on pH of blood
Acute respiratory acidosis- PaCO2 increases 10 mm Hg and pH decreases 0.08
Chronic respiratory acidosis- PaCO2 increases 10 mmHg and pH decreases 0.03 (renal HCO3- retention)
Transport of CO2 in blood
70% bicarbonate
23% bound to hemoglobin
7% dissolved in plasma
CO2 solubility coefficient
0.067 mL/dL/mmHg
Haldane effect
Describes CO2 carrying
Opposite of Bohr effect
O2 causes RBC to release CO2
R shift=oxygenated hemoglobin
Occurs in lungs
L shift= deoxygenated hemoglobin
Occurs in capillaries
Level for CO2 narcosis
PaCO2 > 90mmHg