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a/A ratio
PaO2/PAO2 norm is 90%, >35%weaning, reflects efficiency of oxygenation as a percentage, <74%shunt, V/Q mismatch or diffusion defect
A-aDo2
A-a gradient, norm 5-10 mmHg on .21, 30-60 on 100%, >350mech support, <350 weaning. Represents potential to Oxygenate vs. the amount of O2 in the artery. Every 50mmHg is approx. 2 percent shunt above norm of 2-5%
Alveolar Air Equation
(pb-47)FIO2-(PaCO2x1.25), norm 80-100mmHg (can reach 675 on 100%), press of O2 in the Alveoli at any given Pb, represents potential for arterial oxygen
BP
norm 120/80 (90-140/60-90), <90/60 or >180/110 is inconsistent with weaning
CaO2
norm 16-20 vol% (Hbx1.34)SaO2 + (PaO2x.003) total amount of O2 carried in 100ml of blood, combined content of O2 carried on Hb and dissolved in plasma, (can be reduced by
CcO2
Content of pulm capillary blood oxygen at 100% FIO2, (Hbx1.34)1 + (PAO2x.003) used in shunt equation
CD
dynamic compliance, aka CLdyn, norm is 0.03-0.04L/cmH2O (30-40mL/cmH20), calc is Vt(L)/(PIP-PEEP) Changes in CD indicate changes in CL or elastance. Up with decreased elasticity (emphysema, down with with stiff (ARDS).
CI
cardiac index, 2.5-4 L/min, <2.1 inconsistent with weaning
Cs (CVAE)
static compliance, norm for vent pt is .035-.055L/cmH20 or 35-55mL/cmH20, calc is Vt/(Pplat-PEEP), represents the combination of lung elasticity and chest wall recoil while on vent. Down with stiff lungs, >35ml/cnH2O weaning
*Ct
Tube compliance aka compressible volume, volume lost to pt circuit, approx 3ml/cmH20 x PIP, deduct from VT to find actual delivered tidal volume. VT-(PIP x 3) equals actual VT.
CvO2
(Hb x 1.34)SvO2 + (PvO2 x .003) norm is 15 vol%, represents the value of O2 in blood returning to the right side of the heart after tissues have oxygenated.
CVP
central venous pressure, norm 2-6 mmHg, 2-6 weaning
Deadspace
ventilation in excess of perfusion (pulm emboli)
DO2
O2 Delivery, (CaO2 x CO) x 10, norm is 1000mL/O2/min
FIO2 for weaning
<40-50% weaning
Flow
(VT/IT) x 60 or VE x (I+E)
Flow required for a 1 second I-time and a VT of 750cc?
.750 equals L/sec x 1 or .750L/sec flow. To convert to L/min .750 x 60 equals 45L/m, this is the vent flow setting to deliver a VT in 1 second I-time.
Hb
12-16 g/100ml of blood, (no anemia or >10g for weaning)
HCO3
22-26 torr
HCT
40-50%
HR
norm 60-80, 60-120 weaning
I:E ratios/%
1:233%, 1:325%, 1:420% (add the ratio parts, then figure what percent is the sum of the parts, 1+4 is 5 and 1/5 of 100% is 20%)
IBW F
105+5/lb over 60\"
IBW M
106+6/lb over 60\"
I-time
represents relationship for volume (Liters), flow (L/sec) and time (seconds). V eq F x T or F eq V/T
Low press on vent
look for leak, cuff or humidifier will be first place
Magic Box
TIIVR+TIVER, FRC, TIIVR TLC, IRV, IC, VC, RV, + TIVER, FRC TLC, IRV, VT, ERV, RV, FRC
MAP
Mean arterial pressure, norm 90 (80-100), 70-130 weaning
MIP/NIF
Max Inspiratory Press, norm -80 - -100, > -20 support indicated, < -20 weaning (remember that negative numbers are larger as they become less, -25 < -20)
PaCO2
35-45 torr, > 55 indicates support, < 50 weaning
PaCO2 to increase with pt on mech vent
< PIP, < RR, > PEEP
PaCO2(d)
CO2 desired, CO2 is adjusted by changing Resp rate so (VExCO2)/CO2dVEd or (RRset x CO2)/CO2dRRd, always round down and go slightly acidic as tissue will oxygenate better.
PaCO2-to decrease with pt on mech vent
>PIP, >RR,
PaO2
80-100 torr, > 60 mmHg on < 60% weaning
PaO2 <80 on FIO2 <60
V/Q mismatch
PaO2 <80 on FIO2 >60
shunt, refractory hypoxemia or venous admixture
PaO2 desired
PaO2 (desired) x FIO2 (current)/PaO2 (current)FIO2 required to bring PaO2 to desired level. Example of pt on 40% FIO2, PaO2 of 53 and wanting PaO2 of 80, calc is (80x.4)/53 equals .60, so increase FIO2 to 60%
PaO2/FIO2
PaO2/FIO2, norm 350-450mmHg, <300 indicates acute lung injury, <200 indicates ARDS, >200weaning, measures o2 efficiency
PaO2-to decrease while pt on mech vent
PaO2-to increase while pt on mech vent
>PIP, >RR, >PEEP, or >FIO2
PAP
pulmonary artery pressure, norm 25/10 (20-35/5-15), >35/15 is inconsistent with weaning, pulm hypertension, left vent fail, fluid overload
PCWP
pulmonary artery wedge pressure, norm 5-10 mmHg, >18 is inconsistent with weaning, left vent failure, fluid overload
PEEP
positive end expiratory pressure above baseline of 0, norm 3-5 (5-8/ARDS)
PH
Norm 7.35-7.45, <7.20 indicates support, >7.35 weaning
PIP
Peak pressure, norm is <50cmH2O, the press required to overcome both compliance and resistance
PvO2
40 torr
QS/QT
Pulmonary Shunt equation (CcO2-CaO2)/(CcO2-CvO2) Norm 2-3%, >20% vent indication, <20% weaning, >30% is life threatening. Measures % of QT not exposed to ventilation, shunts caused by atelectasis, edema, pneumonia, pneumothorax, obstructions
QT
cardiac output, norm 5L/min (4-8)
RAW (RIAF)
Airway Resistance norm is 5-12cmH2O/L/Sec for intubated pt, (PIP-Pplat)/(flow in min/60 sec). Increase in RAW reflects an issue with airways, bronchospasm, secretions, edema etc.
Refractory hypoxemia
hypoxemia that does not respond to O2 therapy
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