Alv. Gas
A patient is breathing 60% oxygen, barometric pressure is 760 mmHg, and PaCO₂ is 40 mmHg.
What is PAO₂ = (0.60)(760-47) – 40 = 408.8 mmHg
A patient has a heart rate of 80 bpm and a stroke volume of 70 mL. What is their cardiac output?
What is CO = 80 × 70 = 5600 mL/min or 5.6 L/min
A ventilated patient has Vt = 500 mL, PIP = 35 cmH₂O, and PEEP = 5 cmH₂O. What is the dynamic compliance?
What is Cdyn = 500 / (35 – 5) = 16.7 mL/cm H₂O
A patient’s PaO₂ is 75 mmHg and calculated PAO₂ is 100 mmHg. What is the PaO₂/PAO₂ ratio?
What is 75 / 100 = 0.75
How long will an E-cylinder with 2000 psi last at 2 L/min?
What is (0.28 × 2000) / 2 = 280 minutes or 4.67 hours
A patient on room air (FiO₂ = 0.21) has a PaCO₂ of 50 mmHg. What is the approximate PAO₂ using the full alveolar gas equation? (PB = 760 mmHg)
What is PAO₂ = (760–47)(0.21) – (50 × 1.25) = 82.7 mmHg
If a patient has a systolic pressure of 120 mmHg and a diastolic pressure of 70 mmHg, what is their MAP?
What is MAP = (120 + 2(70)) / 3 = 86.7 mmHg
If PIP = 30 cmH₂O, plateau pressure = 25 cmH₂O, and flow = 60 L/min, what is airway resistance?
What is Raw = (30 – 25) / (60 ÷ 60) = 5 cm H₂O/L/sec
A patient has a Vt of 500 mL, Vd of 150 mL, and RR = 12. What is their alveolar minute ventilation (MVA)?
What is (500 – 150) × 12 = 4200 mL/min or 4.2 L/min
A patient is receiving 40% oxygen with an air-entrainment mask and 10 L/min set on the device. What is the total flow delivered?
What is 42 L/min
A patient is on 100% oxygen, PB = 760 mmHg, PaCO₂ = 45 mmHg. What is PAO₂?
PAO₂ = (1.0)(760-47) – 45 = 668 mmHg
A patient has a HR of 90 bpm and SV of 55 mL. What is their cardiac output?
CO = 90 × 55 = 4950 mL/min or 4.95 L/min
Vt = 600 mL, Pplat = 30 cmH₂O, PEEP = 10 cmH₂O. What is static compliance?
Cstat = 600 / (30 – 10) = 30 mL/cm H₂O
A female patient is 5’6”. What is her IBW?
IBW = 45.5 + 2(6) = 57.5 kg
An E-cylinder has 1200 psi remaining, and the flow is set at 3 L/min. How long will it last?
0.28 × 1200) / 3 = 336 / 3 = 112 minutes
PAO₂ = (PB - 47)(FiO₂) – (PaCO₂ × 1.25). What is PAO₂ if FiO₂ = 0.40, PB = 750, and PaCO₂ = 55 mmHg?
PAO₂ = (750 – 47)(0.40) – (55 × 1.25) = 281.2 – 68.75 = 212.45 mmHg
A patient has BP = 88/58 mmHg. What is the MAP?
MAP = (88 + 2(58)) / 3 = (88 + 116) / 3 = 68 mmHg
Vt = 450 mL, PIP = 28, PEEP = 8. What is dynamic compliance?
Answer: Cdyn = 450 / (28 – 8) = 22.5 mL/cm H₂O
A male patient is 5’8”, weighs 170 lbs. What is his anatomic deadspace?
Anatomic deadspace ≈ 1 mL/lb IBW = 145 mL
An H-cylinder is at 2200 psi, flow set at 4 L/min. What is duration of flow?
3.14 × 2200) / 4 = 6908 / 4 = 1727 minutes or ~28.8 hours
If a patient on 60% oxygen has PaCO₂ = 60 mmHg and PB = 730 mmHg, what is PAO₂ using the simplified equation?
PAO₂ = 0.60(730 – 47) – 60 = 409.8 – 60 = 349.8 mmHg
If a patient has a MAP of 55 mmHg, what does this indicate about their organ perfusion?
What is "Organ perfusion is compromised; below acceptable threshold of 65 mmHg"
If PIP = 36, plateau = 28, and flow = 40 L/min, what is airway resistance (Raw)?
Raw = (36 – 28) / (40 / 60) = 8 / 0.667 = 12 cm H₂O/L/sec
A patient has Vt = 600 mL, Vd = 160 mL, and RR = 16. What is alveolar minute ventilation?
MVA = (600 – 160) × 16 = 440 × 16 = 7040 mL or 7.04 L/min
E-cylinder has 1000 psi, running at 5 L/min. How many hours will it last?
(0.28 × 1000) / 5 = 280 / 5 = 56 min = 0.93 hours