Questions and Answers
What should the reservoir bag in a closed circuit CO2 rebreathing response test contain?
What is the alveolar volume (VA) if the patient has a respiratory dead space of 0.3 L (BTPS) and is breathing at a rate of 22 bpm with a tidal volume (VT) of 0.7 L (BTPS)?
8.8L
What is the subject's tidal volume (Vt) if VE is 7.6 L/min and RR is 18 bpm?
0.42L
Which of the following can be measured noninvasively to calculate the Vd/Vt ratio?
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Which measurement confirms the diagnosis of hypoventilation?
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What is P100 in respiratory measurements?
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To calculate respiratory dead space (Vd), which measurements are required?
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How can hyperventilation be defined?
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Which parameter should be measured to assess the adequacy of the output of the respiratory centers?
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Which test requires a variable CO2 scrubbing device in the breathing circuit?
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What color do sodium hydroxide crystals change to when they are fully depleted?
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Calculate the subject's alveolar volume if tidal breathing is measured at 720 ml, with a RR of 12 and a dead space of 150 ml.
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Which statement best describes the measurement P100 or P0.1?
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Which concentrations should the rebreathing bag be filled with before a CO2 response test?
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What formula can be used to estimate dead space?
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Calculate the subject's VE given the following parameters: Temp 25 C, BTPS correction factor: 1.011, Pb: 750, Volume expired: 27L.
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What is the subject's tidal volume (Vt) given the following parameters: Volume expired 27L, RR 12?
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Calculate the subject's Vd/Vt% given: Temp 25 C, Volume expired 27L, FeCO2 33, RR 12, pH 7.38, PCO2 44, PO2 71.
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What is the subject's VA given: Temp 25 C, Volume expired 27L, FeCO2 33, RR 12, pH 7.38, PCO2 44, PO2 71?
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What is the calculated Vd/Vt ratio given the variables: PeCO2 38, RR 15, PaCO2 42, Ve 7.8 L, Temp 19 C, BTPS conversion 1.111?
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Study Notes
Closed Circuit CO2 Rebreathing Test
- Reservoir bag should contain 7% CO2 in O2 for the test setup.
- A variable CO2 scrubbing device is necessary in the breathing circuit for closed-circuit O2 response tests.
Respiratory Measurements
- Patient's respiratory dead space calculated at 0.3 L (BTPS), with a tidal volume (VT) of 0.7 L (BTPS) and a breathing rate of 22 bpm yields an alveolar ventilation (VA) of 8.8 L.
- In a COPD patient, effective tidal volume (VT) can be calculated using minute ventilation (VE) and respiratory rate (RR); example yields a VT of 0.42 L.
- Alveolar volume from tidal breathing of 720 ml and dead space of 150 ml results in an alveolar volume of 7.60 L.
Vd/Vt Ratio Calculation
- Noninvasive measurement of Vd/Vt ratio requires mixed expired PCO2 and PETCO2.
- Vd/Vt ratio estimation can mathematically illustrate the efficiency of ventilation; calculated from the formula VD/VT=(PaCO2-PeCO2)/PaCO2.
Hypoventilation Indicators
- Confirmed hypoventilation with a PAco2 of 48 mm Hg and a pH of 7.29.
Hyperventilation Criteria
- Defined by a PaCO2 less than 35 mm Hg, accompanied by a pH greater than 7.45.
P100 Measurement
- P100 (or P0.1) signifies the pressure developed during the first 100 milliseconds of an occluded breath in response testing.
Use of Sodium Hydroxide Crystals
- Sodium hydroxide crystals (sodasorb) used for CO2 scrubbing change color to violet when fully depleted.
VE and VT Calculations
- Subject's VE (minute ventilation) calculation requires BTPS correction factor; example results in 5.56 L.
- For the subject’s tidal volume (VT), a volume expired of 27L at a rate of 12 breaths per minute computes to 463 ml.
- Vd/Vt % calculated for the same subject is 25%.
- VA measurement for the same conditions results in 4.17 L/min.
Estimating Dead Space
- Dead space can be estimated at approximately 1 ml per pound of ideal body weight for patients.
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Test your knowledge with these flashcards from Ruppel Chapter 4. This quiz covers essential respiratory concepts and calculations related to CO2 rebreathing and dead space measurements. Perfect for students preparing for exams in respiratory physiology.