The following are the most common respiratory therapy formulas and normal values used by respiratory therapists.
1. Ideal Body Weight (IBW):
2. Static Compliance: (VT/Static pressure – PEEP)
3. Desired FiO2 = Desired PaO2 + Known FiO2 divided by known PaO2
(Normal PaO2 on 21% or room air = 105)
4. Desired Ve= Known Ve*Known PaCO2 divided by desired PaCO2
5. Desired Vt = (Known PaCO2 x Known Vt)/Desired PaCO2
6. Desired f = (Known PaCO2 x Known f)/Desired PaCO2
7. RAW: PIP–Plateau/ Flow, or PIP–plateau
8. French size sx catheter = ETT size * 3/2
9. PAO2: (713 *Fio2 – PaCO2)/0.8or 0.1 if 100% O2
10. A-a gradient (ratio or A-ADO2): PAO2 – PaO2
11. To determine cause of hypoxia, refer to the A-a gradient:
12. Shunt % = A-a gradient/20
13. a-A ratio: PaO2/PAO2
14. P/F Ratio: PaO2/FiO2
15. Expected PaO2 = FiO2 x5
Even though normal PaO2 is 105 on room air, a PaO2 of 200 on 100% FiO2 is not necessarily good. It should be 500. Therefore you know patient still not oxygenating effectively.
16. e-cylinder time remaining=0.30(PSI) / LPM
17. Oral intubation = 21-25cm @ lip.
18. Nasal intubation = 26-29cm
19. PEEP therapy = greater than 6-8 CWP
20. Humidity should be set at 37 degrees Celcius.
22. Patient WOB (available on newer microprocessor ventilators)
23. Actual PaO2/ Expected PaO2 = % of patient expected PaO2:
Examples of % expected PaO2: (Despite lower PaO2, patient still oxygenating better)
Another example of % expected PaO2 (PaO2 looks good, but is patient really oxygenating?)
24. Temperature Conversion:
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