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resources:checklists:ventilator_rounding [2023/08/06 01:07] – created adminresources:checklists:ventilator_rounding [2023/12/22 19:14] (current) – [Foundational Equations] admin
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 +[[https://anesthesia.ucsf.edu/sites/anesthesia.ucsf.edu/files/wysiwyg/Ventilator_Pocket_Guide_2020.pdf | Ventilator Pocket Guide]]
 +
 ==== Foundational Equations ==== ==== Foundational Equations ====
 +
 +^ Ohm's Law                         | $\Delta P = FR = P_{aw} - P_{alv} = P_{pl} - PEEP_{total}$                                               |
 +^ Equation of Motion                | $P_{aw} =  FR + \frac{V_{t}}{C} + PEEP_{total}$                                                          |
 +^ Compliance                        | $C = \frac{\Delta V}{\Delta P}$                                                                          |
 +^ Natural Decay Equation            | $V_i(t)= \frac{V_o}{e^{\frac{t}{RC}}} = \frac{V_o}{e^{\frac{t}{\tau}}}$                                  |
 +^ Calculating $\Tau$, General Case  | $ \tau = \frac{V_t}{F} \Bigg(\frac{PIP - P_{plt}}{P_{plt} - PEEP_{total}}\Bigg) $                        |
 +^ Alveolar Gas Equation             | $P_AO_2 = F_iO_2(P_{atm}-P_{H_2O}) - \frac{P_aCO_2}{RQ} $, where $RQ = 0.80$ |
 +
 +  * [[https://xlung.net/en/mv-manual/basic-modes-of-mechanical-ventilation | Vent Waveforms]]
 +==== Alveolar Gas Equation====
 +$P_AO_2 = F_iO_2(P_{atm}-P_{H_2O}) - \frac{P_aCO_2}{RQ}$
 +
 +substituting back in to $RQ$ equation:
 +$RQ = \frac{P_ACO_2}{\frac{V_AP_ACO_2}{kVO_2}}= \frac{VO_2}{V_a}k$
 +
 +$V_T = V_A + V_D$, where $V_A = 350$ and $V_D = 150$
 +
 +
 +==== Dead Space Fraction ====
 +$\frac{V_D}{V_T} = \frac{P_ACO_2 - P_ECO_2}{P_ACO_2}$
 +
 +Formal measurement of $P_ECO_2$ requires volumetric capnography, which requires a capable ventilator or a dedicated measurement device.
 +
 +Thankfull, $P_ECO_2 \approx ETCO_2$, so an approimation would $\frac{V_D}{V_T} = \frac{P_ACO_2 - ETCO_2}{P_ACO_2}$
 +
 +
 +
 +==== Alveolar ventilation ====
 +$P_{A}O_2 = F_iO_2(P_{atm}-P_{H_2O}) - \frac{P_AO2}{RQ}$
 +$\dot{V}_A=k\frac{\dot{V}CO_2}{P_ACO_2}$
 +$\implies \dot{V}CO2 = \frac{\dot{V}_AP_ACO_2}{k}$
 +
 +To convert $F_ACO_2$ into $P_ACO_2$, we have $F_ACO_2(P_{atm} - PH_2O = P_ACO_2$
 +Similarly, using $F_ECO_2$, we can show $P_ECO_2 = F_ECO_2(P_{atm} - P_{H_2O})$
 +
 +$Volume_{expiredCO2} = Volume_{producedAlvCO2}$
 +
 +$V_TF_ECO_2 = V_AF_ACO_2$
 +
 +$V_TF_ECO_2 = (V_T - V_D)F_ACO_2$, and we can convert $F_ACO_2$ into $P_ACO_2$
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resources/checklists/ventilator_rounding.1691284040.txt.gz · Last modified: 2023/08/06 01:07 by admin

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