vent refresher

static compliance

VT / Pplat - PEEP (100mL/cmH2O)

dynamic compliance

VT / PIP - PEEP (60-100mL/cmH2O)

alveolar air equation

(PB - 47)FiO2 - PaCO2/.8

P/F ratio

PaO2/FiO2 (380-450mmHg)

Vd/Vt

PaCO2-PeCO2/PaCO2 (.2-.35)

Raw

PIP - Pplat / flow (,5-2,5cmH2O/L/sec)

% shunt CcO2

(CcO2 - CaO2) / (CcO2 - CvO2) × 100 (less than 5% cardiac output)

CcO2

(Hb x 1.34 × 1) + (PAO2 x .003)

CaO2

(Hb x 1.34 x SaO2) + (PaO2 x .003)

CvO2

(Hb x 1.34 x SvO2) + (PvO2 x .003)

refractory hypoxemia

respiratory failure, PaO2 < 60 torr despite FiO2 >60%

full ventilatory support

CMV, A/C or SIMV (absence of spontaneous breathing)

partial ventilatory support

BiLevel PAP, PSV, A/C or SIMV (w/ spontaneous breathing)

CMV

controlled MV, all breaths delivered by ventilator no pt triggering, used for paralyzed or apneic patients, must set RR, VT (or PIP), FiO2, PEEP

frequency

initial setting 10-12(20)bpm → adjust to pt, increase to decrease PaCO2 (can lead to shorter e time/air trapping/auto-PEEP)

expiratory pause

measures auto-PEEP/air trapping

minute ventilation

tidal volume x RR (L/min)

tidal volume

initial setting 4-8mL/kg, 4 to reduce lung injury (ARDS 4-6, COPD/air trapping 5-7, obstructive (asthma) 6-8) target Pplat <30cmH2O 28 for ARDS

predicted body weight

males: 50kg + 2.3kg X (height in inches - 60), women: 45.5 instead of 50

initial FiO2

100% for severe/prolonged hypoxemia or abnormal cardiopulmonary status (emergency, post resus, smoke inhalation, ARDS) and 50% for mild to moderate hypoxemia or normal cardipulmonary status (overdose, post op)

PEEP

5cmH2O initially for refractory hypoxemia (post resus, smoke inhalation, ARDS) increase base on FiO2 requirement, PEEP tolerance and cardiovascular response

PSV initial

set to achieve 8-10mL/kg or RR 20-25bpm, reduce PS gradually (2-4cmH2O, minimum 5-8 is needed to overcome ETT resistance) watch for RR or SpO2 drop

PSV extubation endpoints

spontaneous RR 20-25bpm, spontaneous VT 8-10mL/kg, RSBI (RR/VT in L) <105, maintained w/o desat

flow rate

maximum flow delivered by vent during inspiration, air hunger is usually a peak flow issue (flow hunger) go w/ default setting unless pt needs change

I:E ratio

typically 1:2 to 1:4, longer E time for patients with air trapping/auto-PEEP

increased E time

can be achieved by increasing flow rate, increasing E time, decreasing I time/I time %, decreasing frequency, decreasing tidal volume

decelerating flow pattern

lower PIP, bettwer gas distribution, mimics normal breathing

sine flow pattern

most physiological flaw, reduces dyssynchrony

peak inspiratory pressure

set based off plateau number (from insp hold) on vol control → pressure control start from the plateau pressure (safe zone from overdistension) 10-15 above PEEP

low exhaled volume alarm

100mL lower than expired tidal volume, detect and alert leaks or disconnect

low inspiratory pressure alarm

10-15cmH2O below the observed PIP, detect and alert leaks or disconnection

high inspiratory pressure alarm

10-15cmH2O above observed PIP, detect and alert conditions due to increase in resistance or decrease in compliance (water in circuit, secretions, ET kinking, tension pneumo, coughing)

apnea alarm

15-20sec time delay, detects and alert apnea or circuit disconnection

high frequency alarm

10bpm over observed total frequency, detect and alert patient distress or improper sensitivity setting

high and low FiO2

5-10% over the analyzed FiO2, low 5-10 below

safe pressure limits

PIP <50cmH2O, Pplat <30cmH2O, MAP <30cmH2O, PEEP <10cmH2O (prevent barotrauma)

high peak low plat

mucus plug, bronchospasm, ET tube block, biting

high peak high plat

ARDS, pulmonary edema, pneumothorax, ETT migration to single bronchus, effusion

MV indications

ABG → >50mmHg PaCO2 with pH <7.25, COPD pH <7.2, drug overdose, flail chest, neuromuscular issues

impending ventilatory failure

VE >10L/min, VC <10mL/kg, NF/MIP -20, RR >35bpm, VC >10mL/kg

P(A-a)O2

>350 P/F indicator, normal between 5-20mmHg