Avd mech vent exam 2

Desired FiO2 formula

= (current FiO2 x desired PaO2) / current PaO2

Desired RR formula

= (current RR x current PaCO2) / desired PaCO2

Desired Vt formula

= (current PaCO2 x current Vt) / desired PaCO2

Desired VA (alveolar ventilation) formula

= (Current VA × Current PaCO2) / Desired PaCO2

a high minute ventilation will result in a ____ PaCO2

low

a low minute ventilation will result in a ____ PaCO2

high

If PaO2 is too low what can you change

increase FiO2 and/or PEEP

if PaO2 is too high what can you change

decrease FiO2 first, then decrease PEEP if needed

Oxygenation changes are made by

FiO2 and PEEP

Ventilation changes are made by

RR and Vt

If PaCO2 too high what change can you make

increase RR or Vt (prefer RR first if volumes already lung-protective)

If PaCO2 too low what changes can you make

decrease RR or Vt

norm flow trigger setting

1-10L/min below base flow

flow triggering mechanism

continuous bias flow in circuit; pt’s insp effort reduces flow to trigger

flow triggering pros

• faster response

• more comfortable

• gas continues to flow during exhalation

norm pressure trigger setting

-1 to -2 cmH2O

mechanism of pressure triggering

pt generates negative pressure; exhalation valve must close to sense change

pressure triggering risk

if set too negative (ex: -4 to -5 cmH2O), effort is excessive

what can make it too difficult for pt to trigger flow

if the difference set between base flow and flow trigger is too large

what can make it too difficult for pt to trigger pressure

if set more negative than -2 cmH2O

clinical cue of pt having difficulty triggering breathe

pt showing increased WOB, accessory muscle use, missed triggers

if vent is alarming what are the 3 steps you as an RT should do

step 1: go to pt - ensure they are being ventilated

step 2: if unsure or pt unstable, disconnect from vent and bag with 100% O2

step 3: then troubleshoot machine/circuit

pt problems that could result in vent alarming

• bronchospasm

• secretions

• pneumothorax

• decreased compliance

• agitation

circuit/equipment problems that could result in vent alarming

• disconnection

• leak

• kinked tubing

• water in circuit

• malfunctioning valve

pressure limit alarm setting

~10 cmH2O above PIP

low-pressure alarm setting

~5-10 cmH2O below PIP

what to inspect for leak check

• around humidifier

• connections

• ETT cuff

• water traps

COPD primary goal for vent management

reduce air trapping and WOB

COPD vent management strategy (Vt, rr, flow, PEEP)

Vt: 6-8mL/kg

rr: 8-16/min

Flow: >60 L/min (shorter insp time)

PEEP: low/modest; careful w/ auto-PEEP

COPD vent management targets (Pplat, PaO2, FiO2)

Pplat < 30cmH2O

PaO2 55-75 mmHg

FiO2 < 50%

high-yield risk for COPD on vent

dynamic hyperinflation/auto-PEEP

asthma primary goal for vent management

avoid air trapping and excessive pressures

asthma vent management strategy (mode, rr, Vt, I time, flow)

• VC-CMV or PC-CMV

• rr < 8 → long expiratory time for severe obstruction

• Vt 6-8mL/kg

• TI ≤ to 1 sec

• flow 80-100 L/min

asthma vent management targets (CO2, pH)

premissive hypercapnia w/ pH ≥ to 7.2

risks for asthma pts on vent

air trapping, high peak/plateau pressure

neuromuscular weakness vent management primary goal

provide adequate ventilatory support

neuromuscular weakness vent management strategy (mode, Vt, rr, flow, PEEP)

• Assist control or volume control

• Vt 6-8mL/kg

• rr 8-16

• flow ≥ 60 L/min

• PEEP ~ 5 cmH2O if needed

neuromuscular weakness vent management targets (Pplat, FiO2)

Pplat < 30 cmH2O

FiO2 may start at 21% if oxygenation normal

risk of neuromuscular weakness pt on vent

hypoventilation from muscle weakness

closed head injury vent management primary goal

protect airway and avoid worsening ICP

closed head injury vent management strategy (CO2)

• avoid routine hyperventilation

• temporary PaCO2 25-30 mmHg only for uncontrolled ICP, then gradual normalization

closed head injury vent risk

abrupt CO2 changes or excessive intrathoracic pressure affecting ICP

ARDS vent management primary goal

improve oxygenation while limiting VILI

ARDS vent management strategy (mode, PEEP, Vt)

• PC-CMV or VC-CMV

• PEEP to prevent collapse

• Vt 6-8 mL/kg for mild-mod; Vt 4-6 mL/kg for mod-severe (lung-protective)

ARDS vent management targets (Pplat, SaO2)

Pplat < 30 cmH2O

SaO2 ~ 88-90%

ARDS risk for vent

overdistension, collapse, rapid CO2 rise

CHF/pulmonery edema vent management primary goal

reduce WOB and improve oxygenation/hemodynamics

CHF/pulmonary edema vent management strategy (mode, Vt, rr, flow, PEEP)

• VC-CMV or PC-CMV

• Vt 6-8 mL/kg

• rr ≥ 10

• flow ≥ 60L/min

• PEEP 5-10 cmH2O

CHF/pulmonary edema vent management targets (FiO2, SpO2)

start FiO2 at 100%, titrate to SpO2 > 90-92%

CHF/pulmonary edema vent risk

hemodynamic effects of positive pressure (decrease venous return, hypotension)

Initial vent setup steps

• verify orders: mode, Vt, rr, FiO2, PEEP, sensitivity

• determine ABG goals

• vent check: complete setup/calibration; leak test

• bedside assessment

  • auscultation: BBS, ETT position

  • vital signs: HR, BP, SpO2, RR

  • alarms: set appropriately (pressure, volume, apnea)

• diagnostics: ABG, CXR, relevant labs

frequency of pt-vent system checks

1-4 hrs (institution policy)

when to check pt-vent system

• before/around ABG sampling

• after vent changes or new orders

• after transport/testing

• during acute clinical changes

• when vent performance is questionable

what to document on first vent system check

• mode and sensitivity

• Vt, rr, MV

• tubing compliance and delivered Vt

• alveolar ventilation and dead space considerations

• pt response: vitals, comfort, synchrony

PIP

peak inspiratory pressure

• influenced by resistance + compliance

Pplat

plateau pressure

• marker of alveolar/static pressure; measured with insp hold

• disease guidelines emphasize < 30 cmH2O

PTA

transairway pressure = PIP - Pplat

• represents resistive pressure across airways

EEP/PEEP

end-expiratory pressure/positive end-expiratory pressure

• relates to alveolar recruitment, oxygenation, and hemodynamics

increase PIP, unchanged Pplat =

increased RAW

• secretions, bronchospasm, kink

increased PIP and increased Pplat =

decreased compliance

• pulmonary edema, ARDS, pneumothorax

Static compliance equation

Cstatic = Vte / (Pplat - PEEP)

Static compliance focus

uses plateau pressure; reflects rsp system compliance under static conditions

Dynamic compliance equation

Cdyn = Vte / (PIP-PEEP)

dynamic compliance focus

uses peak pressure; affected by both resistance and compliance

Airway resistance equation

RAW = (PIP-Pplat) / flow (L/s)

airway resistance focus

resistive pressure difference relative to insp flow

interpretation of decreased Cstatic

stiff lungs

• ARDS, fibrosis, edema

interpretation of decreased Cdyn with normal Cstatic

increased RAW

• bronchospasm, secretions

interpretation of increased RAW

airway narrowing, obstruction, tube issues

lower infection point of the static pressure-volume curve marks

recruitment of large numbers of alveoli

clinical use of lower inflection point

set PEEP above this point to prevent collapse

upper inflection point of static pressure-volume curve indicates

onset of overinflation

clinical use of upper inflection point

keep Vt/pressure below this region to reduce VILI

what do you look at to monitor oxygenation/ventilation for vented pt

• SpO2

• ABGs

• RR

what do you look at to monitor hemodynamics for vented pt

• BP

• cardiac output

• HR

what do you look at to monitor vent mechanics

• PIP

• Pplat

• PEEP

• compliance

• RAW

in an obstructive (COPD) case what would you examine first on vent

• RR

• Vt

• flow

• I:E ratio

• presence of auto-PEEP

how can you increase expiratory time

• decrease RR

• increase flow

• decrease Vt if large

• adjust I:E (1:3 - 1:4)

what pt cases need longer expiratory time

obstructive cases

what can you adjust on vent to help an asthma case with permissive hypercapnia

aggressive normalization of PaCO2 requires high RR/Vt

if you increase RR or Vt on asthma case to blow off CO2 what is a risk you need to monitor

increased air trapping and pressures

what is the priority for an asthma case with permissive hypercapnia

maintain acceptable pH (≥ 7.2) and avoid barotrauma

in an ARDS case what are 3 vent parameters you want to focus on the most

• Vt: low (4-6) to limit overdistention

• PEEP: enough to prevent collapse and improve oxygentation

• Pplat: keep < 30 cmH2O → balance oxygenation vs VILI

what steps do you take to assess an alarm case for an unstable pt

go to pt → assess breathing → disconnect and bag w/ 100% O2 → then check circuit, ETT, settings

what is the pattern and what would you assess in pt with high PIP but stable Pplat

• pattern: increased RAW

• assess: secretions, bronchospasm, kinks, water in tubing, ETT patency

what is the pattern in pt with high PIP and high Pplat

decreased compliance (asthma, ARDS, pneumothorax)

isolated PIP rise =

increased resistance

both PIP and Plat rise =

decreased compliance

PaO2 problem you would adjust what vent parameters

FiO2/PEEP

PaCO2 problem you would adjust what vent parameters

RR/Vt

simple fixes for increased RAW issue

• suction - if secretions suspected

• bronchodilator - if bronchospasm pattern

• check circuit - remove water, unkink tubing

• check ETT - reposition, bite block if needed

• reduce insp flow - if flow is excessively high and causing turbulent resistance

• lengthen exp time - if dynamic hyperinflation is contributing

simple fixes for decreased compliance issue

• increase PEEP - improves recruitment

• reduce Vt - lung-protective strategy

• check for pneumothorax - tx if present

• diuresis - if pulmonary edema suspected

• prone positioning (ARDS)

• recruitment maneuvers if appropriate

• fix abdominal pressure (NG tube, repositioning)

P/F ratio formula

PaO2/FiO2

transairway pressure (PTA) formula

PIP - Pplat

Deadspace Ratio (VD/Vt) forumla

(PaCO2 - PeCO2) / PaCO2

x Vt = VD

Current Alveolar Vent (VA) / Alveolar Minute Volume (VE) formula

(Vt - VD) x RR

Cardiac Output (QT) forumla

SV x HR

Arterial Oxygen Content (CaO2) formula

(1.34 x SaO2 x Hb) + (0.003 x PaO2)

Total Oxygen Delivery (DO2) formula

CaO2 x QT x 10

Alveolar Gas Equation (PAO2)

FiO2 (PB - 47) - (PaCO2 / 0.8)