2. Mechanical Ventilation Flashcards by Tegan Turner

How does a normal respiratory cycle start?

negative intrathoracic pressure by coord movement diaphragm, intercostal muscles elevates lateral ribs like a bucket handle increasing intrathoracic pressure so net pressure pulls air into lungs

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How does expiration work?

relax diaphragm recoil chest decreases intrathoracic volumes increase pressure in ch cavity passive exhalation

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Amount of positive pressure required for adequate ventilation includes what factors?

pt’s resp effort and therefore passive relaxation on expiration (so really inspiration is based off pt effort)

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During inspiration, how does this effect cardiac?

decreased intrathor pressure augments venous return and preload cardiac otput incr so incr pressure gradient LV and aorta

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PPV - how does this effect cardiac?

venous return falls cardiac output falls derease LV and aorta so can get hypotension!

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Invasive ventilation: how does gas get to lungs?

vol duration freq degreev interaction pt with ventilator

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How the ventilator delivers gas to lungs - __ variable

control

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Control variable in ventilator settings: what are the options?

VC - sp volume 2. PC - sp pressure

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Inspiratory flow rate defn

amount of time breath is delivered (inspiratory time and speed throiugh circuit)

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Circuit defn in ventilator: how __ delivery of a breath

terminates

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How does volume control work?

breath defined by tidal volume - clinician sets inspiratory vol and flow rate

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Benefit of volume control setting on ventilator:

ability to control tidal volume and minute ventilation

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When is volume control setting dangerous (ie what conditions?)

impaired resp system compliance as can result in high airway pressure and barotrauma

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How does pressure control setting work?

set amount of pressure applied to lungs for a specific abmount of time - set inspiratory pressure so that TV and inspiratory flow rate vary asfunctions of lung compliance and airway R

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Pressure control can help to prevent ___ trauma

baro

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Why might pressure control ventilator setting help an intubated pt with high resp drive?

inspiratory flow not fixed

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Pressure control settings - cons

TV cannot be guaranteed or limited as lung compliance changes

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When should volum controlled ventilation be used?

when need a sp TV: - ARDS (as low TV improves mortality) - decreased chest wall compliance so that adequate TV is deliveredc (morbid obesity, chest wall burns)

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When should pressure control ventilator setting be used?

risk of dynamic hyperinflation and instrinsic PEEP: sev asthma or COPD

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Pressure regulated volume control - how does this work?

delivering breaths combining vol and pressure strategies delivers a specific TV while minimizing airway pressure - pressure limit set and sounds when exceeded

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Ventilator mode - what does this refer to?

sp amount of resp support provided by ventilator and how often initiates a breath

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Ventilator mode - example modes?

A/C (assist control mech ventil) IMV - intermittent CMV - cont

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Ventilator mode - key differences AMV/IMV/Cont spon vent:

AC and IMV provide pt with sp MIN number of breaths as defined by ventilator to deliver via pressure/control methods CSV: no mandatory breaths, determined by effort of pt and augmented with applied pressure or vol airway

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Assist conttrol mech ventilation: intended to do what, for who?

provide full vent support to pt with little or no spont resp activity by cont delivery of breaths at preset rate *if has any resp this will also be assisted by vent

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A/C mode: for promotion of ventilator synchrony: spont pt initiated breath should take priority over __

preset

ne of the biggest challenges with A/C ventilation, however, is that patient-initiated breaths are not proportional to patient ___; when inspiratory effort is detected, a full-sized breath is delivered.

effort

A/C mode requires sedation to avoid what complications?

hyperventil
air trap
hypotension

Intermittent mandatory ventilatopn: provides what, to who?

both mandatory and spont breaths
mandatory at preset rate but syncronized as much as possible with spont patient effort

IMV ventilation: if a patient has a higher spon- taneous respiratory rate than the preset rate, the patient receives ...

all preset full breaths at the set rate

IMV: why is this in some ways preferred over A/C?

additional breaths by pt are vol or pressure that commesurate with pt resp eoffrt so less hypervent and air trap

CSV: only augments...

pt breathing spontaneously

What is positive end expiratory pressure/PEEP?

maintenance of positive airway pressure after completing passive exhalation

PEEP: how does it help in resp failure?

incr FRC
improves o2
decreases intrapulmonary shunting because helps keep alveoli open

PEEP: what disease is it most useful in?

diffuse parenchymal lung idsease

PEEP: how can this negatively effect cardiovascular and pulmonary efforts?

increase intrapulm and thoracic pressure so get reduced venous return, CO, lung overdistension, PTX

What is auto-peep?

improper assisted ventilation when adequate time is not allowed between breaths for complete exhalation

What is noninvasive ppv?

delivery of cont spontaneous ventilation via mask (instead of ETT)

MC examples of NIPPV in ED

CPAP
BIPAP

BIPAP - how does it work?

higher pressure inspiration and lower pressure on expiration

**Bipap:

just as with invasive mechanical ventilation, IPAP augments patient respi- ratory effort by decreasing the work of breathing during inspiration, whereas EPAP acts as PEEP to maintain FRC and alveolar recruit- ment.

**Notably, although PEEP, CPAP, and EPAP all represent positive airway pressure at the end of expiration, PEEP, by convention, refers to pressure applied during invasive mechanical ventilation, whereas CPAP is the application of positive pressure (invasively or noninva- sively) during spontaneous breathing. The terms are occasionally used interchangeably.

Why is high flow nasal cannula so helpful?

high flow more closely match pt inspir flow and vol demands to increase fo02
2. high flow washes out anatomic dead space to repl with o2
3. fio2 and flow rate are titrated ind
4. small PEEP 1-3cmh2o
5. gas humified and heated so more tolerable
6. NP occlude nares

When is high flow nasal cannula indicated?

1. acute hypoxemic resp failure without sign hypercarbia
and
2. pt for whom supplementary intrathoracic pressure would not be necessary

CI high flow nasal cannula

1. non patent upper airway
2. depressed mental status
3. facial injury
4. inability to manage secretions
5. resp arrest

Relative contraindications to NPPV:

1. decreased LOC (can't think)
2. lack of resp drive (can't breath)
3. incr secretions (can't swallow)
4. HD instability (can't BP)
5. facial trauma preventing seal (can't face mask)

Who are best candidates for NPPV?

COPD exac
cardiogenic pulmonary edema with fatigue

How does NPPV help cardigeogeic HF?

elevation Intrathoracic pressure
decreases LVEP and traunsumurla pressure to decr afterload
decr RV preload to help LV compliance

First method of NPPV recommended?

ful; face mask

How to start BIPAP setting?

IPAP at 10cm h2o
EPAP at 5cmh20
titrate to pt response, pressure tol,RR, o2 sat
titrate by 1-2cm at a time

Changes to IPAP on bipap specifically effect what?

modulate TV and min ventilation

Changes in EPAP impact with?

oxygenation to combat atelectasis and improve alv recruitment

If IPAP >20cm, risk of ?

discomfort and gastric insuff

HFNC: rate up to?

80L/min

HFNC: initial settings?
max?

fio2 50$ and flow rate of 40L/min
max fio2 of 100%, 60L/min

HFNC:titrate fio2 to ?

spo2

HFNC: titrate flow to?

hypoxemia and dyspnea relief

HFNC: ROX index - spo2/fio2 as compared to RR to predict failure
what numbers are important?

<3.85 high risk failure
>/=4.88 measired at 2, 6 or 12 hours after initiate suggest lower risk intubation

A/C ventilator for paralyzed pt: initial settings?

TV 6-8ml/kg IBW
Rate 12-14 breaths per min
initiall pressure should not exceed 30
fio2 of 1.0 and titrate down to mainttain o2 sat 88-92%
PEEP at 5

How to know if you should change mechanical ventilation settings?

pulse ox
etco2
ventil pressure
blood glas levels: 15-20 mins post initiation to determine ph and adequacy of exchange

Risks/cons of using vbg to change vent settings?

1. pco2 between venous and art samples not reliable comparison
2. capnography better correlates iwth pco2 of art sample
arterial sample required for fio2/pao2 calculation

What is a key measurement of severity of hypoxemia in ARDS?

fio2/pao2 relationship from abg

How to adjust the pco2 - ventilator settings wise

- change minute ventilation: TV and RR

How to avoid oxygen toxicity (pao2 >120mmhg)?

fio2 reduced at earliest opp
PEEP helps

How to ensure pressure in ventilator circuit (including lungs) is adequate?

peak inspir pressure
plateau pressure

What is the PIP?

max pressure in ventil circuit during a breath cycle
represents resp sys compliance and R

In PC ventilation, how to calculate PIP?

sum of set pressure target and PEEP

VC - how is max alveolar pressure determined on ventulator?

inspiratory hold at end inspire (plateau pressure)

Sudden incr airway R or decr lung compliance results in __ airway pressure during VC

incr

Sudden incr airway R or decr lung compliance results in __ tidal vol during PC ventil

reduced

*Decreases in lung pressure, conversely, indicate decreased resistance or decreased airflow in the ventilatory circuit and should prompt investigation of the ventilator circuit for leaks.

For patients with underlying respiratory failure secondary to increased airway resistance such as in asthma or COPD, gradual decreases in ? indicate clinical improvement.

PIP

Multiple validated tools are used to guide appropriate levels of sedation for mechanically ventilated patients. Name 2

Crit- ical Care Pain Observation Tool (CPOT) and Richmond Agitation- Sedation Scale (RASS).

analgesia in ventilated pt: __may be preferred in patients with renal insufficiency

fentanyl

What med is typically used for sedation post intubation?

propofol

Does propofol penetrate BBB?

yes

SE of propofol

hypotension secondary to venous capacitance
suppreses myocardial contractility

What does to start propofol infusion?

0.1mg/kg/min

what is propofol inusion syndrome?

prolonged/high dose infusion: metabolic acidosis, rhabdo, renal and liver injury, cardiovascular collapse

**sedation with benzodiazepines should be first attempted with intermittent bolus administration before a continuous infusion is used. The most commonly used benzodiaze- pines are midazolam (0.01 to 0.05 mg/kg IV push) and lorazepam (0.02 to 0.04 mg/kg IV push).

when does ventilator assisted pneumonia typically occur?

within 4d of mech ventilation

how to decrease risk of VAP?

- management secretion: suction/NG or OG tube, semirecumbent with head at least 30 deg
-daily sedation vacation
-assessment of extubation readiness
-PUD prophylaxis
-oral decontam
-GI decompression

Sudden change in a ventilated pt's condition: recommend?

1. Vital signs - hypotension/cardiac arrest = removed vent, bagged manually 100% on o2 --> think tension PTX, incr iPEEP, accidental extub
- check breath sounds
-disconnect from vent will cure hypot with iPEEP, not tension PTX

Acute decreases in PIP indicate discontinuity in the ventilator circuit, which could include ?2

inadvertent extubation or disconnection from the circuit

Patients with increased PIP can be considered in two categories—

those with con- comitant increases in Pplat and those with unchanged Pplat

both PIP and Pplat acutely increase, this suggests decreased...

compliance of resp system

levated PIP with unchanged Pplat indicates problems with increased...

airway R in lungs of vent circuit

Ventilatory management of COPD

- broncodil
- CS
-decrease RR
-decr TV
-decr inspir vol while incr expir (1:4)
- o2 sat 88% - reduce min vent for permissive hypercap
-PEEP at 5

How to manage asthmatics on ventil (differences from copd specifically)

- low RR with max expir time
VC: TV 6-8ml/kg IBW
RR 8-12 breaths/min
low PEEP of 3-5cmh2o
PEEP to match approx 80% of iPEEP
I:E 1:4

ARDS ventilatory settings

TV 4-6ml/kg based on IBW
Pplat <30cm h2o

in patients with ARDS (Pao2/Fio2 < 300), a low tidal volume (≤6 mL/kg of IBW) and low plateau pressure (≤ 30 cm H2O) ventilation strategy should be used.

How does mechanical ventilation cause VILI?

- alveolar overdistension, volutrauma due to high TV
elevated pressure --> alveolar rupture, ptx, pneumomeediastinum

How to limit risk of VILI?

max end inspir alveolar pressure 30-32cm h2o
min diff end inspir pressure/plateau pressure, PEEP, minimizing driving pressure

Complication of PPV: auto peep defn

accumulation of end expir vol and end expir pressure when exhalation cannot be fully complete so get breath stacking

Complication of PPV: auto peep = __ PIP and sx?

high
difficulty triggering braths
hypot
potential circulatory collapse

Complication of PPV: auto peep - tx?

1. decrease RR or inspiratory time
2. incr inspir flow rate
= expir increase time

2. Mechanical Ventilation Flashcards

(98 cards)