Chapter 10 - Ventilatory Assistance

Ventilation

Movement of oxygen and co2 at the alveolar level

Distensibility

How easily the lung stretches

Compliance

Change in lung volume

Eupnea

Normal breathing pattern

Cheyne-Stokes Respirations

• Deep to shallow respirations followed by periods of apnea

• Etiol: CNS disorders & congestive HF

Biots Respirations

Irregular breathing with abrupt pauses

• etiol: brainstem injury

Kussmaul Respirations

• Rapid, deep, regular breaths

• Etiol: DKA

Apneustic Respirations

• Gasping inspirations with ineffective expirations

  • Pons injury (etiol)

What can be done to minimize chest hairs sounding like crackles?

Wetting the chest hairs

PaO₂ (Range)

80 - 100 mmHg

Hypoxemia (in terms of PaO₂ )

< 60 mmHg

SaO₂

92 - 99%

How to distinguish pericardial from pleural friction rub?

Pleural friction rub is not heard if pt holds their breath upon auscultation

End-Tidal CO₂ (ETCO₂) Monitoring

• measures CO2 at the end of exhalation/direct measurement of arterial co2

(amount of CO2 after exhaling)

Normal ETCO₂

2 to 5 mmHg below PaCO₂

_{**should be around the same as PaCO2}

PaCo2-ETCO2 Gradient

ETCO₂ is substracted from PaCO₂

Dead Space

Lung is being ventilated but not perfused

Colorimetric ETCO₂ Detectors

Used to confirm tracheal intubation placement

Fraction of Inspired Oxygen (FiO₂)

Amount of oxygen the patient gets

**hard to predict since it depends on patients inspiration efforts

When is oxygen humidification necessary?

Anything > 4L/min

When is systemic humidification necessary?

When secretions remain thick despite humidification

Heat-Moisture Exchange (HME) Device

• Functions as an artificial nose by humidifying and warming the inspired air

• NA: inspect regularly for accumulated secretion (sterilize or get new one)

Up until what rate does a nasal cannula go?

Up to 6L/min

High Flow Nasal Cannula

• delivers 15L - 40 L/min via face mask

• NA/RTA: ensure adequate humidification is supplied

Partial Rebreathing Mask

• delivers 35% - 60%

• prevent the bag from deflating no more than 1/2

Non Rebreathing Mask

• delivers 60% - 80%

• has one-way valves to ensure pt doesn’t breathe in exhaled co2/room air

• prevent bag from deflating

Venturi Mask

• delivers precise FiO₂

• ports are color coded by amount!!

• indications: COPD or hypoxemic patients (prevents excess oxygen admin)

ETT Cuff Purpose

Seals the trachea and diverting the air to pass THRU the ETT

Verifying ETT

• Auscultating epigastrum

• Observe for equal chest expansion

• Chest Radiograph 🏆

• ETCO2 Monitor

Suction Duration

10 to 15 secs

Positive Pressure Ventilation

Forces air into lungs

Tidal Volume

Amount of air needed to inflate lungs

Range: 500cc

Why would an inverse I:E ration (I > E) be necessary?

To improve oxygenation for pts with noncompliant lungs

• gives alveoli enough time to fill and prevent collapse

PEEP

Pressure used to keep alveoli open and prevening collapse

Normal PEEP

3 to 5 mmHg

Why may PEEP be used to decrease the use/amount of FiO₂ ?

Due risk of oxygen toxicity from a high FiO₂

How does a high level of PEEP lead to pneumothorax?

It can cause overinflation → popped alveoli/lung

What amount of discrepancy between EV_T vs V_T requires intervention?

>50mL

PIP > ___ can cause VILI

40 mmHg (so avoid!!!)

Total RR

MV RR + Pts RR

Assist-Control

(Continuous Mandatory Ventilation)

• Every breath delivered & initiated by the ventilator

• Delivers a SET V_T (so if pt has a spontaenous breath it is forced take the full V_T)

Synchronized Intermittent Mandatory Ventilation (SIMV)

• Allows pt to take over WOB bc they dictate the V_T with their spontaneous breath

• More comfy for pt!!

Pressure Support

• Form of spontaneous breathing supported by pressure

• kinda last step b4 extubation

High Peak Pressure Alarm

• Think High Blockage

  • kinks

  • dyssynchrony

  • biting ETT

  • accumulated secretions

Low Pressure Alarm

• leakage

• disconnected from ventilator

• malfunction

Barotrauma

• Pressure trauma causing lung injury

Tension Pneumothorax

• life-threatening

• air in pleural space causing mediastinal shift

• ss: tracheal deviation (away from affected side)

• tx: needle aspiration with chest tube

When FiO₂ is 1.0, how is there a risk for oxygen toxicity and damage?

• there is a lack of nitrogren

  • nitrogen: prevents collapse of the alveoli

Goal for FiO2

Keep < 0.6

MV effect on Hemodynamics

• hypotension

• ⬇ CO

MV Effect on GI

• Stress ulcers

  • Tx: prophylaxis (ex. PPIs/H2)

T/F: A high carb diet increases the pts WOB

T

Why are daily sedation vacations necessary?

• To assess patients readiness to be off sedation

• Reorient/evaluate patient

• Reduce dose PRN

Spontaneous Breathing Trial (SBT)

• 30 to 120 mins

Sedation while on MV

Promotes synchronous breathing with the vent

T-Piece

• used for weaning trials

  • only provides humidified oxygen

• pt does all WOB and there are NO alarms (staff needed!!!)

Cuff Leak Test

• for pts high risk for post-extubation stridor