Week 2 - Mechanical Ventilation Flashcards
What are the 2 physiologic criteria for when you should be considering mechanical ventilation?
- Hypercarbia (PaCO2 > 50mmHg)
2. Hypoxemia (despite supplemental O2)
What are 4 causes of respiratory failure?
- Mechanical dysfunction of the lung
- Loss of respiratory control d/t impaired central respiratory drive
- Upper or lower airway obstruction
- Multisystem organ failure, cardiac arrest
What are 7 signs of impending respiratory failure?
- Increased respiratory drive
- Respiratory muscle fatigue
- Hypoxemia or hypercapnia
- Evidence of lung disease
- Loss of cough or gag
- Critical upper airway obstruction
- Decreased respiratory drive - LATE sign
What are the 5 goals of mechanical ventilation?
- Protect the lung from iatrogenic injury
- Promptly and aggressively treat the illness or injury
- Proper nutrition
- Assess extubation readiness daily
- Mobility
What is tidal volume?
Common setting?
quantity of gas delivered w/ each breath
5-8 mL/kg
4-6 mL/kg in PARDS
What is PEEP?
Common setting?
airway pressure at end of expiration
Start at 5-8 cm H2O
What is PIP?
Common setting?
maximal airway pressure reached during delivered breath
PIP = pressure control + PEEP
Only a setting in PC/PS
Normal set at 16-25
What is I:E?
Common setting?
time for the vent to deliver the volume of pressure breath and allow for exhalation
1:2 or 1:3
What is rate?
Common setting?
number of breaths/min delivered by ventilator
What is pressure support ventilation (PSV)?
all breaths spontaneous (patient initiated) and ventilator augments patient effort w/ pressure or volume
What is assist control (A/C) ventilation?
A/C ventilation provides full respiratory support. It takes over WOB for the patient.
All programmed breaths delivered within fixed inspiratory time (I-time)
What is SIMV?
Synchronized intermittent mandatory ventilation - combo of mandatory and spontaneous breaths
Patient or ventilator can initiate breath; ventilator will deliver entire breath to support
What vent mode is often better for neonates and patients with uncuffed tubes?
SIMV + PS/PC
What is plateau peak pressure?
Alveolar pressure - the equilibrium of pressures in lung when flow is stopped
Normal difference peak-plateau < 5
What is part of the respiratory exam for a patient on a vent?
- WOB (retractions, belly-breathing, nasal flaring, head bobbing)
- Breath sounds
- Waveforms on ventilator
- Patient-ventilator “synchrony” (Trigger, flow, inspiratory time, mode of ventilation)
What is part of the non-respiratory exam for a patient on a vent?
- Vital signs (HR, BP, SpO2)
- Appearance (pallor, diaphoretic, mottling)
- sedation/muscle relaxing
- Discomfort
What’s the pneumonic for troubleshooting a distressed vent patient?
DOPE D - displacement of tube O - obstruction P - pneumothorax E - equipment failure
What’s the pneumonic for troubleshooting decompensation during mechanical ventilation?
DOPE D - displacement of tube O - obstruction P - pneumothorax E - equipment failure
Capnography - decreasing EtCO2
Meaning?
ET tube cuff leak
ET tube in hypopharynx
Partial obstruction
Capnography - sudden increase in EtCO2
Meaning?
Return of spontaneous circulation (ROSC)
Capnography - bronchospasm (shark-fin appearance)
Asthma
COPD
Capnography - bronchospasm (shark-fin appearance)
Meaning?
Asthma
COPD
Capnography - decreased EtCO2 (variable changes)
Meaning?
Apnea
Sedation
What are some examples of restrictive lung disease (inadequate oxygenation)?
ARDS, aspiration pneumonitis, pneumonia, pulmonary fibrosis, pulmonary edema, alveolar hemorrhage, chest trauma
What are some examples of obstructive lung disease (inadequate ventilation)?
Asthma, COPD
What are some examples of severe metabolic acidosis?
Salicylate poisoning, septic shock, toxic exposures, acute renal failure, DKA
What are complications for a patient on a vent?
Diminished cardiac output and hypotension
Pulmonary barotrauma (eg. pneumothorax)
Ventilator-associated lung injury
Auto-positive-end-expiratory pressure (ie. intrinsic PEEP)
Elevated intracranial pressure
What is recommended vent mode and setting for inadequate oxygenation?
SIMV + PS
high PEEP (5-8) low tidal volume (3-6 or 5-8 depending on lung compliance)
Vent adjustment for a patient with persistent hypoxia despite increasing/max FiO2?
Increase PEEP
maybe increase I-time
What is recommended vent mode and settings for inadequate ventilation?
Pressure or volume controlled (SIMV + PS or PS alone)
low RR (8-16), max expiratory time (prolonged I:E, low I-time; 1:3 or greater)
Vent adjustments for dynamic hyperinflation and evidence of auto-PEEP?
lower RR (10-14)
shorten I-time (1:3 - 1:5)
Keep tidal volume 6-8
High peak + high plateau pressure. Causes?
Low compliance from underlying disease
Pneumothorax, severe pulmonary edema, pulmonary effusion, hyperinflation, elevated intra-abdominal pressure from ascites or compartment syndrome
High peak pressure + normal/low plateau pressure. Causes?
Obstruction of airflow within vent circuit (clogged ETT) or proximal airways (copious secretions, bronchospasm)
Low peak pressure (change). Causes?
ETT cuff leak
Accidental extubation
Low peak pressure (no change). Causes?
Consider pulmonary embolism
What is the recommended vent mode and settings for restrictive lung dz?
A/C (either volume or pressure controlled)
Higher PEEP (5-10) Lower tidal volume (4-6)
What is the recommended vent mode and settings for obstructive lung dz?
A/C (prefer volume)
Lower RR (10-14) Shorter I-time (to increase I:E ratio) 1:3 or higher
What lung dz would you allow permissive hypoxemia? SpO2 range?
Obstructive lung dz
SpO2 88-92%
What is the recommended vent mode and settings for severe metabolic acidosis?
Pressure support ventilation
PEEP 5-10
PS 10-15
Minute ventilation 18-25
How to adjust vent if PaO2 too low?
inc FiO2, inc PEEP
How to adjust vent if PaCO2 too high?
inc RR
inc tidal volume (volume controlled)
inc driving pressure (pressure controlled)
How to adjust vent if PaCO2 too low?
dec RR
dec tidal volume (volume controlled)
dec driving pressure (pressure controlled)
7 causes of hypoxemic respiratory failure?
- shunt
- VQ mismatch
- diffusion limitation
- dead space
- low FiO2
- low Pb (barometric pressure)
- alveolar hypoventilation
Examples when VQ ratio < 0.8?
asthma, COPD, interstitial lung dz, tracheobronchitis, pneumonitis
Examples when VQ ratio > 0.8?
thromboembolic disease, vasculitis, overdistension of alveoli during positive pressure ventilation
