W2 D4/5 - Mechanical ventilation Flashcards
Why is warming, humidifiying ventilated air important?
Ventilated patients recieve air after the upper airway therefore skipping the warming and humifying part
* patients tracheal mucosa may burn or crack without humidification
What is an HME?
Heat and Moisture Exchanger
* short term solution
* gas and air is warmed and humidified by the patients own body and returned on inhalation
Explain lung compliance
Examples that decrease it
How easily the lung accepts a volume of gas
* 15-25 cm H2O
* monitor peak airway pressure
* decreased = bad, less stretch
Decrease compliance from
* stiffening of lungs (edema)
* chest wall distensibility (rib fractures)
* conditions that occupy pleural cavity (hemothorax)
Volume cycled vs. pressure cycled ventilation
Volume cycled
* pt receives a set tidal volume
* pts pressure fluctuates
Pressure cycled
* pt gets a set PEAK pressure
* pts volume fluctuates
How do you calculate tidal volume for the patient?
Approx 6-8 ml/kg of body weight
* know that lung size is based on height, so if the patient is obese this may be inaccurate
What is the minute volume on a ventilator?
How many litres of gas/air the patient is receiving every minute
MV (L/min) = frequency RR x tidal volume
What is flow rate on the ventilator?
How fast the tidal volume is delivered
* slow inspiration and low flow to allow time for passive expiration
Which is the normal inspiration to expiration ratio?
1:2 inspiration:expiration
2 seconds in: 4 seconds out
What is PEEP on the vent?
What is alveolar recruitment maneuver?
Positive end expiratory pressure
* keeps the alveoli open at the end of expiration for better gas exchange
* pO2 will be maintained at a lower FiO2
* 2.5-5 cm H2O
* changes in PEEP may have effect on BP quickly
Disadvantages
* risk alveoli rupture causing pneumothorax d/t high PEEP
* decreased preload d/t low venous return from PEEP pressure on the inferior & superior vena cava
* increased ICP: d/t pressure on SVC, venous blood cannot drain down from the brain
ARM = temporary and short increase in PEEP to open collapsed alveoli
List the different modes of ventilation?
PSV - pressure support ventilation
PCV - pressure control ventilation
PRVS - pressure regulated volume control
ACVC - assist control, volume control
ACVS - assist control, pressure control
Non invasive support
* CPAP
* BIPAP
* Optiflow
Explain CPAP and its indications
Continuous positive airway pressure
* constant pressure to keep alveoli open for GE
* non invasive, tight fitting mask
* pt determining their own RR and VT
* used for OSA (sleep apnea)
Indications
acute respiratory failure, acute/chronic respiratory insufficiency, sleep apnea, CHF, neuromuscular disease
Explain BiPAP and its indications
Bi-Positive airway pressure
* provides inspiratory positive airway pressure IPAP for changes in VT
* and expiratory postive aireway pressire EPAP/PEEP for changes in oxygenation
* able to provide more support as i/e can be different
* nasal or full face mask
Indications
acute respiratory failure, acute/chronic respiratory insufficiency, sleep apnea, CHF, neuromuscular disease
What are some contraindications to noninvasive ventilation?
Patients who cannot/will not breathe spontaneously
* hemodynamically unstable patients
* respiratory/cardiac arrest
* facial trauma, burns, surgery
* uncooperative patient, sedated
Unable to protect their own airway
* excessive respiratory secretions
* reduced LOC
* esophageal or gastric surgery
Explain high flow nasal cannula delivery
Optiflow/airvo for example
* an air and O2 blend (21-100%)
* heated humidifer
Explain PSV
Pressure support ventilation
* spotaneous mode with no set RR or Vt
* set inspiratory pressure only
* when the patients breathes, the vent adds inspiratory pressure
* measure PS 5-20 cm H2O and PEEP
Explain ACVC ventilation
Assist control volume control
* VC, gives volume no matter what
* preset RR, FiO2, PEEP, pressure fluctuates
* preset volume will be delivered with any small inspiratory effort and without
* monitor PEAK 15-25 cmH20
* 6-8 ml/kg tidal volume
Explain ACPS/PCV
Assist control Pressure controlled ventilation
* pressure is always set, RR, PEEP, FiO2
* tidal volume changes
* used with non-compliant lungs
Different from PSV because ACPS has a set resp rate as well
How is peak pressure calculated?
PEEP + pressure support %
What is PRVC ventilation?
between AC-PC and VC
* guaranteed Vt
* limited peak pressure
* every breath is analyzed and pressure adjusts
Differentiate ACPC, ACVC, and PRVC
ACPC
* set pressure, set RR
* no set tidal volume
ACVC
* set volume, set RR
* no set pressure assistance
PRVC
* set volume, set RR
* varying pressure dependent on patient
