Mech ventilation Dr Ambrisko Flashcards
What defines ventilation
PaCO2
What defines oxygenation
How is it monitored
PaO2 or SpO2
arterial blood gas or pulse oximetry
What is considered hypoxemia
PaO2 <60 mmHg ⇔ SaO2 < 90%
How can oxygenation be improved?
How can good oxygenation be insured in most circumstances?
When breathing 100% O2 it CANNOT be improved by MORE ventilation
Could be improved by special respiratory manoeuvers
Use 100% oxygen
What does resistance & compliance limit?
flow & volume respectively!
what is the respiratory cycle
Inspiration
inspiratory flow time
inspiratory pause
Expiration
expiratory flow time
expiratory pause
what is mechnical ventilation (MV)
artificial ventilation where mechanical means is used to assist or replace spontaneous breathing
provided by a ventilator or a person
What are the types of ventilation
Spontaneous - pt determines when & how
Assisted - pt derermines when, ventilator determines how
Mandatory (or controlled) - ventilator determines when & how
What is IPPV
Intermittent Positive Pressure Ventilation
positive pressure only during inspiration (no PEEP)
what is IMV
Intermettent Mandatory Ventilation
predetermined # of positive breaths but pt can breath inbetween freely
what is CPAP
Continuous Positive Airway Pressure
spontaneous breath w/ positive pressure during both inspiratory & expiratory phases
can prevent lung collapse
what is PIP
Peak Inspiratory Pressure
highest pressure during inspiration
inflates alveoli, opens atelectasis, causes barotrauma
what is PEEP
Positive End Expiratory Pressure
positive pressure maintained during expiration
pressure keeps alveoli open (prevents re-collapse of alveoli)
Indications for PEEP
open thorax
lung parenchymal dz
following alveolar recruitment maneuver
indications for MV under anesthesia
in intubated pt that breathe 100% O2 used to DECREASE PaCO2
(to tx hypoventilation)
specific indications for MV under anesthesia
neuromuscular blockade
throacic sx
control of ICP
chest wall or diaphragmatic trauma
Side effect of MV
how to tx side effects
may cause hypotension in hypovolemic pt
Volume loading
change ventilator settings
turn off ventilator
Inotropic drugs (e.g. dobutamine)
pneumothorax & lung injury
Effects of hypercapnia
Direct effects of CO2:
- peripheral vasodilation*
- decr myocardial contractility (inotropy)*
- incr ICP*
- bradycardia*
Indirect effects of CO2 (via catecholamine release):
- tachycardia*
- incr myocardial contractility*
ventilating healthy lungs
TV: 10-15 ml/kg
for ruminants: 6-10 ml/kg
RR: 10-15(20) breath/min
Inspiratory time: 1-2 sec
PIP: 10 cmH2O if BW <10kg
20 cmH2O if BW >10kg
PEEP: 0-2 cmH2O
How is manual ventilation performed
- close pop-off
- squeeze reservoir bag until desired pressure reached
- release bag so pt passively expire
- open pop-off
- repeat cycle q 6 secs (10/min)
What are respiratory assist devices
ambu bag
demand valve
modes of MV
volume controlled
pressure controlled (preffered)
