ventilators Flashcards
why we need ventilators
- Inability of the lungs to keep up with the body’s needs
- Airway compromise (Trauma, burns, fractures, etc)
- Stridor
- Loss of respiratory drive (Strokes, brain injury, intoxicants)
- Treatment for increased intracranial pressure: (To induce hyperventilation to lower intracranial pressure)
- Inability to ventilate properly
- Inability to oxygenate appropriately
noninvasive ventilation
Nasal cannula (in L)
Venturi mask (variable valves for 24-50% fiO2)
Nonrebreather (100%/15L)
High flow nasal cannula (can vary both the rate and the Fio2 up to 100%)
CPAP PAP/FIO2)
BIPAP (IPAP/EPAP/Fio2) The only true noninvasive VENTILATION
invasive ventilation
Endotracheal Intubation:
Assist Control- volume controlled versus pressure controlled
Synchronized Intermittent Mechanical Ventilation
Pressure Support
Many others!
oxygenation
use lowest value of oxygenation to maintain art. hemoglobin sat of 90% or more (PO2 of 60mmHg)
- higher levels have no proven benefit and may cause free radical damage
- restoration of normoxia may cause HYPOventilation in chronic hypercapnic pts (high CO2) -(lose drive to breathe (low O2))
noninvasive positive pressure ventilation
- Bilevel positive pressure ventilation (BIPAP) vs. Continuous positive pressure ventilation (CPAP)
- Full face mask, nasal mask, nasal pillows can all be used
noninvasive positive pressure ventilation: first in line for
pts with hypercapneic respiratory failure who can protect their away, handle their secretions and tolerate the mask (reduces need for intubation)
for chronic resp. failure, this tx is tried and can easily be used at home for OSA, obesity hypo vent.
CPAP
for advanced disease if a patient fails CPAP they may be transitioned to nocturnal home BIPAP
for acute resp. failure in hospital, this is preferred
BIPAP
invasive ventilation: tracheal intubation indications
Hypoxemia despite supplemental oxygen Upper airway obstruction (stridor) Impaired airway protection (trauma) Inability to clear secretions (relative) Severe respiratory acidosis Progressive general fatigue, tachypnea, use of accessory muscles, or mental deterioration Apnea
Continuous mechanical ventilation (assist control)
Can be volume controlled or pressure controlled (typically use volume control)
factors set:
-Fio2 (percentage of oxygen delivered)
-Respiratory rate
-Positive end expiratory pressure
-Tidal Volume (in Volume control) vs Peak Pressure (In Pressure control)
in acute resp. failure, begin with
100% Fio2 and quickly taper down to lowest level possible to maintain saturations
RR may inc. from (12) in these pts
hypercapneic, to blow of CO2 and red. acidosis
tidal volume is calculate based off
ideal body weight
Typically aim for 6-8mL/Kg of IBW (which is calculated based on sex and height)
Higher tidal volumes may also allow for blowing off of CO2 but be careful, too high TV may result in
barotrauma
any given TB will cause lungs to reach certain pk pressure (compliance), aim to keep pressures…
LOW:
PEEP, why necessary?
positive end expiratory pressure (relationship btw TV and pk pressure)
need to prevent atelectasis!
typically PEEP = 5
theses pts may need higher PEEP to maintain oxygenation
ARDS pts
PEEP causes inc. pressure during exhalation, can cause
cardiopulmonary changes (elevated intrathoracic pressure causing decreased systemic venous return) leading to decreased cardiac output and hypotension *turn PEEP to 0 during acute hemodynamic compromise
PEEP also increases risk for
tension pneumothorax in pt with known PTX
temp. turn off PEEP til definitive tx given
example volume control settings
rate of 12/Fio2 of 35%/ TV of 450 and PEEP pf 5
-pt. breathes over vent. @ rate of 18, for the 6 additional breaths the pt. still receives set TV, FiO2, and PEEP
difference btw volume and pressure control
- in volume control you set a TV and based on lung compliance the lungs produce a certain peak pressure
- In pressure control you set the peak pressure and based on the lung compliance the lungs produce a certain volume
- otherwise identical
problem with pressure control
it doesn’t give a set TV and therefore if not watching closely might have small tidal volumes leading to hypercapnea
pressure support
pt. drives the breath, no set TV/rate
Besides for given Fio2 and PEEP the clinician choses a preset “pressure support” which is additional continuous pressure given to aid in overcoming resistance from endotracheal tube making it easier for patient to breath (gives additional support on top of pk)
-considered “weaning” mode (can pt. handle extubation?), CPAP, spontaneous breathing trial
Synchronized Intermittent Mechanical Ventilation (SIMV)
combination of both Volume Control AC and Pressure support
-previously “weaning” mode, now not as much, used by some surgeons, anesthesiologists, avoided in ICU pts
example of SIMV
This time if patient is overbreathing at a rate of 18 instead of receiving the set TV and for those additional 6 breaths, those 6 breaths are only given a predetermined additional pressure support
Therefore those 6 breaths are completely patient driven and only have some additional CPAP to reduce patient effort
if endotracheal tube is positioned poorly
may cause atelectasis of contralateral lung with hyperinflation of intubated lung
(aim to be 2-3cm above carina)
other complications of mech. ventilation
- Barotrauma from high transmural pressure can cause subcutaneous emphysema, pneumothorax, or gas embolism
- Volutrauma from overdistension of alveoli from excessive tidal volumes tends to cause inflammatory changes
- Ventilator associated pneumonias (VAP)
