Chapter 295 - Mechanical Ventilatory Support Flashcards
What is the primary indication for initiation of MV
Respiratory Failure
Types of respiratory failure
hypoxemic
hypercarbic
Hypoxemic respiratory failure occurs when arterial O2 saturation falls below which level despite an increased FiO2
<90%
Hypoxemic respiratory failure results from which conditions?
VQ mismatch
Shunt
Hypercarbic respiratory failure occurs if arterial CO2 values are greater than which level?
> 50 mmhg
Hypercarbic respiratory failure results from which conditions?
decrease minute ventilation
increase physiologic dead space
When respiratory failure is CHRONIC, patients are obligatorily treated with mechanical ventilation.
FALSE
only when acute is MV lifesaving
Respiratory failure with hypoxemia is the most common reason for instituting MV. This accounts for how many percent of all ventilated cases?
65%
Most common cause of hypercarbic respiratory failure?
Coma (15%)
COPD in exacerbation (13%) Neuromuscular disease (13%)
What are the primary objectives of MV?
- decrease work of breathing
2. reverse life threatening hypoxemia and acidosis
Complications of NIV?
pneumonia
tracheolaryngeal trauma
2 most frequently implemented ways of NIV
- bilevel positive airway pressure ventilation
2. pressure support ventilation
Major limitation of NIV
patient intolerance
Most important group of patients who benefit from a trial of NIV
COPD in exacerbation Respiratory acidosis (pH <7.35)
blood pH level associated with low failure rates (15-20%) and good outcomes with NIV
7.25 - 7.35
In more severely ill patients, with blood pH <7.25, the rate of NIV failure is inversely related to the severity of the respiratory acidosis; the lower the pH the higher the rate of failure
TRUE
Good clinical indicators of the therapeutic benefit of NIV
- reduction in respiratory frequency
2. decrease in the use of accessory muscles
What characterizes a conditioned gas?
warmed, oxygenated, humidified
Good choices of sedatives during intubation but can have a deleterious effect on hemodynamics in patients with depressed cardiac function or low systemic vascular resistance
Opiates and benzodiazepines
Drug used during intubation that can promote histamine release from tissue mast cells and may worsen bronchospasm
Morphine
Drug that may increase systemic arterial pressure and has been associated with hallucinatory responses
Ketamine
Contraindications for NIV
Cardiac/ respiratory arrest Severe encephalopathy Severe GI bleed Hemodynamic instability Unstable angina or MI Facial surgery or trauma Upper airway obstruction High risk aspiration inability to clear secretions
Basic goals of MV
to optimize oxygenation while avoiding ventilator induced lung injury due to overstretch and collapse/re-recruitment
(protective ventilatory strategy)
Refers to the manner in which ventilator breaths are triggered, cycled, and limited
Mode
defines what the ventilator senses to initiate an assisted breath
Trigger
refers to the factors that determine the end of inspiration
Cycle
operator specified values that are monitored by transducer internal to the ventilator circuit throughout the respiratory cycle
Limiting factors
most widely used mode of ventilation
ACMV
patient or timer triggered
delivers an operator specified tidal volume
ACMV
Ventilatory rate is determined either by the patient or by the operator specified back up rate, whichever is of higher frequency
ACMV
allows synchronization of the ventilator cycle with the patient’s inspiratory effort
ACMV
Increased intrathoracic pressures resulting from dynamic hyperinflation occurring if there is inadequate time available for complete exhalation between inspiratory cycles
Auto-PEEP
Variable set by ACMV
TV BUR PEEP FiO2 Pressure limit
Patient triggered, flow cycled, pressure limited
Pressure support ventilation
Operator sets the pressure level to augment every spontaneous respiratory effort
PSV
Patients receive ventilator assistance only when the ventilator detects an inspiratory effort
PSV
operator sets the number of mandatory breaths of fixed volume to be delivered by the ventilator; between those breaths, the patient can breathe spontaneously
Intermittent Mandatory ventilation
If the patient fails to initiate a breath, the ventilator delivers a fixed TV breath and resets the internal timer of the next inspiratory cycle
SIMV
time triggered, time cycled, pressure limited
Pressure control ventilation
tidal volume and inspiratory flow rate are dependent and are not operator specified
PCV
preferred mode of ventilation in whom it is desirable to regulate peak airway pressures, such as those with preexisting barotrauma, and for post-thoracic surgery patients in whom the shear forces across a fresh suture line should be limited.
PCV
variant of PCV that incorporates the use of prolonged inspiratory time with the appropriate shortening of the expiratory time
Inverse ratio ventilation
used in patients with severe hypoxemic respiratory failure. increases mean distending pressures without increasing peak airway pressures.
Inverse ratio ventilation
provides fresh gas to the breathing circuit with each inspiration and sets to a constant operator specified pressure
Continuous positive airway pressure
static pressure in the airway at the end of inspiration
Plateau pressure
Preventive ventilatory strategy has decreased the mortality rate of patients with acute hypoxemic respiratory failure to how many percent?
30%
Daily interruption of sedation in patients with improved ventilatory status results in a shorter time on the ventilator and a shorter ICU stay
True
3 most common organisms causing VAP
pseudomonas aeruginosa
enteric gram neg rods
s aureus
Hypotension resulting from elevated intrathoracic pressures with decreased venous return is almost always responsive to which management?
Intravascular volume repletion
4 Conditions indicating amenability to weaning by the ventilatory weaning task force
WEAN SCREEN
(1) Resolving disease
(2) adequate gas exchange with low PEEP (<8 cmH2O) and Fio2 (<0.5)
(3) stable hemodynamics
(4) spontaneous breathing ability
How is SBT implemented?
T-piece using 1–5 cmH2O CPAP with 5–7 cmH2O
PSV
How many percent of patients require reintubation despite all precautions instituted
10-15%
3 complex complications of long term tracheostomy
tracheal stenosis
granulation
erosion of the innominate artery
Tracheostomy is planned if a patient needs MV for how many days?
> 10-14 days
How many percent of ventilated patients ultimately become dependent on vent support?
2%
When is SBT declared a failure?
- RR >35 for 5 min
- O2 sat <90%
- HR >140 or 20% inc or dec from baseline
- SBP <90 or >180
- inc anxiety/ diaphoresis
Mainstay for therapy for analgesia in MV patients
Opiates
Use of neuromuscular blocking agents may result in prolonged weakness terms as
Post paralytic syndrome
