Critical Care Flashcards
2 options for mode setting
Full support
Partial support
What do we have to set on ventilator?
- Mode
- Tidal volume
- Rate
- FiO2
- PEEP
- Sensitivity type a level
- Peak flow
- Alarms
- Insp flow waveform
- Humidification system
Tidal volume initial settings
8-12 mL/kg IBW
Tidal volume initial settings for ARDS and COPD
5-8 cc/ kg IBW
Initial vent rate settings
8-12 bpm w moderate tidal volume
Initial fio2 vent settings
Use whatever fio2 they were on when mechanical ventilation was initiated.
If on room air, use 100%
How much to wean fio2 to reduce risk of o2 toxicity?
60% or less
PEEP vent initial settings.
5 cm H2O of BP ok
2 types of sensitivity settings
Pressure
Flow
Pressure sensitivity initial vent settings
-1 to -2 cm H2O
Flow based sensitivity initial vent settings
5 L/min base flow
1-3 L/min usually triggers breath
Peak flow initial vent settings
40-60 L/min MINIMUM
Peak flow / I:E ratio relationship
Increase peak flow= increase I:E (longer time to exhale)
Decrease peak flow= decrease I:E (shorter time to exhale)
Inspiratory flow waveforms
Square (constant)
Decelerating (descending)
Accelerating (ascending)
Sine (normal breathing)
Temp of nose
20-22 C
Temp of hypo pharynx
29-32 C
Temp of trachea
32-35 C
Temp 5 cm below carina
37 C
If over 24 hrs, air needs to be
Heated!
Should avoid HME in pts w…
Thick secretions
Low body temp
High spontaneous minute ventilation (>10L/min)
Large air leaks
Normal minute ventilation
5-10 L/min
Relative humidity
A gas that has only part of the humidity it could have
Absolute humidity
Weight of humidity based on pressure
Measured in mg/L
Absolute humidity at 37C
44 mm Hg
Goals of mechanical ventilation
- Improve gas exchange
- Relieve respiratory distress
- Improve pulmonary mechanics
- Permit lung and airway healing
- Avoid complications
Impending resp failure tidal volume threshold
<3-5 mL/kg
Impending resp failure frequency and pattern threshold
> 30L/min labored or irregular
Impending vent failure minute ventilation threshold
> 10L/min
Impending vent failure vital capacity threshold
<15 mL/kg
Impending vent failure max inspiratory pressure threshold
<-20 cm H2O (ie -10cm H2O)
Impending vent failure PaCO2 trend threshold
Increasing to >50 mm Hg
Impending vent failure vital signs threshold
Inc hr
Inc BP
Severe hypoxemia thresholds for mechanical ventilation
P(A-a)O2 > 450mm Hg on 100% O2 (refractory hypoxemia)
<200 mm Hg for ARDS
*aka P/F ratio (pao2/fio2)
Reasons for prophylactic vent support
Reduce risk of pulm complications
Reduce hypoxia of major body organs
Reduce cardiopulmonary stress
Contraindications for mechanical ventilation
Absolute: untreated tension pneumothorax Relative: pt informed request Medical futility Reduction or termination of pain and Suffering Exclusion criteria for ventilator access
Initial PS level for MV
8-10
Titrated for weaning
Longer E time for pts w air trapping achieved by
Increasing flow rate Increaing E time Decreasing I time Decreasing frequency Decreasing tidal volume
Use PIFR formula to change the I:E ratio by flow
Ve= 12L/min
Desired I:E = 1:3
12 x 4 = 48 L/min. PIFR
Constant insp flow waveform
Square
Peak flow same as mean flow
Ideal for normal lungs
Accelerating insp waveform
Spending
Peak flow same as mean flow
Suitable for partial airway obstruction
Decelerating insp waveform
Descending
Higher initial pressure and flow
Flow tapers to end expiration
Improve distribution of tidal volume and gas exchange
Sine inspiratory flow wave pattern
Similar to normal breathing
Improves distribution of tidal volume and gas exchange
Maximum inspiratory pressure
Aka negative inspiratory force
Reflects a patients respiratory muscle strength
Should be -20 cm H2O
If -19 cm H29 to 0, then impending ventilatory failure
Assessments for impending ventilatory failure
Tidal volume Frequency Minute volume Vital capacity Maximum inspiratory pressure Paco2 trend Vital signs
Severe hypoxemia
Pao2 less than 60 mm Hg on 50% or more fio2
Or less than 40 mm Hg on any fio2
Common clinical manifestations of ARDS and ALI
Acute onset
Bilateral infiltrates
Normal PCWP
PCWP
Pulmonary capillary wedge pressure
Used to rule out pulmonary edema or bilateral infiltrates caused by cardio genie pulmonary edema if less than or equal to 18 mm Hg
BSA
Body surface area
What is the primary ventilator control to regulate paco2?
Frequency
Frequency/ paco2 relationship
Increase frequency if paco2 is too high, decrease frequency if paco2 is too low
Factors preventing patient from receiving set tidal volume
- Gas leakage in ventilator circuit
- Gas leakage at et tube
- Circuit compressible volume loss
Circuit compressible volume
Expansion of ventilator circuits during inspiration leading to a small lost volume of gas that does not reach the patient, but is recorded as part of the expired tidal volume.
Conditions that may require lower tidal volume
Increase airway pressure requirement (ARDS)
Increase of lung compliance (emphysema)
Decrease of lung volumes (pneumonectomy)
Corrected tidal volume
Expired tidal volume - circuit compressible volume
Extinction can be considered when…
PS level reached 5-8 cm H2O for 2 hours w no signs of resp distress
Basic ventilator alarms
Low exhaled volume Low inspiratory pressure High inspiratory pressure Apnea High frequency FiO2
Low exhaled volume alarm
Should be set at about 100 mL lower than the expired mechanical tidal volume.
Low inspiratory pressure alarm
Should be set at 10-15 cm H2O below observed peak inspiratory pressure
High inspiratory pressure alarm
Should be set at 10-15 cm H2O above the observed peak inspiratory pressure
Apnea alarm
Should be set with a 15-20 sec time delay
High frequency alarm
Should be set at 10/min over the observed frequency
Fio2 alarm
Should be set 5% -10% above and below set fio2
Hazards and complications of mechanical ventilation related to ppv
Barotrauma Hypotension Arrhythmia Oxygen toxicity Bronchi pleural fistula Bronchi pulmonary dysphasia in infants Upper gastrointestinal hemorrhage
Hazards and complications of mechanical ventilation associated w pt condition
Infection
Physical and psychological trauma
Multiple organ failure
Hazards and complications of mechanical ventilation related to equipment
Ventilator and alarm malfunction Ventilator circuit disconnection Accidental extubation Main bronchus intubation Postintubation stridor Endotracheal tube blockage Tissue damage Atelectasis
Hazards and complications of mechanical ventilation related to medical professionals
Nosocomial pneumonia
Inappropriate vent settings
Misadventures
Risk of barotrauma is high when…
PIP >50 cm H2O
Plateau pressure > 35 cm H2
mPaw >30 cm H2O
PEEP >10 cm H2O
High airway pressures are more detrimental in patients with which type of compliance?
Those with high compliance
LMA
Laryngeal mask airway
A tube with a small cushioned mask on the distal end that provides a seal over the laryngeal opening
LMA indications
When tracheal intubation is precluded by lack of experience or equipment
When attempts at endotracheal intubation have failed
Does the LMA protect pt from aspiration?
No
Which size LMA for adults?
Size 4 females
Size 5 males
Positive pressure ventilation may be provided via most LMAs at peak inspiratory pressure up to
20 cm H2O
Silicone LMAs can be used up to how many times as long as it is cleaned by what method?
40 times
Steam autoclave
Best measure of ventilatory status
PaCO2
Strategies to Improve ventilation (ie lower paco2)
Increase ventilator frequency Increase spontaneous tidal volume Increase ventilator tidal volume Reduce mechanical dead space Consider high frequency jet or oscillatory ventilation
How to determine new frequency to obtain a certain paco2
New frequency = (current frequency x current paco2) / desired paco2
Permissive hypercapnia
Intentional hypoventilation of a patient by reducing the ventilator tidal volume to a range of 4-7 mL/kg.
Used to lower pulm pressures and minimize risk of ventilator related lung injuries
Acidosis is neutralized w tromethamine
Plateau pressure should be kept at or below what to avoid pressure induced lung injuries
35 cm H2O
2 main conditions that permissive hypercapnia is used for
Status asthmaticus
ARDS
Oxygenation
Amount of oxygen available for metabolic functions
Affected by ventilation, diffusion and perfusion
Strategies to improve oxygenation
Increase fio2
Improve ventilation and reduce mechanical dead space
Improve circulation
Maintain normal hemoglobin level
Initiate continuous positive airway pressure only w adequate spontaneous ventilation (CPAP)
Consider airway pressure release ventilation (APRV)
Initiate positive end expiratory pressure (PEEP)
Consider inverse ratio ventilation (IRV)
Consider prone positioning
Consider extracorporeal membrane oxygenation (ECMO)
IRV improves oxygenation by…
Overcoming noncompliant lung tissues
Expanding collapsed alveoli
Increasing time for gas exchange
HFOV initial settings
Mean airway pressure= 5 cm h20 over vent setting Power = 4 Frequency = 5-6 Hz Insp. time= 33% F1o2= 100%
Low pressure alarm may be triggered in following cases:
Loss of circuit pressure
Loss of system pressure
Conditions leading to premature termination of inspiratory phase
Inappropriate ventilator settings
The low volume alarm is usually triggered w what alarm?
Low pressure alarm
High pressure alarm may be triggered by
Increase in airflow resistance
Decrease in lung or chest wall compliance
High frequency Alarm may be triggered by
Patients need to increase ventilation
Excessive sensitivity setting
What is the most frequent trigger of the apnea alarm.
Disconnection of the ventilator circuit from the pt’s et tube
Ways to reduce auto PEEp
Reducing tidal volume or frequency
Increasing inspiratory flow
Eliminating airflow obstruction
If an MDI is used w an HME, where must the MDI be placed?
Between the HME and the patient
The tidal volume selected for patients w Ali or ARDS should result in a plateau pressure of
<35 cm H2O
Brachial plexophathy
Decreased movement or sensation in the arm and shoulder
TGI
Tracheal gas insufflation
Use of a small catheter to provide a continuous or phasic gas flow directly into the trachea during mechanical ventilation
Weaning success
Absence of ventilatory support 48 hours following extubation
Weaning failure
Failure of spontaneous breathing trial
Or
The need for reintubation within 48 hours following extubation
Pts who faile SBT often exhibit the following clinical signs:
Tachypnea Tachycardia Hypertension Hypotension Hypoxemia Acidosis Arrhythmias
2 critical questions before attempting to wean:
- Has pt significantly recovered from the acute phase of the disease or injury that prompted the need for mechanical ventilation?
- Are there other clinical conditions that may interfere with the pt’s ability to sustain the work of spontaneously breathing?
“Clinical” weaning criteria
Resolution of acute phase of disease
Adequate cough
Absence of excessive secretions
Cardiovascular and hemodynamic stability
“Ventilatory” weaning criteria
Spontaneous breathing trial: 20-30 min
PaCo2: 10 mL/kg
Spontaneous Vt: >5 mL/kg
F/Vt: <10 L w satisfactory ABG
“Oxygenation” weaning criteria
PaO2 without PEEP: >60 mm Hg at fio2 up to .4 PaO2 w PEEP: >100 mm Hg at fio2 up to .4 Sao2: >90% at fio2 up to .4 P/F: > or = 150 mm Hg Qs/Qt: <350 mm Hg at fio2 .1
Pulmonary reserve weaning criteria
Vital capacity: >10 mL/kg
Max insp pressure: >-30 cm H2O in 20 sec
Pulmonary measurements weaning criteria
Static compliance: >30 mL/ cm H2O
Airway resistance: stable or improving
Vd/Vt: <60% while intubated
5 weaning criteria categories
Clinical Ventilatory Oxygenation Pulmonary reserve Pulmonary measurements
What are the vital capacity and tidal volume measurements that correlate w successful weaning?
10 mL/kg and 5 mL/kg respectively
