14. Mechanical Ventilation Flashcards
Endotracheal Tube Placement
-Confirmation of correct placement is done immediately after intubation.
-Waveform capnography is most accurate. -End-tidal CO2 detector -Auscultation
-Cuff inflation to 20 cm H2O pressure
-Obtain a chest XR for placement confirmation: should be 3 - 5 cm ABOVE the CARINA.
-Assess and document tube placement at the level of the teeth or gum line for an ongoing assessment of correct placement.
-If the tube migrates down, it most often migrates to the right lung due to the anatomy of the mainstay bronchi (Right is shorter/wider, with less of an angle, than the left).
-Get ABGs within 20 to 30 min of intubation to assess acid-base status.
-The ETT:
-is narrow and increases airway resistance, similar to
breathing thru a straw.
-is longer than a tracheostomy tube; therefore, it has
a greater degree of dead space ventilation than a
tracheostomy tube.
Ventilator Management:
-Ventilator breaths may be delivered at a set volume (most common for adults) or at a set pressure
-The main focus of the exam is how the ventilator settings may differ depending upon the pt’s primary problem (e.g., ARDS or asthma); nontraditional modes of ventilation are not covered on exam
Ventilator Modes:
-Assist-control (AC) mode
-Synchronized intermittent mandatory ventilation (SIMV)
Assist-contol (AC) mode
-The pt receives a SET TIDAL VOLUME at the set breath rate; the pt also receives the SET TIDAL VOLUME for each breath triggered by the pt’s spontaneous effort made above the set breath rate.
-For example, if the AC is set at a rate of 12 breaths/min, at a tidal volume of 700 mL, and the pt’s total rate per minute is 20, the tidal value of the 8 extra breaths initiated by the pt is 700 mL bc the extra breaths are sensed by the machine and the set tidal volume (700 mL) is given.
-All breaths are machine breaths
-Provides full ventilatory support
-Not used as a weaning mode unless it is being alternated with periods of spontaneous breathing)
-can result in overventilation and/or hyperinflation of the lungs at higher spontaneous breathing rates
Synchronized intermittent mandatory ventilation (SIMV) mode
The pt receives the set tidal volume at the set breath rate, and all breaths above the set rate are spontaneous breaths at the pt’s own tidal volume.
- For example, if the SIMV is set at a rate of 12 breaths/min, at a tidal volume of 700 mL, and the pt’s total rate per minute is 20, the tidal volume of the 8 extra breaths will vary from breath to breath bc the breaths that are spontaneously initiated by the pt are at the pt’s own tidal volume.
-All machine breaths are synchronized with the pt’s breathing effort
-provides full or partial ventilatory support
-reducing the SIMV rate will allow the pt to assume more of the work of breathing
-spontaneous breaths may be pressure supported
Ventilator Settings:
-PEEP (positive end-expiratory pressure)
-Continuous positive airway pressure (CPAP)
-Pressure Support Ventilation (PSV)
-Breath Rate
-Tidal Volume (Vt)
-Fraction of Inspired Oxygen (FiO2)
PEEP
Positive End-Expiratory Pressure
-positive pressure is applied to the airways at the end of exhalation
-increases lung volume at the end of exhalation (FRC), creating more surface area for gas exchange; increases alveolar recruitment.
-Can be applied to pts via artificial airways, full face mask, nasal mask, and nasal prongs (neonates)
-Think oxygenation!
CPAP
Continuous Positive Airway Pressure (CPAP)
-CPAP is PEEP applied to a spontaneously breathing pt.
-The pt does not receive machine breaths.
-The pt assumes all the work of breathing.
-Usually the last step in the weaning process.
-All breaths may be pressure supported.
-The pt may experience fatigue if left on CPAP for an extended period of time.
PSV
Pressure support Ventilation:
-The pt receives an increase in airway pressure during inspiration to augment (boost) the spontaneous tidal volume
-Patient-triggered mode (if the pt is paralyzed &/or sedated, PSV will not be triggered on)
-Rate, tidal volume, inspiratory flow rate, and inspiratory time are determined by the pt’s effort.
-You cannot use PSV with assist-control mode
-PSV is frequently used during weaning to REDUCE THE WORK OF BREATHING and to overcome imposed work of ETT and ventilator circuit.
Breath Rate
The breath rate is determine by the PaCO2, generally 12 - 16 breaths/min on full ventilator support.
Tidal Volume (Vt)
-The tidal volume (Vt) is determined by the pt’s ideal body weight and medical problem.
-Generally, the Vt is 6 -8 mL/kg
-For ARDS, in order to prevent “volutrauma” it is 5 - 6 mL/kg
FiO2
Fraction of Inspired Oxygen
-The fraction of inspired oxygen is generally set at 100% on intubation and is then adjusted down according to the PaO2; the goal is to decrease it to 50% or less as soon as you are able to.
Ventilator alarms
set for pt safety
Cause of High-Pressure Limit Alarms
-Agitation
-Coughing
-Secretions
-Aspiration
-Kinked/occluded ETT or ventilator circuit
-bronchospasm or mucosal edema
-decreasing lung compliance (ARDS)
-penumothorax
Cause of low-pressure limit alarms
-Ventilator circuit disconnection or leak
-inadequate tidal volume
-cuff leak
-chest tube leak
