2 (C) Ventilatory Support Hypercapnic Respiratory Failure Flashcards
What is hypercapnic respiratory failure?
• CO2 retention
• Failure to move enough air in and out of
alveoli
• Mode of ventilation is chosen to assist moving
air whilst minimising the detrimental effects
How does positive pressure ventilation worl
Instead of using negative pressure to draw air in, now use positive pressure to push the air in
What is controlled ventilation?
– RR set – VT set – patient effort ignored – no control – requires sedation of awake patient – limited/no respiratory muscle activity – airway pressure always positive
What is assist/control ventilation?
ACV – set ventilator rate – VT set – plus any patient p y p effort triggers ventilator breath – preset minimal rate – limited respiratory muscle activity – airway pressure always positive – risk of hyperventilation (If pt breathes, will deliver next breath when scheduled. Therefore, pt couldn't fully expire, leading to hyperventilation/hyperinflation)
What is IMV?
Intermittent Mandatory Ventilation
• IMV
– set number and size of ventilator breaths per
minute
– unlimited number of patient breaths in between,
of any volume
– risk of breath stacking
– more use of respiratory muscles than CV or ACV (but will still be deconditioned)
What is SIMV?
• SIMV
– set number and size of ventilator breaths per
minute triggered by patient effort
– unlimited number of patient breaths in between,
of any volume
– no risk of breath stacking
What can Pressure Support Ventilation be used for?
To wean a patient off ventilation
What is PSV?
Pressure Support Ventilation
• PSV
– rate set by patient (supports all of pt’s breaths w/ pressure)
– volume augmented by ventilator
– patient must make continuous inspiratory effort
– promotes more use of respiratory muscles than
SIMV
– intubated patients and by mask
(Can be given invasively and non-invasively)
What is “Bilevel”??
• Sometimes also called “Biphasic” mode
• Combination mode ‐ able to fully control ventilation
as well as allowing any spontaneous breathing effort
• Ventilator cycles between two levels of PEEP
(highPEEP and lowPEEP)
• Set times for highPEEP and lowPEEP (to give I:E ratio)
• If the patient makes no effort to breathe, this model
is similar to SIMV(P)
What does PEEP high do in Bilevel?
Inspiratory pressure
What can Bilevel be helpful for?
• This mode can be helpful for patients with poor lung
compliance and low oxygenation (eg ARDS)
• In addition, allows patient to breathe spontaneously
any time while on highPEEP or lowPEEP , muscle
disuse atrophy
• need for sedatives/paralysing drugs if better
comfort and synchronisation
What does Bilevel do if a patient breaths during a mandatory breath?
Gives much less support to the patient’s effort, lessening breath stacking
What does Bilevel do if a patient takes a breath between mandatory breaths?
Supports the breath, bigger breath with much less effort.
What is IPPB?
Intermittent Positive Pressure Breathing • IPPB* – non intubated patient not dependent on mechanical ventilation to survive – rate set by patient – volume set by ventilator – used by physiotherapists to VT – mouthpiece or mask
Modes of delivering IPPB
mouthpiece or mask
