ARDS and Ventilation Flashcards
What is the new global definition of ARDS 2023? How does it differ from the Berlin 2013 defiintion
NB is “objective assessment” incorporated to exclude cardiogenic odema and iatrogenic intravascular overload
What is the ARDS New Global Definition 2023
Additions are
1. Lung ultrasound by trained personal to diagnosed infiltrates (as an alternative to the use of CXR/CTChest)
- PF ratio < 300 in the presence of PEEP > 5 OR HFNO2 > 30l/min
- The addition of an SF ratio < 315 instead of a PF ratio is valid.
NB is “objective assessment” incorporated to exclude cardiogenic odema and iatrogenic intravascular overload.
Name the trial that defined the Berlin 2013 ARDS definition
Acute respiratory distress syndrome: the Berlin Definition
Ranieri et al 2013
Name the Research that defined the ARDS New Global Definition 2023
ARDS A New Global Definition
Matthay et al 2023
Categorize the severity of ARDS and include the relative mortality
Mild PF 200 to 300 (27%)
Moderate PF 100 to 200 (32%)
Severe PF < 100 (45%)
Mortality in parenthesis was determined with all patients on a PEEP of 5+
Summarise the pathophysiology of ARDS
Injury to the body –> inflammatory process
Disruption alveolar-capillary membrane
What does the flow trigger do on the ventilator
Causes the ventilator to cycle back to inspiration
What is peak inspiratory pressure
Pressure recorded at end inspiration
Dependent on volume or pressure delivered and airway resistance
Define plateau pressure
Static transalveolar pressure at end inspiration during an inspiratory hold for an assisted breath
Define PEEP
Positive end expiratory pressure
Pressure applied to the expiratory phase of a mechanical breath
What is extrinsic PEEP and Intrinsic PEEP
Extrinsic PEEP - PEEP applied through a mechanical ventilator
Intrinsic PEEP (Auto-PEEP) - PEEP that is secondary to incomplete exhalation (airtrapping) e.g. asthma and COPD
Compare CPAP and BIPAP
CPAP - Continuous Positive Airway Pressure
Positive pressure applied to both inspiration and expiration during spontaneous breathing in an awake and alert patient.
- no cycling of ventilator
- patient initiates all breaths
BIPAP - Bilevel Positive Airway Pressure
Awake patient who is breathing spontaneously
Ventilator alternates between higher inspiratory pressure (IPAP), augmenting patients own respiratory effort, and lower expiratory pressure (EPAP)
analogous to CPAP/PEEP
What are the different types of ventilation
Volume cycled - inspiration ends when preset Vt is delivered
Pressure cycled - inspiration ends when preset pressure has been delivered
Time cycled - inspiration ends when inspiratory time has elapsed
Flow cycled - Inspiration ends when a preset inspiratory flow is reached
Differentiate Volume controlled: CMV, A/C, IMV and SIMV modes of ventilation
CMV - Preset Vt. Fixed machine rate. Cannot be increased by patient. No spontaneous breathing by patient (Theatre only - patient paralysed)
A/C - Preset Vt. Pt can increase machine rate by triggering additional breaths.
IMV - Preset Vt. Fixed machine rate. Spontaneous breathing in between allowed. Stacking possible - machine breath on patient breath.
SIMV - Preset Vt. Fixed machine rate.
Spontaneous breathing in between allowed. Machine breaths only administered after patient exhalation complete (prevents stacking).
Differentiate Pressure controlled: PSV, PCV, APRV/BIPAP, Volume targeted pressure control
PSV - Pt rate. Machine supports until set pressure. Vt determined by pressure set and lung compliance
PCV - Fixed machine rate. Vt determined by pressure set and compliance of lungs.
APRV - Airway Pressure Release Ventilation. The machine delivers intermittent positive pressure, the rate and duration of which can be set. The patient can breath spontaneously at the lower and high level of pressure.
Volume targeted pressure control - Flow varies but volume is delivered at lowest possible pressure.
