17.1. Outline four (4) causes for the capnograph trace (shown below) obtained from a critically ill patient.
17.2. Examine the data provided from a co-oximeter and a simultaneous pulse oximeter recording from patient A and B. List three (3) causes in each patient for the discrepancy between the two oximeters.
17.3. The figure below illustrates an airway pressure waveform of a single breath during volume controlled ventilation, incorporating an end inspiratory pause and an auto- PEEP manoeuvre.
X Axis – Time in seconds
Y axis – Airway pressure in cm water
- (a) What are the factors which determine variable B?
- (b) If the delivered tidal volume was 500 ml, what is the calculated compliance?
- (c) List the change(s) you would make to the ventilator settings to treat an increase in the value of variable D.
Answer and interpretation
Outline four (4) causes for the capnograph trace (shown below) obtained from a critically ill patient.
- a) Ventilator disconnection
- b) Esophageal intubation
- c) Cardiac/respiratory arrest
- d) Apnoea test in a brain dead patient
- e) Capnograph obstruction
17.2. Patients A and B
- Met Hb
- Radiofrequency interference
- Tricuspid regurgitation
- Ambient light
- Poor peripheral perfusion
- Dyes- Methylene blue
- Poor probe contact
17.3. (a) What are the factors which determine variable B?
- Resistance, compliance, tidal volume, PEEP, insp flow rate and flow pattern
17.3. (b) If the delivered tidal volume was 500 ml, what is the calculated compliance?
- 25 ml/cm water [TV/(Plateau-PEEP)]
17.3. (c) List the change(s) you would make to the ventilator settings to treat an increase in the value of variable D.
- Increase expiratory time
- Decrease I:E ratio, decrease RR, reducing MV
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.