Pressure Monitoring Definitions
Zeroing
- Zeroing = a process which confirms that atmospheric pressure results in a zero reading by the measurement system
- intermittent confirmation ensures the absence of baseline drift where atmospheric pressure no longer reads zero -> resulting in aberrant results
- this is relatively common with disposable transducers
Levelling (or establishing the zero reference point)
- Levelling = the process which determines the position on the patient you wish to be considered to be zero
- transducers are placed at this point (often utilising fluid filled tubing)
- this is the level of the right atrium (midaxillary line in the supine patient)
- significant errors in measurement may occur if readings using different zero reference points are used (ie. CPP)
Calibration
- Calibration = the process of adjusting the output of a device to match a known input value
- verification of calibration requires the use of a ‘gold standard’ (ie. mercury or water manometer)
- requires a two-step procedure (confirming that zero = zero and 100mmHg = 100mmHg)
- this assesses linearity of the system
- the calibration of disposable transducers is preset and cannot be altered
Example of pressure transducer set-up
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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