Respiratory Rate and Why SpO2 is Not the Same Thing 2

Part of my role last year, was to pilot and Early Warning and Recognition System (EWARS) into our hospital. This chart and accompanying escalation protocol was often referred to somewhat derisively as a ‘track n trigger obs chart’. This, and the use of the term ‘dummy’ when alluding to a $120,000 patient simulator mannequin, are two of the more irritating understatements I hear on a regular basis. Ranting aside, the process of implementing this system, lead me into a voyage of discovery of the attitudes and thoughts of many nurses with respect to the humble respiratory rate.

I must first issue a disclaimer. As a novice nurse, I was definitely guilty of the odd instance of satellite observation with respect to respiratory rate (shame still racks my sleepless nights). I can trace this distasteful practice back to my first practical placement, when a preceptor said something along the lines of:

Oh they’re talking, their resp rate is about 16, just put down 16.

Reflecting back on this, I recall many instances in which I was prompted by my early mentors, that a cursory glance could yield a respiratory rate that reliably sat at 16-20 breaths/min (a range that is neither accurately obtained, nor physiologically normal). An interesting addition to this practice is the dogmatic fervour with which ‘accurate sats’ were pursued. As I progressed through my early years and learned more of the concept of evidence based practice, I realised that ‘sats’ or more correctly ‘SpO2’ was not a surrogate for respiratory rate. SpO2 is really only a superficial view as to the oxygen carrying status of the patient and offers little insight into the sinister metabolic processes at play, into which accurate measurement of respiratory rate provides a premonition of badness to come. This was a concept that I was able to draw back on the metabolic biochemistry I studied in my exercise science degree, having laboured the concepts of buffering and respiratory offset for metabolic acidosis.

I went exploring for a baseline of observation behaviour, before implementing a new system to fail on the back of old habits. Conducting some brief and repeated spot experiments (veiled as inservice teaching), I asked six nurses to go and each grab a random bedside char (n=6)t. I then asked the staff what they predicted the respiratory rates of these patients would be, before opening the charts. This was met with a couple of knowing smiles, a couple of darting eyes and a couple of bewildered grads thinkingI was a magician. To little surprise we uncovered serial observations of 16-20 breaths per minute, which when correlated to actual one minute counts on the same patients, lacked statistical power. A curious variable, however, was that a couple of patients from our sample group (n=2) admitted with a primary diagnosis of respiratory illness had well represented respiratory rates, completed with frequency and accuracy and variability. An obvious link between respiration and ventilation.

So why does this phenomenon occur? Is it simply the territory of the ward nurse, pushed for time and lacking assessment skills? (No, see references for how this is done poorly in ED and Triage too). The insight provided from the accuracy of the respiratory rates in the ‘respiratory patients’ was useful, suggestive and a source of great relief. The hint of ignorance as to the metabolic effects on respiratory rates and the pre-emptive power, was reassuring as the alternative explanation for poor observation accuracy was negligence. With the independent predictive power of rises in respiratory rate in terms of forthcoming cardiac arrest, it was (excuse the pun) vital to up-skill in this area. The primary knowledge deficit lay in the concepts of cellular respiration.

In attempts to simplify the complexities of respiratory rate changes and how they signify poor tissue perfusion I drew on what all good Australian blokes would… sporting analogy. The burn in the legs of lactic acid when going for a run (or walking up some flights of stairs depending on the fitness level of the audience). This crude overview of acidosis and it’s relationship to stress an oxygen deprivation is really easy to grasp and hence saw rapid uptake on improvement in accurate resp rate recording and this was sustained with post implementation audits. Below is my very crude explanation of cellular respiration.

Some Great Papers:

Cretikos et al (2008) ‘Respiratory Rate: The Neglected Vital Sign https://www.mja.com.au/journal/2008/188/11/respiratory-rate-neglected-vital-sign – Must Read.

Parks (2011) ‘Rate of Respiration: The Forgotten Vital Sign – this happens in ED.

Lovett et al (2005) ‘The Vexatious Vital: Neither Clinical Measurements by Nurses nor an Electronic Monitor Provides Accurate Measurements of Respiratory Rates in Triage – Triage too.