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Can Respiratory Rates Indicate Pain?

June 13, 2014
New study finds elevated respiratory rates in unconscious patients may indicate pain.

Do unconscious patients experience pain? And if so, how does one measure pain in a non-responsive patient? According to Canadian researchers, respiratory rates (RR) of traumatic brain injury (TBI) patients may be one vital sign used to monitor pain levels in conscious and unconscious patients in the intensive care unit.

Reporting in the journal Pain Research and Treatment, Caroline Arbour of the McGill University’s Ingram School of Nursing in Montreal, Quebec, and fellow researchers stated that the most significant fluctuations in TBI patients’ vital signs occurred in their RR levels.1 Noticeable changes in intracranial pressure were also found, but further research will be needed to validate the study findings.

Arbour and colleagues noted that numerous studies have examined the vital signs of patients in critical care with TBI, but those studies were inconclusive in large part because of the problems with the study methodologies. For example, previous studies only took one sampling of vital signs instead of gathering data over a period of time. Other attempts at examining vital signs failed because of the lack of patients with varying levels of consciousness (LOC) and no accounting for the severity of the patients’ TBI, its localization, or the type and amount of analgesic and sedative therapeutic regimens.

To avoid these shortcomings, Arbour and colleagues used a sample of TBI patients in an intensive care unit at a trauma center in Montreal, recording the different characteristics of the patients including their level of consciousness, the severity of their TBI, the localization of TBI, as well as other factors like whether they were on a breathing machine and what drugs they had been administered.

The researchers then observed the patients during two common procedures done for TBI patients: noninvasive blood pressure with cuff inflation (NIBP), a standard non-nociceptive procedure, and turning the patient, considered a nociceptive procedure. The researchers looked at vital sign data taken at different intervals of the procedures, including one minute before the procedure (serving as the baseline), and then during the procedure and fifteen minutes after its completion.

State of Conscious Studied

While other tests failed to take into consideration that TBI patients can have differing LOC’s, this new study used patients with varying cognitive states and took specific notice of any changes in the patients’ LOC by using measurement with the Glasgow Coma Scale (GCS). The also sampled a wide variety of vital signs during their tests, collecting data on the patients’ systolic and diastolic pressures, mean arterial pressure (MAP), capillary saturation (Sp02), heart rates (HR), respiratory rates (RR), end-tidal CO2 levels, and if possible, their intracranial pressure (ICP). Conscious patients also reported their pain levels using a 1 to 10 point pain scale and a faces pain thermometer (FPT).

The study data gathered from the two separate trials yielded some curious results. HR, RR, and ICP levels were the only vital signs that changed significantly during the nociceptive procedure (turning the patient), but even this data was somewhat puzzling. For instance, while RR spiked dramatically during the first trial’s conscious patients during the nociceptive procedure, there were virtually no noticeable changes in vital signs for similar LOC patients in the second trial during the turning procedure.

The issue of vital sign analysis for TBI patients is still open for further trials, Arbour and colleagues said. The problem is that while vital signs fluctuated noticeably in their patients, these fluctuations could be easily explained as being natural physiological responses to the procedures themselves and not necessarily an indicator of a biological reaction to pain.

However, the researchers believe that the data they observed in RR shows evidence that this may be an important indicator of pain, as it showed the most significant and consistent results during their trials. This data, although, left many questions unanswered. Their results seemed dependent on patients’ LOC, as they didn’t find RR fluctuations in unconscious patients, which contrasted the results of previous studies that Arbour and colleagues had tried.2,3 Also, RR weren’t fluctuating for conscious patients in the second trial.

Emotional states, various other nociceptive and non-nociceptive procedures, and opioid medications can also play a role in affecting vital signs, suggesting that more research is needed to determine if RR can truly be a vital sign indicator of pain.

Last updated on: May 19, 2015