Respiratory Rate: The Hidden Vital Sign

Capturing a patient’s respiratory rate — as an important vital sign — is a process that varies significantly across hospitals throughout the country. Undervalued at times, respiratory rate is a vital sign that is usually not measured by in-room medical devices, but instead is assessed and documented subjectively — if even documented at all.1-2 Just as clinicians capture blood pressure and body temperature to inform on patient treatment decisions, respiratory rate, too, should be an inclusive metric to enhance patient outcomes.

Traditional methods of assessing respiratory rate include counting the visual breaths of a patient or through electrocardiography (ECG) impedance, which is typical in an intensive care unit (ICU) setting. The counting method occurs more frequently in the general care floor where patient’s vital signs are ‘spot checked’ rather than continuously monitored. Those vital signs are then recorded in the chart at certain time intervals throughout the day. There are problems with this method of respiratory rate measurement including:

  • A greater risk for human error with subjective capture of vital signs.1-2
  • Spot checking respiratory rate values only captures a momentary snapshot of a patient’s condition.1-2

For example, a clinician counts a patient’s respiratory rate of 19 breaths per minute at 11:14am, but at 11:42am the patients breathing has increased to 26 breaths per minute. And at 11:59am the patient starts breathing 32 times a minute and subsequently experiences a respiratory event. If the patient’s respiratory rate had been monitored continuously and objectively vs. subjectively, the change in the patient’s condition may have been caught much earlier and possibly prevented from escalating. In 1993, Fieselmann and colleagues reported that a respiratory rate higher than 27 breaths/minute was the most important predictor of cardiac arrest in hospital wards.3

Capturing an early indication of increases in respiratory rate, as described in the example above may help clinicians predict adverse patient effects such as cardiac arrest in hospital wards.3

Capnography solves for inconsistent respiratory rate monitoring

Using capnography supports clinicians’ evaluation of respiratory rate as a vital sign, turning a subjective value into an objective value. Capnography is typically used for the measurement of a patient’s end-tidal carbon dioxide (etCO2) but may also add value with an accurate objective respiratory rate measurement. Capnography is an accepted reference standard measurement and more accurate in continuously monitoring respiratory rate.4-7

Additionally, capnography is an indicator of adequate ventilation and complements pulse oximetry measurements. Considered a valuable tool, pulse oximetry is not without its limitations as it only looks at the oxygenation portion of the breathing cycle.

The key advantage of capturing respiratory rate with capnography is that it measures ventilation directly at the airway. Ventilation is the process of inhalation of oxygen from the atmosphere into the lungs, gas exchange occurring at the alveoli, resulting in carbon dioxide (CO2) gas, which is expelled during exhalation. Continuous monitoring of CO2-derived respiratory rate and etCO2 are essential to help detect life-threatening conditions.8 Capnography continuously delivers both of these values to clinicians in an accurate and objective manner.4-7

Post-extubation patients in the ICU may also benefit from capnography with an increased accuracy of respiratory rate measurement. In patients receiving supplemental oxygen, pulse oximetry can be a later indicator of alveolar hypoventilation. Pulse oximetry and capnography combined work together to monitor the patient following extubation.9, 10

Related: Learn more about limitations of pulse oximetry.

Respiratory rate monitoring tools further support clinician care of growing patient population

As hospitals reach capacity in many locations across the country, the Society of Critical Care Medicine has issued new guidance to help clinicians improve survival rates of patients diagnosed with sepsis during their hospital care.11 Encompassing various screening symptoms for the classification and treatment of COVID-19 patients, one symptom is a patient’s increasing respiratory rate. Capnography promotes continuous monitoring of respiratory rate, including trends and indicators of increasing respiration rates.12

Demands on clinicians continue to increase from the influx of patients requiring ventilation and respiratory therapy during the pandemic. Adding capnography monitoring as an early alert to trends and evolving respiratory problems may help with patient management. Vital Sync™ remote monitoring coupled with Microstream™ capnography further supports general care floor patient monitoring away from the bedside. We are here for you, so you can be there for them.

Related: Read how an enhanced respiratory monitoring solution with capnography is designed to help keep you and your patients safe during the COVID-19 pandemic.

1. Karlen W, Gan H, Chiu M, et al. Improving the accuracy and efficiency of respiratory rate measurements in children using mobile devices [published correction appears in PLoS One. 2015;10(2):e0118260]. PLoS One. 2014;9(6):e99266. Published 2014 Jun 11. doi:10.1371/journal.pone.0099266
2. Philip KE, Pack E, Cambiano V, Rollmann H, Weil S, O'Beirne J. The accuracy of respiratory rate assessment by doctors in a London teaching hospital: a cross-sectional study. J Clin Monit Comput. 2015;29(4):455-460. doi:10.1007/s10877-014-9621-3
3. Fieselmann JF, Hendryx MS, Helms CM, et al. Respiratory rate predicts cardiopulmonary arrest for internal medicine patients. J Gen Intern Med. 1993; 8: 354-360.
4. Autet L, Frasca D, Pinsard M, Cancel A, Rousseau L, Debaene B, Mimoz O. Evaluation of acoustic respiration rate monitoring after extubation in intensive care unit patients. Br J Anaesth. 2014; 113 195–7.
5. Frasca D, Geraud L, Charriere J M, Debaene B and Mimoz O. Comparison of acoustic and impedance methods with mask capnometry to assess respiration rate in obese patients recovering from general anaesthesia. Anaesthesia. 2015; 70 26–31.
6. Bergese S D, Mestek M L, Kelley S D, McIntyre R Jr, Uribe A A, Sethi R, Watson JN, Addison PS. Multicenter study validating accuracy of a continuous respiratory rate measurement derived from pulse oximetry: a comparison with capnography. Anesth. Analg. 2017; 124 1153–9.
7. Ermer S, Brewer L, Kuck K, Orr J. Detecting low respiratory rates using myriad, low-cost sensors. Spacegrant. 2017; 8.
8. Microstream™ Sampling Lines Product Specification.
9. Weinger MB. Dangers of postoperative opioids. APSF Newsletter. 2006; 21: 61–88.
10. Fu ES, Downs JB, Schweiger JW, Miguel RV, Smith RA. Supplemental oxygen impairs detection of hypoventilation by pulse oximetry. Chest. 2004; 126: 1552–8.
11. Alhazzani W, et al. Surviving Sepsis Campaign: Guidelines on the Management of Critically Ill Adults with Coronavirus Disease 2019 (COVID-19). Critical Care Medicine. 2020; 48(6).
12. Cretikos MA, Bellomo R, Hillman K, Chen J, Finfer S, Flabouris A. Respiratory rate: the neglected vital sign. Medical Journal of Australia. 2008;188(11):657-659.

The recommendations of using Microstream, Nellcor, and Vital Sync in the management of COVID-19 are not cleared by FDA. This labeling has been introduced into the US market through enforcement discretion leveraging FDA guidelines supporting the COVID-19 public health emergency and this pathway can only be utilized for the duration of the emergency. These devices are considered adjunctive technology and should not be solely or primarily relied upon to prevent, diagnose, or treat COVID-19 or co-existing conditions.

About the Author

Jamie Hallahan RN, BSN, PHRN, CCRN is a clinical product specialist for Medtronic’s Respiratory and Monitoring Solutions portfolio. Her experiences as a critical care nurse both inside intensive care units as well as in the critical care transport community help her bring practical applications of Microstream™ capnography to her customers.

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