Accuracy of respiratory rate monitoring using a non-invasive acoustic method after general anaesthesia

Br J Anaesth. 2012 May;108(5):872-5. doi: 10.1093/bja/aer510. Epub 2012 Feb 8.


Background: Respiratory rate should be monitored continuously in the post-anaesthesia care unit (PACU) to avoid any delay in the detection of respiratory depression. Capnometry is the standard of care but in extubated patients requires a nasal cannula or a face mask that may be poorly tolerated or can be dislodged, leading to errors in data acquisition and false alarms. The value of a new non-invasive acoustic monitor in this setting has not been fully investigated.

Methods: Adult patients admitted to the PACU after general anaesthesia were included. After tracheal extubation, an adhesive sensor with an integrated acoustic transducer (RRa™) was placed on the patient's throat and connected to its monitor while the patient breathed through a face mask with a carbon dioxide sampling port (Capnomask™) connected to a capnometer. Both the acoustic monitor and the capnometer were connected to a computer to record one pair of data per second for up to 60 min.

Results: Fifty-two patients, mean (range) age 54 (22-84) yr and BMI 26 (19-39) kg m(-2), were studied. Compared with capnometry, the bias and limits of agreement of the acoustic method were 0 (-1.4-1.4) bpm. The acoustic sensor was well tolerated while the face mask was removed by eight patients, leading to study discontinuation in two patients.

Conclusions: In extubated patients, continuous assessment of respiration rate with an acoustic monitor correlated well with capnometry.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Airway Extubation
  • Anesthesia, General / methods*
  • Auscultation / instrumentation
  • Auscultation / methods*
  • Capnography / methods
  • Female
  • Humans
  • Male
  • Masks
  • Middle Aged
  • Monitoring, Physiologic / instrumentation
  • Monitoring, Physiologic / methods
  • Postoperative Care / instrumentation
  • Postoperative Care / methods*
  • Postoperative Complications / diagnosis
  • Prospective Studies
  • Reproducibility of Results
  • Respiratory Insufficiency / diagnosis
  • Respiratory Rate / physiology*
  • Respiratory Sounds / physiology*
  • Young Adult