Characterization of breathing patterns during patient-controlled opioid analgesia

Br J Anaesth. 2013 Dec;111(6):971-8. doi: 10.1093/bja/aet259. Epub 2013 Aug 21.


Background: Respiratory rate is an important measurement in patient care, but accurate measurement is often difficult. We have developed a simple non-invasive device to measure respiratory movements in clinical circumstances, with minimal interference with the patient. We investigated respiratory patterns in patients receiving postoperative morphine analgesia to assess the capacity of the device to detect abnormalities.

Methods: We studied subjects during self-administered opioid analgesia after major gynaecological surgery, and related the derived signals with a signal from a nasal cannula. Respiratory movement signals were transmitted wirelessly to a recorder from two encapsulated tri-axial accelerometer (RESpeck) sensors. We analysed the signals using two different sensor placements, each for 30 min. The nasal cannula signal was used to classify breathing patterns as obstructive or non-obstructed.

Results: We studied 20 patients for a mean duration of 49 min each. Breathing patterns were very variable, between and within patients. The median breathing rates ranged from 6.4 to 19.5 bpm. Breathing was partly obstructed in 10 patients, and six patients had repeated cycles of obstruction and transient recovery. In these patients, we found a consistent and statistically significant pattern of changes in chest wall movement, with increased abdominal and decreased rib cage movement during obstruction. In patients with slow respiratory rates, breath-to-breath times were highly variable.

Conclusions: In undisturbed subjects receiving patient-controlled morphine analgesia after surgery, abnormal breathing patterns are extremely common. Cyclical airway obstruction is frequent and associated with a typical pattern of changes in chest wall movement.

Keywords: monitoring, physiologic; respiration disorders; respiratory rate.

Publication types

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

MeSH terms

  • Accelerometry / methods
  • Adult
  • Aged
  • Airway Obstruction / chemically induced
  • Airway Obstruction / diagnosis
  • Airway Obstruction / physiopathology
  • Analgesia, Patient-Controlled / adverse effects*
  • Analgesia, Patient-Controlled / methods
  • Analgesics, Opioid / administration & dosage
  • Analgesics, Opioid / adverse effects*
  • Gynecologic Surgical Procedures
  • Humans
  • Middle Aged
  • Monitoring, Physiologic / methods
  • Movement / physiology
  • Pain, Postoperative / prevention & control*
  • Postoperative Care / methods
  • Respiration Disorders / chemically induced
  • Respiration Disorders / diagnosis*
  • Respiration Disorders / physiopathology
  • Respiratory Rate / drug effects
  • Signal Processing, Computer-Assisted
  • Thoracic Wall / physiopathology


  • Analgesics, Opioid