Investigators from Cleveland, Ohio, USA, studied early respiratory depression during therapeutic upper endoscopy.
They assessed the frequency of abnormal ventilatory activity during this procedure.
They also evaluated the sensitivity of observation and pulse oximetry in the detection of apnea or disordered respiration
Furthermore, they investigated whether capnography (the detection of exhaled carbon dioxide) provides an improvement over accepted monitoring techniques.
A total of 49 patients undergoing therapeutic upper endoscopy were included in the study.
Each was monitored with standard methods, including pulse oximetry, automated blood pressure measurement, and visual assessment.
In addition, graphic assessment of respiratory activity with sidestream capnography was performed in all patients.
The endoscopy personnel were blinded to capnography data.
Endoscopy personnel documented episodes of apnea or disordered respiration detected by capnography. These were compared with the occurrence of hypoxemia, hypercapnea, hypotension, and the recognition of abnormal respiratory activity.
Comparison of simultaneous respiratory rate measurements obtained by capnography and by auscultation with a pretracheal stethoscope verified that capnography was an excellent indicator of respiratory rate, when compared with the reference standard (auscultation).
Some 54 episodes of apnea or disordered respiration occurred in 28 patients (mean duration 71 seconds).
| Only 50% of apnea episodes detected by pulse oximetry.
| Gastrointestinal Endoscopy |
The researchers found that only 50% of apnea or disordered respiration episodes were eventually detected by pulse oximetry.
None were detected by visual assessment.
Dr John J. Vargo, of the Cleveland Clinic Foundation, said on behalf of fellow authors, "Apnea/disordered respiration occurs commonly during therapeutic upper endoscopy and frequently precedes the development of hypoxemia."
"Potentially important abnormalities in respiratory activity are undetected with pulse oximetry and visual assessment," he concluded.