A Comparison of the Detection of Hypoventilation During Deep Sedation Utilizing Nasal End Title CO@ Versus Transcutaneous CO2 Measurement Techniques

This study has been completed.
Information provided by:
Northwestern University
ClinicalTrials.gov Identifier:
First received: August 5, 2009
Last updated: December 22, 2009
Last verified: December 2009

The estimation of the partial pressure of carbon dioxide (PCO2) in the arterial blood is used to judge the adequacy of ventilation during spontaneous and controlled ventilation. Although the gold standard for monitoring PCO2 remains arterial blood gas sampling, this requires an invasive procedure and provides only an intermittent estimate of what is frequently a continuously changing value. The solution to this problem has been the development and validation of accurate noninvasive monitoring techniques which provide a continuous intraoperative estimate of PCO2.The most commonly used noninvasive technique to monitor PCO2 is measurement of the end tidal CO2 (PECO2) . However, sampling errors and patient -related issues such as ventilation-perfusion mismatch, patient positioning or decreases in pulmonary blood flow may influence the accuracy of PECO2 monitoring (1-3). Nasal capnography has been proved to be an accurate monitor during the post-operative period (4) but its ability to accurately detect hypoventilation associated with deep sedation has not been studied.

According to the American Society of Anesthesiologist standards for basic monitoring, continuous capnography is required for all patients undergoing general anesthesia but it is optional for MAC/sedation cases. The need for CO2 monitoring has been studied by other medical specialties that use procedural sedation, including gastroenterology (12) and emergency medicine (13, 14) and many specialties now recommend capnography as a standard monitor.

Patients receiving supplemental oxygen may experience significant persistent hypoventilation leading to progressive hypercarbia and acidosis which may go undetected for a significant time interval since the routinely monitored SpO2 may be maintained within normal range. A recent study has shown that despite the fact that end tidal CO2 is reliable in detecting apnea , increasing oxygen flow rates decrease the amplitude of measured CO2, probably via dilution, making the quantitative value less reliable as an assessment of adequacy of ventilation (15). Furthermore, during hypoventilation there is reduced alveolar ventilation and the end tidal CO2 is not a true reflection of arterial CO2.

Transcutaneous measurement of PCO2(PtcCO2) is a non-invasive method of measuring PCO2 that has been used much less frequently due to technical difficulties with earlier transcutaneous electrodes. Preliminary studies of the reliability of the current PtcCO2 electrodes (TOSCA, Linde Medical Sensors, and Basel, Switzerland) have shown good correlation of arterial and transcutaneous measurements in both adult volunteers and anesthetized subjects (5). PtcCO2 is measured with a sensor attached by a low pressure clip to an earlobe. The sensor probe heats the earlobe to 42 degrees Celsius to enhance blood flow. The current sensors have also been evaluated in anesthetized children (7, 8), anesthetized adults (9, 10) and critically ill neonates (11) and all these studies revealed a good correlation between PtCO2 and PaCO2.

Condition Intervention
Hysteroscopic Surgery
Other: Arterial blood draw

Study Type: Interventional
Study Design: Allocation: Non-Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Single Group Assignment
Masking: Open Label
Primary Purpose: Diagnostic
Official Title: A Comparison of the Detection of Hypoventilation During Deep Sedation Utilizing Nasal End Title CO@ Versus Transcutaneous CO2 Measurement Techniques

Resource links provided by NLM:

Further study details as provided by Northwestern University:

Primary Outcome Measures:
  • Evaluate the correlation between PaCO2 - ETCO2 versus PaCO2- TcCO2 in detecting hypoventilation for patients undergoing deep sedation [ Time Frame: 1 hour ] [ Designated as safety issue: Yes ]

Secondary Outcome Measures:
  • Subjects with SaO2 less than 90% on 3L oxygen by nasal cannula. Subjects requiring airway supporting measures; jaw support, oral / nasal airway. Subjects converted to general anesthesia due to inadequacy of deep sedation [ Time Frame: 1 hour ] [ Designated as safety issue: Yes ]

Enrollment: 40
Study Start Date: June 2009
Study Completion Date: August 2009
Primary Completion Date: August 2009 (Final data collection date for primary outcome measure)
Intervention Details:
    Other: Arterial blood draw
    One arterial blood draw

Ages Eligible for Study:   18 Years and older
Genders Eligible for Study:   Female
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Age>18 years of age
  • Sex: Non-pregnant, Female
  • ASA PS: I, II
  • Surgery: Elective Hysteroscopy surgery
  • Consent: Obtained

Exclusion Criteria:

  • Age < 18 years old
  • Patients who refuses participation
  • History of lung disease
  • History of Obstructive sleep apnea
  Contacts and Locations
Please refer to this study by its ClinicalTrials.gov identifier: NCT00954733

United States, Illinois
Northwestern University
Chicago, Illinois, United States, 60611
Sponsors and Collaborators
Northwestern University
Study Director: Robert McCarthy, PharmD Northwestern University
  More Information

Responsible Party: Gildasio De Oliveira, M.D., Department of Anesthesiology, Feinberg School of Medicine,Northwestern University
ClinicalTrials.gov Identifier: NCT00954733     History of Changes
Other Study ID Numbers: STU00004382
Study First Received: August 5, 2009
Last Updated: December 22, 2009
Health Authority: United States: Institutional Review Board

Keywords provided by Northwestern University:
Hysteroscopic surgery
Transcutaneous Co2 Monitor

Additional relevant MeSH terms:
Respiratory Insufficiency
Respiration Disorders
Respiratory Tract Diseases
Signs and Symptoms, Respiratory
Signs and Symptoms

ClinicalTrials.gov processed this record on April 17, 2014