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.
Sponsor:
Information provided by (Responsible Party):
Gildasio De Oliveira, Northwestern University
ClinicalTrials.gov Identifier:
NCT00954733
First received: August 5, 2009
Last updated: June 25, 2014
Last verified: June 2014
  Purpose

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
Surgery
Hypoventilation
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:
  • TcCo2 vs PACo2 Difference [ Time Frame: 1 hour ] [ Designated as safety issue: No ]
    Evaluate the correlation between PaCO2- TcCO2 in detecting hypoventilation for patients undergoing deep sedation Absolute mean difference between TcCo2 and the PA Co2


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)
Arms Assigned Interventions
Experimental: All participants
All participants, one arterial blood draw
Other: Arterial blood draw
One arterial blood draw

Detailed Description:

A group of _40 patients scheduled to undergo Hysteroscopy surgery with deep sedation will be studied. Standard monitors will be utilized. Additionally a transcutaneous CO2 electrode will be attached to the ear lobe and a BIS monitor will be applied to the forehead.

The anesthetic management will be left to the discretion of the anesthesia provider (Anesthesia resident or CRNA, under the supervision of a faculty attending anesthesiologist).All patients will receive supplemental oxygen at 3L/ minute via nasal cannula, to maintain oxygen saturation greater than 90%.

Both the end tidal CO2 (ETCO2) and transcutaneous CO2 (TcCO2) (Linde Medical Sensors, Basel , Switzerland ) will be calibrated before use, according to the manufacturer's instruction.. The anesthesia provider will be blinded to the TcCO2 monitor but will have access to the ETCO2 values. The ETCO2 and TcCO2 values will be recorded simultaneously by an independent observer.

One arterial blood samples will be collected from each subject for measurement of PaCO2 at a deep level of sedation defined by a modified Ramsey score greater or equal to 5 (1= anxious/agitated/restless; 2= cooperative/oriented/tranquil; 3= drowsy/responds to commands only; 4= brisk response to shaking/loud sound; 5= sluggish response to shaking/loud sound; 6= no response) The ETCO2 and .TcCO2 will be recorded throughout the time of obtaining the blood sample every 15 seconds and the mean value will be used for comparison. Hypoventilation will be defined as a PaCO2 level greater than 45mmHg.

Sedation score (OASS) will be recorded on admission to recovery area. Time to meet discharge criteria will be recorded.

The experimental procedures: ABG draw, ETCO2 monitor placement on the ear, 2 Ramey scale assessments.

  Eligibility

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

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
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Please refer to this study by its ClinicalTrials.gov identifier: NCT00954733

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

Publications:
Responsible Party: Gildasio De Oliveira, Principal Investigator, Northwestern University
ClinicalTrials.gov Identifier: NCT00954733     History of Changes
Other Study ID Numbers: STU00004382
Study First Received: August 5, 2009
Results First Received: June 25, 2014
Last Updated: June 25, 2014
Health Authority: United States: Institutional Review Board

Keywords provided by Northwestern University:
Hysteroscopic surgery
Hypoventilation
Co2
Transcutaneous Co2 Monitor

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

ClinicalTrials.gov processed this record on October 20, 2014