Morning Report: ETCO2 - Capnography

ETCO2 – Capnography

Technology

-Infrared spectroscopy, CO2 absorbs specific wavelength

-Micro sampling vs in line spectroscopy

Physiology

-Aerobic cell metabolism produces CO2

-CO2 diffused easily across alveoli and exhaled

-CO2 partial pressure measured

-Small difference between arterial CO2 and ETCO2; ETCO2 usually 2-5 mmHg lower

Normal values CO2

ETCO2 and ABG similar: 35-45 mmHg

Venous: 38-52 mmHg

Uses:

-Intubation confirmation

-Critical patient monitoring

-Evaluating obstructive airway disease

-Procedural Sedcation

-Detects hypoventilation earlier

-Allows supplemental O2 administration

Waugh et al: meta-analysis reported improved diagnostic performance with capnography. In the meta-analysis, capnography was 17.6 (95% conﬁdence interval [CI] 2.5 to 122) times more likely to detect respiratory depression than standard monitoring alone.

-Assessment of CPR and cardiac death

After 20 minutes of advanced cardiac life support, end-tidal carbon dioxide was 4.4mm Hg in nonsurvivors and 32.8 mm Hg in survivors A 20-minute end-tidal carbon cioxide value of 10 mm Hg or less successfully discriminated between the 35 patients who survived to hospital admission and the 115 nonsurvivors.

AHA 2010 guidelines: It is reasonable to consider using quantitative waveform capnography in intubated patients to monitor CPR quality, optimize chest compressions, and detect ROSC during chest compressions or when rhythm check reveals an organized rhythm (Class IIb, LOE C). If PETCO₂ is <10 mm Hg, it is reasonable to consider trying to improve CPR quality by optimizing chest compression parameters (Class IIb, LOE C).

Here’s Dr. Alsup with today’s Morning Report!

References:

Capnography. Emerg Med Clin N Am 26 (2008) 881–897
Life in the fast lane
2010 AHA guidelines
Robert L. Levine. End-Tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest. N Engl J Med 1997; 337:301-306