Alaris® EtCO2 module
Topic 6: Responding to Abnormal Waveforms

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Abnormal Waveform: *Hypoventilation

Case: Mr. Johnson is on continuous morphine PCA. Two hours after initiating his PCA, his RR to 8 breaths/minute and his EtCO2 from 38 to 53 mmHg. (normal EtCO2 35-45 mmHg)

Clinical Findings & Abnormal Waveform1-3:

  • RR, tidal volumes relatively normal
  • EtCO2 because fewer breaths allowing more CO2 to build up in the lungs

Possible Causes1-3:

  • Over medication/increased sedation
  • Snoring or possible obstruction

Possible Responses1-3: Follow hospital protocols, which may include:

  • Assess ABC's (Airway, Breathing, Circulation)
  • Assess sedation level
  • Stimulate patient
  • Notify Respiratory Therapy and/or M.D.

1Capnography in the Management of the Critically Ill Patient, EducationPAK for Critical Care and Procedural Sedation - A Guide to Capnography. CD-ROM - Needham, MA. Oridion Medical. 2003.
2AACN Procedure Manual for Critical Care 4th Ed. (2001). Ed. Lynn-McHale, D.J. & Carlson, K.K.. American Association of Critical Care Nurses.
3Thalan's Critical Care Nursing Diagnosis and Management 4th Ed. (2001). Ed. Urden, L.D.; Stacy, K.M.; & Lough, M.E. C.V. Mosby

*The following are examples of common EtCO2 waveforms. The waveform trends are examples only and do not represent all potential abnormal waveforms. Analysis of these waveform trends may provide an early indication of the noted possible causes. The associated possible responses are suggestions only and are not meant to replace current clinical practice or hospital protocols. Always consult hospital protocols. Abnormal waveforms are not always associated with alarms.