Original Article

Journal of Anesthesia

, Volume 23, Issue 2, pp 198-202

Transcutaneous \( P_{CO_2 } \) monitors are more accurate than end-tidal \( P_{CO_2 } \) monitors

  • Makihiko HirabayashiAffiliated withDepartment of Anesthesiology, The Jikei University School of MedicineDepartment of Anesthesiology, Atsugi Municipal Hospital
  • , Chieko FujiwaraAffiliated withDepartment of Anesthesiology, The Jikei University School of Medicine
  • , Norimasa OhtaniAffiliated withDepartment of Anesthesiology, The Jikei University School of Medicine
  • , Sohei KagawaAffiliated withDepartment of Anesthesiology, The Jikei University School of MedicineDepartment of Anesthesiology, Atsugi Municipal Hospital
  • , Masayuki KamideAffiliated withDepartment of Anesthesiology, The Jikei University School of MedicineDepartment of Anesthesiology, Atsugi Municipal Hospital

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Abstract

Purpose

The accuracy of monitors for measuring transcutaneous \( P_{CO_2 } \) (Tc\( P_{CO_2 } \)), end-tidal \( P_{CO_2 } \) (Et\( P_{CO_2 } \)), and nasal Et\( P_{CO_2 } \) was evaluated.

Methods

The measuring devices included a Tc\( P_{CO_2 } \) monitor (TCM3; Radiometer Trading), an Et\( P_{CO_2 } \) monitor (Ultima; Datex-Ohmeda), and a nasal Et\( P_{CO_2 } \) monitor (TG-920P; Nihon Kohden). The sensor electrode of the TCM3 Tc\( P_{CO_2 } \) monitor was applied to the skin of the subject’s upper arm. A sampling tube attached to the proximal end of the tracheal tube was connected to the Ultima Et\( P_{CO_2 } \) monitor. The miniature sensor of the TG-920P nasal Et\( P_{CO_2 } \) monitor was attached to the nostril. The values obtained were compared with direct measurements of arterial \( P_{CO_2 } \)(\( Pa_{CO_2 } \)) obtained by means of an ABL700 blood gas analyzer (Radiometer Trading) in surgically treated patients. The means ± 2 SD of the differences between variables were calculated.

Results

The Tc\( P_{CO_2 } \) monitor (0.19 ± 4.8 mmHg, mean ± 2-SD) was more accurate than the Et\( P_{CO_2 } \) monitor (−4.4 ± 6.5 mmHg, mean ± 2-SD) in patients receiving artificial ventilation via an endotracheal tube and the Tc\( P_{CO_2 } \) monitor was also more accurate than the nasal Et\( P_{CO_2 } \) monitor (−6.3 ± 9.8 mmHg, bias ± 2-SD) in patients breathing spontaneously.

Conclusion

We found that the Tc\( P_{CO_2 } \) monitor was more accurate than the Et\( P_{CO_2 } \) or nasal Et\( P_{CO_2 } \) monitor in surgically treated patients.

Key words

Transcutaneous \( P_{CO_2 } \) End-tidal \( P_{CO_2 } \) Noninvasive monitor