COMPARATIVE ACCURACY OF SUMI HI-CAPNO FACEMASK AND SENTRI NASAL CANNULA FOR END-TIDAL CARBON DIOXIDE MONITORING IN SPONTANEOUSLY BREATHING PATIENTS UNDERGOING REGIONAL ANAESTHESIA

Abstract

Background: Capnography provides continuous non-invasive assessment of ventilation and is useful for early detection of respiratory compromise in spontaneously breathing patients receiving supplemental oxygen. In non-intubated patients, the accuracy of end-tidal carbon dioxide (EtCO₂) monitoring may vary depending on the sampling interface. This study compared the Sumi Hi-Capno Facemask and the Sentri Nasal Cannula for EtCO₂ monitoring in spontaneously breathing adults undergoing regional anaesthesia. Materials & Methods: This prospective comparative crossover study included 60 adult patients undergoing elective surgery under regional anaesthesia with spontaneous ventilation. EtCO₂ measurements were obtained sequentially using the Sumi Hi-Capno Facemask and the Sentri Nasal Cannula under identical clinical conditions. Arterial partial pressure of carbon dioxide (PaCO₂), measured by arterial blood gas analysis, was used as the reference standard. The primary outcome was comparison of mean EtCO₂ values between the two devices. Secondary outcomes included PaCO₂–EtCO₂ gradient, correlation with PaCO₂, Bland–Altman agreement, waveform quality, and clinical feasibility. Results: The mean arterial PaCO₂ was 39.78 ± 2.91 mmHg. The mean EtCO₂ was 37.68 ± 3.34 mmHg with the Sumi Hi Capno Facemask and 37.62 ± 3.01 mmHg with the Sentri Nasal Cannula, with no statistically significant difference between the two devices (P = 0.8355). The mean PaCO₂–EtCO₂ gradient was 2.10 ± 1.77 mmHg for the Sumi Hi-Capno Facemask and 2.16 ± 1.64 mmHg for the Sentri Nasal Cannula. Both devices showed strong correlation with arterial PaCO₂, with Pearson correlation coefficients of 0.8488 and 0.8467, respectively. Bland–Altman analysis showed comparable agreement with PaCO₂, and the direct inter-device mean bias was minimal at 0.0633 mmHg. Successful waveform acquisition was achieved in all patients. Discussion and conclusion: The Sumi Hi-Capno Facemask and Sentri Nasal Cannula demonstrated comparable EtCO₂ measurement accuracy, PaCO₂ agreement, PaCO₂–EtCO₂ gradients, waveform reliability, and clinical feasibility in spontaneously breathing adults undergoing regional anaesthesia. Both commercial interfaces may be suitable for routine capnographic monitoring, with device selection guided by patient comfort, breathing pattern, procedural requirements, and institutional availability.