Introduction: Obstructive apnoea (OA) is the main factor of desaturation after major surgery (1). In spite of several trials, monitoring of apnoea is not wide spread and SpO2 is the standard monitoring in recovery room. The aim of this study was to evaluate the interest of nasal CO2 monitoring in the detection of postoperative apnoea in recovery room.
Materials and Methods: 28 patients with obesity and/or history of respiratory disease, anaesthetised for abdominal, ENT or superficial surgery have been included. Induction were performed using propofol, remifentanil and sevoflurane or desflurane. In recovery room, respiratory rate (RR), nasal end tidal CO2 (etCO2) and pulse oxymetry (SpO2) were recorded using a Microstream® system (ORIDION®, Jerusalem, Israel), and analysed (PROFOX® software, Escondido, CA). Patients received O2 6 l mn−1 when SpO2 < 93% and morphine bolus IV then PCA to obtain a pain score lower than 40 using a visual analog scale of 100 mm. Apnoea was defined when RR was lower than 6bpm; Hypopnoea when RR was between 6 and 10bpm. Episods of desaturation were defined when the time of low saturation (SpO2 < 91% or between 91% and 95%) was longer than 1% of the total recording time.
Results: Demographics characteristics are: BMI: 29 ± 5 kg m−2, age 62 ± 11 years, duration of anaesthesia: 235 ± 122 min. Apnoea episodes were identified in 10 patients and were responsible for desaturation in 7 patients, hypopnoea occurred in 11 patients and were responsible for desaturation in 2 patients. Low respiratory rate occurred without desaturation in 3 patients (Table 1).
Conclusion: Obstructive apnoea was not the only mechanism for postoperative O2 desaturation. Nasal CO2 monitoring allowed a good detection of apnoea and hypopnoea state even with oxygenotherapy.
1 Catley DM Anesthesiology. 1985;63:20-8.