How often should we perform arterial blood gas analysis during thoracoscopic surgery?

STUDY OBJECTIVES: To continuously measure arterial blood gases (ABGs), to calculate the percentage of anticipated changes over time, and to develop recommendations for sampling frequencies of arterial blood gases in patients undergoing thoracoscopic surgery. DESIGN: Prospective, observational clinical trial. SETTING: University hospital. PATIENTS: 43 consecutive elective patients undergoing thoracoscopic surgery with one-lung ventilation. INTERVENTIONS AND MEASUREMENTS: A Paratrend 7 probe for continuous arterial partial pressure of oxygen and arterial partial pressure of carbon dioxide measurement was introduced through a radial artery cannula in the awake patient before surgery. Data were collected throughout the procedure until patients left the operating room. Afterward, time courses of arterial blood gas values were transformed into frequency space by fast Fourier transform analysis, and the expected deviations in arterial blood gases were calculated over time. MAIN RESULTS: Forty-three consecutive patients undergoing thoracoscopic surgery were included, and arterial blood gas values were measured during a total of 141.5 h. Critical arterial partial pressure of oxygen values