Intermittent capnography during high-frequency jet ventilation for prolonged rigid bronchoscopy

Background: Gas exchange during high-frequency jet ventilation (HFJV) for p rolonged rigid bronchoscopy (RBS) is usually monitored by arterial blood ga s analysis. Capnography of expired gases during brief HFJV discontinuation may be a reliable and noninvasive supplemental method. Capnography can be p erformed either for single breaths or with respiratory rate (RR) reduced to 10.min(-1). The aim of this study was to demonstrate that capnography duri ng short periods of HFJV discontinuation represents a reliable measure of P aCO2 during prolonged RES. Methods: We prospectively investigated 100 consecutive patients (75 male an d 25 female) undergoing HFJV for RES. HFJV was delivered through the rigid bronchoscope at the following settings: working pressure 1.2 bar, rate 100 min(-1), F1O2 0.99, t(i)/t(tot)0.6. The light guiding channel ending at the distal tip of the rigid bronchoscope was used for gas sampling. Capnograms were assessed at 5 min intervals and compared to PaCO2 from arterial blood samples drawn simultaneously. The accuracy of single breath CO2 sampling w as compared with sampling at RR=10 min(-1). Results: Mean duration of RES was 30+/-21 min. A significant correlation be tween capnography (PetCO(2)) and arterial blood gas analysis (PaCO2) was ob served, being r=0.90 for the RR=10 min(-1) method and r=0.91 for the single breath method. Mean difference between PaCO2 and PetCO(2) was 0.37+/-0.2 k Pa throughout the entire study period. No significant differences between s ingle breath sampling or sampling at RR=10 min(-1) were observed. Conclusion: Capnography performed during short periods of HFJV discontinuat ion reliably and noninvasively reflects PaCO2 during prolonged endoscopic p rocedures. Capnography during HFJV for RES may reduce the frequency of arte rial blood gas sampling, the duration of unmonitored intervals and costs. (C) Acta Anaesthesiologica Scandinavica 44 (2000).