Respiration monitoring in PACU using ventilation and gas exchange parameters

The importance of perioperative respiration monitoring is highlighted by high incidences of postoperative respiratory complications unrelated to the original disease. The objectives of this pilot study were to (1) simultaneously acquire respiration rate (RR), tidal volume (TV), minute ventilation (MV), SpO(2) and PetCO(2) from patients in post-anesthesia care unit (PACU) and (2) identify a practical continuous respiration monitoring method by analyzing the acquired data in terms of their ability and reliability in assessing a patient’s respiratory status. Thirteen non-intubated patients completed this observational study. A portable electrical impedance tomography (EIT) device was used to acquire RR(EIT), TV and MV, while PetCO(2), RR(Cap) and SpO(2) were measured by a Capnostream35. Hypoventilation and respiratory events, e.g., apnea and hypopnea, could be detected reliably using RR(EIT), TV and MV. PetCO(2) and SpO(2) provided the gas exchange information, but were unable to detect hypoventilation in a timely fashion. Although SpO(2) was stable, the sidestream capnography using the oronasal cannula was often unstable and produced fluctuating PetCO(2) values. The coefficient of determination (R(2)) value between RR(EIT) and RR(Cap) was 0.65 with a percentage error of 52.5%. Based on our results, we identified RR, TV, MV and SpO(2) as a set of respiratory parameters for robust continuous respiration monitoring of non-intubated patients. Such a respiration monitor with both ventilation and gas exchange parameters would be reliable and could be useful not only for respiration monitoring, but in making PACU discharge decisions and adjusting opioid dosage on general hospital floor. Future studies are needed to evaluate the potential clinical utility of such an integrated respiration monitor.