The Effects of Endotracheal Suctioning on the Accuracy of Oxygen Consumption and Carbon Dioxide Production Measurements and Pulmonary Mechanics Calculated by a Compact Metabolic Monitor George Briassoulis, MD, PhD* Panagiotis Briassoulis, MD† Evi Michaeloudi, MD* Diana-Michaela Fitrolaki, MD* Anna-Maria Spanaki, MD* Efrossini Briassouli, MD‡ BACKGROUND: Open endotracheal suctioning (ETS), which is performed regularly in mechanically ventilated patients to remove obstructive secretions, can cause an immediate decrease in dynamic compliance and expired tidal volume and result in inadequate or inaccurate sidestream respiratory monitoring, necessitating pro- longed periods of stabilization of connected metabolic monitors. We investigated the immediate effect of open ETS on the accuracy of oxygen consumption (VO 2 ) and carbon dioxide production (VCO 2 ) measurements and calculated lung me- chanics, respiratory quotient, and resting energy expenditure in mechanically ventilated children without severe lung pathology, when using a compact modular metabolic monitor (E-COVX) continuously recording patient spirometry and gas exchange measurements. METHODS: Open ETS was performed when clinically indicated in 11 children mechanically ventilated for sepsis or head injury. A total of 2800 pulmonary 1-min gas exchange measurements were recorded in 28 ETS instances for 50 consecutive minutes before and 50 min after the standardized procedure. RESULTS: Pulmonary mechanics and indirect calorimetry did not differ between pre- and postsuction sets of measurements. Pre- and postsuction VO 2 , VCO 2 , dynamic airway resistance, dynamic compliance, and expiratory minute ventilation remained stable from 5 to 55 min after tracheal suctioning and did not differ among different ventilatory modes. Average paired differences of sequential pre- and postsuction VO 2 , VCO 2 , respiratory quotient, and resting energy expenditure were -0.6%, -1%, -0.1%, and -0.3%. Ratio differences between the first and the second periods of measure- ments (1–25 vs 26 –50 sets of 1-min measurements) did not differ in the two groups. CONCLUSIONS: Pulmonary mechanics and indirect calorimetry measurements are not influenced after uneventful open ETS in well-sedated patients. The E-COVX is able to reliably record spirometry and metabolic indices as early as 5 min after suctioning at different ventilator modes. (Anesth Analg 2009;109:873–9) The most accurate method for determining resting energy expenditure (REE) in hospitalized patients is indirect calorimetry. 1,2 Metabolic monitoring devices used in the critical care setting, however, are subject to a range of conditions that may compromise their accuracy. 3 More specifically, metabolic monitors’ er- rors were shown to be significantly affected by oxygen concentration and minute ventilation 4 and when used during inhaled anesthesia. 5 Additionally, older sys- tems like Deltatrac II (Datex Ohmeda 2000, Helsinki, Finland), which measure gas volume in a mixing cham- ber, are relatively expensive, require a high level of technical expertise, and are time consuming to calibrate. 6 New compact modular metabolic monitors like the E-COVX™ (formerly M-COVX™, GE Healthcare/ Datex-Ohmeda), which use a breath-by-breath method to analyze oxygen consumption (VO 2 ) and carbon diox- ide production (VCO 2 ), are less expensive and simpler to use, perform calibration automatically, and are much smaller in size. 7 Using such a simple monitor in certain ventilation modes and in nonsedated patients, however, may not provide measurements within a clinically ac- cepted range. 8 Open endotracheal suctioning (ETS) is performed regularly in mechanically ventilated children to remove obstructive secretions. It was shown that ETS can cause an immediate decrease in dynamic compliance and expired tidal volume in ventilated children intubated From the *Pediatric Intensive Care Unit, University Hospital, University of Crete, Heraklion, Greece; †Department of Anaesthe- siology, School of Medicine, University of Athens; and ‡The 1st Department of Internal Medicine-Propaedeutic, University of Ath- ens, Athens, Greece. Accepted for publication May 4, 2009. Address correspondence and reprint requests to George Brias- soulis, MD, Pediatric Intensive Care Unit, University Hospital of Heraklion, 71110 Heraklion, Crete, Greece. Address e-mail to ggbriass@otenet.gr. Copyright © 2009 International Anesthesia Research Society DOI: 10.1213/ane.0b013e3181b018ee Vol. 109, No. 3, September 2009 873