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CRITICAL CARE AND TRAUMA

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^*, and Efrossini Briassouli, MD

From the *Pediatric Intensive Care Unit, University Hospital, University of Crete, Heraklion, Greece; Department of Anaesthesiology, School of Medicine, University of Athens; and The 1st Department of Internal Medicine-Propaedeutic, University of Athens, Athens, Greece.

Address correspondence and reprint requests to George Briassoulis, MD, Pediatric Intensive Care Unit, University Hospital of Heraklion, 71110 Heraklion, Crete, Greece. Address e-mail to ggbriass{at}otenet.gr.

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 prolonged periods of stabilization of connected metabolic monitors. We investigated the immediate effect of open ETS on the accuracy of oxygen consumption (VO₂) and carbon dioxide production (VCO₂) measurements and calculated lung mechanics, 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 VO₂, VCO₂, 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 VO₂, VCO₂, 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 measurements (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.