EE: Gas Collection Devices in Critically Ill 2013
Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.
EE: Gas Collection Devices in Critically Ill
If the critically ill patient is spontaneously breathing (not intubated or receiving supplemental oxygen), the registered dietitian nutritionist (RDN) should consider the canopy or hood to conduct a resting metabolic rate (RMR) measurement. Typically, the canopy or hood is reasonably tolerated by the patient, fits most patient circumstances and is most likely to produce a complete gas collection. However, patient circumstances or preference may require use of an alternative gas collection device.
Risks/Harms of Implementing This Recommendation
There are no potential risks or harms associated with the application of this recommendation.
Conditions of Application
- This recommendation applies to critically ill patients who are spontaneously breathing and who are not on supplemental oxygen. Patients must be breathing room air on their own.
- Critically ill patients who are intubated must be measured through the mechanical ventilator
- If the patient is dependent on supplemental oxygen, do not attempt to measure RMR. With supplemental oxygen, the indirect calorimeter will provide invalid measurements of RMR (Brandi et al, 1997; Matarese, 1997; McClave and Snider, 1992).
- Logistical considerations (e.g., patient comfort, injuries to the face, tubes in the nose or mouth, claustrophobia) should be taken into account when selecting a gas collection device (Brandi 1997). For other logistical considerations, the RDN is referred to the review by Matarese (1997).
Potential Costs Associated with Application
No obvious costs are associated with the application of this recommendation.
No studies were included in the evidence analysis of this recommendation. However, three review articles provide support for the recommendation.
- The basic principles underlying the application of indirect calorimetry to the accurate measurement of RMR include the requirement that expired carbon dioxide is derived from cellular oxidation, and there should be no transit delay between cells and expired gases (Brandi et al, 1997).
- Complete and accurate gas collection that reflects cellular metabolism is required to obtain an accurate measurement of RMR. In a spontaneously breathing patient, there are a variety of gas collection devices that may be used, with advantages and disadvantages to each, depending on the clinical picture (Matarese, 1997). For example, a mouthpiece and noseclip can be associated with incomplete gas collection because of inadequate seal around the mouthpiece, excessive salivation, dry throat, jaw fatigue and inability to maintain a resting state due to the patient holding the mouthpiece (Matarese, 1997).
- A canopy system can be used for spontaneously breathing patients who do not require supplemental oxygen and carries the advantage of not interfering with a patient’s breathing pattern. However, some patients may feel claustrophobic under a hood. In addition to logistical constraints in terms of hardware, patients on supplemental oxygen present additional challenges because of the possibilities of fluctuating FIO2 concentrations and difficulties reaching steady state. Depending on the system used, it may be possible to adjust the calculations based on breath-by-breath measurements to correct for transient changes in FIO2. An external oxygen blender should be used to ensure stability in the delivery of the FIO2 (McClave and Snider, 1992).
- See Matarese, 1997, and McClave and Snider, 1992, for additional details on measuring spontaneously breathing patients.
Recommendation Strength Rationale
Conclusion statement is grade V and thus the recommendation is consensus.
- Risks/Harms of Implementing This Recommendation
The recommendations were created from the evidence analysis on the following questions. To see detail of the evidence analysis, click the blue hyperlinks below (recommendations rated consensus will not have supporting evidence linked).
Is there a difference in accuracy of RMR measurements related to different types of gas collection devices (such as facemask, mouthpieces with noseclips or ventilated hood/canopy) in the critically ill population?
References not graded in Academy of Nutrition and Dietetics Evidence Analysis Process
- Brandi, L.S., Bertolini, R. and Calafa M. Indirect Calorimetry in Critically Ill Patients: Clinical Applications and Practical Advice. Nutrition, 1997 13, 349-358.
- Matarese LE. Indirect calorimetry: technical aspects. J Am Diet Assoc. 1997 Oct; 97 (10 Suppl 2): S154-S160. Review. PMID: 9336580.
- McClave SA, Snider HL. Use of indirect calorimetry in clinical nutrition. Nutr Clin Pract. 1992 Oct; 7 (5): 207-221. Review. PMID: 1289691.