Metabolic Cart

Metabolic Cart

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Critical illness can significantly affect metabolism, so an accurate measurement of the resting energy expenditure (REE) can help determine the energy requirements in ICU patients. REE (usually 70% of the total energy expenditure) can increase after burns, sepsis, trauma, and surgery. A precise calculation of energy expenditure may prevent overfeeding or underfeeding.

REE can be measured with indirect calorimetry using a metabolic cart, which is used to measure the oxygen consumption (VO2) and carbon dioxide production (VCO2). Every liter of oxygen consumed is equivalent to the energy cost of 5 kcal. A metabolic cart can also be used to assess the energy requirements during exercise and to determine work capacity.

In 1949, Weir introduced an equation to facilitate the calculation of REE, as follows:

REE = [VO2 (3.941) + VCO2 (1.11)] 1440 min/day

Metabolic cart is indicated for the following:

To guide appropriate nutritional support

To determine the oxygen cost of work of breathing and to help select appropriate ventilator mode and settings [1]

To determine the causes of increased ventilatory requirements (high glucose intake can increase carbon dioxide production, stimulating ventilation and complicating weaning)

To measure cardiac output [2]

Exercise physiology

In general, metabolic cart has no contraindications unless transient disconnection from mechanical ventilation cannot be tolerated.

The following are relative contraindications to indirect calorimetry:

Leaks around endotracheal or tracheostomy tube, including cuffless tubes

Chest tube to suction and leaks around the chest tube

Subcutaneous emphysema and communicating tracheal esophageal fistula

Ventilatory modes that use bias flow or leak compensation

Although not representing a contraindication, measurements may be inaccurate in patients who require high levels of oxygen (FiO2 ≥60%), high PEEP (>10 cm H2 O), air leaks, peritoneal or hemodialysis up to 4 hours after (the latter due to elimination of carbon dioxide across the artificial dialysis membrane).

The key to indirect calorimetry is that all inspired and expired air must be collected; any potential leaks in the closed ventilatory system leads to errors in the readings or uninterpretable results.

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Holland AE, Dowman L, Fiore J Jr, Brazzale D, Hill CJ, McDonald CF. Cardiorespiratory responses to 6-minute walk test in interstitial lung disease: not always a submaximal test. BMC Pulm Med. 2014 Aug 11. 14:136. [Medline]. [Full Text].

Miller M. R., Hankinson J, Brusasco V, et al. ATS/ERS Task Force: standardization of lung function testing. Eur Respir J 2005. 2005. 26:319-338.

ATS/ACCP statement on cardiopulmonary exercise testing. American Thoracic Society/ American college of chest physicians. 2002.

AARC Clinical practice guideline, Metabolic measurement using indirect calorimetry during mechanical ventilation. Respiratory Care. 09/2004.

Flancbaum L, Choban PS, Sambucco S, Verducci J, Burge JC. Comparison of indirect calorimetry, the Fick method and prediction equations in estimating the energy requirements of critically patients. Am J Clin Nutr. 1999. 69:461-466.

Wysokinski A, Kloszewska I. Blood serum levels of CART peptide in patients with schizophrenia on clozapine monotherapy. Psychiatry Res. 2014 Aug 21. [Medline].

Zanni MV, Schouten J, Grinspoon SK, Reiss P. Risk of coronary heart disease in patients with HIV infection. Nat Rev Cardiol. 2014 Oct 21. [Medline].

Agustina D Saenz, MD Resident Physician, Department of Internal Medicine, Albert Einstein Medical Center

Disclosure: Nothing to disclose.

David C Sestili, CRT, RPFT, LRCP Coordinator, BREATHE AIRE Programs, Pulmonary Diagnostic Technologist, Respiratory and Pulmonary Diagnostic Laboratories, Albert Einstein Medical Center

David C Sestili, CRT, RPFT, LRCP is a member of the following medical societies: American Association for Respiratory Care

Disclosure: Nothing to disclose.

Richard J Grant, MD, MS, MPH Chair, Division of Geriatrics, Albert Einstein Medical Center; Medical Director, Allegheny Valley School; Medical Director, Einstein Center for Adults with Developmental Disability; Medical Director, Wesley Enhanced Living at Pennypack Park

Disclosure: Nothing to disclose.

Glenn Eiger, MD Director of Internal Medicine Residency Program, Associate Chairman, Department of Medicine, Albert Einstein Medical Center

Glenn Eiger, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Chest Physicians, American College of Physicians-American Society of Internal Medicine, American Thoracic Society, Phi Beta Kappa, Association of Program Directors in Internal Medicine

Disclosure: Nothing to disclose.

Michael R Pinsky, MD, CM, Dr(HC), FCCP, MCCM Professor of Critical Care Medicine, Bioengineering, Cardiovascular Disease, Clinical and Translational Science and Anesthesiology, Vice-Chair of Academic Affairs, Department of Critical Care Medicine, University of Pittsburgh Medical Center, University of Pittsburgh School of Medicine

Michael R Pinsky, MD, CM, Dr(HC), FCCP, MCCM is a member of the following medical societies: American College of Chest Physicians, American College of Critical Care Medicine, American Thoracic Society, European Society of Intensive Care Medicine, Society of Critical Care Medicine

Disclosure: Received income in an amount equal to or greater than $250 from: Masimo, Edwards Lifesciences, Cheetah Medical<br/>Received honoraria from LiDCO Ltd for consulting; Received intellectual property rights from iNTELOMED for board membership; Received honoraria from Edwards Lifesciences for consulting; Received honoraria from Masimo, Inc for board membership. for: Received consulting fees, ExoStat .

Metabolic Cart

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