Indirect Calorimetry

Indirect Calorimetry is a procedure which measures the amount of energy a person expends. It measures the Resting Energy Expenditure the amount of calories a person burns at rest per day called Resting Energy Expenditure or REE Depending on body size and activity , a normal healthy adult may burn from 1000 to 3000 Kcal per day to maintain normal body functions.

Indirect Calorimetry calculates heat production by measuring gas exchange. During resting conditions food sources are broken down to produce energy (heat or kcals). The oxygen consumed and the carbon dioxide produced are measured to provide an indirect assessment of calorie requirement at rest per day.

What are the benefits of the test to the patients as well as to the doctors?

The following information will give us the following benefits:

1. Resting energy expenditure (REE) - measures the body’s actual caloric requirement per day. This will guide us on how much calories the person needs to take per day.

2. Respiratory quotient (RQ)- estimates where the energy is mainly coming from (Carbohydrates, Protein and Fats)

3. Substrates utilization – specific percentages of energy source (from Carbohydrates, Protein and Fats) – so that diet can be tailored according to what an individual needs.

Which patients will benefit from Indirect Calorimetry?

Patients with the following conditions will benefit from Indirect Calorimetry:

• Neurologic trauma

• Paralysis/stroke

• COPD (chronic bronchitis/emphysema)

• Acute pancreatitis

• Cancer

• Multiple trauma/Post op surgery/Burns

• Amputations

• Severe sepsis/infections

• Obese/malnourished patients

• Diabetic patients

• Hyperthyroidism/hypothyroidism

• Weight management and sports nutrition

• Failure to wean from mechanical ventilation/ Critically ill patients

• Patients who fail to respond adequately to estimated nutritional needs

• Patients who require long-term acute care

• Renal patients undergoing dialysis

How is the patient prepared for the procedure?

Ambulatory

• The patient should maintain his regular diet a day prior to the procedure, then must undergo fasting for at least 4 hours just before the procedure.

• He needs to rest for at least 30 minutes before the actual test.

• If 24-hour urinary urea nitrogen determination is required, Indirect Calorimety should be performed within the 24-hour urine collection period.

• Patient must be relaxed and undisturbed. Ventilated Patients

• F1o2 should not be more than seventy percent (70%). Patients requiring more than 70% Fio2 cannot undergo the procedure.

• No Fio2 adjustment within ninety (90) minutes prior to procedure.

• No sedation within one (1) hour prior to procedure.

• Suctioning shall not be allowed one (1) hour prior to procedure.

• Enteral and parenteral feeding shall be maintained at constant rate

• Oral feeding shall be restricted two to four (2-4) hours prior to procedure

• If twenty four (24) hour urinary nitrogen is required. Indirect calorimetry shall be performed within collection period.

Reference:

American Association for Pulmonary Care, AARC Clinical Practice Guideline

Metabolic measurement using indirect calorimetry during mechanical ventilation-2004 revision and update. RespirCare Sept;49(9):1073-9

Note:   This information is not intended to be used as a substitute for professional medical advise, diagnosis or treatment.   If you or someone you know have any of the symptoms mentioned above, it is advisable to seek professional help.

For more information, please call:

PULMONARY DIAGNOSTIC AND THERAPEUTIC CENTER

Tel. nos.: (632) 988-1000 / (632) 988-7000 ext. 6238

NUTRITION MANAGEMENT SERVICES

Tel. nos.: (632) 988-1000 / (632) 988-7000 ext. 6510

CENTER FOR PATIENT PARTNERSHIP

Tel. nos.: (632) 988-1000 / (632) 988-7000 ext. 6444