Will the Use of Respiratory Quotient "RQ" to Optimize Nutrition Therapy With Indirect Calorimetry Improve Treatment Outcomes for Intensive Care Unit (ICU) Patients?
Phase: NA
Conditions: Nutritional Therapy in an ICU
Sponsor: Poznan University of Medical Sciences

Document date: 02.03.2026 
 
 
 
RQCal Study 
 
Will the Use of Respiratory Quotient “RQ” to Optimize Nutrition 
Therapy With Indirect Calorimetry Improve Treatment Outcomes for 
Intensive Care Unit (ICU) Patients? 
 
 
 
 
Organization's Unique Protocol ID : RQ 447/24 
 
 
 
 
 
 
 
 
 

Protocol 
 
Title of the study: Will the use of respiratory quotient “RQ” to 
optimize nutrition therapy with indirect calorimetry improve 
treatment outcomes for intensive care unit (ICU) patients? 
Introduction and assumptions of the research project: 
  Patients treated in intensive care units (ICUs) require comprehensive 
treatment. Nutrition is an important and integral part of this therapy.  
Both insufficient and excessive calorie intake are associated with 
poorer prognosis and increased mortality in ICU patients. 
Furthermore, the caloric requirements of patients in life-threatening 
conditions in the ICU are characterized by periods of hypo- and 
hypermetabolism, which, if nutrition is not optimized, expose 
patients to overfeeding or underfeeding. Therefore, monitoring 
resting energy expenditure (REE) using indirect calorimetry has 
become the “gold standard” in the ICU. Previous methods based on 
mathematical formulas for calculating REE were characterized by 
insufficient correlation with actual demand. Indirect calorimetry uses 
measured exhaled carbon dioxide and the concentration of oxygen 
administered. Then, taking into account patient-dependent 
parameters such as gender, height, and weight, it indirectly calculates 
energy expenditure, which corresponds to caloric demand.  By 
dividing the volume of CO2 released by the volume of O2 absorbed, 
investigators can obtain the respiratory quotient (RQ). This quotient is 
related to the type of diet and is, for example, 0.7 for fats, 0.8 for 
proteins, and 1.0 for carbohydrates. Its value also changes with 
nutritional status. High values may suggest an excessive energy 
supply (relative to demand), while low values may indicate a calorie 
deficit. Some authors suggest that the RQ ratio could potentially be 
used to further optimize nutritional status.  Currently, however, due 
to insufficient research, it is mainly used in clinical practice to assess 

the accuracy of recording and monitoring calorimetry. This study, is  
trying to assess the usefulness of RQ for optimizing nutrition in 
patients treated in the ICU.  
 
Methodology: 
Study group:   
  This will be a randomized study with a study group and a control 
group in patients treated in the ICU. All patients participating in the 
study are patients who, at the time of qualification, are mechanically 
ventilated and treated in the ICU. These will be patients of both sexes, 
aged 18-85 years.  The control group will be fed under the supervision 
of indirect calorimetry and REE, in accordance with current ICU 
nutrition guidelines. In the study group, nutritional preparations will 
be additionally systematized and selected for each patient depending 
on their RQ value, and caloric requirements will be controlled by 
indirect calorimetry and REE, as in the control group. Regular 
assessments of albumin, total protein, total cholesterol, LDL, HDL, 
iron, glycemia, Na+, K+, and triglycerides will be conducted, collected 
along with the routine test package. In addition, typical endpoints for 
patients treated in the ICU will be assessed, such as length of stay in 
the ICU, length of mechanical ventilation, number of days without a 
ventilator, 28-day survival, and survival to hospital discharge. 
Expected duration of the study: October 2024 to October 2026 (2 
years)  
Conditions for inclusion in the study: patients > 18 years of age, 
treated in the ICU, mechanically ventilated, covered by universal 
health insurance 
Conditions for exclusion from the study: ECMO therapy, the need for 
mechanical ventilation with an oxygen concentration in the breathing 
mixture FiO2 > 60%, patients breathing independently without the 

aid of a ventilator, critically ill patients who are not expected to 
survive the next 48 hours, pregnant women, patients < 18 years of 
age or > 85 years of age 
Reasons for discontinuing the study: 
a. if, during the course of the study, there are clear indications that 
one of the groups will experience or worsen final outcomes such as 
mortality, 28-day mortality, length of stay in the ICU – which would 
suggest a clear advantage of one of the chosen strategies, along with 
an increase in the number of patients included in the study, a regular 
analysis of the current effects of both strategies will be conducted, 
b. the patient develops hypersensitivity/intolerance to nutritional 
preparations, with no possibility of switching to another preparation 
used in the study, 
Planned scope of procedures and options for obtaining informed 
consent: 
  All preparations used in the study are tested, registered, and 
routinely used in enteral and parenteral treatment in the ICU. 
Similarly, the use of indirect calorimetry is currently the “gold 
standard” of treatment in the ICU and is part of standard practice in 
the ICU. The devices used for indirect calorimetry automatically 
calculate the respiratory quotient (RQ) without additional therapeutic 
interventions. The laboratory test results that will be used in the 
study are also part of standard therapy in the ICU, will be performed 
along with routine tests, and will not require additional invasive 
interventions. The work will consist solely of systematizing existing 
therapies based on routinely measured RQ values. Therefore, 
investigators believe that it is possible to waive the requirement to 
obtain informed consent to participate in the study. Furthermore, in 
the case of this group of patients, i.e., unconscious, mechanically 
ventilated, and treated in the ICU, given the narrow time frame for 

inclusion in the study, obtaining the consent of the patient or the 
competent court prior to inclusion in the study seems impracticable. 
Expected results and their planned subsequent use:  
  In patients from the control group, investigators should achieve 
faster stabilization of nutritional parameters and fewer episodes of 
underfeeding and overfeeding. This should translate into improved 
endpoints  such as mortality, length of stay in the ICU, and shorter 
mechanical ventilation time. In addition, the systematization and 
algorithms for the use of nutritional products developed during the 
study can be further used in  our department and other departments 
in the country and around the world.