Practical guidance for the use of indirect calorimetry during COVID 19 pandemic

Abstract

The daily practice requires the use of indirect calorimetry to define the energy requirements of intensive care patients. In the time of COVID-19 pandemic, this practice is challenging. The purpose of this methodology paper is to provide practical guidance to health professionals to perform this measurement safely, using various metabolic monitors.

Introduction

Indirect calorimetry (IC) remains the best tool to assess resting energy expenditure in critically ill patients and ESPEN as well as ASPEN societies recommend its use [1,2]. Nutritional recommendations have been recently released [[3], [4], [5]] and the use of indirect calorimetry in the COVID-19 infection time remains controversial, mainly because of lack of clear instructions regarding a safe use. ASPEN guidelines [4] state that “while energy requirements can ideally be determined by indirect calorimetry, the principle of “clustering” of care is particularly important and ASPEN recommends instead using weight-based equations to estimate energy requirements as a practical matter for the COVID-19 patients.“AuSPEN guidelines [5] ”do not recommend the use of indirect calorimetry (IC) in patients with COVID-19” and ESPEN [3] states that “Energy needs can be assessed using indirect calorimetry if safely available with ensured sterility of the measurement system, or as alternatives by prediction equations or weight-based formulae…” Since our main concern is the personal health professionals safety, we suggest here a guidance to perform indirect calorimetry in an optimal and safe way to ensure an appropriate measurement and energy target determination, according to the use of various metabolic monitors.

1. Guidance for QNRG+ (Cosmed, Rome, Italy) in ventilated COVID19-patients

1.1. Staffing: safety of healthcare practitioners (HCP) is rule number one

Operators should be familiar with the use of the calorimeter, or trained before action, to limit exposure time, avoid mistakes, use time and resources in an optimal way. As manipulation of the ventilator is involved, we recommend medical doctors or HCP's familiar with the ‘COVID’ approach to do the connection and disconnection of the device.

1.2. List up patients

Check ventilation modes and sedation modes off the floor: how many patients will you measure? Do you need extra material? Will you need to change the sedation mode (sevoflurane switch to Propofol?). Think about timing: when will you approach the patients? Are procedures planned?

1.3. Procedure and checklist: be prepared – be ready

All disposables (flow meter, sampling lines, FiO2 adapter, filter) for one measurement should be placed in one plastic bag.

All necessary patient information (name, body weight, length,..)should be introduced in software before going bedside.

1.4. Connection of IC

• a.Apnoe modus or stand by on ventilator
• b.Clamping of endotracheal tube
• c.Use a plastic, see trough, non-sterile plastic cover over the patient to limit virus spread and still see what you are doing. Discard after use (connection and disconnection).

1.5. Actual measurement

Limit time: keep an eye on variability, when <10%, stop recording. Use best 5 min.

1.6. Disconnection

• a.Stop test on Q-NRG
• b.Apnea modus (stand by mode) on ventilator/clamping of tube/plastic cover
• c.Remove disposables, wrap in plastic cover and discard.

1.7. Desinfection

• a.Hand over machine to person non-bedside who handles it with double gloves (follow your local guideline).
• b.Total disinfection conform local practice and remove from COVID zone

1.8. Communication and nutritional therapy adaptation

• a.Operator checks ventilation modus, condition of patient, sedation.
• b.Confirm to nurse procedure is done and state of patient
• c.Communicate how results will be managed and how adaptation of nutritional therapy needs to be done.

1.9. Additional practical points provided by the manufacturer

QNRG is a very safe device that, from a hygiene and disinfection point of view, is much safer than a ventilator.

1.9.1. For ventilated patients

All parts in contact with patients are single use (flowmeter, sampling lines, FiO2 adapter). Bacteria and virus filtration of the HME Filter or the Normal Filter (BFE 99.999%, VFE 99.999%) positioned before the flow meter, counteracts any contamination of the device internally.

1.9.2. For canopy test

Use of disposable single-use veils and cleaning procedure of canopy prevent cross contamination. Use of a high efficiency filter (BFE 99.9999%, VFE 99.999%) placed at the canopy blower/port prevent contaminated air to reach the device.

Additional micro filters are placed internally as a redundant safety measure to prevent device contamination.

Patient Inhalation of air from the unit (for both ventilated, canopy and masks) is prevented by the direction of sampling flow (towards device only).

Always follow the indications, instructions and warnings provided in the user manual of the cleaning and disinfectant agent and select only disinfectants with approved efficiency (e.g. FDA clearance or CE mark). The Spaulding classification system, based on the potential risk of infection, establishes the minimum level of reprocessing needed to ensure medical devices are safe for use.

Classification adapted from [6].

2. Metabolic modules included in monitors

2.1. General electric (GE) E-sCOVX/E-sCAiOVX modules

2.1.1. Practicalities according to the manufacturer

In ICU the gas flow is always away from the patient. Water trap is acting as a protective filter when the protective membrane is intact. Recommendation for user is to be aware of instruction for use (user manual & IFU in the box) and ask users not to manipulate the water trap to avoid breaking the protective membrane. In addition, reading the warnings from user manual is always beneficial - it would be good to connect a scavenging line to gas sample out connector (in front of the module) to avoid sampled gas discharge in room.

2.1.2. Disinfection and cleaning

About cleaning and disinfection, Bx50/CARESCAPE ONE instructions [7] cover also the X-module. We have good filtering in water traps. For the E-sCOVX/E-sCAiOVX modules there is a D-Fend Pro+particle separation White Paper available [8,9].

2.2. Mindray

2.2.1. Suggestions for metabolic monitor with confirmed or highly suspected COVID-19 patients

The metabolic monitor is based on Sidestream CO2 module and RM module. To reduce the risk of cross-patient contamination during metabolic monitoring, the following recommendations apply:

• 2.2.1.1.

  All components and/or accessories that are in contact with the patient's breathing gas be disposable, such as gas sampling line, RM flow sensor, airway adapter, etc.

• 2.2.1.2.

  The water trap on the CO2 or gas module should be replaced after each patient use.

2.2.2. Suggestions for metabolic monitor after usage with confirmed or highly suspected COVID-19 patients

• 2.2.2.1.

  Wrap the CO2 and RM module completely with a plastic, cover, and store them safely for a specified time (e.g. 21 or 28 days) at room temperature or higher, and then follow the cleaning and disinfecting procedures in the operator's manual before next use.

• 2.2.2.2.

  All the disposable accessories should be removed after each case. To ensure the safe disposal of contaminated devices, please refer to the hospital guideline or local regulations.

3. Case illustration

On picture 1 (from E De Waele), a ventilated COVID19+ patient is undergoing a measurement of indirect calorimetry. A plastic cover is placed during connection and disconnection. Clamping of the tube and connection of the Q-NRG disposable is done under the cover. All the disposables (sampling lines, FiO2 adapter, Filter) are placed on the bed and ready to use.

4. Discussion

With the increasing knowledge regarding the spread of the pandemic [10] and with the improvement in the protection of health care professionals [11], diagnostic and therapeutic approaches such as ECMO have been modified and more codified [12,13]. High flow nasal cannula oxygen therapy that was recommended for a couple of hours at the beginning of the epidemic is now a recommendation of the Surviving Sepsis Campaign for COVID-19 [14]. None of any required procedure has been cancelled in the COVID -19 era, in the same perspective, therefore, we think that the AusPEN position [5] may be too conservative and may prevent to evaluate ICU patients accurately and may induce energy prescription leading to over or under nutrition. A recent position paper is strengthening this position [15]. Metabolic information can be of great value as this largely unknown disease may perturbate the Renin-Angiotensin System and energy metabolism [16].

5. Conclusions

It is mandatory to ensure health professional safety while assessing resting energy expenditure using metabolic monitors. This practical guidance gives the recommended approach to allow a safe metabolic evaluation in critical as well as in ward hospitalized patients. A better evaluation of the metabolic needs will allow a more efficient medical nutritional therapy following the international guidelines.

Conflict of Interest

None declared.