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Effect of PEEP on Indirect Calorimetry in Critically Ill Patients (IC-PEEP)

29 de agosto de 2026 atualizado por: Carl Sjödin, Vastra Gotaland Region

Effect of Positive End-Expiratory Pressure on Indirect Calorimetry Measurements in Mechanically Ventilated Critically Ill Patients: A Prospective Physiological Study

Indirect calorimetry is used in intensive care to measure how much oxygen a patient consumes and how much carbon dioxide is produced. These measurements are used to estimate energy expenditure and help guide nutritional treatment. In mechanically ventilated patients, however, ventilator settings may potentially influence the accuracy of indirect calorimetry.

This study will investigate whether changes in positive end-expiratory pressure (PEEP), a routinely used ventilator setting, affect measurements obtained by indirect calorimetry in critically ill mechanically ventilated adults.

Each participant will undergo indirect calorimetry at three PEEP levels: 8, 12, and 16 cmH2O. Each PEEP level will be maintained for a stabilization period before measurements are obtained. Other ventilator settings will be kept unchanged during the measurement sequence whenever clinically feasible.

The study will compare oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ), and resting energy expenditure (REE) across the three PEEP levels. The aim is to determine whether clinically relevant changes in PEEP systematically influence indirect calorimetry measurements and their interpretation.

Visão geral do estudo

Status

Ainda não está recrutando

Condições

Intervenção / Tratamento

Descrição detalhada

Indirect calorimetry (IC) is considered a reference method for assessment of energy expenditure in critically ill patients. It measures oxygen consumption (VO2) and carbon dioxide production (VCO2), from which respiratory quotient (RQ) and resting energy expenditure (REE) are calculated. Reliable measurements are important when IC is used to guide nutritional therapy in mechanically ventilated intensive care patients.

Measurement accuracy may potentially be influenced by ventilator settings and changes in respiratory mechanics. Positive end-expiratory pressure (PEEP) is frequently adjusted during intensive care, but there is limited clinical evidence regarding whether changes in PEEP within commonly used ranges systematically affect contemporary indirect calorimetry measurements. The approved research project therefore includes a physiological substudy specifically examining the influence of PEEP on VO2, VCO2, RQ, and REE.

This is a prospective, single-center, repeated-measures physiological study conducted in mechanically ventilated adult intensive care patients at Sahlgrenska University Hospital. Participants undergo indirect calorimetry during a standardized sequence of three PEEP levels: 8, 12, and 16 cmH2O. Each participant therefore serves as their own control.

At each PEEP level, the patient is allowed to reach a stable condition before indirect calorimetry measurements are obtained. The ethics protocol specifies a stabilization period before measurement and that other ventilator settings should remain unchanged during the PEEP sequence. The final operational study protocol uses PEEP levels of 8, 12, and 16 cmH2O.

Indirect calorimetry measurements will include VO2, VCO2, RQ, and REE. Measurements will be performed under standardized conditions, with attention to measurement stability and ventilator leakage. In the underlying research protocol, acceptable IC measurement periods are defined using steady-state criteria and controlled ventilator conditions.

The primary objective is to determine whether VO2, VCO2, RQ, and REE change systematically across PEEP levels of 8, 12, and 16 cmH2O. Repeated measurements will be analyzed using mixed-effects models accounting for clustering of observations within participants.

PEEP changes are performed within clinically accepted ranges under continuous intensive care monitoring. The measurement sequence will be interrupted if clinically relevant deterioration in hemodynamics, oxygenation, or other physiological parameters occurs. The ethics protocol specifically requires PEEP changes to remain within clinically acceptable levels and to be discontinued if adverse physiological effects are observed.

A relative difference of 10% in indirect calorimetry-derived measurements between PEEP levels was considered clinically meaningful. Assuming a within-participant standard deviation of approximately 12.5%, corresponding to a standardized paired effect size of 0.8, approximately 15 evaluable participants are required to achieve 80% power at a two-sided alpha level of 0.05. To account for incomplete measurement sequences and technically inadequate indirect calorimetry measurements, 20 participants are planned for enrollment.

Tipo de estudo

Intervencional

Inscrição (Estimado)

20

Estágio

  • Não aplicável

Contactos e Locais

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Contato de estudo

Critérios de participação

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Critérios de elegibilidade

Idades elegíveis para estudo

  • Adulto
  • Adulto mais velho

Aceita Voluntários Saudáveis

Não

Descrição

Inclusion Criteria:

  • Age 18 years or older.
  • Admitted to CIVA or NIVA at Sahlgrenska University Hospital.
  • Receiving invasive mechanical ventilation.
  • Expected intensive care stay longer than 72 hours.
  • Arterial catheter in place.
  • Clinical condition considered sufficiently stable by the responsible physician and research nurse to undergo the study-specific PEEP sequence.
  • PEEP levels of 8, 12, and 16 cmH2O considered clinically acceptable for the participant during the study measurement period.

Exclusion Criteria:

  • Ongoing or planned continuous renal replacement therapy or intermittent hemodialysis (CRRT/iHD).
  • Extracorporeal membrane oxygenation (ECMO).
  • Fraction of inspired oxygen (FiO2) >0.70.
  • Severe renal failure or rapidly increasing creatinine where metabolic measurements may be difficult to interpret.
  • Terminal illness or decision for end-of-life care.
  • Previous participation in the study during the same ICU admission.
  • Clinical instability or other condition judged by the responsible physician to make the PEEP measurement sequence unsafe or inappropriate.

Plano de estudo

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Como o estudo é projetado?

Detalhes do projeto

  • Finalidade Principal: Outro
  • Alocação: N / D
  • Modelo Intervencional: Atribuição sequencial
  • Mascaramento: Nenhum (rótulo aberto)

Armas e Intervenções

Grupo de Participantes / Braço
Intervenção / Tratamento
Experimental: Sequential PEEP Levels
All participants undergo indirect calorimetry measurements during a standardized sequence of PEEP levels at 8, 12, and 16 cmH2O. Each PEEP level is maintained for a predefined stabilization period before measurement. Other ventilator settings are kept unchanged whenever clinically feasible. Each participant therefore serves as their own control.
Positive end-expiratory pressure (PEEP) is adjusted sequentially to 8, 12, and 16 cmH2O during a single study session. Each level is maintained until the predefined stabilization criteria are met before indirect calorimetry measurements are obtained. The sequence is performed under continuous intensive care monitoring and is discontinued if clinically relevant deterioration occurs.

O que o estudo está medindo?

Medidas de resultados primários

Medida de resultado
Descrição da medida
Prazo
Resting Energy Expenditure Across PEEP Levels
Prazo: During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
Resting energy expenditure (REE), measured by indirect calorimetry and expressed in kcal/day, will be compared within participants across PEEP levels of 8, 12, and 16 cmH2O. The primary objective is to determine whether changes in PEEP produce systematic and clinically meaningful changes in measured REE.
During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)

Medidas de resultados secundários

Medida de resultado
Descrição da medida
Prazo
Oxygen Consumption Across PEEP Levels
Prazo: During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
VO₂ in mL/min compared within participants at PEEP 8, 12, and 16 cmH₂O.
During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
Carbon Dioxide Production Across PEEP Levels
Prazo: During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
VCO₂ in mL/min compared within participants at the three PEEP levels.
During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
Respiratory Quotient Across PEEP Levels
Prazo: During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)
RQ calculated as VCO₂/VO₂ and compared within participants at the three PEEP levels.
During a single study session: after approximately 20 minutes at each PEEP level (8, 12, and 16 cmH2O)

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Patrocinador

Datas de registro do estudo

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Datas Principais do Estudo

Início do estudo (Estimado)

1 de novembro de 2026

Conclusão Primária (Estimado)

1 de junho de 2028

Conclusão do estudo (Estimado)

1 de outubro de 2028

Datas de inscrição no estudo

Enviado pela primeira vez

25 de agosto de 2026

Enviado pela primeira vez que atendeu aos critérios de CQ

29 de agosto de 2026

Primeira postagem (Real)

1 de setembro de 2026

Atualizações de registro de estudo

Última Atualização Postada (Real)

1 de setembro de 2026

Última atualização enviada que atendeu aos critérios de controle de qualidade

29 de agosto de 2026

Última verificação

1 de agosto de 2026

Mais Informações

Termos relacionados a este estudo

Outros números de identificação do estudo

  • IC-PEEP-01

Plano para dados de participantes individuais (IPD)

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INDECISO

Descrição do plano IPD

The feasibility and conditions for sharing de-identified individual participant data have not yet been determined. Any future data sharing will be subject to applicable ethical approvals, data protection regulations, institutional policies, and appropriate data-sharing agreements.

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