Non-inferiority of Continuing Oral Intake Versus Fasting in Patients With Acute Respiratory Failure

Continuation of Oral Intake Compared With Fasting in Patients With Acute Respiratory Failure Before Intubation : a Non-inferiority Randomized Clinical Trial

Fasting in intensive care is mainly studied in mechanically ventilated patients or those in the weaning phase. Recent research challenge the common assumption of fasting and suggests that continuing enteral nutrition before extubation may be beneficial. Fasting is also practiced before procedures (e.g., tracheostomy, endoscopy) or surgeries, based on anesthetic guidelines. Yet, no data address fasting in non-intubated ICU patients with acute respiratory failure, despite frequent caloric deficits and inadequate nutritional intake.

Aspiration risk often justifies fasting, but studies indicate that swallowing reflexes remain intact in patients receiving high-flow nasal oxygen or non-invasive ventilation. Moreover, although intubation carries a 2-5.9% aspiration risk, rapid sequence induction mitigates this, questioning the necessity of preventive fasting. Despite its prevalence, this practice lacks scientific validation and guideline support.

Patient discomfort is also significant. Hunger and thirst are major sources of distress, and evidence from anesthesiology suggests that allowing fluid intake pre-anesthesia reduces discomfort. Extrapolating these findings to ICU patients could improve well-being.

In conclusion, fasting in ICU patients may contribute to discomfort, dehydration, and malnutrition, while its protective benefits remain uncertain. We hypothesize that maintaining oral intake does not increase the risk of intubation or aspiration-related complications.

Fasting in intensive care is a crucial issue that has primarily been studied in mechanically ventilated patients or during the mechanical ventilation weaning process. This practice has recently been challenged with a study which demonstrated the benefits of continuing enteral nutrition before extubation compared to maintaining an empty stomach. Fasting has also been studied in the context of technical procedures (such as tracheostomy or endoscopy) and before surgery, based on an analogy with pre-anesthetic fasting recommendations.

To our knowledge, no data are available regarding fasting in critically ill patients with acute respiratory failure who are hospitalized in the ICU but not intubated. Nutritional management in this specific patient population is not addressed in current ICU nutrition guidelines, despite evidence in the literature showing that these patients frequently fail to meet theoretical caloric targets. A large proportion of them receive no nutritional intake, whether orally, enterally via a nasogastric or orogastric tube, or parenterally. This highlights a strong rationale for maintaining nutritional support in patients with acute respiratory failure.

One of the major concerns among healthcare teams managing these patients is the potential risk of aspiration. This often leads to delays in resuming oral intake, with patients remaining fasting, possibly as an overly cautious approach. However, several experimental studies, including animal models and studies in patients with acute respiratory failure receiving respiratory support (such as high-flow nasal oxygen therapy or non-invasive ventilation), suggest that swallowing reflexes remain intact in these situations.

Beyond aspiration concerns, tracheal intubation in ICU patients requiring mechanical ventilation carries a risk of gastric content aspiration, estimated between 2% and 5.9% in different studies, potentially leading to pneumonia. Clinically, aspiration may be asymptomatic but can also result in severe pneumonia, acute respiratory distress syndrome, pulmonary fibrosis, and, ultimately, life-threatening complications.

During anesthesia for scheduled surgery, controlled operating room conditions allow for preoperative fasting (six hours without solid food and two hours without clear liquids) before anesthetic induction. By analogy, in intensive care, patients at risk of intubation are often kept fasting as a preventive measure to reduce the risk of aspiration and potential gastric content inhalation in the event of intubation. However, this common practice in ICUs remains unstudied in the literature and is not included in clinical guidelines. Moreover, the systematic use of rapid sequence induction techniques during emergency intubation minimizes the risk of aspiration, potentially reducing the need for preemptive fasting.

Finally, ICU patients experience multiple discomforts. Several studies, including a French study validating the IPREA score, have identified hunger and, more notably, thirst as major sources of discomfort in the ICU. In anesthesiology, preoperative comfort has been extensively studied, and research has shown that allowing patients to drink before general anesthesia significantly reduces thirst and hunger sensations. It is reasonable to extrapolate these findings to ICU patients with acute respiratory failure, suggesting that permitting the intake of liquids and solid foods could improve their overall comfort.

Thus, fasting in the ICU may be potentially harmful - hunger and thirst are frequent sources of discomfort, and dehydration and malnutrition are often inadequately compensated by parenteral routes - while its benefits remain uncertain.

We hypothesize that continuing oral intake in ICU patients at risk of intubation does not increase the need for intubation and does not lead to higher rates of adverse events, such as aspiration or gastric content inhalation, in patients who ultimately require intubation.

Inclusion Criteria:

• Male or female ≥ 18 years old

• Participant affiliated to a social security scheme

• Express oral consent of the participant, or failing that of the trusted support person, or failing that of the next of kin

• Patient hospitalised in an intensive care unit or in a continuous surveillance unit or in an intensive care unit for less than 24 hours.

• Criteria for acute hypoxaemic respiratory failure defined as.

  • Respiratory rate > 25 cpm or indifferent if SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2) infection occurred ≥ 1 time since admission.
  • PaO2/FiO2 < 200 mmHg or equivalent SpO2 (oxygen saturation)/FiO2 (fraction of inspired oxygen) i.e. < 235 (measured under at least 10 L/min high concentration mask)

Exclusion Criteria:

• Patient with criteria for immediate intubation:

  • Persistent or worsening respiratory failure (respiratory rate > 40/min, respiratory failure on physical examination, respiratory acidosis with pH (hydrogen potential ) < 7.25, copious tracheal secretions, hypoxia with SpO2 < 90% despite FiO2 > 80% for more than 5 minutes without technical dysfunction).
  • Major haemodynamic failure (need for increasing vasopressor support with instability and hypoperfusion).
  • Neurological failure (Glasgow score < 8).
  • Cardiac or respiratory arrest

• Chronic lung disease: chronic obstructive pulmonary disease (GOLD grade 3 or 4: Global Initiative for Chronic Obstructive Lung Disease) or other chronic lung disease requiring long-term oxygen or ventilation (this does not include a patient undergoing continuous positive nocturnal pressure for sleep apnoea syndrome).

• Contraindications to oral nutrition: known previous swallowing problems or inability to swallow, digestive sutures, admission for inhalation pneumonia, exclusive parenteral nutrition, etc.

• Patients with a nasogastric or orogastric tube, a jejunostomy or a feeding ileostomy

• Patient already on invasive mechanical ventilation on admission

• Limitation of therapies including a decision not to intubate

• Incapacitated adult (guardianship or curators)

• Pregnant, parturient or breast-feeding women

• Tracheostomised patient

• Patient already included for the first time in this study