Basing intubation of acutely hypoxemic patients on physiologic principles

by Franco Laghi, Hameeda Shaikh and Nicola Caccani 

Annals of Intensive Care volume 14, Article number: 86, Published: 12 June 2024

  

Abstract

The decision to intubate a patient with acute hypoxemic respiratory failure who is not in apparent respiratory distress is one of the most difficult clinical decisions faced by intensivists. A conservative approach exposes patients to the dangers of hypoxemia, while a liberal approach exposes them to the dangers of inserting an endotracheal tube and invasive mechanical ventilation. To assist intensivists in this decision, investigators have used various thresholds of peripheral or arterial oxygen saturation, partial pressure of oxygen, partial pressure of oxygen-to-fraction of inspired oxygen ratio, and arterial oxygen content. In this review we will discuss how each of these oxygenation indices provides inaccurate information about the volume of oxygen transported in the arterial blood (convective oxygen delivery) or the pressure gradient driving oxygen from the capillaries to the cells (diffusive oxygen delivery). The decision to intubate hypoxemic patients is further complicated by our nescience of the critical point below which global and cerebral oxygen supply become delivery-dependent in the individual patient. Accordingly, intubation requires a nuanced understanding of oxygenation indexes. In this review, we will also discuss our approach to intubation based on clinical observations and physiologic principles. Specifically, we consider intubation when hypoxemic patients, who are neither in apparent respiratory distress nor in shock, become cognitively impaired suggesting emergent cerebral hypoxia. When deciding to intubate, we also consider additional factors including estimates of cardiac function, peripheral perfusion, arterial oxygen content and its determinants. It is not possible, however, to pick an oxygenation breakpoint below which the benefits of mechanical ventilation decidedly outweigh its hazards. It is futile to imagine that decision making about instituting mechanical ventilation in an individual patient can be condensed into an algorithm with absolute numbers at each nodal point. In sum, an algorithm cannot replace the presence of a physician well skilled in the art of clinical evaluation who has a deep understanding of pathophysiologic principles.

Surgical mask on top of high-flow nasal cannula improves oxygenation in critically ill COVID-19 patients with hypoxemic respiratory failure

 

Surgical mask on top of high-flow nasal cannula improves oxygenation in critically ill COVID-19 patients with hypoxemic respiratory failure

 

by Virginie Montiel, Arnaud Robert, Annie Robert, Anas Nabaoui, Tourneux Marie, Natalia Morales Mestre, Maerckx Guillaume, Pierre-François Laterre and Xavier Wittebole

 

Annals of Intensive Care volume 10, Article number: 125 (2020) Published: 29 September 2020

 

Objective

Critically ill patients admitted in ICU because of COVID-19 infection display severe hypoxemic respiratory failure. The Surviving Sepsis Campaign recommends oxygenation through high-flow nasal cannula over non-invasive ventilation. The primary outcome of our study was to evaluate the effect of the addition of a surgical mask on a high-flow nasal cannula system on oxygenation parameters in hypoxemic COVID-19 patients admitted in ICU who do not require urgent intubation. The secondary outcomes were relevant changes in PaCO2 associated with clinical modifications and patient’s feelings.

Design

We prospectively assessed 21 patients admitted in our mixed Intensive Care Unit of the Cliniques Universitaires Saint Luc.

Main results

While FiO2 was unchanged, we demonstrate a significant increase of PaO2 (from 59 (± 6), to 79 mmHg (± 16), p < 0.001), PaO2/FiO2 from 83 (± 22), to 111 (± 38), p < 0.001) and SaO2 (from 91% (± 1.5), to 94% (± 1.6), p < 0.001), while the patients were under the surgical mask. The SpO2 returned to pre-treatment values when the surgical mask was removed confirming the effect of the device rather than a spontaneous positive evolution.

Conclusion

A surgical mask placed on patient’s face already treated by a High-flow nasal cannula device improves COVID-19 patient’s oxygenation admitted in Intensive Care Unit for severe hypoxemic respiratory failure without any clinically relevant side.

Causes and characteristics of death in patients with acute hypoxemic respiratory failure and acute respiratory distress syndrome: a retrospective cohort study

Causes and characteristics of death in patients with acute hypoxemic respiratory failure and acute respiratory distress syndrome: a retrospective cohort study

by Scott W. Ketcham, Yub Raj Sedhai, H. Catherine Miller, Thomas C. Bolig, Amy Ludwig, Ivan Co, Dru Claar, Jakob I. McSparron, Hallie C. Prescott and Michael W. Sjoding

Critical Care volume 24, Article number: 391 (2020)

Background

Acute hypoxemic respiratory failure (AHRF) and acute respiratory distress syndrome (ARDS) are associated with high in-hospital mortality. However, in cohorts of ARDS patients from the 1990s, patients more commonly died from sepsis or multi-organ failure rather than refractory hypoxemia. Given increased attention to lung-protective ventilation and sepsis treatment in the past 25 years, we hypothesized that causes of death may be different among contemporary cohorts. These differences may provide clinicians with insight into targets for future therapeutic interventions.

Methods

We identified adult patients hospitalized at a single tertiary care center (2016–2017) with AHRF, defined as PaO2/FiO2 ≤ 300 while receiving invasive mechanical ventilation for > 12 h, who died during hospitalization. ARDS was adjudicated by multiple physicians using the Berlin definition. Separate abstractors blinded to ARDS status collected data on organ dysfunction and withdrawal of life support using a standardized tool. The primary cause of death was defined as the organ system that most directly contributed to death or withdrawal of life support.

Results

We identified 385 decedents with AHRF, of whom 127 (33%) had ARDS. The most common primary causes of death were sepsis (26%), pulmonary dysfunction (22%), and neurologic dysfunction (19%). Multi-organ failure was present in 70% at time of death, most commonly due to sepsis (50% of all patients), and 70% were on significant respiratory support at the time of death. Only 2% of patients had insupportable oxygenation or ventilation. Eighty-five percent died following withdrawal of life support. Patients with ARDS more often had pulmonary dysfunction as the primary cause of death (28% vs 19%; p = 0.04) and were also more likely to die while requiring significant respiratory support (82% vs 64%; p <  0.01).

Conclusions

In this contemporary cohort of patients with AHRF, the most common primary causes of death were sepsis and pulmonary dysfunction, but few patients had insupportable oxygenation or ventilation. The vast majority of deaths occurred after withdrawal of life support. ARDS patients were more likely to have pulmonary dysfunction as the primary cause of death and die while requiring significant respiratory support compared to patients without ARDS.

A plea for avoiding systematic intubation in severely hypoxemic patients with COVID-19-associated respiratory failure

A plea for avoiding systematic intubation in severely hypoxemic patients with COVID-19-associated respiratory failure

by Eduardo Villarreal-Fernandez, Ravi Patel, Reshma Golamari, Muhammad Khalid, Ami DeWaters and Philippe Haouzi

Critical Care volume 24, Article number: 337 (2020)

Letter to the editor:

In early February 2020, Yang et al. [1] reported an alarming high mortality rate in patients with COVID-19-associated acute respiratory failure requiring mechanical ventilatory support. Such a dreadful outcome was regarded as the fundamental tenet dictating our strategy to treat patients with COVID-19 acute respiratory failure. Two essential recommendations were offered to the medical community in keeping with these first reports: (1) early intubation of hypoxemic patients [2]. Indeed, since a profound hypoxemia appears to be the hallmark of COVID-19-associated pneumonia, the initial consensus [2] was to start invasive mechanical ventilation as soon as possible due to the overwhelming number of patients in respiratory failure presenting at the same time in a hospital and to prevent the risk of hypoxic cardiac arrest; (2) avoidance of high-flow nasal cannula (HFNC) to reduce respiratory droplet aerosolization for healthcare workers [3] in what was seen as “inevitable” intubations.

Systemic hypoferremia and severity of hypoxemic respiratory failure in COVID-19

Systemic hypoferremia and severity of hypoxemic respiratory failure in COVID-19

by Akshay Shah, Joe N. Frost, Louise Aaron, Killian Donovan and Hal Drakesmith 

Letter to the Editor: Critical Care volume 24, Article number: 320 (2020) 

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory coronavirus 2 (SARS-CoV-2) was declared a pandemic on March 11, 2020 [1]. Risk factors associated with respiratory failure in patients with COVID-19 include older age, neutrophilia and elevated inflammatory and coagulation markers [1]. Inflammation is often accompanied by systemic hypoferremia and low iron levels may impair hypoxia sensing and immunity [2], and increase the risk of thromboembolic complications [3]—which are all of significant concern in COVID-19. However, the iron status of COVID-19 patients is unclear. Therefore, we sought to characterise iron parameters, including serum iron, in COVID-19 intensive care unit (ICU) patients and relate these to disease severity.

Beyond Low Tidal Volume Ventilation: Treatment Adjuncts for Severe Respiratory Failure in Acute Respiratory Distress Syndrome

Beyond Low Tidal Volume Ventilation: Treatment Adjuncts for Severe Respiratory Failure in Acute Respiratory Distress Syndrome

1 Critical Care Medicine - Most Popular Articles by Fielding-Singh, Vikram; Matthay, Michael A.; Calfee, Carolyn S.  /  7d //  keep unread  //  hide

Critical Care Medicine: November 2018 - Volume 46 - Issue 11 - p 1820–1831

Objectives: Despite decades of research, the acute respiratory distress syndrome remains associated with significant morbidity and mortality. This Concise Definitive Review provides a practical and evidence-based summary of treatments in addition to low tidal volume ventilation and their role in the management of severe respiratory failure in acute respiratory distress syndrome.

Data Sources: We searched the PubMed database for clinical trials, observational studies, and review articles describing treatment adjuncts in acute respiratory distress syndrome patients, including high positive end-expiratory pressure strategies, recruitment maneuvers, high-frequency oscillatory ventilation, neuromuscular blockade, prone positioning, inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, glucocorticoids, and renal replacement therapy.

Study Selection and Data Extraction: Results were reviewed by the primary author in depth. Disputed findings and conclusions were then reviewed with the other authors until consensus was achieved.

Data Synthesis: Severe respiratory failure in acute respiratory distress syndrome may present with refractory hypoxemia, severe respiratory acidosis, or elevated plateau airway pressures despite lung-protective ventilation according to acute respiratory distress syndrome Network protocol. For severe hypoxemia, first-line treatment adjuncts include high positive end-expiratory pressure strategies, recruitment maneuvers, neuromuscular blockade, and prone positioning. For refractory acidosis, we recommend initial modest liberalization of tidal volumes, followed by neuromuscular blockade and prone positioning. For elevated plateau airway pressures, we suggest first decreasing tidal volumes, followed by neuromuscular blockade, modification of positive end-expiratory pressure, and prone positioning. Therapies such as inhaled pulmonary vasodilators, glucocorticoids, and renal replacement therapy have significantly less evidence in favor of their use and should be considered second line. Extracorporeal membrane oxygenation may be life-saving in selected patients with severe acute respiratory distress syndrome but should be used only when other alternatives have been applied.

Conclusions: Severe respiratory failure in acute respiratory distress syndrome often necessitates the use of treatment adjuncts. Evidence-based application of these therapies in acute respiratory distress syndrome remains a significant challenge. However, a rational stepwise approach with frequent monitoring for improvement or harm can be achieved.

Predictors of Intubation in Patients With Acute Hypoxemic Respiratory Failure Treated With a Noninvasive Oxygenation Strategy

Predictors of Intubation in Patients With Acute Hypoxemic Respiratory Failure Treated With a Noninvasive Oxygenation Strategy

Frat, J-P et al

Critical Care Medicine: February 2018 - Volume 46 - Issue 2 - p 208–215

Objectives: In patients with acute hypoxemic respiratory failure, noninvasive ventilation and high-flow nasal cannula oxygen are alternative strategies to conventional oxygen therapy. Endotracheal intubation is frequently needed in these patients with a risk of delay, and early predictors of failure may help clinicians to decide early. We aimed to identify factors associated with intubation in patients with acute hypoxemic respiratory failure treated with different noninvasive oxygenation techniques. 

Design: Post hoc analysis of a randomized clinical trial. Setting: Twenty-three ICUs. Patients: Patients with a respiratory rate greater than 25 breaths/min and a PaO2/FIO2 ratio less than or equal to 300 mm Hg. Intervention: Patients were treated with standard oxygen, high-flow nasal cannula oxygen, or noninvasive ventilation. 

Measurement and Main Results: Respiratory variables one hour after treatment initiation. Under standard oxygen, patients with a respiratory rate greater than or equal to 30 breaths/min were more likely to need intubation (odds ratio, 2.76; 95% CI, 1.13–6.75; p = 0.03). One hour after high-flow nasal cannula oxygen initiation, increased heart rate was the only factor associated with intubation. One hour after noninvasive ventilation initiation, a PaO2/FIO2 ratio less than or equal to 200 mm Hg and a tidal volume greater than 9 mL/kg of predicted body weight were independent predictors of intubation (adjusted odds ratio, 4.26; 95% CI, 1.62–11.16; p = 0.003 and adjusted odds ratio, 3.14; 95% CI, 1.22–8.06; p = 0.02, respectively). A tidal volume above 9 mL/kg during noninvasive ventilation remained independently associated with 90-day mortality. Conclusions: In patients with acute hypoxemic respiratory failure breathing spontaneously, the respiratory rate was a predictor of intubation under standard oxygen, but not under high-flow nasal cannula oxygen or noninvasive ventilation. A PaO2/FIO2 below 200 mm Hg and a high tidal volume greater than 9 mL/kg were the two strong predictors of intubation under noninvasive ventilation.