Defining Acute Respiratory Distress Syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) was first identified in 1967 during the Vietnam War as a distinctively new subset of hypoxemic respiratory failure. ARDS was first defined in 1994 by the Berlin definition as the acute onset of hypoxemia with bilateral frontal infiltrates on chest radiograph and no evidence of left atrial hypertension. In 1994, the American and European Consensus Conference (AECC) established the specific criteria to describe acute lung injury (ALI) and ARDS. These criteria included acute onset, bilateral lung infiltrates of chest x-ray, no evidence of elevated left atrial pressure, and severe hypoxemia, assessed by the arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2) ratio.

According to the above guidelines, ALI existed at a PaO2/FiO2 of =/< 300mmHg, and ARDS was diagnosed when PaO2/FiO2 =/< 200mmHg. In 2011, the European Society of Intensive Care Medicine proposed that the Berlin ARDS definition replace the AECC definition due to the limitation of diagnostic reliability.

Presently, the Berlin definition of ARDS includes (1-10):

1. An acute onset (within 7 days of new or worsening respiratory symptoms)
2. Bilateral radiographical opacities that are not fully explained by effusion, atelectasis, or masses
3. Arterial hypoxemia is defined by thresholds:
   1. Mild: 200 < PaO2/FiO2 ratio ≤300 mm Hg, on continuous positive airway pressure (CPAP) or positive end-expiratory pressure (PEEP) ≥5 cm H2O (observed mortality 27%)
   2. Moderate: 100 < PaO2/FiO2 ratio ≤200 mm Hg, on PEEP ≥5 cm H2O (observed mortality 32%)
   3. Severe: PaO2/FiO2 ratio ≤100 mm Hg, on PEEP ≥5 cm H2O (observed mortality 45%)
4. Identified risk factor for ARDS (if no clear risk factor, exclude heart failure as a cause)
5. Not exclusively due to cardiac causes

After years of extensive research, we know that ARDS is a complicated emergency clinical condition caused by an inflammatory immune response resulting in endothelial permeability, non-cardiogenic pulmonary edema, and atelectasis. Historically, ARDS has been formally coined as a health condition in recent decades. ARDS has existed since the beginning of time, as lung injuries have existed for as long as humans have.

ARDS is a severe medical complication that, if left untreated, can lead to permanent organ damage, decreased quality of life, and immediate death. Several ARDS patients receive mechanical ventilation, and ARDS has an extremely high mortality of up to 40%, depending on its severity. While ARDS is rarely seen in outpatient settings because of its acute nature, many patients who have survived ARDS have been seen in outpatient settings for years.

If patients are lucky and are in general good health, they can survive ARDS with no immediate complications. However, ARDS can affect anyone, from children to the elderly, causing nurses to be aware of the role of critical care conditions in the acute and chronic health of patients. Also, as COVID-19 and other respiratory pathogens have emerged within the past decade, ARDS clinical guidelines, care practices, and other interventions have shifted.

More research shows that severe respiratory pathogens, such as COVID-19, SARS, and others, can trigger an ALI and contribute to the development of ARDS, even in previously healthy patients.

What’s more is that, as technology advances, more and more patients are recovering from ARDS, a once near-fatal condition with a poor prognosis, and receive outpatient care for their pulmonary health in several outpatient clinics nationwide. In particular, emergency rooms, intensive care units (ICUs), and critical care units can see several patients a day with possible ARDS or at risk of having ARDS. Staffing concerns, documentation issues, and poor provider-patient communication can lead to several cases of ARDS being undocumented, under-treated, or poorly managed, leading to decreased quality of life and poorer health outcomes for patients (1-10).

While many clients receive acute care for ARDS within ICUs nationwide, as the demands for home health nursing and medical interventions shift, the reality is that many clients receive follow-up for ARDS complications and ARDS sequelae in non-emergent health care settings daily. Nursing care and patient monitoring must ensure that patients receive appropriate nutrition, maintain good hydration, tolerate pain management, show respiratory health progression, and improve health and quality of life.

In particular, ARDS management, depending on the severity of ARDS and patient health and response to interventions, is not guaranteed the same outcome for every client. Some clients can have more severe ARDS management complications, such as possible lung transplant, lifelong immunocompromise, and worsening of the client’s health status. Because there are several pharmacological and non-pharmacological ARDS management interventions, including prone positioning, nurses must be aware of the patient’s response and health status (1-15).

Prevalence

The exact prevalence of ARDS is not known, as several instances of ARDS are undetected and unreported. While it is estimated that there are thousands of patients with ARDS in America, it is also estimated that ARDS is more prevalent in women and among older people. Studies estimate that the incidence of ARDS is 64.2 to 78.9 cases per 100,000 person-years, and cases of ARDS can be found in several ICU and critical care units nationwide. That said, there are possible cases of ARDS that never make it to emergent care for logistic reasons, costs, and immediate death. Since ARDS is an emergent condition, people can die of ARDS without ever being treated for this condition or have this condition misdiagnosed or undetected at the time of death (1-10).

Signs and Symptoms

Common signs and symptoms of ARDS include loss of consciousness, difficulty breathing, hypoxemia, severe chest pain, muscle weakness, difficulty speaking, and loss of responsiveness. Oftentimes, ARDS has no immediate hallmark signs, as many respiratory conditions can also trigger difficulty with breathing and severe chest pain. That said, ARDS is noted for its hypoxemia, pulmonary edema, worsening of the client’s health condition, and increased workload of breathing. While diagnostic testing and examination can rule out other conditions, ARDS should be a condition to be aware of in all patients with risk factors and respiratory complications, given the rapid progression of ARDS (1-5).

Risk Factors

The most common risk factor for ARDS is anything that can cause an ALI, such as blunt force trauma, gunshot wound, motor vehicle accident, infection, blood transfusion, surgery, or other similar situations. For instance, blood transfusions are performed daily in several acute healthcare facilities. However, blood transfusions performed on a geriatric client with a history of pneumonia after surgery make this client, in particular, more at risk for developing ARDS. No one develops ARDS from regular breathing, as ARDS is an acute respiratory emergency. However, anyone is at risk of ARDS if they experience an ALI.

It is important to remember that ARDS is triggered by something that causes ALI. Toxic flume inhalation, substance overdose, septic shock, severe aspiration, ventilation complications, COVID-19, SARS, pneumonia, cardiovascular surgery, organ transplant, pneumothorax, excessive fluid in the lungs, traumatic brain injury (TBI), and pancreatitis are some well-known risk factors for ARDS development.

More studies are showing that patients who are female, elderly, consume alcohol, smoke tobacco, undergo radiation therapy, and are more exposed to highly respiratory pathogens are at increased risk of ARDS and ARDS complications. Some studies suggest that ARDS progression and development might have a genetic component, but further research is needed.

Furthermore, it is estimated that at least 10-23% of mechanically ventilated patients nationwide meet ARDS criteria. Mortality associated with ARDS is 40-58%, where some studies have shown an approximate decrease in mortality by 50% when prone positioning is used (1-15).

Clinical Criteria for Diagnosis

ARDS is not diagnosed with a single blood test or examination hallmark feature. ARDS also does not have a single cure or treatment option, as prone positioning and other pharmacological and non-pharmacological interventions can slow the progression or severity of ARDS. Also, ARDS can be diagnosed via the Berlin ARDS criteria and is often still viewed as a diagnosis of exclusion.

For instance, a patient can be treated in a medical-surgical unit for post-cardiac surgery complications and start to develop early symptoms of what could be ARDS or another post-surgical complication. The Berlin ARDS criterion remains the gold standard because there is no single hallmark feature or diagnostic test for ARDS.

While the Berlin ARDS criteria are the main standard for ARDS diagnosis, clinician judgment, and patient response, consideration should guide the need for interventions and prone positioning, as patient response and clinical conditions with ARDS can vary widely. Prompt and effective ARDS management is essential, as prolonged or under-treated ARDS can lead to permanent organ damage, severe health complications, and death. Consultations with respiratory therapists, surgeons, critical care nurses, pulmonologists, and other specialists can be considered for ARDS management (1-20).

Pathophysiology Breakdown of ARDS

The Exudative Phase

Before diving into the benefits of the prone position for ARDS patients, it is important to understand the pathophysiology of ARDS and its implications for ARDS progression, management, and nursing interventions. The pathophysiology of ARDS can be broken down into three main phases: exudative, proliferative, and fibrotic. The cause of the ALI ultimately leading to ARDS can be indirect or direct, influencing the trajectory and severity of ARDS. In direct cases, the injurious agent, such as a gunshot wound, reaches the lung through the airways or by trauma to the chest.

In indirect cases, such as an organ transplant complication, the injurious agent arrives at the lungs through the bloodstream. A direct or indirect agent can injure the alveolar capillary endothelial cells and type I pneumocytes (alveolar epithelial cells). This leads to the loss of the normally tight alveolar barrier to fluid and macromolecules, causing protein-rich edema fluid to accumulate in the interstitial and alveolar spaces (10-20).

Pro-inflammatory cytokines and lipid mediators are increased in this acute phase, leading to the recruitment of leukocytes, especially neutrophils, into the pulmonary interstitium and alveoli. In addition, condensed plasma proteins aggregate in the air spaces with cellular debris and dysfunctional pulmonary surfactant. This forms hyaline membrane whorls, and alveolar edema predominantly involves dependent portions of the lung with diminished aeration.

As edema progresses, there is often a collapse of large sections of the dependent lung, which, in turn, contributes to decreased lung compliance and possible lung failure. Consequently, intrapulmonary shunting and hypoxemia develop, and the work of breathing increases, leading to dyspnea. All of this is then exacerbated by microvascular occlusion that reduces pulmonary arterial blood flow to ventilated portions of the lung (increased dead space! Hello V/Q mismatch!) and in pulmonary hypertension (10-20).

This means that in addition to severe hypoxemia, hypercapnia, secondary to an increase in pulmonary dead space, can be prominent in early ARDS. The exudative phase is typically the first 7 days of exposure to an ARDS risk factor. Symptoms usually present within 12-36 hours of initial insult but can be delayed by 5-7 days, depending on patient response to ALI, patient compensation factors, and other co-existing health conditions. So, what will a patient look like in this phase? Typically, a patient can appear dyspneic with a sensation of rapid shallow breathing and an inability to get enough air.

Tachypnea and increased work of breathing may progress rapidly from mild hypoxemia with a low oxygen requirement to severe hypoxemia with progressively increasing oxygen requirement. A patient can also have associated respiratory fatigue, leading to respiratory failure and, ultimately, a need for mechanical ventilation. An early hallmark clinical sign of ARDS is profound hypoxemia that is resistant to oxygen therapy. Not all patients with ARDS require endotracheal intubation, but it should not be delayed if it is clinically indicated (10-20).

Laboratory values are generally nonspecific and are primarily indicative of underlying clinical disorders or true ARDS severity. The chest x-ray will show infiltrates involving up to 75% of the lung fields, but is often indistinguishable from cardiogenic pulmonary edema (CPE). It’s possible to have both CPE and ARDS exist concurrently. It is often safer to assume that there is a component of ARDS and initiate therapies to reduce lung injury rather than ignore early radiographic findings. Both CPE and ARDS may share bilateral airspace opacifications, but ARDS is not typically associated with cardiomegaly or cephalization of the pulmonary vasculature.

When trying to differentiate between CPE and ARDS on a basic chest radiograph, cardiogenic pulmonary edema typically begins centrally, and ARDS will generally present with a uniform opacification. Pleural effusions are often present in CPE and will respond to diuretic therapy; however, pleural effusions in ARDS persist despite diuresis. Kerley B lines are standard in CPE but not typically found in patients with ARDS. Radiographic and physical exam evidence of cardiogenic pulmonary edema, such as pleural effusions, cardiomegaly, peripheral edema, or clinical heart failure, should be considered in patients with bilateral opacities and respiratory failure (10-20).

Overall, in this phase, the patient looks like the one you’re staring at, wondering what’s wrong with them. They are ill, but you can’t figure out why. Lots of nonspecific findings are present, and the patient looks like there is impending doom.

The Proliferative Phase

The proliferative phase of ARDS typically occurs between days 7-21 of ARDS progression. Patients tend to improve and are frequently extubated from mechanical ventilation during the proliferative phase. In terms of histology, this is where the nurse will see the first signs of improvement. There is the initiation of lung repair, an organization of alveolar exudates, and a shift from neutrophil-dense infiltrates to lymphocyte infiltrates. Despite this, some patients continue to experience dyspnea, tachypnea, and hypoxemia. Some patients will also begin to develop progressive lung injury, which is different from ALI, and begin to show signs of pulmonary fibrosis (10-20).

The Fibrotic Stage

The majority of patients recover from ARDS within approximately three to four weeks. However, some patients develop a fibrotic stage of ARDS that often includes extended mechanical ventilation needs or noninvasive supplemental oxygen requirements. Low tidal volume and high Positive End-Expiratory Pressure (PEEP) mechanical ventilation, along with steroid therapy (when appropriate), may prevent or reduce pulmonary fibrosis.

Histologically, the alveolar edema and inflammatory exudates that typically resolve convert to extensive alveolar duct and interstitial fibrosis. This disruption leads to emphysema-like pulmonary changes. The physiologic consequences of ARDS include an increased risk of pneumothorax, reductions in lung compliance, and increased pulmonary dead space. Patients in this late phase experience a substantial burden of excess morbidity (10-20).

How has ARDS management evolved over the past few decades in your place of work? ARDS develops in three stages. What are the clinical, radiographical, and alveolar features of each stage?

Pharmacological Interventions That Can Alter the Progression of ARDS

As explained previously, most of the pathological insult in ARDS occurs within the first seven days during the exudative phase. The evolution of pulmonary and systemic inflammation during the first week will dictate the physiological progression from exudative to fibrosis. Patients who fail to improve their mechanical ventilation requirements (PEEP and PaO2/FiO2 requirements), static lung compliance, and degree of infiltration on chest x-ray by day 7 of mechanical ventilation exhibit persistently high levels of circulating inflammatory markers. These clients also have a higher mortality rate and are at increased risk of ARDS chronic complications.

Since the direction of systemic inflammatory response is established early in the disease, studies have evaluated the effects of early methylprednisolone and its impact on disease trajectory. Some literature suggests that prolonged, low-dose methylprednisolone (1mg/kg/day) within 72 hours of diagnosed ARDS can reduce ARDS progression and ICU stay (10-22).

Improvement by day 7 also correlated with survival by day 7 and overall hospital survival. While the use of steroids is not the primary method of treating ARDS, there is growing evidence-based research showing that early and prolonged administration of glucocorticoids can lead to more ventilator-free days and decrease overall mortality by preventing the progression to pulmonary fibrosis.

Nurses are encouraged to investigate and be aware of their particular workplace’s policy regarding ARDS and medication administration policies. Evidence-based research also suggests that steroids may help prevent pulmonary fibrosis if given early, but side effects and medication risk profile are factors to consider in patient care overall (10-22).

Case Study

You are a nurse working in a busy Medical ICU. You are coming in to start your shift and receive the sign-out on your patients. There was one admission overnight. A 23-year-old male, Shawn, was brought into the emergency department (ED) from a concert venue with severe alcohol intoxication. He just graduated from college and was celebrating too vivaciously with his family and friends at a local concert.

Per his mom, he ran in the morning and returned to prepare for the tailgate. They started drinking around noon, and Shawn ventured off with friends later in the afternoon. It wasn’t until several hours later that his family began to worry. Eventually, the family got a call from the local ED, saying that Shawn was in their care. He was found by emergency medical services (EMS) to be highly intoxicated, and he was unable to comply with basic procedures. Shawn was then taken to the hospital for further evaluation.

In the ER, he was given fluids, and basic labs were drawn, including a blood alcohol level and a toxicology screen. Labs were all within normal limits. His blood alcohol level was 250 mg/dL. Unfortunately, during his otherwise routine stay, Shawn vomited and aspirated.

Due to his severe intoxication and mental status impairment, Shawn wasn’t able to protect his airway and required intubation. At this point, he was admitted to the medical ICU for further care. Since he’s healthy, the initial nursing care plan is to extubate him early in the day once his sedation wears off and he passes a spontaneous breathing trial (SBT).

Shawn’s Physical Assessment:

• Vital Signs: Temperature: 37C tympanic, HR 97 bpm, BP 128/90 mmHg, respiratory rate 25, SpO2 93% on volume control (VC) mechanical ventilation with settings of 60% fraction of inspired oxygen (FIO2), RR 18, PEEP 5, tidal volume (TV) 350.
• HEENT: Pupils are equal, round, and reactive to light bilaterally—moist mucous membranes. Native teeth intact. Ears intact.
• Cardiovascular: Heart rate and rhythm are irregular. No murmurs, rubs, or gallops. No peripheral edema. Nail beds pink, capillary refill <2 seconds.
• Pulmonary: Intubated on VC, appears comfortable, tachypneic above set ventilator rate. No evidence of auto-PEEP. Diffuse crackles and rhonchi in all lung fields.
• Gastrointestinal: Normoactive bowel sounds. The abdomen is symmetric, soft, and nontender to palpation.
• GU: Foley catheter is in place to drain yellow urine.
• Skin: Intact. No rashes, lesions. Normal skin turgor.
• Neurological: Unable to participate in physical examination due to intubation and sedation. No focal deficits were noted—appropriate response to painful stimuli.

The nurse practitioner (NP) during your shift asks you to hold his sedation and ask the respiratory therapist to transition him to 40% CPAP once he is awake and able to tolerate an SBT. You arrive, and you realize that your patient is failing his SBT. You want to know if this patient should be re-sedated. You call the NP and tell them about the situation. You explain that the patient is now diaphoretic, tachypneic with a respiratory rate of 40/min, SpO2 of 85%, and tachycardic with a HR 127.

The NP arrives in a few minutes, and they decide to lightly re-sedate him, switch him back to full ventilation and 100% FiO2 to allow for his Spo2 to recover, and order some diagnostic tests. The NP orders basic lab work, such as a complete blood count (CBC), comprehensive metabolic panel (CMP), lactate levels, coagulation studies, and an arterial blood gas (ABG) level. The NP also orders a portable chest x-ray.

Diagnosing ARDS

The Berlin Criteria (1-10)

A diagnosis of ARDS is made when a patient meets the Berlin criteria. The Berlin criteria require that all four of the following are met:

1. Timing: Symptoms have begun within one week of a known clinical insult, or the patient has had new or worsening respiratory symptoms over the past week.
2. Chest Imaging: Bilateral infiltrates consistent with diffuse pulmonary edema must be present on either a chest x-ray or chest CT scan that is not explained by pleural effusions, lobar collapse, lung collapse, or pulmonary nodules.
3. Origin of Edema: Respiratory failure must not be fully explained by cardiac failure or fluid overload. A cardiogenic cause of pulmonary edema had to be excluded by pulmonary artery catheterization, showing a pulmonary artery occlusion pressure (PAOP) of <18. Since adopting the Berlin criteria, this has been phased out in favor of using an objective study to rule out hydrostatic pulmonary edema, such as an echocardiogram.
4. Oxygenation: A moderate to severe oxygenation impairment must be present, as defined by PaO2/FiO2. There is a direct correlation between the severity of hypoxemia and the severity of ARDS diagnosis:
5. Mild ARDS: The PaO2/FiO2 ratio is > 200, but ≤ 300, on a ventilator with a PEEP or continuous positive airway pressure ≥ 5 cm H2O. This used to be referred to as acute lung injury- this phrase is now replaced with mild ARDS.
6. Moderate ARDS: The PaO2/ FiO2 ratio is > 100, but ≤ 200 mmHg, on a ventilator with a PEEP ≥ 5 cm H2O.
7. Severe ARDS: The PaO2/ FiO2 ratio is ≤ 100 on a ventilator with a PEEP ≥ 5 cm H2O.

Case Study Continued

The NP receives the lab results, collaborates with the physician in the ICU, and informs you of the results via the patient portal. The labs appear normal except for a minor value of 14,000 leukocytosis.

His ABG is as follows: pH 7.45/CO2 26/ HCO3 22/ PaO2 105 on 100% FiO2. The patient would have a PaO2/FiO2 of 105 using these numbers, compatible with moderate ARDS. In this particular patient, it can be assumed that the inciting incident was the episode of aspiration on stomach contents before intubation in the ED. Since ARDS is an inflammatory process set off due to an underlying disease process, the health care team in the ICU decides that the focus is to treat the underlying disease (in this case, aspiration pneumonia/pneumonitis) and support the respiratory system through the ARDS process.

What Do We Do with the Ventilator in ARDS?

Several evidence-based guidelines can be used to determine ventilator settings and patient management for ventilator patients. It is also important to check with your workplace regarding ventilator management and to ensure that you are working within your scope of work to perform care and adjust ventilator settings as appropriate within your nursing scope.

The cornerstone of ARDS therapies is low tidal volume, high PEEP mechanical ventilation, and the conservative use of intravenous fluids (when there is no organ dysfunction caused by tissue hypoperfusion) in conjunction with diuretics to hasten mechanical ventilation liberation.

Nurses should be aware of the basics of ventilator guidelines, including ventilator setup and adjustment, oxygenation goal, plateau pressure goal, and ventilator weaning. As you read the policies associated with ventilation management in the ARDS patient, you will notice an emphasis on low tidal volume ventilation. As a side effect of this guideline, patients are more likely to become hypercarbic and subsequently acidotic.

The purpose of ventilator management is to allow the damaged and inflamed lungs to heal. For this to be successful, many healthcare providers use a “permissive hypercapnia” philosophy. This means that evidence shows it is better to have patients who are hypercapnic and acidotic to an extent than to have regular blood gas with ventilator settings that damage the lungs. The idea is that in ARDS, we must allow the lungs to heal, even if the blood gas is not perfect. The focus of ARDS mechanical ventilation should be on optimizing the patient’s ventilation while protecting the lungs and not driven by perfecting the ABG results (10-29).

Part 1: Ventilator Set-up and Management

The goal of mechanical ventilation in ARDS is to minimize inflammation by reducing barotrauma and volutrauma to the lungs. The lungs are stiff in ARDS, and each ventilator breath causes alveolar shear. This repeated shearing worsens the inflammation and perpetuates the cycle of increased inflammation and decreased gas exchange across the injured alveoli. The goal of reducing tidal volume and increasing PEEP is to decrease alveolar shear.

To lessen the opportunity of ventilator-associated lung injury, it is recommended to use low tidal volume ventilation with high PEEP coupled with a high respiratory rate. As a surrogate of lung stiffness, we use plateau pressure. If the plateau pressure is consistently above 30, this is an indicator that the injured, stiff lungs are being stretched excessively, causing further injury.

Below is the step-wise, evidence-based approach to achieve adequate ventilation and oxygenation in the ARDS patient without adding insult to injury. You will notice that some of the calculations rely on the patient’s predicted body weight and other health factors (10-29).

1. Calculate predicted body weight (PBW) Males = 50 + 2.3 [height (inches) – 60] and Females = 45.5 + 2.3 [height (inches) -60]
2. Select any ventilator mode
3. Set ventilator settings to achieve initial VT = 8 ml/kg PBW
4. Reduce VT by 1 ml/kg at intervals ≤ 2 hours until VT = 6 ml/kg PBW.
5. Set the initial rate to approximate baseline minute ventilation (not > 35 bpm).
6. Adjust VT and RR to achieve the pH and plateau pressure goals below.

pH Goals and Management

Table 1. pH goals and interventions for ventilator management 

Consider the effect of acidosis rather than the absolute number. Some patients may have hypotension, arrhythmias, skin changes, and other clinical manifestations at a pH of 7.2, while others may tolerate a pH of 7.1 without issues. In general, the approach is one of “permissive acidosis,” meaning acidosis is permitted as much as possible to maximize lung-protective ventilation.

Inspiration to Expiration Ratio Goals

Inspiration (I) to expiration (E) ratio goal (I:E): Duration of inspiration should be < duration of expiration.

Pressure Goals and Management

Plateau pressure goal: ≤ 30 cm H2O

• The plateau pressure is the amount of pressure applied to the terminal airways and alveoli. It’s measured using a 0.5 – 1-second inspiratory pause at end-inspiration, with a <30 cm H2O goal. When titrating ventilator settings, the increasing PEEP coupled with decreased lung compliance can cause increased plateau pressure, leading to a higher risk of alveoli overdistension and lung injury. Using tidal volumes >6-8 mL/kg can add to the risk of overdistension and ventilator-associated volumtrauma.
• Check Pplat (0.5 second inspiratory pause), at least every 4h and after each change in PEEP or VT.
• If Pplat > 30 cm H2O, decrease VT by 1ml/kg steps (minimum = 4 ml/kg). When the tidal volume declines, especially if using volumes of 4mL/kg, check frequent ABGs to avoid complications.
• If Pplat < 25 cm H2O and VT< 6 ml/kg, increase VT by 1 ml/kg until Pplat > 25 cm H2O or VT = 6 ml/kg.
• If Pplat < 30 and breath stacking or dys-synchrony occurs, may increase VT in 1ml/kg increments to 7 or 8 ml/kg if Pplat remains < 30 cm H2O.
• Plateau pressures may be artificially elevated if patients are on the ventilator asynchronously or breathing against it.

Oxygenation Goals and Management

Oxygenation Goal: PaO2 55-80 mmHg or SpO2 88-95%

• Use a minimum PEEP of 5 cm H2O. Consider using incremental FiO2/PEEP combinations to a max FiO2 of 100% and max PEEP of 24 to achieve the goal.
• The physiologic reason behind using high levels of PEEP is to avoid the repetitive opening and closing of the atelectatic alveoli, which can induce or worsen ventilator-induced lung injury. The idea is to keep the alveoli open at end-inspiration and preserve inspiratory lung recruitment.

​Part II: Ventilator Weaning 

Part of weaning clients off the ventilator includes conducting a spontaneous breathing trial daily as tolerated (10-29). Conduct a spontaneous breathing trial (SBT) daily when:

• FiO2 ≤ 0.40 and PEEP ≤ 8 OR FiO2 < 0.50 and PEEP < 5.
• PEEP and FiO2 ≤ values of the previous day.
• The patient has acceptable spontaneous breathing efforts. (May decrease vent rate by 50% for 5 minutes to detect effort.)
• Systolic BP ≥ 90 mmHg without vasopressor support.
• No neuromuscular blocking agents or blockade.

If all the above criteria are met, and the patient has been stable and responsive for at least 12 hours, initiate an SBT of UP TO 120 minutes of spontaneous breathing with FiO2 < 0.5 and PEEP < 5. Follow these steps:

1. Place on T-piece, trach collar, or CPAP ≤ 5 cm H2O with PS < 5
2. Assess for tolerance as below for up to two hours.
   1. SpO2 ≥ 90: and/or PaO2 ≥ 60 mmHg
   2. Spontaneous VT ≥ 4 ml/kg PBW
   3. RR ≤ 35/min
   4. pH ≥ 7.3
3. No respiratory distress. Distress = 2 or more of the following:
   1. HR > 120% of baseline
   2. Marked accessory muscle use
   3. Abdominal paradox
   4. Diaphoresis
   5. Marked dyspnea
4. If tolerated for at least 30 minutes, consider extubation.
5. If not tolerated, resume pre-weaning settings.

Case Study Continued

Let’s go back to our case study. Shawn’s ABG values were pH 7.45/CO2 26/ HCO3 22/ PaO2 105 on 100% FiO2. The PaO2/FiO2 of 105 is compatible with moderate ARDS. The healthcare team decided to focus on treating the underlying disease (Shawn’s aspiration pneumonia/pneumonitis). Using the information from the section above, initially, 8mL/kg PBW would be the tidal volume of 658 mL. Since 6mL/kg PBW is also acceptable, it is appropriate to start there.

The tidal volume can be set to 493 mL, which is still a big breath! You select AC as your ventilator mode, set the FiO2 to 100% TV to 490, respiratory rate of 20 to start, and turn the PEEP up to 18. You let Shawn rest for 30 minutes and get your first ABG, which is as follows: pH 7.13, CO2 65, HCO3 25, PaO2 76.

Based on these results, you consult with the provider on site and are advised to increase the ventilator rate and the PEEP to help with persistent hypoxemia. The provider also orders a follow-up ABG, and this pattern will be repeated until the pH is >7.3 or the CO2 is <25. For the next several hours, the nurse follows this protocol, but the patient remains acidotic. The nurse noticed that his PaO2/FiO2 remains low.

The nurse tried several times to titrate the PEEP up to bring the FiO2 below 100%, but the client’s SpO2 precipitously dropped to the low 80% range each time. The PEEP has been titrated up to 24, and the FiO2 remains 100%.

After several ABGs with worsening acidosis, the provider and clinical team decided to initiate chemical paralysis to ensure complete control of his ventilation and respiratory effort. Sometimes, adequate sedation is insufficient to overpower the body’s innate respiratory drive. Because of this, chemical paralysis is needed to physically take complete control of the patient’s respiratory effort and work towards correcting the profound acidosis.

The nurse also initiates a steroid regimen since it is early in the disease process and can help decrease the likelihood of ARDS progressing to the fibrotic stage. Shawn is 190 lbs, and the recommended dose of methylprednisolone in ARDS is 1mg/kg/day. This comes out to 86mg/day, which will be scheduled to start this evening.

Prone Positioning: What Is It, and Why Are We Doing It?

Prone positioning is a therapeutic modality that has been used to aid in oxygenation in patients diagnosed with ARDS. It involves turning the patient completely over onto their stomach in the face-down position. Prone positioning has been used successfully for many years in patients who have developed ARDS.

Growing evidence-based research has confirmed that oxygenation is significantly improved in patients in a prone position rather than a supine one, particularly for patients with ARDS. Prone positioning first came into practice in the 1970s after the introduction of CT scanning. It was observed on CT scans that lung consolidation and edema were primarily in the dependent lung regions, with the aerated portion of the lung in the non-dependent areas.

Although patient arterial oxygen saturation improves in the prone position, this is likely due to the homogenous redistribution of alveolar stress in the prone position versus the supine position rather than the original hypothesis of better aerating nondependent areas of the lung.

The mechanisms by which prone positioning may benefit patients with ARDS undergoing mechanical ventilation include improving ventilation-perfusion matching, increasing end-expiratory lung volume, and preventing ventilator-induced lung injury by a more uniform distribution of tidal volume through lung recruitment and alterations in chest wall mechanics (30-39).

When to Initiate Prone Positioning

There is no hard and fast rule for initiating prone therapy. There are patient-specific factors that must be considered, as well as facility resources. It is a resource-intensive process and requires vigorous monitoring. Evidence-based literature suggests that earlier proning may be better for short- and long-term outcomes. Currently, proning is often used as a last resort, whereas it may have more benefit when used early. Proning a client remains an area of great debate, but there is some strong evidence suggesting that earlier proning may be superior; hence, this recommendation.  Clinical practices vary, and an individualized choice has to be made for each patient. It is also important to remember that low-tidal volume, high PEEP therapy is likely synergistic with proning therapy (30-39).

How Long and How It’s Done 

There is no standard of time that a patient should remain in the prone position; however, most evidence-based literature states that 12-16 hours a day in the prone position with the remaining 8-12 hours in the supine position shows the most benefit. Evidence suggests that if the patient has improved PaO2 >10 mmHg within 30 minutes of being placed in the prone position, as evidenced by ABG results, prone positioning is more likely to show prolonged benefit from prone positioning. The length of therapy is dictated by the patient’s tolerance of the physical repositioning procedure, success in improving the patient’s PaO2, and whether the patient is able to sustain improvements made in the prone position when transitioned back to supine. While this criterion is not the hard and fast rule for stopping prone positioning, it is the criteria many intensivists use when caring for the proned ARDS patient.

Contraindications to prone positioning include those patients with an increased risk of increased intracranial pressure, hemodynamic instability, spinal cord injuries, and recent abdominal surgery (30-39).

Proning: The Process of Placing a Patient in the Prone Position

Proper forethought is highly recommended before pruning a patient. Ideally, there will be a formal policy and education for staff members. Complications of pruning can include extubation and severe skin breakdown. These complications are increased when the staff is inexperienced and/or untrained (30-39).

To safely prone a patient, there needs to be:

• An adequate number of nurses available to watch lines and safely perform the procedure (likely 3-5)
• A respiratory therapist who is solely responsible for the airway
• A provider experienced in ET intubation is immediately available in case of tube dislodgement

It is suggested that tube feeding be stopped for 2 hours before the procedure to reduce the risk of aspiration. If the patient is not already, place them on 100% Fi02 for 10-20 minutes to provide pre-oxygenation. The first step of the procedure is gathering supplies. The patient will need adequate padding for bony prominences and pressure points and a crash cart, including intubation supplies, eye lubricant, and eye shields. The patient should be paralyzed and adequately sedated before the procedure. The patient’s eyes should be lubricated and taped shut. Padding should be placed on the face, chest, pelvis, wrist, and anterior leg region at a minimum (30-39).

The procedure varies slightly. If the staff uses a specialized bed, staff will place the patient on the bed at this point. The major difference in using a specialty bed is that staff will simply turn the patient using the bed rather than manually. Before actually turning, a nurse should be responsible for each line. Each line (such as the central and arterial lines) should be monitored by a dedicated nurse not involved in the turning process.

A respiratory therapist should be in charge of monitoring the ET tube to ensure it is not displaced. A provider skilled in ET intubation should be present to oversee the procedure and monitor vital signs. 8-12” of cushioning (typically 2-3 pillows) should be placed on the chest and hip region. These will support the patient and allow for adequate lung expansion. For the turning process, the nurse will need 2-4 additional staff members to turn the patient physically. This must be done slowly and meticulously to prevent line/tube displacement (30-39).

Once the patient is prone, all lines and tubes, as well as patient response, should be reassessed. Patient tolerance should be monitored and noted. An ABG within the next 30-60 minutes is compared to one obtained immediately pre-prone positioning. A reverse Trendelenburg position may be used to reduce aspiration risk. Depending on the habitus, the patient may need a pillow placed under their head for positioning and comfort (30-39).

Case Study Continued

Since no other maneuvers are improving Shawn’s respiratory status, and chemical paralysis did not drastically improve his status, the clinical team decides the best option is to place him prone. The facility doesn’t have fancy beds, which can cause facial skin breakdown and take up too much room. The nurse reaches out to another ICU nurse to gather supplies and extra hands to reposition the client manually.

The care team discusses this treatment method with his tearful and scared mother, who agrees to do anything necessary to help her son. Yourself and four experienced ICU nurses prepare Shawn by taping and lubricating his eyes, padding bony prominences (knees, elbows, shoulders, ankles) with soft foam pads, moving cardiac wires to a posterior position to decrease skin breakdown, and retaping his ET to prevent skin breakdown from the plastic holster.

You position yourself at the head of the bed with a respiratory therapist to watch the airway while the nurses position Shawn onto his stomach. You watch hemodynamics for changes in his heart rate or blood pressure, and the nurses ensure that all his IV lines and tubes are without kinks.

After 30-45 minutes, another ABG is drawn, which shows the following: pH 7.32/ CO2 50/ HCO3 24/ PaO2 140. Since his PaO2 has improved from 115 to 140, and the client is otherwise stable, the care team decided to leave him prone for the next 12 hours. The provider orders ABGs hourly to start, a chest x-ray timed for when he will be placed supine again and takes a sigh of relief that finally there is some improvement.

Case Study Continued

After four days of proning Shawn for 12-16 hours daily, his ABGs improved to pH 7.42/ CO2 40/ HCO3 22/ PaO2 95 on 40% FiO2. This still meets the criteria for mild ARDS, but the PaO2 stopped improving with prone vs. supine positioning. The client remained intubated for an additional two days before being extubated to a high-flow nasal cannula.

The client’s first words were, “I am never drinking again.” The client was ultimately discharged from the hospital with home physical therapy to help him regain overall strength and endurance.

Special Considerations for ARDS and Prone Positioning for Special Populations:

Special Considerations for ARDS and Prone Positioning for Pediatric Patients

ARDS and prone positioning are not limited to adult patients. In fact, evidence-based research on infants and children with ARDS and prone positioning is a growing pediatric critical care topic, especially during the COVID-19 pandemic. While ARDS is often diagnosed and seen in adults, anyone can experience an ALI, including children, which can then increase their risk for ARDS.

ARDS and proning in this population can pose a serious risk to someone’s quality of life, educational accessibility, ability to care (or learn to care) for oneself, and more. From toddlers to adolescents, pediatric patients have their own unique set of considerations for ARDS and proning.

For instance, prematurity, burns, physical trauma, gunshots, blood transfusions, nerve damage, and more can affect the pediatric population, causing possible ALIs and an increased risk for ARDS. Also, many healthcare providers might not screen for ARDS initially in pediatric populations, depending on the severity of the ALI.

For instance, a toddler who experienced a blood transfusion after experiencing a car accident might not be the patient deemed most at risk for an ALI leading to ARDS. Likewise, an adolescent could be involved in a fight, leading to a gunshot wound in the chest, leading to ALI and ARDS risks (1-10, 30-39).

Weight, parental consent, medication dosing, frequency of repositioning, cost, accessibility, and patient and caregiver education are all factors to consider when considering proning management options in this population. In addition, proning and ARDS severity can greatly depend on the overall health of the patient, any pre-existing health conditions, and pain severity. While there are several stances and guidelines on ARDS management for pediatric populations, there is still much discrepancy between consistent guidelines and evidence-based research on proning.

Educating parents, caregivers, and family members about proning is essential, especially if patients are discharged after and given outpatient follow-up regimens to complete. For instance, a new mother might see her premature infant be in the prone position in the neonatal NICU, and then, upon discharge, she thinks it might be OK to place the baby prone during naptimes. Education on safe sleep and why prone positioning was done in the hospital versus not continuing this practice outside the hospital is essential (1-15,30-39).

Proning in pediatric patients also needs to be monitored very carefully, as children, in particular, use much smaller sizes of tape, pillows, needle sizes, infusion pumps, and vital sign parameters. Unlike adult populations, children might not be able to verbalize their pain or comfort levels during medical interventions. Despite this, comfort measures and pain medication can be offered and administered, such as music therapy, talk therapy, parental and caregiver involvement, and other non-pharmacological interventions. Taking the time to educate and inform parents about these interventions is essential. Proning in pediatric patients requires a good eye for detail, clear documentation, and excellent patient care. Since tubes are smaller (can be misplaced easily), vital signs can change much more rapidly. Caregivers are often much more involved (1-15, 30-39).

Special Considerations for ARDS and Prone Positioning for Geriatric Patients

The geriatric population is one of the fastest-growing patient populations in America and continues to increase with the rise of America’s aging population. In addition, the geriatric population is the most likely to experience severe ARDS complications, given their likelihood of having more pre-existing health conditions, skin integrity, and decreased immune system response. Elderly patients have several factors that could contribute to the possibility of developing ARDS and the need for proning. Because of their reduced skin integrity, possible increased mobility issues, and polypharmacy concerns, pain management during proning and extra care for skin integrity during repositioning are growing problems in health and among evidence-based research guidelines.

In fact, there are several inconsistencies in proning for elderly patients at times, given clinician judgment, workplace dynamics, patient response to therapy, and caregiver intervention, often leaving providers at their own clinical discretion based on resources and patient situation. For instance, an 86-year-old patient might be admitted for a fall in which they landed on their chest, causing a broken rib to be diagnosed in the ER.

A few days after discharge, this patient has had increasing chest pain while also consuming alcohol daily for the past twenty years. By the time they have reached the ER again, their work of breath is much more, and they collapse in the ER. By the time this patient makes it to the ICU, there are conflicts about the power of attorney, caregiver dynamics, and concerns if proning is an option if the patient does not improve after a few days, given their health condition.

This brief example is just one of many proning consideration cases that occur in ICUs daily. Patient care among elderly patients, including proning care, can be very delicate and sometimes more risky than beneficial. Like all other patients, patients must be assessed before proning to determine the need, extent, duration, frequency, safety, feasibility, and consent (1-15,30-40).

Role of Telemonitoring in Inpatient Care for Patients with ARDS

With the rise of at-home patient care, telehealth, and remote patient monitoring, several patients receive post-ARDS and proning management with the click of a button. While telemonitoring has expanded significantly in the past decade due to the rise of telehealth nursing, technological advances, and more widespread insurance and Internet coverage, ARDS and proning are still managed in critical care settings. But, even within ICUs and critical care settings nationwide, more and more healthcare facilities rely on and adopt artificial intelligence (AI) technology, telemonitoring, and surveillance to detect possible early changes in patient vital signs. While nothing can replace physical examination and monitoring by a healthcare professional, as technology progresses, more technology can be used to detect early possible complications of ARDS, prone positioning, or both (1-20).

Nursing Considerations

Nurses remain the most trusted profession for a reason. They are often pillars of patient care in several healthcare settings. Patients turn to nurses for guidance, education, and support. While there is no specific guideline for nurses’ role in ARDS management and proning education, here are some suggestions to provide quality care for patients with ARDS in the prone position (1-15,30-39).

The Nurse’s Role in ARDS Care

Obtain a Health History

Obtain a detailed health history of the patient. Oftentimes, vital signs and history taking can be complex, especially in acute settings. Many times, ARDS patients can have complex medical histories and various inpatient consults before being diagnosed with ARDS, or being prone, making critical health history notes lost.

As nurses, it is important to be involved in the vital signs, history, and assessment to learn about noticing any abnormalities or medical concerns that warrant medical attention. Also, it is important to assess the patient for any skin changes or mobility concerns that can increase complications with proning. If a patient appears to have issues with their skin, tubes, or vital signs, take the time to assess and reach out to the care team.

Check for Allergies

Read the medical record to see if the patient has allergies, especially to certain adhesives or medications. Many eye tapes and padding materials can be made of several ingredients, and many ARDS patients cannot verbalize allergies by the time they are in the prone position or eligible for prone positioning. Pain medications can also be derived from various sources, making it possible for them to trigger an allergic reaction. Monitor their skin integrity and breathing for changes since patients cannot verbalize possible allergic reaction symptoms.

Provide Education

Educate the caregivers on pain medication administration and non-pharmacological interventions. Answer any questions about the therapies and confirm the orders.

Document Appropriately

Regardless of how long a client has been prone, ensure documentation is current and assessments are regularly performed.

Review Medications

Review medication history at every encounter. In busy clinical settings, reviewing health records can be overwhelming, especially for patients with complex medical histories, ARDS, and those in the prone position. Confirm medications in the IV bags, the tubes are patent, orders are received and documented, and more to avoid medication errors and compromised patient care.

Involve the Interdisciplinary Team

Communicate the care plan to other staff involved for continuity of care. For several patients, especially patients with ARDS and those in prone positions, care often consists of a team of nurses, specialists, pharmacists, caregivers, and more. Ensure that patients’ records are up to date for ease in record sharing and continuity of care.

Engage in Self-Education

Stay current on continuing education related to ARDS and the prone position, as evidence-based information constantly evolves. You can then present your new learnings and findings to other healthcare professionals and educate your patients with the latest information.

Additional Nursing Roles in ARDS Care

Unfortunately, it is impossible to look at someone with the naked eye and determine if they are a good candidate for proning, given the state of their ARDS. Some patients are more visibly deteriorated and can be good candidates for proning. Other patients need more assessment and evaluation before considering the prone position.  Since management and presentation can vary widely, adequate assessment and nursing judgment are essential in ARDS care.

In addition, nurses can answer questions and address concerns regarding ARDS and caregivers’ prone positions. Nurses can provide quality care by reviewing health histories, observing patients during assessments, addressing caregivers’ problems, and diligently repositioning clients (1-10, 20-39).

• Confirm with the medical records or caregivers any existing medical conditions or concerns (need to identify risk factors)
• Confirm with the medical records or caregivers any existing lifestyle concerns, such as alcohol use, other drug use, sleep habits, diet, surgical history, and allergies (need to identify lifestyle factors that can influence the likelihood of ARDS and prone position complications)
• Observe for any changes to the patient’s body, such as changes in breathing, changes in urination, changes in stool, changes in skin texture (potential prone position complication symptoms)

Research Findings

There is extensive publicly available literature on ARDS and prone positioning via the National Institutes of Health (NIH) and other evidence-based journals. Clients interested in clinical trial research can seek more information on clinical trials from local universities and healthcare organizations.

Conclusion

Prone positioning is here to stay since someone, somewhere, will be at risk for experiencing an ALI and the likelihood of developing ARDS. Because of the nuanced nature of prone positioning, evidence-based research, facility resources, medical guidelines, patient health history, and clinical judgment will determine its role for several ARDS patients nationwide.