Learning Objectives
By the end of this section, you will be able to:
- Discuss the pathophysiological changes to the patient’s respiratory concerns when in the intensive care unit
- Describe the medical assessments and therapies that apply to the critical care patient’s respiratory system
- Apply nursing concepts and plan associated nursing care for the critical care patient’s respiratory system
One of the leading causes of ICU admissions is acute respiratory failure (ARF), which is a sudden failure of the lungs that causes impaired gas exchange. The result is both hypoxemia, or low oxygen levels in the blood, and hypercapnia, or elevated carbon dioxide levels. In hypoxemia, body organs are not adequately perfused, leading to organ dysfunction and eventual failure. This highlights the importance of maintaining both a patent airway and adequate ventilation for patients in critical care settings. Without appropriate respiratory care, the patient’s life is at risk and systemic complications may result.
Pathophysiological Insult to the Critical Care Patient’s Respiratory System
Respiratory failure is common in critically ill patients, and the COVID-19 pandemic contributed to an increase in respiratory failure incidence over the last several years (Wilcox, 2020). There are two main types of respiratory failure: hypoxemic and hypercapnic (Mirabile, Shebl, Sankari, & Burns, 2023). These two types are briefly outlined in Table 35.5.
| Hypoxemic Respiratory Failure | Hypercapnic Respiratory Failure | |
|---|---|---|
| Definition | The failure of the lungs and heart to provide adequate oxygen to meet the body’s metabolic needs | The failure of the lungs to eliminate carbon dioxide (CO2) from the body |
| Diagnostic criteria | Partial pressure of oxygen (PaO2) <60 mm Hg without elevation of CO2 | Partial pressure of CO2 (PaCO2) >50 mm Hg (hypercapnia) |
| Causes |
|
|
Exemplar: Acute Respiratory Distress Syndrome
Acute respiratory distress syndrome (ARDS) is the most severe form of ARF, with a nearly 40% mortality rate (Siegel, 2022). Among other causes, studies have shown a direct correlation between severe COVID-19 cases and the development of ARDS. Other common causes of ARDS are listed in Table 35.6.
| Direct causes | Fatty embolism Gastric aspiration Near-drowning Respiratory infection (e.g., COVID-19, pneumonia) Trauma resulting in chest or lung injury |
| Indirect causes | Burn injury Cardiopulmonary bypass Drug overdose Multiple blood transfusions Sepsis |
The pathophysiology of ARDS is not well understood, but it appears to involve widespread lung inflammation after injury or insult, which results in an accumulation of fluid in the alveoli, or air sacs, of the lungs. Fluid-overloaded alveoli are not able to function effectively, which results in severely decreased gas exchange within the lungs and a decreased perfusion of oxygenated blood to the tissues. Assessment findings and diagnostic criteria associated with ARDS are listed in Table 35.7. Treatment for ARDS involves providing oxygenation, pharmacological interventions, and prone positioning, all of which are discussed in more detail later in this chapter.
| Assessment findings |
|
| Diagnostic criteria |
|
Endotracheal Intubation and Mechanical Ventilation
Intubation refers to the placement of a flexible ETT through the patient’s mouth or nose and into the trachea and airway. Most commonly, this is performed through the mouth and the tube is left in place so it can be connected to a ventilator to control the patient’s respiratory efforts. At the end of the ETT is a distal cuff, or balloon, that is inflated with a small amount of air to keep the tube in place and seal off the trachea so that air passes through, and not around, the tube. An illustration of an ETT placement is shown in Figure 35.8. The ETT is secured with a harness that is threaded around the back of the patient’s head and held in place with Velcro straps and padded stickers on the cheeks to prevent skin breakdown.
Once the ETT has been placed, the nurse and RT collaborate to connect the tube to the ventilator. A ventilator provides mechanical ventilation that takes the place of the patient’s own breathing and respiratory drive (Figure 35.9.) Successful placement of an ETT tube includes listening for air passage in all lobes, a chest X-ray to confirm placement, and end-tidal CO2 measurements, which demonstrate appropriate ventilation. Ventilators are used for many conditions, some of which involve the patient being unable to adequately breathe on their own, such as ARF, or traumatic brain injury that interferes with the patient’s respiratory drive. Ventilators provide several different modes and settings that can be adjusted according to the function of the patient’s respiratory system. Some supplement the patient’s initiated breaths; others deliver all breaths while the patient is sedated or pharmacologically paralyzed.
Nurses work closely with the respiratory care team to ensure the correct ventilator mode is being used and that appropriate changes in settings are made on the basis of changes to the patient’s condition. One of the main roles of the nurse when caring for patients connected to a ventilator is suctioning the airway as needed. Often, an in-line suction catheter is attached to the ETT, allowing for sterile suctioning of the airway at the bedside for patients with excessive respiratory secretions. Another role of the nurse when caring for a patient receiving ventilator assistance is communication with other team members, most notably the RT and provider, to ensure optimal functioning and management of the ventilator.
Exemplar: Ventilator-Associated Pneumonia
Though mechanical ventilators are necessary in many cases, their use increases the risk of aspiration and subsequent infection, which can result in ventilator-associated pneumonia (VAP), which is pneumonia that develops within 48 hours of the patient being intubated. The development of VAP has been linked to longer hospitalizations and increased health-care costs, indicating the important need for prevention measures in the critical care setting. Many ICUs have implemented intervention bundles that can help prevent the development of VAP. An example of one of these care bundles is presented in the following Quality and Safety Education for Nurses (QSEN) Feature Box.
Clinical Safety and Procedures (QSEN)
QSEN Competency: Evidence-Based Practice
Definition: integrate best current evidence with clinical expertise and patient and family preferences for delivery of optimal health care.
Evidence-Based Practice Strategies to Avoid VAP: VAP Practice Bundle.
The nurse will
- maintain ETT cuff pressure,
- keep the head of the bed elevated to at least 30°,
- provide regular oral care with chlorhexidine swabs,
- conduct daily awakening (“sedation vacation”) with assessment of need for continued intubation, and
- administer prophylactic medications for stress ulcers and deep venous thrombosis.
Medical Assessments and Therapies
One of the most frequently used bedside diagnostic tests for assessing respiratory function and gas exchange in the ICU is arterial blood gas (ABG) measurement. This test involves obtaining a blood sample either by direct needle puncture of the radial artery (Figure 35.10) or from an arterial catheter. The sample is then processed and laboratory values reflect the patient’s oxygenation status. These values and their descriptions are listed in Table 35.8. Critical care nurses must understand the meaning of these values and collaborate with the respiratory therapy team to implement changes to the plan of care and interventions based on ABG findings.
| ABG Component | Normal Range | Description | Clinical Significance |
|---|---|---|---|
| PaO2 | 80–100 mm Hg | The pressure of oxygen dissolved in the blood |
|
| pH | 7.35–7.45 | The concentration of hydrogen (H+) ions in the blood |
|
| PaCO2 | 35–45 mm Hg | The pressure of CO2 dissolved in the blood |
|
| Bicarbonate (HCO3−) | 22–26 mEq/L | A substance that acts as a base to neutralize acids in the body |
|
| Base excess or base deficit | −2 to +2 mEq/L | The sum of all buffer bases in the body |
|
Pharmacological Supports
There are different classes of medications commonly given in critical care settings as part of care for the respiratory system. For patients receiving mechanical ventilation, use of sedatives and neuromuscular blocking agents (also called paralytics) may be indicated. These classes of medications are often used to minimize movement when patients are receiving ventilatory support; movement may potentially dislodge the ETT and compromise the patient’s airway. It is important to temporarily pause these medications at least once per day to assess the patient’s neurological status and continued need for intubation and mechanical ventilation. These periods are often called “sedation vacations,” and they can be performed at the same time as spontaneous breathing trials (SBTs), which are discussed in the next section. In addition to sedation, patients receiving ventilatory support often receive IV opioid medications for pain relief. Placement of an ETT for long periods can cause pain, particularly when combined with immobility, so it is important for critical care nurses to frequently assess and treat patients for nonverbal signs of pain. This is especially important for patients receiving ventilatory support because they are unable to verbally communicate their pain level, requiring a degree of nursing assessment skills to determine pain level on the basis of body language and other nonverbal clues such as changes in vital signs.
Another class of medications used to treat severe respiratory conditions is corticosteroids. These are usually given through an inhaled nebulizer treatment or intravenously. The purpose of corticosteroids is to decrease the airway inflammation associated with many respiratory disorders. Use of corticosteroids poses some risks, including increased risk of infection due to immunosuppression, and episodes of hyperglycemia, so it is important for the critical care nurse to observe patients closely for adverse effects.
Prophylactic medications are usually given daily to patients receiving ventilatory support to prevent the development of stress ulcers and deep vein thrombosis (DVT), which are common in patients receiving mechanical ventilation. Medications for stress ulcers include sucralfate (e.g., Carafate), proton pump inhibitors (PPIs), and histamine receptor blockers. DVT presents a risk for developing pulmonary emboli, which can result in respiratory complications and death. To prevent this, anticoagulants such as heparin or a low-molecular-weight heparin, such as enoxaparin (brand name, Lovenox), are administered subcutaneously.
Nursing Care
Most of the nursing care for patients in the ICU is related to care of the ETT and ventilator. First and foremost, critical care nurses are responsible for frequently monitoring ETT placement. If the tube becomes even slightly displaced, the ventilatory support being provided may not be efficient. Several times during the shift, the nurse should check the placement of the ETT to ensure it has not moved. Small markings on the ETT allow for easy visual assessment of placement at the lips. If the nurse determines that the tube may have migrated from its optimal position, it is imperative that they let the health-care provider know. It is likely that the patient will need an immediate X-ray to confirm tube placement.
Another aspect of nursing care for patients receiving mechanical ventilation is SBTs, which are overseen by the nurse and RT. SBTs involve switching the mode on the ventilator to a setting that allows for assessment of the patient taking breaths on their own. If the patient can breathe effectively in this mode and does not show any other signs of agitation or abnormal vital signs, they may be ready for removal of the ventilator and ETT. The main role of the nurse during this process is turning off the sedation and neuromuscular medications and paralytics so that the patient is fully awake and able to participate in the breathing trial process. Turning off the sedation can be startling to the patient who wakes up with an ETT in their throat, so the nurse must be present and able to communicate the process to the patient to ease their anxiety and prevent them from pulling out essential catheters and tubes. Current practices use risk assessment models such as the Richard Agitation Sedation Scale to gauge a patient’s mental status when progressing on drug holidays (Sharma et al., 2024)
Finally, prone positioning has often been used in the ICU for patients with respiratory conditions, especially those with ARDS related to COVID-19. Prone positioning entails the patient lying on their abdomen, which enables gravity to improve perfusion to more parts of the lungs. This process is highly complex, especially when patients are connected to a ventilator and other invasive equipment. Proning a patient requires the assistance of several staff members to ensure the patient can be safely positioned without disruption of their equipment and catheterss. In the past several years, there have been developments in proning beds that provide protective padding for both the patient and their equipment, and make positioning much easier. A picture of one of these beds is shown in Figure 35.11.