Respiratory Study Guide for the CCRN

Intubation and Ventilator Support

Patients may need to be intubated and ventilated if their respiratory conditions lead to severe respiratory distress and failure. The body can only compensate for increasing levels of carbon dioxide or decreasing oxygen perfusion for so long. Both acute and chronic pulmonary diseases lead to the use of mechanical ventilation. Patients with severe and chronic asthma, COPD, drug overdose, Guillain−Barré, and myasthenia gravis may all require intubation in light of respiratory insufficiency. Other patients may be intubated due to traumatic injury, Glasgow Coma Scale (GCS) scores of \(8\) or less, or multi-organ distress or failure.

Nurses should monitor their patients for increasing respiratory distress, dyspnea with tachypnea, gasping, retractions, and use of accessory muscles. Arterial blood gas reading will likely show respiratory acidosis. The patient may be hypoxic and have dropping oxygen saturations. Patients with a extensive (or severe) burns, salicylate (aspirin) poisoning, and hyperventilation disorders are at increased risk for respiratory failure due to respiratory alkalosis.

If conservative measures do not improve the patient’s symptoms and reverse the patient’s respiratory failure, they will be intubated and mechanically ventilated. Intubation is the process of bypassing through the trachea to allow direct passage of oxygenated airflow to the lungs. Many patients who are acutely intubated will be intubated with an endotracheal tube. If patients are intubated for an extended period of time or need continued ventilator support, a temporary or permanent tracheostomy tube may be considered.

Ventilator Settings

There are several types of ventilators and ventilator settings that may be used in acute care units. These can be adapted to best fit the patient’s needs.

Controlled mechanical/mandatory ventilation (CMV) is a setting used to provide measured, preset volume or pressure with each breath regardless of what the patient’s respiratory efforts are doing. This is typically used in a completely apneic or fully sedated and paralyzed patient.
Assist-control (AC) ventilation is a setting used to assist or replace a patient’s breathing pattern. This is the most common initial mode a ventilator is set to. This mode delivers a fixed tidal volume for every breath whether timed or spontaneously triggered. In other words, patients can trigger a breath, but the ventilator does all the work.
The synchronized intermittent mandatory ventilation (SIMV) setting allows the patient to take spontaneous breaths while the ventilator also provides a set rate, volume, or pressure of other breaths. This mode delivers a variable tidal volume and the patient is doing all the work on all spontaneous breaths.This mode is not ideal for those who need ventilatory muscle rest. This mode was created for purposes of weaning, but it is not as commonly used for that anymore. The benefits to this mode are decreased risk of barotrauma and hyperventilation. However, the patient must be able to maintain adequate tidal volumes on spontaneous breaths. Another rationale clinicians may use to support this mode is that it is thought to decrease respiratory muscle atrophy.
Pressure support ventilation (PSV) is a setting used to provide extra pressure during inspiration. There is no set tidal volume or respiratory rate; however, the extra pressure does help increase tidal volumes. This is a fully spontaneous mode and is the most commonly used setting determining if the patient can come off the ventilator.

Other ventilator settings will also be used to maximize the therapy and performance of mechanical ventilation for the patient.

Tidal volumes (TV) will be set to allow measured amounts of air into the lungs with each breath. Tidal volume in a normal healthy adult is around 500 mL.
Respiratory rates (frequency) can be manipulated based on the patient’s tolerated tidal volume and \(\text{PaCO}_2\) goals. In general, increasing respiration drives down \(\text{CO}_2\) retention while decreasing respiration increases \(\text{CO}_2\).
\(\text{FiO}_2\) or the fraction of inspired oxygen is a measure of how much oxygen is present in the inspired air. Oxygen toxicity can occur with levels higher than \(40\%\); however, most mechanical ventilators can provide oxygen concentrations from \(21\%\) to \(100\%\). For reference, the FiO2 in room air is 21% and for every supplemental liter, FiO2 increases by about 4%.
Positive-end expiratory pressure (PEEP) allows the patient to spontaneously breathe while supporting or maintaining a constant pressure to alleviate stress on the alveoli by avoiding full decompression of the structures.
Ventilator sensitivity triggers can be controlled to anticipate a patient’s respiratory effort and provide supportive ventilation as triggered.
Ventilator alarms signal critical issues such as abnormal pressures, inadequate volumes, or even issues with the machine itself such as low oxygen supply.
High pressure alarms indicate that the pressure in the circuit is too high. The most common causes are anything that increases resistance such as when the patient is biting, coughing, gagging, or otherwise fighting the ventilator. Other reasons could be a bronchospasm or secretions blocking ventilation as well as a kink in the tubing.
Low pressure alarms indicate that the pressure in the circuit is too low or has decreased resistance. This could mean the tubing has disconnected, the ET tube cuff has a leak, or the breathing tube has been removed by the patient.
If the patient is on a mode that allows for spontaneous breaths, various alarms can be set for high/low respiratory rate, high/low volumes, apnea, and more depending on the type of ventilator and mode it is set to.

It is essential that nurses review these alarm parameters for each ventilated patient. Parameters can be adjusted based on the patient’s condition but should always maintain safety without contributing to unnecessary alarm fatigue .

To prevent barotrauma (tissue damage), tidal volumes should be maintained at \(8\) to \(12\) mL/kg PBW for the majority of patients. In patients with ARDS, volumes less than \(6\) mL/kg may be considered to avoid lung injury. Keeping these settings within this range helps to reduce overdistension of the lungs and avoid pulmonary resistance.

Weaning from the Ventilator

Weaning and ultimately discontinuing the ventilator may be a daunting task. There are three phases of this process:

removal of the ventilator
extubation
eventual removal of supportive oxygen therapy

There are specific criteria a patient must meet in order to consider weaning the ventilator. Every facility and physician has different guidelines, but generally speaking, the patient must have the following:

an intact neurological status and good protective reflexes (e.g., cough, gag)
hemodynamic stability
an ability to breathe spontaneously and maintain adequate tidal volumes
an Fio2 less than 40 to 50% and PEEP less than 8 cmH2O
ensurance that the condition that led to the need of ventilatory support has been treated

The patient must also be able to pass a spontaneous breathing trial (SBT) before extubation. This includes placing them on minimal ventilatory support (as we discussed often in PSV mode) and stopping any sedating/paralyzing medications.This assesses the patient’s ability to breathe independently for 30 to 120 minutes before the ventilator is removed. If the patient cannot maintain oxygen saturations, has bradypnea, tachypnea, or any signs of respiratory distress, the trial should be discontinued immediately. If the patient fails the trial, the ventilator settings are changed back to what they were previously, and it is often repeated again the following day.

Another assessment tool is the cuff leak test (CLT). This involves deflating the ET tube cuff and checking for an air leak. This is primarily used for predicting the risk of upper airway obstruction post extubation. A passed CLT means there was an air leak present and suggests lower risk of reintubation. A failed CLT means there was not an air leak present and suggests a higher risk of reintubation. Supplemental oxygen should be applied following extubation and patients should be monitored closely. Oxygen therapy following extubation may be weaned as long as the patient maintains a \(\text{PaO}_2\) of \(70\) to \(100\) mmHg on room air.

Non-Invasive Ventilators

Non-invasive ventilation can be provided by a tight-fitting nasal or face mask. These ventilators provide positive pressure air to help prevent the full collapse of the alveoli, thus improving ventilation and decreasing the patient’s work of breathing. The two most common types of non-invasive ventilation include CPAP and BiPAP. These can be used to manage patients chronically such as in obstructive sleep apnea or in critically ill patients that need pressure support.

CPAP stands for continuous positive airway pressure. In CPAP, a continuous stream of pressurized air is administered to the patient throughout the breathing cycle. It helps to reduce preload volumes in congestive heart failure and increases the patient’s residual lung volume to improve oxygenation.
BiPAP stands for bi-level positive airway pressure. BiPAP also provides constant pressurized air, but as the patient begins to inspire, the pressure increases further to support the ventilatory effort. A backup rate may be programmed in this machine to ensure the patient is receiving a minimum amount of breaths.

Nursing considerations for non-invasive ventilators include continuing to monitor for respiratory decompensation, ensuring an appropriate fit of the mask, reducing skin breakdown around the mask, and helping provide facial hygiene. Patients with non-invasive ventilation should not be restrained so they have the ability to remove the mask if needed.

Nursing Considerations

There are many things to consider when a nurse is caring for a ventilated patient. Nurses should always speak to ventilated and sedated patients just as they would any other patient. Also they must take into consideration the emotional burden a critically ill patient has on family members. To support family, nurses can validate their experience, communicate clearly, and encourage gentle participation.

Preventing Complications

One of the main concerns with ventilated patients is the development of ventilator-associated pneumonia (VAP). A lot of the interventions listed not only keep the patient comfortable, but also reduce the risk of infection including oral care, positioning, early mobility, and extubation as soon as possible. Nurses should perform frequent respiratory assessments to note any changes in or absence of breath sounds, cardiac function, and neurologic status. Perform frequent oral care, usually every four hours, and endotracheal or tracheostomy suctioning, as needed and correctly (only suctioning while withdrawing the catheter and avoiding extensive or excessively deep suctioning), to prevent trauma. Also ensure the patient has appropriate ventilator settings to prevent barotrauma and pneumothorax events.

Using sequential devices or TED hose along with antithrombotics (e.g., heparin, Lovenox®) can help to prevent the formation of deep vein thrombosis (DVT). Perform passive range of motion and encourage active range of motion exercises once the patient is able to follow commands to promote mobilization.

Tube Placement

Nurses are partially responsible for checking the placement of the endotracheal tube. This can be done through a couple different practices. Many tubes will be taped or secured at a certain number after previous confirmation via either X-ray or end-tidal \(\text{CO}_2\) (\(\text{ETCO}_2\)) has proven an appropriate placement. Nurses should ensure that the numbers on the tube (usually measured at the level of the teeth or lips) are in the correct place. Securement devices can increase the risk of pressure injuries so ensure they are not too tight, gently change the positioning to reduce pressure, and use preventative dressings as needed.

Continuous \(\text{ETCO}_2\) readings can be used to monitor for significant changes in tube placement. If ever in doubt, the nurse can work with the prescribing provider to have an X-ray to confirm the placement of the endotracheal tube.

Positioning the Patient

Patient positioning helps to improve ventilation effects and decrease the risk for complications. Elevate the patient’s head to a minimum of \(30\) degrees to prevent aspiration and pneumonia. To prevent skin breakdown and to help mobilize secretions, turn or reposition patients every two hours. Some patients may benefit from prone positioning as discussed earlier in this guide.

Nutrition

Mechanical ventilation can also put great stress on the GI system, so famotidine or pantoprazole should be considered to prevent ulcers and bleeding. Nutrition should be assessed early in the event of mechanical ventilation. Research has shown improved outcomes for patients who have had initiation of enteral nutrition within 24 to 48 hours of intubation. This is generally through an orogastric (OG) or nasogastric (NG) tube. Reducing sedation, when possible, helps to avoid prolonged suppression of GI motility.

Sedation

In general, patients should be on the least amount of sedation necessary for their condition. Very deep sedation has been shown to decrease patient outcomes and lead to ICU-acquired delirium. This is a very common condition that causes sudden and fluctuating changes in mental status including confusion, disorganized thinking, and inattention.

The Richmond Agitation-Sedation Scale (RASS) is an assessment tool to assess the alertness of a patient. The typical goal for a nonparalyzed ventilated patient is a RASS score of 0 to -2.

1 Richmond Agitation-Sedation Scale (RASS).png

Length of Intubation

Ultimately, the quicker the patient returns to normal pulmonary function, the less risk they have for complicating factors. Daily spontaneous breathing trials should be initiated to assess patient readiness for discontinuation of mechanical ventilation. Furthermore, prevention of unnecessary intubation is key by utilizing less invasive options first and ventilatory support as the last resort.