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, 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, Glascow 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 with a \(PaCO_2\) greater than 50 and a pH less than 7.35. The patient may be hypoxic and have dropping oxygen saturations. Patients with a decreased respiratory drive, burns, salicylate (aspirin) poisoning, and hyperventilation disorders are at increased risk for respiratory failure due to respiratory alkalosis. Arterial blood gas levels for a patient with respiratory alkalosis will show a \(HCO_3\) greater than 26 and pH greater than 7.45.

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. Different types of ventilation include: volume-cycled, pressure-cycled, negative-pressure, HFJV, HFOV, CPAP, and BiPAP. Ventilation on these machines can be further manipulated.

Controlled ventilation is a setting used to provide measured, preset volume or pressure with each breath regardless of what the patient is doing. Assisted ventilation is a setting used to assist or replace a patient’s breathing pattern. The synchronized intermittent mandatory setting allows the patient to take spontaneous breaths while the ventilator also provides a set rate, volume, or pressure of other breaths. 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. CPAP and BiPAP are used as well and provide positive pressure to the patient’s lungs to ease respiration. CPAP and BiPAP settings are commonly used during mechanical ventilation weaning to “test” the patient’s ability to maintain ventilation on their own.

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. Respiratory rates can be manipulated based on the patient’s tolerated tidal volume and \(PaCO_2\) goals. In general, increasing respiration drives down \(CO_2\) retention while decreasing respiration increased \(CO_2\).

\(FiO_2\) 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%. Ventilator sensitivity triggers can be controlled to anticipate a patient’s respiratory effort and provide supportive ventilation as triggered.

To prevent barotrauma, the AACN has written guidelines in calculating and setting ventilator settings. Tidal volumes should be maintained at 8-12 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 the recommended guidelines helps to reduce overdistension of the lungs and avoid pulmonary resistance.

Weaning and ultimately discontinuing the ventilator may be a daunting task. There are three phases of this process: removal of the ventilator, extubation, and eventual removal of supportive oxygen therapy. There are specific criteria a patient must meet in order to consider weaning the ventilator. The patient must have a vital capacity of 10-15 mL/kg, maximum negative inspiratory pressure of at least -20 cm \(H2_O\), tidal volume of 7-9 mL/kg, minute ventilation around 6 L/min, less than 100 breaths/m/L, \(PaO_2\) greater than 60 mmHg, and a \(FiO_2\) less than 40%. The patient must also be able to pass a spontaneous breathing trial before extubation. Oxygen therapy following extubation may be weaned as long as the patient maintains a \(PaO_2\) of 70-100 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. CPAP stands for continuous positive airway pressure, whereas BiPAP stands for bi-level 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 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.

Specialized Ventilators

Specialized ventilators may be indicated in specific populations. The high frequency jet ventilator (HFJV) provides a gentler form of ventilation that can improve gas exchange by directing frequent, high velocity air streams into the lungs. The provided ventilation effect then pushes carbon dioxide against the walls of the alveoli, decreasing dead space and maximizing gas exchange using tidal volumes of usually 1-3 mL/kg. This is sometimes considered “panting” respirations. HFJV ventilation reduces barotrauma. It may be used in conditions including progressive chronic lung disease, hypoxemic respiratory failure, pulmonary interstitial emphysema, and bronchopulmonary dysplasia.

Another form of high frequency ventilation is the high frequency oscillatory ventilator (HFOV). The HFOV can provide ventilation around 150 breaths per minute. This ventilator can be used on patients with increased pulmonary dead space. The ventilator works by keeping a high pressure to the lungs and then oscillating the alveoli with the ventilation breaths. It reduces pulmonary vascular resistance and improves V/Q mismatch. Due to its gentler nature, like the HFJV, the HFOV causes less lung injury and reduces the risk of barotrauma. Patients with respiratory distress syndrome and persistent pulmonary hypertension may be candidates for HFOV. HFOV is also used more frequently in infants in children.

Nursing Considerations

There are many things to consider when a nurse is caring for a ventilated patient. Nurses should perform frequent respiratory assessments to note any changes in or absence of breath sounds, cardiac function, and neurologic status. Frequent oral care, usually every four hours, should be provided to prevent ventilator-acquired pneumonia. Perform endotracheal or tracheostomy suctioning as needed and do so 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.

Nurses are partially responsible for checking the placement of the endotracheal tube. This can be done by 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 \(CO_2\) (\(ETCO_2\)) has proven appropriate placement. Nurses should ensure that the numbers on the tube (usually measured at the level of the teeth) are in the correct place.

Continuous \(ETCO_2\) 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.

Patient positioning helps to improve and decrease the risk for complications of ventilation. 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. Using sequential devices or TED hose along with antithrombotics (e.g., heparin, Lovenox®) can help to prevent the formation of deep vein thrombosis (DVT).

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 24-48 hours of intubation. Reducing sedation, when possible, helps to avoid prolonged suppression of GI motility.

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.