Ventilation assistance

Definition

Ventilation assistance includes a variety of methods designed to help restore or improve breathing function in patients who are unable to adequately breathe on their own. These methods range from at-home oxygen therapy for patients with chronic obstructive pulmonary disease (COPD) to mechanical ventilation for patients with acute respiratory failure . Ventilation assistance therapies usually include the following categories:

• oxygen therapy
• continuous positive airway pressure (CPAP)
• hyperbaric oxygen therapy
• mechanical ventilation
• newborn life support

Purpose

Ventilation assistance is used for disease or injury that causes progressive or sudden respiratory failure. It may also be used after surgery until patients recover enough to breathe adequately on their own. Physicians choose the therapy based on the type and stage of the disease process, as well as on the results of blood and pulmonary function tests that indicate the oxygenation status of the patient.

Oxygen therapy

Home oxygen therapy is commonly ordered for patients with COPD, and is usually started when a patient's pulse oximetry (amount of hemoglobin saturated with oxygen) is below 90% on room air. Oxygen therapy is also used in the hospital to support a patient's respiratory status after illness, injury, or surgery.

Continuous positive airway pressure (CPAP)

One of the most common uses of CPAP is for patients with sleep apnea. It may also be used for both infants and adults with respiratory distress syndrome , collapse of lung tissue (atelectasis), or abnormalities of the lower airways.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy is used when there is an immediate need for greater blood oxygen saturation. Divers with decompression sickness (the bends), climbers with altitude sickness, patients suffering from severe carbon monoxide poisoning , and children or adults in acute respiratory distress may require hyperbaric oxygenation. In recent years, physicians have also used this therapy to assist in burn and wound healing, since the pressure under which the oxygen is delivered can reach areas that have an inadequate blood supply under normal conditions.

Mechanical ventilation

Mechanical ventilation is used for patients with acute respiratory distress, temporarily after surgery, or while sedated or pharmacologically paralyzed. Most patients can be weaned off of mechanical ventilation and resume breathing on their own. Some patients require long-term mechanical ventilation (i.e., quadriplegia) and, in some cases, mechanical ventilation is considered life-support for patients who would otherwise die.

Newborn life support

Newborn babies, particularly those who are born premature, may require ventilation assistance immediately after birth, since their lungs may not be fully developed. Some newborns may have serious respiratory problems or complications from birth, such as respiratory distress syndrome, neonatal wet lung syndrome, apnea of prematurity, or persistent fetal circulation (delayed closure of the ductus arteriosis and foramen ovale).

Precautions

Ventilation assistance can be beneficial during acute illness and it may provide a higher quality of life if the patient has end-stage COPD. However, oxygen is not a benign substance, and precautions must be used with any of these therapies.

Oxygen therapy

Oxygen is an extremely flammable gas, so patients who smoke should not have oxygen therapy prescribed. If there are family members who smoke, they must avoid smoking in the area of oxygen use.

Continuous positive airway pressure (CPAP)

Although CPAP can be very helpful in alleviating the symptoms of sleep apnea, it can also be uncomfortable because patients must wear a tight-fitting mask over their nose and the oxygen is pushed into their airway with considerable force. Patients who are unable or unwilling to comply with the physician's instructions regarding the use of CPAP are not likely to have it prescribed.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy involves administering 100% oxygen at three times the normal atmospheric pressure. This creates a high risk for fire and explosive decompression, as well as a risk for pulmonary and neurological toxicity. The benefits must be weighed against the potential complications. All patients, particularly children, must be carefully monitored while in the hyperbaric chamber.

Mechanical ventilation

The use of mechanical ventilation can cause pulmonary damage from high pressures. It is often frightening for patients because they are hooked up to an endotracheal or tracheostomy tube that prevents them from speaking and may make them feel like they are breathing through a straw. Usually, patients require sedation or even pharmacological paralysis to prevent accidental removal of the tube and to keep them from fighting against the ventilator.

Newborn life support

Not all infants with breathing problems require mechanical ventilation. The physician makes the determination based on the maturity and respiratory condition of the infant. Bronchopulmonary dysplasia is a chronic pulmonary disease that can develop in premature infants from high pressures and high oxygen levels delivered during mechanical ventilation.

Description

Oxygen therapy

Supplemental oxygen may be ordered for a patient who has pulse oximetry values below 90% on room air. The primary purpose of oxygen therapy is to prevent damage to vital organs caused by inadequate oxygen supply. Since there is a risk of oxygen toxicity, the lowest possible level of oxygen (measured in liters/minute) is ordered to maintain the patient's pulse oximetry at an acceptable level. The oxygen is administered via nasal cannula, mask, or tracheostomy.

Patients with chronic hypoxemia often receive longterm oxygen therapy at home. A physician must prescribe home oxygen and the patients' pulse oximetry is monitored to ensure that they are receiving the correct amount of oxygen. Some patients require oxygen therapy only at night or when exercising.

The type of home oxygen system chosen varies depending on availability, cost, and the mobility of the patient. Patients who are ambulatory, especially those who work, need a system with a small portable tank. Frequent oxygen delivery and refilling of portable tanks is necessary.

In the case of respiratory distress in both newborns and adults, oxygen therapy may be attempted before mechanical ventilation since it is noninvasive and less expensive. Oxygen is also effective in treating patients with other diseases such as cystic fibrosis , chronic congestive heart failure , or other lung diseases.

Continuous positive airway pressure (CPAP)

Sleep apnea is caused by the collapse of the upper airway. CPAP administers a constant pressure during both inhalation and exhalation, which prevents a collapse. CPAP is usually administered through a tight-fitting mask as humidified oxygen. (When CPAP is administered through an endotracheal or tracheostomy tube, it is not used for sleep apnea). Patients receiving CPAP in a hospital setting must have continuous vital sign monitoring, along with periodic sampling of blood gas values.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy delivers pure oxygen under pressure that is three times that of normal atmospheric pressure. This treatment is especially effective for treating decompression sickness in scuba divers. The oxygen is delivered inside of a plastic cylinder-shaped chamber that is large enough for the patient to lie down in. The therapy usually lasts one hour, although it can take up to five hours. Before the patient exits the chamber, the pressure is gradually lowered back to normal atmospheric level.

Mechanical ventilation

In general, mechanical ventilation replaces or supports the normal ventilatory lung function of the patient. Although mechanical ventilation is usually used for acute illness or injury in an intensive care setting, patients who require long-term mechanical ventilation can receive it at home under the supervision of a physician and home health agency. The patient must have a tracheostomy for long-term therapy.

There are several modes of mechanical ventilation, each offering different advantages and disadvantages. Many can be used in conjunction with one another.

CONTROL VENTILATION (CV). CV delivers the preset volume or pressure regardless of the patient's own inspiratory efforts. This mode is used for patients who are unable to initiate a breath. If it is used with spontaneously breathing patients, they must be sedated and/or pharmacologically paralyzed so they do not breathe out of synchrony with the ventilator.

ASSIST-CONTROL VENTILATION (A/C) OR CONTINUOUS MANDATORY VENTILATION (CMV). Both A/C and CMV deliver the preset volume or pressure in response to the patient's inspiratory effort, but will initiate the breath if the patient does not do so within the set amount of time. This mode is used for patients who can initiate a breath but who have weakened respiratory muscles. The patient may need to be sedated to limit the number of spontaneous breaths as hyperventilation can occur in patients with high respiratory rates.

SYNCHRONOUS INTERMITTENT MANDATORY VENTILATION (SIMV). SIMV delivers the preset volume or pressure and preset respiratory rate while allowing the patient to breathe spontaneously. The vent initiates each breath in synchrony with the patient's breaths. SIMV is used as a primary mode of ventilation as well as a weaning mode. (During weaning, the preset rate is gradually reduced, allowing patients to slowly regain breathing on their own.) The disadvantage of this mode is that it may increase the work of breathing and respiratory muscle fatigue. Breathing spontaneously through ventilator tubing has been compared to breathing through a straw.

POSITIVE-END EXPIRATORY PRESSURE (PEEP). PEEP is positive pressure that is applied by the ventilator at the end of expiration. This mode does not deliver breaths but is used as an adjunct to CV, A/C, and SIMV to improve oxygenation by opening collapsed alveoli at the end of expiration. Complications from the increased pressure can include decreased cardiac output, lung rupture, and increased intracranial pressure.

PRESSURE SUPPORT VENTILATION (PSV). PSV is preset pressure that augments the patient's spontaneous inspiration effort and decreases the work of breathing. The patient completely controls the respiratory rate and tidal volume. PSV is used for patients with a stable respiratory status and is often used with SIMV during weaning.

INTERMITTENT POSITIVE PRESSURE BREATHING (IPPB). IPPB is a form of assisted ventilation in which compressed oxygen is delivered under positive pressure into the patient's airway until a preset pressure is reached. Exhalation is passive. The cycle is repeated for the ordered number of breaths. IPPB is often used for a short time after a patient is weaned off of a ventilator to promote maximal lung expansion and to help clear secretions.

Newborn life support

Premature infants, particularly those born before the 28th week of gestation, have underdeveloped breathing muscles and immature lungs. These infants require respiratory support either by oxygen hood or through mechanical ventilation. The length of time that support is needed depends on the infant's gestational age and respiratory effort. CPAP can be delivered through a nasal or endotracheal tube by a ventilator that is specifically designed for neonates. As the infant's respiratory status improves, the ventilator can be weaned off.

Preparation

In an acute situation, preparation for any of these treatments includes gathering equipment and educating the patient and/or family about the treatment. At-home oxygen therapy or mechanical ventilation requires education and cooperation with a home health agency and respiratory therapist. Blood and pulmonary function tests are done to assist in individualizing the treatment for the patient.

Aftercare

Blood and pulmonary function tests are performed to verify that the treatment was successful or to monitor and adjust treatments if the therapy is long term. Mechanical ventilation requires frequent oral, nasal, or tracheostomy care for the area surrounding the insertion site of the breathing tube.

Complications

Ventilation assistance can be life saving, but these therapies also create their own set of complications and side effects.

Oxygen therapy

At-home oxygen therapy carries risk if patients or their families do not handle the oxygen in a safe manner. Patients and their families should not smoke near the oxygen supply and they should keep the tank and tubing away from any source that could cause electrical spark, flames, or intense heat.

Continuous positive airway pressure (CPAP)

The effectiveness of CPAP for sleep apnea may be limited if patients do not apply the mask properly or if they do not wear it while sleeping. Possible complications of CPAP include skin abrasions from the mask, nasal congestion, nasal or oral dryness, and discomfort from the pressure of oxygen delivery.

Hyperbaric oxygen therapy

Hyperbaric oxygen therapy is painless; however, the high atmospheric pressure can lead to pulmonary and neurological oxygen toxicity. As with any oxygen therapy, there is the risk of flammability or explosion.

Mechanical ventilation

One complication of mechanical ventilation may be patients' dependence on the ventilator and the inability to wean them off. The physician should carefully select the mode of ventilation and monitor each patient's progress to prevent this complication. Intubation and mechanical ventilation are frightening and uncomfortable for many patients and they may fight the ventilator. If this occurs, the patient should be sedated, and pharmacologically paralyzed if needed, to promote optimal ventilation. However, prolonged sedation and paralysis can cause complications as well. Intubation may cause irritation to the trachea and larynx, and a tracheostomy can be associated with a risk of bleeding, pneumothorax (punctured lung), local infection , and increased incidence of aspiration.

Newborn life support

Mechanical ventilation in neonates can result in bronchopulmonary dysplasia from lung injury caused by high oxygen concentrations and high pressures. It also increases the risk of infection in premature babies. Complications of PEEP or CPAP can include pneumothorax and decreased cardiac output.

Results

Oxygen therapy

In the case of COPD, oxygen therapy does not treat the disease but can prolong life, increase quality of life, and delay the onset of more serious symptoms. Effective oxygen therapy for any patient should lead to improved or sustained levels of oxygen in arterial blood.

KEY TERMS

Aspiration —Accidental suction of fluids or vomit into the respiratory system.

Endotracheal tube —Tube inserted into the trachea via either the oral or nasal cavity for the purpose of providing a secure airway and delivery of mechanical ventilation.

Hypoventilation —Reduced gas exchange in the lungs resulting in low oxygen levels and high carbon dioxide levels.

Hypoxemia —Deficient oxygen supply in the blood.

Pharmacological paralysis —Paralysis induced by medication to promote optimal mechanical ventilation.

Pneumothorax —Air in the plerual space that can exert pressure on the heart and opposite lung, leading to decreased cardiac and pleural function.

Pulse oximetry —Measure of the percent of hemoglobin saturated with oxygen.

Tracheostomy —Surgically created opening in the trachea for the purpose of providing a secure airway and long term ventilation assistance.

Continuous positive airway pressure (CPAP)

Successful CPAP should result in a reduction in periods of apnea for patients with sleep apnea. Hospitalized patients on CPAP should show improvement in blood gas values and pulse oximetry.

Hyperbaric oxygen therapy

After one or two treatments, scuba divers undergoing emergency treatment in a hyperbaric chamber should exhibit immediate improvement in oxygen levels throughout the body, regardless of blood flow restrictions. Patients receiving oxygen chamber therapy for difficult wounds may receive treatments daily for several weeks before satisfactory results are reached. Patients with carbon monoxide poisoning should show improvement in neurologic function. Results of hyperbaric oxygen therapy depend largely on how quickly the patient was transported to the chamber, as well as on the severity of the initial condition.

Mechanical ventilation

Successful mechanical ventilation should result in a gradual decrease in dependence on the ventilator, with eventual complete restoration of spontaneous respiration. A COPD exacerbation may be successfully treated with mechanical ventilation, and the patient may return to home oxygen therapy. Pediatric patients on long-term mechanical ventilation at home should demonstrate normal growth and development. Some patients in a hospital intensive care unit may be unable to breathe again without the ventilator; if the ventilator is the only thing keeping them alive, families and physicians may have to make hard decisions about continuing life support.

Newborn life support

Ventilation assistance is considered successful when the infant's respiratory rate is reduced by 30–40%, chest x ray and oxygen levels are improved, and the infant is able to breathe spontaneously.

Health care team roles

The nurse and respiratory therapist are responsible for carrying out the physician's orders for any type of ventilation assistance. The nurse monitors the patient's respiratory status and the level of effectiveness of the treatments. The respiratory therapist generally makes any ventilator changes ordered by the physician and sets up equipment required for treatment. Both the nurse and respiratory therapist are responsible for documenting their assessment of the patient's respiratory status. Both are also responsible for teaching the patient and family about the chosen treatment.

The nurse, respiratory therapist, or lab personnel may be responsible for drawing arterial blood gases , but the results are obtained by lab personnel. The nurse may need to inform the physician of the results, as changes in treatment may need to be made. The respiratory therapist often administers pulmonary function tests and reports the results to the physician.

Resources

BOOKS

Norris, June, ed. Critical Care Skills: A Nurse's Photo Guide. Springhouse, PA: Springhouse Corporation, 1996.

Porth, C. Pathophysiology: Concepts of Altered Health States. Philadelphia, PA: Lippincott, 1998.

Thelan, Lynne, et al. Critical Care Nursing: Diagnosis and Management. St. Louis, MO: Mosby, 1998.

ORGANIZATIONS

American Lung Association. 800-LUNG-USA or 800-586-4872. <http://www.lungusa.org>.

Hyperbaric Research and Treatment Center. <http://www.hyperbaricrx.com>.

Abby Wojahn, R.N., B.S.N., C.C.R.N.