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Complications of Positive Pressure Ventilation

Cardiovascular System

PPV can affect circulation because of the transmission of increased mean airway pressure to

the thoracic cavity.

With increased intrathoracic pressure, thoracic vessels are compressed resulting in decreased

venous return to the heart, decreased left ventricular end-diastolic volume (preload),decreased CO, and hypotension. Mean airway pressure is further increased if titrating PEEP

(>5 cm H2O) to improve oxygenation.

Pulmonary System

As lung inflation pressures increase, risk ofbarotrauma increases.

o Patients with compliant lungs (e.g., COPD) are at greater risk for barotraumas.

o Air can escape into the pleural space from alveoli or interstitium, accumulate, and

become trapped causing a pneumothorax.

o For some patients, chest tubes may be placed prophylactically.

Pneumomediastinum usually begins with rupture of alveoli into the lung interstitium;

progressive air movement then occurs into the mediastinum and subcutaneous neck tissue.

This is commonly followed by pneumothorax.

Volutrauma in PPV relates to the lung injury that occurs when large tidal volumes are used

to ventilate noncompliant lungs (e.g., ARDS).

o Volutrauma results in alveolar fractures and movement of fluids and proteins into the

alveolar spaces.

Hypoventilation can be caused by inappropriate ventilator settings, leakage of air from the

ventilator tubing or around the ET tube or tracheostomy cuff, lung secretions or obstruction,and low ventilation/perfusion ratio.

o Interventions include turning the patient every 1 to 2 hours, providing chest physical

therapy to lung areas with increased secretions, encouraging deep breathing and

coughing, and suctioning as needed.

Respiratory alkalosis can occur if the respiratory rate or VT is set too high (mechanicaloverventilation) or if the patient receiving assisted ventilation is hyperventilating.

o If hyperventilation is spontaneous, it is important to determine the cause (e.g.,

hypoxemia, pain, fear, anxiety, or compensation for metabolic acidosis) and treat it.

Ventilator-associated pneumonia (VAP)is defined as a pneumonia that occurs 48 hours ormore after endotracheal intubation and occurs in 9% to 27% of all intubated patients with

50% of the occurrences developing within the first 4 days of mechanical ventilation.

o Clinical evidence suggesting VAP includes fever, elevated white blood cell count,

purulent sputum, odorous sputum, crackles or rhonchi on auscultation, and

pulmonary infiltrates noted on chest x-ray.

o Evidenced - based guidelines on VAP prevention include (1) HOB elevation at a

minimum of30 degrees to 45 degrees unless medicallycontraindicated, (2) no routine changes of the patients ventilatorcircuit tubing, and (3) the use of an ET with a dorsal lumen above

the cuff to allow continuous suctioning of secretions in thesubglottic area. Condensation that collects in the ventilator tubing should bedrained away from the patient as it collects.

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Progressive fluid retention often occurs after 48 to 72 hours of PPV especially PPV with

PEEP. It is associated with decreased urinary output and increased sodium retention.

o Fluid balance changes may be due to decreased CO.

o Results include diminished renal perfusion, the release of renin with subsequent

production of angiotensin and aldosterone resulting in sodium and water retention.

o Pressure changes within the thorax are associated with decreased release of atrial

natriuretic peptide, also causing sodium retention.o As a part of the stress response, release of antidiuretic hormone (ADH) and cortisol

may be increased, contributing to sodium and water retention.

Neurologic System

In patients with head injury, PPV, especially with PEEP, can impair cerebral blood flow.

Elevating the head of the bed and keeping the patients head in alignment may decrease the

deleterious effects of PPV on intracranial pressure.

Gastrointestinal System Ventilated patients are at risk for developing stress ulcers and GI bleeding.

Reduction of CO caused by PPV may contribute to ischemia of the gastric and intestinal

mucosa and possibly increase the risk of translocation of GI bacteria.

Peptic ulcer prophylaxis includes the administration of histamine (H2)-receptor blockers,

proton pump inhibitors, and tube feedings to decrease gastric acidity and diminish the risk of

stress ulcer and hemorrhage.

Gastric and bowel dilation may occur as a result of gas accumulation in the GI tract from

swallowed air. Decompression of the stomach can be accomplished by the insertion of anNG/OG tube.

Immobility, sedation, circulatory impairment, decreased oral intake, use of opioid pain

medications, and stress contribute to decreased peristalsis. The patients inability to exhale

against a closed glottis may make defecation difficult predisposing the patient to

constipation.

Musculoskeletal System

Maintenance of muscle strength and prevention of the problems associated with immobility

are important.

Progressive ambulation of patients receiving long-term PPV can be attained without

interruption of mechanical ventilation.

Passive and active exercises, consisting of movements to maintain muscle tone in the upper

and lower extremities, should be done in bed.

Prevention of contractures, pressure ulcers, foot drop, and external rotation of the hip and

legs by proper positioning is important.

Psychosocial Needs Patients may experience physical and emotional stress due to the inability to speak, eat,

move, or breathe normally.

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Tubes and machines may cause pain, fear, and anxiety.

Ordinary activities of daily living such as eating, elimination, and coughing are extremely

complicated.

Patients have identified four needs: need to know (information), need to regain control, needto hope, and need to trust. When these needs were met, they felt safe.

Patients should be involved in decision making as much as possible.

The nurse should encourage hope and build trusting relationships with the patient and

family.

Patients receiving PPV usually require some type of sedation and/or analgesia to facilitate

optimal ventilation.

At times the decision is made to paralyze the patient with a neuromuscular blocking agent to

provide more effective synchrony with the ventilator and increased oxygenation.

o If the patient is paralyzed, the nurse should remember that the patient can hear, see,

think, and feel.

o Intravenous sedation and analgesia must always be administered concurrently when

the patient is paralyzed.

o Assessment of the patient should include train-of-four (TOF) peripheral nerve

stimulation, physiologic signs of pain or anxiety (changes in heart rate and blood

pressure), and ventilator synchrony.

Many patients have few memories of their time in the ICU, whereas others remember vividdetails.

Although appearing to be asleep, sedated, or paralyzed, patients may be aware of their

surroundings and should always be addressed as though awake and alert.

Machine Disconnection or Malfunction

Most deaths from accidental ventilator disconnection occur while the alarm is turned off,

and most accidental disconnections in critical care settings are discovered by low-pressure

alarm activation.

The most frequent site for disconnection is between the tracheal tube and the adapter.

Alarms can be paused (not inactivated) during suctioning or removal from the ventilator and

should always be reactivated before leaving the patients bedside.

Ventilator malfunction may also occur and may be related to several factors (e.g., power

failure, failure of oxygen supply).

Patients should be disconnected from the machine and manually ventilated with 100%

oxygen if machine failure/malfunction is determined.

Nutritional Therapy: Patient Receiving Positive Pressure Ventilation

PPV and the hypermetabolism associated with critical illness can contribute to

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inadequate nutrition.

Patients likely to be without food for 3 to 5 days should have a nutritional program

initiated.

Poor nutrition and the disuse of respiratory muscles contribute to decreased

respiratory muscle strength.

Inadequate nutrition can delay weaning, decrease resistance to infection, and

decrease the speed of recovery.

Enteral feeding via a small-bore feeding tube is the preferred method to meet caloric

needs of ventilated patients.

Evidence-based guidelines regarding verification of feeding tube placement include:

(1) x-ray confirmation before initial use, (2) marking and ongoing assessment of the tubes

exit site, and (3) ongoing review of routine x-rays and aspirate.

A concern regarding the nutritional support of patients receiving PPV is the

carbohydrate content of the diet.

o Metabolism of carbohydrates may contribute to an increase in serum CO2 levels

resulting in a higher required minute ventilation and an increase in WOB.

o Limiting carbohydrate content in the diet may lower CO2 production.

o The dietitian should be consulted to determine the caloric and nutrient needs of these

patients.

Weaning from Positive Pressure Ventilation and Extubation

Weaning is the process of reducing ventilator support and resuming spontaneousventilation.

The weaning process differs for patients requiring short-term ventilation (up to 3 days)

versus long-term ventilation (more than 3 days).

o Patients requiring short-term ventilation (e.g., after cardiac surgery) will experience

a linear weaning process.

o Patients requiring prolonged PPV will experience a weaning process that consists of

peaks and valleys.

Weaning can be viewed as consisting of three phases. The preweaning, or assessment, phase

determines the patients ability to breathe spontaneously.

Weaning assessment parameters include criteria to assess muscle strength and

endurance, and minute ventilation and rapid shallow breathing index.

Lungs should be reasonably clear on auscultation and chest x-ray.

Nonrespiratory factors include the assessment of the patients neurologic

status, hemodynamics, fluid and electrolytes/acid-base balance, nutrition, and

hemoglobin.

Drugs should be titrated to achieve comfort without causing excessive

drowsiness.

o Evidenced-based clinical guidelines recommend a spontaneous breathing trial (SBT)

in patients who demonstrate weaning readiness, the second phase. An SBT should be at least 30 minutes but no longer than 120 minutes and

may be done with low levels of CPAP, low levels of PS or a T piece.

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Tolerance of the trial may lead to extubation but failure to tolerate a SBT

should prompt a search for reversible factors and a return to a nonfatiguing

ventilator modality.

The use of a standard approach for weaning or weaning protocols have shown to decrease

ventilator days.

Weaning is usually carried out during the day, with the patient ventilated at night in a rest

mode.

The patient being weaned and the family should be provided with explanations regarding

weaning and ongoing psychologic support.

The patient should be placed in a sitting or semirecumbent position and baseline vital signs

and respiratory parameters measured.

During the weaning trial, the patient must be monitored closely for noninvasive criteria that

may signal intolerance and result in cessation of the trial (e.g., tachypnea, tachycardia,

dysrhythmias, sustained desaturation [SpO2