Acute Respiratory Failure in the Patients with COPD

Individuals with chronic obstructive pulmonary disease are at high risk for the development of acute respiratory failure. Altered host defenses, increased secretions volume and viscosity, impaired secretion clearance and airway changes and common pathophysiologic changes predispose patients with COPD to frequent episodes of ARF. The etiology, clinical presentation and management of COPD patients vary somewhat from ARF without chronic underlying pulmonary dysfunction.

The anatomic changes in COPD

Etiology, Risk Factors, and Pathophysiology

Any systemic or pulmonary illness can precipitate ARF in patients with COPD. Precipitating events of acute respiratory failure in COPD include decreased ventilator drive, decreased muscle strength such as with malnutrition and shock, decreased chest wall elasticity such as in patients rib fractures and pleural effusion, decreased lung capacity for gas exchange, increased airway resistance, and increased metabolic oxygen requirements. In addition to the etiologies of ARF, diseases as well as situations that decrease ventilator drive, muscle strength, chest wall elasticity, or gas exchange capacity, or increase airway resistance or metabolic oxygen requirements can easily lead to ARF in patients with COPD.  The most common precipitating events include:

1. Airway infection. Frequent antibiotic administration, hospitalization, and impaired cough and host defenses in COPD increase acute airway infections. Infections are commonly caused by gram-negative enteric bacteria or Legionella, with Haemophilus influenza and Streptococcus pneumonia causing bronchitis.
2. Pulmonary embolus. The high incidence risk of right ventricular failure in COPD increases the risk of pulmonary embolus from right ventricular mural thrombi.
3. Heart failure. In the presence of pulmonary hypertension and right sided heart failure, treatment of left-sided heart failure is often delayed because of difficulties in early diagnosis.
4. Noncompliance with medication regime. The complicated treatment regimen in the management of COPD which includes frequent administration of both oral and inhaled agents, frequently leads to the under use of medications.

The development of ARF in patients with COPD places a tremendous burden on the pulmonary system. The chronic disease process leads to the impairment of ventilation, poor gas exchange, and airway obstruction. The additional burden of acute disease process, even relatively a minor one, further impairs ventilation and gas exchange and increases airway obstruction.

The signs and symptoms are ARF includes:

• Hypoxemia (PaO₂ <60 mmHg)
• Restlessness
• Tachypneas
• Dyspnea
• Tachycardia
• Confusion
• Diaphoresis
• Anxiety
• Hypercabia (PaCO₂ >50 mmHg)
• Hypertension
• Irritability
• Somnolence (late sign)
• Cyanosis (late sign)
• Loss of consciousness  (late sign)
• Pallor or cyanosis of the skin
• Use of accessory muscles of respiration
• Abnormal breath sounds

Principles of Management for ARF in Patient with COPD

Treat the Underlying Disease state

Treatment is directed at both the acute precipitating event and the chronic airway obstruction problems associated with COPD.

1. Bronchodilators and corticosteroids are usually used to increase the airway diameter and reduce airway edema respectively. Higher than usual doses may be necessary until the precipitating event is resolved. However, brochospasm that is refractory to bronchodilators in severe asthma cases may require subcutaneous epinephrine administration.
2. Antibiotics to treat pulmonary infections
3. Improve secretion removal by adequate hydration, corticosteroids, coughing, heated moist aerosolization and chest physiotherapy.

Improving oxygenation and ventilation

1. Correction of hypoxemia by small increases in FiO₂ levels, preferably with a controlled oxygen delivery with devices such as a Venturi mask, biphasic intermittent positive airway (BIPAP). Arterial blood gases are frequently monitored to ensure adequate arterial oxygenation. Higher than necessary FiO₂ should be avoided since it may suppress the hypoxic ventilator drive of the COPD patient. Titration of oxygen administration should be guided by pH and PaCO₂.
2. Positioning of the patient is also necessary in maximizing ventilatory efforts and relaxation during spontaneous breathing. High Fowler position, leaning on an overbed table is often the greatest position of comfort for COPD patients prior to intubation.
3. Relaxation techniques and pursed lip breathing may be helpful to decrease anxiety and improve ventilatory patterns. Anxiolytics and other sedatives should be used cautiously.
4. Intubation and mechanical ventilation are based primarily on the deterioration of mental status coupled with knowledge of the patient's baseline pulmonary function and functional status and the reversibility of the underlying cause. Somnolence and lack of cooperation with treatments are strong indications for intubation. Weaning from the mechanical ventilation is frequently more difficult, and in some cases impossible for patients with COPD. Informed discussions with the patient and the family regarding intubation should be undertaken.

Fowler position is most ideal for COPD

Slow correction of hypercarbia should be done to avoid life threatening alkalemia from preexisting metabolic compensation. The development of auto PEEP and barotrauma is increased in patients with COPD, necessitating smaller tidal volumes, higher respiratory rates and short inspiratory and long expiratory times.

Nutritional support

Typically, patients with COPD have protein-calorie malnutrition as well as low levels of electrolytes such as phosphate, magnesium and calcium. These chronic nutritional deficits lead to muscle weakness and may interfere with the weaning process. Early enteral or parenteral feeding of these patients is essential to avoid further deterioration in their nutritional status during acute illness. Parenteral feeding may be best initially since dyspnea in non-intubated patient makes oral feeding more difficult. Lipid calories should also account for 50% of the nutritional support during mechanical ventilation.

Maintaining the body's ideal weight is likewise important as part of the nutritional goals of a patient with COPD. Good nutrition will help the body become strong against infections. Eating a healthy diet is essential for proper body weight maintenance and seeing a dietician will help you define the best nutritional plan with high consideration to your condition. Being overweight can induce more stress to both the lungs and heart which can exacerbate COPD and might increase the risk to an acute respiratory failure. On the other hand, being underweight can make the body weak and more susceptible to other diseases and infection. To keep the body strong against COPD complications, the combination of regular exercise and a healthy diet will provide the body sufficient energy and strength.

Drinking fluids of up to 6 to 8 ounces of water or non-caffeinated drinks will have a good effect in thinning the mucus which makes coughing easier and less burdensome. It is also best to avoid certain beverages that might interact with your medications like tea, caffeinated drinks, cola and other carbonated drinks. Fiber rich diet is also ideal in helping the digestion process that helps control the body glucose levels. At least 20 to 35 grams of fiber consumption each day will be adequate in supplying the fiber needs of the body.

Preventing and managing complications

Healthcare team should also monitor complications commonly observed in COPD patients:

1. Arrhythmia: high incidence of both atrial and ventricular arrhythmia in patients with COPD because of hypoxemia, acidosis, heart disease, medications and electrolyte abnormalities. Cardiac monitoring and treatment of the underlying cause is the focus and antiarrhythmic medications should be given only for life threatening situations.
2. Pulmonary embolus: observe for signs and symptoms and follow the usual treatment and prevention guidelines as this has high incidence risk
3. GI distention and ileus: very common in dyspneic patients, increasing incidence of this complication
4. Auto-PEEP and barotrauma: high incidence especially in elderly and patients with high ventilation needs.

An acute respiratory failure can become an emergency situation. In order to ensure that you are in a healthy condition, make sure to see your doctor regularly.