Respiratory Distress and Failure

last authored: Sept 2012, David LaPierre
last reviewed:

 

 

 

Introduction

Respiratory failure is an inability of the lungs to maintain adequate exchange of gas. There are two types of respiratory failure - hypoxia (low oxygen) and hypercapnea (increased carbon dioxide). While criteria are somewhat arbitrary, pO2 under 60 mmHg or a pCO2 over 50 mmHg are often used.

 

Respiratory failure can affect healthy patients who sustain an acute event, such as trauma. However, it is common in patients who are weakened by chronic disease, such as COPD or heart failure, and then develop an infection or other exacerbating condition.

 

 

 

The Case of James B.

James is a 68 year old man who has not been to the doctor in years. He is relatively healthy, though smokes 2 packs/day. James has found himself increasingly unable to catch a breath over the course of two days, and calls an ambulance when he is unable to walk up a flight of stairs. The ambulance provides oxygen to James en route to the hospital. When he arrives, James is largely unresponsive.

• How do you immediately manage James's condition?
• What might be happening to James?

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Causes of Respiratory Failure

airway disorders COPD asthma airway obstruction (mucus, foreign body, edema) cystic fibrosis acute overwhelming lung disease pneumonia congestive heart failure (various causes) valvular heart disease aspiration pneumonitis acute respiratory distress syndrome pulmonary embolism tuberculosis lung contusion lung cancer pulmonary fibrosis pleural effusion inhaled toxins (ie chlorine gas) vascular diseases pulmonary embolism severe haemoptysis air embolism amniotic fluid embolism fat embolism Severe sepsis or septic shock, other shock chest wall disorders kyphoscoliosis chest wall trauma (rib fracture, flail chest, diaphragmatic rupture) pneumothorax abdominal distension

neuromuscular problems poliomyelitis polymyositis Guillain-Barre syndrome myasthenia gravis ALS muscular dystrophy hypoventilation spinal cord injury myxedema transverse myelitis tetanus botulism disuse atrophy central nervous system disorders respiratory centre depression (alcohol, opioids, barbiturates) encephalitis trauma brainstem stroke   increased metabolic activity fever hyperthyroidism seizure   other hypokalemia hypophosphatemia

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Pathophysiology

There are five main physiologic mechanisms that can lead to arterial hypoxia. These include:

• V/Q mismatch
• shunting (pneumonia)
• diffusion impairment
• hypoventilation
• low inspired FiO2 (altitude)

Post-operative patients experience pain, secretions, and pain medications. The most affected patients include thoracics and upper abdominal patients.

 

Closing volume is the point at which lung tissue becomes atalectatic.

Secretions (pneumonia, smoking) increase closing volume.

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Signs and Symptoms

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Investigations

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Treatments

Management should be guided by the clinical situation.

Position the patient to ensure maximal alignment of the airway.

Ensure IV access and place the patient on a monitor.

Provide oxygen to attain an oxygen saturation of 90%. Caution should be taken to avoid causing hypoventilation in patients who retain CO2 (that is, have chronic hypercapnia). However, this concern should not prevent oxygen from being given. Oxygen may be given through nasal cannula, a simple mask, or a non-rebreather. Further details are described here.

 

If the patient is otherwise stable (ie, with satisfactory blood pressure, heart rate, and level of consciousness), and are alert enough to tolerate the mask and clear secretions, non-invasive ventilation may be an option. Bilevel positive pressure ventilation is normally used.

 

If the patient has ARDS or is becoming unstable, however, intubation is required. Indications for consideration of advanced airway include:

• respiratory rate >30, or apnea
• altered mental status
• worsening fatigue
• inability to protect airway
• hypotension
• bradycardia or tachycardia

Techniques that can be used to reduce oxygen usage include sedation/paralysis, as well as cooling.

Blood transfusion can also be given to increase oxygenation.

Treat the underlying condition.

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Consequences and Course

Depending on the cause, many patients will experience a rapid reversal of their condition with appropriate management. If intubation is required, some patients may be extubated within a day or two. If lung damage is severe, however, prognosis outside of ongoing ventilatory support can be quite poor.

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Resources and References

Ray P et al. 2008. Acute respiratory failure in the elderly: diagnosis and prognosis. Age and Aging. 37(3): 251-257.

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Topic Development

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