Respiratory failure Flashcards
Define respiratory failure
The term ‘respiratory failure’ is used when pulmonary gas exchange fails to maintain normal arterial oxygen and carbon dioxide levels.
How is respiratory failure classified?
Its classification into types I and II is defined by the absence or presence of hypercapnia (raised Pa CO2 ).
Acute and Chronic forms.
What is type 1 respiratory failure?
Hypoxia with normocapnia (normal concentrations of CO2 in the blood).
What is type 2 respiratory failure?
Hypoxia with hypercapnia (elevated concentrations of CO2 in the blood).
What can cause acute type 1 respiratory failure?
Acute asthma Pulmonary oedema Pneumonia Lobar collapse Pneumothorax Pulmonary embolus ARDS
What can cause chronic type 1 respiratory failure?
COPD
Lung fibrosis
Lymphangitic carcinomatosis
Right-to-left shunts
What can cause acute type 2 respiratory failure?
Acute severe asthma Acute exacerbation of COPD Upper airway obstruction Acute neuropathies/paralysis Narcotic drugs Primary alveolar hypoventilation Flail chest injury
Any disease that reduces total ventilation. The latter includes not just diseases of the lung but also disorders affecting any part of the neuromuscular mechanism of ventilation.
What can cause chronic type 2 respiratory failure?
COPD Sleep apnoea Kyphoscoliosis Myopathies/muscular dystrophy Ankylosing spondylitis
Any disease that reduces total ventilation. The latter includes not just diseases of the lung but also disorders affecting any part of the neuromuscular mechanism of ventilation.
How is respiratory failure type 1 managed?
Prompt diagnosis and management of the underlying cause.
Give oxygen.
How is acute respiratory failure type 2 managed?
Acute type II respiratory failure is an emergency requiring immediate intervention.
In all such cases, high-concentration (e.g. 60%) oxygen should be administered, pending a rapid examination of the respiratory system and measurement of arterial blood gases.
In cases of an inhaled foreign body, heimlich / tracheostomy.
What is important to distinguish when assessing type 2 acute respiratory failure?
It is useful to distinguish between patients with high ventilatory drive (rapid respiratory rate and accessory muscle recruitment) who cannot move sufficient air, and those with reduced or inadequate respiratory effort. In the former, particularly if inspiratory stridor is present, acute upper airway obstruction from foreign body inhalation or laryngeal obstruction (angioedema, carcinoma or vocal cord paralysis) must be considered, as the Heimlich manoeuvre, immediate intubation or emergency tracheostomy may be life-saving.
If a tension pneumothorax is causing respiratory failure what is the treatment?
Patients with the trachea deviated away from a silent and resonant hemithorax are likely to have tension pneumothorax, and air should be aspirated from the pleural space and a chest drain inserted as soon as possible.
How should patients with generalised wheeze, scanty breath sounds bilaterally or a history of asthma or COPD be treated?
Salbutamol 2.5 mg nebulised with oxygen, repeated until bronchospasm is relieved.
Failure to respond to initial treatment in cases of respiratory failure indicates what?
Failure to respond to initial treatment, declining conscious level and worsening respiratory acidosis (H + > 50 nmol/L (pH 6.6 kPa (50 mmHg)) on blood gases are all indications that supported ventilation is required.
In patients with acute type 2 respiratory failure whom have a reduced conscious level what should you consider?
Patients with acute type II respiratory failure who have reduced drive or conscious level may be suffering from sedative poisoning, CO 2 narcosis or a primary failure of neurological drive (e.g. following intracerebral haemorrhage or head injury).
History from a witness may be invaluable, and reversal of specific drugs with (for example) opiate antagonists is occasionally successful, but should not delay intubation and supported mechanical ventilation in appropriate cases.
What is the most common cause of type 2 chronic respiratory failure?
The most common cause of chronic type II respiratory failure is severe COPD.
How is acute on chronic type II respiratory failure treated?
The principal aims of treatment in acute on chronic type II respiratory failure are to achieve a safe Pa O 2 (> 7.0 kPa (52 mmHg)) without increasing Pa CO 2 and acidosis, while identifying and treating the precipitating condition.
Explain how giving oxygen cause respiratory depression?
A small percentage of patients with severe chronic COPD and type II respiratory failure develop abnormal tolerance to raised Pa CO2, and may become dependent on hypoxic drive to breathe. In these patients only, lower concentrations of oxygen should be used to avoid precipitating worsening respiratory depression. In all cases, regular monitoring of arterial blood gases is important to assess progress.
What are the signs of CO2 retention?
Warm periphery, bounding pulses, flapping tremor.
What are the signs of airway obstruction?
Wheeze, prolonged expiration, hyperinflation, intercostal indrawing, pursed lips
Cor pulmonale
The abnormal enlargement of the right side of the heart as a result of disease of the lungs or the pulmonary blood vessels.
In cases of respiratory failure what investigations are carried out?
- Arterial blood gases (severity of hypoxaemia, hypercapnia, acidaemia, bicarbonate)
- Chest X-ray
NIV
Non-invasive ventilation
Why is acidosis not seen in cases of CO2 retention?
Renal compensation - kidney’s retain bicarbonate balancing the acidosis.
