Hypoxaemia
Original Editor - Adam Vallely Farrell
Top Contributors - Adam Vallely Farrell, Lucinda hampton, Abbey Wright, Kim Jackson, Rishika Babburu and Chelsea Mclene
Respiratory Failure[edit | edit source]
Respiratory failure is demonstrated in arterial blood gas (ABG) tensions. Type I respiratory failure is defined as PaO2 <8.0kPa with a normal or lowered PaCO2. Type II respiratory failure (ventilatory failure) is defined as PaO2 <8.0kPa and a PaCO2 >6.0kPa. Acute respiratory failure is related to respiratory distress, with increased work of breathing and deranged gas exchange. It may occur with or without the presence of excessive pulmonary secretions and/or sputum retention., and is not necessarily related to a primary respiratory problem, e.g. neurological problems may be related to respiratory depression, hypoventilation, reduced level of consciousness and inability to protect the airway. Cough depression and risk of aspiration are a serious concern. Unrecognised respiratory failure leads to;
- respiratory muscle fatigue
- hypoventilation
- sputum retention
- Decreased O2 (hypoxaemia)
Acute assessment to establish the underlying cause is imperative as, if left untreated, it may progress to any or all of the following;
- cardiac arrhytmia
- cerebral hypoxaemia
- respiratory acidosis
- coma
- cardiorespiratory arrest
Thus, timely recognition and treatment of respiratory failure is of the utmost importance and a serious part of a patients care.
Hypoxaemia (Type 1 Respiratory Failure)[edit | edit source]
Hypoxaemia is defined as the inability to maintain the PaO2 above 8kPa
Classification and Causes of Hypoxaemia[edit | edit source]
Classification | Cause | |
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Hypoxic hypoxaemia |
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Ischaemic hypoxaemia |
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Anaemic hypoxaemia |
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Toxic hypoxaemia |
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E.g. carbon monoxide poisoning, cyanide poisoning |
Clinical Signs[edit | edit source]
A patient with hypoxaemia will display some/all of the following symptoms;
- central cyanosis (blue lips, tongue)
- peripheral shut-down (cool to touch, 'cold and clammy')
- tachypnoea - increased respiratory rate (>20 beats per minute)
- low oxygen saturation (<90%)
- confusion or agitation if profound hypoxaemia, may be non compliant with treatment
Aim of Physiotherapy[edit | edit source]
To identify and treat, if appropriate, the cause of the hypoxaemia, thus aiming to increase PaO2 >8kPa while administering appropriate oxygen therapy
Treatment of Hypoxaemia[edit | edit source]
The primary treatment of hypoxaemia is controlled oxygen therapy, plus identification and treatment of the underlying cause. Patients who are unable to maintain SaO2 >90% on face mask oxygen may require additional respiratory support, either continuous positive airway pressure (CPAP) or intubation and mechanical ventilation. Patients with unilateral lung disease can be positioned in side-lying, with the unaffected lung down, to try to improve V/Q matching.
Controlled Oxygen Therapy[edit | edit source]
- Oxygen is a drug which should be prescribed for the required percentage and/or flow rate
- Usually 24-60% can be given by an oxygen mask
- 2-4L/min via nasal cannulae; however, a mask may be preferable if hypoxic and/or mouth breather
- Over 60% oxygen with persistently low sats (<90%) use a non-rebreather mask to administer constant flow of high concentration oxygen
- CPAP is useful with profound hypoxaemia once pneumothorax excluded
Humidification[edit | edit source]
- Consider cold or heated humidification
- Heated is better for tenacious secretions or severe bronchospasm
Treat the cause, e.g. bronchospasm, sputum retention, volume loss[edit | edit source]
- If primary respiratory problem, treat this
- If primary problem is cardiac or renal, discuss this with the medical team
Increased work of breathing[edit | edit source]
- Use airway clearance techniques if needed
- Positioning is essential to reduce breathlessness and improve ventilation perfusion matching
- IPPB may be useful (with a high flow rate) to rest the muscles and improve efficacy of other treatments