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Respiratory failure: Difference between revisions
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Respiration is sufficient when it is able to provide enough oxygen to and remove enough carbon dioxide from the tissues. If this is not the case, there is '''respiratory failure'''. There are two types of respiratory failure, partial and global. | Respiration is sufficient when it is able to provide enough oxygen to and remove enough carbon dioxide from the tissues. If this is not the case, there is '''respiratory failure'''. There are two types of respiratory failure, partial and global. | ||
Partial respiratory failure, also called '''hypoxaemic respiratory failure''' or type I respiratory failure, is characterised by [[hypoxaemia]] (decreased pO2) but no [[hypercapnia]] (elevated pCO2). | Partial respiratory failure, also called '''hypoxaemic respiratory failure''' or type I respiratory failure, is characterised by [[hypoxaemia]] (decreased pO2 < 60 mmHg) but no [[hypercapnia]] (elevated pCO2). | ||
Complete respiratory failure, also called '''hypercapnic respiratory failure''' or type II respiratory failure, is characterised by both hypoxaemia and hypercapnia. This is more severe and also causes [[respiratory acidosis]]. | Complete respiratory failure, also called '''hypercapnic respiratory failure''' or type II respiratory failure, is characterised by both hypoxaemia and hypercapnia. This is more severe and also causes [[respiratory acidosis]]. | ||
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=== Hypoxaemic respiratory failure === | === Hypoxaemic respiratory failure === | ||
Hypoxaemic respiratory failure occurs due to problems with gas exchange in the lungs or due to mild V/Q mismatching. This is because CO2 exchanges much more easily in the lungs than O2. | Hypoxaemic respiratory failure occurs due to problems with gas exchange in the lungs or due to mild [[Ventilation perfusion mismatch|V/Q mismatching]]. This is because CO2 exchanges much more easily in the lungs than O2. | ||
==== Impaired gas exchange ==== | |||
Impairment of gas exchange, usually due to disorder of the lungs, can cause hypoxaemic respiratory failure. | |||
* [[Interstitial lung disease]] | |||
* [[Emphysema]] | |||
==== Mild V/Q mismatching ==== | |||
Ventilation/perfusion mismatching can cause hypoxaemic respiratory failure, but if severe enough, hypercapnic respiratory failure occurs. | |||
* Too high V/Q ratio (not enough perfusion compared to ventilation) | |||
** [[COPD]] | |||
** [[Bronchiectasis]] | |||
** [[Pulmonary hypertension]] | |||
** [[Interstitial lung disease]] | |||
* Too low V/Q ratio (not enough ventilation compared to perfusion) | |||
** [[Pneumonia]] | |||
** [[Pulmonary oedema]] | |||
** [[Acute respiratory distress syndrome]] | |||
** Atelectasis | |||
** Pulmonary arteriovenous fistula | |||
=== Hypercapnic respiratory failure === | === Hypercapnic respiratory failure === | ||
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==== Increased dead space (V/Q mismatch) ==== | ==== Increased dead space (V/Q mismatch) ==== | ||
Increased dead spacing occurs when there is a ventilation/perfusion mismatch (V/Q mismatch). When a part of the lung receives no perfusion, the alveoli in the area effectively become dead space (due to not having blood to exchange gas to). This can occur in case of: | Increased dead spacing occurs when there is a ventilation/perfusion mismatch (V/Q mismatch) where regions of the lung are not perfused. When a part of the lung receives no perfusion, the alveoli in the area effectively become dead space (due to not having blood to exchange gas to). This can occur in case of: | ||
* Pulmonary embolism (severe) | * Pulmonary embolism (severe) | ||
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==== Severe lung disease ==== | ==== Severe lung disease ==== | ||
CO2 diffuses easily across the respiratory membrane. Even so, severe lung disease can impair the respiratory membrane such that even CO2 diffusion is impaired. | CO2 diffuses easily across the respiratory membrane. Even so, severe lung disease can impair the respiratory membrane such that even CO2 diffusion is impaired. | ||
== Clinical features == | |||
Hypercapnia causes depressed consciousness. | |||