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Recurrent Airway Obstruction (view source)
Revision as of 14:12, 11 August 2010
, 14:12, 11 August 2010Created page with "Chronic obstructive pulmonary disease (COPD) [[Image:COPD.jpg|right|thumb|100px|<small><center>COPD (Image sourced from Bristol Biomed Image Archive with permission)</center></sm..."
Chronic obstructive pulmonary disease (COPD)
[[Image:COPD.jpg|right|thumb|100px|<small><center>COPD (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:COPD scanning micrograph.jpg|right|thumb|100px|<small><center>COPD scanning electron micrograph (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Synonyms: '''Recurrent Airway Obstruction (RAO) '''(correct current terminology), "heaves", "broken wind"
*COPD is one of the most common conditions encountered in adult horses and is a major cause of loss of performance
*It is an asthma-like syndrome of the bronchioloalveolar region
*The aetiopathogenesis of COPD is not fully understood, but is thought primarily to be caused by an immune-mediated hypersensitivity response to inhaled allergens commonly found in mouldy hay or bedding and in stable dust (eg: spores from ''Faenia rectivirgula'', [[Aspergillus spp.|''Aspergillus fumigatus'']], and [[:Category:Actinomycetes|''Thermoactinomyces vulgaris'']])
*The immune reaction is considered primarily to be a type III hypersensitivity (antigen-antibody complex mediated)
**Type I and type IV hypersensitivity reactions may also play a role
*Repeated episodes of inflammation in the lower airways, especially the bronchioles, results in chronic changes that cause obstruction of the lower airways, sometimes followed by [[Lungs Ventilation - Pathology#Emphysema|alveolar emphysema]]
*The histological features are what you would predict given this pathogenesis:
**Luminal accumulation of exudate made up of thick mucus (goblet cell metaplasia), [[Neutrophils|neutrophils]] and cellular debris
**This can predispose to, and is often accompanied by, secondary bacterial infection eg: ''[[Streptococcus equi subsp. zooepidemicus]]''
**Thickened mucosa - epithelial hyperplasia, chronic inflammatory cell infiltrate with variable numbers of eosinophils in the airway wall
**Peribronchiolar fibrosis
**Bronchospasm
*When susceptible horses are exposed to inhaled allergens they develop airway inflammation and respiratory dysfunction
*Typically, susceptible horses are clinically normal when at pasture, but develop signs of disease shortly (hours to days) after being housed
*Clinical signs are what you would predict from a chronic inflammatory process in the airways:
**Coughing (following activation of coughing reflexes due to inflammation in the airways, mechanical pressure on the airway walls associated with the accumulation of intraluminal exudate)
**Nasal discharge (usually bilateral - mucopurulent tracheal exudate on bronchoscopy)
**Increased respiratory rate (compensation for reduced tidal volume following the reduction in airway lumen diameter)
**Pronounced effort during inspiration with an obvious abdominal component (may result in a "heave-line" in the flank due to hypertrophy of the abdominal muscles - reduced airway diameter results in increased resistance to air flow, so more inspiratory effort required for same airflow rates)
**Wheezing and crackling lung sounds on auscultation at the end of inspiration and expiration - caused by bubbles in mucus collapsing
[[Category:Allergic Respiratory Diseases]]
[[Category:To Do - Blood]]
[[Category:Horse]]
[[Image:COPD.jpg|right|thumb|100px|<small><center>COPD (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
[[Image:COPD scanning micrograph.jpg|right|thumb|100px|<small><center>COPD scanning electron micrograph (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Synonyms: '''Recurrent Airway Obstruction (RAO) '''(correct current terminology), "heaves", "broken wind"
*COPD is one of the most common conditions encountered in adult horses and is a major cause of loss of performance
*It is an asthma-like syndrome of the bronchioloalveolar region
*The aetiopathogenesis of COPD is not fully understood, but is thought primarily to be caused by an immune-mediated hypersensitivity response to inhaled allergens commonly found in mouldy hay or bedding and in stable dust (eg: spores from ''Faenia rectivirgula'', [[Aspergillus spp.|''Aspergillus fumigatus'']], and [[:Category:Actinomycetes|''Thermoactinomyces vulgaris'']])
*The immune reaction is considered primarily to be a type III hypersensitivity (antigen-antibody complex mediated)
**Type I and type IV hypersensitivity reactions may also play a role
*Repeated episodes of inflammation in the lower airways, especially the bronchioles, results in chronic changes that cause obstruction of the lower airways, sometimes followed by [[Lungs Ventilation - Pathology#Emphysema|alveolar emphysema]]
*The histological features are what you would predict given this pathogenesis:
**Luminal accumulation of exudate made up of thick mucus (goblet cell metaplasia), [[Neutrophils|neutrophils]] and cellular debris
**This can predispose to, and is often accompanied by, secondary bacterial infection eg: ''[[Streptococcus equi subsp. zooepidemicus]]''
**Thickened mucosa - epithelial hyperplasia, chronic inflammatory cell infiltrate with variable numbers of eosinophils in the airway wall
**Peribronchiolar fibrosis
**Bronchospasm
*When susceptible horses are exposed to inhaled allergens they develop airway inflammation and respiratory dysfunction
*Typically, susceptible horses are clinically normal when at pasture, but develop signs of disease shortly (hours to days) after being housed
*Clinical signs are what you would predict from a chronic inflammatory process in the airways:
**Coughing (following activation of coughing reflexes due to inflammation in the airways, mechanical pressure on the airway walls associated with the accumulation of intraluminal exudate)
**Nasal discharge (usually bilateral - mucopurulent tracheal exudate on bronchoscopy)
**Increased respiratory rate (compensation for reduced tidal volume following the reduction in airway lumen diameter)
**Pronounced effort during inspiration with an obvious abdominal component (may result in a "heave-line" in the flank due to hypertrophy of the abdominal muscles - reduced airway diameter results in increased resistance to air flow, so more inspiratory effort required for same airflow rates)
**Wheezing and crackling lung sounds on auscultation at the end of inspiration and expiration - caused by bubbles in mucus collapsing
[[Category:Allergic Respiratory Diseases]]
[[Category:To Do - Blood]]
[[Category:Horse]]