Objective—To estimate the association between climate
and airborne pollen and fungal factors and
chronic obstructive pulmonary disease (COPD) in
Sample Population—Data from 1,444 horses with a
diagnosis of COPD.
Procedure—The Veterinary Medical Database was
used to identify records of horses admitted to veterinary
teaching hospitals in the United States and
Canada between 1990 and 1999. Rainfall, mean minimum
and maximum temperature, and maximum
monthly pollen and fungal spore (mold) counts recorded
at the city closest to where the hospital is located
were identified for each month data were reported to
the Veterinary Medical Database. Associations
between climatic and aeroallergen data and monthly
prevalence of COPD were estimated by use of crosscorrelation
and logistic regression models.
Results—Significant positive correlations were found
between prevalence of COPD and rainfall 3 months
previously, minimum temperature 1 and 2 months previously,
total pollen counts measured 3 months previously,
and total mold counts measured during the
same month and 1 month previously.
Conclusions and Clinical Relevance—Outdoor
aeroallergens and climatic factors may contribute to
the occurrence of COPD in horses. (Am J Vet Res
Objective—To determine effects of syringe type and storage conditions on blood gas and acid-base values for equine blood samples.
Sample—Blood samples obtained from 8 healthy horses.
Procedures—Heparinized jugular venous blood was equilibrated via a tonometer at 37°C with 12% O2 and 5% CO2. Aliquots (3 mL) of tonometer-equilibrated blood were collected in random order by use of a glass syringe (GS), general-purpose polypropylene syringe (GPPS), or polypropylene syringe designed for blood gas analysis (PSBGA) and stored in ice water (0°C) or at room temperature (22°C) for 0, 5, 15, 30, 60, or 120 minutes. Blood pH was measured, and blood gas analysis was performed; data were analyzed by use of multivariable regression analysis.
Results—Blood Po2 remained constant for the reference method (GS stored at 0°C) but decreased linearly at a rate of 7.3 mm Hg/h when stored in a GS at 22°C. In contrast, Po2 increased when blood was stored at 0°C in a GPPS and PSBGA or at 22°C in a GPPS; however, Po2 did not change when blood was stored at 22°C in a PSBGA. Calculated values for plasma concentration of HCO3 and total CO2 concentration remained constant in the 3 syringe types when blood was stored at 22°C for 2 hours but increased when blood was stored in a GS or GPPS at 0°C.
Conclusions and Clinical Relevance—Blood samples for blood gas and acid-base analysis should be collected into a GS and stored at 0°C or collected into a PSBGA and stored at room temperature.
Objective—To determine the degree of agreement between 2 analyzers for measurement of total CO2 concentration (ctCO2) in equine plasma.
Animals—6 healthy untrained horses, 6 trained Standardbreds undergoing a simulated race protocol, and 135 trained Standardbreds at a racetrack.
Procedures—Jugular venous blood samples were obtained from all horses. Two analyzers (commonly used analyzer A and less expensive analyzer B) were used to measure plasma ctCO2 in each sample. Validation of both analyzers was conducted in accordance with guidelines established by the Clinical and Laboratory Standards Institute and involved characterization of linearity, total analytic error, and bias estimation.
Results—Total analytic error (instrument SD) was 0.58 mmol/L (coefficient of variation, 1.6%) and 0.49 mmol/L (coefficient of variation, 1.4%) for analyzers A and B, respectively, when measuring an aqueous standard containing 36.0 mmol of CO2/L. A 1 g/L decrease in plasma protein concentration corresponded to an increase in ctCO2 measured with analyzer B of 0.065 mmol/L. A difference plot indicated that analyzer B produced values 2.7% higher than analyzer A for 103 samples from the 6 trained and exercised Standardbreds (mean plasma protein concentration, 67 g/L).
Conclusions and Clinical Relevance—Analyzer B provided adequate precision and linearity for measurement of ctCO2 from 5 to 40 mmol/L and was therefore suitable for measuring ctCO2 in equine plasma, provided allowances are made for changes in plasma protein concentration.
Objective—To identify risk factors for recurrent airway
obstruction (RAO) among horses examined at
veterinary teaching hospitals in North America.
Design—Retrospective case-control study.
Animals—1,444 horses with RAO and 1,444 control
horses examined for other reasons.
Procedure—The Veterinary Medical Database was
searched for records of horses in which RAO was
diagnosed. A control group was identified by randomly
selecting a horse with a diagnosis other than RAO
that matched the institution and year of admission for
each of the horses with RAO. Information obtained
included hospital, admission year and month, age,
sex, breed, and discharge status. The association
between risk factors and diagnosis of RAO was estimated
with logistic regression models.
Results—The risk of RAO increased significantly with
age, with horses ≥ 7 years old being 6 to 7 times as
likely to have RAO as were horses ≤ 4 years old.
Thoroughbreds were 3 times as likely to have RAO as
were ponies. Horses were 1.6 and 1.5 times as likely
to be examined because of RAO during winter and
spring, respectively, than they were during summer.
Conclusions and Clinical Relevance—Results suggest
that RAO was more likely to be diagnosed in
females, horses ≥ 4 years old, and Thoroughbreds and
that RAO has a seasonal distribution. (J Am Vet Med
Objective—To evaluate the association among clinical
signs, results of cytologic evaluation of bronchoalveolar
lavage (BAL) fluid, and measures of pulmonary
function in horses with inflammatory respiratory
Animals—9 healthy horses, 5 horses with inflammatory
airway disease (IAD), and 9 horses with chronic
obstructive pulmonary disease (COPD).
Procedure—Clinical examination, lung function
tests, and BAL were performed on each horse.
Results—Standard lung mechanics of horses with
exacerbated COPD differed significantly from those
of healthy horses; however, there were few differences
among horses with IAD, horses with COPD
during remission, and healthy horses. Most variables
for forced expiration (FE) in horses with COPD or IAD
differed significantly from those for healthy horses.
Results of clinical examination had low to moderate
sensitivity and predictive values for a diagnosis of
COPD (range, 67 to 80%). Results of FE tests had
high sensitivity, specificity, and predictive values for a
diagnosis of COPD (79 to 100%), and results of standard
lung mechanics tests had low sensitivity and
predictive values (22 to 69%). Percentage of neutrophils
in BAL fluid was highly sensitive (100%) but
moderately specific (64%) for a diagnosis of COPD.
Conclusion and Clinical Relevance—Clinical examination
is moderately accurate for establishing a diagnosis
of COPD. Forced expiration tests can specifically
detect early signs of airway obstruction in horses
with COPD and IAD that may otherwise be inapparent.
Cytologic evaluation of BAL fluid allows early
detection of inflammatory respiratory disease, but it
is not specific for COPD. (Am J Vet Res 2001;62:
Objective—To determine whether administration of
glucocorticoids provides additional benefits to environmental
management of horses with recurrent airway
Animals—28 horses with RAO.
Procedure—Horses were classified as having mild,
moderate, or severe RAO. Within each category,
horses were randomly assigned to receive inhaled
fluticasone propionate, inhaled control substance,
or oral administration of prednisone. During the 4-
week study, horses were maintained outdoors and
fed a pelleted feed. Clinical scores, pulmonary function,
results of cytologic examination of bronchoalveolar
lavage fluid (BALF), and adrenal gland
function were determined before and 2 and 4
weeks after initiation of treatment.
Results—Clinical score and pulmonary function of all
RAO-affected horses improved during the treatment
period. After 4 weeks, clinical scores and pulmonary
function of horses treated with a glucocorticoid were
not different from those for the control treatment. In
horses with severe RAO, treatment with fluticasone
for 2 weeks resulted in significantly greater improvement
in pulmonary function, compared with pulmonary
function after treatment with prednisone or
the control substance. Treatment with a glucocorticoid
for 4 weeks and a low-dust environment did not have
any effect on cellular content of BALF. Treatment with
prednisone for 2 weeks resulted in a significant
decrease in serum cortisol concentration, compared
with concentrations after administration of fluticasone
or the control substance.
Conclusions and Clinical Relevance—Environmental
management is the most important factor in
the treatment of horses with RAO. Early treatment
with inhaled fluticasone can help accelerate recovery
of horses with severe RAO. (Am J Vet Res
Objective—To determine whether plasma total CO2 concentrations would vary with the size of the evacuated tube used to collect blood samples.
Design—Randomized crossover study.
Animals—Convenience sample of 20 healthy adult horses.
Procedures—Jugular venous blood was collected from horses in random order into 8 types of evacuated tubes: 2-mL glass, 2- or 3-mL plastic or plastic plasma separator, 4- or 6-mL plastic, and 10-mL glass or plastic. Total CO2 concentrations in plasma were measured with a biochemistry analyzer. Data were analyzed via repeated-measures ANOVA and multivariate regression.
Results—The air volume-to-blood volume ratio was significantly higher and consequently, plasma total CO2 concentration was significantly lower when blood was collected into 2-mL glass tubes and 2- or 3-mL plastic tubes than when the other 5 types of evacuated tubes were used. Concentrations in the other tube types were statistically equivalent. A linear relationship was detected between total CO2 concentration and air volume–to–blood volume ratio.
Conclusions and Clinical Relevance—Blood samples should be collected into evacuated tubes with a small air volume–to–blood volume ratio whenever an accurate estimate of plasma total CO2 concentration is required.