Topics of Discussion

Environmental Management of IAD

IAD is an inflammatory condition of the airways that is triggered by exposure to a high level of particulates in the air, such as dust, mold, pollen and spores. Studies have shown that feeding – especially hay and pelleted feed – is the most important contributor to inhaled dust. Other important sources are cleaning stalls and sweeping the aisles. Exposure can be reduced by Continue reading

Topics of Discussion

What is Inflammatory Airway Disease [IAD]?

IAD is a disease of the airways which disturbs normal lung function (most often causing exercise intolerance) in addition to acting as a source of irritation (causing cough). Clinical signs are associated with swelling or obstruction and thus narrowing of the lower airways, which prevents air from reaching the maximum number of air sacs (alveoli) for gas exchange. In horses suffering from IAD, the airways are narrower because of inflammatory secretions, excessive mucus and fibrous tissue. In order to overcome the resulting increase in airway resistance, the horse has to work harder to achieve each breath and ultimately becomes exercise intolerant.

Horses with IAD most commonly present with a Continue reading

Clinicians and Staff

This Month’s Guest Editors

Dr. Melissa Mazan

Melissa Mazan, DVM, DACVIM

Dr. Melissa Mazan

Dr. Melissa Mazan, DVM, Diplomate ACVIM, is an Associate Professor and Director of the Equine Sports Medicine program at the Cummings School of Veterinary Medicine’s Hospital for Large Animals. Lung function, she notes, is essential to the success of equine athletes, and optimizing performance for competing horses is an important goal for hers. Dr. Mazan has extensive experience in the area of equine inflammatory airway disease, which affects as many as 80 percent of stabled horses and has provided pathways to better understanding similar human diseases, such as emphysema.

Dr. Daniela Bedenice
Dr. Daniela Bedenice

Daniela Bedenice, DVM, DACVIM, DACVECC

Dr. Bedenice, Dr. Med. Vet, Diplomate ACVIM, Diplomate ACVECC, joined the Tufts faculty following specialized training in large animal critical care and respiratory medicine. Dr. Bedenice became board certified in the specialty of large animal internal medicine in 2002, followed by large animal emergency and critical care in 2005. She works as an Assistant Professor in the Department of Clinical Sciences at Tufts, which combines teaching, research and a clinical referral service in the field of camelid and equine health care. Her special interests lie in comparative respiratory medicine, early disease identification and management, as well as newborn and adult intensive care. In collaboration with Drs. Hoffman and Mazan, Dr. Bedenice has been integrally involved in the characterization of lung disease, as well as development and validation of pulmonary function testing across species.

Dr. Andrew Hoffman
Dr. Andrew Hoffman

Andrew Hoffman, DVM, DVSc, DACVIM

An expert in equine lung function, Dr. Andrew Hoffman, DVM, DVSc, Diplomate ACVIM, is a Professor, researcher, and clinician at the Cummings School of Veterinary Medicine’s Hospital for Large Animals. Dr. Hoffman has spearheaded the development of non-invasive lung function testing of animals at the Cummings School, including Continue reading

Innovation

Techniques of non-invasive Lung Function Testing

In the clinical setting, three main non-invasive methods are currently used at Tufts to  test lung function in awake large animals: Forced Oscillation Techniques (FOT), plethysmography and measurement of functional residual capacity (FRC), which is an estimate of lung elasticity.

Forced oscillation techniques (FOT) are non-invasive tests to measure the resistance of the breathing system and thus evaluate airway narrowing. Different frequencies (1-7 Hz) of small air-pulses are directed into the patient’s airways via a face mask, while a computer captures changes in pressure and flow of these waves during spontaneous breathing. This calculates respiratory system resistance (Rrs).

FOT Lung Function Testing

A horse with airway inflammation undergoing FOT lung function testing at Tufts' Hospital for Large Animals.

A high Rrs often indicates airway narrowing due to thickening of bronchial walls and / or mucous accumulation in the lower lung. In horses with lower airway inflammation (e.g. IAD), we commonly observe a frequency dependence of resistance. This means that higher values for resistance are recorded at the lower oscillatory frequencies (1-2 Hz), a finding that is indicative of bronchoconstriction. Higher oscillation frequencies (> 2 Hz) provide information concerning central airway resistance. Baseline respiratory resistance measurements using Forced Oscillation Techniques can also be combined with bronchoprovocation tests to determine airway hyperreactivity or “twitchiness.” Continue reading

Innovation

Why is Lung Function Testing useful?

Over the past decade, pulmonary lung function testing (PFT) has gained increasing importance in veterinary patients, due to its ability both  to characterize and quantify the patient’s lung dysfunction using non-invasive techniques. This is particularly important during the early diagnosis of respiratory disease and the evaluation of treatment responses. The Cummings School of Veterinary Medicine has pioneered the development of non-invasive lung function testing in animals, including horses, dogs, llamas and alpacas.

Our Lung Function Laboratory, under the leadership of Dr. Andrew Hoffman and operation by Drs. Melissa Mazan and Daniela Bedenice, is a nationally recognized Continue reading

Clinical Case Review

Windy’s Cough: Causes and Characteristics

For the past 4 years, Windy, a 12-year old Hanoverian mare, has had a mild cough whenever her barn was closed up against the cold in the winter. Last year, the cough did not go away – and even seemed to be worse during the hot, humid weather in the late spring and summer. The cough was now interfering with the horse’s work as a third-level dressage horse. Windy’s veterinarian had recommended treatment with dexamethasone, a corticosteroid. The medication seemed to help, but the cough came back as soon as the treatment was discontinued.

Windy came to the Hospital for Large Animals at Tufts University’s Cummings School of Veterinary Medicine for a more in-depth evaluation. On physical examination, Windy’s breathing rate was slightly higher than usual (about 20 breaths per minute). There was also a small trickle of white discharge from both nostrils. When we listened to the air moving through her trachea, or windpipe, we could hear a rattling noise–which suggested the presence of mucus in her airways.

We examined Windy further at the Tufts Lung Function Laboratory, the only one of its kind in the Northeast. Here, we were able to test the ability of Windy’s lungs to move air effectively through her airways (see lung function testing, in our “Innovation” section), and found that her baseline resistance was only slightly elevated, an indicator of mild airway narrowing. This was good news, as it suggested a lower level of lung dysfunction. To determine if Windy’s lungs were “twitchy,” or more responsive to stimuli as often seen in horses with inflammatory airway disease, we performed a histamine bronchoprovocation test. These results showed that Windy narrowed her airways when exposed to very low levels of histamine, a substance that may be released in the horse’s lung when it is irritated by a dusty environment or cold temperatures.

Cytology of a bronchoalveolar lavage

This image shows the cytology of a bronchoalveolar lavage (BAL or lung wash) from a horse with inflammatory airway disease (IAD). This horse has many mast cells, as well as neutrophils and particulates from exposure to barn dust.

To further characterize the degree and type of inflammation in Windy’s airways, we performed a bronchoalveolar lavage, or BAL, using a thin, 2.3-meter videoscope. After examining the larger airways, we infused sterile saline into the lower lung and quickly suctioned it back. This gave us a sample of the abnormal inflammatory cells and mucus that were causing Windy’s cough. Microscopic examination of the lung secretions showed a large amount of mucus and inflammatory cells, called neutrophils. Windy also had an elevated number of mast cells, another type of inflammatory cell that contributes to airway reactivity, or twitchiness (see image).

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