A pulmonary alveolus, also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where pulmonary gas exchange takes place. Oxygen is exchanged for carbon dioxide at the blood–air barrier between the alveolar air and the pulmonary capillary. Alveoli make up the functional tissue of the mammalian lungs known as the lung parenchyma, which takes up 90 percent of the total lung volume.
Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered mental status due to ischemia in the brain.
Shortness of breath (SOB), also medically known as dyspnea or dyspnoea, is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity", and recommends evaluating dyspnea by assessing the intensity of its distinct sensations, the degree of distress and discomfort involved, and its burden or impact on the patient's activities of daily living. Distinct sensations include effort/work to breathe, chest tightness or pain, and "air hunger". The tripod position is often assumed to be a sign.
Crackles are the clicking, rattling, or crackling noises that may be made by one or both lungs of a human with a respiratory disease during inhalation, and occasionally during exhalation. They are usually heard only with a stethoscope. Pulmonary crackles are abnormal breath sounds that were formerly referred to as rales.
Skatole or 3-methylindole is an organic compound belonging to the indole family. It occurs naturally in the feces of mammals and birds and is the primary contributor to fecal odor. In low concentrations, it has a flowery smell and is found in several flowers and essential oils, including those of orange blossoms, jasmine, and Ziziphus mauritiana. It has also been identified in certain cannabis varieties.
There are different systems of feeding cattle in animal husbandry. For pastured animals, grass is usually the forage that composes the majority of their diet. In turn, this grass-fed approach is known for producing meat with distinct flavor profiles. Cattle reared in feedlots are fed hay supplemented with grain, soy and other ingredients to increase the energy density of the feed. The debate is whether cattle should be raised on fodder primarily composed of grass or a concentrate. The issue is complicated by the political interests and confusion between labels such as "free range", "organic", or "natural". Cattle raised on a primarily foraged diet are termed grass-fed or pasture-raised; for example meat or milk may be called grass-fed beef or pasture-raised dairy. The term "pasture-raised" can lead to confusion with the term "free range", which does not describe exactly what the animals eat.
Interstitial lung disease (ILD), or diffuse parenchymal lung disease (DPLD), is a group of respiratory diseases affecting the interstitium and space around the alveoli of the lungs. It concerns alveolar epithelium, pulmonary capillary endothelium, basement membrane, and perivascular and perilymphatic tissues. It may occur when an injury to the lungs triggers an abnormal healing response. Ordinarily, the body generates just the right amount of tissue to repair damage, but in interstitial lung disease, the repair process is disrupted, and the tissue around the air sacs (alveoli) becomes scarred and thickened. This makes it more difficult for oxygen to pass into the bloodstream. The disease presents itself with the following symptoms: shortness of breath, nonproductive coughing, fatigue, and weight loss, which tend to develop slowly, over several months. The average rate of survival for someone with this disease is between three and five years. The term ILD is used to distinguish these diseases from obstructive airways diseases.
Pneumonitis describes general inflammation of lung tissue. Possible causative agents include radiation therapy of the chest, exposure to medications used during chemo-therapy, the inhalation of debris, aspiration, herbicides or fluorocarbons and some systemic diseases. If unresolved, continued inflammation can result in irreparable damage such as pulmonary fibrosis.
Acute interstitial pneumonitis is a rare, severe lung disease that usually affects otherwise healthy individuals. There is no known cause or cure.
Alveolar lung diseases, are a group of diseases that mainly affect the alveoli of the lungs.
Idiopathic pulmonary fibrosis (IPF), or (formerly) fibrosing alveolitis, is a rare, progressive illness of the respiratory system, characterized by the thickening and stiffening of lung tissue, associated with the formation of scar tissue. It is a type of chronic scarring lung disease characterized by a progressive and irreversible decline in lung function. The tissue in the lungs becomes thick and stiff, which affects the tissue that surrounds the air sacs in the lungs. Symptoms typically include gradual onset of shortness of breath and a dry cough. Other changes may include feeling tired, and abnormally large and dome shaped finger and toenails. Complications may include pulmonary hypertension, heart failure, pneumonia or pulmonary embolism.
Usual interstitial pneumonia (UIP) is a form of lung disease characterized by progressive scarring of both lungs. The scarring (fibrosis) involves the pulmonary interstitium. UIP is thus classified as a form of interstitial lung disease.
Diffuse alveolar damage (DAD) is a histologic term used to describe specific changes that occur to the structure of the lungs during injury or disease. Most often DAD is described in association with the early stages of acute respiratory distress syndrome (ARDS). It is important to note that DAD can be seen in situations other than ARDS (such as acute interstitial pneumonia) and that ARDS can occur without DAD.
Pneumonia can be classified in several ways, most commonly by where it was acquired, but may also by the area of lung affected or by the causative organism. There is also a combined clinical classification, which combines factors such as age, risk factors for certain microorganisms, the presence of underlying lung disease or systemic disease and whether the person has recently been hospitalized.
Bovine coronavirus is a coronavirus which is a member of the species Betacoronavirus 1. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the N-acetyl-9-O-acetylneuraminic acid recepter. Infection causes calf enteritis and contributes to the enzootic pneumonia complex in calves. It can also cause winter dysentery in adult cattle. It can infect both domestic and wild ruminants and has a worldwide distribution. Transmission is horizontal, via oro-fecal or respiratory routes. Like other coronaviruses from genus Betacoronavirus, subgenus Embecovirus, it has a surface protein called hemagglutinin esterase (HE) in addition to the four structural proteins shared by all coronaviruses.
Ground-glass opacity (GGO) is a finding seen on chest x-ray (radiograph) or computed tomography (CT) imaging of the lungs. It is typically defined as an area of hazy opacification (x-ray) or increased attenuation (CT) due to air displacement by fluid, airway collapse, fibrosis, or a neoplastic process. When a substance other than air fills an area of the lung it increases that area's density. On both x-ray and CT, this appears more grey or hazy as opposed to the normally dark-appearing lungs. Although it can sometimes be seen in normal lungs, common pathologic causes include infections, interstitial lung disease, and pulmonary edema.
Bovine respiratory disease (BRD) is the most common and costly disease affecting beef cattle in the world. It is a complex, bacterial or viral infection that causes pneumonia in calves which can be fatal. The infection is usually a sum of three codependent factors: stress, an underlying viral infection, and a new bacterial infection. The diagnosis of the disease is complex since there are multiple possible causes.
Mycoplasma bovis is one of 126 species of genus Mycoplasma. It is the smallest living cell and anaerobic organism in nature. It does not contain any cell wall and is therefore resistant to penicillin and other beta lactam antibiotics.
Indoleacetate decarboxylase (IAD) is a glycyl radical enzyme that catalyses the decarboxylation of indoleacetate to form skatole, which is a malodorous organic compound that gives animal faeces their characteristic smell. This decarboxylation is the last step of the tryptophan fermentation in some types of anaerobic bacteria.
