The annual incidence of ARDS is 13–23 people per 100,000 in the general population. Its incidence in the mechanically ventilated population in intensive care units is much higher. According to Brun-Buisson "et al" (2004), there is a prevalence of acute lung injury (ALI) of 16.1% percent in ventilated patients admitted for more than 4 hours.

Worldwide, severe sepsis is the most common trigger causing ARDS. Other triggers include mechanical ventilation, sepsis, pneumonia, Gilchrist's disease, drowning, circulatory shock, aspiration, traumaespecially pulmonary contusionmajor surgery, massive blood transfusions, smoke inhalation, drug reaction or overdose, fat emboli and reperfusion pulmonary edema after lung transplantation or pulmonary embolectomy. Pneumonia and sepsis are the most common triggers, and pneumonia is present in up to 60% of patients and may be either causes or complications of ARDS. Alcohol excess appears to increase the risk of ARDS. Diabetes was originally thought to decrease the risk of ARDS, but this has shown to be due to an increase in the risk of pulmonary edema. Elevated abdominal pressure of any cause is also probably a risk factor for the development of ARDS, particularly during mechanical ventilation.

The death rate varies from 25–40% in centers using up-to-date ventilatory strategies and up to 58% in all centers.

Normal surgical masks and N95 masks appear equivalent with respect to preventing respiratory infections.

The lower respiratory tract consists of the trachea (wind pipe), bronchial tubes, the bronchioles, and the lungs.

Lower respiratory tract infections are generally more serious than upper respiratory infections. LRIs are the leading cause of death among all infectious diseases. The two most common LRIs are bronchitis and pneumonia. Influenza affects both the upper and lower respiratory tracts, but more dangerous strains such as the highly pernicious H5N1 tend to bind to receptors deep in the lungs.

Since ARDS is an extremely serious condition which requires invasive forms of therapy it is not without risk. Complications to be considered include the following:

- Pulmonary: barotrauma (volutrauma), pulmonary embolism (PE), pulmonary fibrosis, ventilator-associated pneumonia (VAP)

- Gastrointestinal: bleeding (ulcer), dysmotility, pneumoperitoneum, bacterial translocation

- Cardiac: abnormal heart rhythms, myocardial dysfunction

- Kidney: acute kidney failure, positive fluid balance

- Mechanical: vascular injury, pneumothorax (by placing pulmonary artery catheter), tracheal injury/stenosis (result of intubation and/or irritation by endotracheal tube

- Nutritional: malnutrition (catabolic state), electrolyte deficiency.

To help the bronchial tree heal faster and not make bronchitis worse, smokers should quit smoking completely.

Rhinorrhea can also occur when individuals with allergies to certain substances, such as pollen, dust, latex, soy, shellfish, or animal dander, are exposed to these allergens. In people with sensitized immune systems, the inhalation of one of these substances triggers the production of the antibody immunoglobulin E (IgE), which binds to mast cells and basophils. IgE bound to mast cells are stimulated by pollen and dust, causing the release of inflammatory mediators such as histamine. In turn, this causes, among other things, inflammation and swelling of the tissue of the nasal cavities as well as increased mucus production. Particulate matter in polluted air and chemicals such as chlorine and detergents, which can normally be tolerated, can make the condition considerably worse.

Rhinorrhea can be a symptom of other diseases, such as the common cold or influenza. During these infections, the nasal mucous membranes produce excess mucus, filling the nasal cavities. This is to prevent infection from spreading to the lungs and respiratory tract, where it could cause far worse damage. It has also been suggested that rhinorrhea is a result of viral evolution, and may be a response that is not useful to the host, but which has evolved by the virus to maximise its own infectivity. Rhinorrhea caused by these infections usually occur on circadian rhythms. Over the course of a viral infection, sinusitis (the inflammation of the nasal tissue) may occur, causing the mucous membranes to release more mucus. Acute sinusitis consists of the nasal passages swelling during a viral infection. Chronic sinusitis occurs when one or more nasal polyps appear. This can be caused by a deviated septum as well as a viral infection.

Acute bronchitis is one of the most common diseases. About 5% of adults are affected and about 6% of children have at least one episode a year. It occurs more often in the winter.

In infants under one year of age, acute bronchitis was the most common reason for admission to the hospital after an emergency department visit in the US in 2011.

Prevention of occupational asthma can be accomplished through better education of workers, management, unions and medical professionals. This will enable them to identify the risk factors and put in place preventive measures, including respiratory protection and exposure limits.

Approximately 21% of the adults affected by asthma report an aggravation of their symptoms while at work and an improvement when away, which implies that they may be suffering from occupational asthma. In the United States, occupational asthma is the most common occupational lung disease. Today, asthma affects as much as 15% of the Canadian population, a statistic reflective of other developed countries, and has increased fourfold in the last 20 years. Various reasons can be identified for this increase, including increase environmental pollution, better diagnostic ability, and greater awareness.

Viruses are common causes of the common cold. Less often, bacteria may also cause pharyngitis. Both of these organisms enter the body via the nose or mouth as aerosolized particles when someone sneezes or coughs. Because many germs are contagious, one can even acquire them from touching utensils, toys, personal care products or door knobs. The most common viruses that causes throat irritation include the common cold virus, influenza, infectious mononucleosis, measles and croup. Most bacteria and viruses usually induce throat irritation during the winter or autumn.

When the environment is dry especially in winter, it can create a sensation of dryness and a scratchy feeling in the throat. This is most commonly observed in the morning. Other individuals who also develop throat irritation are those breathing through their mouth because of a congested nose.

Environmental pollution is also a common cause of throat irritation. In fact, indoor pollution because of tobacco smoke used to be a common cause of throat irritation. Other items known to induce throat irritation include alcohol, spicy or hot foods and smokeless tobacco.

Clinically, the most serious and immediate complication is acute respiratory distress syndrome (ARDS), which usually occurs within 24 h. Those with significant lower airway involvement may develop bacterial infection. Importantly, victims suffering body surface burn and smoke inhalation are the most susceptible. Thermal injury combined with inhalation injury compromises pulmonary function, producing microvascular hyperpermeability that leads to a significant increase in lung lymph flow and pulmonary edema. The terrorist attack on the World Trade Center on September 11, 2001 left many people with impaired lung function. A study of firefighters and EMS workers enrolled in the FDNY WTC Medical Monitoring and Treatment Program, whose lung function was tested prior to 9/11, documented a steep decline in lung function in the first year after 9/11. A new study that includes a thousand additional workers shows that the declines have persisted over time. Prior to 9/11, 3% of firefighters had below-normal lung function, one year after 9/11 nearly 19% did, and six years later it stabilized at 13%. Ten to 14 days after acute exposure to some agents (e.g. ammonia, nitrogen oxides, sulfur dioxide, mercury), some patients develop bronchiolitis obliterans progressing to ARDS. Bronchiolitis obliterans with organized pneumonia can ensue when granulation tissue accumulates in the terminal airways and alveolar ducts during the body's reparative process. A minority of these patients develop late pulmonary fibrosis. Also at enhanced risk are persons with co-morbidities. Several studies report that both aged persons and smokers are especially vulnerable to the adverse effects of inhalation injury.

Sulfur mustard was used as a chemical weapon in World War I and more recently in the Iran–Iraq War. Sulfur mustard is a vesicant alkylating agent with strong cytotoxic, mutagenic, and carcinogenic properties. After exposure, victims show skin irritations and blisters. This agent also causes respiratory tract lesions, bone marrow depression, and eye damage, the epithelial tissues of these organs being predominately affected. Inhalation of high doses of this gas causes lesions in the larynx, trachea, and large bronchi with inflammatory reactions and necrosis. The alkylating agent affects more the upper parts of the respiratory tract, and only intensely exposed victims showed signs like bronchiolitis obliterans in the distal part. Secondary effects of sulfur mustard exposure lead to chronic lung diseases such as chronic bronchitis.

Carbon monoxide (CO) is presumed to be a complication in smoke inhalation. The initial approach to presumed CO poisoning involves administering supplemental oxygen at a fraction of inspired oxygen (FiO2) of 100 percent and then the use of hyperbaric oxygen (HBO) therapy is evaluated by physicians.

There is currently a limited amount of information available on the incidence and prevalence of VCD, and the various rates reported in the literature are most likely an underestimate. Although VCD is thought to be rare overall, its prevalence among the population at large is not known.

However, numerous studies have been conducted on its incidence and prevalence among patients presenting with asthma and exertional dyspnea. A VCD incidence rate of 2% has been reported among patients whose primary complaint was either asthma or dyspnea; the same incidence rate has also been reported among patients with acute asthma exacerbation. Meanwhile, much higher VCD incidence rates have also been reported in asthmatic populations, ranging from 14% in children with refractory asthma to 40% in adults with the same complaint. It has also been reported that the VCD incidence rate is as high as 27% in non-asthmatic teenagers and young adults.

Data on the prevalence of VCD is also limited. An overall prevalence of 2.5% has been reported in patients presenting with asthma. Among adults with asthma considered "difficult to control", 10% were found to have VCD while 30% were found to have both VCD and asthma. Among children with severe asthma, a VCD prevalence rate of 14% has been reported. However, higher rates have also been reported; among one group of schoolchildren thought to suffer from exercise-induced asthma, it was found that 26.9% actually had VCD and not asthma. Among intercollegiate athletes with exercise-induced asthma, the VCD rate has been estimated at 3%.

In patients presenting with symptoms of dyspnea, prevalence rates ranging from 2.8% to 22% have been reported in various studies. It has been reported that two to three times more females than males suffer from VCD. VCD is especially common in females who suffer from psychological problems. There is an increased risk associated with being young and female. Among patients suffering from VCD, 71% are over the age of 18. In addition, 73% of those with VCD have a previous psychiatric diagnosis. VCD has also been reported in newborns with gastroesophageal reflux disorder (GERD).

Smoke inhalation is the primary cause of death for victims of indoor fires. The inhalation or exposure to hot gaseous products of combustion can cause serious respiratory complications.

Some 50–80% of fire deaths are the result of smoke inhalation injuries, including burns to the respiratory system. The hot smoke injures or kills by a combination of thermal damage, poisoning and pulmonary irritation and swelling, caused by carbon monoxide, cyanide and other combustion products.

One of the most common areas of the body associated with irritation is the vagina. Many women complain of an itch, dryness, or discharge in the perineum at some point in their lives. There are several causes of vaginal irritation including fungal vaginitis (like candida) or trichomoniasis. Often, herpes simplex infection of the mouth or genitalia can be recurrent and prove to be extremely irritating.

Sometimes, the irritation can be of the chronic type and it can be so intense that it also causes painful intercourse. Aside from infections, chronic irritation of the vagina may be related to the use of contraceptives and condoms made from latex. The majority of contraceptives are made of synthetic chemicals which can induce allergies, rash and itching. Sometimes the lubricant used for intercourse may cause irritation.

Another cause of irritation in women is post menopausal vaginitis. The decline in the female sex hormones leads to development of dryness and itching in the vagina. This is often accompanied by painful sexual intercourse. Cracks and tears often develop on outer aspects of the labia which becomes red from chronic scratching. Post menopausal vaginitis can be treated with short term use of vaginal estrogen pessary and use of a moisturizer.

Individuals who smoke or are exposed to smog or other airborne pollutants can develop a condition known as COPD. In this disorder, there is constant irritation of the breathing tubes (trachea) and the small airways. The constant irritation results in excess production of mucus which makes breathing difficult. Frequently, these individuals wake up in the morning with copious amounts of foul smelling mucus and a cough which lasts all day. Wheeze and heavy phlegm are common findings. COPD is a lifelong disorder and there is no cure. Eventually most people develop recurrent pneumonia, lack any type of endurance, and are unable to work productively. One of the ways to avoid chronic bronchitis is to stop or not smoke.

The following increase an individual's chances for acquiring VCD:

- Upper airway inflammation (allergic or non-allergic rhinitis, chronic sinusitis, recurrent upper respiratory infections)

- Gastroesophageal reflux disease

- Past traumatic event that involved breathing (e.g. near-drowning, suffocation)

- Severe emotional trauma or distress

- Female gender

- Playing a wind instrument

- Playing a competitive or elite sport

Laryngitis that continues for more than three weeks is considered chronic. If laryngeal symptoms last for more than three weeks, a referral should be made for further examination, including direct laryngoscopy. The prognosis for chronic laryngitis varies depending on the cause of the laryngitis.

Laryngitis is inflammation of the larynx (voice box). Symptoms often include a hoarse voice and may include fever, cough, pain in the front of the neck, and trouble swallowing. Typically, these last under two weeks.

Laryngitis is categorised as acute if it lasts less than three weeks and chronic if symptoms last more than three weeks. Acute cases usually occur as part of a viral upper respiratory tract infection. Other infections and trauma such as from coughing are other causes. Chronic cases may occur due to smoking, tuberculosis, allergies, acid reflux, rheumatoid arthritis, or sarcoidosis. The underlying mechanism involves irritation of the vocal cords.

Concerning signs that may require further investigation include stridor, history of radiation therapy to the neck, trouble swallowing, duration of more than three weeks, and a history of smoking. If concerning signs are present the vocal cords should be examined via laryngoscopy. Other conditions that can produce similar symptoms include epiglottitis, croup, breathing in a foreign body, and laryngeal cancer.

The acute form generally gets better on its own. Resting the voice and sufficient fluids may help. Antibiotics generally do not appear to be useful in the acute form. The acute form is common while the chronic form is not. The chronic form occurs most often in middle age and is more common in men than women.

Fungi are ubiquitous organisms that play a vital role in decomposing organic matter. Many species of fungi live on the human body and some will infect nails causing a condition called onychomycosis. There are oral and topical antifungal therapies for this condition, however, in some instances cutting, filing, or abrading the nail may be necessary to improve cure rates. Thickened nails caused by injury, infection, diabetes, psoriasis, or vascular disease may require the use of a mechanical therapy, which can expose the healthcare worker to microbial dust.

Exposure to nail dust was first discussed and described in the literature as an occupational hazard in the early 70’s. In 1975, two female chiropodists were diagnosed with allergic hypersensitivity to nail dust Since that time, there have been a number of occupational-related complaints pertaining to airborne nail dust exposure and efforts have been made to study the podiatric professionals to determine related symptoms. Biological dust from the hand and foot care procedures may deposit in the conjunctiva, nose, and throughout the respiratory tract. The local irritation of these areas can lead to conjunctivitis, itching, tearing, rhinitis, sneezing, asthmatic attacks, bronchitis, and coughing.

The literature suggests that nail dust can be a respiratory sensitizer, which is defined as a substance that when breathed in can trigger an irreversible allergic reaction in the respiratory system. Sensitization does not usually take place immediately, but rather after months or years of exposure to the agent. Once sensitized, even the smallest amount of the substance can trigger asthma, rhinitis, or conjunctivitis that may exhibit the following symptoms: coughing, wheezing, chest tightness, runny or stuffy nose, and watery or prickly eyes. Millar found that within the podiatry profession there is four times the national prevalence of asthma. Hypersensitivity reactions are the most probable disposition for healthcare workers inhaling nail dust, although more serious lung pathology can not be ruled out

It is widely known and accepted that fungi will induce asthma, but it is estimated that only 10% of the population has allergic antibodies to fungal antigens, and half of them, that is 5% of the population, would be asymptomatic, further complicating the link between the fungal dust and troubling symptoms. "Trichophyton rubrum" is the most common fungal cause of nail dystrophy. Studies conducted in England found that the prevalence of "trichophyton rubrum" antibodies in podiatrists ranged from 14%-31%. This is evidence that the podiatrist is heavily exposed to "trichophyton rubrum" as observed in increased precipitating antibodies compared to the general population. It has been suggested that absorption of "trichophyton" fungal antigens can give rise to immunoglobulin E (IgE) antibody production, sensitization of the airways, and symptomatic asthma and rhinitis.

Nail work requiring clipping and drilling is also a potential cause for ocular injury and infection to the podiatrists, podiatric staff, and patients that are exposed to nail fragments and high-speed drills used for grinding. Possible ocular hazards result from exposure to foreign bodies, allergens, bacteria, viruses, fungi and protozoa that can be introduced at the time of eye trauma, or enter as a consequence of damage to the ocular structures; permitting the entry of opportunistic infection. The high-speed rotation of podiatry drill burrs potentially expose the healthcare worker to aerosols containing bloodborne pathogens such as Hepatitis B, Hepatitis C, or HIV. Davies et al. surveyed podiatrists and found that 41% of them complained of eye problems, particularly soreness, burning, itching and excess lacrimation.

A 1990 case illustrates the potential for ocular trauma to the healthcare provider: A podiatrist suffered a lacerated cornea when hit by a metallic shard from the grinding bit or by a fragment from the patient’s toenail. The podiatrist reported fleeting periods of blurriness for several months following the incident. The healthcare worker’s exposure to foreign bodies is not well documented in the literature like they are with dental staff using similar equipment; however, many of these incidents are certain to go unreported. The healthcare provider’s risk of injury during nail care, however slight, warrants the use of simple and inexpensive preventative measures.

Healthcare providers may use podiatry drills on onychauxic (thickened) nails of patients to alleviate or eliminate pain, prevent or treat subungual ulcerations, allow better penetration of topical antifungal agents, or improve cosmesis, all in effort to improve the patient’s “quality of life.” In a study conducted by Miller, 65% of respondents reported routinely drilling thickened toenails. However, the improved effectiveness of antifungal drugs such as itraconazole and terbinafine reduces the need to drill these infected nails.

Podiatry drills have a mechanical rotating burr that can be set at a range of speeds usually up to 12,000 rpm and may or may not have an integrated local ventilation extraction system. Even with the most effective dust extractors, the electric nail debridement process is not totally risk free because the extractors range from 25% - 92% effective in reducing airborne particles. While the large particles settle out to the floor, varying amounts of smaller particles remain suspended and are inhaled by or adhere to the practitioner and clinical environment. The particle sizes range from 0.1 to 100 um and 86% of these particles are less than 5 um in diameter and therefore capable of entry into the alveoli.

A kitten that has difficulty in breathing is very likely also to suffer from colic (which can cause weight loss in the early development of a normal kitten), and a very small daily (or twice daily) dose of liquid paraffin (one or two drops placed on the tongue of the kitten, or 0.1 ml) should help to alleviate this problem. FCKS kittens who do not maintain weight are usually among the group which die, but many of them may simply be unable to feed properly due to colic, becoming increasingly weak and lethargic, and fading due to malnutrition as much as to the thoracic problems.

Colic has many causes, but in a kitten with respiratory difficulty it is possible that a malfunction during the breathing process leads the kitten to swallow air instead of taking it into its lungs. The GI tract fills with air while the lungs do not receive a proper air supply, preventing them from inflating fully. Pressure from the stomach exacerbates the condition. Treating for colic with liquid paraffin seems to shorten recovery time from 4–10 weeks to a matter of days.