Lower respiratory tract infection

Lower respiratory tract infection
Classification and external resources
Conducting passages.
ICD-10	J10-J22, J40-J47

The lower respiratory tract is the part of the respiratory tract below the vocal cords. While often used as a synonym for pneumonia, the rubric of lower respiratory tract infection can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, high fever, coughing and fatigue.
Lower respiratory tract infections place a considerable strain on the health budget and are generally more serious than upper respiratory infections. Since 1993 there has been a slight reduction in the total number of deaths from lower respiratory tract infection. However in 2002 they were still the leading cause of deaths among all infectious diseases, and they accounted for 3.9 million deaths worldwide and 6.9% of all deaths that year.^[1]
There are a number of acute and chronic infections that can affect the lower respiratory tract. The two most common infections are bronchitis and pneumonia.^[2] Influenza affects both the upper and lower respiratory tracts. Antibiotics are often thought to be the first line treatment in lower respiratory tract infections; however, these are not indicated in viral infections. It is important to use appropriate antibiotic selection based on the infecting organism and to ensure this therapy changes with the evolving nature of these infections and the emerging resistance to conventional therapies.^[3] H. influenzae and M. catarrhalis are of increasing importance in both community acquired pneumonia (CAP) and acute exacerbation of chronic bronchitis (AECB) while the importance of S. pneumoniae is declining. It has also become apparent the importance of atypical pathogens such as C. pneumoniae, M. pneumoniae and L. pneumophila, in CAP.^[3]

Contents 1 Classification 1.1 Bronchitis 1.2 Pneumonia 2 Treatment 2.1 Antibiotic Choice 2.2 Non-Pharmacological Treatments 2.3 Complementary Therapies 3 Epidemiology 4 Research

Classification

Bronchitis

Main article: Bronchitis

Bronchitis can be classified as either acute or chronic. Acute bronchitis can be defined as acute bacterial or viral infection of the larger airways in healthy patients with no history of recurrent disease.^[2] It affects over 40 adults per 1000 each year and consists of transient inflammation of the major bronchi and trachea.^[4] Most often it is caused by viral infection and hence antibiotic therapy is not indicated in immunocompetent individuals.^[5][6] There are no effective therapies for viral bronchitis.^[6][7] Treatment of acute bronchitis with antibiotics is common but controversial as their use has only moderate benefit weighted against potential side effects (nausea and vomiting), increased resistance, and cost of treatment in a self-limiting condition.^[4][8] Beta2 agonists are sometimes used to relieve the cough associated with acute bronchitis. In a recent systematic review it was found there was no evidence to support their use.^[6]
Acute Exacerbations of Chronic Bronchitis (AECB) are frequently due to non-infective causes along with viral ones. 50% of patients are colonised with Haemophilus influenzae, Streptococcus pneumoniae or Moraxella catarrhalis.^[2] Antibiotics have only been shown to be effective if all three of the following symptoms are present:- increased dyspnoea, increased sputum volume and purulence. In these cases 500 mg of Amoxycillin orally, every 8 hours for 5 days or 100 mg doxycycline orally for 5 days should be used.^[2]

Pneumonia

Main article: Pneumonia

Pneumonia occurs in a variety of situations and treatment must vary according to the situation.^[7] It is classified as either community or hospital acquired depending on where the patient contracted the infection. It is life-threatening in the elderly or those who are immunocompromised.^[9][10] The most common treatment is antibiotics and these vary in their adverse effects and their effectiveness.^[9] Pneumonia is also the leading cause of death in children less than five years of age.^[11] The most common cause of pneumonia is pneumococcal bacteria, Streptococcus pneumoniae accounts for 2/3 of bacteremic pneumonias.^[12] A dangerous type of lung infection with a mortality rate of around 25%.^[10] For optimal management of a pneumonia patient the following must be assessed;- pneumonia severity (including where to treat e.g. Home, hospital or intensive care), identification of causative organism, analgesia of chest pain, the need for supplemental oxygen, physiotherapy, Hydration, bronchodilators and possible complications of emphysema or lung abscess.^[13]
For community acquired respiratory infections the appropriate use of fluoroquinolones is a therapeutic option. These have been demonstrated to have targeted in vitro activity against both the typical and atypical pathogens of interest.^[14][15] The newer fluoroquinolones (e.g., moxifloxacin or gatifloxacin) have extended gram +ve activity and once daily dosing and hence are potential first line in the treatment of lower respiratory tract infections.^[3] However it is clinical response that is the best indicators of efficacy and moxifloxacin or gatifloxacin have been proven to be effective against community acquired respiratory tract infections clinically.^[16][17]

Treatment

Antibiotic Choice

With increased development of drug resistance, traditional empirical treatments are becoming less effective, hence it is important to base antibiotic choice on isolated bacteria and sensitivity tests. According to the Cochrane review of antibiotic use in CAP in adults, the current evidence from RCTs is insufficient in order to make evidenced based decisions on the antibiotic of choice. Further studies are required to make these decisions.^[9] For children they found amoxicillin or procaine penicillin to have greater effect than co-trimoxazole for the treatment of CAP. In hospital settings, penicillin and gentamicin was found to be more effective than chloramphenicol, with oral amoxicillin giving similar results to injectable penicillins.^[11] In another review of children with severe pneumonia, oral antibiotics were found to be as effective as injectable ones without the side effects of pain, risk of infection, or high cost.^[18] Also in a Cochrane review azithromycin has been shown to be no better than Amoxycillin or Amoxycillin with clavulanic acid in the treatment of lower respiratory infections.^[19] The AMH list Amoxycillin as first line of AECB and community acquired pneumonia where as IV azithromycin is first line if high risk of death. If severe hospital acquired pneumonia it recommends IV gentamicin and ticarcillin with clavulanic acid.^[20]

Non-Pharmacological Treatments

In 2003 a very high quality, published research was done about the risk of hospitalization due to respiratory illness and type of infant feeding in developed countries. It involved 3,201 breastfed babies and 1,324 non –breastfed babies. It showed an overall 72 % reduction in the risk of hospitalization in infants who exclusively breastfed for 4 or more months compared to those who were formula-fed. Therefore, exclusive breastfeeding for 4 or more months is associated with a reduction in the risk of hospitalization secondary to lower respiratory tract diseases.^[21]
The mainstay of non pharmacological treatment for many years has been rest and increased fluid intake. Although it is common for doctors and other health professionals to recommend extra fluid intake, a Cochrane systematic review could find no evidence for or against increased fluid intake. Although the idea of replacing fluids lost through fever and rapid breathing was sound, some observational studies reported harmful effects such as dilution of blood sodium concentration leading to headache, confusion or possibly seizures.^[22] Rest will allow the body to conserve energy to fight off the infection. Physiotherapy is indicated in some types of pneumonia and should be encouraged where appropriate.

Complementary Therapies

Chickweed taken orally has been used for many years to reduce fever and phlegm associated with bronchitis. It is believed to act as an expectorant and although the pharmacological actions of several constituents suggest it may be useful, controlled studies are not available to confirm its effectiveness.^[23]
A systematic review of Chinese herbs used in the treatment of acute bronchitis found that there was weak evidence for their use, but there were insufficient quality data to recommend them. The benefit found may be due to study design or publication bias. Hence they should be used carefully because their safety is largely unknown.^[24]
Thyme is approved by commission E in the treatment of bronchitis and there are encouraging data for its use in chronic bronchitis when used in combination with other herbs, however there is no stand-alone data.^[23]
The use of Vitamin C is commonly thought to act to prevent colds and other respiratory infections. However according to a recent Cochrane review the evidence is too weak to support its widespread use as a prophylactic in preventing pneumonia in the general population. It may be reasonable to use in high risk patients with low plasma levels of vitamin C due to its low cost and risk associated with is use.^[25] Vitamin C used as an orthomolecular antibiotic, is most effective when used in the same way; i.e., on timetable dosages.
Vitamin A has been successfully used to reduce the mortality and severity of respiratory infection with measles. However in a review of non-measles pneumonia it was not found to have any benefit or harmful effects.^[26]
Used by native healers for millennia, garlic contains allicin, a powerful anti-fungal and antibiotic compound. Native American tribes have used garlic to treat coughs and croup. British herbalists use garlic for hoarseness and coughs. Louis Pasteur studied garlic's antibacterial properties. During both World Wars, Allium sativum was used as an antiseptic.
For the treatment of pneumonia baical skullcap was shown to be as effective as piperacillin after one treatment. The piperacillin group resulted in 4 of 30 patients with fungal infections while there were none in the baical skullcap group.^[23]

Epidemiology

Disability-adjusted life year for lower respiratory infections per 100,000 inhabitants in 2002.^[27]

  no data

  less than 100

  100-700

  700-1400

  1400-2100

  2100-2800

  2800-3500

  3500-4200

  4200-4900

  4900-5600

  5600-6300

  6300-7000

  more than 7000

Research

It is likely that the future treatment of lower respiratory tract infections will consist of new antibiotics aimed at facing the problems associated with the constant emergence of antibiotic resistance. With resistance evolving so rapidly future treatments may include the use of vaccines to prevent these infections. Although a Cochrane systematic review of a polysaccharide pneumococcal vaccine didn’t reduce the pneumonia or their related deaths in adults, but was able to reduce incidence of more specific outcomes such as pneumococcal disease in the elderly.^[10] So it is hoped with further developments these will become more effective against pneumonia.
Vaccination of patients with AECB in the autumn months is thought to have a positive effect in reducing the severity and number of exacerbations over winter. The oral vaccine described in this review was able to decrease the carriage or non-typeable Haemophilus influenzae that is a common cause of exacerbations to chronic bronchitis.^[28] With good planning and further research these types of vaccines may reduce the burden associated with lower respiratory diseases.
There are few treatments available for viral forms of bronchitis and pneumonia. Respiratory syncytial virus (RSV), the main cause of these in children, could be potentially treated using a new monoclonal antibody (mAb) Motavizumab. In animal trials it reduced antibody titres 100 lower than the only drug currently available to treat the condition.^[29] This holds great promise for future treatments of LRTI.

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