Caisson Disease or Decompression Sickness

Caisson disease is also known as decompression sickness or diver's disease. When the body is subjected to high surrounding pressure (e.g. scuba diving), more than usual amount of Nitrogen gets dissolved in the blood. If the pressure is relieved suddenly, the dissolved Nitrogen can become gaseous quicker than the body can get rid of. These bubbles can lead to ischemia by blocking blood vessels. Clinical situations when such sudden depressurization can occur include scuba diving, caisson working, mining, flying in unpressurised aircraft, and extra-vehicular activity from spacecraft.

Depending upon the location of ischemia a variety of symptoms can results. Classically the symptoms are described as the bends, the chokes and the staggers!

The bends: refers to pain in the joints from ischemia of joint capsules
The chokes: refers to dyspnea
The staggers: refers to neurological symptoms.

Prevention:


-Divers should limit their ascent rate to about 10 metres per minute.
-Oxygen pre-breathing

Treatment:

-Administer 100% oxygen by face mask until re-compression with 100% oxygen until hyperbaric oxygen therapy is available.
-Treat dehydration

DLCO - Diffusion Capacity of Lungs for Carbon Monoxide

DLCO measures the ease with which Carbon Monoxide can diffuse across the alveolar lining. Normal would be 100 +/- 20. There are conditions in which it can increase as well as decrease as listed below.

Decreased DLCO:

With restrictive pattern on PFTs (poulmonary function tests) then diagnosis could be restrictive lung diseases such as fibrosis, pneumonitis, elveolitis, idiopathic pulmonary fibrosis, firbrosis secondary to bleomycin therapy.

With obstructive pattern on PFTs then diagnosis is usually emphysema.

If there is no PFTs and clinical scenarios are suggestive the following two could be possible:
1) Pulmonary embolism (long plane journey, after pregnancy, on oral contraceptives etc.)
2) Pulmonary hypertension (idiopathic, h/o heart disease etc.)

Increased DLCO:

With increased circulating lung blood volume e.g. exercise, heart failure

Asthma

Polycythemia

Normal DLCO 

Can be seen in extrinsic conditions affecting the ventilation for example scoliosis. PFTs will show restrictive pattern but DLCO will be normal.

Pneumonia - causes and organisms

1) Gram-Positive Bacteria

    -Streptococcus pneumoniae is the most common cause of pneumonia(20 - 60% of all community-acquired pneumonia-CAP in adults).
    -Staphylococcus aureus causes only about 2% of CAP but 10 - 15% of hospital-acquired pneumonias. It is the organism most often associated with viral influenza.
    -Streptococcus pyogenes or Group A streptococcus.

2) Gram-Negative Bacteria

    These cause infections in patients with chronic lung conditions like cystic fibrosis and chronic lung disease.

    -Haemophilus influenzae
    -Klebsiella pneumoniae may be responsible for pneumonia in alcoholics and other people who are physically debilitated.         

    -Pseudomonas aeruginosa is an important cause of nosocomial pneumonia. It is a common cause of pneumonia.
    -Moraxella catarrhalis, Neisseria meningitidis and E. Coli are other rare gram negative bacteria causing pneumonia.

3) Atypical Pneumonia

    -Mycoplasma pneumoniae is the most common atypical bug causing pneumonia. Mycoplasma is a tiny bacterium that lacks a cell wall. The pneumonia caused by it is commonly called "walking pneumonia."
    -Chlamydia pneumoniae disease is usually mild but can be severe in babies and elderly.
    -Legionella pneumophila causes Legionnaires' disease. It is contracted by breathing in drops of contaminated water (especially from air coolers and air conditioners). Outbreaks are often reported in hotels, cruise ships, and office buildings.
    -Workers exposed to pigeons, parrots, parakeets, and turkeys are at risk for psittacosis, a lung disease caused by the bacteria Chlamydia psittaci.

4) Viral Pneumonia

    -Influenza. Pneumonia is a major complication of the flu and can be very serious(usually staphylococcal)
    -Respiratory syncytial virus usually infects infants and causes bronchiolitis. It can also cause pneumonitis.
    -Parainfluenza virus, Adenoviruses, Herpes viruses, Avian influenza(Type A influenza subtype H5N1 in birds/Swine flu) are other relatively uncommon causes of pneumonia.

5) Anaerobic Bacteria

This usually results from aspiration. This may happen in children and adults with chronic neuromuscular disorders, after a head injury or general anesthesia, or under the effects of drugs or alcohol.

6) Opportunistic infections

    -Pneumocystis carinii, renamed Pneumocystis jiroveci in 2002, is a parasite. It was originally thought to be protozoa but is now classified as a fungus.
    -Mycobacterium tuberculosis, avium etc.
    -Cytomegalovirus

7) Chemical pneumonia:

    Exposure to chemicals can also cause inflammation and pneumonia.

Legionnaire’s Disease

Legionnaire’s Disease – caused by Legionella Pneumonia causes disease in smokers, with diarrhea, headache and confusion.

Clinical manifestations of Aspergillus infection of the lungs(Pulmonary aspergillosis)

There are four common manifestations of pulmonary aspergillosis namely - Allergic Broncho Pulmonary Aspergillosis (ABPA), Chronic Necrotizing Pulmonary Aspergillosis(CNPA), aspergilloma ('Fungal ball') and invasive aspergillosis.

 

1) ABPA - is almost exclusively seen in asthmatics or cystic fibrosis patients. It is basically an allergic reaction to aspergillus that is colonized in the airways. Patients have fever and respiratory symptoms (cough, hemoptysis, wheezing).

2) Aspergilloma -  is seen in immunocompromised patients. or in lungs with pre-existing cavities.  Aspergillomas are often silent or cause fever and respiratory symptoms similar to ABPA.

 

3) CNPA - Occurs in individuals with underlying disease, such as severe chronic obstructive pulmonary disease (COPD) and prolonged antibiotic therapy. They present with symptoms  such as fever, cough, night sweats, and weight loss.

 

4) Invasive aspergillosis - occurs in patients with immunosuppression or ANC (Absoulute neutorphil count) and in patients post transplantation. These patients are usually sick and need urgent parenteral treatment.