Medicine Hack

Bilevel noninvasive ventilation provides: 1) IPAP - inspiratory positive airway pressure and 2) EPAP - expiratory PAP at two different levels. This is typically delivered with a tight fitting nasal or face mask which allows for the development of positive airway pressure. The noninvasive therapy should be initiated as early as possible in case of respiratory failure and is best used for short term. "Delta PAP" is the difference between IPAP and EPAP. It directly correlates with the tidal volume delivered. If the "delta PAP" is larger then the tidal volume will be larger and hence it will provide a better alveolar ventilation.  INITIAL SETTINGS  It is quite safe to start the following initial settings: 1) EPAP 3 to 5 cm H2O (2 - 4 mm Hg) – It can be increased to around 10 cm H2O if ever the oxygenation remains inadequate tidal volume. 2) IPAP 8 to 12 cm H2O (6 - 9 mm Hg) – This can be increased in increments of 2 cm H2O as tolerated by the patient, to a maxim

 PENETRATION  Penetration is one of the five technical factors that help you in determining whether a radiograph is technically adequate.  ADEQUATE PENETRATION  If a frontal chest radiograph is adequately penetrated, you should be able to see the thoracic spine through the heart shadow. In the radiograph above, we can see the thoracic spine through the heart shadow (solid white line).  UNDER PENETRATION  It means that the penetration is inadequate. The radiograph will appear as too white. We will not be able to see the thoracic spine through the heart. This can lead us into making interpretation errors. 1) The pulmonary markings may appear more prominent and these can be mistaken for being due to a congestive heart failure or pulmonary fibrosis. 2) The left lung base will appear opaque thus obscuring the left hemidiaphragm. This can mimic or hide a true disease in the left lower lung field e.g. left lower lobe pneumonia or left pleural effusion. To avoid these misin

COPD exacerbation: Definition: Exacerbation of COPD is defined as an acute episode, characterized by the worsening of the patient’s respiratory symptoms that is beyond normal daily variations and that will eventually lead to a change in his medications. Those having 2 or more exacerbations per year are known as “frequent exacerbators”. Precipitating factors: 1) Respiratory tract infections – viral or bacterial. Most common cause. There may be an increased bacterial burden in the lower airways or new strains of bacteria are acquired during an exacerbation. Commonly implicated viruses include rhinovirus, respiratory syncytial virus, coronavirus and influenza virus. 2) Air pollution. 3) Interruption of maintenance therapy. 4) Unknown causes – 30% cases. Diagnosis: Diagnosis should be made clinically whereby the patient complains of an acute aggravation of his symptoms out of proportion to his day to day variations.  Assessment: Medical history: 1) Se

Exacerbations of COPD are more commonly seen during the winter season (nearly 1.6 times more frequently). The main cause of these exacerbations is infection with the respiratory virus, rhinovirus. Frequent exacerbations have been shown to lead to a faster decline in the lung function, poorer quality of life and increased mortality. A recent study showed that COPD exacerbations in colder periods of the year take longer to recover from and are more likely to involve cough or coryzal symptoms. The exacerbations in the cold seasons also have a greater impact on daily activity, with patients spending more time indoors and being more likely to be hospitalized with respiratory viral infection.

Respiratory failure may be classified as hypercapnic or hypoxemic. Hypercapnic respiratory failure is defined as an arterial PCO2 (PaCO2 ) greater than 45mmHg. Hypoxemic respiratory failure is defined as an arterial PO2 (PaO2 ) less than 55 mmHg when the fraction of oxygen in inspired air (FiO2) is 0.60 or greater. In many cases, hypercapnic and hypoxemic respiratory failure coexist. Distinctions between acute and chronic respiratory failure are summarized in the table below. In general, acute hypercapnic respiratory failure is defined as a PaCO2 greater than 45 mmHg with accompanying acidemia (pH less than 7.30). The physiological effect of a sudden increase in PaCO2 depends on the prevailing level of serum bicarbonate anion. In patients with chronic hypercapnic respiratory failure e.g. COPD, a long-standing increase in PaCO2 results in renal compensation and an increased serum bicarbonate concentration. A superimposed acute increase in PaCO2 has a less dramatic effect th

History: The three most common symptoms in COPD are 1) cough, 2) sputum production and 3) exertional dyspnea. Many patients will have the above named symptoms for months or years. They will seek medical attention only when there will be an episode of acute exacerbation. However, a careful history usually reveals the presence of symptoms prior to the acute exacerbation. Exertional dyspnea is often described as 1) increased effort to breathe, 2) heaviness, 3) air hunger or 4) gasping. The dyspnea is more when the patient does activities involving significant arm work, particularly at or above shoulder level. Conversely, activities that allow the patient to brace the arms and use accessory muscles of respiration are better tolerated.e.g. pushing a shopping cart, walking on a treadmill or pushing a wheelchair. As COPD advances, the principal feature is worsening dyspnea on exertion with increasing intrusion on the ability to perform vocational or avocational activities. In

Barrel shaped chest is commonly encountered in the clinical setting. It is seen in emphysema, hence also called as emphysematous chest. The anteroposterior diameter is increased (normally transverse:AP diameter is 7:5). The subcostal angle is wide (usually it is acute at around 70 degrees). The angle of Louis is unduly prominent with the sternum more arched. The spine is concave forwards and the ribs are less oblique. The respiratory movements are diminished bilaterally, with the mediastinum remaining in the central position. On percussion, the lung is hyper-resonant. On auscultation, there is a diminished vesicular breathing with a prolonged expiration. Rhonchi may be present.

Above is a chest radiograph of a schizophrenic patient. He was delusional about being a doctor. He used to read a lot of medical books and mastered the art of taking blood pressure. During an episode of psychosis, he broke the blood pressure apparatus and injected the mercury into his vein. We can see in the X-ray that there is micro-embolism of the liquid mercury to the pulmonary arterioles, mostly to the dependent areas and the arrow indicates a small pool of the mercury in the right ventricle.

COPD is a preventable and treatable systemic disease state characterized by a progressive airflow limitation that is not fully reversible and associated with an abnormal inflammatory response of the lungs to noxious particles and gas. Note that the new definition according to GOLD/ATS and ERS does not talk anything about the disease being a mixture of chronic bronchitis and emphysema, though these conditions are very frequently encountered in COPD and also the fact of being 'not fully reversible' distinguishes this disease from the other chronic obstructive condition which is bronchial asthma.

In a classical lesion, dilated and destroyed respiratory bronchioles coalesce in series and in parallel to produce sharply demarcated emphysematous spaces. They are separated from the acinar periphery (the  lobular septa) by intact  alveolar ducts and sacs of normal size, as shown by the diagram below.  The lesions vary in quality and quantity even within the same lung. There is striking irregularity of involvement of lobules, and even within the same lobule. The lesions are usually more common and become more severe in the upper than in the lower zones of the lung. Most affected are the upper lobe, particularly the posterior and apical segments, and the superior segment of the lower lobe as depicted below.  This type of emphysema is commonly seen in chronic cigarette smokers. For classification of emphysema, follow this link:  Emphysema

The criteria for separating transudates from exudates were published in 1972 by Light and coworkers. They were based on the measurements of serum and pleural fluid protein and LDH.  The criteria are as follows: If at least one of the following 3 criteria is present, the fluid is virtually always an exudate and if none is present then the fluid is virtually always a transudate: 1)      Pleural fluid : Serum protein ratio > 0.5 2)      Pleural fluid LDH > 2/3 of the upper limit of the serum reference range 3)      Pleural fluid : Serum LDH ratio > 0.6 An exception to using Light’s criteria is in the setting of CHF treated with diuretics. Normally, in CHF, the effusions are due to an increased capillary hydrostatic pressure and are therefore transudates. But the use of diuretics has been shown to increase the pleural fluid protein and LDH concentrations. Thus we will have a false positive result making the fluid appear as an exudate. It is believed to be

It is at times difficult to interpret a PA chest X-ray as the amount of information present is huge. A systematic approach should always be done.  One should have the understanding of what is normal. This must include an evaluation of the  1) soft tissues,  2) bones and joints,  3) pleura, lungs, major airways and pulmonary vascularity,  4) mediastinum and its contents,  5) heart and its chambers, as well as  6) the areas seen below the diaphragm and above the thorax. The heart borders are explained in this post.  On the right side of the heart the following structures can be identified: 1) Az - Azygous vein 2) A - Ascending aorta 3) S - Superior vena cava 4) RA - Right atrium On the left side of the heart, we can identify the following: 1) SC - Subclavian artery 2) AA - Aortic arch 3) PA - Pulmonary artery 4) LB - Lower border of pulmonary artery 5) LA - Left atrial appendage 6) LV - Left ventricle The x-ray on the right side i.e. B shows the actual positio

As soon as a diagnosis of VTE / PE is strongly suspected, anticoagulant therapy should be started unless there are contraindications. Parenteral drugs like unfractionated heparin (standard heparin) and low molecular weight heparin (lovenox) are started and therapy shifted to a long term stable vitamin K antagonist like warfarin. Unfractionated heparin The anticoagulant action is by binding to and accelerating the activity of antithrombin III. This inactivates thrombin, factor IXa and Xa and thus prevents further clot formation. The classical regimen for the dosage is a loading dose of 5000 - 10000 units followed by a continuous infusion of 1000 - 1500 units/hour. Unfortunately we all do not have the same weight. So, a more appropriate dosage is a loading dose of 80 units/kg and a continuous infusion of 18 units/kg/hr. The aim is to achieve a target activated partial thromboplastin time (aPTT) aka partial thromboplastin time with kaolin (PTTK) of 2-3 times the normal laboratory val

The use of I.V morphine in dyspnea from pulmonary edema due to left ventricular failure produces remarkable relief. The proposed mechanisms include:  1) reduced anxiety ( decreased perception of shortness of breath ),  2) reduced cardiac preload ( reduced venous tone ) and  3) decreased cardiac afterload (decreased peripheral resistance ).  However frusemide remains the treatment of choice.  Side effect is respiratory depression at a higher dosage which occurs because of inhibition of the brainstem respiratory mechanism.

It is caused by an organism known as Bacillus anthracis. The latter is a gram positive, spore-forming rod that is found in soil. The spores can remain viable for years. Anthrax came to public notice in September 2001 when it was used as a bioweapon delivered through the U.S Postal System causing infection in 22 persons of whom 5 died. In the past i.e. during World War II , anthrax was studied mainly for its potential use as a biological weapon but following the Biological and Toxin Weapons Convention Treaty in 1972, such research was no longer allowed. Still, some nations and extremist groups do work on this agent secretly. There are 3 major clinical forms of anthrax: 11)       Gastrointestinal anthrax – from ingestion of contaminated meat 22)       Cutaneous   anthrax – from introduction of spores through opening in skin 33)       Inhalational anthrax- inhalation of spores that deposit in the alveolar spaces. The inhalational form is the one usually used for biot

1) There is usually a tingling sensation in the throat in hemoptysis while in hematemesis the patient will usually complain from nausea and upset stomach. 2) The blood is usually frothy and bright red in hemoptysis while it is dark red in hematemesis, non-frothy and food particles may also be present at the same time. 3) Blood in hematemesis will give an acidic pH when tested with litmus paper whereas that in hemoptysis will be neutral to alkaline. 4) Stools will be almost always positive for occult blood in hematemesis while it is usually negative in case of hemoptysis. But it can also be positive at times if the patient has swallowed his sputum. Last reviewed on: 1 September 2015

Bronchial asthma is considered to be well controlled if the patient experiences cough, shortness of breath and wheezing less than 3 times/week during the day, less than 3 times/month of night time awakenings and no asthma related interference with normal activity. Recently it has been found that only 1/3rd of asthma patients can be categorized as being into the well controlled group.

It is a new approach to the treatment of asthma. It  is a recombin ant humanized gamma immunoglobulin (IgG)1 monoclonal antibody  that is targeted against the portion of IgE that binds to its receptors (FC -R1 and FC -R2 receptors) on mast cells and other inflammatory cells. It inhibits the binding of IgE to mast cells but does not activate IgE already bound to these cells and thus does not provoke mast cell degranulation. It may also inhibit IgE synthesis by B lymphocytes.    In addition, omalizumab causes down-regulation of IgE receptors on mast cells and basophils. Administration of omalizumab to asthmatic individuals for 10 weeks lowers plasma IgE to undetectable levels and significantly reduces the magnitude of both the early and the late bronchospastic responses to antigen challenge.  Repeated administration lessens asthma severity and reduces the corticosteroid requirement in patients with moderate to severe disease, especially those with a clear environment

Emphysema is defined as an abnormal, permanent dilatation of the airways distal to the terminal bronchioles due to a destruction in the walls. There are 4 types of emphysema: 1) centriacinar/centrilobular - seen in cigarette smokers 2) panacinar/panlobular - seen in α 1 -antitrypsin deficiency 3) distal acinar 4) irregular. Pathogenesis: Protease- antiprotease imbalance theory as shown in the picture above. On examination: Patient will be dyspneic, hyperventilating and have a prolonged expiration. The chest will be barrel shaped.