History

Fact Explanation
History of ischemic heart disease. Ischemic cardiomyopathy is a significantly impaired left ventricular function (left ventricular ejection fraction ≤35 to 40%) due to inadequate oxygen delivery to the myocardium due to coronary artery disease. Therefore patients with ischemic cardiomyopathy often have symptoms of angina or heart failure. [1],[2],[3],[4]
shortness of breath. Shortness of breath is a heart failure symptom. To maintain cardiac output left ventricular end diastolic pressure is raised. It is followed by in left atrial pressure rising and pulmonary venous pressure rising. It results in reduced pulmonary diffusion owing to interstitial edema, thus causing breathlessness. Dyspnea on exertion is caused by failure of the left ventricular output to rise during exercise with resultant increase in pulmonary venous pressure. [1],[2],[5],[6]
Orthopnea Orthopnea is the sensation of breathlessness in the recumbent position, relieved by sitting or standing. Orthopnea is caused by the pulmonary congestion which occurs during recumbency. In the horizontal position there is redistribution of blood volume from the lower extremities and splanchnic beds to the lungs. In normal individuals this has little effect, but in patients in whom the additional volume cannot be pumped out by the left ventricle, there is a significant reduction in vital capacity and pulmonary compliance with resultant dyspnea. Pulmonary congestion reduces when the patient is in erect position, it results in improvement in symptoms. [1],[2],[5]
Paroxysmal nocturnal dyspnea Paroxysmal nocturnal dyspnea is a sensation of breathlessness that awakens the patient, often after 1 or 2 hours of sleep, and is usually relieved in the upright position.Paroxysmal nocturnal dyspnea may be caused by mechanisms similar to those for orthopnea. The failing left ventricle is suddenly unable to match the output of a more normally functioning right ventricle; this results in pulmonary congestion. [1],[2] [5]
Chest pain Chest pain occurs behind the sternum or slightly to the left of it. The character of the pain may be tightening, squeezing, or crushing pain. The pain may radiate to the neck, jaw, back, shoulder, or arm. The pain may be associated with dizziness, feeling of indigestion, nausea, vomiting, and sweating. [1],[2],[3],[4]
Extreme fatigue Extreme fatigue is unexplained tiredness after activity. Reduced cardiac output on exercise leads to impaired skeletal muscle blood supply, thus causing fatigue. [1],[2],[3],[4]
Palpitations Palpitation is sensation of feeling the heartbeat. This is a symptom of heart failure. [5],[6]
Cough Cough occurs as a result of congestion caused by fluid in the lungs. The sputum i frothy and pink due to rupture of capillaries. [5],[6]
Headache and blurred vision Hypertension is a important risk factor of ischemic heart disease. Symptoms of severe hypertension such as headache and blurred vision, previous treatments, duration and response are important are important information to management decisions. [1],[2],[3],[4],[6]
Polyurea and Polydipsea, Diabetes is a important risk factor of ischemic heart disease. Symptoms such as polyuria, polydipsia, previous treatments, duration and response are important are important information to management decisions. [1],[2],[3],[4],[6]
Family history Family history of hypertension, diabetes mellitus, dyslipidemia, cardiovascular disease must assessed specifically. They are important in risk assessment. [1],[2],[3],[4]
Social history Occupation, habits like smoking, alcohol consumption, dietary habits, engaging aerobic exercise are important factors influencing management and outcome. [1],[2],[3],[4]
References
  1. MANTZIARI L, ZIAKAS A, VENTOULIS I, KAMPERIDIS V, LILIS L, KATSIKI N, KARAVASILIADOU S, KIRAKLIDIS K, PLIAKOS C, GEMITZIS K, KARVOUNIS H, STYLIADIS IH. Differences in Clinical Presentation and Findings between Idiopathic Dilated and Ischaemic Cardiomyopathy in an Unselected Population of Heart Failure Patients. Open Cardiovasc Med J [online] 2012:98-105 [viewed 07 July 2014] Available from: doi:10.2174/1874192401206010098
  2. KWON D. H., HACHAMOVITCH R., ADENIYI A., NUTTER B., POPOVIC Z. B., WILKOFF B. L., DESAI M. Y., FLAMM S. D., MARWICK T.. Myocardial scar burden predicts survival benefit with implantable cardioverter defibrillator implantation in patients with severe ischaemic cardiomyopathy: influence of gender. Heart [online] December, 100(3):206-213 [viewed 07 July 2014] Available from: doi:10.1136/heartjnl-2013-304261
  3. PROCLEMER A, LEWALTER T, BONGIORNI MG, SVENDSEN JH, PISON L, LUNDQVIST CB, SCIENTIFIC INITIATIVE COMMITTEE, EUROPEAN HEART RHYTHM ASSOCIATION. Screening and risk evaluation for sudden cardiac death in ischaemic and non-ischaemic cardiomyopathy: results of the European Heart Rhythm Association survey. Europace [online] 2013 Jul, 15(7):1059-62 [viewed 07 July 2014] Available from: doi:10.1093/europace/eut187
  4. LANZA GA, CREA F. Primary coronary microvascular dysfunction: clinical presentation, pathophysiology, and management. Circulation [online] 2010 Jun 1, 121(21):2317-25 [viewed 07 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.109.900191
  5. MUKERJI V, WALKER HK, HALL WD, HURST JW. Dyspnea, Orthopnea, and Paroxysmal Nocturnal Dyspnea [online] 1990 [viewed 08 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/21250057
  6. ROBERTS AW, CLARK AL, WITTE KK. Review article: Left ventricular dysfunction and heart failure in metabolic syndrome and diabetes without overt coronary artery disease--do we need to screen our patients? Diab Vasc Dis Res [online] 2009 Jul, 6(3):153-63 [viewed 09 July 2014] Available from: doi:10.1177/1479164109338774

Examination

Fact Explanation
Edema Bilateral pitting ankle, sacral, abdominal wall and genital edema can be elicited. As a result of the left ventricular failure pulmonary edema occurs. Pulmonary edema causes pulmonary arterial hypertension, right ventricular hypertrophy with dilatation and right ventricular failure. Right ventricular failure causes systemic venous congestion and edema. [1],[2],[3],[4]
Cyanosis Reduced pulmonary diffusion due to interstitial edema causes deoxyhemoglobin concentration >5.0 g/dL. It results in bluish discoloration of the skin or mucous membranes. [1],[2],[3],[4]
Elevated Jugular Venous Pressure (JVP) As a result of the left ventricular failure pulmonary edema occurs. Pulmonary edema causes pulmonary arterial hypertension, right ventricular hypertrophy with dilatation and right ventricular failure. Right ventricular failure causes systemic venous congestion and elevated pressure in the neck veins. [1],[2],[3],[4]
Tachycardia Heart rate is increased up to a limit to compensate the impaired left ventricular function. Therefore pulse may feel rapid. [1],[2],[3],[4]
Displaced apex Due to impaired left ventricular function left ventricular hypertrophy and left ventricle dilatation occurs. It results cardiomegaly and displaced apex.
Gallop rhythm Left ventricular failure cause 3rd and 4th heart sounds. When 3rd and 4th heart sounds heard with tachycardia it is called as "gallop rhythm". [1],[2],[3],[4]
Bilateral crepitations. Bilateral fine end inspiratory crepitations will be heard during respiratory system examination. [1],[2],[3],[4]
Hepatomegaly As a result of the left ventricular failure pulmonary edema occurs. Pulmonary edema causes pulmonary arterial hypertension, right ventricular hypertrophy with dilatation and right ventricular failure. Right ventricular failure causes systemic venous congestion and enlarged liver. Liver is usually tender due to the stretching of the capsule. [1],[2],[3],[4]
References
  1. MANTZIARI L, ZIAKAS A, VENTOULIS I, KAMPERIDIS V, LILIS L, KATSIKI N, KARAVASILIADOU S, KIRAKLIDIS K, PLIAKOS C, GEMITZIS K, KARVOUNIS H, STYLIADIS IH. Differences in Clinical Presentation and Findings between Idiopathic Dilated and Ischaemic Cardiomyopathy in an Unselected Population of Heart Failure Patients. Open Cardiovasc Med J [online] 2012:98-105 [viewed 07 July 2014] Available from: doi:10.2174/1874192401206010098
  2. ASHLEY, E.A. and NIEBAUER, J. Cardiology Explained. London: Remedica; 2004. Chapter 7, Heart failure. [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/books/NBK2218/
  3. KWON D. H., HACHAMOVITCH R., ADENIYI A., NUTTER B., POPOVIC Z. B., WILKOFF B. L., DESAI M. Y., FLAMM S. D., MARWICK T.. Myocardial scar burden predicts survival benefit with implantable cardioverter defibrillator implantation in patients with severe ischaemic cardiomyopathy: influence of gender. Heart [online] December, 100(3):206-213 [viewed 07 July 2014] Available from: doi:10.1136/heartjnl-2013-304261
  4. PROCLEMER A, LEWALTER T, BONGIORNI MG, SVENDSEN JH, PISON L, LUNDQVIST CB, SCIENTIFIC INITIATIVE COMMITTEE, EUROPEAN HEART RHYTHM ASSOCIATION. Screening and risk evaluation for sudden cardiac death in ischaemic and non-ischaemic cardiomyopathy: results of the European Heart Rhythm Association survey. Europace [online] 2013 Jul, 15(7):1059-62 [viewed 07 July 2014] Available from: doi:10.1093/europace/eut187

Differential Diagnoses

Fact Explanation
Dilated cardiomyopathy More than half of the cases of dilated cardiomyopathy, the etiology is unknown. As many as one-third of the people who have dilated cardiomyopathy inherit it from their parent. [1],[2],[3]
Hypertrophic cardiomyopathy Most cases of hypertrophic cardiomyopathy are inherited. It also can develop over time because of high blood pressure or aging. Sometimes, other diseases, such as diabetes or thyroid disease, can cause hypertrophic cardiomyopathy. Sometimes the etiology of hypertrophic cardiomyopathy is unknown. [1],[2],[3]
Restrictive cardiomyopathy Certain diseases and conditions can cause restrictive cardiomyopathy. Some examples are hemochromatosis, sarcoidosis, amyloidosis and connective tissue disorders. [1],[2],[3]
Arrhythmogenic Right Ventricular Dysplasia It is thought that arrhythmogenic right ventricular dysplasia is an inherited disease. [1],[2],[3]
Non cardiac pulmonary edema Examples for noncardiac pulmonary edema are Adult respiratory distress syndrome (ARDS), Renal failure and fluid overload. [4],[5]
Bronchial asthma Bronchial asthma or Chronic obstructive pulmonary disease (COPD) exacerbation can presents with breathlessness, tachypnea and tachycrdia. [4],[5]
Broncho pneumonia Usually presents with breathlessness, tachypnea, tachycardia and fever. Patients are usually very ill. [4],[5]
Nephrotic syndrome Usually presents with frothy urine, facial puffiness, ankle and sacral edema. Urine ward test helps to identify protein urea. [4],[5]
Chronic renal failure Usually presents with pallor, half moon nails, uremic breath and ankle edema. [4],[5]
Chronic liver disease Usually presents with jaundice, ankle edema, ascites and features of hepatic encephalopathy. [4],[5]
References
  1. MANTZIARI L, ZIAKAS A, VENTOULIS I, KAMPERIDIS V, LILIS L, KATSIKI N, KARAVASILIADOU S, KIRAKLIDIS K, PLIAKOS C, GEMITZIS K, KARVOUNIS H, STYLIADIS IH. Differences in Clinical Presentation and Findings between Idiopathic Dilated and Ischaemic Cardiomyopathy in an Unselected Population of Heart Failure Patients. Open Cardiovasc Med J [online] 2012:98-105 [viewed 07 July 2014] Available from: doi:10.2174/1874192401206010098
  2. WU J. Congestive Cardiac Failure: Pathophysiology and Treatment Yale J Biol Med [online] 1994, 67(1-2):49-50 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2590803
  3. PROCLEMER A, LEWALTER T, BONGIORNI MG, SVENDSEN JH, PISON L, LUNDQVIST CB, SCIENTIFIC INITIATIVE COMMITTEE, EUROPEAN HEART RHYTHM ASSOCIATION. Screening and risk evaluation for sudden cardiac death in ischaemic and non-ischaemic cardiomyopathy: results of the European Heart Rhythm Association survey. Europace [online] 2013 Jul, 15(7):1059-62 [viewed 07 July 2014] Available from: doi:10.1093/europace/eut187
  4. ASHLEY, E.A. and NIEBAUER, J. Cardiology Explained. London: Remedica; 2004. Chapter 7, Heart failure. [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/books/NBK2218/
  5. FIGUEROA MS, PETERS JI. Congestive heart failure: Diagnosis, pathophysiology, therapy, and implications for respiratory care. Respir Care [online] 2006 Apr, 51(4):403-12 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16563194

Investigations - for Diagnosis

Fact Explanation
Electrocardiogram (ECG) ECG is performed to identify features of hypertension such as axis deviation, ischemic changes such as Q waves, deep T waves, arrhythmia and left ventricular hypertrophy . [1],[2]
Echocardiogram To get the echo evidence of ischemic cardiomyopathy such as regional wall motion abnormalities, cardiac chamber dimension, systolic and diastolic function, ejection fraction etc. [2],[3]
Chest X-ray Chest X-ray demonstrates genaralized cardiac enlargement. cardiothoracic ratio >50%, prominent upper lobe veins, interstitial edema, alveolar shadowing, kerly B lines and bat wing appearance are the important changes of heart failure. [2],[4]
Treadmill test The ECG is performed whilst the patient walks on a motorized treadmill. The test based upon the principle that exercise increases the myocardial demand on coronary blood supply, which may be inadequate during exercise, and at peak stress can result relative myocardial ischemia. Myocardial ischemia provoked by exertion results in ST segment depression in leads facing the affected segments. The form of ischemic segment depression provoked by ischemia is characteristic. It is either planer or shows down sloping depression. [1],[2]
Coronary angiography This is done to identify narrowing of the arteries. It can differentiate ischemic cardiomyopathy from congestive cardiomyopathy.[1],[2]
Blood urea This is important to identify renal failure. If blood urea is elevated specific tests such as creatinine clearance must be performed.[2],[4]
Serum creatinine This is important to identify renal failure. If serum creatinine is elevated specific tests such as creatinine clearance must be performed. [2],[4]
Serum electrolytes These patients are treated with diuretics. Therefore serum electolytes must be checked. [2],[4]
Urine full report To exclude nephrotic syndrome and chronic renal failure from differentials this is important. [2],[4]
Full blood count Anemia causes high output cardiac failure. Full blood count provides information on type and possible etiology of anemia. [2],[4]
Cardiac biochemical markers Cardiac biochemical markers (CK-MB, troponin) provides evidence of myocardial infarction. [1], [2]
Lipid profile Hyperlipidemia increases the risk of ischemic heart disease. [2],[4]
Cardiac MR May demonstrate etiologies of left ventricular dysfunction ( e.g. previous myocardial infarction) or demonstrate abnormal myocardial fibrosis. Cardiac MR is also useful for identifying myocardial thrombus. [1],[2]
Radionuclide studies Radionuclide studies are performed to assess heart’s pumping function. [1]
Myocardial biopsy Myocardial biopsy done to study a small tissue sample from heart muscle. This is not indicated outside specialist care. [1],[2]
References
  1. AGHASADEGHI K, ASLANI A. Differentiation of ischemic and dilated cardiomyopathy on electrocardiograms. Asian Cardiovasc Thorac Ann [online] 2008 Apr, 16(2):103-6 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18381865
  2. ASHLEY, E.A. and NIEBAUER, J. Cardiology Explained. London: Remedica; 2004. Chapter 7, Heart failure. [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/books/NBK2218/
  3. HAYLEY BD, BURWASH IG. Heart failure with normal left ventricular ejection fraction: role of echocardiography. Curr Opin Cardiol [online] 2012 Mar, 27(2):169-80 [viewed 09 July 2014] Available from: doi:10.1097/HCO.0b013e32834fe8df
  4. FIGUEROA MS, PETERS JI. Congestive heart failure: Diagnosis, pathophysiology, therapy, and implications for respiratory care. Respir Care [online] 2006 Apr, 51(4):403-12 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16563194

Investigations - Followup

Fact Explanation
ECG ECG must must performed periodically to identify features of hypertension such as axis deviation, ischemic changes such as Q waves, deep T waves, arrhythmia and left ventricular hypertrophy. [1]
Echocardiogram This is performed periodically to monitor cardiac function of ischemic cardiomyopathy such as regional wall motion abnormalities, cardiac chamber dimension, systolic and diastolic function, ejection fraction etc. [2]
References
  1. AGHASADEGHI K, ASLANI A. Differentiation of ischemic and dilated cardiomyopathy on electrocardiograms. Asian Cardiovasc Thorac Ann [online] 2008 Apr, 16(2):103-6 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18381865
  2. HAYLEY BD, BURWASH IG. Heart failure with normal left ventricular ejection fraction: role of echocardiography. Curr Opin Cardiol [online] 2012 Mar, 27(2):169-80 [viewed 09 July 2014] Available from: doi:10.1097/HCO.0b013e32834fe8df

Management - General Measures

Fact Explanation
Educate the patient. Educate the patient and family about the condition. Discuss with the patient about available management options. [1],[2]
Maintaining healthy weight Advise patients to maintain desired weight and BMI <25kg/m2. Emphasize importance of weight monitoring. Patients may be asked to monitor body weight daily. Weight gain of 3 or more pounds over 1 or 2 days may indicate fluid buildup. [1],[2]
Consume a healthy diet Large meals should be avoided, If necessary weight reduction is advised. Salt restriction is necessary and foods rich in salt should be avoided. Advise patient to consume a diet rich in vegetables and fruits with low cholesterol and low saturated fat. [1],[2]
Avoid excessive drinking Alcohol has a negative inotropic effect and heart failure patients should restrict or consume in moderate amount. [1],[2]
Stop smoking Smoking is a major cardiovascular risk factor. Smoking should be stopped. Can get help from anti smoking clinics. [1],[2]
Avoid NSAID. NSAID has a fluid retention action. Therefore over the counter medicines for pain should be avoided. [1],[2]
Avoid anemia Anemia exacerbates heart failure symptoms. [3]
Treat other co morbidity Treat hypertension, diabetes and dyslipidemia. They increase the cardiovascular risk. [1]
References
  1. LANZA GA, CREA F. Primary coronary microvascular dysfunction: clinical presentation, pathophysiology, and management. Circulation [online] 2010 Jun 1, 121(21):2317-25 [viewed 07 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.109.900191
  2. FIGUEROA MS, PETERS JI. Congestive heart failure: Diagnosis, pathophysiology, therapy, and implications for respiratory care. Respir Care [online] 2006 Apr, 51(4):403-12 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16563194
  3. BEN-DOR I, BATTLER A. Erythropoietin treatment for ischemic cardiomyopathy: anemia correction and myocardial protection. Timely Top Med Cardiovasc Dis [online] 2007 Dec 11:E33 [viewed 07 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18301786

Management - Specific Treatments

Fact Explanation
Pharmacological treatment: Step 1 Angiotensin converting enzyme inhibitors (ACEi) and Beta-blockers should be used in all patients with a recent or remote history of MI regardless of Ejection Fraction (EF) or presence of heart failure (HF). Angiotensin converting enzyme inhibitors should be used in patients with a reduced EF and no symptoms of HF. ACEi inhibits angiotensin converting enzyme. It results in inhibiting aldosterone production and reducing preload. By vasoconstriction it reduces afterload. It has both symptomatic and survival benefit. Beta blockers acts by blunting of activated sympathetic nervous system. This is useful in chronic stable heart failure patients. Angiotensin receptor blocker (ARB) should be administered to post-MI patients without HF who are intolerant of ACE inhibitors and have a low EF. ARB binds to angiotensin receptors and acts as ACEi. It has both symptomatic and survival benefit. [4],[5]
Pharmacological treatment: Step 2 Patients with previous or current HF symptoms are treated with loop diuretics and/or digoxin in addition to Step 1. Loop diuretics inhibits sodium reabsorption in the thick ascending limb of loop of henle and increases the sodium and water loss. It results reducing preload. By vasodilatation also it reduces preload. This drug gives symptomatic benefit most rapidly. Digoxin is a cardiac glycoside. It increases the contractility of the heart. Useful in symptomatic chronic heart failure. Digoxin should not be used in patients with low EF, sinus rhythm, and no history of HF symptoms. [4],[5]
Pharmacological treatment: Step 3 Add aldosterone antagonists to Step 2. They inhibits sodium reabsorption in distal convoluted tubule. Useful in symptomatic patients. Cardiac resynchronization is performed if bundle branch block is present in a patient without symptoms of HF. Perform revascularization to appropriate patients. Valve replacement or repair should be recommended for patients with hemodynamically significant valvular stenosis or regurgitation and no symptoms. of HF.[1],[2],[3],[4],[5]
Pharmacological treatment: Step 4 For patients with refractory symptoms special interventions such as inotropes administration, ventricular assisted devices are required. Some people may benefit from the heart devices such as single or dual chamber pacemaker, biventricular pacemaker, and left ventricular assist device (LVAD). Placement of an implantable cardioverter-defibrillator (ICD) is reasonable in ischemic cardiomyopathy patients who are at least of post-MI days of 40 , have an of 30% or less LVEF , are NYHA functional class I on chronic optimal medical therapy, and have reasonable expectation of survival with a good functional status for more than 1 year. [1],[2],[3],[4],[5]
Pharmacological treatment: Step 5 A heart transplant may be recommended for patients who have failed all the standard treatments and still have very severe symptoms. Recently, implantable, artificial heart pumps have been developed. [1],[2],[3],[4],[5]
References
  1. BORIANI G, GASPARINI M, LANDOLINA M, LUNATI M, BIFFI M, SANTINI M, PADELETTI L, MOLON G, BOTTO G, DE SANTO T, VALSECCHI S, INSYNC/INSYNC ICD ITALIAN REGISTRY INVESTIGATORS. Effectiveness of cardiac resynchronization therapy in heart failure patients with valvular heart disease: comparison with patients affected by ischaemic heart disease or dilated cardiomyopathy. The InSync/InSync ICD Italian Registry. Eur Heart J [online] 2009 Sep, 30(18):2275-83 [viewed 07 July 2014] Available from: doi:10.1093/eurheartj/ehp226
  2. GASPARINI M, MENOZZI C, PROCLEMER A, LANDOLINA M, IACOPINO S, CARBONI A, LOMBARDO E, REGOLI F, BIFFI M, BURRONE V, DENARO A, BORIANI G. A simplified biventricular defibrillator with fixed long detection intervals reduces implantable cardioverter defibrillator (ICD) interventions and heart failure hospitalizations in patients with non-ischaemic cardiomyopathy implanted for primary prevention: the RELEVANT [Role of long dEtection window programming in patients with LEft VentriculAr dysfunction, Non-ischemic eTiology in primary prevention treated with a biventricular ICD] study. Eur Heart J [online] 2009 Nov, 30(22):2758-67 [viewed 07 July 2014] Available from: doi:10.1093/eurheartj/ehp247
  3. BENETIS R, SIMUKAUSKIENE A, JANKAUSKIENE L, KAVOLIūNIENE A. [Ischemic cardiomyopathy: possibilities of surgical treatment]. Medicina (Kaunas) [online] 2007, 43(11):909-17 [viewed 07 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/18084150
  4. LANZA GA, CREA F. Primary coronary microvascular dysfunction: clinical presentation, pathophysiology, and management. Circulation [online] 2010 Jun 1, 121(21):2317-25 [viewed 07 July 2014] Available from: doi:10.1161/CIRCULATIONAHA.109.900191
  5. FIGUEROA MS, PETERS JI. Congestive heart failure: Diagnosis, pathophysiology, therapy, and implications for respiratory care. Respir Care [online] 2006 Apr, 51(4):403-12 [viewed 09 July 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/16563194