Approach to the Patient with a Respiratory Disorder PDF

Approach to the Patient with a Respiratory Disorder  Anatomic and Physiologic Considerations: The respiratory system is comprised of several elements including the central nervous system, the chest wall, the pulmonary circulation, and the respiratory tract. The bronchial branches ar...

Approach to the Patient with a Respiratory Disorder  Anatomic and Physiologic Considerations: The respiratory system is comprised of several elements including the central nervous system, the chest wall, the pulmonary circulation, and the respiratory tract. The bronchial branches are conducting airways and do not participate in gas exchange. Gas exchange takes place in the branches from the respiratory bronchioles to the alveoli, called the respiratory zone. The alveolar lining cells are predominantly flat, type I pneumocytes while type II pneumocytes, about 5% of the alveolar lining cells, are round and secrete surfactant. The right lung is divided into upper, middle, and lower lobes, while the left lung is divided into upper, and lower lobes, each of which is further subdivided into segments.  The primary function of the lungs is gas exchange. The entire cardiac output goes through the lungs, where oxygen is absorbed and carbon dioxide is removed from blood. Gas exchange requires adequate cardiac output, alveolar ventilation, alveolar-capillary surface area, and regional matching of blood flow to ventilation.  Ventilation Ventilation is the movement of air in and out of the lungs. During inspiration, active contraction of the respiratory muscles increases intrathoracic volume and air enters the lung. Exhalation is passive in normal lungs and begins when inspiratory muscles relax. With active contraction of expiratory muscles, emptying additional volume from the lung. In disease states such as emphysema, when the elastic recoil of the lung is greatly diminished, active contraction of the expiratory muscles is required to empty enough air from the lungs.  The primary respiratory muscle is the diaphragm. The so-called accessory muscles of respiration-the intercostal, sternocleidomastoid, scalene, and abdominal muscles-normally contribute little.  Compliance Compliance is the change in lung volume produced by a given change in transpulmonary pressure. Compliance is decreased in diseases such as pulmonary fibrosis or pulmonary edema, which restrict lung volume expansion. Compliance is increased in emphysema because of the loss of elastic recoil.  Control of ventilation: Ventilation is the primary short-term homeostatic mechanism for maintaining normal blood pH, the strongest factor controlling ventilation. The partial pressure of carbon dioxide (PCO2) in blood is inversely proportional to the minute ventilation. Hypoxia is the second strongest drive to ventilation.  Gas transfer Gas transfer: Oxygen and carbon dioxide are easily dissolved in plasma. The majority of O2 contained in the blood is bound to hemoglobin, with a small fraction dissolved measured as the Pao2. Each molecule of hemoglobin is capable of carrying four molecules of oxygen.  The oxygen-hemoglobin dissociation curve It is a graph of the relationship between Pao2 and hemoglobin saturation. Decreased blood pH, increased temperature, increased 2,3-diphosphoglycerate, and increased Paco2 all act to decrease the affinity of hemoglobin for oxygen, which facilitates unloading of oxygen into tissues( shift to the right). Carbon monoxide binds hemoglobin with 240 times greater affinity than does oxygen at the same sites and also induces cooperative binding. Binding of hemoglobin by carbon monoxide decreases the oxygen content of blood by decreasing the amount of oxygen bound to hemoglobin.  shifts to right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. enhanced oxygen delivery to tissues Shifts to Right = Raised oxygen delivery raised [H+] (acidic)PH is low raised pCO2 raised 2,3-DPG raised temperature  shifts to left = for given oxygen tension there is increased saturation of Hb with oxygen i.e. decreased oxygen delivery to tissues Shifts to Left = Lower oxygen delivery HbF, methaemoglobin, carboxyhaemoglobin low [H+] (alkali)PH is high low pCO2 low 2,3-DPG low temperature  Pulmonary Gas Exchange The degree of gas exchange depends on four main factors: (1) matching of ventilation with perfusion, (2) ventilation, (3) shunt, and (4) diffusion.  INTRODUCTION Patients with respiratory illness typically present with characteristic symptoms. The most common symptoms include dyspnea (shortness of breath) and cough. Less common symptoms include hemoptysis (coughing up blood) and chest pain. A proper approach always begins: with a detailed history: Regarding the nature of present symptom, information regarding the patient’s past medical , occupational, family, and social history, A careful physical examination And appropriate diagnostic testing. HISTORY OF THE PRESENT ILLNESS Dyspnea Shortness of breath is a common symptom of both respiratory and cardiac disease. Elements of the history including:  Timing and onset.  The duration of dyspnea.  Exacerbating and alleviating factor.  Extent of physical impairment and severity assessment.  Associated feature.  Clinical grades of severity of dyspnea Grade 0: no dyspnea except with strenuous exercise. Grade 1: slight dyspnea on hurrying on a level of surface or walking up a hill. Grade 2: dyspnea while walking more than 100 yards. Grade 3: : dyspnea while walking less than 100 yards or after few minutes. Grade 4: dyspnea on dressing or undressing. Grade 5: dyspnea at rest.  CAUSES OF DYSPNOEA Acute dyspnoea at rest Cardiovascular Acute pulmonary edema Respiratory Acute severe asthma Acute exacerbation of COPD Pneumothorax Pneumonia Pulmonary embolus Acute respiratory distress syndrome Inhaled foreign body (especially in the child) Others Metabolic acidosis (e.g. diabetic ketoacidosis, lactic acidosis, uremia, overdose of salicylates, ethylene glycol poisoning) Psychogenic hyperventilation (anxiety or panic-related)  Chronic exertional dyspnoea Cardiovascular Chronic heart failure Myocardial ischemia Respiratory COPD Chronic asthma Bronchial carcinoma Interstitial lung disease (sarcoidosis, fibrosing alveolitis, extrinsic allergic alveolitis, pneumoconiosis) Chronic pulmonary thromboembolism Lymphatic carcinomatosis. Large pleural effusion. Others Severe anemia Obesity  Cough and Hemoptysis Cough occurs secondary to irritation of the mucous membrane along the respiratory tract. It is typically classified into one of two categories: acute cough (lasting 4 weeks).  The three most common causes of chronic cough (accounting for >90% of cases in nonsmokers) include: postnasal drip. asthma. and gastroesophageal reflux.  A proper approach to cough  Timing and duration (Nocturnal cough disrupting sleep is common in asthma. Occupational asthma and exposure to dusts and fumes. Occult gastro-esophageal reflux disease (GORD) and chronic sinus disease with associated postnasal drip cause daytime cough. Angiotensin-converting enzyme (ACE) inhibitors cause a dry cough, particularly in women. Coughing during and after swallowing liquids suggests neuromuscular disease of the oropharynx.  The presence or absence of sputum specifically ask about this sputum: Amount How much sputum is coughed up each day? Is it a small (a teaspoonful) or large (a teacupful) amount? Color. and presence or absence of blood in the sputum  associated features  Appearance of sputum: There are many types of sputum. Clear, watery( Acute pulmonary edema) , Frothy, pink( Alveolar cell cancer), Mucoid Clear,( Chronic bronchitis/COPD) , White, viscid( Asthma ), Purulent Yellow( Acute bronchopulmonary infection, Asthma), and Green Longer-standing infection like Pneumonia, Bronchiectasis ,  Causes of cough Acute cough (4 weeks) Normal chest X-ray GERD Asthma Drugs, especially ACE inhibitors Post viral bronchial hyper-reactivity Rhinitis/sinusitis Cigarette smoking Irritant dusts/fumes  'Red flag' symptoms associated with cough that should prompt a chest X-ray Haemoptysis Breathlessness Fever Chest pain Weight loss  Hemoptysis Coughing up blood (haemoptysis).  Clarify whether the blood was coughed up (respiratory tract), vomited (upper gastrointestinal tract) or suddenly appeared in the mouth without coughing (nasopharyngeal).  Amount and appearance Establish the volume and nature of the blood. Blood- streaked clear sputum or blood clots in sputum for more than a week suggest lung cancer. Haemoptysis with purulent sputum suggests an infective cause. Massive hemoptysis, which is defined as the expectoration of more than 600 mL of blood in 24 hours, is most frequently occur in lung cancer, bronchiectasis and tuberculosis.  CAUSES OF HAEMOPTYSIS  Bronchial disease (Carcinoma, Bronchiectasis ) Parenchymal disease (Tuberculosis , Suppurative pneumonia ,Lung abscess) Lung vascular disease (Pulmonary infarction , Polyarteritis nodosa , Goodpasture's syndrome ) Cardiovascular disease (Acute left ventricular failure, Mitral stenosis) Blood disorders (Leukaemia , Haemophilia, Anticoagulants)  Chest Pain Chest pain is a nonspecific symptom that can occur from a host of disease processes involving the respiratory, cardiac, GI, musculoskeletal, and neurological systems. Chest pain of respiratory origin can be distinguished from most nonrespiratory causes of chest pain in that it is almost always respirophasic in nature (i.e., increases with forced inhalation or exhalation or during spontaneous breathing), or when increased as pressure is applied to the chest wall. Sometimes this is referred to as pleuritic pain.  CAUSES OF CHEST PAIN Central Cardiac (Myocardial ischaemia, Myocardial infarction , Myocarditis , Pericarditis , Mitral valve prolapse syndrome) Aortic (Aortic dissection , Aortic aneurysm) Oesophageal ( Oesophagitis , Oesophageal spasm) Massive pulmonary embolus Mediastinal (Tracheitis , malignancy) Peripheral Lungs/pleura (Pulmonary infarct , Pneumonia , Pneumothorax Connective tissue disorders ) Musculoskeletal (Osteoarthritis , rib fracture/injury syndrome) Neurological (Herpes zoster , thoracic outlet syndrome)  ADDITIONAL HISTORY past medical history social history: information regarding smoking, occupational/environmental exposure, and risk factors for AIDS. Questions regarding smoking history should be focused on determining the intensity , duration ,as well as the time of first cigarette, which is a marker of severity of addiction.  PHYSICAL EXAMINATION The general appearance is important for the physical exam. in any patient, especially one who presents with respiratory symptoms. Distress displayed by a patient with a respiratory condition can be a sign of a life-threatening illness. Although complaints of shortness of breath can be subjective, looking for signs of respiratory distress, such as cyanosis or the inability to speak in complete sentences, is critical. A patient’s body habitus can also be telling. Obesity is associated with a number of respiratory conditions, and cachexia can be a sign of cancer or AIDS, both of which are associated with respiratory disorders. In children with serious respiratory disorders, such as severe chronic asthma and cystic fibrosis, growth and development can be delayed. Finally, smelling alcohol or cigarette smoke.  Examination of the thorax Examination of the thorax should be approached in an organized sequence: inspection, palpation, percussion, and auscultation. On inspection: the rate and pattern of breathing should be observed. the chest wall should be examined for signs of deformities or asymmetry. Any impairment in respiratory movement on one or both sides should be noted, and the interspaces should be checked for abnormalities of retraction ( severe asthma, COPD, or upper airway obstruction, whereas a unilateral impairment or lagging of respiratory movement is suggestive of underlying lung or pleural disease (e.g., fibrosis, lobar pneumonia, pleural effusion). On palpation, the chest wall should be palpated for tenderness and fremitus. Fremitus refers to the palpable vibration transmitted along the bronchopulmonary tree during speech A decreased vibratory sense can be seen in conditions such as pleural effusion in which the accumulation of fluid in the pleural space causes a dampening of vibration. Fibrosis, COPD, and pneumothorax are other conditions that can cause a decrease in fremitus. Fremitus is increased when the transmission of sound is increased as in the consolidated lung of pneumonia.  Percussion of the chest wall allows the physician to determine whether the underlying tissue is air- or fluid- filled or solid. In the normal lung, produce a resonant sound. In conditions, such as pleural effusion or lobar pneumonia, in which fluid replaces the air-containing lung and dullness replaces the resonant sound. Dullness to percussion can also be heard when solid tissue replaces the air-filled lung, such as with pulmonary fibrosis or lung cancer. Hyperresonance can be heard bilaterally in the hyperinflated lung, such as with emphysema or asthma, whereas unilateral hyperresonance suggests the presence of a large pneumothorax.  On auscultation, the quality, intensity, and presence of extra breath sounds should be determined.  The quality of breath sounds in normal lungs are characterized as bronchial, vesicular, or bronchovesicular. Bronchial breath sounds are loud, high-pitched, and characteristically heard over the central airways. Vesicular breath sounds are soft, low-pitched, and heard best at the periphery and at the base of the lungs; they are heard through inspiration and continue without pause through expiration. Bronchovesicular breath sounds are a combination of both bronchial and vesicular breath sounds and are heard best over medium-sized airways; inspiratory and expiratory sounds are about equal in length and, at times, separated by a silent interval. If bronchial or bronchovesicular breath sounds are heard in sites distant from their typical location, the air-filled lung has likely been replaced by fluid-filled or solid lung tissue.  The intensity of the breath sounds should be noted. They may be decreased when airflow is decreased, as with obstructive lung disease, or they may be decreased when the transmission of sound is decreased, as with pleural effusion, pneumothorax, or emphysema. The most common adventitious (extra) breath sounds not heard in normal lungs include wheezes, rales, and rhonchi. Wheezes are relatively high-pitched sounds can be heard in which the airways have narrowed or become obstructed, such as with asthma, obstructive lung disease. Rales, or “crackles,” are described as either fine or coarse. Fine crackles are soft, high pitched sounds that are heard most commonly at the lung bases. They are produced in the patient with pulmonary edema, and interstitial fibrosis. Coarse crackles are loud, they result from the presence of mucus in the airways and can be seen in conditions such as bronchiectasis. Rhonchi are relatively low-pitched sounds that have a snoring quality and result from the presence free liquid in the airway lumen. Other adventitious breath sounds include friction rubs and strider.  DIAGNOSTIC TESTING Worldwide, chest radiography is the most commonly performed imaging procedure the films should be obtained with the patient inhaling to total lung capacity. These images provide views of the lungs, mediastinum, and chest wall simultaneously. Chest radiography (chest X-ray) is often the initial diagnostic study of choice in patients presenting with symptoms of respiratory disease. computed tomography (CT) of the chest. Findings on chest CT are more sensitive than plain radiography. CT testing is particularly useful in cases of trauma, evaluation of pulmonary embolism (spiral CT), and in the diagnosis of primary and secondary neoplasia.  Magnetic resonance imaging (MRI) depends on the magnetic properties of hydrogen atoms. Because of its soft tissue specificity, MRI has applications in the assessment of chest wall invasion, mediastinal infiltration, and diaphragmatic involvement by lung cancer or malignant mesothelioma. Fluorodeoxyglucose positron emission tomography (FDG-PET). This technique has proved helpful in studying intrathoracic tumors and has facilitated the work-up of solitary pulmonary nodules.  Pulmonary Function Tests Lung function tests are essential to measure a person's objective ability to move the ventilatory apparatus in comparison with normal subjects, adjusted for sex, height, and age.  INTRODUCTION Pulmonary function tests (PFTs) refer to a panel of tests including:  spirometry( which is a record of exhaled volume versus time during a forced exhalation) measurement of lung volumes  diffusion capacity for carbon monoxid (DLCO)(which measures the transfer of carbon monoxide to indicate how well inspired gases cross the alveolar-interstitial- capillary endothelial interface into blood).  and noninvasive pulse oximetry, for oxygen saturation measured at rest or during ambulation.  OBSTRUCTION We first review the basic types of pulmonary disorders (obstructive versus restrictive), and then discuss the main types of PFTs. Obstructive lung diseases have in common decreased airflow during expiration. The three classic obstructive diseases are asthma, chronic bronchitis, and emphysema. They are defined on spirometry as having a volume of air in the first second of forced expiration (FEV1), which is less than 70 to 80% of the predicted value matched for age and gender.  RESTRICTION Decreased lung volumes characterize restrictive lung diseases. They are defined as having a total lung capacity (TLC) less than 80% of predicted. Extrinsic causes: include decreased chest wall compliance (e.g., obesity, kyphoscoliosis, concentric chest wall burns) and weakening of the muscles of respiration (e.g., neuromuscular disorders). Intrinsic defects are within the lung itself (e.g., interstitial lung disease, congestive heart failure).  Spirometry Spirometry measures changes in lung volume over time during forced breathing maneuvers. The patient is instructed to take a full inspiration and then exhales as forcefully as possible for as long a possible. The total volume of expired air is the forced vital capacity (FVC). Air expired in the first second of that maneuver is the FEV1. Spirometry is one of the easiest and inexpensive PFTs.  INTERPRETING RESULTS An FEV1 of less than 70 to 80% of predicted suggests obstruction. The FVC may be normal or decreased, but to a lesser degree than the FEV1. An FEV1:FVC ratio of less than 0.7 is characteristic of obstruction. Classically, FEV1 and FVC are both reduced in restriction, but the ratio of FEV1:FVC is normal or increased. An FEV1:FVC ratio of more than 0.7 suggests restriction  Spirometry Terms Obstruction Restriction Forced expiratory volume (FEV)1, Decreased, , Normal is the volume of air that is forcefully 30% in children N/A flow rate during expiration >20% in adults The forced expiratory flow (FEF)25–75%, when decreased, is used as an indicator of small airways disease. The slow vital capacity (SVC) can be used to differentiate restriction from obstruction in patients in which both FEV1 and FVC are decreased. If obstruction is suspected by initial spirometry, the test can be repeated 10 minutes after administration of a bronchodilator, such as albuterol.  Flow–Volume Loops Plotting flow (y-axis) versus volume (x-axis) during forced maximal inspiration and expiration can be helpful in determining the site of lung obstruction. Restrictive lung disease also gives a distinctive flow–volume loop pattern.  CARBON MONOXIDE DIFFUSION Also called the “transfer function,” the diffusion capacity (DLCO) measures the ability of the alveolar capillary membrane to diffuse gases. The patient is required to inhale a harmless, composite gas (usually 10% helium and 0.3% CO) and hold their breath for 10 seconds. The exhaled breath is then analyzed for dilution of helium and uptake of CO. A DLCO of less than 74% predicted is considered mild impairment. Severe impairment is defined as less than 40% predicted 1. Obstruction: DLCO is decreased in obstruction when there is anatomic destruction of the alveoli (emphysema). This makes DLCO measurement a good way to differentiate chronic bronchitis and asthma from emphysema. 2. Restrictive disease: DLCO is most useful in differentiating intrinsic restrictive lung disease from extrinsic disease. A decreased DLCO is seen in significant interstitial lung disease (intrinsic), whereas normal values are typically seen in other causes of decreased lung volume, such as obesity, neuromuscular diseases, kyphoscoliosis, and pleural scarring. DLCO is often used to follow patients at risk. This may be helpful in patients receiving chemotherapy (e.g., bleomycin), radiation to the chest, or amiodarone. An abnormal DLCO may be a clue to pulmonary vascular disease in the patient with normal spirometry and dyspnea (10). This includes chronic recurrent pulmonary emboli, primary pulmonary hypertension, and vasculitis. It is important to note that DLCO can be abnormally low in patients with anemia or who have been recently smoking (secondary to increased carboxyhemoglobin levels). It can be abnormally high in polycythemia, severe obesity, mild heart failure (increased blood in the pulmonary capillaries without pulmonary edema), and if the patient has exercised just before the test (increased cardiac output).  Other tests commonly utilized in the evaluation of patients with respiratory disease include pulmonary function testing, arterial blood gas analysis, pulse oximetry, and bronchoscopy.  Dyspnea algorithm Low FEV1/FVC Yes no Obstruction low FVC Low FVC yes no yes no Rule out restriction of obstruction restrictive defect asthma suspected combined defect Measure lung volume reversable with bronchodilator DLCO yes no Normal decrease yes no normal low methacholine test DLCO Obstruction restrictive asthma emphysema extrinsic intrinsic normal low non pulmonary workup pulmonary vasculer disease