Intern Survival Guide Dyspnea Shortness of Breath Hypoxia and

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Intern Survival Guide Dyspnea Shortness of Breath Hypoxia and Powered By Docstoc
					       Intern Survival Guide                    Dyspnea (Shortness of Breath)

     Department of Emergency Medicine             An awareness of the need for an
        National Taiwan University Hospital       increase in pulmonary ventilation
                                                  Subjective breathlessness at rest or
        Dyspnea: DDx and Mx                       less exertion than in the past

            Tsung-Chien Lu, MD, MS

Hypoxia and Hypoxemia                           Hypoxemic Respiratory Failure
 Hypoxia: The reduction of oxygen                 Occurs when a patient’s Pao2 falls
 availability in tissues
                                                  so low that it is life-threatening or
                                                  has serious adverse physiologic
 Hypoxemia: arterial oxygen tension (PaO2)
 < 60mmHg, or arterial oxygen saturation
 (SaO2) < 90%

                                                Arterial Oxygen Tension (PaO2)
Tissue Hypoxia: Mechanisms
                                                  Normal value in healthy adult breathing room air
 Impaired delivery                                at sea level ∼ 97 mm Hg.
                                                  ↓ progressively with ↑ age
  – Circulatory (Forward Failure,
                                                  Dependant upon
                                                       1. FiO2
  – Distributive (sepsis)                              2. Patm
  – Defective blood-O2 transport (congenital/     Hypoxemia is PaO2 < 80 mm Hg at RA
    acquired hemoglobinopathies)                  Most pts who need ABG usually require O2
                                                  O2 therapy should not be withheld/interrupted
                                                  ‘to determine PaO2 on RA’

Acceptable PaO2 Values on Room Air                    Inspired O2 – PaO2 Relationship

Age Group                    Accepable PaO2 (mm Hg)   FIO2 (%)                 Predicted Min PaO2
                                                                               (mm Hg)
Adults up to 60 yrs &        > 80                     30                       150
                                                      40                       200
Newborn                      40-70
70 yrs                       > 70                     50                       250
80 yrs                       > 60                     80                       400
90 yrs                       > 50                     100                      500

         60 yrs ∼ 80 mm Hg    ↓ 1mm Hg/yr              If PaO2 < FIO2 x 5, pt probably hypoxemic at RA


  Low inspired O2 (High Altitude)
  Shunt (atrial septal defect, pulmonary A-V
  Ventilation Perfusion Mismatch (COPD,
  Pulmonary Emboli)
  Diffusion Impairment (Interstitial lung
  Alveolar Hypoventilation

Hypercapnic Respiratory Failure                       Hypercapnic Respiratory Failure

  Occurs when a patient’s Paco2                         Increased CO2 production (respiratory
  rises to greater than normal, that is,
                                                        Increased dead space (e.g., COPD, Asthma,
  greater than 45 mmHg.                                 Chest wall abnormalities)
                                                        Decreased minute hypoventilation
                                                        (neurological dis., drugs, hypothyroidism,
                                                        chest wall abnormalities)

                                                Acute onset dyspnea
                                                (+ chest discomfort)-DDX
                                                  Cardiac (+ pulm congestion)
  Acute onset          Gradual onset               – myocardial ischemia
  – (+ chest pain)     – (Exertional Dyspnea)      – valvular (mitral)
                                                   – bronchoconstriction
                                                   – pneumothorax
                                                   – pulmonary emboli
                                                   – Aortic dissection

Gradual onset Dyspnea / Dyspnea on Effort       Gradual onset Dyspnea / Dyspnea on Effort
-History                                        -Physical Examination
  severity, frequency                             general (respiratory rate, cyanosis, clubbing)
  paroxysmal nocturnal dyspnea                    cutaneous, articular
  orthopnea, platypnea, trepopnea                 chest & lung exam
  chest pain/ pleurisy                            CHF signs, increased S2, TR
  cough/ wheezing                                 leg edema, varicose veins, DVT
  habits (smoking)/ occupation
  extra-thoracic complaints

Gradual onset Dyspnea / Dyspnea on Effort
- Initial lab workup
                                                Alveolar Gas Equation
  complete blood count, electrolytes, kidney     PAO2 = FiO2 x (PB – PH2O) – PaCO2/R
  & liver function                                    = 137 – PaCO2/0.8
  ECG                                            A-a gradient = PAO2 - PaO2 (normal => 12-20)
  chest radiograph                              A – Alveolar
  arterial blood gases                          a – arterial
                                                FIO2 – Fractional oxygen content
   – A-a O2 Gradient                            in inspired air
                                                PB - Barometric pressure
                                                PH2O – Water vapor pressure
                                                R – Respiratory quotient

Alveolar-Arterial O2 Gradient                   Common Causes of Dyspnea
 A normal A-a gradient in the face of             Asthma, COPD, bronchitis
 hypoxemia suggests the hypoxemia is due to       Pneumonia
 hypoventilation and not due to underlying
 lung disorders.                                  Croup, bronchiolitis
 An increased A-a gradient identifies             CHF, AMI, myocardial ischemia
 decreased oxygen in the arterial blood           Pleuritis, pleural effusion
 compared to the oxygen in the alveolus. This
                                                  Pulmonary embolism
 suggests a process that interferes with gas
 transfer (ventilation-perfusion mismatch) or     Hyperventilation

Other Causes of Dyspnea                         Congestive cardiac failure
 Interstitial lung disease
 Endobronchial foreign bodies

Jugular Venous Engorgement                      Pericardial Effusion

Pneumonia (RML)   Lung Abscesses

Emphysema         Pulmonary Fibrosis

Pneumothorax      Less Common Causes of Dyspnea
                   Spontaneous pneumothorax
                   Primary pulmonary hypertension
                   Cardiac Tamponade
                   Laryngeal or tracheal obstruction
                   Superior vena cava syndrome

Dyspnea                                         Dyspnea
 Anxiety                                        Fever-infectious causes
 -Hyperventilation                                Pneumonia
  a diagnosis of exclusion                        Trachiobronchitis

Dyspnea                                         Dyspnea
 Cough: asthma, pneumonia, bronchitis,            Pedal edema, PND (paroxysmal nocturnal
 COPD, CHF                                        dyspnea), orthopnea: CHF (CAD, H/T)
 Cough                                            Angina: myocardial ischemia
 with purulent sputum: bacterial                  Smoking, calf swelling and tenderness: pulmonary
 with clear sputum: viral infection               embolism
                                                  Chest pain: pleuritis, pericarditis
 with pink, frothy sputum: CHF
                                                  Tall, thin, young, with sudden onset of dyspnea
 Chronic cough with purulent sputum (> 3
                                                  and pleuritic pain: spontaneous pneumothorax
 months): chronic bronchitis

Dyspnea-PE                                      Dyspnea-PE
 Respiratory Distress Sign                        CHF: JVE (Jugular venous engorgement),
 -Accessory muscle: suprasternal, intercostal     rales,S3 gallop, hepatosplenomegaly,
 retraction, nasal flaring                        ascites, pedal edema
 Fever-Infection                                  Pulmonary H/T: loud P2
 Asthma, COPD-Pulsus paradoxus, prolong           Cardiac tamponade: paradoxical pulse, JVE,
 E phase, wheezing                                distant heart sound, tachycardia,
 Consolidation-crackle, egophony, whisper         hypotension, dyspnea, clear lung

Dyspnea-PE                                                             Diagnostic test
 Intersitial lung disease: dry rales                                     ABG: hypoxemia, metabolic acidosis,
 Pleural effusion:                                                       hypercapnea
  dullness to percusion, BS decrease                                     Chest X-ray: Upright PA view,
 Stridor:                                                                pneumothorax, end-expiratory
 upper airway obstruction                                                CBC/DC: infection, bacterialor viral
 endobronchial foreign body                                              Sputum exam and culture: infection
 epiglottitis                                                            Lateral neck X-ray: epiglottitis, subglottitis,
 croup                                                                   and foreign body

Dyspnea: Differential Diagnosis
  Cardiac                            Metabolic
   – Left ventricular failure         – Metabolic acidosis
   – Pulmonary oedema

                                                                       You’re called to see a patient with
                                      – Anaemia
   – Dilated cardiomyopathy           – Thyrotoxicosis
   – Mitral valve disease             – Psychogenic hyperventilation
   – Aortic stenosis

                                                                       shortness of breath…
   – Arrhythmias                     Neuromuscular
   – Pericardial effusion             – Kyphoscoliosis
                                      – Ankylosing spondylitis
  Respiratory                         – Muscular dystrophy
   – Pulmonary embolism               – Poliomyelitis
   – Pulmonary fibrosis               – Myasthenia gravis
   – Lung tumour                      – Guillain-Barré syndrome
   – Pneumonia
   – Pneumothorax
   – Pleural effusion
   – Asthma
   – COPD
   – Bronchiectasis
   – Lung collapse
   – Primary Pulmonary Hyprtension

Acute dyspnea                                                          Acute dyspnea
 What to do first:                                                       What do you want to do when you arrive??
 -on the phone, ask the nurse for the vitals                             Review the vital signs
 (including pulse oximetry)                                              Visually assess the patient
 -ask the nurse how the patient looks                                    Examine the patient focusing on the cardiac
                                                                         and pulmonary exams:
 -on your way to see the patient, review the
 handout                                                                 -wheezing, crackles, peripheral edema,
                                                                         asymmetric peripheral edema?
                                                                         -cardiac rhythm

Acute dyspnea                                        Acute dyspnea
                                                      Your physical exam may help you narrow
                                                      the differential.
       pulmonary           non-pulmonary (cardiac)    Tests to obtain in the acute setting:
        pulm edema            arrhythmias
        asthma/COPD           acute MI
        PE                    myocardial ishemia
                                                      -portable CXR
        pneumonia                                     -EKG
        pneumothorax                                  -cardiac enzymes
Dx of exclusion: anxiety

Management                                           Management
   If not on oxygen, place on nasal cannula           IV diuretics
   If already on oxygen, increase liters per          Bronchodilators
   minute or place on face mask                       Antibiotics
   Noninvasive ventilation with BiPap is the          Anticoagulation
   next step (consider MICU if using NIPPV)


         Department of Emergency Medicine
            National Taiwan University Hospital


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