TRANS - dyspnea_ cyanosis_ hypoxia by repamatmat17


									 `Hypoxia, Cyanosis, Dyspnea
          Dr. R. Zotomayor                              November 10, 2010

HYPOXIA                                                     Signs and Symptoms of Acute Hypoxia

MAIN FUNCTION OF RESPIRATORY SYSTEM:                            Respiratory: Tachypnea, breathlessness,
    Obtain oxygen from external environment &                  dyspnea, cyanosis
      supply it to cells                                        Cardiovascular: Increased cardiac output,
    Remove from the body the carbon dioxide
                                                                palpitations, tachycardia, arrhythmias,
      produced by cellular metabolism
       The main function of the respiratory system             hypotension, angina, vasodilatation, diaphoresis,
         is the exchange of oxygen from the                     and shock
         atmosphere for carbon dioxide produced by              Central nervous: Headache, impaired judgment,
         the cells of the body.                                 inappropriate behavior, confusion, euphoria,
       Other functions for the respiratory system              delirium, restlessness, papilledema, seizures,
         include participation in the acid-base balance         obtundation, coma
         of the body, phonation, pulmonary defense,             Neuromuscular: Weakness, tremor, asterixis,
         and metabolism.                                        hyper-reflexia, incoordination
       An abnormality in chain of gas and/or                   Metabolic: Sodium and water retention, lactic
              blood flow results in impaired                    acidosis
                                                            Severe Hypoxia
                                                                decrease ATP
                                                                cell membrane depolarization
                                                                Ca2+ influx
                                                                activation of Ca2+ dependent phospholipase and
                                                                cell swelling
                                                                cell necrosis


                                                            Systemic Arterioles
                                                            Hypoxia  ↓ ATP  opening of K channels in vascular
                                                            smooth ms cells  systemic arterioles dilate

                                                            Pulmonary Arterioles
                                                            Hypoxia  dec ATP  inhibition of K channels 
                                                            depolarization  activation of voltage gated channels 
                                                            inc cytosolic Ca2+  pulmonary vasculature smooth ms
HYPOXIA                                                     cell contraction  pulmonary arterial constriction 
                                                            blood shunts toward better ventilated portions of the
Reduction in oxygen level                                   lungs

      ↓ O2 availability to cells/ tissues results in       CNS
       inhibition of the respiratory chain and              Hypoxia causes: impaired judgment, motor in-
       ↑anaerobic glycolysis                                coordination, clinical picture resembling acute alcoholism
      Pasteur’s Effect – switch from aerobic to            High altitude illness – cerebral vasodilation  HA,
       anaerobic metabolism w/c results into dec ATP        dizziness, fatigue, insomnia, GI sx, somnolence
       production (drop in O2 level)
                                                            NON-PULMONARY HYPOXIA
   Respiratory: tachypnea
   Vascular: compensatory mechanism inc SV, inc CO,
                                                                   Respiratory Hypoxia:
   inc HR, vasodilatation, diaphoresis,papiledema,
                                                                -   most common cause is ventilation-perfusion
   hypocapnia in the brain
                                                                    mismatch (V/Q mismatch) resulting perfusion of
   Neuro: weakness, tremor, hypereflexia,
                                                                    poorly ventilated alveoli
   Metabolic: Na and H2O retention
                                                                -   may also be caused by hypoventilation associated
                                                                    with an elevation of PaCO2
                                                                -   may also be caused by shunting of blood across
                                                                    the lung from the pulmonary arterial to the
                                                                                                          1 of 8 Page
    venous bed (intrapulmonary R-L shunting) by             CAUSES OF HYPOXEMIA:
    perfusion of non-ventilated portions of the lung
     dec PaO2                                              1. HYPOVENTILATION
                                                                   o The volume of fresh gas going to the
                        O2                                            alveoli per unit time (alveolar
Alveolar Ventilation = ---------                                      ventilation) is reduced.
                        CO2                                        o If the resting oxygen consumption is
                                                                      not correspondingly reduced,
                                                                      hypoxemia inevitably result.
                                                                   o Commonly caused by diseases outside
                                                                      the lungs; very often the lungs are
                                                            -   Hypoventilation always causes a rise in PC02
                                                                   o Relationship between arterial PC02
                                                                      and level of alveolar ventilation

                                                                           PC02 = VCO2 + K
                                                                    o VC02 = CO2 output
                                                                    o VA = alveolar ventilation
                    Figure: Gas exchange                            o K = constant
   Hypoxia secondary to High Altitude                    If alveolar ventilation is halved, the PC02 is doubled.
-   as one ascends to 3000m, the reduction of the O2
    content of inspired air leads to a dec in alveolar   Disorders where hypoventilation can be seen:
    PO2 to about 60mmHg (High Altitude Illness)                     o Sleep apnea
                                                                           Central sleep apnea
   Hypoxia secondary to R-L extrapulmonary                                Obstructive sleep apnea
    shunting                                                        o Sudden infant Death Syndrome
-   caused by congenital cardiac malformation
    (Tetralogy of Fallot, transposition of great
    vessels)                                             CAUSES OF HYPOVENTILATION:

   Anemia Hypoxia                                              Depression of the respiratory center by drugs
-   ↓ Hb  dec O2 carrying capacity  dec O2                         Barbiturates, morphine derivatives
    transported to the tissues  hypoxia                        Diseases of the medulla
                                                                     Encephalitis, hemorrhage, neoplasm
   Carbon Monoxide Intoxication                                Abnormalities of the spinal cord
-   Carboxy Hb is unavailable for O2 transport  dec                 Following dislocation
    O2 transported to tissues  hypoxia
                                                                Anterior horn cell disease
                                                                     poliomyelitis
   Circulatory Hypoxia
-   venous and tissue PO2 values are reduced as a               Diseases of the nerves to the respiratory
    consequence of reduced tissue perfusion and                 muscles
    greater tissue extraction                                        Guillain-Barre Syndrome
    ex. Strangulating one another.                              Diseases of the myoneural junction
    Mechanism: compressing blood vessels both                        Myasthenia gravis or
    artery and vein, no circulation occurs                             anticholinesterase poisoning
                                                                Diseases of the respiratory muscles
   Specific Organ Hypoxia                                           Progressive muscular dystrophy
-   Atherosclerosis  arterial obstruction  dec                Thoracic cage abnormalities
    perfusion  hypoxia
                                                                     Crushed chest
-   Raynaud’s disease  vasoconstriction  dec
                                                                Upper airway obstruction
    perfusion  hypoxia
                                                                     Tracheal compression

                                                                                                     2 of 8 |Page
      o Means that equilibrium is not reached           - Low compliance (pulmonary fibrosis, lack of
         between the P02 in the pulmonary                  surfactant)
         capillary blood and alveolar gas               - High airway resistance (asthma, COPD)
                                                        - Extrinsic Compression of Alveoli
                                                           (Compression atelectasis due to hydrothorax
                                                           or pneumothorax)

                                                      Other causes:
                                                         - venous obstruction
                                                         - expansion of interstitial fluid / edema  arterial
                                                             compression  dec perfusion  hypoxia
                                                         - ↓ cardiac output & Hypovolemic shock 
                                                             compensatory mechanism: vasoconstriction 
                                                             dec perfusion  hypoxia
                                                         - ↑ O2 requirements
                                                         - ↑ metabolic rate
                                                         - ↑ O2 consumption w/o inc in perfusion 
                                                             hypoxia e.g. fever, thyrotoxicosis, exercise
       Changes in P02 along the Pulmonary Capillary      - Improper O2 utilization
                                                         - Cyanides and other poisons bind to tissues
                                                             making them unable to utilize O2
      o Means that some blood reaches the
         arterial system without passing              MIXED CAUSES OF HYPOXEMIA:
         through ventilated regions of the                  Frequently occurs
         lungs.                                             Often impossible to accurately define the
      o Pulmonary                                            mechanism of hypoxemia
              Intrapulmonary shunts like AV
                                                            Oxygen delivery to tissues
                                                                 Oxygen carrying capacity of the blood
              Consolidated Pneumonia
                                                                 Cardiac output
                 where the area is perfused but
                                                                 Distribution of blood flow to the
              ARDS
      o Extrapulmonary
              Congenital heart Diseases

      o Ventilation and blood flow are
         mismatched in various regions of the
         lung resulting to inefficient gas
      o Very common
      o Responsible for most of the
         hypoxemia of COPD, interstitial lung
         disease and vascular disorders like
         pulmonary embolism
      o Usually identified after the other 3
         causes of hypoxemia are excluded.
                                                      ADAPTATION TO HYPOXIA:
      o All lungs have VQ inequality
      o Normal upright lung: regional pattern
                                                      1. Hypoxia  stimulation of chemoreceptors in the
         with VQ ratio decreasing from apex to        carotid and aortic bodies and in the medulla 
         base                                         ↑ventilation  loss of CO2  may lead to respiratory
      o Factors that can exaggerate the               alkalosis
         hypoxemia of VQ inequality
      o Concomitant hypoventilation                   2. Hypoxia  ↓PaO2  dec cerebrovascular resistance
      o Reduction in cardiac output                    cerebral blood flow ↑  O2 delivery to the brain is
                                                                                                  3 of 8 |Page
3. Hypoxia  ↑erythropoietin  ↑erythropoiesis                      -    sensation of breathlessness or inadequate
↑RBC/polycythemia  ↑Hb                                                   breathing is the most common complaint of
                                                                          patients with cardiopulmonary diseases.
ASSESMENT OF SEVERITY:                                                    Evaluation of the complaint is complicated by
     •    Arterial P02 can be used but may be                             the fact that in many circumstances,
          misleading                                                      shortness of breath is a normal consequence
     •    Alveolar-arterial difference for P02                            of exertion. Furthermore, perception of
     •    PA02 = PI02 – PaC02 + F                                         shortness of breath varies considerably
                                                                          among individuals at the same level of fitness
                                                                          and work and even in the same individual
                                                                          performing comparable work at different
ALVEOLAR GAS EQUATION:                                                    times. In disease states, perception of
PAO2 = (PIO2) – (PaCO2/R)                                                 dyspnea can vary greatly among individuals.
PIO2 = (Barometric pressure-Water vapor pressure) x
FIO2                                                           According to ATS/ERS 2000, Dyspnea is
Thus:                                                            • Breathing discomfort
In a normal individual breathing room air:                       • Qualitatively distinct sensations
                PAO2 = (760 – 47) x 0.21 – 40/0.8                •   Physiologic, psychological, social & environmental
                         = 150 – 50                                 factors
                         = 100                                   •   Induce secondary physiological & behavioral
         A-a O2 gradient                                      ROOTWORDS = Greek
             o difference between alveolar and                  • Dys – painful, difficult
                 arterial PO2                                   • Pneuma – breath
             o result of imperfect diffusion, low V/Q
                 areas at the lung bases, and                  MECHANISM OF DYSPNEA
                 physiological shunts

Normal A-aO2 gradient < 20 mmHg
A-a Gradient: PAO2 – PO2
N Less than 15 mmHg ≤ 30
Age ***
Inc ≈ 3 mmHg per decade


 •       Unpleasant awareness of breathing
 •       Subjective
 •       Commonly accompanies cardiac or
         bronchopulmonary diseases
 •       May accompany anxiety
 •       Labored
 •       Sensation of dyspnea is often poorly or vaguely
         described by patient.
 •       Most common complaint of patients with
         cardiopulmonary diseases.
 •       Evaluation of the complaint is complicated by the
         fact that in many circumstances, shortness of
         breath is a normal consequence of exertion.
 •       Perception of shortness of breath varies
         considerably among individuals at the same level of
         fitness and work and even in the same individual
         performing comparable work at different times.
 •       In disease states, perception of dyspnea can vary
         greatly among individuals.

                                                                                                            4 of 8 |Page


                  RESPIRATORY              CARDIO
              Usually more
              gradual in onset      Nocturnal
              Nocturnal             exacerbations
              Usually obvious evidence of cardiac or
              pulmonary disease. Findings may be
              absent at rest when symptoms are present
              only at exertion
              Rarely causes
              dyspnea unless tests
              of obstructive
              disease (FEV1,
              FEV1/FVC) or
function test
              restrictive disease
              (total lung capacity)
              are reduced (<80%
                                    LV ejection fraction
                                    at rest and/or
                                    during exercise
                                    usually depressed in
                                    cardiac dyspnea.
                                                           TIME COURSE: DEVELOPMENT OF BREATHLESSNESS
POSSIBLE MECHANISMS OF DYSPNEA                                           Pneumothorax
   Condition               Mechanism                         Immediate   Pulmonary edema 2 to cardiac arrhythmia
                    Inc sense of effort                                  Inhalation of foreign body
     Asthma         Stimulation of irritant receptors in                 Left heart failure
                    airways                                              Asthma
                    Inc sense of effort                                  Laryngeal edema
                    Hypoxia, Hypercapnia, Dynamic
      COPD                                                     Days      ARDS
                    Airway Compression
                                                                         Left heart failure
                    Afferent Mismatch
   Mechanical                                                            Pleural effusion
                    Factors Assoc with the underlying          Weeks     Anemia
                    condition                                            Muscle weakness
   Pulmonary        Stimulation of pressure receptors in                 Tumors
   Embolism         pulmonary vasculature of R. Atrium                   Pulmonary fibrosis
                                                                         Muscle weakness
                                                                         Muscle weakness
                                                               Years     COPD
                                                                         Chest wall disorders

                                                                                                      5 of 8 |Page
        DIFFERENTIATION BETWEEN CARDIAC AND                         - Decreased Cardiac Output
                   PULMONARY DYSPNEA                                - Elevated Pulmonary Venous Pressure
   1.    Careful history: Dyspnea of lung disease usually           - Right to Left Shunt
         more gradual in onset than that of heart disease;         MISCELLANEOUS
         nocturnal exacerbations common with each. Pink             - Anemia
         frothy sputum- Congestive Heart Failure; relief            - Anxiety/Psychological
         after coughing up thick sputum- COPD                       - Deconditioning
   2.    Examination: Usually obvious evidence of cardiac
         or pulmonary disease. Findings may be absent at     CYANOSIS
         rest when symptoms are present only at exertion.
   3.    Pulmonary function tests: Pulmonary disease
                                                                   Bluish color of skin/mucous membranes due to
         rarely causes dyspnea unless tests of obstructive
                                                                    increased amount of reduced hemoglobin
         disease (FEV1, FEV1/FVC) or restrictive disease
         (total lung capacity) are reduced (<80%                   Detected when O saturation is:
         predicted).                                                    o <85% - white-skinned
   4.    Ventricular performance: LV ejection fraction at               o <75% -dark-skinned
         rest and/or during exercise usually depressed in          Reduced Hb > 50 g/L (5 g/dL) – it is the absolute
         cardiac dyspnea.                                           rather than the relative quantity of reduced hb
                                                                    which is important in producing cyanosis
Causes of ACUTE Dyspnea:
   • Anxiety/Hyperventilation                                      Usually most marked in the lips nail beds, ears
   • Asthma                                                         and malar eminences
   • Chest trauma                                                  Degree of cyanosis is modified by the quality of
           • Pneumothorax                                           cutaneous pigment, thickness of the skin, state of
           • Fractured Ribs                                         the cutaneous capillaries.
   • Pulmonary Edema
   • Pulmonary Embolism                                      Causes of cyanosis
   • Spontaneous Pneumothorax                                   A. Central Cyanosis
                                                                         o arterial disaturation or abnormal Hb
Causes of CHRONIC Dyspnea:
    RESPIRATORY                                                         o mucous/skin both affected
       Airway Disease                                           B. Peripheral Cyanosis
       - Upper Airway Obstruction                                        o slow blood flow with greater O2
       - Asthma                                                             extraction
       - Chronic Bronchitis                                              o results from vasoconstriction and
       - Emphysema                                                          diminished peripheral blood
       - Cystic Fibrosis                                                    flow/disease.
       Parenchymal Lung Disease
       - Interstitial Lung Disease
       - Malignancy                                          CENTRAL CYANOSIS
       - Primary                                                A. Decreased pO2
       - Metastatic                                                i.  Decreased atmospheric pressure (high altitude)
       - Pneumonia                                                ii.  Pulmonary disease – common cause of
       Pulmonary Vascular Disease                                      central cyanosis
       - A-V Malformation                                                  a. Alveolar hypoventilation
       - Intravascular Obstruction
                                                                           b. V/Q mismatch diffusion impairment
       - Vasculitis
       - Veno-occlusive disease                                            c. Impaired O2 diffusion
       Pleural Disease                                           iii.   Anatomic Shunts
       - Effusion                                                          a. Congenital Heart Disease
       - Fibrosis                                                          b. Pulmonary A-V fistulas
       - Malignancy
                                                                                    congenital/acquired;
       Chest Wall Disease
       - Deformities (e.g. Kyphoscoliosis)                                          solitary/multiple;
       - Abdominal “Loading”(ascites, pregnancy,                                    microscopic/massive
           obesity)                                                        c. Multiple small intrapulmonary shunts
       Respiratory Muscle Disease                                       most common congenital cardiac lesion
       - Neuromuscular Disorder (Myasthenia Gravis,                        associated with cyanosis in the adult is
           Polio)                                                          the combination of ventricular septal
       - Phrenic Nerve Dysfunction                                         defect and pulmonary outflow tract
       - Weakness                                                          obstruction
                                                                                                          6 of 8 |Page
                more severe the obstruction, greater the      Problem Acute
                 degree of R-L shunting                                            Cough and sputum            symptoms and
     iv.     Hb with low O2 affinity                                              Dry cough
   B. Hemoglobin Abnormalities                                                    (without sputum),        Acute, fairly minor
                                                                                  may become               illness with
             a. Methemoglobinemia - hereditary, acquired    Laryngitis            productive of            hoarseness.
             b. Sulfhemoglobinemia - acquired                                     variable amounts         Often assoc. With
                                                                                  of sputum                viral nasopharyngitis
             c. Carboxihemoglobinemia - not true cyanosis
PERIPHERAL CYANOSIS                                                                                        Acute, often viral
                                                                                  Dry cough,
    Common etiology: vasoconstriction and                  Tracheobronchitis     may become
                                                                                                           illness with burning
         decreased peripheral blood flow (cold exposure,                                                   retrosternal
         shock, CHF, peripheral vascular disease)
                                                                                  Dry hacking cough,       Acute, febrile illness,
    Mucous membranes (oral cavity and beneath              Mycoplasma and        often becoming           often with malaise,
         tongue) are spared                                 viral pneumonia       productive of            headache, and
                                                                                  mucoid sputum            possibly dyspnea
   1. Decreased cardiac output                                                    Pneumococcal:
   2. Cold exposure                                                               sputum mucoid            Pneumococcal:
   3. Blood flow redistribution from extremities                                  or purulent;             Acute illness with
                                                                                  may be blood-            chills, high fever,
   4. Arterial obstruction                                                        streaked,                dyspnea and chest
   5. Venous obstruction                                    Bacterial pneumonia   diffusely pinkish, or    pain; Often preceded
                                                                                  rusty                    by acute URTI
                                                                                  Klebsiella: similar;     Klebsiella: occurs in
APPROACH TO PATIENTS WITH CYANOSIS                                                or sticky red, and       older alcoholic men,
                                                                                  jellylike                typically
       duration (congenital heart disease)                                                              Repeated attempts to
       exposure to drugs/chemicals                                                                         clear the throat.
   2. DIFFERENTIATE CENTRAL VS PERIPHERAL                                                                 Postnasal discharge
      CYANOSIS                                                                    Chronic cough; sputum    may be sensed by
                                                            Postnasal drip              mucoid or          patient or seen in
       Use of lab tests, chest x-ray (heart and lung                                 mucopurulent        posterior pharynx.
          diseases)                                                                                         Associated with
       Response of extremities to warming                                                              chronic rhinitis, with or
   3. PRESENCE OR ABSENCE OF CLUBBING OF                                                                   without sinusitis
      FINGERS (bulbous soft tissues enlargement)                                                             Often long-standing
                                                                                                              cigarette smoking.
       (+)  may indicate heart and/or lung                                      Chronic cough; sputum
          disease; chronic                                                         mucoid to purulent,
                                                            Chronic Bronchitis                                  superimposed
       (+)  not found in peripheral and acute                                   maybe blood-streaked
                                                                                                            infections. Wheezing
          central type of cyanosis                                                   or even bloody
                                                                                                              and dyspnea may
          o Clubbing w/o cyanosis – ineffective                                                                    develop
              endocarditis, ulcerative colitis                                    Chronic cough; sputum
          o Slight cyanosis – lips, cheeks – (-)clubbing                              purulent, often
              of fingers – common in px with mitral                                 copious and foul-
                                                            Bronchiectasis                                   infections common;
              stenosis                                                               smelling; may be
                                                                                                            sinusitis may coexist.
                                                                                    blood-streaked or
          o Combination of clubbing and cyanosis –                                        bloody
              congenital cardiac disease, pulmonary
                                                                                   Cough dry or sputum       Early, no symptoms.
                                                                                     that is mucoid or     Later, anorexia, weight
          o Peripheral cyanosis is not associated with      Pulmonary
                                                                                    purulent; may be       loss, fatigue, fever, and
              clubbed fingers                               Tuberculosis
                                                                                    blood streaked or            night sweats
   4. ABG’s DETERMINATION                                                                  bloody
          o spectroscopic and other examinations for                              Sputum purulent and       A febrile illness. Often
              abnormal hemoglobin                           Lung abscess
                                                                                  foul-smelling; may be      poor dental hygiene
                                                                                         bloody             and a prior episode of
                                                                                                           impaired consciousness
                                                                                    Cough, with thick
                                                                                                           Episodic wheezing and
                                                                                    mucoid sputum,
                                                                                                            dyspnea, but cough
                                                            Asthma                especially near end of
                                                                                                           may occur alone. Often
                                                                                        an attack
                                                                                                            a history of allergy

                                                                                                                  7 of 8 |Page
      Problem              Cough and sputum            symptoms and                                      Clinical Questions
                                                                                  1. A 16 Y/O female complains of difficulty of breathing
                               Cough dry to             Usually a long
Neoplasm                   productive; sputum        history of cigarette         after an argument with her mother. She was previously
Cancer of the Lung           may be blood-          smoking. Associated           well, active member of the volleyball team. She describes
                           streaked or bloody        manifesta tions are          a heavy compressive pain at the center of the chest. PE is
                                                                                  unremarkable, with occasional sighing breaths. The most
                                 Often dry,                                       likely condition to explain her symptoms is:
Cardiovascular                 especially on
Disorders                  exertion or at night;
Left Ventricular           may progress to the                                    A. angina                  C. asthma
Failure or Mitral           pink frothy sputum                                    B. anxiety                 D. pulmonary embolism
                                                     nocturnal dyspnea
Stenosis                   of pulmonary edema
                                or to frank
                                hemoptysis                                        2. A 60 y/o, heavy smoker male complains of progressive
                           Dry to produc tive;        Dyspnea, anxiety,           difficulty of breathing of 4 months duration associated
Pulmo Emboli
                           may be dark, bright        chest pain, fever;          with occasional dry cough. There is no chest pain nor
                           red, or mixed with        factors that predis          fever. The chest is resonant with distant breath sounds
                                  blood             pose to deep venous
                                                                                  and occasional rhonchi /wheezing. He most likely has:
                                                         Exposure to
                           Variable. There may                                    A. chronic bronchitis               C. asthma
Irritating Particles,                               irritants. Eyes, nose,
                            be a latent period
Chemicals, or Gases                                  and throat may be            B. emphysema                        D. coronary disease
                           between exposure
                             and symptoms
                                                                                  3. A 65 y/o, ex- heavy smoker is seen at the ER because of
                                                    Wheezing, especially
                                                       at night (often            difficulty of breathing of 2 months duration associated
                                                        mistaken for              with cough and recent onset of bloody sputum. There is a
                              Chronic cough,           asthma), early             20-lbs weight loss in the past 6 months but denies fever.
Gastroesophageal           especially at night or   morning hoarseness,
                                                                                  On examination, there is a persistent rhonchi over the
reflux                     early in the morning         and repeated
                                                    attempts to clear the
                                                                                  right-mid lung. The condition that needs to be strongly
                                                       throat. Often a            considered is:
                                                    history of heartburn
                                                      and regurgitation
                                                                                  A. chronic bronchitis               C. asthma
                                                                                  B. lung cancer                      D. tuberculosis


                                        History                                                 ABG
                                  Physical Examination                                          CBC

                                                                                                              Exclude Anemia

                                                                      Chest X ray

                    Inapparent Pulmonary
                      Disease or possible                                                      Obvious Pulmonary Dx
                         Heart disease

                                                                                                                  Exclude Infx, Neoplasm

                                                                             Pulmonary Function Test
                                                                                Diffusing Capacity
                        Work Up
                        Cardial Dx                                                                                                 8 of 8 |Page

To top