SPR L15 Pathophysiology of Respiratory Disease and Failure Flashcards Preview

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Pathophysiology of Respiratory Disease and Failure

Learning Outcomes


  • Symptoms/signs respiratory disease
  • Pathophysiology/investigation/management of COPD
  • Pathophysiology/investigation/management of asthma
  • Definition and causes of respiratory failure
  • Pathophysiology of respiratory failure
  • Monitoring of respiratory failure
  • Management of respiratory failure


Respiratory physiology: overview

What is the function of the respiratory system?

Control of systemic arterial blood gases

PaCO2 (+pH) & PaO2

  • Ventilation
  • Gas exchange


Symptoms and signs respiratory disease (1)

  1. What are the S&S of upper respiratory system?
  2. Explain the mechanism of coughing 

  1. Runny nose (rhinorrhoea), Blocked nose, Sneezing 

  2. Mechano and Chemo-R in the Pharynx, Larynx, Trachea, bronchi and diaphragm transmit via the afferent neurones to cough centre in medulla oblongata, then efferent neurones carry signal to expiratory muscles to cough.



Symptoms and signs respiratory disease (2)

  1. Describe mucoid sputum
  2. What is contained in yellow/green sputum?
  3. In what conditions can haemoptysis present?

  1. clear/white
  2. cellular material (eg. infection)
  3. COPD

    Bronchial carcinoma

    Pulmonary oedema (pink and frothy)



Symptoms and signs respiratory disease: dyspnoea (1)

  1. Describe the receptors stimulated by neurogenic factors
  2. Describe the receptors stimulated by chemical stimuli

  1. Pumonary Receptors - sensitive to stretch and bronchial irritation. Stimulated by Asthma, PE, Pneumonia.                                                                 Juxtacapillary Receptors - stimulated by asthma, pulmonary congestion (heart failure)                            Muscle and Joint Receptors - stimulated by exercise.                                                                          Chest Wall Receptors     
  2. Respiratory Centre - Stimulated by increase in PaCOand increase in [H+]                                            Carotid and Aortic Bodies - Stimulated by PaO< 8kPa


Symptoms & signs respiratory disease: dyspnoea (2)

​Explain the following...

  1. Orthopnoea
  2. Tachypnoea
  3. Hypernoea
  4. Hyperventilation

  1. breathless lying down; abdominal pressure   ‘splinting’ diaphragm

  2. increased rate breathing - may be normal

  3. increased ventiliation - may be normal

  4. inappropriate increase in breathing


Symptoms and signs respiratory disease (3)

  1. What is a wheeze typically a feature of?
  2. What is it caused by?
  3. When is it more pronounced?

  1. Typically a feature of airway obstruction
  2. Caused by airway vibration/turbulent airflow
  3. during expiration (due to airway collapse) 


Symptoms and signs respiratory disease (4)

​Give examples of evidence of hypoxaemia?

  • Increased ventilation

  • Central cyanosis

    • greater than 5 g/dL of desaturated Hb

  • increase in Hb (polycythaemia) if chronic

  • Reduced consciousness, confusion


Symptoms and signs respiratory disease (5)

Give examples of evidence of hypercapnia

  • Increased ventilation
  • Flushed skin, bounding pulse (peripheral vasodilatation)
  • Headache (acidosis/cerebral vasodilatation)
  • Coarse tremor outstretched hands
  • Reduced consciousness, confusion


Definition and causes COPD

  1. What is COPD?
  2. What conditions does it include?
  3. List the causes of COPD?

  1. 'Chronic Obstructive Pulmonary Disease' - Disease state characterized by airflow limitation which is not fully reversible

  2. chronic bronchitis and emphysema


  • Climate
  • Air pollution
  • Genetic susceptibility
  • a1-antitrypsin deficiency
  • Infections (exacerbatory)


Pathophysiology of COPD (1)

  1. ​What does Airways Obstruction lead to?
  2. What could be the reasons for airway obstruction in COPD?

  1. increased work of breathing
  2. Chronic inflammation bronchi/bronchioles: Mucosal swelling, Increased mucus secretion/mucus plugging, Obstruction maybe reversible in early stages                                              Fibrosis: thickening airway walls                                Emphysema: destruction of lung tissue distal to terminal bronchiole - loss of elastic tissue exacerbates obstruction, early expiratory closure

(Fibrosis and Emphysema are IRREVERSIBLE)


Pathophysiology of COPD (2)

Apart from airways obstruction, outline pathophysiology of COPD



Outline the variable ventilatory response in COPD

Ventilation/Perfusion (V/Q) Mismatch - overall fall

Increased ventilatory drive - Airway obstruction reduces alveolar ventilation, Favours an INCREASE in  PaCO2 (and a DECREASE in PaO2)


  • Increased ventilatory effort: maintains normal blood gases (‘pink puffers’)
  • Limited increase in ventilatory effort (‘blue bloaters’):
    • decreased PaCO2
    • increased PaO2
    • Hypoxic respiratory drive


What are the consequences of the pathophysiology of COPD?

  • Respiratory failure (Type 2)
    • Cyanosis
    • Signs of hypercapnia
  • Pulmonary vasoconstriction
    • Pulmonary hypertension
    • Right ventricular hypertrophy
    • Right ventricular failure (cor pulmonale)
  • Renal responses
    • Hypoxia promotes EPO production (polycythaemia)
    • Fluid/salt retention promoting oedema and right heart failure (mechanism unclear)


Outline the main investigations that should be carried out in COPD

Lung Function Tests

  • Spirometry
  • PEFR


LFTS : Spirometry

Look at the attached picture, what do each of the numbers represent?

  1. Total Lung Capacity
  2. Inspiratory Reserve Volume
  3. Tidal Volume
  4. Functional Residual Capacity
  5. Vital Capacity
  6. Residual Volume


Investigations : COPD


What would the following results show?

  1. FEV1: FVC ratio?
  2. PEFR?
  3. FRC?
  4. TLC?
  5. Compliance?
  6. TCO?
  7. Explain 4 5 & 6


  1. decreased (<75%)
  2. decreased
  3. increased - air trapping
  4. increased
  5. increased
  6. decreased 
  7. emphysema, decreased elastic recoil, decreased alveolar surface area



Investigations : COPD

Chest XRay

  1. What features would be present?


  1. Describe the RCC
  2. Describe what would be seen in acuteinfection

  1. Overinflated chest (dark lung fields) and Flattened diaphragm


  1. increased, increased Hb
  2. increased WCC


COPD Management

Outline the steps that should be taken


  • Stop smoking
  • Drug therapy
    • Bronchodilators
    • b2-adrenoceptor agonist
    • Cholinergic (antimuscarinic) antagonists
    • Corticosteroids
    • Mucolytic agents
    • Antibiotics for infections
    • Diuretics for oedema
  • O2 therapy
    • During acute exacerbations (type II respiratory failure below)
    • Long term domiciliary O2
    • Risk of respiratory depression (start with 24% O2)



  1. What is it?
  2. What is Extrinsic Asthma?
  3. What is Intrinsic Asthma?
  4. Describe the airway hyperresponsiveness

  1. Reversible airways obstruction and airway hyperresponsiveness

  2. Atopic individuals - Identifiable allergens (skin prick)

  3. No obvious external allergens

  4. Bronchial inflammation

    Mucus impaction

    Altered smooth muscle function - SM hyperplasia and increased contractility


Clinical Features of Asthma

  1. What are the signs and symptoms?
  2. What do lung function tests show?
  3. What does the skin prick test achieve?

  1. Episodic dyspnoea with wheeze, Worse at night, Cough

  2. decreased PEFR (>15% reversible with bronchodilators)

    Spirometry:  decreased FEV1 (>15% reversible with bronchodilators)

    Normal TCO

  3. Identification of allergens


Generally outline the management of Asthma 


  • Remove extrinsic causes
  • Drug therapy
    • Inhaled bronchodilators
      • Inhaled b2-adrenoceptor agonist
      • Inhaled cholinergic (antimuscarinic) antagonists
    • Inhaled anti-inflammatory agents
      • Sodium cromoglycate
      • Corticosteriods
    • Oral corticosteroids and steroid sparing agents


Outline the management of acute severe asthma

  1. What are the signs and symptoms?
  2. What steps should be carried out 


  1. Cannot complete a sentence

    RR >25 /min

    PR >110 bpm

    PEFR < 50% predicted

  2. Check blood gases

    O2 therapy (40-60%)

    Nebulised bronchodilator

    IV hydrocortisone

    Oral corticosteroids commenced

    Chest X-ray to exclude pneumothorax

    Monitor response (blood gases)


Definition and types of respiratory failure

  1. Give a definition 
  2. Outline Type 1
    1. Outline Type 2

  1. Hypoxaemia/hypercapnia (hypercarbia); normal inspirate. Working definition:

    PaO< 8 kPa (60 mmHg)

    PaCO2 > 7 kPa (55 mmHg)


    Type I: PaO2 low; PaCO2 normal/low

    Type II: PaO2 low; PaCO2 high


Type 1 Respiratory Failure

  1. What is Type 1 RF characterised by?
  2. Give examples of T1RF
  3. Outline the Pathophysiology?


  1. decreased PaO2: normal or decreased PaCO2
  2. Acute lung damage, eg pneumonia, pulmonary oedema

    Acute severe asthmatic attack

    Vascular abnormalities, eg R to L shunt, pulmonary embolus

    Chronic interstitial lung disease (eg fibrosis)


    Ventilation/perfusion (V/Q) mismatch                   Over-ventilated regions compensate PaCO2 but not PaO2




Type 1 Respiratory Failure

  1. Over-ventilated regions compensate for what?
  2. What don't they compensate for?

  1. PaCO2
  2. PaO2


Type II respiratory failure

  1. What is it characterised by?
  2. Give examples of conditions
  3. What is the overall pathophysiology?

  1. decreased PaO2: increased PaCO2
  2. Chronic obstructive pulmonary disease

    Late stages of a severe asthmatic attack

    Restrictive ventilatory defects

    Chest wall deformities

    Weakness of respiratory muscles

    Central respiratory depression

  3. Inadequate total ventilation relative to CO2 production


Monitoring respiratory failure

  1. What are the key clinical indicators of severity of respiratory failure?
  2. What assessments should be carried out?

  1. Tachypnoea

    Use of accessory muscles of respiration

    Inability to speak

    Agitation/restlessness/diminished consciousness

  2. Arterial Blood gas analysis - Abnormal blood gases, Acid-base disturbance                                                      Pulse oximetry - Differential light absorption oxyHb v. deoxyHb, Arterial O2 saturation (SpO2): finger/earlobe, 95-100%, Requires adequate pulsatile flow                                                                    Capnography -  Breath-by-breath; expired CO2 conc., End tidal CO2 normally approximates PaCO2, Allows assessment of successful, endotracheal intubation, Wave-form shape can indicate lower airway obstruction (longer, slower expiratory phase)


Managing Respiratory Failure

Outline the management of RF

  • O2 therapy
    • With COPD and chronically elevated PaCO2: 24 – 28% O2
    • Otherwise 35-55%O2 at 6-10 L/min
  • Treat airways obstruction

    • Physiotherapy 

    • Aspirate Airway

  • Control secretions

  • Treat pulmonary oedema

  • Treat pulmonary infections

  • Respiratory support

    • Mechanical ventilation: invasive/non-invasive

    • Respiratory stimulants

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