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Acute Respiratory Obstruction and Restriction. ICU nurses course 2004 Tim Smith. Topics. Asthma (acute bronchospasm) Acute Exacerbation of COPD Pneumothorax Pleural Effusion. Acute Asthma. Asthma. Chronic inflammatory condition of the lung airways characterised by:

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Acute respiratory obstruction and restriction

Acute Respiratory Obstruction and Restriction

ICU nurses course 2004

Tim Smith


Topics
Topics

  • Asthma (acute bronchospasm)

  • Acute Exacerbation of COPD

  • Pneumothorax

  • Pleural Effusion



Asthma
Asthma

Chronic inflammatory condition of the lung airways characterised by:

  • Reversible airflow limitation

  • Airway hyperresponsiveness

  • Bronchial inflammation

  • Increasing prevalence

  • 10-15% of pop. In 2nd decade


  • Pathogenesis
    Pathogenesis

    • Extrinsic vs. Intrinsic

    • Mast cells (histamine, LTC4, PGD2)

    • T cells (cytokines)

    • Eosinophils (ECP, MBP)

    • C-fibres (NKA, CGRP, SubP)


    Precipitating factors
    Precipitating Factors

    • Allergens

      • Flour

      • Washing powder

      • Animals

    • Non-specific

      • Exercise

      • Cold air

      • Emotion

    • Occupational

      • Isocyanates

      • Colophony fumes


    Mechanisms
    Mechanisms

    • Bronchoconstriction

    • Airway inflammation

      • Microvascular leak

      • Oedema

    • Increased (viscid) mucus production

      AIRWAY OBSTRUCTION


    Physiological effects
    Physiological Effects

    • Increased work of breathing

      • Accessory muscle use

      • Increased oxygen demands

    • Air trapping

      • Prolonged active expiratory phase

      • Auto-PEEP

    • V/Q mismatch

      • Hypoxia

    • Increased respiratory drive


    Clinical features 1
    Clinical Features 1

    Related to severity:

    • Moderate asthma exacerbation

      • Breathlessness

      • Wheeze (expiratory)

      • PEF 50-75%


    Clinical features 2
    Clinical Features 2

    • Acute Severe Asthma

      One of:

      • PEF 33-50%

      • RR >= 25 /min

      • HR >= 110/min

      • Inability to complete sentences


    Clinical features 3

    One of:

    PEF <33%

    SpO2 <92%

    PaO2 <8kPa

    Normal PaCO2

    Silent chest

    Cyanosis

    Feeble respiratory effort

    Bradycardia

    Dysrhythmia

    Hypotension

    Exhaustion

    Confusion

    Coma

    Clinical Features 3

    • Life threatening Asthma


    Clinical features 4
    Clinical Features 4

    • Near Fatal Asthma

      One of:

      • High PaCO2

      • Mechanical ventilation


    Chest x ray
    Chest X Ray

    • Hyperinflation

    • Flattened diaphragm




    Mri with he 3
    MRI with He3

    Before

    40 min after Albuterol


    Medical therapy
    Medical Therapy

    • Oxygen

    • β2-agonists

      • Nebulised if possible

    • Steroids

    • Ipratropium Bromide

    • Magnesium Sulphate

      • Life threatening or poor response

    • Aminophylline

      • Perhaps in some patients


    Indications for itu
    Indications for ITU

    • Deteriorating PEF

    • Worsening hypoxia

    • Hypercapnia

    • Worsening acidosis

    • Altered conciousness

    • Exhaustion

    • Respiratory arrest


    Itu treatment
    ITU treatment

    • Continue full medical treatment

    • NIV

      • Perhaps

    • IPPV

      • For worsening hypoxia/hypercapnia

      • Exhaustion

      • Reduced concious level

    • Optimise

      • Fluid status

      • Hypokalaemia (steroids, β2-agonists)


    Ventilation
    Ventilation

    • Conventionally volume controlled

    • Slow rate

    • Long expiratory time

    • Low/no PEEP

      eg. MV 115 ml/kg, TV 6-8 ml/kg, RR 8-10, PEEP 0

    • FiO2 to keep SpO2 >=94%

    • Remember: hypotension, pneumothorax, EMD



    Acute exacerbation of copd1
    Acute Exacerbation of COPD

    • COPD affects 5% of adult population

    • Fifth most common cause of death world wide.

    • Chronic irreversible disease

    • Acute deterioration can be precipitated by diverse causes


    Pathologic processes
    Pathologic Processes

    • Bronchiolitis (inflam. airway narrowing)

    • Loss of connective tissue tethering

    • Loss of alveoli and capillaries

    • Increased closing volume

    • Increased pulmonary vascular resistance

    • Resulting in:

      • V/Q mismatch

      • Increased resistance

      • Dynamic hyperinflation

      • Increased work of breathing


    Causes of exacerbations
    Causes of Exacerbations

    • Infection (50%)

    • Heart Failure (25%)

    • Sputum Retention

    • PE

    • Pneumothorax

    • Sedation

    • Medication

    • Malnutrition


    Treatment
    Treatment

    Treat underlying cause and support:

    • Oxygen (titrate avoiding carbonarcosis)

    • Bronchodilators

    • Steroids (not if pneumonic cause)

    • Antibiotics for infectious cause

    • Clearance of secretions

      • Physio, mucolytics, suctioning, bronchoscopy

    • Hydration, Diuretics, Vasodilators

    • DVT prophylaxis

    • Nutrition

    • no benefit from respiratory stimulants


    Non invasive ventilation 1
    Non-invasive Ventilation 1

    • Ventilatory support via nasal/facemask

    • Aims:

      • Unload respiratory muscles

      • Augment ventilation

      • Improve oxygenation

      • Reduce CO2


    Non invasive ventilation 2
    Non-invasive Ventilation 2

    Indicated for:

    Worsening COPD with:

    • Acute dyspnoea

    • RR >28/min

    • PaCO2 > 6kPa and pH < 7.35

      in spite of maximal medical therapy and not related to XS O2


    Invasive ventilation 1
    Invasive Ventilation 1

    • Indications:

      • Exhaustion despite NIV

      • Deteriorating concious level

      • Hypoxia

      • Failure of secretion clearance

      • Respiratory arrest

    • Need for mechanical ventilation dramatically decreases survival.

    • Weaning often difficult.


    Invasive ventilation 2
    Invasive Ventilation 2

    • Strategy:

      • Low RR

      • Low TV

      • Prolonged expiration

    • Pitfalls:

      • Dynamic hyperinflation

      • Barotrauma

      • Prolonged difficult wean


    Invasive ventilation 3
    Invasive Ventilation 3

    • Outcome:

      • ITU mortality 10-30%

      • 1 year survival 50%

      • Depends more on previous state, nutrition, age than on measured variables.


    Pneumothorax
    Pneumothorax

    Pathological collection of extraalveolar air in the pleural space.


    Causes
    Causes

    • Spontaneous:

      • Primary – no underlying lung disease

      • Secondary – COPD/CF/AIDS/Ca/chemo

    • Traumatic:

      • blunt or penetrating chest trauma

      • iatrogenic – central lines/surgery

    • Barotrauma:

      • positive pressure ventilation (4-15%)

      • ARDS & IPPV (up to 60%)

      • (COPD/asthma)


    Clinical features 11
    Clinical Features 1

    • Decreased or absent breath sounds

    • Hyperresonant percussion

    • Chest pain

    • Dyspnoea (worse if secondary)

    • Tachycardia

    • Pleural line & lucent space on CXR

    • Hypoxaemia (if large)




    Clinical features 21
    Clinical Features 2

    • Pneumothorax may be difficult to detect in ventilated patient with poorly compliant lungs:

      • Stiff lungs do not collapse readily

      • Gas exchange often already disordered

      • Subtle early signs:

        • Decreased urine output

        • Increased CVP

        • Tachycardia

        • Decreased CI

      • High index of suspicion

      • CT scanning may be useful


    Tension pneumothorax
    Tension Pneumothorax

    • One way valve effect

    • Intrapleural gas accumulates

    • Displacement of mediastinum

    • Compression of contralateral lung

    • Hypoxaemia due to shunt

    • Decreased VR and CO

    • Hypotension and EMD arrest



    Treatment 1
    Treatment 1

    • Spontaneously breathing patient

      • Small pneumothorax (<20%) if asymptomatic can be treated conservatively.

      • Larger pneumothorax must be aspirated or drained.

      • Recurrence requires pleurodesis


    Treatment 2
    Treatment 2

    • Ventilated patient:

      • Low threshold for draining pneumothoraces as risk of tension

      • Place chest drain in patient with pneumothorax requiring ventilation


    Treatment 3
    Treatment 3

    • Tension pneumothorax:

      • Potentially rapidly fatal

      • Rapid decompression based on clinical diagnosis improves survival

      • Don’t wait for the X-ray


    Pleural effusion
    Pleural Effusion

    • Pathological collection of fluid within the pleural space.

    • Starling Forces normally keep pleural space dry.

    • Effusion results from:

      • Increased pulmonary capillary pressure

      • Increased capillary permeability

      • Hypoalbuminaemia

      • Lymphatic obstruction


    Clinical features
    Clinical Features

    • Pleuritic pain

    • Cough

    • Dyspnoea.

    • Decreased air entry

    • “stony” dullness

    • Restrictive defect


    Radiology
    Radiology

    • CXR (upright PA)

      • >300ml loss of costophrenic angle

      • Larger effusions cause opacification

    • Lateral decubitus films

      • more sensitive (5ml)

      • Impractical on ITU

    • USS

      • Extremely sensitive (2ml)

      • Can be used to guide drainage


    Thoracocentesis
    Thoracocentesis

    May help determine cause:

    • Transudate vs. Exudate

      • (prot >3g/dl, sg >1.016)

      • Imbalance in Starling Forces vs increased pleural membrane permeability

    • Low glucose suggests infection/rheumatoid

    • High amylase suggests pancreatitis

    • WCC>10mm-3 suggests infection

    • Gram stain and culture may ID pneumonic cause

    • pH <7.1 = empyema


    Treatment1
    Treatment

    • Treatment of underlying condition where appropriate

    • Drainage if:

      • Empyema

      • Ventilatory compromise

      • h/o trauma (suspect haemothorax)

    • Pleurodesis

    • VATS/Thoracotomy

    • Pleuroperitoneal shunts


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