Acute Respiratory Failure Mechanical Ventilation Aula

Acute Respiratory Failure Mechanical Ventilation

Acute Respiratory Failure • Characterized by – PaO2 < 60 – O2 Sat < 90 – PaCO2 > 50 – pH < 7.30

Types of Failure • Ventilatory Failure • Oxygenation Failure • Combined Ventilatory/Oxygenation Failure

Ventilatory Failure • V/Q • Adequate Perfusion • Inadequate ventilation – Insufficient air movement ↓ O2 to alveoli – CO2 retention

• Caused by – Mechanical abnormality of lungs or chest wall – Defect in respiratory control center – Impaired function of respiratory muscles

Oxygenation Failure • Adequate ventilation • Decreased perfusion • Inadequate oxygenation of pulmonary blood • Caused by – Pulmonary Embolism – Inadequate hemoglobin

Combined Ventilatory/Oxygenation Failure • • • •

Hypoventilation Inadequate gas exchange Occurs in clients with abnormal lungs Cardiac failure – Cannot compensate for ↓ O2

Assessment • Signs of Hypoxemia • Decreased PO2 – – – – – – – –

Dyspnea, tachypnea Cyanosis Restlessness Apprehension Confusion Tachycardia Dysrhythmias Metabolic acidosis

• Signs of Hypercapnia • Increased PCO2 – Dyspnea → resp. depression – Headache – Tachycardia – Coma – Systemic vasodialation – Heart failure – Respiratory acidosis

Interventions • Correct underlying cause • Support ventilation ∀ ↑ PO2 and ↓PCO2 – O2 therapy – Positioning ↓ anxiety – Energy conservation – Bronchodialators

Mechanical Ventilation • Unresponsive to interventions • Hypoxemia • Progressive alveolar hypoventilation with respiratory acidosis • Respiratory support after surgery

Endotracheal Intubation • Short term (10-14 days) • Maintain patent airway ∀ ↓ work of breathing • Remove secretions • Provide ventilation & O2

Types of Ventilators • Negative Pressure (Mimic spontaneous breaths) – Iron Lung

• Positive Pressure (Push air into lungs) – Pressure cycled • Air delivered until preset pressure reached – Time cycled (Pediatrics/Neonates) • Push air in with preset time • Tidal volume & pressure variable – Volume cycled • Push air in until preset volume reached • Constant tidal volume • Variable pressure

Modes of ventilation • Controlled ventilation • Assist-control (A/C) • Synchronized Intermittent Mandatory Ventilation (SIMV)

Controlled ventilation • Least used • All breaths delivered at preset tidal volume, pressure & rate • Client with no spontaneous effort – Severe ICP – Brain death – Voluntary paralysis of muscles

Assist-Control Ventilation • Most commonly used • Tidal volume & rate preset • Client does not trigger breath, ventilator will deliver breath • Advantage- client controls rate of breathing • Disadvantage - ↑ respiratory rate → hyperventilation → respiratory alkalosis

SIMV • Similar to A/C ventilation • Spontaneous breathing between ventilator breaths at clients own rate & tidal volume • Used as primary ventilator mode or weaning mode

Ventilator Settings • Tidal Volume (VT) – Volume of air delivered each breath – 7-10 cc/kg body wt. • 75 kg = 750 cc

• Rate – # of breath/minute – 10-14 BPM

• Fraction of inspired O2 (FIO2) – Oxygen concentration – 21% (room air) to 100%

Ventilator Settings • Peak Airway (Inspiratory) Pressure (PIP) – Pressure needed to deliver set tidal volume – Highest pressure indicated during inspiration ↑ airway resistance • Bronchospasms ∀ ↑ secretions • Pulmonary edema ∀ ↓ pulmonary compliance – Prevents barotrauma • Lung damage from excessive pressure

Ventilatory Settings • Continuous Positive Airway Pressure (CPAP) – Spontaneous respirations – Intubation or tight fitting mask – Positive pressure during the entire respiratory cycle (5-15 cm H2O) – Keeps alveoli open during inspiration – Prevents alveoli collapse during expiration – Improves gas exchange & oxygenation – Used during weaning – Nasal CPAP, BIPAP

Ventilatory Settings • Positive End-Expiratory Pressure (PEEP) – Must be intubated – Positive pressure exerted during expiration (+5 to +15 cm H2O) – Keeps alveoli open between breaths – Improves oxygenation – Enhances gas exchange – Treatment for persistent hypoxemia

Ventilatory Settings • Pressure Support Ventilation (PSV) – Client’s inspiratory effort is assisted to a certain level of pressure ↓ work of breathing & ↑ comfort through ↑ control by client – PSV 5-20

Management • Anxiety – Education – Communication – Alarms • Treat client first, then ventilator

Management • Assessment – Client response to treatment – Continuous O2 saturation – Vital signs – Lung Sounds – Ventilator settings & alarms – Management of secretions • Closed suction system

Prevent Complications • Cardiac – Hypotension • Application of positive pressure →↑ intrathoracic pressure → ↓ venous return to heart → ↓ cardiac output • Dehydration • Requires high PIP

– Fluid retention ∀ ↓ cardiac output → stimulation of reninangiotensin-aldosterone response → fluid retention

Prevent Complications

• Lungs – Barotrauma • COPD

• Pneumothorax, subq emphysema – Volutrauma – Acid-base abnormalities • Infection – Within 48 hrs of intubation, bacteria colonization

Prevent Complications • Electrolyte Imbalances – Monitor K+, Ca++, Mg++, phosphate levels – Efficiency of respiratory muscle function

• Muscular – Immobility ↑ muscle tone & strength – Facilitates gas exchange

Prevent Complications • Ventilator Dependence – Respiratory muscle fatigue – Client unable to resume independent breathing

• Extubation – Monitor respiratory effort – Supplemental O2 – Monitor O2 saturation

Weaning from Ventilator • Parameters set for PaO2, O2 Sat, PaCO2 & pH ∀ ↓ FIO2 →↑spontaneous effort by client • Remain on T-piece after ventilator before extubation → aerosol mask • Minimal sedation while weaning • Monitor respiratory effort & rate, vital signs