Acute Respiratory FailureMechanical 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 renin-

angiotensin-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