Acute Respiratory Failure

Respiratory System Consists of two parts: Gas exchange organ (lung): responsible for OXYGENATION Pump (respiratory muscles and respiratory control mechanism): responsible for VENTILATION NB: Alteration in function of gas exchange unit (oxygenation) OR of the pump mechanism (ventilation) can result in respiratory failure

Normal Lung

Lung Anatomy

Normal Alveoli

Gas Exchange Unit Fig. 66-1

Normal ABGs pH = 7.35-7.45 CO2 = 35-45 HCO3= 23-27

Respiratory and Metabolic Acidosis and Alkalosis CO2 is an acid and is controlled by the Respiratory (Lung) system HCO3 is an alkali and is controlled by the Metabolic (Renal) system Respiratory response is immediate; Metabolic response can take up to 72 hours to respond (except in patients with COPD who are in a constant state of Compensation!)

ABG Interpretation Step 1: Check the pH: Is it acidotic or alkalotic or normal? pH below 7.35 is acidotic; pH above 7.45 is alkalotic If pH is normal, then the ABG is compensated; if pH not normal, then the ABG is uncompensated

ABG Interpretation (cont’d) Step 2. Check the CO2 and HCO3: If the CO2 (acid) is above 45, the pt is acidotic; if the CO2 is below 35, the pt is alkalotic If the HCO3 is above 27, the patient is alkalotic; if the HCO3 is below 23, the patient is acidotic

ABG Interpretation (cont’d) Step 3 If the CO2 is high (above 45), then the patient is in Respiratory Acidosis; if the CO2 is low (below 35), then the patients is in Respiratory Alkalosis. If the HCO3 is high (above 27), then the patient is in Metabolic Alkalosis; if the HCO3 is low (below 23), then the patient is in Metabolic Acidosis.

ABG Example #1 pH = 7.36 CO2 = 41 HCO3 = 27 Diagnosis: ?

ABG Example #2 pH = 7.49 CO2 = 37 HCO3 = 32 Diagnosis: ?

ABG Example #3 pH = 7.29 CO2 = 50 HCO3 = 26 Diagnosis: ?

ABG Example #4 pH = 7.40 CO2 = 32 HCO3 = 30 Diagnosis: ?

Acute Respiratory Failure Results from inadequate gas exchange Insufficient O2 transferred to the blood Hypoxemia Inadequate CO2 removal Hypercapnia

Acute Respiratory Failure with Diffuse Bilateral Infiltrates

Acute Respiratory Failure Not a disease but a condition Result of one or more diseases involving the lungs or other body systems NB: Acute Respiratory Failure: when oxygenation and/or ventilation is inadequate to meet the body’s needs

Acute Respiratory Failure Classification: Hypoxemic respiratory failure (Failure of oxygenation) Hypercapnic respiratory failure (Failure of ventilation)

Classification of Respiratory Failure Fig. 66-2

Acute Respiratory Failure Hypoxemic Respiratory Failure PaO2 of 60 mm Hg or less (Normal = 80 - 100 mm Hg) Inspired O2 concentration of 60% or greater

Acute Respiratory Failure Hypercapnic Respiratory Failure PaCO2 above normal (>45 mm Hg) Acidemia (pH <7.35)

Hypoxemic Respiratory Failure Etiology and Pathophysiology Causes: Ventilation-perfusion (V/Q) mismatch Shunt Diffusion limitation Alveolar hypoventilation

V-Q Mismatching I) V/Q mismatch Normal ventilation of alveoli is comparable to amount of perfusion Normal V/Q ratio is 0.8 (more perfusion than ventilation) Mismatch d/t: Inadequate ventilation Poor perfusion

Range of V/Q Relationships Fig. 66-4

Hypoxemic Respiratory Failure Etiology and Pathophysiology Causes V/Q mismatch COPD Pneumonia Asthma Atelectasis Pulmonary embolus

Hypoxemic Respiratory Failure Etiology and Pathophysiology II) Shunt An extreme V/Q mismatch Blood passes through parts of respiratory system that receives no ventilation d/t obstruction OR fluid accumulation Not Correctable with 100% O2

Diffusion Limitations III) Diffusion Limitations Distance between alveoli and pulmonary capillary is one- two cells thick With diffusion abnormalities: there is an increased distance between alveoli (may be d/t fluid) Correctable with 100% O2

Hypoxemic Respiratory Failure Etiology and Pathophysiology Causes Diffusion limitations Severe emphysema Recurrent pulmonary emboli Pulmonary fibrosis Hypoxemia present during exercise

Diffusion Limitation Fig. 66-5

Alveolar Hypoventilation IV) Alveolar Hypoventilation Is a generalized decrease in ventilation of lungs and resultant buildup of CO2

Hypoxemic Respiratory Failure Etiology and Pathophysiology Causes Alveolar hypoventilation Restrictive lung disease CNS disease Chest wall dysfunction Neuromuscular disease

Hypoxemic Respiratory Failure Etiology and Pathophysiology Interrelationship of mechanisms Hypoxemic respiratory failure is frequently caused by a combination of two or more of these four mechanisms Effects of hypoxemia Build up of lactic acid → metabolic acidosis → cell death CNS depression Heart tries to compensate → ↑ HR and CO If no compensation: ↓ O2, ↑ acid, heart fails, shock, multi-system organ failure

Hypercapnic Respiratory Failure Etiology and Pathophysiology Imbalance between ventilatory supply and demand Occurs when CO2 is increased

Causes Hypercapnic Respiratory Failure I) Alveolar Hypoventilation and VQ Mismatch: Ventilation not adequate to eliminate CO2 Leads to respiratory acidosis Eg. Narcotic OD; Guillian-Barre, ALS, COPD, asthma

Causes Hypercapnic Respiratory Failure II) VQ Mismatch: - Leads to increased work of breathing - Insufficient energy to overcome resistance; ventilation falls; ↑PCO2; respiratory acidosis

Hypercapnic Respiratory Failure Categories of Causative Conditions I) Airways and alveoli Asthma Emphysema Chronic bronchitis Cystic fibrosis

Hypercapnic Respiratory Failure Categories of Causative Conditions II) Central nervous system Drug overdose Brainstem infarction Spinal cord injuries

Hypercapnic Respiratory Failure Categories of Causative Conditions III) Chest wall Flail chest Fractures Mechanical restriction Muscle spasm

Hypercapnic Respiratory Failure Categories of Causative Conditions IV) Neuromuscular conditions Muscular dystrophy Multiple sclerosis

Respiratory Failure Tissue Oxygen Needs Major threat is the inability of the lungs to meet the oxygen demands of the tissues

Respiratory Failure Clinical Manifestations Sudden or gradual onset A sudden  in PaO2 or rapid  in PaCO2 is a serious condition

Respiratory Failure Clinical Manifestations When compensatory mechanisms fail, respiratory failure occurs Signs may be specific or nonspecific

Respiratory Failure Clinical Manifestations Severe morning headache Cyanosis Late sign Tachycardia and mild hypertension Early signs

Respiratory Failure Clinical Manifestations Consequences of hypoxemia and hypoxia Metabolic acidosis and cell death  Cardiac output Impaired renal function

Respiratory Failure Clinical Manifestations Specific clinical manifestations Rapid, shallow breathing pattern Sitting upright Dyspnea

Respiratory Failure Clinical Manifestations Specific clinical manifestations Pursed-lip breathing Retractions Change in Inspiratory:Expiratory ratio

Respiratory Failure Diagnostic Studies Physical assessment ABG analysis Chest x-ray CBC ECG

Respiratory Failure Diagnostic Studies Serum electrolytes Urinalysis V/Q lung scan Pulmonary artery catheter (severe cases)

Acute Respiratory Failure Nursing and Collaborative Management Nursing Assessment Past health history Medications Surgery Tachycardia

Acute Respiratory Failure Nursing and Collaborative Management Nursing Assessment Fatigue Sleep pattern changes Headache Restlessness

Acute Respiratory Failure Nursing and Collaborative Management Nursing Diagnoses Ineffective airway clearance Ineffective breathing pattern Risk for imbalanced fluid volume Anxiety

Acute Respiratory Failure Nursing and Collaborative Management Nursing Diagnoses Impaired gas exchange Imbalanced nutrition: less than body requirements

Acute Respiratory Failure Nursing and Collaborative Management Planning Overall goals: ABGs and breath sounds within baseline No dyspnea Effective cough

Acute Respiratory Failure Nursing and Collaborative Management Prevention Thorough physical assessment History

Acute Respiratory Failure Nursing and Collaborative Management Respiratory Therapy Oxygen therapy Mobilization of secretions Effective coughing and positioning

Acute Respiratory Failure Nursing and Collaborative Management Respiratory Therapy Mobilization of secretions Hydration and humidification Chest physical therapy Airway suctioning

Acute Respiratory Failure Nursing and Collaborative Management Respiratory Therapy Positive pressure ventilation (PPV)

Acute Respiratory Failure Nursing and Collaborative Management Drug Therapy Relief of bronchospasm Bronchodilators

Acute Respiratory Failure Nursing and Collaborative Management Drug Therapy Reduction of airway inflammation Corticosteroids

Acute Respiratory Failure Nursing and Collaborative Management Drug Therapy Reduction of pulmonary congestion IV diuretics

Acute Respiratory Failure Nursing and Collaborative Management Drug Therapy Treatment of pulmonary infections IV antibiotics

Acute Respiratory Failure Nursing and Collaborative Management Drug Therapy Reduction of severe anxiety, pain, and agitation Benzodiazepines Narcotics

Acute Respiratory Failure Nursing and Collaborative Management Medical Supportive Therapy Treat the underlying cause Maintain adequate cardiac output and hemoglobin concentration Monitor BP, O2 saturation, urine output

Acute Respiratory Failure Nursing and Collaborative Management Nutritional Therapy Maintain protein and energy stores Enteral or parenteral nutrition Supplements