Acute Respiratory Failure

Respiratory SystemConsists 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 UnitFig. 66-1

Normal ABGs

pH = 7.35-7.45

CO2 = 35-45

HCO3= 23-27

Respiratory and Metabolic Acidosis and AlkalosisCO2 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 InterpretationStep 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 (contd)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 alkaloticIf the HCO3 is above 27, the patient is alkalotic; if the HCO3 is below 23, the patient is acidotic

ABG Interpretation (contd)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 #1pH = 7.36CO2 = 41HCO3 = 27

Diagnosis: ?

ABG Example #2pH = 7.49CO2 = 37HCO3 = 32

Diagnosis: ?

ABG Example #3pH = 7.29CO2 = 50HCO3 = 26

Diagnosis: ?

ABG Example #4pH = 7.40CO2 = 32HCO3 = 30

Diagnosis: ?

Acute Respiratory Failure

Results from inadequate gas exchange

Insufficient O2 transferred to the bloodHypoxemia

Inadequate CO2 removalHypercapnia

Acute Respiratory Failure with Diffuse Bilateral Infiltrates

Acute Respiratory Failure

Not a disease but a conditionResult 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 bodys needs

Acute Respiratory Failure

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

Classification of Respiratory FailureFig. 66-2

Acute Respiratory FailureHypoxemic Respiratory FailurePaO2 of 60 mm Hg or less (Normal = 80 - 100 mm Hg)Inspired O2 concentration of 60% or greater

Acute Respiratory FailureHypercapnic Respiratory FailurePaCO2 above normal (>45 mm Hg)Acidemia (pH

Hypoxemic Respiratory FailureEtiology and Pathophysiology

Causes:Ventilation-perfusion (V/Q) mismatchShuntDiffusion limitationAlveolar hypoventilation

V-Q MismatchingI) 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 ventilationPoor perfusion

Range of V/Q RelationshipsFig. 66-4

Hypoxemic Respiratory FailureEtiology and Pathophysiology

Causes V/Q mismatchCOPDPneumoniaAsthmaAtelectasisPulmonary embolus

Hypoxemic Respiratory FailureEtiology and Pathophysiology

II) ShuntAn extreme V/Q mismatchBlood passes through parts of respiratory system that receives no ventilationd/t obstruction OR fluid accumulationNot 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 FailureEtiology and Pathophysiology

Causes Diffusion limitationsSevere emphysemaRecurrent pulmonary emboliPulmonary fibrosisHypoxemia present during exercise

Diffusion LimitationFig. 66-5

Alveolar HypoventilationIV) Alveolar Hypoventilation

Is a generalized decrease in ventilation of lungs and resultant buildup of CO2

Hypoxemic Respiratory FailureEtiology and Pathophysiology

Causes Alveolar hypoventilationRestrictive lung diseaseCNS diseaseChest wall dysfunctionNeuromuscular disease

Hypoxemic Respiratory FailureEtiology and Pathophysiology

Interrelationship of mechanismsHypoxemic respiratory failure is frequently caused by a combination of two or more of these four mechanismsEffects of hypoxemiaBuild up of lactic acid metabolic acidosis cell deathCNS depressionHeart tries to compensate HR and COIf no compensation: O2, acid, heart fails, shock, multi-system organ failure

Hypercapnic Respiratory FailureEtiology and Pathophysiology

Imbalance between ventilatory supply and demand

Occurs when CO2 is increased

Causes Hypercapnic Respiratory FailureI) Alveolar Hypoventilation and VQ Mismatch:

Ventilation not adequate to eliminate CO2Leads to respiratory acidosis

Eg. Narcotic OD; Guillian-Barre, ALS, COPD, asthma

Causes Hypercapnic Respiratory FailureII) VQ Mismatch:

- Leads to increased work of breathing

- Insufficient energy to overcome resistance; ventilation falls; PCO2; respiratory acidosis

Hypercapnic Respiratory FailureCategories of Causative Conditions

I) Airways and alveoliAsthmaEmphysemaChronic bronchitisCystic fibrosis

Hypercapnic Respiratory Failure Categories of Causative Conditions

II) Central nervous systemDrug overdoseBrainstem infarctionSpinal cord injuries

Hypercapnic Respiratory Failure Categories of Causative Conditions

III) Chest wallFlail chestFracturesMechanical restrictionMuscle spasm

Hypercapnic Respiratory Failure Categories of Causative Conditions

IV) Neuromuscular conditionsMuscular dystrophyMultiple sclerosis

Respiratory FailureTissue Oxygen Needs

Major threat is the inability of the lungs to meet the oxygen demands of the tissues

Respiratory FailureClinical Manifestations

Sudden or gradual onsetA sudden in PaO2 or rapid in PaCO2 is a serious condition

Respiratory FailureClinical Manifestations

When compensatory mechanisms fail, respiratory failure occursSigns may be specific or nonspecific

Respiratory FailureClinical Manifestations

Severe morning headacheCyanosis Late signTachycardia and mild hypertensionEarly signs

Respiratory FailureClinical Manifestations

Consequences of hypoxemia and hypoxiaMetabolic acidosis and cell death Cardiac outputImpaired renal function

Respiratory FailureClinical Manifestations

Specific clinical manifestationsRapid, shallow breathing patternSitting uprightDyspnea

Respiratory FailureClinical Manifestations

Specific clinical manifestationsPursed-lip breathingRetractionsChange in Inspiratory:Expiratory ratio

Respiratory FailureDiagnostic Studies

Physical assessmentABG analysisChest x-rayCBCECG

Respiratory FailureDiagnostic Studies

Serum electrolytesUrinalysisV/Q lung scanPulmonary artery catheter (severe cases)

Acute Respiratory FailureNursing and Collaborative Management

Nursing AssessmentPast health historyMedicationsSurgery Tachycardia

Acute Respiratory FailureNursing and Collaborative Management

Nursing AssessmentFatigueSleep pattern changesHeadacheRestlessness

Acute Respiratory FailureNursing and Collaborative Management

Nursing DiagnosesIneffective airway clearanceIneffective breathing patternRisk for imbalanced fluid volume Anxiety

Acute Respiratory FailureNursing and Collaborative Management

Nursing DiagnosesImpaired gas exchangeImbalanced nutrition: less than body requirements

Acute Respiratory FailureNursing and Collaborative Management

PlanningOverall goals:ABGs and breath sounds within baselineNo dyspnea Effective cough

Acute Respiratory FailureNursing and Collaborative Management

PreventionThorough physical assessment History

Acute Respiratory FailureNursing and Collaborative Management

Respiratory TherapyOxygen therapyMobilization of secretionsEffective coughing and positioning

Acute Respiratory FailureNursing and Collaborative Management

Respiratory TherapyMobilization of secretionsHydration and humidificationChest physical therapyAirway suctioning

Acute Respiratory FailureNursing and Collaborative ManagementRespiratory TherapyPositive pressure ventilation (PPV)

Acute Respiratory FailureNursing and Collaborative Management

Drug TherapyRelief of bronchospasmBronchodilators

Acute Respiratory FailureNursing and Collaborative Management

Drug TherapyReduction of airway inflammationCorticosteroids

Acute Respiratory FailureNursing and Collaborative Management

Drug TherapyReduction of pulmonary congestionIV diuretics

Acute Respiratory FailureNursing and Collaborative Management

Drug TherapyTreatment of pulmonary infectionsIV antibiotics

Acute Respiratory FailureNursing and Collaborative Management

Drug TherapyReduction of severe anxiety, pain, and agitationBenzodiazepinesNarcotics

Acute Respiratory FailureNursing and Collaborative Management

Medical Supportive TherapyTreat the underlying causeMaintain adequate cardiac output and hemoglobin concentrationMonitor BP, O2 saturation, urine output

Acute Respiratory FailureNursing and Collaborative Management

Nutritional TherapyMaintain protein and energy storesEnteral or parenteral nutritionSupplements