Respiratory Failure By: Dr.Samet.M Yazd University.
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Transcript of Respiratory Failure By: Dr.Samet.M Yazd University.
Respiratory Failure
By:
Dr.Samet.MYazd University
Respiratory Failure
Respiratory failure is a condition in which the respiratory system fails in one or both of its gas-exchanging functions:
oxygenation
carbon dioxide elimination
CLASSIFICATION
Acute & Chronic
Hypercapnic: PaCO2 >45 mmHg
Hypoxemic: PaO2 <55 mmHg when FIO2 ≥0.60
Distinctions between acute and chronic respiratory failure
Arterial blood gas values
Presence of markers of chronic hypoxemia
( polycythemia or cor pulmonale)
Abrupt changes in mental status
PATHOPHYSIOLOGY
Controller dysfunctionController dysfunction
Pump dysfunctionPump dysfunction
Airway system dysfunctionAirway system dysfunction
Alveolar compartment dysfunctionAlveolar compartment dysfunction
Pulmonary vascular dysfunctionPulmonary vascular dysfunction
Controller dysfunctionController dysfunction“central apnea“central apnea””
Structural: meningoencephalitis, localized tumors or vascular abnormalities of the medulla,strokes affecting medullary control centers
Pharmacologic: narcotic, sedative
Metabolic: severe myxedema,hepati failure,advanced uremia,hypothermia
Elevation of Pco2 in the CNS: chronic metabolic alkalosis (diuretic use)
Obesity-hypoventilation syndrome
COPD
Controller dysfunctionController dysfunction“central apnea“central apnea””
Determine rate & depth of breathingDetermine rate & depth of breathing
Determine pattern of breathingDetermine pattern of breathing
Determine amount of effort for breathingDetermine amount of effort for breathing
1.1. Awareness patient without sedative use can`t Awareness patient without sedative use can`t increase RR>12/min or make use of accessory increase RR>12/min or make use of accessory musclesmuscles
2.2. Hypoxemia,HypercapniaHypoxemia,Hypercapnia
3.3. PAo2-Pao2 was normalPAo2-Pao2 was normal
4.4. Type II respiratory failureType II respiratory failure
Pump DysfunctionPump DysfunctionDecreased respiratory muscle strength:
Muscle fatigue Recovery from acute respiratory failure, high respiratory rates, increased inspiratory time
Disuse atrophyProlonged mechanical ventilation, following phrenic nerve injury
Electrolyte abnormalities
Decreased motor neuron function:
Decreased phrenic nerve output Polyneuropathy, Guillain-Barr´e syndrome, phrenic nerve transection or injury,
Poliomyelitis
Decreased neuromuscular transmissionMyasthenia gravis, use of paralyzing agents
Pharmacologic:paralyzing agents, corticosteroids, cholinergic crisis, aminoglycosides
Structural abnormalities: Kyphoscoliosis,Obesity,Ascites,Distention,Flail chest,Thoracoplasty
Pump DysfunctionPump DysfunctionParadoxical movement of diaphragmParadoxical movement of diaphragm
Respiratory distressRespiratory distress
Vital capacity<10ml/kgVital capacity<10ml/kg
Inspiratory force<-20cmH2OInspiratory force<-20cmH2O
RSBI>105RSBI>105
Transdiaphragmatic pressureTransdiaphragmatic pressure
EMG & NCVEMG & NCVHypercapniaHypercapnia
Type II respiratory failureType II respiratory failure
Airways System DysfunctionAirways System Dysfunction
Upper airways:acute epiglottitis, aspirated foreign body, tracheal tumor
narrowing of the trachea or glottis by fibrotic tissue
Lower airways: COPD, asthma, advanced cystic fibrosis
Airways System DysfunctionAirways System Dysfunction
A greater transthoracic pressure gradient requirement
The resistive work of breathing is increased Vo2
Tidal volume falls and dead space ventilation increases
Respiratory muscle fatigue shallow breathing pattern
Air trapping hyperinflation diaphragm flattening
Stirdor,Bronchospasm(wheez,rhonchi) Raw>10 cmH2O/L/S Type II respiratory failureType II respiratory failure
Alveolar Compartment DysfunctionAlveolar Compartment Dysfunction
Cardiogenic and noncardiogenic pulmonary edema
Diffuse pneumonia
Extensive pulmonary hemorrhage
Aspiration of stomach contents
Neardrowning
Lung contusion
Hypoxemia,HypercapniaHypoxemia,HypercapniaType I respiratory failureType I respiratory failure
Alveolar Compartment DysfunctionAlveolar Compartment DysfunctionHypoxemia:
Diffuse alveolar filling large right-to-left shunt
Interstitial edema impair diffusion across the alveolar-capillary membrane
Hypercapnia: Increased ventilatory demand:
Hypoxemia
Vd / Vt,
Elastic work of breathing (reduced lung compliance)
Resistive work of breathing (airway narrowing and airway reactivity)
Neural drive to breathe (mediated by pulmonary parenchymal vagal fibers) Decreased ventilatory supply:
Alveolar flooding
Reduced lung elasticity
Respiratory muscle fatigue
Reduced blood supply to the diaphragm secondary to shock
Alveolar Compartment DysfunctionAlveolar Compartment Dysfunction
ConsolidationConsolidation
bronchial sound,egophonia,dullnessbronchial sound,egophonia,dullness
Static compliance<30 ml/cmH2OStatic compliance<30 ml/cmH2O
Type I respiratory failureType I respiratory failure
Pulmonary Vascular DysfunctionPulmonary Vascular Dysfunction
Symptoms & Signs of right HFSymptoms & Signs of right HF::
JVP,S3,RV heave,TR,S2JVP,S3,RV heave,TR,S2
EKG RBBB,RV strain patternEKG RBBB,RV strain pattern
CX-Ray Pulmonary artery enlargementCX-Ray Pulmonary artery enlargement
Type II respiratory failureType II respiratory failure
Respiratory FailureType I:Type I: Acute Hypoxemic Respiratory Failure Acute Hypoxemic Respiratory Failure
alveolar flooding and subsequent intrapulmonary shunt physiologyalveolar flooding and subsequent intrapulmonary shunt physiology
pulmonary edema, pneumonia, or alveolar hemorrhagepulmonary edema, pneumonia, or alveolar hemorrhage
Type II:Type II: Alveolar hypoventilationAlveolar hypoventilation impaired CNS drive to breathe, impaired strength with failure of impaired CNS drive to breathe, impaired strength with failure of
neuromuscular function in the respiratory system, increased load on neuromuscular function in the respiratory system, increased load on the respiratory system the respiratory system
Type III:Type III: Lung atelectasisLung atelectasis perioperative respiratory failureperioperative respiratory failure
Type IV:Type IV: Hypoperfusion of respiratory musclesHypoperfusion of respiratory muscles
shockshock
Hypoxemic Respiratory Failure
Alveolar hypoventilation
Ventilation-perfusion Mismatch
Shunt
Diffusion limitation
PAO2 = FIO2 x (PB – PH2O) – PaCO2/R PAO2 = 150 – 1.25 x PaCO2 PAO2 = 150 – 1.25 x PaCO2 PAo2 − Pao2 = [PIo2 − PaCo2/R] − Pao2
Hypoxemic Respiratory Failure
Although changes in minute and alveolar ventilation can change Paco2 considerably, this is not so for Pao2.
At a Pao2>55-60 mmHg,the effect of increasing ventilation on CaO2 is minimal,since the oxyhemoglobin dissociation curve is flat in this range.
In the absence of underlying pulmonary disease, the hypoxemia accompanying alveolar hypoventilation is characterized by a normal alveolar-arterial oxygen gradient.
Hypercapnic Respiratory Failure
Paco2 is determined:
Rate of CO2 production (˙Vco2 ) rate of CO2 production # rate of CO2 elimination
) CvCO2-CaCO2.(CO.10 # 90-130 L/min/M2
Level of alveolar ventilation VA = K . ˙Vco2/Paco2
VE = K . (˙Vo2 . RQ) / (Paco2 / [1 − Vd / Vt] )
˙ Vo2 = rate of O2 consumption
RQ = respiratory quotient