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 /  \\\\\\\\\\\\\. Mohammad Rezaei Fellowship of Pediatric Pulmonology

Dec 23, 2015



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  • Mohammad Rezaei Fellowship of Pediatric Pulmonology
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  • Respiratory distress Respiratory distress is a clinical impression
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  • Respiratory failure inability of the lungs to provide sufficient oxygen (hypoxic respiratory failure) or remove carbon dioxide (ventilatory failure) to meet metabolic demands.
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  • Respiratory failure Pao 2 < 60 torr with breathing of room air and Paco 2 > 50 torr resulting in acidosis, the patient's general state, respiratory effort, and potential for impending exhaustion are more important indicators than blood gas values.
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  • Respiratory distress can occur in patients without respiratory disease, and respiratory failure can occur in patients without respiratory distress.
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  • Respiratory failure Acute Chronic
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  • The physiologic basis of respiratory failure determines the clinical picture. normal respiratory drive are breathless and anxious decreased central drive are comfortable or even somnolent.
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  • The causes: conditions that affect the respiratory pump conditions that interfere with the normal function of the lung and airways
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  • Respiratory Pump Dysfunction Decreased Central Nervous System (CNS) Input Head injury Ingestion of CNS depressant Adverse effect of procedural sedation Intracranial bleeding Apnea of prematurity Peripheral Nerve/Neuromuscular Junction Spinal cord injury Organophosphate/carbamate poisoning Guillian-Barre syndrome Myasthenia gravis Infant botulism Muscle Weakness Respiratory muscle fatigue due to increased work of breathing Myopathies/Muscular dystrophies
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  • Airway/Lung Dysfunction Central Airway Obstruction Croup Foreign body Anaphylaxis Bacterial tracheitis Epiglottitis Retropharyngeal abscess Bulbar muscle weakness/dysfunction Peripheral Airways/Parenchymal Lung Disease Status asthmaticus Bronchiolitis Pneumonia Acute respiratory distress syndrome Pulmonary edema Pulmonary contusion Cystic fibrosis Chronic lung disease (eg, bronchopulmonary dysplasia)
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  • Arterial gas composition depends on : the gas composition of the atmosphere the effectiveness of alveolar ventilation pulmonary capillary perfusion diffusion across the alveolar capillary membrane
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  • Alveolar Gas Composition P A O2 = P I O2 (PCO2/R) P I O2 = (BP P H2O ). Fio2 P A O2 = [(BP P H2O ). Fio2] (PCO2/R)
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  • Hypoventilation V A = V T. RR low respiratory rate and shallow breathing are both signs of hypoventilation.
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  • Dead Space Ventilation Anatomical Physiological V D / V T = (P a CO2-P E CO2)/ P a CO2 = 0.33 Increases in decreased pulmonary perfusion: PHTN, hypovolemia, decreased cardiac output
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  • Alveolar Ventilation V A = (V T -V D ). RR
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  • Hypoventilation The Paco2 increases in proportion to a decrease in ventilation. Pao2 falls approximately the same amount as the Paco2 increases.
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  • Hypoventilation The relationship between oxygenation and hypoventilation is complicated by the shape of the Hb-dissociation curve Because of the dissociation curve, a patient who exhibits alarming CO2 retention might have a near normal oxygen saturation.
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  • 1. PO2 100 mm Hg= SpO2 of 97% 2. PO2 60mm Hg= SpO2 of90% When Paco2 increases from 40 to 70 mm Hg, a dangerous level of hypoventilation, might have a Pao2 that has decreased from 100 to 60 mm Hg and, therefore, maintain an oxygen saturation of 90%.
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  • Thus: oximetry is not a sensitive indicator of the adequacy of ventilation. This is particularly true when a patient is receiving oxygen.
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  • Lung/Airway Disease Diseases of the lung or airways affect gas exchange most often by disrupting the normal matching of V/Q or by causing a shunt. usually can maintain a normal Paco2 as lung disease worsens simply by breathing more. hypoxemia is the hallmark of lung disease
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  • Ventilation-Perfusion Mismatch
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  • hypoxemia due to V/Q mismatch & hypoxemia due to shunt administering Oxygen
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  • Intrapulmonary Shunt
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  • Diffusion diffusion defects manifest as hypoxemia rather than hypercarbia. Examples : interstitial pneumonia, ARDS, Scleroderma, Pulmonary lymphangiectasia,
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  • Monitoring a Child in Respiratory Distress and Respiratory Failure
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  • Clinical Examination Clinical observation is the most important component of monitoring.
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  • ABG & Oximetry ABG /CBG/ VBG Oximetry - Oximetry provides an invaluable and usually accurate measurement of oxygenation. - important to recognize its technical limitations
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  • ConditionLimitation Dark skin pigment Anemia Causes inadequate signal Bright external light Motion Decreased perfusion Venous pulsations Severe right heart failure Tricuspid regurgitation Tourniquet or blood pressure cuff above site Results in low reading Abnormal hemoglobin concentration Methemoglobin Unreliable reading (tends to read 80% to 85% saturation regardless of actual saturation) SS hemoglobin Saturationaccurate, but hemoglobin dissociation curve shifted to right CarboxyhemoglobinSpuriously high saturation readings
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  • Acute Respiratory Failure
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  • ARF most common cause of cardiac arrest in children. When presented with a child who has: a decreased level of consciousness, slow/shallow breathing, or increased respiratory drive, the possibility of ARF should be considered
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  • First: to assure adequate gas exchange and circulation (the ABCs). Oxygen Administration to maintain . If Ventilation is or appears to be inadequate .. Intubation ? Need ICU
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  • Chronic Respiratory Failure
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  • CRF is seen most commonly in children who have: Respiratory muscle weakness (muscular dystrophy, anterior horn cell disease) or severe chronic lung diseases (BPD, end- stage cystic fibrosis)
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  • usually has an insidious onset Most children do not have dyspnea. PH normal or near normal, unless.. Recognizing need careful monitoring of children at risk for CRF
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  • Disordered sleep Daytime hypersomnolence Morning headaches Altered mental status Increased respiratory symptoms Cardiomegaly Decreased baseline oxygenation CRF often presents first during sleep Develops an intercurrent illness, Fever
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