Upload
elmer-henderson
View
219
Download
0
Tags:
Embed Size (px)
Citation preview
/ \\\\\\\\\\\\\
RESPIRATORY FAILURE
Mohammad Rezaei
Fellowship of Pediatric Pulmonology
Respiratory distress
Respiratory distress is a clinical impression
Respiratory failure
inability of the lungs to provide sufficient oxygen (hypoxic respiratory failure) or remove carbon dioxide (ventilatory failure) to meet metabolic demands.
Respiratory failure
Pao2 < 60 torr with breathing of room air and
Paco2 > 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.
Respiratory distress can occur in patients without respiratory disease,
and
respiratory failure can occur in patients without respiratory distress.
Respiratory failure
Acute Chronic
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.
The causes:
conditions that affect the respiratory pump
conditions that interfere with the normal function of the lung and airways
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
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)
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
Alveolar Gas Composition
PAO2 = PIO2 – (PCO2/R)
PIO2 = (BP – PH2O) . Fio2 PAO2 = [(BP – PH2O) . Fio2] – (PCO2/R)
Hypoventilation VA = VT . RR
low respiratory rate and shallow breathing are both signs of hypoventilation.
Dead Space Ventilation
Anatomical Physiological
VD/ VT = (PaCO2-PECO2)/ PaCO2 = 0.33
Increases in decreased pulmonary perfusion: PHTN, hypovolemia, decreased cardiac output
Alveolar Ventilation
VA = (VT-VD). RR
Hypoventilation
The Paco2 increases in proportion to a decrease in ventilation.
Pao2 falls approximately the same amount as the Paco2 increases.
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.
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%.
Thus: oximetry is not a sensitive indicator of the adequacy of ventilation.
This is particularly true when a patient is receiving oxygen.
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
Ventilation-Perfusion Mismatch
hypoxemia due to V/Q mismatch
& hypoxemia due to shunt
administering Oxygen
Intrapulmonary Shunt
Diffusion
diffusion defects manifest as hypoxemia rather than hypercarbia.
Examples :
interstitial pneumonia, ARDS, Scleroderma, Pulmonary lymphangiectasia,…
Monitoring a Child in Respiratory Distress and
Respiratory Failure
Clinical Examination
Clinical observation is the most important component of monitoring.
ABG & Oximetry
ABG /CBG/ VBG
Oximetry- Oximetry provides an invaluable and usually accurate measurement of oxygenation.
- important to recognize its technical limitations
Condition LimitationDark skin pigmentAnemia Causes inadequate signalBright external lightMotion
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 read80% to 85% saturation regardless of actual saturation)
— SS hemoglobin Saturation accurate, but hemoglobin dissociation curve shifted to right
— Carboxyhemoglobin Spuriously high saturation readings
Acute Respiratory Failure
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
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
Chronic Respiratory Failure
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)
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
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