Control of Breathing Control of Breathing RESPIRATORY CENTRE (Medulla) MEDULLARY & CAROTID CHEMORECEPTORS Higher Control Centres RESPIRATORY REFLEXES DRUG EFFECTS e.g. OPIATES & CAFFEINE CRANIAL & SPINAL MOTOR NEURONES STRETCH & PROPRIOCEPTORS LUNGS & CHEST WALL INSPIRATION
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Control of BreathingControl of Breathing
RESPIRATORYCENTRE (Medulla)
MEDULLARY &CAROTID
CHEMORECEPTORS
Higher Control Centres
RESPIRATORYREFLEXES
DRUG EFFECTS e.g.OPIATES & CAFFEINE
CRANIAL & SPINALMOTOR NEURONES
STRETCH & PROPRIOCEPTORSLUNGS & CHEST WALL
INSPIRATION
ChemoreceptorsChemoreceptors
Medulla Oblongata and Carotid BodyMedulla Oblongata and Carotid BodyRespond to changes in pH, CORespond to changes in pH, CO22 and O and O22
Resetting of carotid chemoreceptors Resetting of carotid chemoreceptors occurs at birth in response to oxygenationoccurs at birth in response to oxygenation
Not essential at initiation of respiration but Not essential at initiation of respiration but used for control of breathing used for control of breathing
Responses are weak in the immediate Responses are weak in the immediate newborn period and in preterm babiesnewborn period and in preterm babies
DefinitionsDefinitionsTidal volume = volume of gas each breathTidal volume = volume of gas each breath
5 - 7 mL/Kg in babies 5 - 7 mL/Kg in babies Minute volume = vol. of gas each minuteMinute volume = vol. of gas each minute
200 – 400 mL/kg/min200 – 400 mL/kg/min
Minute volume = Tidal volume x resp. rateMinute volume = Tidal volume x resp. ratePaCO2 inversely PaCO2 inversely MV MV
PaCO2 PaCO2 ↓↓ by by ↑ tidal volume or ↑ resp. rate↑ tidal volume or ↑ resp. rateDead Space = Vol. of lung not involved in Dead Space = Vol. of lung not involved in
ventilation (eg, airways and ET tubes)ventilation (eg, airways and ET tubes)
ComplianceCompliance Compliance is a measure of the distensibility of Compliance is a measure of the distensibility of
the lungthe lung
Compliance = Compliance = Change in Volume (L)Change in Volume (L)
Change in Pressure (cm HChange in Pressure (cm H22O)O)
• Small & long ET tubesSmall & long ET tubes• Subglottic stenosisSubglottic stenosis
Work of BreathingWork of BreathingEnergy required to produce change in lung Energy required to produce change in lung
volumevolume Increases with decreased complianceIncreases with decreased compliance Increases with increased resistanceIncreases with increased resistance
If energy required to breath exceeds If energy required to breath exceeds capacity to supply oxygen to provide that capacity to supply oxygen to provide that energy then respiratory failure develops energy then respiratory failure develops requiring mechanical ventilationrequiring mechanical ventilation
Usually pretermUsually pretermTachypnoea > 60Tachypnoea > 60 Indrawing/ retraction/ recessionIndrawing/ retraction/ recessionGruntingGruntingNasal flaringNasal flaringCyanosis in airCyanosis in airPresents within a few hours of lifePresents within a few hours of life
Usually close to termUsually close to termTachypnoea 100-120/minTachypnoea 100-120/minOverinflated chestOverinflated chestNo grunting/ retractionNo grunting/ retractionSettles within 24-48 hoursSettles within 24-48 hours
TTN - AetiologyTTN - Aetiology
Delayed fetal lung fluid clearanceDelayed fetal lung fluid clearanceCaesarean section - no squeeze of thorax Caesarean section - no squeeze of thorax
at birthat birthMum not in labour - no catecholamine Mum not in labour - no catecholamine
surge to promote absorption of fetal lung surge to promote absorption of fetal lung fluidfluid
TTN - treatmentTTN - treatment
Prevention - avoid early elective Prevention - avoid early elective caesarean sections at termcaesarean sections at term
Oxygen supplementation and IV fluids until Oxygen supplementation and IV fluids until resolutionresolution
May be asymptomaticMay be asymptomaticMay be life threateningMay be life threateningSudden deterioration in gas exchangeSudden deterioration in gas exchangePoor colourPoor colourHypotension and tachycardiaHypotension and tachycardiaUnilateral overexpanded thoraxUnilateral overexpanded thorax
Pneumothorax - aetiologyPneumothorax - aetiology
Uneven alveolar ventilationUneven alveolar ventilationAir trapping and high pressure swingsAir trapping and high pressure swingsTracking of air from pulmonary interstitial Tracking of air from pulmonary interstitial
Spontaneous in 1% of all babiesSpontaneous in 1% of all babies Increases with mechanical ventilationIncreases with mechanical ventilation Increased x 4 with HMDIncreased x 4 with HMD Increased x 16 with CPAPIncreased x 16 with CPAP Increased x 34 with IPPVIncreased x 34 with IPPV
Mainly occurs in preterm babies ventilated Mainly occurs in preterm babies ventilated for HMDfor HMD
Gas trapping in perivascular sheathsGas trapping in perivascular sheaths Increased incidence at lower gestationsIncreased incidence at lower gestations
PIE - Clinical featuresPIE - Clinical features
Severe hypoxaemia and CO2 retentionSevere hypoxaemia and CO2 retentionDeteriorating clinical conditionDeteriorating clinical condition
X- RayX- RayOverinflation with gross cystic changesOverinflation with gross cystic changes
PIE - TreatmentPIE - Treatment
Lower PEEP and PIPLower PEEP and PIPParalysisParalysisHigh rate low pressure ventilationHigh rate low pressure ventilation? HFOV? HFOV? Selective bronchial intubation? Selective bronchial intubation
Persistent pulmonary Persistent pulmonary hypertension of the newbornhypertension of the newborn
Clinical featuresClinical features
Severe hypoxaemia (cyanosed in 100% O2)Severe hypoxaemia (cyanosed in 100% O2)No severe lung diseaseNo severe lung diseaseEvidence of R to L shunt (pre vs. postductal)Evidence of R to L shunt (pre vs. postductal)Structurally normal heartStructurally normal heart
PPHN - Aetiology and PPHN - Aetiology and predisposing factorspredisposing factors
Failure of NO synthaseFailure of NO synthaseAsphyxia/ acidosisAsphyxia/ acidosis InfectionInfectionDiaphragmatic herniaDiaphragmatic herniaAlveolar capillary dysplasiaAlveolar capillary dysplasiaMeconium aspiration syndromeMeconium aspiration syndrome
PPHN - treatmentPPHN - treatment
Minimal handlingMinimal handling Inotropic supportInotropic supportVentilation - maintain low normal CO2Ventilation - maintain low normal CO2ParalysisParalysisHyperventilation - ? Risk of PVLHyperventilation - ? Risk of PVLHFOVHFOVNitric OxideNitric OxidePulmonary vasodilators Pulmonary vasodilators
Meconium passage prior to deliveryMeconium passage prior to deliveryMeconium in pharynx and tracheaMeconium in pharynx and tracheaRespiratory distress post delivery with Respiratory distress post delivery with
typical X-ray changestypical X-ray changes
MAS - AetiologyMAS - Aetiology
Asphyxia and intrauterine stressAsphyxia and intrauterine stressPassage of meconium + gasping Passage of meconium + gasping
movementsmovements Inhalation usually prior to deliveryInhalation usually prior to delivery
MAS - effects of meconiumMAS - effects of meconium
Ball valve effect - air trappingBall valve effect - air trappingChemical irritation and pneumonitisChemical irritation and pneumonitisSuperinfection with bacteriaSuperinfection with bacteriaSurfactant inhibitionSurfactant inhibition
MAS - ManagementMAS - Management
Prevention in delivery suitePrevention in delivery suiteMinimal handlingMinimal handlingMaintain normoxaemiaMaintain normoxaemiaMay need ventilation + ? ParalysisMay need ventilation + ? ParalysisSurfactant lavageSurfactant lavageAntibioticsAntibiotics
Usually pretermUsually pretermHMD with PDAHMD with PDAPost surfactant therapyPost surfactant therapyCoagulopathyCoagulopathyCongestive cardiac failureCongestive cardiac failure
Protracted respiratory insufficiency and Protracted respiratory insufficiency and oxygen requirement beyond 28th day or oxygen requirement beyond 28th day or 36th week post conceptional age36th week post conceptional age
Very preterm with early ventilation for Very preterm with early ventilation for HMDHMD
Minimise ventilation and oxygen exposureMinimise ventilation and oxygen exposureHFOVHFOVEarly surfactantEarly surfactantCorticosteroids Corticosteroids Early extubationEarly extubation
SummarySummary Knowledge of respiratory anatomyKnowledge of respiratory anatomy Physiology of adaptation at birthPhysiology of adaptation at birth SurfactantSurfactant Gas exchangeGas exchange Gas transportGas transport Lung mechanicsLung mechanics
Application of knowledge to the clinical Application of knowledge to the clinical management of babies with respiratory diseasemanagement of babies with respiratory disease