Respiratory Flashcards
Oxygen dissociation curve
LEFT = HIGHER AFFINITY - binds more in lungs LEFT = LOW!! (everything except pH) - LOW TEMP - LOW CO2 (hyperventilation) - LOW 2,3 DPG - HIGH pH (alkaloic) - FOETAL HB - CO
RIGHT = LESS AFFINITY - more O2 to tissues e.g. sickness, exercising muscles RIGHT = HIGH!! (everything except pH) - HIGH TEMP - HIGH CO2 (hypoventilation) - HIGH 2, 3 DPG - LOW pH (acidotic)
Ventilation
Oxygenation = PaO2
- Depends on MAP + FiO2
- Increase LV, iTime
- P50 = 27mmHg
Ventilation = PaCO2
- Frequency (F up = PaCO2 up)
- Minute volume (MV up = PaCO2 down)
MV = TV + RR
Compliance = change in volume/change in pressure
- FRC
Airway resistance e.g. asthma
- slow rate, moderate volume
Decreased compliance e.g. RDS, pneumonia, CCF
- rapid rate, small volume
Equations
PRESSURE (gas) inversely proportional to volume
VOLUME (gas) proportional to temperature
FLOW = CHANGE IN PRESSURE / RESISTANCE
RESISTANCE = VISCOSITY x LENGTH/RADIUS^4
PiO2 = 0.21 x (Patm - Pwater)
Water = 47mmHg
Sea level atm = 760mmHg
PiO2 at sea level = 0.21 x (760-47) = 150
PiO2 on mountain Patm = 650mmHg: 0.21 x (650-47) = 126
FRC, RV, TV, VC
FRC = What is left after tidal volume released in standard breath (need whole body plethysmography)
Residual volume = volume left after maximum possible exhalation
Tidal volume = volume with each standard breath
Vital capacity = volume with maximum breath
Restrictive lung disease
Problem with INTERSTITIAL tissue/lung PARENCHYMA
Restrict the expansion of lung -> stiff, less compliant
No significant problem in the airways
“Smaller lung” / smaller volume but more dense parenchyma e.g. neuromuscular weakness, interstitial lung disease (DCLO2 NORMAL in neuromuscular, LOW in interstitial)
Obstructive lung disease
Problem is with the AIRWAYS
Increased airway resistance - difficult expiration
No problem with parenchymal or lung tissue e.g. asthma, CF
Important values
FEV1/FVC 80% = normal (restrictive - same, obstructive <70%)
Bronchodilator response - 12% improvement in FEV1
Histamine response - 20% reduction in FEV1
Monitoring: FEV1 = obstructive. FVC = restrictive
FEF25-75 = small airway obstruction
Restrictive flow volume
LESS! TLC less / FRV less TV less / RV less VC less / FEV1 less FVC less
Compliance less, stiffness more
FEV1/FVC normal or increased
FEF25-75 normal or increased
Obstructive flow volume
TLC high (air trapping) FRC high RV high FEV1 less (most reproducible in CF) VC less
compliance more, stiffness less
FEV1/FVC less
FEF25-75 less
Flow volume loops
Obstructive lung disease
- Scooped out curve e.g. asthma, CF
Restrictive lung disease
- Similar shape but smaller e.g. interstitial lung disease, chest wall deformity
Neuromuscular weakness
- Small circle graph
Fixed upper airway obstruction
- Both inspiratory and expiratory flattened e.g. goitre, tracheal stenosis
Variable extrathoracic upper airway obstruction
- Inspiration flattened e.g. laryngomalacia, subglottic haemangioma, vocal cord palsy (bilateral normal cry, resp distress. Unilateral - weak cry, minimal resp distress, choke with feeds)
Variable intrathroacic upper airway obstruction
- Fixed inspiration e.g. tracheomalacia
Thumb sign
Epiglottis
Steeple sign
Croup
Irregular trachea
Bacterial tracheitis
Multi cystic lesion in lung
CCAM
Dextrocardia, sinusitis, bronchiectasis
Kartageners
