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Anaesthesiology
Respiratory Function in Anesthesia
Built from Barash Clinical Anesthesia, 9th Edition
What’s inside
8 sections · 144 slides
Overview
- Scope of this topic
- Key messages of this topic
- From applied pressure to gas exchange
Respiratory Mechanics
- Pressure difference as the driver of airflow
- The two impedances to inflation
- The equation of motion
- Limits of the basic model
- Work and power of breathing
- Compliance and elastance
- Transmural pressures across lung and chest wall
- Pressure and volume relationships of the lung
- Compliance is highest near functional residual capacity
- Surface tension and the Laplace relationship
- Hysteresis of the alveoli
- Dynamic pressure-volume loop of a tidal breath
- Bronchopulmonary segments of the lung
- Major divisions of the lung
- Major divisions of the lung (continued)
- Measuring compliance during anesthesia
- Pendelluft and stress recovery
- Driving pressure
- Driving pressure and postoperative pulmonary complications
- Cautions when lowering tidal volume
- Esophageal pressure and chest wall compliance
- Setting ventilation from transpulmonary pressure
Changes in Elastic Forces under Anesthesia
- Atelectasis under anesthesia
- Persistence and reversal of atelectasis
- Compressive mechanism of atelectasis
- Compression as the principal cause
- Positions and conditions that worsen compliance
- Airway pressure when pleural pressure is high
- PROBESE trial findings
- A stepwise recruitment technique
- Obesity versus pneumoperitoneum
- Resorption atelectasis
- Resorption without airway closure
Resistive Forces
- Two components of resistance
- Expiratory resistance and hyperinflation
- Anatomy of the trachea
- Tracheal mobility and tube position
- Main bronchi and take-off angles
- Bronchial lengths and anatomical variants
- Bronchioles
- Airway resistance and cross-sectional area
- Laminar and turbulent flow
- Reynolds number and gas density
- Tissue resistance
- Pressure-time waveform during an inspiratory pause
- Measurement of resistance
- Interrupter resistance technique
- Mechanisms by which anesthesia changes resistance
- Reduced airway diameter under anesthesia
- Lung volume, closing capacity and flow effects
- Intrinsic PEEP
- Time constants and incomplete exhalation
- Detecting intrinsic PEEP
Gas Exchange
- Ventilation and perfusion as the functional unit
- The normal ventilation-perfusion ratio
- Shunt, dead space and silent units
- Distribution of ventilation and perfusion in the upright lung
- Continuum of ventilation-perfusion relationships
- Determinants of regional ventilation-perfusion ratio
- West zones of pulmonary blood flow
- West zones of the lung
- Limits of the gravitational model
- Measurement of ventilation-perfusion distribution
- Determinants of oxygen delivery
- The alveolar gas equation
- The alveolar gas equation at altitude
- Alveolar-arterial oxygen gradient
- The PaO2 to FiO2 ratio
- Pathway from atelectasis to hypoxemia
- Shunt as the cause of hypoxemia under anesthesia
- Mixed venous oxygen and arterial oxygenation
- Hypoxic pulmonary vasoconstriction
- Determinants of alveolar carbon dioxide
- Alveolar ventilation versus minute ventilation
- Three components of dead space
- Instrumental dead space
- Quantifying dead space
Control of Breathing
- Central respiratory centers
- Central nervous system respiratory centers
- Peripheral and central chemoreceptors
- Central carbon dioxide sensing
- Carbon dioxide ventilatory response curve
- Resting PaCO2 and the apneic threshold
- Pattern of the ventilatory response to hypercarbia
- Deglutition and vomiting reflexes
- The cough reflex
- Pulmonary proprioception and stretch reflexes
- Golgi tendon organs and the Hering-Breuer reflex
- Anesthetic effects on alveolar ventilation
- Rate of carbon dioxide rise during apnea
- Dead space and mismatch under anesthesia
- Why shunt affects carbon dioxide less than oxygen
- Carbon dioxide production under anesthesia
Lung Volumes and Pulmonary Function Tests
- Lung volumes and capacities
- Tidal volume
- Vital capacity
- Inspiratory capacity
- Expiratory reserve volume and residual volume
- Forced vital capacity
- Forced vital capacity thresholds and the single breath count
- Forced expiratory volume
- The FEV1 to FVC ratio
- Effort dependence of the FEV1 to FVC ratio
- Forced expiratory flow over the middle half of forced vital capacity
- Interpreting forced expiratory flow
- Flow-volume loop
- Clinical role of flow-volume loops
- Carbon monoxide diffusing capacity
- Normal values and derivations of diffusing capacity
- Factors that influence diffusing capacity
- Diseases that lower diffusing capacity
- Spirometry in practice
- Identifying a restrictive defect
- Distinguishing restrictive from obstructive results
- Pulmonary function tests in restrictive and obstructive lung disease
- Indications for preoperative pulmonary function tests
Perioperative Respiratory Care
- Goals of respiratory care during anesthesia
- Extending care across the perioperative period
- Populations at elevated risk
- Populations at elevated risk of postoperative pulmonary complications
- Populations at elevated risk of postoperative pulmonary complications (continued)
- Perioperative pulmonary rehabilitation
- Takeaways on mechanics
- Takeaways on gas exchange and control
- Takeaways on testing and outcomes
- References
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- References (continued)
- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition