Questions and Answers
What is the airway resistance formula?
Raw = ∆P / V
What does Raw stand for?
What does ∆P represent in respiratory terms?
Pressure Change
What does V stand for in the airway resistance formula?
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How is pressure change calculated?
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Which two pressures are used in calculating pressure change?
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The normal airway resistance ranges from 0.6 - 2.4 cm/H2O/L/sec.
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What is the normal airway resistance for intubated patients?
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What is the flow rate for normal airway resistance in healthy and intubated patients?
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An endotracheal tube will give you greater airway resistance.
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How do you convert flow rate from L/min to L/sec?
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What does ↑ Raw indicate about the diameter of an airway?
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What is the relationship between airway resistance (Raw) and length?
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What clinical conditions may lead to increased airway resistance?
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What does WOB stand for?
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What relationship exists between ∆P and V?
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What happens when severe airflow obstruction remains uncorrected?
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When mechanical ventilation is useful?
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Study Notes
Airway Resistance Overview
- Airway resistance (Raw) is calculated using the formula: Raw = ∆P / V.
- ∆P represents the change in pressure, defined by the difference between peak inspiratory pressure (PIP) and plateau pressure.
- Flow (V) is the volume of air flow, typically measured in L/sec.
Key Measurements
- Normal airway resistance ranges from 0.6 to 2.4 cm/H2O/L/sec.
- In intubated patients, normal airway resistance is about 5 cm/H2O/L/sec.
- An average flow rate for healthy and intubated patients is 30 L/min or 0.5 L/sec.
Impact of Equipment
- Endotracheal (ET) tubes increase airway resistance due to their length.
- When calculating Raw, convert flow rates from L/min to L/sec by dividing by 60.
Relationships and Resistance
- Airway resistance varies directly with the length of the airway and inversely with the diameter.
- Increased Raw leads to decreased flow (V), increasing work of breathing (WOB).
- Decreased Raw results in increased flow (V), reducing WOB.
Clinical Significance
- WOB measures the effort required to breathe, which can indicate the necessity for mechanical ventilation.
- Conditions that increase airway resistance include Chronic Obstructive Pulmonary Disease (COPD), mechanical obstructions, and infections like laryngotracheobronchitis.
Common Conditions Affecting Raw
- COPD can involve emphysema, chronic bronchitis, asthma, and bronchiectasis.
- Mechanical issues leading to increased Raw may involve post-intubation obstructions or foreign body aspiration.
- Infections like croup or epiglottitis can also cause elevated Raw.
Visualization and Interpretation
- In flow volume loops, an increase in Raw is indicated by bowing of the inspiratory limb due to excessive inspiratory flow.
- The peak pressure on the pressure-volume loop is observed during inhalation, while on exhalation, both pressure and tidal volume (Vt) decrease.
Mechanical Ventilation
- Mechanical ventilation becomes necessary when a patient cannot maintain adequate ventilation for gas exchange, particularly during high WOB situations.
- Inability to overcome increased WOB can lead to ventilatory failure, impacting oxygen and carbon dioxide exchange.
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Description
Test your knowledge on airway resistance concepts with these flashcards. Learn essential formulas, definitions, and components related to airway resistance in respiratory physiology. Perfect for students in health sciences or related fields.
