Advanced Respiratory Physiology
In a healthy adult, what is the normal range for end-tidal CO₂ (EtCO₂), and what does a sudden drop in EtCO₂ during resuscitation usually indicate?
Normal EtCO₂ is 35–45 mmHg; a sudden drop often indicates decreased cardiac output or cardiac arrest.
A patient with severe asthma presents with “silent chest” and bradycardia. What does this indicate?
What is impending respiratory failure?
Typical adult nebulized dose of albuterol for bronchospasm.
2.5 mg in 3 mL of normal saline via nebulizer.
This positive pressure ventilation mode delivers one pressure on inspiration and another on exhalation.
What is BiPAP (Bilevel Positive Airway Pressure)?
In emphysema, destruction of these structures reduces alveolar surface area and elastic recoil.
What are alveolar walls or septa?
Name two conditions that cause diffusion impairment rather than ventilation impairment
What are pulmonary edema and pneumonia?
Which breath sound is continuous, high-pitched, and typically heard during exhalation?
What is a wheeze?
Standard ipratropium bromide dose for adult nebulizer therapy.
0.5 mg (500 mcg) via nebulizer
Describe the main difference between CPAP and BiPAP.
CPAP delivers a single continuous pressure; BiPAP alternates pressures for inhalation/exhalation.
This condition is defined by chronic productive cough for ≥3 months/year for ≥2 consecutive years.
What is chronic bronchitis?
This respiratory pattern, characterized by alternating apnea and hyperpnea, often indicates brainstem injury.
What are Cheyne–Stokes respirations?
End-tidal CO₂ is most useful for monitoring what aspect of respiratory function?
What is ventilation (effectiveness of CO₂ elimination)?
IV magnesium sulfate dose for severe asthma attack.
2 grams IV over 10–20 minutes.
During bag-mask ventilation, excessive pressure can cause this life-threatening complication.
What is tension pneumothorax?
Explain why patients with chronic bronchitis appear cyanotic and overweight (“blue bloaters”).
Hypoxia and hypercapnia from mucus obstruction and V/Q mismatch cause cyanosis and fluid retention.
During quiet inspiration, approximately what percentage of the work of breathing is performed by the diaphragm?
About 60–70%.
On pulse oximetry, a reading of 100% may be misleading in this poisoning.
What is carbon monoxide poisoning?
IM epinephrine dose for severe asthma or anaphylaxis (1:1,000 concentration).
0.3 to 0.5 mg IM every 5–15 minutes as needed.
When ventilating a patient with severe asthma or COPD, what inspiratory-to-expiratory (I:E) ratio should be targeted to prevent air trapping and auto-PEEP?
A ratio of 1:3 to 1:4 to allow prolonged exhalation.
Status asthmaticus is defined as an asthma attack that fails to respond to what?
Standard bronchodilator therapy.
Explain how renal compensation responds to chronic respiratory acidosis.
Kidneys retain bicarbonate (HCO₃⁻) and excrete hydrogen ions to buffer excess CO₂.
In COPD patients, what is the expected change in PaO₂ and PaCO₂ on arterial blood gas?
Decreased PaO₂ and increased PaCO₂ (chronic respiratory acidosis with compensation).
Methylprednisolone IV dose for acute asthma or COPD exacerbation.
125 mg IV bolus.
Name one indication for endotracheal intubation in a severe asthma patient.
What is exhaustion, altered mental status, or respiratory arrest?
A patient with severe COPD suddenly becomes unresponsive after receiving high-flow oxygen. Explain the pathophysiologic mechanism for this deterioration and the correct management response.
High-flow O₂ can suppress the hypoxic drive in chronically hypercapnic patients, leading to hypoventilation and CO₂ narcosis. Management includes reducing FiO₂ to maintain SpO₂ around 88–92%, providing ventilatory support (e.g., CPAP/BiPAP), and monitoring EtCO₂.