Respiratory Physiology
What muscle is the primary driver of ventilation?
Diaphragm
Rationale: The diaphragm is the major muscle responsible for inspiration. When it contracts, it flattens and creates negative pressure to draw air into the lungs.
What oxygen device delivers the most precise FiO₂?
Venturi mask
Rationale: It mixes oxygen with room air using precise adapters and delivers a fixed, accurate concentration—ideal for COPD patients who need controlled FiO₂
What does a PaCO₂ > 45 mmHg indicate?
Respiratory acidosis
Rationale:
Elevated PaCO₂ indicates the body is retaining CO₂, which leads to decreased pH (acidosis). This often occurs with hypoventilation or COPD.
What is the earliest sign of hypoxia?
Restlessness
Rationale: Low oxygen levels affect the brain first, causing subtle behavioral or mental status changes before physical signs like cyanosis appear.
What does continuous bubbling in the water seal chamber usually indicate?
An air leak
Rationale:
Occasional bubbling is normal with pneumothorax resolution, but constant bubbling means air is escaping into the system. Always assess connections and the insertion site.
What does the P wave represent in the cardiac cycle?
Atrial depolarization (contraction)
Rationale:
The P wave is the first small upward deflection on ECG and reflects electrical activity spreading through the atria.
A patient is restless and tachypneic while on 2 L/min nasal cannula. What's your next nursing action?
Raise the head of the bed and assess breath sounds .
Rationale:
Restlessness and tachypnea are signs of hypoxia. Elevating HOB improves ventilation. Assessing breath sounds helps determine if there's fluid, obstruction, or poor gas exchange before escalating oxygen therapy.
What is the normal range for PaO₂
80-100 mmHg
Rationale: Partial pressure of oxygen in arterial blood (PaO₂) reflects how well oxygen moves from the lungs into the blood. Below 80 indicates hypoxemia.
Which device is preferred for COPD patients to prevent CO₂ retention?
Nasal cannula at low flow (1-2 L/min)
Rationale:
High oxygen flow can suppress their hypoxic drive to breathe. Low-flow devices minimize the risk of CO₂ narcosis.
Respiratory alkalosis is caused by what breathing pattern?
Hyperventilation
Rationale:
Blowing off too much CO₂ (via rabid breathing) raises pH, causing respiratory alkalosis. Common in anxiety, pain, or early asthma attacks
What's a late sign of hypoxia and why does it occur?
Cyanosis; it occurs due to desaturated hemoglobin in capillaries.
Rationale: When hemoglobin is no longer carrying enough O₂, tissues become blue-tinged, especially in lips, fingers, and earlobes.
What's the immediate priority actions if a chest tube becomes dislodged?
Cover the site with a sterile petroleum gauze dressing and tape on 3 sides.
Rationale:
Taping on 3 sides allows air to escape but prevent air from entering, reducing the risk of tension pneumothorax.
Define stroke volume and list three factors that influence it.
Stroke volume = amount of blood ejected per beat; affected by preload, afterload, and contractility.
Rationale:
Preload: Volume in ventricles at end-diastole
Afterload: Resistance to ventricular ejection
Contractility: Strength of myocardial contraction
Why is preoxygenation necessary before suctioning a ventilated patient?
To prevent hypoxia during suctioning.
Rationale:
Suctioning temporarily removes oxygen along with secretions. Preoxygenating increases O₂ reserves and reduces the risk of desaturation.
Define diffusion in gas exchange.
The movement of gases from areas of high concentration to low concentration across the alveolar-capillary membrane.
Rationale:
Oxygen diffuses from alveoli (high 0₂) into capillaries (low O₂) while CO₂ diffuses the opposite direction.
What is the flow rate range and FiO₂ delivered by a simple face mask?
Flow 6-10 L/min, FiO₂ delivered by a simple face mask?
Rationale:
It requires at least 6 L/min to flush out CO₂. Less than 6 L/min may result in CO₂ rebreathing.
What is the normal range for HCO₃ and what does it represent?
22-26 mEq/:; it represents the metabolic (renal) component of acid-base balance.
Rationale: Bicarbonate (HCO₃) is a base regulated by the kidneys and helps buffer excess acids. It compensates for respiratory disturbances.
Why does cyanosis appear during hypoxia and what does it indicate?
It's a sign of severely low oxygen saturation and occurs when over 5g/dL of unoxygenated hemoglobin circulates.
Rationale:
Cyanosis reflects advanced hypoxia and is medical emergency in most cases.
Why is important to elevate the HOB with a chest tube in place?
Improves lung expansion and promotes drainage.
Rationale:
Upright positioning enhances ventilation, reduces pleural pressure, and facilitates gravity drainage of air/fluid.
What is the normal range for ejection fraction and what does it tell us?
What is the normal range for ejection fraction and what does it tell us?
50-70%; it indicates how well the heart pumps blood.
Rationale: Lower EF (< 40%) indicates systolic heart failure. EF is key diagnosing and managing cardiac conditions.
A COPD patient becomes lethargic after their oxygen flow rate was increased from 2 L to 6 L. What's happening?
Oxygen-induced hypoventilation due to less of hypoxic drive.
Rationale:
COPD patients rely on low O₂ levels to stimulate breathing (hypoxic drive). Too much oxygen suppresses this, leading to CO₂ retention and respiratory acidosis.
Name one condition that impairs perfusion.
Heart failure
Rationale: Perfusion requires adequate cardiac output. In heart failure, reduced pumping impairs blood flow to lungs and tissues, reduces oxygen delivery.
Describe how a partial rebreather mask functions and when it's used.
It allows rebreathing of some exhaled air and delivers ≈ 60-75% FiO₂ without full rebreather complexity.
Interpret this ABG: pH 7.25, PaCO₂ 55, HCO₃ 24. What's this condition?
Uncompensated respiratory acidosis
Rationale: Low pH = acidosis. High PaCO₂ = respiratory cause. Normal HCO₃ = no metabolic compensation yet.
Differentiate between hypoxemia and hypoxia using clinical examples
Hypoxemia ↓ O₂ in blood (e.g., COPD, pnuemonia)
Hypoxia ↓ O₂ at tissue level (e.g., shock, anemia)
Rationale:
Hypoxemia can lead to hypoxia, but you can have hypoxia without hypoxemia (e.g., if hemoglobin is low or circulation is poor).
Describe two signs of a tension pneumothorax and why they are dangerous.
Tracheal deviation & hypotension
Rationale:
Air builds in pleural space and compresses lung, shifting mediastinum, decreasing venous return and cardiac output. Life-threatening.
What is the formula for cardiac output and what variable influence it?
CO = Stroke Volume x Heart Rate
Rationale:
Low SV (due to blood loss or MI) or bradycardia → ↓CO
High HR (tachycardia) can also lower CO by reducing ventricular filling time.
Your intubated patient suddenly has diminished lung sounds on the left side. What might this indicate and what's your priority action?
Right mainstem intubation—pull back the ET slightly and notify the provider.
Rationale:
ET tubes can shift into the right bronchus, causing left lung collapse. Immediate correction is needed to prevent hypoxia.
Explain how surfactant reduces alveolar surface tensions and prevents atelectasis.
Surfactant lowers surface tensions in the alveoli, preventing collapse and allowing for better gas exchange.
Rationale: Without surfactant (especially in premature infants), alveoli may collapse (atelectasis), severely impairing ventilation.
Which device delivers nearly 100% oxygen in emergency setting, and why is it the best option?
Non-rebreather mask
Rationale:
It has a reservoir bag and one-way valves to prevent room air entry and exhaled gas rebreathing. Used for critically hypoxic patients.
Confusion, lethargy, and shallow respirations.
Rationale:
CO₂ buildup causes cerebral vasodilation, leading to mental status changes. Shallow breathing worsens CO₂ retention, worsening acidosis
Name and explain 2 physical exam findings that indicate chronic hypoxia in long-term respiratory patients.
Clubbing of fingers and barrel chest
Rationale:
Clubbing results from prolonged O₂ deprivation. Barrel chest occurs in COPD due to overinflated alveoli over time.
What are the methods used to confirm lung re-expansion after chest tube placement?
Chest X-ray and assessment of breath sounds.
Rationale: Imaging confirms absence of air/fluid in pleural space. Return of clear, bilateral breath sounds also indicates resolution.
Interpret this rhythm: normal P wave, prolonged PR interval, and wide QRS complex.
What does this suggest?
First-degree AV block with possible bundle branch block
Rationale:
PR > 0.20 sec = 1st degree block
Wide QRS = delayed conduction in ventricles
May occur with ischemia, medications (like digoxin), or electrolyte imbalances
A patient's oxygen saturation drops 85% despite being high-flow oxygen. What is your priority actions and rationale?
Assess for underlying causes like pneumothorax or pulmonary embolism and notify the provider immediately.
Rationale:
Persistent hypoxia on high oxygen is red flag for critical conditions that require for critical conditions that require urgent interventions (e.g., PE, ARDS, tension pneumothorax). Do not delay escalation.