Airway Management and Oxygen Therapy Flashcards

A patient under deep sedation develops partial airway obstruction. After repositioning the head and performing a jaw thrust, SpO₂ remains at 88% on 6 L/min via nasal cannula. What is the MOST appropriate next intervention?

Answer: Insert a nasopharyngeal airway and increase oxygen flow to 10–15 L/min via non-rebreather mask

When repositioning and jaw thrust fail to resolve partial obstruction in a deeply sedated patient, a nasopharyngeal airway (NPA) is the preferred adjunct because it is better tolerated than an oropharyngeal airway in semi-conscious patients and physically stents the pharynx open. Simultaneously upgrading oxygen delivery to a non-rebreather mask (10–15 L/min, FiO₂ ~0.90) maximizes oxygen reserves while the obstruction is addressed. Flumazenil reversal is a later step if mechanical maneuvers fail and opioids are not the sole agent. CPAP requires specialized equipment not typically immediately available chairside and is not a first-line rescue step. Blind nasotracheal intubation is an advanced airway reserved for failed airways.

During office-based deep sedation, a patient's end-tidal CO₂ waveform suddenly shows a sustained 'shark-fin' morphology with a plateau ETCO₂ of 58 mmHg. Breath sounds are equal bilaterally and SpO₂ is 97% on 4 L/min nasal cannula. What does this capnography pattern most likely indicate?

Answer: Bronchospasm causing expiratory flow obstruction

A 'shark-fin' or sloped upstroke on the capnography waveform—where the plateau phase rises slowly and the square wave is lost—is the hallmark of expiratory airflow obstruction, most commonly bronchospasm. The elevated ETCO₂ (58 mmHg) confirms hypoventilation due to air trapping from incomplete exhalation. Equal breath sounds rule out unilateral obstruction (e.g., mucus plug), though wheezing may be subtle or absent in severe spasm. Esophageal intubation produces absent or rapidly diminishing waveforms, not a shark-fin. Hyperventilation would produce low ETCO₂. During CPR, waveforms appear but are low amplitude and irregular.

A 62-year-old patient with severe COPD (FEV₁ 28% predicted) requires moderate sedation for an extended dental procedure. Which oxygen delivery strategy best balances adequate oxygenation against the risk of hypercapnic respiratory failure in this patient?

Answer: Titrated low-flow oxygen (1–2 L/min) with continuous capnography monitoring to target SpO₂ 88–92%

In severe COPD patients who chronically retain CO₂, supplemental oxygen should be titrated to target SpO₂ 88–92%—not the standard ≥95%—because excessive oxygen can suppress hypoxic pulmonary vasoconstriction, worsen V/Q mismatch (Haldane effect), and blunt the residual hypoxic ventilatory drive, precipitating hypercapnic respiratory failure. Low-flow titration (1–2 L/min) with capnography to detect rising CO₂ is the safest approach. Withholding all oxygen is dangerous and incorrect—the risk of acute hypoxia far exceeds the concern about eliminating hypoxic drive entirely. High-flow or non-rebreather delivery creates uncontrolled high FiO₂ and is specifically contraindicated in hypercapnic COPD.

Following intravenous midazolam and fentanyl for deep sedation, a patient develops laryngospasm. After 30 seconds of firm positive pressure ventilation with 100% oxygen via bag-valve-mask, the spasm has not broken. What is the CORRECT pharmacological intervention at this point?

Answer: Succinylcholine 0.1–0.2 mg/kg IV (subparalytic 'laryngospasm dose')

Complete laryngospasm unresponsive to positive pressure ventilation requires pharmacologic relaxation of the false vocal cords. Succinylcholine at 0.1–0.2 mg/kg IV (approximately 10–20 mg in an adult) is the 'laryngospasm dose'—a subparalytic amount sufficient to relax the spasm without causing full apnea, preserving some spontaneous ventilation. If IV access is unavailable, IM succinylcholine at 4 mg/kg is an alternative. Flumazenil reverses sedation but does not directly relax laryngeal muscles; flumazenil would not break an established spasm and opioids also contribute. Atropine addresses secretions, not vocal cord spasm. Epinephrine is indicated for anaphylaxis/bronchospasm, not true laryngospasm.

A nasal cannula is being used to deliver oxygen to a sedated patient. At a flow rate of 6 L/min, which statement most accurately describes the FiO₂ being delivered?

Answer: Approximately 0.44, assuming a normal tidal volume and respiratory rate

With a nasal cannula, the delivered FiO₂ is variable and depends heavily on the patient's tidal volume, inspiratory flow rate, and respiratory rate. The commonly used rule of thumb is that each 1 L/min adds approximately 0.04 (4%) to room air FiO₂ (0.21), so 6 L/min ≈ 0.21 + (6 × 0.04) = 0.45, or approximately 0.44–0.46. This estimate assumes normal tidal volume (~500 mL) and respiratory rate. The FiO₂ is NOT fixed or exact—it rises with lower tidal volumes and slower rates (more entrainment time) and falls with higher minute ventilation. The nasopharynx does serve as a small anatomic reservoir (~50 mL), which is factored into the standard estimate.

During recovery from IV sedation, a patient is placed supine. The pulse oximeter reads 91% despite 4 L/min nasal cannula oxygen. The patient is snoring loudly but responds to verbal stimulation. Repositioning to lateral decubitus and applying a chin lift transiently improves SpO₂ to 94%, but it drops again when the assistant's hand is removed. Which airway adjunct is MOST appropriate for this scenario, and why?

Answer: Nasopharyngeal airway (NPA), because it is better tolerated in semi-conscious patients and provides continuous pharyngeal patency

The patient is semi-conscious (responds to verbal stimuli) with positional upper airway obstruction causing desaturation that cannot be maintained manually. An NPA is specifically indicated here: it physically stents the pharyngeal airway open without requiring the patient to be fully unconscious, and it is much better tolerated than an OPA in patients who retain any gag reflex or response to stimulation. The OPA would likely trigger gagging, vomiting, or laryngospasm in this partially conscious patient. An LMA or ETT is premature—this is a partially obstructed airway amenable to a simple adjunct, not a failed airway. SpO₂ of 91% with a correctable cause does not meet criteria for emergent intubation.