Pressure Alarms and Airway Mechanics
: A patient in Assist-Control suddenly triggers a high-pressure alarm; peak inspiratory pressure rises from 22 to 38 cm H₂O, with diminished breath sounds on the right.
What is a right mainstem intubation or right pneumothorax causing an airway resistance/compliance problem (vs. a diffuse compliance problem, which would raise plateau pressure too)?
A rising PEAK pressure with a normal or unchanged plateau pressure points to a resistance problem (kinked tube, secretions, bronchospasm, mainstem migration) rather than a compliance problem (pneumothorax, ARDS, abdominal distension), which raises both peak and plateau pressure together. Unilateral diminished sounds narrow this to tube migration or pneumothorax — both require immediate priority assessment, since pneumothorax can progress to tension physiology within minutes.
ABG on a ventilated patient: pH 7.29, PaCO₂ 55, HCO₃ 26, PaO₂ 78.
What is acute (uncompensated/minimally compensated) respiratory acidosis with mild hypoxemia, indicating inadequate minute ventilation on current settings?
High tidal volumes in ARDS versus a lung-protective strategy
What is the trade-off between larger breaths that may transiently improve CO₂ clearance and comfort, against the well-documented risk of volutrauma/barotrauma and worsened mortality from overdistending already-injured alveoli?
A patient becomes bradycardic during endotracheal suctioning
What is a vagal response triggered by airway stimulation, compounded by suction-induced hypoxemia from removed oxygen along with secretions?
ABG 30 minutes into a spontaneous breathing trial: pH 7.33, PaCO₂ 50, PaO₂ 70, HCO₃ 25.
What is a borderline result requiring correlation with the whole clinical picture — mild respiratory acidosis and a low-normal PaO₂ could reflect acceptable, tolerable compensation in a comfortable patient, or early decompensation in one who is tachypneic and struggling?
A low-pressure alarm sounds; the tubing is intact, but SpO₂ drops to 88%.
What is a cuff leak (or a smaller disconnection elsewhere in the circuit) allowing loss of set tidal volume?
ABG during a weaning trial: pH 7.48, PaCO₂ 30, HCO₃ 24, PaO₂ 92.
What is respiratory alkalosis that could reflect either an anxious/tachypneic patient over-breathing the vent (favorable oxygenation, but not necessarily readiness) or early compensation that still needs correlation with clinical signs before proceeding?
A patient with acute pulmonary edema is placed on BiPAP.
What is the use of positive pressure to reduce preload and afterload, redistribute alveolar fluid, and improve oxygenation without the risks of intubation — escalating to intubation if mental status declines, the patient can’t protect the airway, or work of breathing/gas exchange fails to improve?
A patient on Pressure Support shows decreasing spontaneous tidal volumes
What is respiratory muscle fatigue (inadequate support for the work of breathing) versus over-sedation blunting respiratory drive — distinguished by respiratory rate, sedation score, and accessory muscle use?
The clinical reasoning pathway connecting improved lung compliance, reduced FiO₂ requirements, stable ABGs, and decreased PEEP.
What is the sequence showing lung recovery: as injured alveoli heal, compliance improves → the lung requires less pressure/oxygen to achieve adequate gas exchange → PEEP and FiO₂ can be weaned while ABGs remain stable → confirming the patient can maintain gas exchange with progressively less ventilatory support, supporting a trial toward extubation?
A patient with copious secretions develops frequent high-pressure alarms
What is increased airway resistance from mucus plugging, producing V/Q mismatch (low V relative to Q in obstructed units) and eventual CO₂ retention if uncorrected?
A patient on high PEEP has improved oxygenation but declining blood pressure
What is decreased venous return/preload from increased intrathoracic pressure, reducing right ventricular filling and downstream cardiac output?
CPAP versus BiPAP
What is CPAP delivering a single continuous pressure (mainly improving oxygenation/recruitment with no inspiratory boost) versus BiPAP delivering two pressures — a higher IPAP and lower EPAP — adding real ventilatory support for CO₂ clearance and reduced work of breathing?
A patient extubated after meeting all readiness criteria develops stridor
What is post-extubation laryngeal edema/laryngospasm from cuff-related airway trauma, requiring immediate assessment and stepwise response (racemic epinephrine, humidified oxygen, escalating to reintubation if obstruction worsens)?
Evidence-based components of the VAP prevention bundle.
What are head-of-bed elevation 30–45 degrees, daily sedation vacations paired with spontaneous breathing trials, DVT and peptic ulcer prophylaxis, oral care with chlorhexidine, and subglottic secretion drainage — each targeting a specific mechanism of aspiration or stasis-related infection?
A patient becomes agitated and “fights the ventilator,” triggering repeated alarms
What is patient-ventilator dyssynchrony, arising from a mismatch between the patient’s own respiratory drive/effort and the ventilator’s set flow, timing, or sensitivity?
A COPD patient on BiPAP shows rising PaCO₂ despite increased IPAP.
What is worsening alveolar hypoventilation or increasing dead space/V̇-Q̇ mismatch that increased pressure support alone isn’t overcoming — raising concern for fatigue, mask leak, or progressing air-trapping (auto-PEEP)?
A trauma patient with structurally normal lungs requires intubation solely for airway protection
What are settings aimed at maintaining normal gas exchange and avoiding iatrogenic lung injury — standard tidal volumes (6–8 mL/kg predicted body weight), modest PEEP (often 5 cm H₂O), and FiO₂ titrated to the lowest level maintaining adequate saturation — rather than lung-protective ARDS-style settings?
Criteria to determine readiness for a spontaneous breathing trial.
What are hemodynamic stability (minimal/no vasopressor support), adequate oxygenation (PaO₂/FiO₂ ratio typically >150–200 on PEEP ≤ 5–8), appropriate mental status (arousable, able to protect airway), and acceptable ABG parameters (resolving acidosis, adequate ventilation) — all present simultaneously, not in isolation?
A decision tree for when BiPAP is appropriate versus when invasive ventilation is required.
What is a branching pathway where BiPAP is appropriate for an awake, cooperative patient who can protect their airway and clear secretions, with a correctable or rapidly reversible process (cardiogenic edema, COPD exacerbation, early hypoxemic failure) — while invasive ventilation is required for altered mental status, inability to protect the airway, copious secretions, hemodynamic instability, or failure to improve on noninvasive support?
: A ventilated patient suddenly becomes hypotensive and hypoxic with high-pressure alarms sounding
What is the DOPE/DOTTS approach — assess Displacement, Obstruction, Pneumothorax, and Equipment failure, disconnecting to manually bag on 100% oxygen if any of these cannot be immediately ruled out?
A low exhaled tidal volume alarm sounds on a volume-targeted mode.
What is a discrepancy between delivered and exhaled tidal volume caused by an air leak in the circuit (cuff, connection, chest tube with bronchopleural fistula) or a sudden drop in compliance limiting how much volume the lungs can accept?
The ventilator shows rising peak pressures together with rising PaCO₂.
What is bronchospasm, mucus plugging, or pneumothorax — each raising resistance or reducing effective ventilation, distinguished by breath sounds (wheezing vs. diminished/absent), suction return, and hemodynamic stability?
During a weaning trial, respiratory rate rises from 18 to 34, tidal volume drops, and accessory muscles are used.
What is respiratory muscle fatigue with impending failure of the trial — terminate the SBT and return to full ventilatory support rather than continuing?
A troubleshooting flowchart for high-pressure alarms, differentiating patient factors, equipment factors, and lung compliance changes.
What is a structured algorithm that first disconnects to bag if instability is present, then sequentially rules out patient factors (biting, coughing, secretions, bronchospasm, dyssynchrony), equipment factors (kinked/water-filled tubing, malfunctioning valve), and compliance changes (pneumothorax, worsening ARDS, abdominal distension) — using breath sounds, suctioning, and circuit inspection to sort between them?