Airway assessment, respiratory mechanics and ventilation
Airway and ventilation reasoning begins with oxygenation, ventilation, protection, anatomy, urgency and available expertise. A predicted difficult laryngoscopy is not identical to an inability to oxygenate. Assessment combines history, examination, prior airway information, patient condition and the proposed procedure. A reassuring individual measurement does not guarantee easy management, and an adverse measurement does not independently establish one mandatory technique. A difficult-airway plan includes limits, alternatives, communication and rescue capability rather than repeated identical attempts.
Respiratory mechanics separates resistance, compliance, applied pressure and patient effort. During an appropriate inspiratory hold in a passive patient, plateau pressure differs from peak pressure because flow has ceased. A rise in peak pressure with a relatively unchanged plateau can suggest increased resistance, while a rise in plateau suggests a different problem involving compliance, volume or pressure relationships. Driving pressure is interpreted using the actual plateau and PEEP measurement conditions. An association with outcome does not turn one numerical value into an independently proven universal treatment target.
ARDS assessment considers timing, opacities, explanation of edema and oxygenation under the specified framework. A Berlin category is not established from the oxygen ratio alone if the other defining elements are absent. Protective ventilation uses predicted rather than actual body weight for the relevant tidal-volume approach. The actual mode, plateau, effort, gas exchange and circulation require reassessment. Proning and neuromuscular blockade are selected strategies with eligibility, expertise and risks; they are not automatically indicated for every abnormal chest radiograph.
Obstructive disease can generate dynamic hyperinflation when expiration is incomplete. Examine expiratory flow, timing and patient-ventilator interaction rather than increasing rate indiscriminately. Intrinsic PEEP measurement requires suitable conditions, and a maneuver in an actively breathing patient can be misleading. Noninvasive support requires an appropriate airway, cooperation, monitoring and a plan for failure. A patient in arrest or with an unprotected airway is not made suitable simply because a mask is available. Device settings must follow the actual clinical assessment rather than a universal recipe from a vignette.
Liberation from ventilation considers the underlying disease, circulation, alertness, strength, secretions, cough and airway patency. A spontaneous breathing trial and a calculated rapid-shallow-breathing index provide information but do not independently guarantee safe extubation. A cuff-leak result is also not infallible. High-flow oxygen can support oxygenation and reduce anatomical dead-space effects in selected settings, but oxygen delivery during apnea is not the same as adequate carbon dioxide elimination. Treat actual deterioration promptly and distinguish an index calculation from a complete decision to continue, escalate or withdraw support.