Respiratory failure, ventilation and systemic critical illness
Airway and gas exchange
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.
Critical infection and organ dysfunction
Systemic critical illness requires recognition of organ dysfunction, cause, physiological instability and the trajectory under treatment. Sepsis is not defined as fever alone, and the absence of a dramatic temperature does not exclude it. The Sepsis-3 framework links infection to life-threatening organ dysfunction through a dysregulated host response. A qSOFA component question tests a named bedside tool; qSOFA alone must not be treated as the definitive diagnosis, a rule-out test or the only screening strategy.
Infection management includes timely appropriate sampling, antimicrobial therapy when indicated and source control. Timing and spectrum depend on the actual likelihood, shock, source, host and local resistance information. An organism name does not automatically establish every susceptibility or authorize a fixed combination. De-escalation considers microbiology, clinical response, source control and duration evidence. A biomarker may inform an assessed decision but should not be used as an isolated automatic stop rule. Routine antibiotics for sterile pancreatitis or unnecessary treatment of colonization can create harms without the intended benefit.
Prevention in intensive care includes hand hygiene, appropriate device use, aseptic processes, oral hygiene, ventilation and sedation practices and early review of device need. A bundle needs current evidence and eligible conditions; an old list is not automatically valid because all its components were once common. Routine chlorhexidine oral care solely to prevent ventilator-associated pneumonia is not recommended in the reviewed prevention framework. A positive respiratory culture does not independently establish pneumonia, and a fever does not prove that the central line is the source.
Toxicology connects exposure, mechanism, clinical pattern and available treatment. In carbon monoxide exposure, a conventional two-wavelength pulse oximeter can appear reassuring despite impaired oxygen carriage. Safe rescue and appropriate clinical assessment matter; a normal displayed saturation does not settle the concern. In acetaminophen toxicity, glutathione-related metabolism explains the role of the specific antidote, but the actual treatment decision depends on exposure timing, laboratory assessment and the relevant toxicology pathway. Do not turn a mechanism question into a universal dose or home treatment instruction.