12-phase flow (12)

1. 1FRAME
   THE PIVOT — classify aspiration PNEUMONITIS (chemical/Mendelson: abrupt onset hours after a witnessed acid/gastric event, infiltrate evolving and improving, fever early and resolving, RESPONDS WITHOUT ANTIBIOTICS in 24-48 h; severe acid load → ARDS) vs aspiration PNEUMONIA (bacterial: subacute >24-48 h, persistent/late fever + leukocytosis, fixed dependent-segment infiltrate, REQUIRES ANTIBIOTICS) (Marik NEJM 2001 PMID 11228282; Mandell & Niederman NEJM 2019 PMID 30763196)
   inputs: symptom_onset_relative_to_event
   advance: Pneumonitis-vs-pneumonia working classification assigned with timing/fever-curve rationale
2. 2ENTRY
   Triggered by witnessed aspiration/choking, dependent-segment infiltrate (RLL, posterior segments, RUL-posterior if supine), or sepsis in a high-aspiration-risk substrate patient (Mandell 2019 PMID 30763196)
   inputs: age
   advance: Aspiration risk substrate or imaging finding present
3. 3CONTEXT
   Capture risk substrate (dysphagia, stroke, dementia, ALS, intoxication/overdose, NG/PEG tube, recent extubation/peri-procedural, GERD/achalasia), oral health (severe periodontal disease — now the key anaerobic-coverage trigger), prior antibiotics, recent hospitalisation (≥48 h → hospital-acquired pattern)
   inputs: spo2, temp, rr, sbp, aspiration_event, dysphagia_or_altered_los, periodontal_disease_or_abscess, recent_hospitalization
   advance: Substrate, oral health, hospital-acquired status, and severity captured
4. 4RED_FLAGS
   Severe sepsis/septic shock, hypoxemic respiratory failure, ARDS from massive acid aspiration (Mendelson), lung abscess, empyema, large-volume vomiting with ongoing aspiration risk, foreign-body aspiration with airway obstruction
   inputs: spo2, sbp
   actions: calc.qsofa
   advance: No emergent escalation needed OR sepsis bundle / airway protection initiated
5. 5INITIAL_WORKUP
   CXR (dependent-segment pattern — RLL/posterior segments upright, RUL-posterior/superior-RLL supine); blood cultures + sputum Gram stain/culture if pneumonia suspected; lactate, CBC, creatinine. KEY: an evolving/improving infiltrate that clears in 24-48 h with NO new fever supports pneumonitis (observe, no abx); a fixed/progressing infiltrate with persistent fever supports bacterial pneumonia (Marik 2001 PMID 11228282; Mandell 2019 PMID 30763196)
   inputs: cxr, wbc, creatinine, lactate
   actions: aspiration_pneumonia
   advance: Imaging + cultures obtained and pneumonitis-vs-pneumonia trajectory clarified
6. 6BRANCHING_WORKUP
   CT chest if poor response at 48-72 h or abscess/necrotizing/empyema concern (cavitation, air-fluid level, loculated pleural collection); bronchoscopy if foreign-body aspiration or post-obstructive pneumonia (rule out endobronchial malignancy in non-resolving); modified barium swallow / FEES once acute illness settles
   inputs: ct_chest
   advance: Complications and mimics excluded or characterised
7. 7DIFFERENTIAL
   Aspiration pneumonitis vs aspiration pneumonia (THE pivot) vs CAP (no aspiration substrate) vs HAP/VAP (≥48 h hospitalised → pulm.hospital-acquired-pneumonia-non-covid.v1) vs ARDS (Mendelson can cause it → pulm.ards.core.v1) vs PE (pleuritic, hypoxia disproportionate to infiltrate → pulm.pe.core.v1) vs lung abscess/empyema vs sepsis from another source (id.sepsis.core.v1)
   advance: Working diagnosis identified with discriminators documented
8. 8RISK_STRATIFICATION
   CURB-65 / PSI for severity + disposition; decide anaerobic-coverage (ONLY if lung abscess, empyema, necrotizing pneumonia, or severe periodontal disease with putrid sputum — NOT routine, per Metlay ATS/IDSA 2019 PMID 31573350); decide community vs hospital-acquired empiric spectrum
   actions: calc.curb65
   advance: Severity score + anaerobic-coverage decision + community-vs-hospital spectrum documented
9. 9TREATMENT
   PNEUMONITIS (chemical, witnessed event, infiltrate clearing, no late fever/leukocytosis) → SUPPORTIVE ONLY, withhold/stop antibiotics, reassess 48 h. PNEUMONIA → empiric antibiotics targeting oral aerobes / S. aureus / enteric Gram-negatives (community: ampicillin-sulbactam or amoxicillin-clavulanate; hospital-acquired/severe: pip-tazo ± MRSA) WITHOUT routine added anaerobic agent — add metronidazole/clindamycin ONLY for abscess/empyema/necrotizing/severe periodontal disease (Metlay 2019 PMID 31573350; Mandell 2019 PMID 30763196). Renal/hepatic dose adjust; speech-swallow consult + NPO until assessed
   inputs: creatinine
   actions: calc.ckd_epi_2021
   advance: Treat-vs-observe decision made; if treating, antibiotic + duration + anaerobic decision + dysphagia consult documented
10. 10DISPOSITION
    Pneumonitis improving → home with swallow follow-up; mild community pneumonia CURB-65 0-1 → outpatient; CURB-65 2 / hypoxia → ward; CURB-65 ≥3 / septic shock / hypoxemic respiratory failure / ARDS → ICU
    advance: Disposition decided
11. 11MONITORING
    Clinical response at 48-72 h (de-escalate / stop antibiotics if pneumonitis confirmed by resolution); repeat imaging only if non-resolving (then CT for abscess/empyema); swallow re-evaluation pre-discharge
    advance: Response trend documented; antibiotics stopped if pneumonitis, narrowed if pneumonia; aspiration-prevention plan in place
12. 12FOLLOWUP
    Secondary prevention bundle — speech-language pathology swallow rehab, diet/texture modification, oral-hygiene programme, head-of-bed elevation, sedative/anticholinergic deprescribing, vaccination, goals-of-care discussion for recurrent aspiration (PEG does NOT eliminate aspiration risk) (Mandell 2019 PMID 30763196; Sherman/Martino JAHA 2021 PMID 34096328)
    advance: Aspiration-prevention + secondary-prevention bundle in place