Browse categories and answer follow-up questions to refine your symptom profile.
History
Exposure context
Carbon monoxide exposure context
Location type
Home
Garage
Workplace
Vehicle
Fire or smoke exposure
Exposure scenario
Enclosed space
Multiple people symptomatic
Pets symptomatic
Recent use
Furnace or boiler
Space heater
Generator
Grill or charcoal
Fireplace
Gas stove or oven
Timeline
Time of last known well
Estimated duration of exposure
Time since removal from source
Prehospital care
Oxygen given
Time on oxygen before labs
Symptom characterization
Symptom profile
Associated symptoms
Headache
Dizziness
Nausea
Vomiting
Weakness
Chest pain
Dyspnea
Confusion
Syncope
Seizure
Symptom trajectory
Improving after fresh air or oxygen
Persistent despite oxygen
Functional impact
Unable to ambulate normally
Unable to maintain oral intake
OPQRST if prominent symptom
OPQRST for dominant symptom
Onset
Sudden
Gradual
Time of onset relative to exposure
Provocation or palliation
Worse in enclosed space
Better outdoors
Better with oxygen
Quality
Pressure
Throbbing
Shortness of breath sensation
Region or radiation
Frontal
Diffuse
Chest radiation
Severity
Mild
Moderate
Severe
Timing
Constant
Intermittent
Recurrent with re exposure
Alarm Features
Immediate life threats
Critical features
Airway compromise
Inability to protect airway
Recurrent vomiting with somnolence
Respiratory failure
SpO2 low on high flow oxygen
Severe work of breathing
Neurologic emergency
Seizure
Coma
Focal neurologic deficit
Cardiovascular emergency
Chest pain concerning for ischemia
Dysrhythmia
Shock
High risk thresholds
Escalation thresholds
Systolic blood pressure less than 90 mmHg
Escalate to resuscitation bay
Vasopressor consideration after fluids
Respiratory rate greater than 30
Noninvasive ventilation consideration
Early intubation consideration
GCS less than 13
Immediate airway readiness
Immediate hyperbaric consultation consideration
Persistent altered mental status
Continuous monitoring
Broaden differential and co ingestion workup
Medications
Current and recent agents
Medication reconciliation focus
Cardioactive medications
Beta blockers
Calcium channel blockers
Antiarrhythmics
Sedatives and opioids
Benzodiazepines
Opioids
Glucose lowering agents
Insulin
Sulfonylureas
Anticoagulants and antiplatelets
DOACs
Warfarin
Aspirin
Recent changes
Dose increase
Missed doses
Treatment relevant contraindications
Oxygen therapy considerations
Severe COPD with chronic hypercapnia
Titrate oxygen with ABG or VBG monitoring
Ventilatory support thresholds
Pregnancy status
Lower threshold for hyperbaric consultation
Fetal monitoring coordination
Seizure history
Hyperbaric seizure risk awareness
Antiseizure medication adherence
Diet
Recent intake and exposures
Intake and exposure patterns
Hydration status indicators
Poor oral intake
Vomiting limiting intake
Alcohol exposure
Recent ethanol intake
Risk of co intoxication
Caffeine and energy drinks
High caffeine intake
Palpitations confounders
Carbon monoxide relevant environment
Recent indoor cooking or heating
Use of charcoal indoors
Review of Systems
System symptom screen
ROS clusters
General
Fatigue
Malaise
Fever
Neurologic
Headache
Confusion
Dizziness
Visual changes
Syncope
Seizure
Cardiopulmonary
Chest pain
Dyspnea
Palpitations
Gastrointestinal
Nausea
Vomiting
Abdominal pain
ENT
Sore throat after smoke
Hoarseness
Dermatologic
Burns or soot exposure
Cyanosis
Collateral History and Family History
Collateral and scene information
Collateral sources
EMS report
Scene description
Other symptomatic occupants
Fire department
CO detector readings if available
Environmental remediation status
Family or roommates
Shared symptom pattern
Timing of symptom onset
Family history relevant to risk
Family history considerations
Early coronary artery disease
First degree relative under 55 male
First degree relative under 65 female
Hemoglobinopathies
Sickle cell disease
Thalassemia
Inherited arrhythmia syndromes
Long QT syndrome
Brugada syndrome
Risk Factors
Exposure and environmental risks
Exposure risk factors
Enclosed space exposure
Poor ventilation
Sleeping during exposure
Faulty combustion sources
Furnace or boiler malfunction
Generator indoors
Vehicle running in garage
Fire and smoke exposure
Structural fire
Wildfire smoke in enclosed space
Patient factors increasing harm
High risk populations
Pregnancy
Increased fetal susceptibility
Lower threshold for hyperbaric consultation
Infants and children
Higher minute ventilation
Nonspecific symptom presentation
Older adults
Higher cardiac risk
Baseline cognitive vulnerability
Coronary artery disease (I25.10)
Lower ischemia threshold
Higher risk dysrhythmia
Anemia (D64.9)
Reduced oxygen carrying capacity
More severe symptoms at lower COHb
Differential Diagnosis
Life threatening
Life threatening causes
Carbon monoxide poisoning (T58.91XA)
Multiple occupants symptomatic
Improvement with oxygen
Cyanide toxicity
Fire in enclosed space
Severe lactic acidosis
Acute coronary syndrome (I21.9)
Chest pain
ECG ischemia
Stroke or TIA (I63.9)
Focal deficits
Persistent neurologic symptoms
Severe hypoglycemia (E16.2)
Diaphoresis
Altered mental status
Toxic co ingestion
Sedative toxidrome
Opioid toxidrome
Common
Common alternatives
Viral syndrome
Fever
Myalgias
Migraine
Photophobia
Prior migraine history
Gastroenteritis
Diarrhea
Sick contacts
Anxiety or panic symptoms
Hyperventilation
Paresthesias
Less common
Less common and mimics
Methemoglobinemia
Low SpO2 with normal PaO2
Oxidant exposure
Carbon dioxide exposure
Confined space
Headache with hypercapnia
Meningitis or encephalitis (G00.9)
Neck stiffness
Persistent altered mental status
Thyrotoxicosis (E05.90)
Tremor
Heat intolerance
Past Medical History
Relevant conditions and baseline
Baseline risks and prior events
Prior carbon monoxide exposure
Prior hyperbaric treatment
Delayed neuropsychiatric symptoms history
Cardiopulmonary disease
Coronary artery disease (I25.10)
Heart failure (I50.9)
COPD (J44.9)
Asthma (J45.909)
Neurologic disorders
Seizure disorder (G40.909)
Stroke history (I63.9)
Hematologic conditions
Anemia (D64.9)
Sickle cell disease (D57.1)
Pregnancy and pediatric specifics
Special populations baseline
Pregnancy status
Gestational age
Obstetric complications
Pediatrics
Developmental baseline
Baseline feeding pattern
Physical Exam
Vitals and general appearance
Immediate exam targets
Vitals trends
Temperature
Heart rate
Blood pressure
Respiratory rate
SpO2 on room air and on oxygen
General appearance
Toxic appearance
Diaphoresis
Altered level of consciousness
Perfusion
Capillary refill
Skin temperature
Peripheral pulses
Neurologic and cardiopulmonary
System focused findings
Neurologic
GCS
Orientation
Cranial nerves
Motor strength
Sensation
Coordination
Gait if safe
Cardiovascular
Heart sounds
Murmur
Signs of heart failure
JVP elevation
Peripheral edema
Crackles
Respiratory
Work of breathing
Wheeze
Crackles
Soot in nares or oropharynx
Skin
Burns
Soot contamination
Lab Studies
Core labs and interpretation
Key laboratory tests
Carboxyhemoglobin level
Venous acceptable for COHb trending
Interpret with time on oxygen
Blood gas
ABG or VBG
PaO2 in mmHg
pH
Lactate in mmol/L
Basic metabolic panel
Sodium in mmol/L
Potassium in mmol/L
Creatinine
Glucose
CBC
Hemoglobin
Leukocytosis context
Troponin
Chest pain
Abnormal ECG
Older adults
CK
Prolonged immobilization concern
Seizure concern
Pitfalls and limitations
Common interpretation pitfalls
SpO2 limitation
Pulse oximetry may read falsely normal
Does not measure COHb
COHb level limitations
Lower after oxygen therapy
Symptoms may not correlate with COHb
Lactate interpretation
High lactate suggests severe hypoxia
Very high lactate in fire suggests cyanide co toxicity
Imaging
Scoring Systems
Severity and pathway tools
Hyperbaric referral triggers local protocol dependent
Loss of consciousness
Persistent neurologic symptoms
Severe metabolic acidosis
Pregnancy with elevated COHb
Fire exposure adjunct risk assessment
Soot in airway
Facial burns
Hoarseness or stridor
MRI
Neuro imaging considerations
MRI brain for delayed neuropsychiatric syndrome concern
Cognitive change days to weeks after exposure
Movement disorder symptoms
MRI limitations
Not required for typical acute management
Timing dependent findings
CT
CT indications
CT head
Persistent altered mental status not explained by CO alone
Focal neurologic deficit
Trauma after syncope
CT chest
Inhalation injury complications concern
Alternative diagnosis concern
Ultrasound
POCUS applications
Cardiac POCUS
Global function
Pericardial effusion
Lung POCUS
Pulmonary edema
Alternative diagnosis support
Special Tests
Bedside and confirmatory testing
Diagnostic tests beyond routine labs
Co oximetry
Measures COHb and methemoglobin
Prefer arterial or venous blood over pulse oximetry
Continuous cardiac monitoring
Dysrhythmia detection
Ischemia surveillance
Neurocognitive screening
Short memory and attention screen if stable
Baseline for follow up
Hyperbaric oxygen coordination tests
Pre transfer requirements local protocol dependent
Pregnancy testing when applicable
Urine or serum testing
Gestational age documentation
Fire exposure screening
Lactate in mmol/L
Consider cyanide evaluation pathway
ECG
Indications and high risk findings
ECG use
Indications
Chest pain
Dyspnea
Syncope
Older adults
Known coronary disease
High risk patterns
ST elevation
ST depression
T wave inversion new
Ventricular dysrhythmia
QT prolongation
Serial ECG and biomarkers
Monitoring strategy
Serial ECG timing
Repeat with symptom change
Repeat with abnormal initial ECG
Troponin strategy
Serial per local ACS pathway
Higher concern with CO exposure plus ischemic symptoms
Assessment
Working diagnosis and severity
Carbon monoxide poisoning assessment
Working diagnosis
Suspected carbon monoxide poisoning (T58.91XA)
Confirmed by elevated COHb
Severity stratification
Mild symptoms with normal mentation
Neurologic involvement
Cardiac involvement
Severe acidosis
Complications to rule out
Myocardial ischemia
Dysrhythmia
Inhalation injury
Cyanide co toxicity with fire exposure
Diagnostic uncertainty
Alternative diagnoses
Persistent symptoms despite low COHb after oxygen
Consider alternate causes of headache
Consider infection
No clear exposure source
Consider medical mimics
Consider environmental assessment needs
Plan
First 5 minutes
Immediate stabilization workflow
Monitoring
Continuous pulse oximetry
Continuous cardiac monitoring
Frequent blood pressure cycling
Oxygen
High flow oxygen via nonrebreather
Target SpO2 94 to 98
IV access
One large bore IV for stable
Two large bore IV for unstable
Point of care tests
Fingerstick glucose
ECG if chest pain or syncope
Escalation triggers
GCS less than 13
Seizure
Shock
Respiratory failure
Therapeutics
Treatment priorities
Normobaric oxygen
100 percent oxygen until symptoms resolve
Continue until COHb normalizing with clinical improvement
Hyperbaric oxygen consultation local protocol dependent
Loss of consciousness
Persistent neurologic symptoms
Ischemic ECG changes or elevated troponin
Severe acidosis
Pregnancy with elevated COHb or symptoms
Fluids
Isotonic crystalloid bolus for hypotension
Reassess perfusion after bolus
Antiemetic example adult dosing
Ondansetron ODT or IV 4 mg
Repeat 4 mg once if needed
Seizure treatment example adult dosing
Lorazepam IV 2 mg
Repeat every 2 to 3 minutes to maximum 8 mg
Cyanide antidote pathway fire exposure local protocol dependent
Consider hydroxocobalamin when severe lactic acidosis plus fire exposure
Coordinate with toxicology
Reassessment loop
Reassessment cadence
Neuro status
Repeat mental status every 30 to 60 minutes
Repeat gait when safe
Symptom response
Headache trajectory on oxygen
Nausea control
Objective monitoring
Repeat COHb per clinical course
Repeat ECG and troponin when indicated
Disposition pivot triggers
New neurologic deficit
Rising troponin
Persistent symptoms after several hours of oxygen
Disposition
Level of care criteria
ICU or high acuity criteria
Airway or ventilation support required
Intubation
Noninvasive ventilation
Hemodynamic instability
Vasopressor requirement
Persistent hypotension
Severe neurologic toxicity
Coma
Recurrent seizures
Cardiac complications
Ongoing ischemia
Malignant dysrhythmia
Admission and discharge criteria
Inpatient or observation criteria
Persistent symptoms despite oxygen
Headache not improving
Ongoing nausea or vomiting
Abnormal investigations
Elevated troponin
Significant acidosis
Social reliability concerns
Unsafe return environment
No reliable supervision
Discharge criteria
Clinical stability
Normal mentation at baseline
Symptoms resolved or minimal and improving
Safe environment confirmed
Source addressed by qualified services
Functional CO alarms present
Follow up arranged
Primary care within 24 to 72 hours
Neuro follow up if symptoms occurred
Discharge Instructions
Copy discharge instructions
Discharge text
Diagnosis summary
You were treated for possible carbon monoxide exposure
Carbon monoxide can cause headache, dizziness, nausea, confusion, and chest pain
Home safety
Do not return to the exposure location until it is cleared safe by qualified services
Ensure working carbon monoxide alarms are installed
Medications
Use your usual medications as prescribed
If nausea returns, use prescribed anti nausea medication as directed
Activity
Rest today
Avoid driving if you feel dizzy or foggy
Follow up
Primary care follow up in 1 to 3 days
If you had confusion or fainting, discuss neuro follow up
Return to ED now for
Fainting
New confusion
Seizure
Chest pain
Shortness of breath
Worsening headache
Persistent vomiting
New weakness or numbness
Symptoms after returning to the same building
References
Guidelines and key sources
Evidence based references
Undersea and Hyperbaric Medical Society
Hyperbaric oxygen indications for carbon monoxide poisoning
Local protocol dependent thresholds
CDC
Clinical guidance for carbon monoxide poisoning
Prevention and public health recommendations
American Heart Association
Carbon monoxide and cardiovascular effects
Ischemia risk considerations
Goldfrank Toxicologic Emergencies
Carbon monoxide poisoning management
Cyanide co toxicity considerations in fire
Project instructions source
Formatting requirements
Structure requirements
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.