Fire smoke and bad air: who decompensates first

For four days the city has woken up to an orange sky because of forest fires hundreds of kilometers away. In the outpatient clinic, a teenager with asthma says she has needed her rescue inhaler several times a day. In the emergency department, a sixty-eight-year-old man with COPD arrives short of breath and says "it's the smoke". Next to him, a woman thirty-two weeks pregnant asks whether she should leave home to go to work. Later, a fifty-five-year-old male smoker seeks care for chest tightness and cough, and someone writes on the chart "smoke irritation". The scenes are fictional and were written for teaching. This text uses these frames as a setting for clinical reasoning: how to think about the risk of people exposed to smoke, how to adjust care before decompensation and how to keep the context from hiding another diagnosis.

NEXO is a daily medical diagnosis game: one clinical case a day, up to six progressive clues, and ICD-10 proximity feedback across five levels.

The text avoids being a protocol. Medications, doses and admission criteria follow each service's protocols, under supervision. The focus is on how to think: who is more likely to worsen, what to ask, when to reassess and which shortcuts lead to error. If you play the case of the day on NEXO, you will recognize the move: a contextual clue changes the weight of the others, but does not decide the case on its own.

Key points

• Forest fire smoke is consistently associated with asthma and COPD exacerbations, and there is growing evidence of association with respiratory infections and all-cause mortality.
• The evidence for cardiovascular effects is more mixed, but some studies show an increase in out-of-hospital cardiac arrest on days with more fine particles.
• Children, pregnant women, older adults and people with respiratory or cardiac disease form the group that deserves active contact before worsening.
• Care includes reviewing the written action plan for asthma or COPD crises, reducing exposure at home and using air quality indices to plan the day.
• The most dangerous context bias is attributing all chest pain or shortness of breath to the smoke and missing a myocardial infarction, a pulmonary embolism or a pneumonia.

What smoke changes in clinical reasoning

Fire smoke is a mixture of gases and particles, and fine particles, called PM2.5, are the most concerning because they reach the depths of the lungs. The critical review by Reid and colleagues gathered the studies on the effects of exposure to forest fire smoke and found consistent evidence of respiratory worsening, especially asthma and COPD exacerbations, growing evidence for respiratory infections and all-cause mortality, and mixed results for cardiovascular outcomes (Reid and colleagues, 2016). The systematic review by Liu and colleagues reached similar conclusions about respiratory effects (Liu and colleagues, 2015).

For those providing care, this means two things. In weeks of smoke, the pretest probability of respiratory exacerbation rises, and services must be prepared for more asthma and COPD cases. At the same time, smoke does not protect anyone from the other causes of shortness of breath and chest pain, which keep occurring at the same frequency or even more. The post on pretest probability explains how context changes the reading of each finding without removing the need to examine.

A problem that is not local

Smoke travels far. Cities distant from the fire can spend days with bad air, and the exposure reaches populations that do not see themselves as fire victims. Johnston and colleagues estimated the global mortality attributable to landscape fire smoke and showed that the problem affects several continents, with greater weight in tropical regions (Johnston and colleagues, 2012). The World Health Organization global air quality guidelines set reference values for fine particles and other pollutants and serve as the basis for many local indices (WHO Global Air Quality Guidelines, 2021).

This post deals with the person exposed to smoke in daily life. The direct victim of the fire, with burns or smoke inhalation at the scene, calls for another line of reasoning and is left for another text in the series.

Respiratory infections during smoke season

The review by Reid and colleagues points to growing evidence of an association between smoke and respiratory infections (Reid and colleagues, 2016). For clinical reasoning, this has a practical consequence: a cough that starts as irritation can progress to bronchitis or pneumonia in the following days. A person who improved with a bronchodilator and returns with fever, different sputum or worsening of general condition calls for a full reassessment, not just another round of the same treatment.

The same applies to a child with asthma who develops fever during the smoke week. The context explains part of the picture, and the fever calls for looking into the other part. Writing both hypotheses in the chart keeps the first from erasing the second.

Who decompensates first

Cascio reviewed the relationship between wildfire smoke and health and lists as most susceptible people with respiratory and possibly cardiovascular disease, middle-aged and older adults, children, pregnant people and the fetus (Cascio, 2018). This list helps organize active outreach to those under follow-up.

Group	Why they are more vulnerable	What to consider before worsening
Asthma	Airway already inflamed, reacts to particles and irritants	Updated written action plan for attacks, inhaler technique, warning signs
COPD	Small pulmonary reserve, risk of exacerbation and infection	Maintenance medication, when to seek care
Heart disease	Fine particles associated with acute events in some studies	Symptoms that are not from the smoke, adherence to treatment
Children	Breathe more air per weight, spend more time outdoors	School, physical activity, filtered environment
Pregnant people	Association with preterm birth in some studies	Reducing exposure, prenatal follow-up
Older adults and people who are isolated	Multiple diseases, less access to information and shelter	Who checks how they are doing, where they can stay

Children

Holm, Miller and Balmes reviewed the effects of wildfire smoke on children and explain that they are more vulnerable for physiological and behavioral reasons, and also discuss low-cost sensors, respirator use and air quality in schools (Holm and colleagues, 2021). For clinical reasoning, the question about where the child spends the day, and whether the school has filtration, belongs in the visit of any child with asthma during smoke season.

Pregnant people

A study in Colorado, in the United States, found an association between exposure to wildfire smoke during pregnancy, especially in the second trimester, and preterm birth (Abdo and colleagues, 2019). The finding does not justify alarm, but it justifies including air quality in the prenatal conversation in regions and seasons with fires.

Adjusting care before worsening

The best time to think about smoke is before decompensation. For people with asthma or COPD, fire season is a good occasion to review the written action plan for attacks, check inhaler technique, verify that there is enough rescue medication and agree on when to seek care. These measures follow the guidelines for each disease and the service protocol. What changes in this context is the urgency of doing them.

Carlsten and colleagues gathered, in a European Respiratory Society document, personal strategies to reduce the effects of air pollution on respiratory health: limiting outdoor exertion on days of high pollution, using air quality alert systems to plan activities, using masks in defined situations and using portable air purifiers with high-efficiency filters (Carlsten and colleagues, 2020). The authors note that well-designed prospective studies are lacking to confirm the clinical benefit of each measure.

Those who cannot protect themselves

Some of the most exposed people have fewer choices. Those who work outdoors, those who live in precarious housing, those who live on the street or those who care for other people cannot always stay indoors with filtered air. Risk also follows social conditions: in a fire in North Carolina, in the United States, the largest difference in the risk of emergency care for asthma and for heart failure linked to smoke appeared when counties were separated by socioeconomic factors (Rappold et al., 2012). For clinical reasoning, this changes the question asked in the consultation: instead of "what should the person do", it is worth asking "what can they do this week".

The answer may involve breaks in an enclosed space during work, a public place with filtered air during the worst hours, adjusting the time of activities or contact with social and public health services. Each of these measures complements public policy and reduces a little the exposure of those who need it most. Recording this conversation in the chart also helps the team recognize, at follow-up, why the person got worse again.

Air quality indexes as a clinical tool

Many countries publish daily air quality indexes. For those providing care, the index works as a context clue that helps guide the person about the day: postpone outdoor exercise, keep windows closed when the air outside is worse than the air inside, set up a cleaner room at home. The guidance needs to be concrete and adapted to each person's reality. Those who work outdoors or live in a house without sealing have fewer options, and the conversation should start from what is possible.

Filters and masks: what the evidence supports

Barn et al. argued that portable air purifiers should be at the center of the public health response to fire smoke, because they reduce the concentration of particles indoors (Barn et al., 2016). Holm et al. show that surgical masks offer limited protection and that well-fitted respirators protect much more, with the caveat that fitting them on children is difficult (Holm et al., 2021). The clinical reasoning here is about risks and gains: which measure the person can really use, and which brings more gain for their risk.

• Ask where the person spends most of the day and whether they can stay in a cleaner environment.
• Review the written crisis guidance and inhaler technique in those with asthma or COPD.
• Confirm that there is enough rescue medication for the next few days.
• Explain how to use the air quality index to decide about outdoor activities.
• Agree on warning signs and when to seek care without waiting.

When smoke hides another diagnosis

The scene of the fifty-five-year-old man with chest tightness is the center of this text. During a week of smoke, the explanation "irritation from smoke" is available for almost any respiratory or chest complaint. That availability is the problem. The context increases the probability of respiratory exacerbation, but it is also associated with cardiovascular events in some studies, and pneumonia may even become more likely (Reid et al., 2016).

Haikerwal et al. studied the 2006 and 2007 fires in Victoria, Australia, and found an association between the increase in fine particles and the risk of out-of-hospital cardiac arrest, as well as associations with visits for ischemic heart disease (Haikerwal et al., 2015). Even with cardiovascular evidence still mixed across studies, the lesson for the shift is that smoke can be the trigger of a cardiac event, and not the explanation of a benign symptom.

Questions that reopen the differential

• Does the pain have features of ischemia, such as worsening with exertion, radiation or sweating?
• Is the shortness of breath out of proportion to the worsening cough or wheezing?
• Is there fever, purulent sputum or a focal finding on auscultation that suggests pneumonia?
• Is there a risk factor for embolism, such as immobilization, recent surgery or cancer?
• Is the pattern of this crisis different from the person's own previous crises?

The last question is one of the most useful. People with asthma or COPD know their own attacks. When the person says that "this time it is different", that sentence weighs more than the orange sky outside. The post on examples of heuristics shows when the availability heuristic helps and when it gets in the way.

The exam that reopens the case

More than ordering many tests, what reopens the differential is examining with a question in mind. Asymmetric auscultation raises the hypothesis of pneumothorax or pneumonia. Lower limb edema and jugular distension point to heart failure. Tachycardia out of proportion to the respiratory picture, with low oximetry and little change in the lungs, suggests embolism. Each finding points to a different chapter, and the smoke explains none of them.

The person who arrived saying "it is the smoke" also deserves to be heard carefully. Sometimes they are right, and the exam confirms a typical exacerbation. Sometimes they are repeating the explanation they heard on the news. The history that asks when it started, how it started and what changed separates the two scenarios in most cases. The post on signs, symptoms and history helps organize this conversation.

The biases of the smoke scenario

The smoke week brings together haste, overcrowding and a ready explanation for almost everything. Pat Croskerry describes the most frequent cognitive errors in diagnosis and proposes metacognition, stopping and examining one's own reasoning, as the main way to reduce them (Croskerry, 2003).

A simple way to apply this is the diagnostic pause before closing each respiratory or chest case during the smoke week: what else could it be, what does not fit, what would I do if the smoke did not exist. The post on diagnostic pause describes the method in detail.

Attribution to context

The first bias is attributing to context what belongs to the patient. The smoke becomes an explanation for the cough, for the shortness of breath, for the tiredness and even for the chest pain. The correction is to write the working diagnosis and, next to it, the serious hypothesis that must be ruled out, with the exam or reassessment that will rule it out.

Anchoring on the known disease

The second bias is anchoring on the underlying disease. Someone with COPD who arrives with shortness of breath gets the label of exacerbation before the exam. Decompensated heart failure, pneumonia and embolism can present the same way, and the smoke does not change that.

Excess alarm

The third bias goes in the opposite direction. In a smoke season, healthy people with mild eye and throat irritation may receive unnecessary tests and treatments. Risk reasoning also serves to reassure those at low risk and explain what to watch for. The post on diagnostic uncertainty brings strategies for deciding well when the picture is not yet clear.

Reassess and decide on discharge

During the smoke week, the discharge decision depends on the environment the person will return to. A person with COPD who improved in the emergency department but will return to a home without sealing and without filtration has a higher risk of getting worse again in the following days. The base rate of readmission changes with context, and the post on base rate in diagnosis helps think about how this enters the decision.

At discharge, it is worth recording the working diagnosis and the hypotheses ruled out, the changes in treatment and in the written crisis guidance, the place where the person will stay and what they can do to reduce exposure. Also included are the signs that call for return and the follow-up contact, always with guidance to seek the necessary help if there is worsening. When follow-up is remote, by teleconsultation, the post on telemedicine shows how to keep clinical reasoning without an in-person exam.

How NEXO helps train this reasoning

In NEXO, the case of the day is fictional, with a real clinical presentation and up to six progressive clues. You propose a diagnosis by looking for the code in ICD-10 and receive feedback on proximity in five levels, which shows whether the guess landed on the exact code, the same category, the same group, the same chapter or a different chapter. This format connects with the theme of this text: when the context clue points to the respiratory chapter and the diagnosis is in the circulatory chapter, the proximity feedback shows the size of the deviation.

To use the case of the day as training against attribution to context, try three habits. Before each guess, write down the serious hypothesis you need to rule out. When a clue seems to explain everything, ask what it leaves unexplained. After the result, note which clue you overvalued.

Three exercises with cases

Switch the chapter. In every case with shortness of breath, write one respiratory hypothesis and one cardiovascular hypothesis before looking at the tests.

Compare with the person's baseline. In cases with chronic disease, ask what makes today's picture different from previous flare-ups.

Plan the exit. For each fictional case of exacerbation, write where the person will stay and what needs to change in the environment.

The post about case-based learning in clinical practice shows why training with cases helps lock in this kind of decision.

The limits on using the game are described on the NEXO economy page. If you research the teaching of clinical reasoning, the page for researchers explains how to get in touch. Professionals who write or review cases find information on curation and on creators, and institutions can learn about the proposal on the partnerships page.

Frequently asked questions

Who should be contacted first when the smoke arrives?

People with asthma, COPD or heart disease, pregnant women, children with respiratory disease and older adults who live alone. Active contact allows reviewing the written crisis guidance, checking the medication and advising on reducing exposure before things get worse.

Does smoke explain chest pain during fire season?

It may contribute, but it must be the last explanation, not the first. Chest pain calls for the same reasoning as always, with attention to ischemia, embolism, pneumothorax and pneumonia. Some studies link increases in fine particles to acute cardiac events.

Do masks help?

Well-fitted respirators protect more than surgical masks, which offer limited protection. Fitting is difficult in children and in people with beards. Reducing exposure at home, with a closed environment and filtration, is often the most feasible measure for many people.

How can the air quality index be used in the consultation?

As a context clue for planning the day. The index helps decide when to postpone outdoor exercise, when to keep windows closed and when to step up symptom monitoring. The guidance needs to fit the person's reality.

What changes for pregnant women?

Air quality comes into the prenatal conversation in regions and seasons with fires. Studies link smoke exposure to premature birth, which justifies advising reduced exposure without causing alarm.

When is discharge safe in a week of smoke?

When the picture is stable, serious hypotheses have been ruled out and the return environment allows reduced exposure. If the person is going back to a place without protection, it is worth discussing alternatives and arranging closer follow-up.

Final checklist

• I asked about smoke exposure, home environment and work in every respiratory or chest picture.
• I compared the current flare-up with the person's usual baseline.
• I wrote a cardiovascular and an infectious hypothesis next to the exacerbation.
• I reviewed the written crisis guidance, inhaler technique and rescue medication.
• I advised on the air quality index, filtration and use of a respirator when possible.
• I planned discharge considering the return environment and follow-up.

Want to practice reasoning with progressive clues? Play the case of the day.

References

1. Abdo M, Ward I, O'Dell K, et al. Impact of Wildfire Smoke on Adverse Pregnancy Outcomes in Colorado, 2007-2015. Int J Environ Res Public Health. 2019. PMID 31581673.
2. Barn PK, Elliott CT, Allen RW, et al. Portable air cleaners should be at the forefront of the public health response to landscape fire smoke. Environ Health. 2016. PMID 27887618.
3. Carlsten C, Salvi S, Wong GWK, et al. Personal strategies to minimise effects of air pollution on respiratory health: advice for providers, patients and the public. Eur Respir J. 2020. PMID 32241830.
4. Cascio WE. Wildland fire smoke and human health. Sci Total Environ. 2018. PMID 29272827.
5. Croskerry P. The importance of cognitive errors in diagnosis and strategies to minimize them. Acad Med. 2003. PMID 12915363.
6. Haikerwal A, Akram M, Del Monaco A, et al. Impact of Fine Particulate Matter (PM2.5) Exposure During Wildfires on Cardiovascular Health Outcomes. J Am Heart Assoc. 2015. PMID 26178402.
7. Holm SM, Miller MD, Balmes JR. Health effects of wildfire smoke in children and public health tools: a narrative review. J Expo Sci Environ Epidemiol. 2021. PMID 32952154.
8. Johnston FH, Henderson SB, Chen Y, et al. Estimated global mortality attributable to smoke from landscape fires. Environ Health Perspect. 2012. PMID 22456494.
9. Liu JC, Pereira G, Uhl SA, et al. A systematic review of the physical health impacts from non-occupational exposure to wildfire smoke. Environ Res. 2015. PMID 25460628.
10. Rappold AG, Cascio WE, Kilaru VJ, et al. Cardio-respiratory outcomes associated with exposure to wildfire smoke are modified by measures of community health. Environ Health. 2012. PMID 23006928.
11. Reid CE, Brauer M, Johnston FH, et al. Critical Review of Health Impacts of Wildfire Smoke Exposure. Environ Health Perspect. 2016. PMID 27082891.
12. World Health Organization. WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. 2021. who.int.