Respiratory Medicine

A diagnosis of COPD should be considered in any patient who has dyspnea, chronic cough, and/or sputum production and an appropriate history of exposure to noxious stimuli. However, not all patients with these symptoms have COPD, and a spirometry demonstrating a post-bronchodilator forced expiratory volume in one second to forced vital capacity (FEV1/FVC) ratio < 70% (or less than the lower limit of normal, if available) is required to make a definitive diagnosis. Starting maintenance inhalers without first objectively diagnosing COPD results in unnecessary treatment in those patients who do not actually have the disease. In turn, this exposes these patients to both the side-effects and the cost of these medications, and might delay the appropriate diagnosis.

Lung cancer screening with a chest CT scan has no proven benefit in patients who are not at high risk for lung cancer. The use of low dose chest CT scan for lung cancer screening has been found to reduce lung cancer mortality in patients at high risk for lung cancer. While there are some differences across jurisdictions in terms of the eligibility for enrollment in a screening program, the Canadian Task Force on Preventive Health Care currently recommends screening adults aged 55-74 years old with a 30 pack-year smoking history who currently smoke or quit less than 15 years ago, though some screening programs are using evidence-based risk assessment calculators to determine eligibility for enrollment. However, screening is also associated with several potential harms, including false-negative and false-positive results, incidental findings, overdiagnosis (detecting indolent and clinically insignificant tumors that would not have been detected in the patient’s lifetime without screening), and cumulative exposure to radiation (which can cause cancer). Screening also leads to unnecessary anxiety and invasive procedures, which carry their own complications. Accordingly, it should not be used in patients who do not meet these evidence-based criteria, nor in patients with a health problem that substantially limits life expectancy or the ability or willingness to undergo treatment. Where lung cancer screening is performed, it should be with a low dose, non-contrast CT protocol, to reduce the added risks related to excessive radiation exposure and contrast media. Because of the evolving nature of the evidence for lung cancer screening eligibility criteria, and the need to ensure access to all the necessary components of high-quality screening, it is recommended that lung cancer screening occur within an organized screening program when it is available within a reasonable geographic proximity and a reasonable wait time.

The majority of adults with chest pain and/or dyspnea do not have a pulmonary embolism (PE). There is strong evidence that in patients with low pre-test probability as determined by a clinical prediction rule (e.g., Wells score), a negative highly sensitive D-dimer assay effectively excludes clinically important PE. Furthermore, there are potential harms to performing CT pulmonary angiography (CTPA) or ventilation-perfusion (V/Q) scanning, including exposure to ionizing radiation, adverse events due to the administration of intravenous contrast, and identification of clinically insignificant PE leading to inappropriate anticoagulation. However, physicians should exercise clinical judgement in populations in whom this two-step algorithm has not been validated (e.g., pregnant patients).

The majority of adults with a short duration of cough from an acute respiratory tract infection have a viral rather than a bacterial infection. Patients often underestimate the typical cough duration from an infectious illness, and when cough does not resolve within their expected time frame, may request antibiotics. The average duration of cough (not treated with antibiotics) is around 18 days, though patients only expect to cough for 5 to 7 days. Use of immediate or delayed antibiotics does not change clinical outcomes compared to no antibiotics in these situations. On the other hand, the harms of over-prescribing antibiotics include medication costs, adverse reactions, and the possibility of inducing bacterial resistance to antibiotics. Physicians should educate patients about the expected duration of cough and the consequences of inappropriate antibiotic use in acute respiratory tract infections.

Although international guidelines uniformly recommend objective testing to establish an asthma diagnosis, this diagnosis is often made clinically and asthma medications are often initiated on that clinical basis. However, physical exam findings and symptoms such as cough, wheeze, and/or dyspnea can be caused by other conditions. As a result, up to one third of patients who have been diagnosed with asthma do not have evidence of asthma when objectively tested with pulmonary function tests. A false clinical diagnosis of asthma may delay diagnosis of the actual underlying condition, which may include serious cardiorespiratory conditions. Furthermore, patients with a false diagnosis of asthma who are started on asthma medications are unnecessarily exposed to both the side-effects and the costs of these medications.

For individuals 6 years of age and older who are able to reliably perform pulmonary function testing, an abnormal spirometry (or challenge test) can be helpful for confirming a diagnosis of asthma, however spirometry can also be falsely negative, especially in individuals with episodic symptoms.  Objective testing for asthma is not broadly available for children less than 6 years old and, in this age group, the diagnosis of asthma should be made clinically.

Following the global pandemic, availability of diagnostic testing is limited in many regions, and treatment can be initiated without confirmatory testing when diagnostic testing is not available in a timely manner. Individuals should be clinically reassessed, and the diagnosis should be confirmed with pulmonary function testing as soon as such testing is available. Consideration should strongly be given to stopping asthma therapy if the individual has not had a severe exacerbation in the last year, testing fails to confirm the diagnosis, and/or clear benefit is not observed. Where safe and possible, individuals should stop asthma controller therapy for 4-8 weeks to optimize the sensitivity of lung function testing for asthma diagnosis.  It is noted that measurement of lung volumes and diffusing capacity (DLCO) are not needed for a diagnosis of asthma.

Asthma exacerbations are characterized by decreased expiratory airflow as well as increased shortness of breath, cough, wheezing, chest tightness, or a combination of these symptoms. When such an attack is precipitated by an infection, it is much more likely to be viral than bacterial. The role of bacterial infection is often overestimated; however antibiotics should be reserved for relatively rare cases in which there is strong evidence of a bacterial infection, such as pneumonia or bacterial sinusitis. Potential harms of unnecessary antibiotic treatment include medication costs, side-effects (including a risk of allergy), and emergence of bacterial resistance.

Supporting patients with serious or progressive respiratory illness to identify and document their values and treatment wishes is an important, but often neglected, intervention. While these patients often experience complex disease trajectories that make accurate prognostication challenging, these discussions can ensure future care is aligned with patients’ preferences.

Metered-dose inhalers (MDIs) contain HFC propellants, which contribute to global warming. When prescribing inhalers, providers should consider whether an objective diagnosis of asthma and/or COPD exists or needs to be confirmed, in keeping with existing CWC CTS recommendations (#1 and #5). Also, optimal choice of controller inhaler agents and non-pharmacologic strategies (e.g. education, trigger avoidance, action plans) should always be included in airway disease management, as they not only improve patient outcomes, but can also reduce rescue inhaler use.

Low carbon footprint inhalers may not be appropriate for some patients (i.e. preschool children, individuals with certain cognitive limitations, end-stage lung disease, muscle weakness or other physical limitations, and during respiratory emergencies). Other patients simply prefer MDIs. Ultimately, whether starting or substituting an inhaler, providers must consider medication efficacy, patient preference, adherence, technique, cost, and side-effect profile. A shared decision-making approach should be used, and the environmental benefits of alternatives to greenhouse gas-intensive MDIs should also inform this decision.

Not all pulmonary nodules require CT surveillance. Benign nodules are common and often represent sequelae of a prior healed infectious or inflammatory process, benign endobronchial mucus plugs or pulmonary lymph nodes. Specifically, nodules with a benign pattern of calcification do not require any surveillance and should be clearly described as benign in the radiology report. These include nodules that are completely calcified, small nodules with central calcification and nodules with a complete circumferential ring of calcification. Calcification may be difficult to identify without thin section (less than 2 mm) slice reformats. Incidental nodules meeting criteria for a perifissural nodule typical for a intrapulmonary lymph node do not require surveillance. Perifissural lymph nodes have a characteristic CT appearance: located along a fissure, smoothly marginated, homogenously solid, polygonal, triangular or ovoid shaped and measuring less than 10mm.  Regardless of CT appearance an incidental solid nodule that has been stable for 2 years can also be safely considered benign (note that many nodules only require one year of surveillance). By making it clear that a nodule does not meet criteria for surveillance, radiologists may reduce unnecessary CT. Radiologists may wish to describe some benign nodules as post inflammatory, rather than “non-specific” to help reduce anxiety and limit over investigation. Referencing relevant practice guidelines can provide added confidence and can add support to the radiologist’s recommendation.

Joint recommendation with the Canadian Association of Radiologists

Current evidence regarding malignant risk of lung nodules by size is based on either 2-dimensional mean measurements or volume measurements. Mean dimension can be calculated by the average of the longest dimension and the perpendicular short axis dimension on a single CT plane. This is best measured in whichever plane produces the largest mean dimension value. Measurements should be made with thin section reconstruction (maximum thickness 1.5 mm). If radiologists report only the longest diameter, malignant risk will be overestimated, particularly for irregular (non-spherical) nodules. Using longest dimension to guide recommendations may result in unnecessary surveillance, over surveillance and over investigation. Guidelines from the Fleischner society regarding incidental pulmonary nodules use mean, not longest, dimension. ACR LungRADS® guidelines regarding management of screen-detected nodules also use mean dimension.

Joint recommendation with the Canadian Association of Radiologists

Accurate assessment of nodule growth requires reviewing all available prior imaging, and not just the most recent prior scan. Guideline frameworks emphasize longitudinal comparison over an extended interval often up to two years for solid nodules, 5 years for subsolid nodules, because stability over a longer period of time favours benignity. Volume doubling times for solid cancers are in the range of 100-400 days whereas mean doubling times for subsolid nodules are 3-5 years. The Fleischner Society’s 2017 Guidelines underscores serial assessment to accurately determine if a nodule is increasing in size. This is of critical importance for subsolid nodules that are typically indolent and slow-growing. For subsolid nodules, it is often necessary to compare to the oldest prior CT scan or baseline CT scan that is available to appreciate the slow growth in size and/or density. Restricting comparison to only the most recent CT scan increases the risk of misclassifying a nodule as stable when in fact it is slowly increasing in size when compared to remote CT scans or the baseline CT scan.

Joint recommendation with the Canadian Association of Radiologists

While flexible bronchoscopy is a safe and high-yield tool for sampling central lesions, flexible bronchoscopy has a low diagnostic yield for small peripheral lesions and should not be performed on its own without advanced adjunct endoscopic tools (e.g. radial endobronchial ultrasound).

Image-guided transthoracic needle biopsy (TTNB) has a high diagnostic yield for peripheral lung lesions and may be preferable to advanced endoscopic sampling depending on the location and characteristics of the nodule, patient factors such as underlying lung disease, as well as local availability and expertise. The environmental footprints of TTNB and flexible bronchoscopy with adjunct tools have not been compared.

In the setting of recurrent malignant pleural effusions, the primary management goal is to improve symptoms and functional status. Pleurodesis and indwelling pleural catheter placement are definitive interventions effective at improving dyspnea. A co-benefit of a definitive procedure is to reduce climate footprint by decreasing repeated transportation, equipment needs, and hospital resources, energy, and waste generation. As such, definitive options have the potential to improve patient care and reduce environmental footprint. Patient preference and shared decision making should always guide interventions for malignant pleural effusions.

Many single use medical devices are made from plastics that are difficult to recycle and contribute significantly to global pollution. There is general agreement that reusing materials, when feasible, is more sustainable than single use items. Reusable flexible bronchoscopes (RFB) require reprocessing, which is resource intensive, requiring manual cleaning and high-level disinfection sterilization. Nevertheless, reprocessing of reusable devices has been overwhelmingly found to be more environmentally sustainable in North American and European contexts, indicating SUFB should not be used in most circumstances. SUFB may have enhanced value in situations where minimizing the risk of infection is critical, such as for patients who are severely immunosuppressed, where highly resistant infectious organisms are present, or in very low-procedure volume settings where reprocessing is impractical.

Standard pulmonary function testing (PFT) to assess bronchodilator responsiveness utilizes short-acting beta agonist (SABA) or short-acting muscarinic antagonist (SAMA) inhalers, most commonly administered by metered dose inhaler (MDI). Similarly, these agents are administered for bronchodilation after a bronchoprovocation test (e.g. methacholine challenge testing). Discarding these inhalers after a single patient use results in plastic, metal, and medication waste and contributes to environmental pollution and climate change as well as avoidable health system costs. Studies have demonstrated that re-utilization of MDIs between patients is both safe, and effective for carbon footprint reduction. This will require keeping track of doses delivered (by count or weight) to ensure safety and optimal use. Collaboration with Infection Prevention and Control authorities is required to determine the optimal disinfection and re-utilization protocol that minimizes patient risk while concurrently minimizing environmental impact. Adjunct strategies to minimize environmental impact include selecting MDIs with a lower greenhouse gas generating propellant (HFC-134a rather than HFC-227ea) and/or HFCs with a low-volume of propellant per dose, ensuring proper technique to avoid wasted medication, and ensuring optimal inhaler disposal (ideally recycling programs tailored for inhalers, and if not available, then incineration).