Contraindications

A couple weeks ago I was asked whether it was safe for a patient with an abdominal aortic aneurysm (AAA) to have pulmonary function testing. My first thought was that it was probably unsafe but after a moment or two of thought I realized that I hadn’t reviewed the subject for a long time. When I checked the 2005 ATS/ERS general testing guidelines (there are no contraindications in the 2005 spirometry guidelines) I found that AAA wasn’t mentioned at all. In fact, the only absolute contraindication mentioned was that patients with a recent myocardial infarction (<1 month) should not be tested. Some relative contraindications were mentioned:

• chest or abdominal pain
• oral or facial pain
• stress incontinence
• dementia or confusional state

and activities that should be avoided prior to testing include:

• smoking within 1 hour of testing
• consuming alcohol within 4 hours of testing
• performing vigorous exercise within 30 minutes of testing
• wearing clothing that restricts the chest or abdomen
• eating a large meal with 2 hours of testing

but these were factors where test results were likely to be suboptimal and not actually contraindications.

This got me curious since I thought that pulmonary function testing was contraindicated for more conditions than just an MI. I reviewed the 1994 and and then the 1987 ATS statements on spirometry but again found no mention of contraindications. Ditto on the 1993 ERS statement on spirometry and lung volumes. Finally, in the 1996 AARC clinical guidelines for spirometry I found a much longer list of contraindications:

• hemoptysis of unknown origin
• pneumothorax
• recent mycardial infarction
• recent pulmonary embolus
• thoracic, abdominal or cerebral aneuysms
• recent eye surgery
• presence of an acute disease process that might interfere with test performance (e.g. nausea, vomiting)
• recent surgery of thorax or abdomen

So where did the AARC’s list of contraindications come from? And why is there such a discrepancy between the ATS/ERS and the AARC guidelines?

A search of the literature led me to BG Cooper’s excellent review of the subject. He points out that the contraindications in both the ATS/ERS and AARC guidelines are based on expert opinion that originated more than 30 years prior to the publication of either standard and not from any formal research. In addition changes in medical technology and practices make the value of many of these older contraindications questionable. In particular changes in post-surgical patient care, and most specifically the widespread use of incentive spirometry (which is usually instituted immediately following surgery) has patients performing maneuvers that are similar in nature to pulmonary function testing.

So what makes anything a contraindication? The primary requirement for this has to be the level of risk. Risk is determined by two factors; first, the likelihood that an ‘adverse event’ will occur during pulmonary function testing. Second, the severity of the ‘adverse event’ if and when it does occur. An absolute contraindication has both a high likelihood of occurring and a high degree of severity. A relative contraindication on the other hand is where either the likelihood or the severity of an adverse event is low. There’s a level of risk that’s greater than zero, but that risk depends on an individual patient’s status.

Whenever there is any level of risk, it of course has to be outweighed by the potential benefit ratio of testing. There are going to be situations where even though spirometry has an elevated level of risk the information it provides is critical to the patient’s care. Realistically however, the number of times when the results from any pulmonary function tests will have an immediate benefit for a patient with a high level of risk are rare and it is more likely that testing can be deferred to another time.

Cooper reviewed surgical and medical literature extensively and by cross referencing the likelihood and potential severity of adverse events, developed an evidence-based list of contraindications.

Contraindication:	Complication:	Likelihood:	Severity:	Risk:
MI (recent)	Death	5	5	25
MI (recent)	Further MI	5	5	25
PE (untreated)	Death	4	5	25
Ascending Aortic Aneurysm (>6 cm dilation)	Death	4	5	20
Ascending Aortic Aneurysm (>6 cm dilation)	MI	4	4	16
Pneumothorax	Lung collapse	3	4	12
Thoracic surgery	futher surgery	3	4	12
Pneumothorax	Pain	5	2	10
Ascending Aortic Aneurysm (<6 cm dilation)	Death	2	5	10
Thoracic surgery	Death	2	5	10
Hemoptysis	Bleed	2	4	8
Angina	MI	2	4	8
Ascending Aortic Aneurysm (<6 cm dilation)	MI	2	4	8
Eye surgery (<1 week)	Undo surgery	2	3	6
Abdominal surgery	Pain	3	2	6
Thoracic surgery	Pain	3	2	6
Hemoptysis	Death	1	5	5
Pneumothorax	Discomfort	5	1	5
MI (>1 week)	Death	1	5	5
PE (treated)	Death	1	5	5
Hemoptysis	PE	1	4	4
Acute diarrhea	Discomfort	4	1	4
Abdominal surgery	Rupture	1	4	4
Angina	Pain	2	2	4
PE (treated)	Hypoxia	1	3	3
Eye surgery (<4 week)	Undo surgery	1	3	3
Eye surgery (<4 week)	Pain	1	2	2
MI (>1 week)	Pain	1	2	2

Where the scoring for likelihood, severity and risk are:

Likelihood:
1	<1%
2	2-10%
3	11-20%
4	20-50%
5	>50%

Risk:
1-4	Low
5-9	Moderate
10-19	High
20-25	Very High

Severity:
1	Discomfort
2	Pain
3	Syncope/bleeding
4	Tissue Damage, minor surgery
5	Emergency care, major surgery, death

Cooper’s list is, of course, a simplification and an individual patient’s level of risk may differ from these general guidelines for any number of reasons. Nevertheless, it is an excellent starting point for an ordering physician who is attempting to determine the risks versus the benefits of pulmonary function testing for a patient.

The list however, is primarily oriented towards spirometry, since that test tends to generate relatively large intra-thoracic and intra-abdominal pressures. Since MIP and MEP testing also generates high intra-thoracic and intra-abdominal pressures the same contradictions likely apply. Lung volume measurements (regardless of which technique) and DLCO also require a vital capacity maneuver, but this can (and should) be performed with significantly less force and therefore much lower intra-thoracic and intra-abdominal pressures. Any patient for whom incentive spirometry can be ordered should be able to perform lung volume and DLCO testing.

A more specific contraindication for lung volume measurements (specifically the helium dilution and plethysmographic techniques) is the potential for hypoxia in oxygen-dependent patients. When lung volumes are important for the management of a patient’s care however, this can be managed to some extent by monitoring a patient’s oxygen saturation with a pulse oximeter and terminating testing only if SpO2 drops below a safe threshold. A more likely limitation in these patients however, is claustrophobia which is a common occurrence in those who are chronically dyspneic.

Elevated levels of carbon monoxide has been raised as a potential concern for DLCO testing, particularly for pregnant women. Realistically however, the level of CO that a developing fetus is exposed to from DLCO testing is no greater than would routinely be seen in urban settings, and certainly is far less risky than cigarette smoking would be.

Exercise testing at either moderate (6-minute walk) or heavy (CPET) levels needs to be evaluated on a case-by-case basis. It should be noted that early post-surgical mobilization of patients has become a common practice so exercise per se is not necessarily contraindicated. Testing may be instead be contraindicated for neurological or musculoskeletal reasons such as paralysis, balance, and weakness that have nothing to do with respiratory, cardiovascular or post-surgical factors. However, the 2003 ATS/ACCP statement on cardiopulmonary exercise testing lists the following as absolute contraindications:

• Acute myocardial infarction (3–5 days)
• Unstable angina
• Uncontrolled arrhythmias causing symptoms or hemodynamic compromise
• Syncope
• Active endocarditis
• Acute myocarditis or pericarditis
• Symptomatic severe aortic stenosis
• Uncontrolled heart failure
• Acute pulmonary embolus or pulmonary infarction
• Thrombosis of lower extremities
• Suspected dissecting aneurysm
• Uncontrolled asthma
• Pulmonary edema
• Room air desaturation at rest <85%
• Respiratory failure
• Acute noncardiopulmonary disorder that may affect exercise performance or be aggravated by exercise (i.e. infection, renal failure, thyrotoxicosis)
• Mental impairment leading to inability to cooperate

and the following as relative contraindications:

• Left main coronary stenosis or its equivalent
• Moderate stenotic valvular heart disease
• Severe untreated arterial hypertension at rest (>200 mm Hg systolic, >120 mm Hg diastolic)
• Tachyarrhythmias or bradyarrhythmias
• High-degree atrioventricular (AV) block
• Hypertrophic cardiomyopathy
• Significant pulmonary hypertension
• Advanced or complicated pregnancy
• Electrolyte abnormalities
• Orthopedic impairment that compromises exercise performance

The 2014 ERS/ATS statement on field walking tests (which includes the 6-minute walk test) indicates that the same contraindications apply to walking tests as apply to cardiopulmonary tests indicated in the 2003 statement.

The 2001 AHA statement on exercise testing has an essentially identical list of contraindications as the ATS/ACCP 2003 statement but as absolute contraindications it includes:

• Physical disability that would preclude safe and adequate test performance
• Inability to obtain consent

and for relative contraindications it includes:

• Atrial fibrillation with uncontrolled ventricular rate
• Electrolyte abnormalities

Since challenge testing (methacholine, cold air, eucapnic voluntary hyperventilation, exercise) includes spirometry, the contraindications from the 2017 ERS statement includes factors that are similar to those mentioned in Cooper’s list, but since the intent of challenge testing is to induce bronchoconstriction (under controlled conditions, of course) it contains some that are specific to this form of testing:

• FEV 1 <60% predicted (adults or children) or 1.5 L (adults)
• FEV 1 <75% predicted (adults or children) for exercise or eucapnic voluntary hyperventilation challenge
• Inability to perform acceptable and repeatable spirometry manoeuvres throughout the test procedure
• Cardiovascular problems
• Myocardial infarction or stroke in last 3 months
• Uncontrolled hypertension
• Known aortic aneurysm
• Recent eye surgery or intracranial pressure elevation risk
• Inability to perform any of the testing manoeuvres

Finally, for bronchodilator reversibility testing using beta-agonist inhalers, there are the following relative contraindications:

• Thyrotoxicosis
• Heart failure
• Hypertension
• Tachydysrhythmias
• Decreased glucose tolerance
• Unstable diabetes mellitus and the concomitant use of cardiac glycosides.

However, it has been noted that these contraindication actually apply to the risks involved with the regular use of beta-agonist inhalers and the risk of a single administration for diagnostic purposes is likely small.

What is clear from all this is that the single absolute contraindication to routine pulmonary function testing included in the ATS/ERS 2005 general considerations statement is far too limited. The AARC 1996 contraindications are more similar to Cooper’s list, but lacks nuance or any indication of relative risk. For these reasons I think that until such time as the ATS and/or ERS update the standards for pulmonary function testing Cooper’s list should be added to every PFT Lab’s procedure manual.

Contraindications are a somewhat neglected part of our field and I think this is because we rarely have a complete diagnosis and patient history available to us when tests are scheduled. Nor do we have the time to review this information, nor for that matter do we necessarily have the expertise. The appropriateness of tests and their risks and benefits for a patient are up to the physician ordering their tests and they are often unaware of possible contraindications. For this reason I’d recommend that labs should have a document detailing contraindications to PFT testing (example) that can be mailed or emailed to physicians whenever necessary.

I don’t have a good answer why there is only one absolute contraindication in the 2005 ATS/ERS statement when there were so many in the 1996 AARC statement. It’s possible that the ATS/ERS participants thought that without objective data, expert opinion was just that, opinion. Still though, contraindications are important for patient safety and it seems that more attention should have been paid to this issue.

I was able to report my findings to my medical director and the patient with the AAA was eventually tested without incident. It was evident however, that my lab’s procedure manual needs to be updated and that we need to be better prepared to respond to this issue.

References:

AARC Clinical Practice Guideline. Spirometry 1996 Update. Respir Care 1996; 41: 629-636.

American Thoracic Society. Guidelines for Methacholine and Exercise challenge testing – 1999. Amer J Respir Crit Care Med 2000; 161: 309-329.

ATS/ACCP Statement on cardiopulmonary exercise testing. Amer J Respir Crit Care Med 2003; 167: 211-277.

ATS Standardization of spirometry – 1987 Update. Amer Rev Respir Dis 1987; 136: 1285-1296.

ATS Standardization of spirometry – 1994 Update. Amer J Respir Crit Care Med 1995; 152: 1107-1136.

Brusasco V, Crapo R, Viegi G. ATS/ERS Task Force: Standardisation of lung function testing. General considerations for lung function testing. Eur Respir J 2005; 26: 153-161.

Coates AL, Wanger J, Cockcroft DW et al. ERS Technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests. Eur Respir J 2017; 49: 1601526.

Cooper BG. An update on contraindications for lung function testing. Thorax 2011; 66: 714-723.

Fletcher GF, Balady GJ, Amserdam EA, et al. AHA Scientific statement. Exercise standards for testing and training. A statement for healthcare professionals from the American Heart Association. Circ 2001; 104: 1694-1740.

Holland AE, Spruit MA, Trooster T et al. An official European Respiratory Society/American Thoracic Society technical standard: field walking tests in chronic respiratory disease. Eur Respir J 2014; 44: 1428-1446.

Quanjer PH, Tammeling GJ, Cotes JE, Pedersen OF, Peslin R, Yernault JC. Lung volumes and forced ventilatory flows. Official statement of the European Respiratory Society. Eur Respir J 1993; Suppl 16: 5-40.