Frequently Asked Questions: Sleep Disorders, Fatigue and Professional Operators

General Resources

Source: National Transportation Library

Obstructive sleep apnea (OSA) in commercial motor vehicle operators (CMVOs)

A variety of tools are available to screen CMVOs who are at higher risk for OSA.

In general, objective measures tend to be more reliable than self-reported symptoms.

Because obesity is a powerful risk factor for OSA, body mass index (BMI; a proxy variable for obesity) or neck circumference (indicative of central obesity) tend to be more reliable estimates for identifying those at high risk for OSA.

Varying BMI thresholds have been suggested to indicate high risk. These range from 30 kg/m2 (recommended by the Medical Review Board of the FMCSA); 33 kg/m2 (recommended by a Medical Expert Panel commissioned by the FMCSA, based on prior worki); or 35 kg/m2 (recommended by a 2012 joint commission of the Motor Carrier Safety Advisory Committee and Medical Review Board, a 2016 FMCSA Medical Review Board; and a Tri-Society Task Force).ii

Physical examination findings of a neck circumference larger than 17 inches in a man or 15.5 inches in a woman, a high modified Mallampati class airway (class III or IV), enlarged tonsils, or retrognathia on physical exam also indicate high OSA risk.

In general, symptoms such as loud habitual snoring, choking or gasping during sleep, breathing stops witnessed by others during sleep, unrefreshing sleep, and excessive daytime sleepiness can suggest the presence of OSA. The lack of these and other symptoms does not exclude the possibility of OSA.

Obesity, male gender, and middle age are among the most common risk factors for OSA. Because all three conditions exist commonly among CMVOs, the prevalence of OSA in this population tends to be high with estimates ranging from 28%iii to 60%.iv,v,vi One of the largest studies assessed 19,371 employees of a single trucking company and found that ~21% of drivers overall had at least 10 breathing pauses or reductions in airflow per hour. Among those at high risk based on a screening questionnaire, 80% had some degree of OSA, defined as at least 5 breathing pauses or reductions in airflow per hour.

The topic of HSAT in CMVOs has been reviewed previously.vii HSAT can be used in the diagnosis of OSA provided the CMVO achieves sleep the night of the recording, the HSAT chain of custody is secure, and OSA is at least moderate in severity. A positive test is useful, but a negative test does not exclude the possibility of OSA because HSAT can miss milder forms of the disease. Indeed, data loss occurs 10% of the time because HSATs are not monitored by a technologist. Programming the HSAT device to start automatically (rather than manually by the patient) can reduce data loss.

HSAT technologies vary widely in signals monitored, sampling rates, and scoring and analysis including automation for some manufacturers. In general, they use total monitoring time as a surrogate for total sleep time thereby systematically overestimating sleep duration. Some use actigraphy to estimate movement time to indicate wake time which increases the accuracy of total sleep time estimations.

The AASM has offered guidelinesviii regarding these technologies including: specific signals and their sampling frequency, manual scoring and review for devices with automated scoring algorithms, confirmatory in-laboratory polysomnography following negative HSAT results in patients with a high pre-test probability of OSA, and follow up care and management recommendations.

While HSAT offers lower cost, greater convenience, and the comfort of testing in one’s own home, this testing modality has limitations. HSAT is not as sensitive as in-lab testing with a false negative rate as high as 17%.ix Thus, a negative HSAT does not rule out the possibility of OSA. Also, HSAT only assesses for sleep-disordered breathing and not other sleep disorders such as periodic limb movement disorder, parasomnias, nocturnal seizures, bruxism, or narcolepsy. In general, HSAT does not record wake versus sleep, so total monitoring time is used as a proxy for total sleep time leading to systematic underestimation of sleep-disordered breathing. Because of this limitation, the test does not generate an AHI, but rather a Respiratory Event Index (REI). Also, sleep fragmentation (i.e., arousals from sleep) related to OSA, which is an important contributor to daytime sleepiness, is not routinely measured by HSAT. As such, HSAT can miss or underdiagnose patients and therefore is recommended for use in those with a high pretest probability of moderate to severe OSA. Patients with complicated medical or neurocognitive conditions such as neuromuscular disease, severe pulmonary disease, congestive heart failure, dementia, or other conditions are not appropriate candidates for HSAT.

Since HSATs are not monitored by a technologist, signal loss or artifact may limit the usefulness of the recording and chain of custody can be an issue. Testing failure requiring repeat testing can occur if a lead becomes displaced, disconnected, or falls off entirely while the patient is sleeping. Technical failures have been reported to occur about 10% of the time.x Devices that auto-start using a pre-programmed timer are less likely to fail than those that have a manual start feature, in which the patient is required to initiate the recording at bedtime.

In-laboratory polysomnography is the gold-standard measure to detect OSA, but certain limitations exist. First, this test is more expensive than HSAT and patients may have higher out-of-pocket costs. More and more third party payers are requiring prior authorization before testing, and, sometimes, such authorization for in-laboratory PSG is not given if sleep apnea is the suspected diagnosis; payers instead require HSAT as the initial diagnostic test.
Second, access to such testing may be limited, with waits in the U.S. reported to be 2-10 months.xi
Third, PSG requires the patient to sleep in an atypical environment which is problematic for several reasons:

  • The laboratory setting and monitoring equipment interferes with sleep.
  • Bedtime activities which influence breathing during sleep, such as alcohol intake or smoking, may be curtailed in the lab setting.
  • Allergens present at home that influence breathing may not be present in the laboratory.
  • Noise, lighting, temperature, and comfort level of the bedding in the laboratory may differ from those at home.

The FMCSA Medical Review Board recommended in 2016 that PAP be offered for all patients who have AHI ≥ 20 events/hour on in-laboratory polysomnography.xii

Be aware this AHI threshold is not interchangeable with the REI obtained on HSAT, since the latter is not expected to capture hypopneas that result in arousals, and total monitoring time, rather than total sleep time, is used in calculating the frequency of sleep-disordered breathing events during HSAT.

Additionally, lower AHI values on in-laboratory PSG or lower REI values on HSAT do not necessarily indicate milder disease. Patients with lower values of AHI or REI should still be offered PAP therapy if they are deemed to have at least moderate disease, which may be suggested by significant symptoms impacting daytime functioning, or by high levels of oxyhemoglobin desaturation during sleep, or the presence of co-morbid medical conditions.

Positive airway pressure (PAP) therapy is the most effective and reliable treatment for OSA of all severities. Many insurance providers require a trial of PAP therapy prior to consideration of coverage of alternate forms of treatment. PAP therapy is advantageous due to the ability to monitor treatment adherence on a daily basis. Some patients have difficulty tolerating PAP treatment for a variety of reasons. However, usage and tolerance are improved when therapy is supervised by sleep specialty providers.

Oral appliances are alternatives for patients with milder degrees of apnea that do not tolerate PAP therapy or prefer an alternative treatment.xiii Historically, the disadvantage of oral appliances was the lack of adherence tracking. If electronic adherence monitoring is validated in oral appliance therapies, they may become acceptable alternatives for transportation workers in the future.

Multilevel or stepwise surgical approaches can be considered for patients intolerant or unwilling to use PAP or oral appliance as long as patients are aware of the limitations and risks.xiv

Whichever form of therapy is chosen – PAP, oral appliance or surgical therapies — the treating physician should document objective improvement of OSA with a target AHI or REI of less than 5 events/hour. This is best accomplished by in-laboratory PSG, though in the case of milder OSA, auto-adjusting PAP devices in an unattended setting or HSAT may be a reasonable alternative.xv One should note that measurement of residual sleep-disordered breathing events using auto-adjusting PAP devices is heterogenous (i.e., manufacturer-specific) and may or may not reflect laboratory-based measurements.

Patients effectively treated surgically should be regularly screened for recurrent disease. Ongoing follow up for all treated patients is necessary to ensure adequacy of therapy, to document adherence, and to address any barriers to adherence or side-effects of therapy.

Drivers should be disqualified immediately or denied certification if they meet any of the following criteria:

  • Report EDS during the major wake period, while driving, OR
  • Experienced a crash that is thought to be due to drowsiness, OR
  • Fell asleep while driving
  • Have AHI ≥ 20 events/hour until treatment efficacy is established
    • for those on PAP, this means a download that shows effective therapy for one week
    • for those who have undergone surgery, a 3-month post-op re-evaluation with AHI < 20
  • Non-adherence with treatment at any point

In the absence of reasons for immediate disqualification:

  • An operator with BMI ≥ 33 kg/m2 may be certified for 2 months, pending sleep study and establishment of adherence with therapy
  • An operator with OSA may be certified for 1 month after starting PAP therapy, then certified for 3 months if adherence and efficacy are demonstrated. If adherence and efficacy are shown at 3 months, the driver may be certified for 1 year. Future certification depends on continued adherence and efficacy
  • Minimal acceptable adherence consists of using PAP for ≥ 4 hours/day on ≥ 70% of days
  • The clinician should use his or her judgment to determine whether more frequent visits or assessments may be required, based on the operator’s disease severity, adherence and individual response to therapy.

All individuals with OSA must be referred to a clinician with relevant expertise.

A CMVO should be re-evaluated by the medical examiner at least yearly. PAP is the preferred, first-line therapy.

Unconditional certification may be issued if:

The CMVO has AHI ≤ 20, and does not report excessive daytime sleepiness during the major wake period, OR The CMVO has OSA (any AHI) which is being effectively treated. The worker does not report experiencing excessive sleepiness during the major wake period, AND meets minimal acceptable adherence levels with treatment (average of ≥ 4 hours of use per day on ≥ 70% of days). Adequate PAP pressure should be established through one of the following: In-laboratory titration studyAuto-adjusting system

CMVOs should be informed that optimal benefits occur with at least 7 hours of daily use.

Following bariatric surgery, a CMVO may be certified if:

  • Effective treatment with PAP is established, OR
  • Re-evaluation (with sleep study) shows AHI < 10/hour at least 6-months post operatively (i.e., once weight nadir is reached), and the treating physician finds that OSA is effectively resolved, AND
  • Cleared by the treating surgeon, AND
  • Excessive daytime sleepiness is resolved

Patients who have an OSA diagnosis should be recertified annually. The CMVO should be advised to have more frequent reevaluation if he/she gains weight (≥ 5%) or if symptoms recur or worsen.

With oropharyngeal surgery, facial bone surgery, or tracheostomy recertification to operate a motor vehicle may occur if the following criteria are met:

  • At least 1 month elapses after surgery, to allow tissue edema to resolve, AND
  • The CMVO is cleared by the treating physician, AND
  • A sleep study shows AHI < 10, AND
  • Excessive daytime sleepiness is resolved

Annual recertification should be done in all patients who have had non-PAP therapies for OSA. If needed on the basis of symptoms, exam, or weight gain, a repeat sleep study should be done, to confirm that AHI < 10/hour; in addition, excessive daytime sleepiness should be resolved.

Because treatment efficacy cannot be ascertained on an ongoing basis, oral appliances are not acceptable for those in whom AHI is ≥ 20 events/hour.

A CMVO who has been disqualified from operating a motor vehicle due to untreated OSA or suspicion of OSA, may resume operating a vehicle if the operator meets the criteria outlined in items #9 and 10 above, such that the CMVO has been evaluated by a sleep specialist and shown to demonstrate objective evidence of adherence to PAP and efficacy of therapy.

The primary goal of OSA treatment is to demonstrate improvement of OSA severity, adherence to therapy, and improved patient symptoms.xvi Specific measures include a combination of physician judgement, symptom surveys, objective testing, and adherence data.

Employees in safety-sensitive positions pose unique challenges which include time limitations, concerns regarding employment, and treatment that is compatible with their job duties.

Improvement in OSA severity can be determined by either a sleep study while on the specific OSA therapy or a sleep study after corrective treatments such as weight loss (through lifestyle changes or bariatric surgery) or upper airway surgeries. However, one should note that these assessments do not provide ongoing evaluation of daytime function in “real time.” Therefore, all patients should be counseled that it is their responsibility to adhere to the prescribed therapy and to avoid drowsy driving. If they feel their OSA is not effectively treated they should alert their health care provider.

For PAP therapies, built-in technologies allow tracking of hours of use, pressure settings, mask leak, and residual AHI. Mask leak is useful in assessing efficacy because leak disrupts sleep quality and may impact the control of sleep-disordered breathing events. Efficacious treatment should also address and resolve mask leak.

Adherence tracking for oral appliances is under investigation. Currently these therapies do not monitor residual events. Body weight should also be monitored. Weight increases of 5% or more in those receiving non-PAP therapies should be re-evaluated to ensure treatment is efficacious. In patients receiving auto-adjusting PAP therapy, review of adherence data is necessary to ensure the device is adjusting adequately to increasing pressure requirements from weight gain and that the residual AHI remains low.

No specific measure alone is adequate to ascertain treatment efficacy. Rather, a comprehensive evaluation by a clinician with experience in sleep medicine is advised. Such evaluation may include a review of sleep hygiene and sleep schedule to ensure adequate sleep quality and sleep duration. Additionally, subjective measures such as the Epworth Sleepiness Scale, or objective measures such as the MSLT or MWT, should be considered, when appropriate.

Of note, subjective symptoms have been shown to be unreliable in employment settings, and MSLT/MWT data provide only a single “snapshot” of the point in time the test was completed. Such studies, though objectively measured (rather than subjectively reported), have not yet been shown to correlate with on-the-road performance.

In conditions in which public health and safety are at risk, reporting requirements generally supersede a patient’s right to privacy. Patients who are deemed to be at high risk for a crash, and who indicate an unwillingness to adhere to treatment recommendations at any time should be reported to state licensing agencies, medical examiners, employers, or the referring entity as appropriate. Reports should be directed to the state DOT. If possible, the referring medical examiner should also be notified. The patient should be informed of the physician’s requirement to report, that a report is being made, and the reason for reporting. This communication should be documented in the medical record.

i Ancoli-Israel S, Czeisler CA, Georgo CFP, Guilleminault C, Pack AI. Expert Panel Recommendations; Obstructive Sleep Apnea and Commercial Motor Vehicle Driver Safety. https://www.fmcsa.dot.gov/sites/fmcsa.dot.gov/files/docs/Sleep-MEP-Panel-Recommendations-508.pdf. Published January 14, 2008. Accessed February 10, 2017.
ii Hartenbaum N, Collop N, Rosen IM, et al. Sleep Apnea and Commercial Motor Vehicle Operators: Statement From the Joint Task Force of the American College of Chest Physicians, American College of Occupational and Environmental Medicine, and the National Sleep Foundation. J Occup Env Med.2006;48:S4–3
iii Pack AI, Dinges DF, Maislin G. A study of prevalence of sleep apnea among commercial truck drivers.FMCSA, Department of Transporation, Report Number DOT-RT-02-030. 2002. [Accessed September 14, 2012]. Available at: http://www.fmcsa.dot.gov/facts-research/research-technology/tech/sleep-apnea-technical-briefing.htm.
iv Howard ME, Desai AV, Gurunstein RR, et al. Sleepiness, sleep disordered breathing and accident risk factors in commercial vehicle drivers. Am J Respir Crit Care Med. 2004;170:1014–21.
v Stoohs RA, Bingham LA, Itoi A, Guilleminault C, Dement WC. Sleep and sleep-disordered breathing in commercial long-haul truck drivers. Chest. 1995;107:1275–82
vi Berger M, Varvarigou V, Rielly A, Czeisler CA, Malhotra A, Kales SN. Employer-Mandated Sleep Apnea Screening and Diagnosis in Commercial Drivers. Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine. 2012;54(8):1017-1025.
vii Zhang C, Berger M, Malhotra A, Kales SN. Portable diagnostic devices for identifying obstructive sleep apnea among commercial motor vehicle drivers: considerations and unanswered questions. Sleep.2012;35:1481–9
viii Collop NA, Anderson WM, Boehlecke B, et al. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. Portable Monitoring Task Force of the American Academy of Sleep Medicine. J Clin Sleep Med. 2007;3:737–47
ix Collop NA, Anderson WM, Boehlecke B, et al.; Portable Monitoring Task Force of the American Academy of Sleep Medicine. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. J Clin Sleep Med. 2007 Dec 15;3(7):737-47.
x Shayeb ME, Topfer LA, Stafinski T, et al., “Diagnostic accuracy of level 3 portable sleep tests versus level 1 polysomnography for sleep-disordered breathing: a systematic review and meta-analysis,” Canadian Medical Association Journal, vol. 186, no. 1, pp. E25–E51, 2014.
xi Flemons W, Douglas NJ, Kuna ST, etc, “Access to diagnosis and treatment of patients with suspected sleep apnea,” American Journal of Respiratory and Critical Care Medicine, vol. 169, no. 6, pp. 668–672, 2004.
xii Medical Review Board. Task 16-01 Draft Letter Report. https://www.fmcsa.dot.gov/advisory-committees/mcsac/mrb-task-16-01-letter-report. Published August 2016. Accessed February 10, 2017.
xiii Ramar K, Dort LC, Katz S etal. Clinical practice guideline for the treatment of obstructive sleep apnea and snoring with oral appliance therapy: An update for 2015. J Clinic Sleep Med 2015;11(7):773-827
xiv Aurora R, Casey K, Kristo D, etal. Practice parameters for the surgical modifications of the upper airway for obstructive sleep apnea in adults. Sleep 2010;33(10):1408-13.
xv Morgenthaler T, Aurora R, Brown T, etal. Practice parameters for the use of autotitrating continuous positive airway pressure devices for titrating pressures and treating adult patients with obstructive sleep apnea syndrome. Sleep 2008;31(1):141-7.
xvi Weaver TE, Chasens ER. Continuous positive airway pressure treatment for OSA in older adults. Sleep Med Rev. 2007 Apr;11(2):99-111. Epub 2007 Feb 1.

Fatigue and sleep disorders in the marine industry

  • As with other transportation industries, insufficient sleep is a common occurrence in the marine industry owing to long work hours and around the clock operations.
  • Work in the marine environment is demanding and prone to high levels of fatigue.
  • Increasingly larger ocean-going vessels are being operated by ever-smaller crews, leading to a greater risk of fatigue and fatigue-related accidents.

Fatigue in the maritime industry differs from other transportation industries in unique ways:

Work Environment

  • Mariners live away from home and family for long periods of time.
  • Workers work in close quarters with shipmates from different countries speaking different languages.
  • Mariners work on the open seas, where the weather is unpredictable and often dangerous.
  • Workers are required to maintain a high level of vigilance to avoid injury, property damage, and environmental catastrophe.
  • Navigation through different marine environments (e.g. ports) requires pilot hand-offs governed by local regulation with highly variable shift, sleep, and fatigue mitigation requirements.

Sleep Environment

  • Workers sleep in cramped spaces that lack privacy
  • Sleep spaces are subject to loud noise, vibration, and heat

Physical Demands on Mariners

  • Workers must be able to:
    • Participate in emergency procedures
      • Fight fires
      • Launch lifeboats
      • Respond to man-overboard
    • Climb steep vertical ladders
    • Maintain balance on moving deck in bad weather
    • Pull heavy fire hoses up to 400 feet
    • Open and close watertight doors that weigh 55 lbs.
    • Crouch, kneel, crawl, and move through restricted openings of 24 X 24 inches.

Diversity of Marine Occupation

Marine occupations and work environments are very diverse, require different degrees of vigilance, and are prone to different degrees of fatigue risk. Periods of monotony are punctuated by periods of high activity.  For example, navigating a container ship in the open seas is substantially different from navigating the same ship into a busy port. Working on an oil rig in the open seas poses quite a different set of challenges compared to navigating a tow boat, with its many articulating barges, through a river channel.  Knowledge of the inherent dangers associated with the type of work and the environment in which it is done is essential to assess safety risk and provide fitness for duty evaluations.

Marine Accidents

Fatigue-related accidents in the marine transportation industry are different from accidents in other transportation modalities.

  • Accidents are often due to loss of situational awareness, poor judgement and poor decision-making rather than due to brief lapses in alertness.
  • Although marine vessels travel more slowly compared to those in other transportation industries, by the time an error is recognized, it is often too late to correct the trajectory to avoid collision.
  • Accidents often lead to enormous economic and environmental losses (e.g. Exxon Valdez Accident)

  • The Marine Safety Committee of International Maritime Organization (IMO) has created a comprehensive document to educate the stakeholders of the marine industry about fatigue, its causes, and strategies to mitigate it.[1]
  • Crew Endurance Management System, a practical guide to mitigate the risk of fatigue and fatigue related accidents[2] is also available.
[1] Guidance on Fatigue Mitigation and Management

https://www.imo.org/en/OurWork/HumanElement/Pages/Fatigue.aspx.  Last accessed 1/23/2021

[2]

Crew Endurance Management Practices https://www.dco.uscg.mil/Portals/9/DCO%20Documents/5p/5ps/Design%20and%20Engineering%20Standards/Human%20Element%20and%20Ship%20Design%20Division/GuideForMaritimeOperations.pdf. Last accessed 11/20/2019.

Governmental Agencies:

  • The U.S. Coast Guard (USCG) is the main regulatory agency with authority over inland and coastal waterways.
  • Each state has authority over its own waterways, but the regulatory systems are very similar to one another.

Private Organizations: There are a number of industry organizations that influence policy, including but not limited to

  • The American Waterways Operators (AWO)
  • The American Pilots Association
  • Seafarers International Union

Medical certificates are required for all licensed officers and certain mariners with qualifying endorsements. The National Maritime Center (NMC), a branch of USCG in Martinsburg, West Virginia, issues the medical certificates.

  • The NVIC 4-08 specifies the medical and physical evaluation guidelines for merchant mariners.
  • The Merchant Mariner Medical Manual provides more detailed guidance, specifically to evaluating medical practitioners, on the medical the physical requirements of mariners.
  • Mariners apply for their medical certificate every 5 years by completing the CG-719K application form. A medical practitioner verifies the history documented on the CG-719K and completes the physical examination portion of the application.
  • The physical examination assesses vision, hearing, and physical ability. The physical ability assessment must take into account the physical demands of marine work as described above.

  • The CG-719K medical credential application form specifically asks about sleep disorders.
  • The recommendations for obstructive sleep apnea screening are outlined in the Merchant Mariner Medical Manual and included in the appendix
  • Sleep apnea is considered a medical condition that poses a “significant risk of sudden incapacitation or debilitating complication” and is therefore a disqualifying condition.
  • Mariners can obtain a waiver for sleep apnea by demonstrating adequate treatment of sleep apnea.
  • Waiver for sleep apnea requires additional documentation
    • Diagnostic sleep study
    • Documentation of treatment adherence (e.g. CPAP adherence report or a medical practitioner note).

Sleep is essential for health and safety.  To improve the effectiveness of the guidelines, USCG should also adopt policies aimed at improving the quality of mariner examinations. One way to do this is to develop a “designated medical examiner” program whereby medical examinations are conducted by properly trained providers with knowledge related to marine specific health and safety risks related to untreated OSA, other untreated sleep disorders, insufficient sleep, and shift work. More consistent application of the currently available knowledge about sleep fatigue will lead to greater safety.

Appendix

Recommendations on screening for obstructive sleep apnea (OSA).[3]

  • The examining medical practitioner should assess the mariner applicant’s risk factors for OSA and then determine whether further evaluation is indicated. Risk factors for OSA may include, but are not limited to:
    1. Medical history of hypertension, diabetes, elevated blood sugars, elevated cholesterol, coronary artery disease, atrial fibrillation or stroke.
    2. Personal history of smoking.
    3. Personal history of obesity, and /or neck circumference greater than 17 inches (male) or 16 inches (female).
    4. Personal history of sedentary lifestyle.
    5. Personal history of snoring or observed apnea.
    6. Personal history of accident(s) related to falling asleep while working, driving or operating a vessel.
    7. Symptoms of non-restful sleep, fatigue, or day-time sleepiness.
  • Examples of screening tools for OSA may include validated office-based screening tools such as the STOP-Bang questionnaire.
  • If the examining medical practitioner determines that the mariner applicant is at significant risk for OSA, the examiner should provide the applicant with education on OSA and refer for appropriate evaluation and testing.
    1. Further evaluation may include referral to a primary care provider, internist, or sleep specialist, as appropriate.
    2. When medically indicated, diagnostic testing may include a home sleep study that measures a minimum of three channels to include air flow, respiratory effort, and pulse oximetry; or attended polysomnogram.
  • If the examining medical practitioner determines that the applicant needs further evaluation for OSA but assesses that the applicant is NOT at immediate risk of sudden incapacitation, then the applicant may be considered for a time-limited medical certificate to allow time to complete the evaluation.

[3] Merchant Mariner Medical Manual

https://media.defense.gov/2019/Sep/11/2002181050/-1/-1/0/CIM_16721_48.PDF. Last accessed 11/20/2019