Portable Monitoring in a Hospital Setting

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by Hassan Abouhouli, MD, and Frank M. Ralls, MD

Meeting diagnostic needs through a collaborative approach.

2012-08 05-01

The use of portable monitoring (PM) for diagnosing obstructive sleep apnea (OSA) in the hospital setting is still being explored. Few hospitals have the capability to perform full polysomnography at the bedside, likely due to a lack of resources or limited budgets. However, through collaboration of the medical services, patients can be tested for sleep apnea with PM, as demonstrated in the case of a 40-year-old morbidly obese male with OSA.

Designed for application in a home setting, American Academy of Sleep Medicine (AASM) clinical guidelines for the use of unattended PM state, “PM is not appropriate for the diagnosis of OSA in patients with significant comorbid medical conditions that may degrade the accuracy of PM, including, but not limited to, moderate to severe pulmonary disease, neuromuscular disease, or congestive heart failure.” The AASM guidelines also state, “PM may be indicated for the diagnosis of OSA in patients for whom in-laboratory PSG is not possible by virtue of immobility, safety, or critical illness.” For inpatients who suffer from multiple medical comorbidities, in many cases, the primary goal of quick and efficient evaluation is to prevent rapid posthospital decompensation, which may be prevented by the effective management and treatment of sleep-disordered breathing.

A common scenario at academic medical centers is to receive a request from a resident or faculty member for an inpatient sleep consult. The consult is requested when an inpatient demonstrates symptoms consistent with OSA, which raise concern for increasing the likelihood of readmission, for complications, or for a delay in discharge. Once loud snoring and significant oxygen desaturations are documented, there is a reluctance to discharge the patient without treatment.

At the University of New Mexico Hospital Sleep Disorders Center, we recently used PM to assist with the diagnosis and treatment of OSA for a patient with extensive comorbidities and a history of frequent rapid readmissions post-discharge. Our experience illustrates the potential benefits of an expedited diagnosis of OSA prior to discharge.


An urgent request was made for sleep medicine to consult, evaluate, and treat a 40-year-old morbidly obese male with a medical history of end stage renal disease (ESRD) on hemodialysis, type 2 diabetes, and hypertension. The patient was initially admitted to the hospital for increasing dyspnea and increasing somnolence. The patient also complained of morning headaches, nocturnal cough, frequent awakenings, and gasping for air. The patient was unable to tolerate more than 1 hour of dialysis per day secondary to pain, and the attending physicians were concerned that effective treatment of pain with narcotics would further suppress respiration. After admission to the hospital, the inpatient medical staff documented heroic snoring (snoring heard two rooms away), witnessed apneic events, and blood gases consistent with respiratory failure (severe hypercapnia).

The patient’s vital signs showed blood pressure 150/70, respiratory rate 14, heart rate 90, and oxyhemoglobin saturation of 88% on 4 liters of oxygen via nasal cannula (NC). The patient had a depressed affect, was somewhat somnolent, and made a minimal effort to respond to questions. His weight was 217.2 kg/m2 (479 pounds), height 185.3 cm (73 inches) tall, neck circumference 19 inches, and he had a BMI of 63.3. The Mallampati score was 4, tonsil score was 0, and mild micrognathia was noted. Lung exam revealed decreased breath sounds bilaterally. He had 2+ pitting edema in bilateral lower extremities. Arterial blood gases (ABGs) were pH 7.27, Pco2 61 torr, Pao2 101 torr, and HCO2 25 mEq/L on 4 L/min of oxygen via nasal cannula.

Pertinent medications included buproprion 100 mg qday, warfarin 2 mg qday, metoprolol 50 mg bid, insulin lispro 6 units with meals, sevelamer 3,200 mg tid, oxycodone 5 mg q 6 hours prn, trazodone 50 mg qhs, simvastatin 40 mg qhs, and oxygen at 4 liters via NC.

The patient had multiple past admissions for respiratory failure and acute mental status changes. A previous pulmonary consult for hypercapnia and hypoxemia resulted in him being empirically titrated with a bilevel PAP pressure of 18/6 cm H2O. Although this appeared to be an effective treatment, the staff was informed that his insurance refused to provide outpatient coverage for PAP therapy because the patient had not met the criteria for OSA with a diagnostic polysomnogram. On the current admission, it was clear by the patient’s presentation and pulmonary work-up that he suffered from obesity hypoventilation and was once again in acute-on-chronic respiratory failure. These were most likely exacerbated by the lack of treatment of his sleep-disordered breathing in the outpatient setting.

2012-08 05-02

Figure 1. Portable monitoring performed on an inpatient who shows an AHI of 21 and an oxygen nadir of 58%.


In order to provide outpatient treatment for OSA, a diagnostic PSG was necessary. Ongoing treatment would help to improve the comorbidities. Our facility does provide bedside polysomnography when indicated and available. However, due to a lack of available equipment, an alternative intervention was required.

After consulting with the primary team, it was decided to use PM. A registered polysomnographic technologist attached the portable monitor unit to the patient.

The diagnostic unit provided six channels: nasal pressure, thermocouple, chest and abdominal effort, snore signal, and oximetry. Due to the significant comorbidities, we chose to utilize a type III PM device, defined as a minimum of four channels. In type III monitoring, measurement of ventilation requires at least two channels of respiratory movement or respiratory movement and airflow. A type III portable monitor allows for the identification and screening of other potential respiratory and movement disorders, for example: hypopneas, differentiation between central, obstructive, or mixed apneas and leg movements (channel not shown but easily added). Type III monitoring (as opposed to type IV devices) increases the accuracy of the diagnosis and helps to determine long-term management options.

For the study, the technologist applied the sensors to the patient and provided education to the patient and the patient’s nurse. The nursing staff was further educated on basic trouble-shooting of the portable unit. Contact information was left for the nursing staff should any problems arise during the study period. The unit was picked up by the technologist the next morning and promptly scored for review by the sleep specialist.

The results of the study provided 3 hours of diagnostic data. The data indicated an apnea/hypopnea index (AHI) of 21 per hour and an oxygen saturation nadir of 58%. As the patient was continued on oxygen at 4 liters via NC during the study, the results clearly underestimate the patient’s true AHI. Although results provided a diagnosis of obstructive sleep apnea that met insurance requirements, we note that supplemental oxygen could degrade the ability of the nasal pressure transducer to detect respiratory events; therefore, we caution against the routine use of PM for patients who require administration of supplemental oxygen.


This patient was diagnosed with obstructive sleep apnea. Significant comorbidities included obesity hypoventilation syndrome, ESRD, hypertension, atrial fibrillation, neuropathy, uncontrolled pain, undertreated depression, and anxiety. Chronic pain adversely affected the patient’s ability to sleep as well as tolerate more than 1 hour of dialysis daily.


Since the patient had been in respiratory failure (hypercapnia), the pulmonary team successfully titrated the patient on bilevel by following his tidal volume, minute ventilation, and serial arterial ABGs for arterial PcO2. He was titrated to 18/12 cm H2O with 4 L/min oxygen bleed.

Palliative medicine was consulted and provided supportive care, as well as options for more effective pain control, which allowed the patient to tolerate dialysis. Early involvement of the sleep medicine team was also a key factor to ongoing adherence to therapy, as there was the opportunity to provide bedside education and promptly address the patient’s concerns. A collaborative approach by members of various subspecialties and by the multidisciplinary team allowed for improvement in other medical comorbidities, as well.


With an established diagnosis, the durable medical equipment (DME) provider received insurance reimbursement and supplied the patient with prescribed equipment. He was discharged home with treatment aimed to reduce his risk of decompensation. The patient was scheduled for a follow-up and a split overnight PSG at our sleep center. A follow-up phone call revealed that the patient’s health had remained stable and the initial bilevel PAP titration proved to be effective.


Diagnostic nocturnal polysomnography remains the gold standard for identifying and treating sleep-disordered breathing, such as OSA, especially in patients with complex comorbidities. However, the use of PM in the hospital setting can provide an effective alternative for the swift diagnosis of OSA when full polysomnography is unavailable and a patient is at an increased risk of decompensation post-discharge.

With the described multidisciplinary approach, we were able to determine an effective treatment option, which allowed for a prompt diagnosis, reduced time in the hospital, and met insurance requirements so the patient had immediate access to equipment upon discharge. Collaboration between medical services, nursing staff, respiratory care, and the sleep technologist is essential to successful use of PM in the hospital setting. PM is limited in that it does not determine the cause of respiratory failure; however, through collaboration with the pulmonary medicine team, it is possible to alternately determine the cause and optimize ongoing care. The inpatient team provides valuable information that is utilized with a type III portable monitor to facilitate a more complete diagnosis. Information includes lab tests, x-rays, and ongoing clinical monitoring. Type III PM provides useful information about the type of respiratory events (ie, central vs obstructive apnea), and this may influence ongoing treatment. In this case, the pulmonary team maximally titrated the patient by following various parameters including Pco2.

PM offers an effective inpatient short-term solution for diagnosis until a full (type I) polysomnogram titration can be performed. Research on the use of PM in the hospital setting is limited, especially in patients with comorbidities. Such patients will most likely still need a full polysomnogram for an optimal titration with positive airway pressure.

With increasing awareness of sleep apnea, outpatient polysomnography remains the gold standard for diagnosis and treatment of sleep apnea. The demand for inpatient sleep consultations, bedside polysomnography, and effective treatment options will continue to increase. Utilizing a collaborative approach among medical services and having effective alternate methods for extending scarce resources help to meet the needs of the institution and the individual.

Hassan Abouhouli, MD, is currently a sleep medicine fellow at the University of New Mexico and has completed fellowships in pulmonary and critical care medicine. He is actively involved in educational activities concerning the effects of sleep deprivation on residents and comparing the efficacy of inpatient sleep studies with formal outpatient sleep studies. Frank M. Ralls, MD, is an assistant professor of internal medicine and practices pediatric and adult sleep medicine, and geriatric medicine. He is program director for adult sleep medicine at the University of New Mexico Hospital Sleep Disorders Center. They can be reached at

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