Today, I review, link to, and excerpt from Oximetry Monitoring Recommended During PAP Initiation for Sleep Apnea in Patients With Obesity or Nocturnal Hypoxemia [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. J Clin Sleep Med. 2018 Nov 15;14(11):1859-1863. doi: 10.5664/jcsm.7480.
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ABSTRACT
Study Objectives:
No consensus exists regarding monitoring the initiation of positive airway pressure (PAP) by oximetry. A PAP device report may be insufficient to ensure a good therapeutic response in all patients. This study aimed to identify patients who would potentially benefit from oximetry monitoring during PAP initiation.
Methods:
PAP initiation was routinely monitored at home with an oximeter. Data were reviewed for all patients who underwent PAP initiation in 2015, including a baseline sleep study and PAP initiation data. Group A included patients with an apnea-hypopnea index as determined from the PAP device (AHIPAP) of < 5 events/h and a residual 3% oxygen desaturation index (ODI3) of ≥ 10 events/h.* Group B included all remaining patients. Cases with a leak of over 24 L/min or with an oximetry recording time of < 1 hour were excluded. AHIPAP < 5 events/h and residual ODI3 < 10 events/h* represented good PAP responses.
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ODI3, or the 3% oxygen desaturation index, measures how often and by how much your blood oxygen levels drop during sleep, aiding in the diagnosis and management of obstructive sleep apnea (OSA).
Here’s a more detailed explanation:
ODI3 refers to the number of times per hour your blood oxygen saturation (SpO2) drops by 3% or more during sleep, as measured by a pulse oximeter.
- Diagnosis: A higher ODI3 value suggests more frequent and deeper oxygen desaturations, which can be an indicator of OSA.
- Severity Assessment: ODI3 can help assess the severity of OSA, with higher values indicating more severe cases.
- Treatment Monitoring: ODI3 can be used to monitor the effectiveness of OSA treatments, such as CPAP therapy.
ODI3 is typically measured during an overnight pulse oximetry study, where a finger or ear clip monitors your blood oxygen levels while you sleep.
- Normal: A normal ODI3 is generally considered to be 0-5 events per hour.
- Mild OSA: ODI3 values between 5 and 15 events per hour may indicate mild OSA.
- Moderate OSA: ODI3 values between 15 and 30 events per hour may indicate moderate OSA.
- Severe OSA: ODI3 values above 30 events per hour may indicate severe OSA.
While the Apnea-Hypopnea Index (AHI) is the primary measurement for diagnosing OSA, your doctor may also review ODI3 to better understand the severity of your OSA.
ODI3 may not be as accurate as polysomnography (PSG) for diagnosing OSA, especially in individuals with mild OSA
Resuming Oximetry Monitoring Recommended During PAP Initiation for Sleep Apnea in Patients With Obesity or Nocturnal Hypoxemia
Results:
From 787 patients, 723 were included in this study. Among these, 158 had an AHIPAP of ≥ 5 events/h, whereas 565 had an AHIPAP of < 5 events/h. Group A consisted of 129 patients (18%). The sensitivity of the PAP device indicating a good PAP response reached 93.1%, with a specificity of 37.2%, a negative predictive value of 96.2%, and a positive predictive value of 23.9% using body mass index (BMI) ≥ 30 kg/m2 and baseline SpO2 < 92% as the cutoff points.
Conclusions:
Relying only on the PAP device parameter to evaluate therapeutic responses provided inconsistent results in one-fifth of cases. Thus, oximetry monitoring during PAP initiation is recommended when baseline SpO2 < 92% or when BMI ≥ 30 kg/m2. Otherwise, oximetry monitoring remains optional.
Citation:
Koivumäki V, Maasilta P, Bachour A. Oximetry monitoring recommended during pap initiation for sleep apnea in patients with obesity or nocturnal hypoxemia. J Clin Sleep Med. 2018;14(11):1859–1863.
BRIEF SUMMARY
Current Knowledge/Study Rationale: Polysomnography represents the gold standard for positive airway pressure (PAP) therapy initiation. This practice is rare and more often the therapy control relies on the self-monitoring of the PAP device.
Study Impact: Oximetry should be part of PAP initiation among patients with obesity and those with low oxygen values during sleep because relying only on PAP device monitoring is unreliable. Oximetry monitoring identified patients who need additional examination to ensure a good PAP therapy response.
INTRODUCTION
Continuous positive airway pressure (CPAP) is a standard treatment for patients with obstructive sleep apnea (OSA), a sleep-related breathing disorder characterized by full or partial occlusion of the upper airway during sleep. The gold standard for CPAP initiation occurs during polysomnography.1 Auto-titrating positive airway pressure (APAP) has been used for titration and OSA therapy, and appears to be as efficient as CPAP when following the application rules.2 Meanwhile, no recommendation exists for monitoring positive airway pressure (PAP) initiation other than via polysomnography. Some sleep centers continue to use in-laboratory PAP initiation monitored by polysomnography, whereas other centers depend primarily on PAP device values.3
PAP devices have undergone considerable technological advances recently, notably in the field of remote medicine. These new devices have reduced the cost of PAP initiation and allowed for the more efficient monitoring of therapy.3 By contrast, the use of polygraphy or oximetry during PAP initiation in remote medicine remains under development.
Although a PAP device has been validated for detecting the apnea-hypopnea index (AHI)4 its criteria for calculating hypopnea differs from recommendations from the American Academy of Sleep Medicine (AASM).5,6 Recently, Thomas and Bianchi7 presented remarkable findings, whereby PAP device algorithms missed the detection of respiratory events. Accordingly, the authors have concerns regarding the reliability of the PAP device in estimating AHI values. In essence, although scoring apnea without oximetry is possible, hypopneas rely on arousals or oximetry values. A PAP device alone provides none of these parameters.7
It is of utmost importance to simplify PAP initiation at home while maintaining good therapeutic control because an increasing emphasis has been placed on appropriate resource utilization—including efforts aimed at decreasing the cost of care—and to cope with the increasing number of patients seeking treatment for sleep disorders. Our clinical experience allows us to conclude that the apnea-hypopnea index reported by a PAP device (AHIPAP) is not trustworthy among a specific group of patients. Therefore, the PAP therapeutic response must be monitored using additional tools such as oximetry.
This study aims to identify groups of patients who may benefit most from the addition of oximetry in monitoring PAP initiation. Patients with normal AHIPAP but abnormal oximetry results manifested through a high 3% oxygen desaturation index (ODI3) were analyzed.
METHODS
Data were collected from all patients referred to our sleep unit for PAP initiation for OSA during 2015. The indication for PAP initiation was a respiratory event index (REI) of ≥ 5 events/h associated with significant daytime sleepiness or the presence of cardiovascular or metabolic comorbidity. Patients with a REI of ≥ 15 events/h were also recommended for PAP therapy regardless of their symptoms or comorbidity. Patients with a central sleep apnea or obesity hypoventilation syndrome were excluded. The sleep apnea diagnosis was confirmed by an outof-center type III sleep study and scoring was performed in accordance with prevailing AASM guidelines.8 Hypopnea was defined as a decrease in the nasal flow of at least 50% for at least 10 seconds or a decrease of at least 3% in the saturation.5
PAP therapy was initiated at home with an APAP device (ResMed, Sydney, Australia). An oximeter (Nonin Xpod, Nonin Medical Inc. Minneapolis, Minnesota, United States) was connected and data were synchronized with the PAP device. The pressure was set to start automatically from 4 cmH2O up to a maximum of 20 cmH2O.
Oximetry data were visually checked and only oximetry data during “PAP On” were included. This is feasible as the ResScan program allows a simultaneous check of airflow, PAP pressure, and oximetry. The baseline SpO2 value represented the mean oximetry value during the cardiorespiratory sleep study (out-of-center type III sleep study).
Patients were excluded if they fulfilled one of the following: a recording time with an oximeter “when PAP was on” of less than 1 hour or a median air leak of more than 24 L/min. Although we considered an AHIPAP of < 5 events/h as normal, it is also reasonable to consider an ODI3 value of < 5 events/h as normal. When analyzing the data, we noticed a large overlap between the two groups. To reduce this overlap and increase the value of the abnormal ODI3, we considered an ODI3 value of ≥ 10 events/h as abnormal. We found no previous studies on this issue in the literature.
A good PAP therapeutic response was indicated when AHIPAP < 5 events/h. Furthermore, a good PAP and oximetry therapeutic response was considered when AHIPAP < 5 events/h and residual ODI3 < 10 events/h. In our analysis, we divided our patients into two groups based on their AHIPAP values and on the residual ODI3 values. As such, group A consisted of patients with AHIPAP < 5 events/h and residual ODI3 ≥ 10 events/h. Group B included all the remaining patients.
We used the age-adjusted Charlson Comorbidity Index* to evaluate comorbidity. This index consists of 19 medical conditions weighted 1 to 6 with total scores ranging from 0 to 37 (0 = no comorbidity).10
*Charlson Comorbidity Index: A Critical Review of Clinimetric Properties [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Psychother Psychosom. 2022;91(1):8-35. doi: 10.1159/000521288. Epub 2022 Jan 6.
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RESULTS
A total of 948 patients were scheduled to undergo PAP initiation (Figure 1). Among these, 12 were no-shows, and oximetry was not available for 149 patients. We analyzed data for a total of 787 patients who received oximetry during PAP initiation. Among these, 36 had a PAP time with oximetry of less than 1 hour and were excluded from the analysis. We also excluded 28 patients who presented with a median leak of more than 24 L/min. Thus, the final analysis included 723 patients; their PAP time was a mean of 7:10 hours:minutes, standard deviation (SD) 2:13. The characteristics of these patients are outlined in Table 1.
Figure 1: Flowchart of all patients.
ODI3 = 3% oxygen desaturation index, PAP = positive airway pressure, REI = respiratory event index.
A total of 565 patients had an AHIPAP of < 5 events/h, whereas 158 patients (22%) showed an AHIPAP of ≥ 5 events/h. Among patients with an AHIPAP of < 5 events/h, 129 patients had a residual ODI3 of ≥ 10 events/h (group A, 18% of all patients). Group A, therefore, included patients classified as having a good therapeutic response using the PAP device (false positive), but an abnormal residual ODI3.
To evaluate the variation in baseline SpO2 and BMI [Start here]
