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. 2017 Jun 1;40(6):zsx056.
doi: 10.1093/sleep/zsx056.

Therapeutic CPAP Level Predicts Upper Airway Collapsibility in Patients With Obstructive Sleep Apnea

Shane A Landry  1   2 , Simon A Joosten  3   4   5 , Danny J Eckert  6   7 , Amy S Jordan  6   8   9 , Scott A Sands  6   10 , David P White  6 , Atul Malhotra  6   11 , Andrew Wellman  6 , Garun S Hamilton  3   4   5 , Bradley A Edwards  1   2   6
Affiliations

Therapeutic CPAP Level Predicts Upper Airway Collapsibility in Patients With Obstructive Sleep Apnea

Shane A Landry et al. Sleep. .

Abstract

Study objectives: Upper airway collapsibility is a key determinant of obstructive sleep apnea (OSA) which can influence the efficacy of certain non-continuous positive airway pressure (CPAP) treatments for OSA. However, there is no simple way to measure this variable clinically. The present study aimed to develop a clinically implementable tool to evaluate the collapsibility of a patient's upper airway.

Methods: Collapsibility, as characterized by the passive pharyngeal critical closing pressure (Pcrit), was measured in 46 patients with OSA. Associations were investigated between Pcrit and data extracted from patient history and routine polysomnography, including CPAP titration.

Results: Therapeutic CPAP level, demonstrated the strongest relationship to Pcrit (r2=0.51, p < .001) of all the variables investigated including apnea-hypopnea index, body mass index, sex, and age. Patients with a mildly collapsible upper airway (Pcrit ≤ -2 cmH2O) had a lower therapeutic CPAP level (6.2 ± 0.6 vs. 10.3 ± 0.4 cmH2O, p < .001) compared to patients with more severe collapsibility (Pcrit > -2 cmH2O). A therapeutic CPAP level ≤8.0 cmH2O was sensitive (89%) and specific (84%) for detecting a mildly collapsible upper airway. When applied to the independent validation data set (n = 74), this threshold maintained high specificity (91%) but reduced sensitivity (75%).

Conclusions: Our data demonstrate that a patient's therapeutic CPAP requirement shares a strong predictive relationship with their Pcrit and may be used to accurately differentiate OSA patients with mild airway collapsibility from those with moderate-to-severe collapsibility. Although this relationship needs to be confirmed prospectively, our findings may provide clinicians with better understanding of an individual patient's OSA phenotype, which ultimately could assist in determining which patients are most likely to respond to non-CPAP therapies.

Keywords: CPAP; Obstructive sleep apnea; Pcrit; collapsibility; phenotyping.

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Figures

Figure 1
Figure 1
Univariate associations between Pcrit and body mass index (BMI), age, and sex. Neither (A) BMI (r2 = 0.07, p = .07), (B) age (r2 = 0.01, p = .44), nor (C) sex (r2 = 0.004, p = .66) were found to be significantly associated with Pcrit. Data from the development data set are shown..
Figure 2
Figure 2
Clinical predictors of Pcrit. Univariate linear regressions demonstrated (A) therapeutic CPAP level to be the strongest predictor of Pcrit (r2 = 0.51, p < .001) and to a lesser extent (B) apnea-hypopnea index (r2 = 0.19, p = .002). Data from the development data set are shown. CPAP = continuous positive airway pressure.
Figure 3
Figure 3
Comparison of therapeutic CPAP level between participants with mild upper airway collapsibility (Pcrit < −2 cmH2O, circles) and those with moderate-severe collapsibility (Pcrit > −2 cmH2O, triangles). Participants with Pcrit less than −2 cmH2O had a significantly lower therapeutic CPAP level (p < .001), with the majority (8/9) having a CPAP level less than 7 cmH2O. Interestingly, the five participants with a therapeutic CPAP level less than 7 cmH2O but were classed as having a more collapsible airway (Pcrit greater than −2), still had low, mostly negative Pcrit values (−1.53, −1.48, −0.69, −0.72, 0.64 cmH2O). Data from the development data set are shown. CPAP = continuous positive airway pressure.
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