Predicting CPAP failure in patients with suspected sleep hypoventilation identified on ambulatory testing

Abstract

Study Objectives: Home sleep apnea testing (HSAT) is commonly used to diagnose obstructive sleep apnea, but its role in identifying patients with suspected hypoventilation or predicting their response to continuous positive airway pressure (CPAP) therapy has not been assessed. The primary objective was to determine if HSAT, combined with clinical variables, could predict the failure of CPAP to correct nocturnal hypoxemia during polysomnography in a population with suspected hypoventilation. Secondary objectives were to determine if HSAT and clinical parameters could predict awake or sleep hypoventilation. Methods: A retrospective review was performed of 142 consecutive patients who underwent split-night polysomnography for suspected hypoventilation after clinical assessment by a sleep physician and review of HSAT. We collected quantitative indices of nocturnal hypoxemia, patient demographics, medications, pulmonary function tests, as well as arterial blood gas data from the night of the polysomnography. CPAP failure was defined as persistent obstructive sleep apnea, hypoxemia (oxygen saturation measured by pulse oximetry < 85%), or hypercapnia despite maximal CPAP. Results: Failure of CPAP was predicted by awake oxygen saturation and arterial blood gas results but not by HSAT indices of nocturnal hypoxemia. Awake oxygen saturation ≥ 94% ruled out CPAP failure, and partial pressure of oxygen measured by arterial blood gas ≥ 68 mmHg decreased the likelihood of CPAP failure significantly. Conclusions: In patients with suspected hypoventilation based on clinical review and HSAT interpretation by a sleep physician, awake oxygen saturation measured by pulse oximetry and partial pressure of oxygen measured by arterial blood gas can reliably identify patients in whom CPAP is likely to fail. Additional research is required to determine the role of HSAT in the identification and treatment of patients with hypoventilation.

Ventilation Strategies in Obese Patients

“…• Insufficient improvement of oxygen saturation on CPAP: ○ Oxygen saturation below 90% for more than 20% of total sleep despite adequate abolition of apneas and hypopneas [36] ○ Oxygen saturation < 85% or hypercapnia despite maximal CPAP [37] ○ Oxygen saturation below 90% for more than 30% of titration night [38] ○ Oxygen desaturation < 80% over 10 min [9] • Persistence of apneic and hypopneic episodes [37] • Insufficient improvement of CO 2 levels ○ ≥5 min-long increase in nocturnal PTcCO 2 > 55 mm Hg and in PaCO 2 ≥ 10 mm Hg compared to the awake state [9] ○ Daytime PaCO 2 > 45 mm Hg [38] The choice of criteria for CPAP failure should be suited for the practice of a particular sleep laboratory, and it should be consistent over time.…”

“…• awake oxygen saturation < 94% and PaO 2 < 68 mm Hg [37] • daytime PaCO 2 > 53 mm Hg [15] • BMI ≥ 50 kg m −2 [15,39] • significant comorbidities [40] • acute respiratory failure [39] • and clinician's preference [39] Generally, worse blood gases [38], higher obesity, significant comorbidities, and clinician's preference warrant the trial of NIV in the first step.…”