Chest
Volume 120, Issue 3, September 2001, Pages 894-899
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Clinical Investigations
Sleep and Breathing
Nocturnal Hypoxemia Is Common in Primary Pulmonary Hypertension

https://doi.org/10.1378/chest.120.3.894Get rights and content

Abstract

Study objective

Unsuspected sleep-related respiratory events are common in patients with severe pulmonary disease. Sleep in patients with primary pulmonary hypertension (PPH) has not been studied (to our knowledge). The purpose of this study was to measure the prevalence of respiratory disturbances and nocturnal hypoxemia during the sleep of patients with PPH.

Setting

Tertiary-care referral hospital.

Design

Retrospective review.

Patients

Thirteen patients with PPH.

Measurements

All patients underwent a single-night comprehensive polysomnogram study. Patients who spent > 10% of the total sleep time with oxygen saturation by pulse oximetry (Spo2) at < 90% or who needed oxygen to maintain their Spo2 level at > 90% were classified as nocturnal desaturators. Analysis was performed to determine which clinical variables (ie, demographics, body mass index, spirometry, diffusion capacity, right heart catheterization pressures, 6-min walk test, arterial blood gas levels, resting and walking Spo2 levels, and polysomnogram variables) would predict nocturnal desaturation. Statistical significance was considered when p values were< 0.05.

Results

Of the 13 patients in the study, 10 (77%) were nocturnal desaturators. All patients had normal apnea indexes, but two had mild elevations of the hypopnea index (< 15 episodes per hour). Nocturnal desaturations occurred independently of apneas or hypopneas. Six patients who did not have O2 titration during sleep spent > 25% of sleep time with Spo2 < 90%. The mean (± SD) variables that were significantly different between desaturators (10 patients) and nondesaturators (3 patients) were FEV1 (70.1 ± 9.1% predicted vs 98.1 ± 15.1% predicted, respectively; p = 0.002), resting Pao2 (61.8 ± 16.1 vs 90.3 ± 2.3 mm Hg, respectively; p = 0.001), alveolar-arterial oxygen pressure difference (P[A-a]O2) (40.5 ± 20.5 vs 12.2 ± 7.2 mm Hg, respectively; p = 0.048), resting Spo2 (91.6 ± 5.4% vs 98.7 ± 2.3%, respectively; p = 0.038), and walking Spo2 (83.8 ± 9.3% vs 95.3 ± 1.2%, respectively; p = 0.002). The mean hemoglobin level was higher in the group of nocturnal desaturators than in the group of nondesaturators (10.43 ± 0.31 vs 13.95 ± 0.98 g/dL, respectively; p < 0.0001).

Conclusion

Seventy-seven percent of patients with PPH have significant nocturnal hypoxemia that is unrelated to apneas and hypopneas. Nocturnal desaturation occurs more frequently in patients with higher P(A-a)O2 values and lower FEV1 values, resting arterial Pao2 and Spo2 values, and walking Spo2 values.

Section snippets

Materials and Methods

Patients with PPH who underwent a comprehensive polysomnogram study (polysomnography) in our institution were included in the study. Pulmonary hypertension was confirmed by right heart catheterization and was defined as a mean pulmonary artery pressure of > 25 mm Hg at rest or > 30 mm Hg during exercise. PPH was diagnosed according to the standard criteria provided by the National Registry of Primary Pulmonary Hypertension1 in 30 patients evaluated by one of the authors (A.C.A.). In brief,

Results

We studied 13 patients with PPH (12 women and 1 man) with a mean age of 44.7 ± 18.2 years and a mean BMI of 30.1 ± 7.3 kg/m2. Other characteristics are shown in Table 1. Three patients were receiving daytime resting oxygen supplementation, and six patients needed oxygen only when walking.

Our patients slept an average of 297.0 ± 48.1 min, with REM sleep making up 13 ± 5.3% of TST (Table 1). Snoring was noted in 85% of patients. All study patients had a normal apnea index (ie,< 5 episodes per

Discussion

The most important finding of the study is that 77% of the patients with PPH had significant nocturnal hypoxemia. Severe oxygen desaturation occurred independently of the presence of apneas or hypopneas. This study is important as well because it suggests that monitoring nocturnal oxygen saturation might be beneficial for patients with PPH.

Nocturnal hypoxemia occurred in 77% of our study population, and all nocturnal desaturators who did not undergo oxygen titration spent> 25% TST-Spo2 < 90%.

Conclusion

A high percentage of patients with PPH have significant nocturnal hypoxemia that is unrelated to apneas and hypopneas. Nocturnal desaturation occurs more frequently in patients with higher P(A-a)O2 values and lower FEV1, resting arterial Pao2 and Spo2, and walking Spo2 values.

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