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.
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