Study objective: Unsuspected sleep-related respiratory events are common in
patients with severe pulmonary disease. Sleep in patients with primary pul
monary hypertension (PPH) has not been studied (to our knowledge). The purp
ose 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 polysomno
gram study. Patients who spent > 10% of the total sleep time with oxygen sa
turation by pulse oximetry (Spo(2)) at < 90% or who needed oxygen to mainta
in their Spo(2) level at > 90% were classified as nocturnal desaturators. A
nalysis was performed to determine which clinical variables (ie, demographi
cs, body mass index, spirometry, diffusion capacity, right heart catheteriz
ation pressures, 6-min walk test, arterial blood gas levels, resting and wa
lking Spot levels, and polysomnogram variables) would predict nocturnal des
aturation. Statistical significance was considered when p values were < 0.0
5.
Results: Of the 13 patients in the study, 10 (77%) were nocturnal desaturat
ors. All patients had normal apnea indexes, but two had mild elevations of
the hypopnea index (< 15 episodes per hour). Nocturnal desaturations occurr
ed independently of apneas or hypopneas. Six patients who did not have O-2
titration during sleep spent > 25% of sleep time with Spo(2) < 90%. The mea
n ( SD) variables that were significantly different between desaturators (1
0 patients) and nondesaturators (3 patients) were FEV1 (70.1 +/- 9.1% predi
cted vs 98.1 +/- 15.1% predicted, respectively; p = 0.002), resting Pao(2)
(61.8 +/- 16.1 vs 90.3 +/- 2.3 inm Hg, respectively; p = 0.001), alveolar-a
rterial oxygen pressure difference (P[A-a]O-2) (40.5 +/- 20.5 vs 12.2 +/- 7
.2 mm Hg, respectively; p = 0.048), resting Spo(2) (91.6 +/- 5.4% vs 98.7 /- 2.3%, respectively; p = 0.038), and walking Spo(2) (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 noc
turnal hypoxeinia that is unrelated to apneas and hypopneas. Nocturnal desa
turation occurs more frequently in patients with higher P(A-a)O-2 values an
d lower FEV1 values, resting arterial Pao(2) and Spot values, and walking S
po(2) values.