*From the Western Reserve Care System (Dr. Acharya), Youngstown, OH; and the Northeastern Ohio Universities College of Medicine (Dr. Kartan), Rootstown, OH.
Correspondence to: Ritha Kartan, MD, FCCP, Department of Research, Western Reserve Care System, 500 Gypsy Lane, Youngstown, OH 44501
Platypnea-orthodeoxia is an uncommon syndrome that may
occur due to the postpneumonectomy state, cirrhosis of the liver,
recurrent pulmonary embolism, and intracardiac shunting. We describe a
patient who was found to have a positional change in desaturation after
being admitted for dehydration. Workup revealed an atrial septal defect
with aneurysm. Following surgical repair, the orthodeoxia resolved.
Different mechanisms explain positional desaturation, such as
atriovenous malformations at the lung base of cirrhotic patients. In an
atrial septal defect, the increased shunting of blood across a
malformed septum in an upright position may cause orthodeoxia. This
case highlights the necessity of heightened awareness of this syndrome
and the need for documenting orthostatic changes in cases of severe
is a rare, poorly understood clinical syndrome in which arterial
desaturation is accentuated in upright posture and relieved by
recumbent position. This is commonly associated with hyperventilation
in the upright position, referred to as platypnea. It is commonly
described in patients with chronic lung diseases.
We discuss the case of a patient who exhibited orthodeoxia in the
absence of demonstrable lung disease. Extensive workup led to the
diagnosis of atrial septal defect with an aneurysm that was surgically
repaired, causing the orthodeoxia to cease.
A 71-year-old, mentally retarded male patient presented with
generalized weakness. He denied having chest pain, shortness of breath,
or fever. His medical history was only significant for hypertension.
There was no history of industrial inhalation, toxic drug exposure, or
tobacco abuse. Physical examination revealed a dehydrated
man with poor skin turgor but no evidence of pedal edema, cyanosis,
clubbing, or telangiectasia. Orthostatic BP changes were noted. Lung
and heart sounds were normal, without audible cardiac murmurs.
Laboratory findings were consistent with dehydration.
During hospitalization, nurses observed the patient sitting up in bed
talking, then slumping over and becoming cyanotic. Monitors showed no
rhythm abnormalities. His heart rate was 80 regular beats/min, and BP
was 90/70 mm Hg with spontaneous respiration. When he was placed
supine, his condition dramatically improved.
Arterial blood gas measurements revealed an oxygen saturation of 84%
and Po2 of 50 mm Hg while the patient
breathed room air. While breathing 100% oxygen by nonrebreather
facemask, oxygen saturation increased to 89% and the
Po2 to 53 mm Hg. ECG detected a sinus
rhythm with right bundle branch block. Chest radiographs
demonstrated clear lung fields with a normal cardiovascular silhouette.
Bilateral lower extremity venous ultrasounds revealed compressible
patent deep veins. A ventilation perfusion lung scan was read as low
probability for pulmonary embolism. A high-resolution CT scan revealed
the lungs were normal. The diagnosis of pulmonary embolism was further
ruled out by a pulmonary angiogram that showed normal pulmonary
pressures at 22/10 mm Hg (mean, 14 mm Hg) and good filling
of the left and right pulmonary arteries. There was no evidence of
filling defects, occlusions, or vascular cutoffs. A transthoracic
echocardiogram did not reveal any septal defects and estimated the left
ventricular ejection fraction at 60%. It showed a markedly dilated
left atrium at 5.5 cm in diameter and a dilated right ventricle 4.6 cm
in diameter with preserved contractility.
The orthostatic nature of the desaturation was again documented with
arterial blood studies while the patient was receiving 100% oxygen by
nonrebreather facemask. In supine position, the
Po2 level was 99 mm Hg and the oxygen
saturation rate was 97%; while sitting, the
Po2 dropped to 38 mm Hg and oxygen
saturation to 75%. A transesophageal echocardiogram (TEE) disclosed a
probable fenestrated atrial septum with an aneurysm and a bidirectional
shunting that was confirmed by cardiac catheterization in supine
The 3 × 3-cm defect was surgically repaired. Postoperative TEE
did not show any evidence of shunting. The patient experienced an
uneventful recovery and cessation of orthodeoxia.
Platypnea-orthodeoxia is most commonly recognized in patients with
a history of a major pulmonary disorders such as emphysema, recurrent
pulmonary embolism, ARDS,1pulmonary atriovenous
malformations,2–3 post- pneumectomy,4–9
hepatopulmonary syndromes, or cirrhosis of liver.10–11 It
is rarely reported in the absence of overt pulmonary
Alveolar pressures are uniformly distributed throughout the normal
lung. Blood flow depends on the vascular pressure in the different
regions of the lung. When in the upright position, blood flow
increases from the apex of the lung to the base as gravity causes
vascular pressures to be lower at the apex. Patients with chronic lung
disease have a parenchymal pulmonary cause of physiologic shunting. In
these patients, elevated alveolar pressures alter the ventilatory
mechanics by causing pulmonary capillary compression and cessation of
blood flow. This has been described as the zone 1
phenomenon.15 The phenomenon is accentuated in the apical
lung portions on assumption of an upright posture with gravitational
drop in pulmonary artery pressure. The combination of the two effects
could produce a substantial compromise of regional blood flow. These
regions are ventilated but underperfused, resulting in respiratory dead
space. The increased dead space causes tachypnea and/or dyspnea that
further augments air trapping. Alveolar pressures again elevate,
creating a repetitive cycle.
Development of platypnea in a postpneumonectomy state should raise the
suspicion of the presence of a right to left interatrial
shunt.4–9 This may develop because of relative change
in the positions of the two atria or mechanical distortion of the fossa
ovalis by an upright position. The streaming of the blood flow may be
aided by the fact that after pneumonectomy, the interatrial septum
would be displaced more to the right, causing the inferior vena cava
orifice to become closer to the septal defect.9 Another
probable mechanism to consider is that an increase in the pulmonary
vascular resistance after reduction in the pulmonary vascular bed
causes an elevation of right ventricular end-diastolic
pressures.11 This, in turn, decreases right ventricular
compliance and elevates right atrial pressures. Trepopnea, dyspnea in
the lateral position, is more common after pneumonectomy or right
middle/lower lobectomy.16Constrictive pericarditis in a
patient who had undergone pneumonectomy has also been reported as
causing orthostatic dyspnea.17
Platypnea-orthodeoxia is well documented and better understood in
patients with cirrhosis of the liver or hepatopulmonary
syndrome.10–11 When the patient is standing, blood flow
follows gravity to the base of the lung, which has true anatomic
intrapulmonary vascular dilatations.3 It is further
postulated that these abnormally dilated capillary blood vessels at the
lung bases are situated far away from the alveolar epithelium. This
decreases the oxygenation of the blood in these segments, which become
more intensified in an upright position. A circulating vasodilator that
is either produced by or not cleared by the damaged liver may also
exist.11 This vasodilator is thought to be responsible for
causing intrapulmonary vascular dilatations.
Many patients with platypnea are found to have normal pulmonary artery
pressures.4 The mechanism of development and marked
positional variation in the right to left shunting in such cases is
poorly understood. Transient right to left interatrial instantaneous
pressure gradient during isovolumic ventricular contraction may cause a
small right to left shunt.18–19 During the phases of the
cardiac cycle, the left atrial pressure is generally greater than the
right. Early ventricular systole causes a slightly greater right atrial
pressure. The interatrial pressure difference is
intensified in states that increase the systemic venous return, similar
to the release phase of the Valsalva maneuver, or during inspiration.
The pooling of pulmonary blood due to decreased intrathoracic pressure
in these states accentuates the shunt. “Flow phenomenon” may be
another mechanism for platypnea. The preferential flow of blood from
the inferior vena cava is directed toward the foramen ovale, as is the
case in the prenatal circulatory path.12–13 Some patients
exhibit an abnormally large eustachian valve at the junction of the
right atrium and inferior vena cava, which causes selective directional
shunting, despite normal atrial pressures.6,12–13
Other possible mechanisms to explain shunting in the absence of
elevated right heart pressures have been reported. One theory suggests
that when an atrial septal defect is present, shunting occurs from the
less compliant or stiffer chamber into the more compliant
chamber.4,6 When standing, there is a drop in the right
ventricular filling pressures, making the left ventricle relatively
more compliant while maintaining right ventricular compliance. In
addition, during early diastole, the compliance of the right ventricle
is reduced, thus offering greater resistance to blood flow from the
right atrium. This leads to enhancement of the shunting across the
septal defect without elevation of the right heart pressures. Reduction
of intravascular volume can change the right ventricular compliance and
cardiac output, thereby increasing the right to left
In the case described herein, the patient had an atrial septal defect
with an aneurysm. Atrial septal aneurysm formation results from
redundancy of the valve of the foramen ovale. The defective septum
secundum billows outward to intercept the venous inflow, and the blood
is then shunted directly across the opening in the septum. We postulate
that due to the dehydrated state, the shunting became even more
prominent (Fig 1
). Severe kyphosis, aortic root enlargement, and nitrate therapy can
also cause the septum secundum to fall away from the primum, thus
worsening the shunt.5
Incidences of platypnea-orthodeoxia have also been described in
patients with acute organophosphorous poisoning,20–
amiodarone-induced lung toxicity,21 bronchogenic or
laryngeal carcinoma,23–24 cryptogenic fibrosing
alveolitis,25or autonomic nervous system
dysfunction.26An elongated ectatic aorta27–
and an aortic aneurysm28 have also been reported to cause
Most cases of platypnea/orthodeoxia described in the literature have
been corrected with surgical correction of the shunt, as occurred with
our patient. Other treatments for orthodeoxia include prednisone for
pericardial effusion following coronary artery bypass graft, and opiate
therapy in elderly patients.14 Treatment with almitrine
bismesylate has been shown to potentiate the normal pulmonary hypoxic
vasoconstriction, thereby reducing the development of respiratory dead
During the administration of TEE in the supine position, we
observed an atrial septal aneurysm coexisting with an atrial septal
defect. We suspect upright posture worsened the shunt. Dehydration
exacerbated the shunt leading to its discovery.
Greater awareness of orthodeoxia and the necessity of documenting
orthostatic changes in saturation levels in all cases of severe
hypoxemia are urged. Orthostatic desaturation should prompt further
workup and facilitate early recognition of potentially treatable
causes. TEE is the ideal technique for septum evaluation and diagnosis
of platypnea-orthodeoxia.30 The presence of an atrial
septal defect or a patent foramen ovale should warrant prompt closure
to prevent the development of ischemic strokes due to paradoxical
Abbreviation: TEE = transesophageal
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