Title: Chronic Obstructive Pulmonary Disease and Sleep
1Chronic Obstructive Pulmonary Disease and Sleep
- AWAKE Meeting
- February 4, 2009
- Anstella Robinson, MD FCCP FAASM
2Introduction
- Respiratory changes during sleep exacerbate gas
exchange abnormalities present in those with
COPD. Subsequent hypoxemia may predispose to
secondary pulmonary hypertension, heart
arrhythmias and premature death. More than 40
of COPD patients complain of sleep disturbances
including reduced sleep time and increased
arousals.
3Introduction contd
- COPD patients complain of more daytime sleepiness
than those without respiratory disease although
the effects of this on daytime function and
quality of life have not been studied.
4Respiratory changes during sleep
- During sleep the metabolic rate diminishes.
Respiratory responses to chemical mechanical and
cortical inputs are reduced. Increased partial
pressure of carbon dioxide is a physiological
response to sleep as is a reduced partial
pressure of arterial blood oxygen. Reduced tidal
volume and minute ventilation are also natural
consequences of sleeping.
5How respiratory function during sleep differs in
COPD
- Normal sleep related respiratory changes can be
deleterious for those with COPD as they may lead
to reduced gas exchange and ultimately
hypoventilation, hypoxemia and hypercapnia
particularly in REM sleep where muscle atonia is
the rule. Hypercapnia may lead to a further
reduction of diaphragmatic contractility and
ventilatory responsiveness.
6How Respiratory function during sleep differs in
COPD Contd
- Hypoxia may provoke an arousal response although
this effect varies widely. Patients may continue
to sleep with significantly impaired oxygen
levels. Women have an increased responsiveness
to hypoxemic effects. Impaired respiratory
muscle activity in COPD patients also effects
breathing during sleep. Increases in airway
resistance may cause exaggerated
broncoconstriction that may be clinically
significant.
7How Respiratory function during sleep differs in
COPD Contd
- Reduced intercostal muscle activity also affects
breathing during sleep in those with impaired
diaphragmatic contraction secondary to
hyperinflation who may be more dependent on
accessory muscle function in order to maintain
ventilation. Hypoxemia and hypercapnia during
sleep are probably related to hypoventilation in
patients with reduced respiratory function
8How Respiratory function during sleep differs in
COPD Contd
- Arterial oxygen desaturation during sleep is due
in mainly to ventilation perfusion mismatch.
Lung volume changes that occur in sleep include a
reduction in functional residual capacity. This
change may lead to ventilation perfusion mismatch
and significant hypoxemia in patients with COPD.
9How Respiratory function during sleep differs in
COPD Contd
- Reduced FRC is due to
- Respiratory muscle hypotonia
- Diaphragmatic displacement when the patient is
lying recumbent - Decreased lung adherence during sleep
10Which COPD Patients Desaturate during sleep and
why?
- The degree of arterial oxygen desaturation
correlates poorly with measures of pulmonary
function such as FEV1. arterial oxygen saturation
while awake is considered to be the best
predictor of sleep desaturation in patients with
COPD. Patients with chronic bronchitis (so
called blue bloaters) have the best correlation
between awake arterial oxygen saturation and
minimum arterial oxygen saturation during sleep.
11Which COPD Patients Desaturate during sleep and
why?
- Patients who are hypoxemic while awake are
typically treated with supplemental oxygen.
However those whose arterial oxygen saturations
are borderline while awake and who do not meet
criteria for supplemental oxygen may develop
clinically significant hypoxemia while asleep.
12Which COPD Patients Desaturate during sleep and
why?
- Fletcher and colleagues evaluated gas exchange
and cardiopulmonary hemodynamics in a group of
COPD patients with borderline oxygen
desaturations PaO2 gt60mmHg who had significant
nocturnal oxyhemoglobin desaturation (NOD) and
compared them to patients with similar pulmonary
hemodynamics but no NOD
13Which COPD Patients Desaturate during sleep and
why?
- These investigators found
- PaO2 was approximately 12mmHg lower in those with
NOD compared to those without NOD. - Arterial/alveolar oxygen tension ratios were more
abnormal in those with NOD compared to those
without NOD
14Which COPD Patients Desaturate during sleep and
why?
- Greater arterial oxygen desaturation occurs
during sleep than in maximal exercise with a
different mechanism. Awake PaO2 at rest has been
found to be a better predictor of sleep arterial
oxygen desaturation than exercise arterial
desaturation. However awake PaCO2 has not been
shown as an independent predictor of NOD.
15Coexistent COPD and OSAS (overlap Syndrome)
- Epidemiologic studies show that contrary to what
one might expect, the prevalence of OSAS in COPD
patients is similar to that in an age matched
population without COPD. - Coexistent COPD and OSAS is associated with more
severe hypoxemia during sleep.
16Coexistent COPD and OSAS (overlap Syndrome)
- Mean SaO2 is lower in patients with COPD and OSAS
and the time spent in desaturation is longer than
those with OSAS alone. Most patients with OSAS
tend to resaturatre to normal SaO2 levels between
apneas while those with coexistent COPD may be
more hypoxemic at the start of the apnea.
17Coexistent COPD and OSAS (overlap Syndrome)
- Thus those with coexistent COPD and OSAS are
particularly prone to complications of hypoxemia
such as cor pulmonale. Although early research
on sleep in COPD had a selection bias towards
those individuals who sought attention for a
sleep disorder the Sleep Heart Health Study
sought to correct this bias by
18Coexistent COPD and OSAS (overlap Syndrome)
- Examining the relationship between COPD and OSAS
in a large community population of 1132
participants with predominantly mild COPD who did
not seek treatment for a sleep disorder. The
investigation concluded that comorbid COPD and
OSAS occurred by chance and that a common
pathophysiological link was unlikely although an
FEV1/FVC ratio lt65 was associated with an
increased risk of arterial oxygen desaturation
during sleep. Greater in patients with COPD and
OSAS than in those with either disorder alone.
19Cardiac arrhythmias
- In chronic bronchitis patients with basal SaO2
lt80 studies show multiple atrial and ventricular
premature contractions as well as other
abnormalities. Thus sustained hypoxemia
contributes to myocardial dysfunction and heart
failure in this subset of patients with COPD.
20Mortality
- Are patients with COPD more likely to die in
their sleep? - Some studies suggest that prolonged arterial
oxygen desaturation during sleep increases the
risk of death, especially during exacerbations of
COPD.
21Mortality
- In a study by Fletcher et al 169 patients with
COPD and daytime PaO2 gt60 mmHG were compared to
patients with and without NOD. The NOD was
further characterized as episodic ( desaturation
occurring mainly in REM sleep) or nonepisodic
SaO2 lt90 during gt30 of time in bed. At median
follow up of 3.4 years - Mortality rated were significantly higher among
patients with NOD.
22Conclusions
- COPD management must be individualized to each
patient especially with respect to sleep quality
and the degree to which COPD sufferers are
affected by changes in respiratory physiology. It
is important to perform a sleep history in COPD
patients as a normal sleep pattern for them might
actually suggest recurrent nocturnal awakenings
due to hypercapnia or significant excessive
daytime sleepiness.
23Conclusions Contd
- Many patients believe that excessive daytime
sleepiness is a normal part of aging when it may,
in fact, be part of a treatable condition. Sleep
studies monitor a number of respiratory and
neurologic variables and can yield valuable
information in patients with COPD. Despite new
research it is unclear how to treat hypoxemia and
hypercapnia in patients with normal or borderline
daytime oxygen. - Coexistent OSAS should be considered in COPD
patients with snoring or excessive daytime
sleepiness.
24References
- Fletcher EC, Luckett RA, Miller T et al Pulmonary
vascular hemodynamics in chronic lung disease
patients with and without sleep related oxygen
desaturation during sleep. Chest 1989
95757-764. - Sanders MH Newman AB, Hagerty CL et al. For the
sleep heart health study sleep and sleep
disordered breathing in adults with predominantly
mild obstructive airway disease. Am J Respir Crit
Care Med 2003 1677-14. - Fleetham JA, Wandersee K. Tosleep perchance to
breathe How sleep affects patients with COPD.
Trends and Reviews in COPD 2008 2 4-11.