O7. Aggravating factors
O7.1 Aspiration
Aspiration of food and liquid is
common in COPD and may be the cause
of recurrent exacerbations and
complications, such as pneumonia and
patchy pulmonary fibrosis.
Diagnosis is usually easy with an
adequate history from patients and
their partners or carers. Dry
biscuits and thin fluids cause the
most difficulty. Confirmation
rests with assessment by a speech
therapist/ pathologist and videofluoroscopy.
Treatment involves retraining in
safe swallowing techniques, which
may include:
O7.2 Gastro-oesophageal reflux
In patients with COPD,
hyperinflation, coughing and the
increased negative intrathoracic
pressures of inspiration may
predispose to reflux, especially
during recumbency and sleep.
A cross-sectional
questionnaire-based study found an
increased rate of gastro-oesophageal
reflux was associated with increased
COPD exacerbations112
but this finding has not been
addressed prospectively. Microaspiration of oesophageal
secretions (possibly including
refluxed gastric content) is a risk,
especially with coexistent snoring
or OSA. Reflux and microaspiration
exacerbate cough, bronchial
inflammation and airway narrowing.
Diagnosis may be confirmed by
24-hour monitoring of oesophageal
pH, modified barium swallow or
gastroscopy. However, a therapeutic
trial of therapy with H2 -receptor
antagonists or a proton-pump
inhibitor may obviate the need for
invasive investigations. Lifestyle
changes, including stopping smoking,
limiting food intake within 4 hours
of bed-time, reduced intake of caffeine and
alcohol, weight loss and exercise,
will also help. Elevation of the
head of the bed is also recommended.
O7.3 Alcohol and sedatives
Patients with COPD have impaired
gas exchange and an exaggerated fall
in PO2 with recumbency and sleep
onset.113,114 Excessive use
of alcohol and sedatives exacerbates
this and predisposes to
sleep-disordered breathing. Heavy
cigarette smoking is associated with
misuse of other substances in many
individuals. Nicotine, caffeine and
alcohol also predispose to gastro-oesophageal
reflux.
O7.4 Sleep related breathing disorders
COPD has adverse effects on sleep
quality, resulting in poor sleep
efficiency, delayed sleep onset,
multiple wakenings with
fragmentation of sleep architecture,
and a high arousal index. Arousals
are caused by hypoxia, hypercapnia,
nocturnal cough and the
pharmacological effects of
methylxanthines and beta-adrenergic
agents.115 Intranasal
oxygen administration has been shown
to improve sleep architecture and
efficiency, as well as oxygen
saturation during sleep.113
Indications for full diagnostic
polysomnography in patients with
COPD include persistent snoring,
witnessed apnoeas, choking episodes
and excessive daytime sleepiness. In
subjects with daytime hypercapnia,
monitoring of nocturnal
transcutaneous carbon dioxide levels
should be considered to assess
nocturnal hypoventilation. Patients
with COPD with a stable wakeful PaO2
of more than 55 mmHg (7.3 kPa) who
have pulmonary hypertension, right
heart failure or polycythaemia
should also be studied. Overnight
pulse oximetry is also useful in
patients with COPD in whom long-term
domiciliary oxygen therapy is
indicated (stable PaO2 < 55 mmHg, or
7.3 kPa) to determine an appropriate
oxygen flow rate during sleep.
The overlap syndrome:
The combination of COPD and
obstructive sleep apnoea (OSA) is
known as the "overlap syndrome". The
prevalence of COPD in unselected
patients with OSA is about 10%,
while about 20% of patients with
COPD also have OSA.114
Patients with COPD who also have OSA have a higher
prevalence of pulmonary hypertension
and right ventricular failure than
those without OSA.114
There is frequently a history of
excessive alcohol intake. While
oxygen administration may diminish
the degree of oxygen desaturation,
it may increase the frequency and
severity of hypoventilation and lead
to carbon dioxide retention.
As in other patients with OSA,
weight reduction, alcohol avoidance
and improvement of nasal patency are
useful in those with COPD. Nasal
continuous positive airway pressure
(CPAP) is the best method for
maintaining patency of the upper
airway and may obviate the need for
nocturnal oxygen. If nasal CPAP is
not effective, then nocturnal
bilevel positive airway pressure
ventilation should be considered,
although the benefits of this in
chronic stable COPD remain to be
established. The role of other OSA
treatments, such as mandibular
advancement splinting, remains to be
evaluated in the overlap syndrome.