Published online: 2020-07-28
Physical Therapy and Rehabilitation in Chronic
Obstructive Pulmonary Disease Patients
Admitted to the Intensive Care Unit
Joan Daniel Martí, PT, PhD1
David McWilliams, PT, PhD2
1 Cardiovascular Surgery Intensive Care Unit, Hospital Clínic de
Barcelona, Spain
2 Therapy Services, University Hospitals Birmingham NHS Foundation
Trust, United Kingdom
3 Respiratory Department, Hospital Clinic de Barcelona, Spain
4 August Pi i Sunyer Biomedical Research Institute (IDIBAPS),
Barcelona, Spain
Elena Gimeno-Santos, PT, PhD3,4
Address for correspondence Joan Daniel Martí, PT, PhD,
Cardiovascular Surgery Intensive Care Unit, Hospital Clínic de
Barcelona, Calle Villarroel 170, Esc 10 Planta 3, 08036
Barcelona, Spain
(e-mail: jd.martibcn@gmail.com).
Abstract
Keywords
► COPD
► intensive care unit
► mechanical
ventilation
► respiratory physical
therapy
► muscle training
► early mobilization
Chronic obstructive pulmonary disease (COPD) is a progressive lung condition that
affects a person’s ability to exercise and undertake normal physical function due to
breathlessness, poor physical fitness, and muscle fatigue. Patients with COPD often
experience exacerbations due to pulmonary infections, which result in worsening of
their symptoms, more loss of function, and often require hospital treatment or in
severe cases admission to intensive care units. Recovery from such exacerbations is
often slow, and some patients never fully return to their previous level of activity. This
can lead to permanent disability and premature death.
Physical therapists play a key role in the respiratory management and rehabilitation of
patients admitted to intensive care following acute exacerbation of COPD. This article
discusses the key considerations for respiratory management of patients requiring
invasive mechanical ventilation, providing an evidence-based summary of commonly
used interventions. It will also explore the evidence to support the introduction of early
and structured programs of rehabilitation to support recovery in both the short and the
long term, as well as active mobilization, which includes strategies to minimize or
prevent physical loss through early retraining of both peripheral and respiratory
muscles.
Patients with chronic obstructive pulmonary disease
(COPD) often present episodes of acute exacerbation
(AECOPD), leading to an accelerated disease progression
and increased mortality,1 and patients with frequent episodes have a more rapid decline in lung function,2 quality of
life,3 and decreased exercise performance.4 In particular,
during an AECOPD, patients often present with enhanced
dyspnea, respiratory muscle fatigue, and hypersecretion5
that may further deteriorate baseline gas exchange
impairment. A recent study also demonstrated a 5 to 10%
Issue Theme COPD in the Intensive Care
Unit; Guest Editors: Antoni Torres MD,
PhD, FERS, FCCP, and Miguel Ferrer, MD,
PhD, FERS
loss of quadriceps force and muscle mass between the third
and eighth day of hospitalization following AECOPD.6 Loss
of muscle function is in turn associated with poor exercise
tolerance7,8 and quadriceps muscle strength and mass in
particular appear to be significant predictors of mortality,
independent of change in lung function.9,10 Mechanisms
contributing to this acute muscle weakness include physical
inactivity,11 systemic corticosteroids,12 systemic inflammation,6 negative nutritional balance,13,14 increased resting
metabolism,15 hypoxia,13,14 and hypercapnia.15–17
Copyright © by Thieme Medical
Publishers, Inc., 333 Seventh Avenue,
New York, NY 10001, USA.
Tel: +1(212) 760-0888.
DOI https://doi.org/
10.1055/s-0040-1709139.
ISSN 1069-3424.
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Semin Respir Crit Care Med
Physical Therapy and Rehabilitation in COPD Patients in ICUs
(PR) may improve exercise capacity, quadriceps force and
quality of life, and is considered a safe intervention during
and after AECOPD.28,29 Additionally, during the last decade, a
growing body of evidence stated limb/respiratory muscular
retraining and early mobilization as a feasible and safe
strategy to improve muscular and functional capacities in
intubated and mechanically ventilated patients.30 Thus, in
this sense, it is logical to apply these recommendations to the
AECOPD patient during the ICU stay.
This evidence-based narrative review is intended to elucidate the role of several physical therapy and rehabilitation
strategies aimed at preventing and/or reversing pulmonary
and neuromuscular sequelae derived from AECOPD requiring
admission to the ICU and IMV.
Respiratory and Neuromuscular Impairment
Impact of Endotracheal Intubation and Mechanical
Ventilation
Endotracheal intubation and mechanical ventilation have
been shown to drastically impair mucus clearance, resulting
in an increased risk for mucus retention, pulmonary collapse,
and further gas exchange mismatch.31 The presence of an
endotracheal tube (ETT) within the trachea impedes the
closure of the glottis and hinders the ability to generate an
efficient cough.32 Moreover, mucociliary clearance rates may
severely decrease up to 10-folds after inflation of the ETT
cuff,33 which also obstructs outward clearance of tracheal
secretions. Additionally, the upper airways provide up to 75%
Fig. 1 Respiratory and muscular impairment in critically ill patients on IMV due to an AECOPD. AECOPD, acute exacerbation of chronic
obstructive pulmonary disease; IMV, invasive mechanical ventilation.
Seminars in Respiratory and Critical Care Medicine
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During an AECOPD, patients may eventually require
admission to the intensive care unit (ICU) and the use of
invasive mechanical ventilation (IMV), increasing the risk for
respiratory complications such mucus retention and/or
respiratory infections, and further deterioration of strength
and functional capacities.11 Bed rest in ICU is also an important risk factor for muscle weakness. ICU-acquired muscle
weakness is defined as clinically identified weakness in
critically ill patients with no possible etiology other than
critical illness.18 In mechanically ventilated patients in the
ICU setting, the cross-sectional area of the peripheral
muscles can decrease around 13% during the first week,
and it is more severe among those patients with multiorgan
failure in comparison with single-organ failure patients.19
Deconditioning and ICU-acquired muscle weakness are
associated with substantial impairments in functionality
and health-related quality of life in acute lung injury survivors that continue beyond 1220 and 24 months.21 Moreover,
peripheral muscle weakness is associated with weakness in
the respiratory muscles and consequently with prolonged
mechanical ventilation22–25 (►Fig. 1).
Respiratory physical therapy is often implemented in the
critically ill patients to prevent and/or reverse mucus retention and/or pulmonary function impairment, particularly in
patients with pathologies entailing hypersecretion.26 Physical exercise and muscular rehabilitation are also recognized
as the most prescribed interventions in patients with
AECOPD26 although published data are limited and impact
is controversial.27 Indeed, early pulmonary rehabilitation
Martí et al.
of the absolute humidity required for an optimal functioning
of the alveolar–capillary interface (i.e., 44 mg H2O/L resulting
from delivering a relative moisture of 100% at 37°C of
temperature). Hence, when the ETT or tracheostomy tube
bypasses the upper airways, suboptimal conditioning of the
respiratory gases may occur (i.e., <30 mg H2O/L), causing
damage of the airway epithelium and further promoting
impairment of airway clearance.34 Also, airway secretion
retention may facilitate overgrowth of respiratory bacteria
that ultimately results in airway inflammation and further
production of mucus.35 Finally, IMV during either spontaneous or mandatory36 modes may impair strength and function
of the diaphragm37 and overall respiratory muscles, resulting
in a prolonged need for ventilation and hospital/ICU
mortality.38
The Impact of Critical Illness and Associated ICU
Immobility
More serious exacerbations of COPD necessitating admission
to ICU can further exacerbate the impact of hospitalization
described above. Muscle wasting occurs early and rapidly
during the first week of critical illness, with losses of up to
20% seen for those in multiorgan failure.19 This muscle loss can
be of particular consequence to patients with COPD, where
pre-existing reductions in muscle strength, respiratory
reserve, and exercise capacity place them at an increased
risk for further deterioration of strength and functional capacities.14 For patients admitted to ICU and requiring IMV, there is
a strong correlation between muscular weakness and poor
outcomes, with weakness directly associated with failure to
wean from mechanical ventilation and increased in-hospital
mortality rates,22,39 as well as severe functional impairments
and reduced pace and degree of recovery in ICU survivors.40
These effects can last months to years after hospital discharge,21 with a negative impact on employment and income
in ICU survivors and their caregivers, and mortality and
utilization of primary care services are high in the immediate
postdischarge period.41
Physical Therapy Management
Airway Clearance Management
Adequate management of airway secretions and maintenance
of pulmonary function are of paramount importance in
patients with AECOPD,42 particularly when on IMV. Adequate
airway humidification is highly recommended as a routine
strategy to ensure optimal mucus properties and outward
clearance in ventilated patients.43 Chest physical therapy (CPT)
is widely implemented in the ICU to improve airway clearance
by techniques targeted to displace mucus from distal to
proximal airways and/or enhance cough efficacy,44 although
there is little research in the critically ill on IMV, and rarely
during AECOPD.45
Humidification of Respiratory Gases
Humidification of respiratory gases can be achieved passively,
through heat and moisture exchanger (HME) filters, or actively,
through heated humidifiers (HHs).43 HME filters are placed at
Martí et al.
the Y-piece of the ventilator circuit with the aim to provide a
minimum absolute humidity of 30 mg H2O/L, a relative humidity of 100%, and a temperature of 34°C. To accomplish that
aim, HME filters partially retain temperature and store moisture from patients’ expiration either by absorbing (i.e., hygroscopic filters) or repelling (i.e., hydrophobic filters) water
vapor. HHs are dedicated electromechanical devices intended
to deliver a relative moisture of 100% and up to 41°C of
temperature to ensure an absolute humidity between 34
and 44 mg H2O/L. In that case, respiratory gases are heated
and humidified during their passage within a heated water
reservoir placed along the inspiratory limb of the ventilator
circuit.
To date, no research has specifically evaluated the effects of
humidification devices in critically ill and invasively ventilated
COPD patients, and no robust conclusions can be drawn from
studies comparing HME filters and HH in unspecific ICU
population. Thus, the use of passive or active humidification
often relies on subjective criteria or per unit’s protocol. However, patients with AECOPD often meet clinical criteria in
which HME filters are deemed contraindicated by current
guidelines.43 Indeed, patients presenting thick and/or copious
secretions are at risk for complete or partial filters’ obstruction
and/or inadequate ventilation (e.g., increased resistance to
airflows) since airway secretions may enter the filter and
ultimately block its membrane. Moreover, HME filters imply
an additional dead-space along the ventilator circuit that,
when it is not compensated by dedicated software of the
mechanical ventilator, may result in retention of carbon dioxide and further enhance hypercapnia. Hence, although targeted evidence is still unavailable, it seems logical to suggest
HH as a preferable choice for critically ill and invasively
ventilated patients with AECOPD.
Chest Physical Therapy
Respiratory physical therapy is aimed to dislodge mucus toward
the central airways and enhance cough efficacy, ameliorate gas
exchange, and improve lung mechanics through different manual and mechanical techniques.44 For several years, postural
drainage through gravity-assisted positions in combination
with manual chest percussions or “clapping” to stimulate ciliary
beating has been the most implemented techniques in these
patients. Only little available evidence exists on the use of these
CPT techniques in invasively ventilated critically ill patients,
none of them with AECOPD, overall reporting contradictory
results.46 Of note, animal research suggests that chest percussions may only achieve frequencies up to 6.2 0.9 Hz, which
notably differ from ciliary beating (i.e., 10–20 Hz).47 Airway
clearance is also promoted by the two-phase gas–liquid flow
mechanism in which airflows interact with the mucus layer.48
Indeed, bench research49,50 and animal51,52 studies demonstrated that mucus is transported toward the glottis when
expiratory flows sufficiently exceed inspiratory flows, or
toward the lungs when inspiratory flows surpass expiratory
flows. Of note, a ratio 10%49 and an absolute difference of 17
L/min50 or 33 L/min52 between expiratory–inspiratory flows
have been suggested as the threshold for outward clearance of
mucus, respectively. Therefore, nowadays, physical therapists
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Physical Therapy and Rehabilitation in COPD Patients in ICUs
implement a wide range of techniques intended to modulate
airflows and create a sufficient expiratory flow bias to improve
outward clearance in the critically ill patient on IMV.
Manual or Ventilator Pulmonary Hyperinflation
Pulmonary hyperinflation is nowadays one of the most commonly utilized techniques to improve pulmonary recruitment,
gas exchange, and airway clearance in intubated and mechanically ventilated patients. The technique consists of slow delivery
(i.e., >3 seconds) of a tidal volume larger than baseline (i.e.,
50% higher than baseline or until inspiratory airway pressure
reaches 40 cmH2O), followed by 3 seconds of an inspiratory
hold, and a rapid pressure release to ensure high expiratory flow
rates.53 Manual hyperinflation (MHI) is considered a pulmonary hyperinflation delivered manually through a resuscitator
bag, whereas ventilator hyperinflation (VHI) is applied by
modifying parameters on the ventilator either during volume
or pressure modes of ventilation (e.g., tidal volume, inspiratory
pressure, inspiratory time, and inspiratory pause). Although
none of the available research investigated MHI and/or VHI on
patients with AECOPD, these may potentially benefit from the
technique since current research in a mixed population of
patients suggests MHI/VHI to result in positive outcomes. The
latest systematic review on MHI during IMV,54 including six
randomized controlled trials and six observational studies,
concluded that the technique may significantly improve compliance in cardiac patients undergoing surgery, patients with
pneumonia or atelectasis, but not in those with acute lung
injury. However, the efficacy of MHI to enhance oxygenation is
still uncertain. Similarly, MHI showed no superiority on mucus
clearance when compared independently to standard care,
whereas positive results have been reported when the technique is combined with positioning of the patient. For instance,
a randomized crossover trial55 in mechanically ventilated
patients presenting radiological signs of lung collapse obtained
significantly greater wet weight of sputum when comparing a
side-lying position with or without MHI (mean (95% confidence
interval [CI]) of 5.5 g (2.6–8.5) vs. 3.5 g (2.4–4.6); p ¼ 0.039).
Furthermore, another randomized crossover trial56 on intubated patients with pulmonary consolidation or collapse also
reported a mean (95% CI) weight of sputum difference of 1.97 g
(0.84–3.10) when adding head-down tilt to a side-lying position
and MHI. A notable variability on the procedures to implement
MHI has been described within the studies, which may have
influenced current available results.54 For instance, the adequate implementation of the technique is of paramount importance to attain an optimal expiratory bias and enhance mucus
clearance, thus specific training targeted to correctly achieve
each of the MHI phases is necessary to ensure the efficacy of the
technique.57
Comparisons between MHI and VHI have been little studied
and, overall, nonrelevant differences in terms of efficacy and
safety have been found.54 However, a recent study in animals
with severe pneumonia demonstrated VHI to be significantly
more consistent when compared with MHI.58 Indeed, VHI
permits a regular implementation of the technique, avoiding
dangerous variability in the pressure transmitted to the lungs
that ultimately depends on practitioners’ experience. MoreSeminars in Respiratory and Critical Care Medicine
Martí et al.
over, VHI does not require disconnection of the patient from
the ventilator as during MHI, allowing continuous monitoring
of the procedure and preventing lung derecruitment and/or
oxygen desaturation. Thus, VHI is suggested to be a suitable
alternative to MHI in intubated and mechanically ventilated
patients. However, it is important to emphasize that not all
modes of ventilation are appropriate to clear airway secretions
through pulmonary hyperinflation.59 Unpredictable variability
in inspiratory flow rates during pressure-controlled modes of
ventilation makes it difficult to ensure a sufficient expiratory
flow bias that enhances mucus clearance,60 whereas during
volume-controlled modalities, an expectable in-expiratory
flow bias is possible.
Finally, although no significant adverse events have been
reported in the literature, the elevated inspiratory pressures
transmitted to the respiratory system during MHI/VHI may
lead to detrimental hemodynamic effects (e.g., decreased
venous return) and/or increased risk for volutrauma. Hence,
pulmonary hyperinflation should be used carefully in the
critically ill on IMV, particularly in patients with hemodynamic compromise and/or affected lung parenchyma.
Manual Chest Expiratory Compressions
Manual compressions over the ribcage during expiration are
often implemented to optimize expiratory flow rates and
displace mucus toward the central airways.61 Commonly,
physical therapists apply either gentle and gradual compressions along the expiratory phase or brief and strong compressions at the very beginning of expiration. Gentle compressions
during the mid–late expiration are intended to displace peripheral secretions by slowly deflating the lungs and optimize
the mucus–airway ratio to prolong the flow–mucus interaction. Whereas, hard manual ribcage compressions are aimed to
enhance outward clearance of proximal secretions through
specifically increasing peak expiratory flows and the consequent expiratory flow bias. Although these have never been
specifically investigated in critically ill patients with AECOPD,
both variants of manual chest compressions may share similarities with other techniques implemented in chronic hypersecretory diseases such as COPD. Soft compressions in a sidelying position are commonly employed with positive results
similar to the ELTGOL technique (i.e., slow expiration with the
glottis opened in the lateral posture)62–64 to clear mucus from
the dependent lung. However, hard manual ribcage compressions are often used independently or in combination with
other strategies (e.g., positioning) as the forced expiratory
technique in chronic patients with copious secretions.65
Unoki T et al66 first compared gradual chest compressions
to standard care (i.e., tracheal suctioning) in 31 intubated and
mechanically ventilated patients positioned side-lying and
also in adult rabbits with induced atelectasis.67 Of note, in
these studies the affected lung was positioned uppermost. The
authors found no significant improvements in the weight of
aspirated natural and artificial mucus, respectively, when the
technique was implemented. The manoeuver did not improve
gas exchange or pulmonary mechanics in humans, whereas
animals that received chest compressions experienced a worsening in oxygenation and compliance of the respiratory
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Physical Therapy and Rehabilitation in COPD Patients in ICUs
system. Lately, hard manual ribcage compressions were associated with positive outcomes in a randomized crossover trial
of 20 mechanically ventilated patients comparing chest compressions with additional pulmonary hyperinflation (i.e., a
pressure support ventilation of 35 cmH2O) or hyperinflation
alone.68 Chest compressions significantly improved the
volume of suctioned sputum (1 [0.5–1.95] vs. 2 [1–3.25] mL;
p < 0.01) and static compliance of the respiratory system after
hyperinflation (40.2 12.2 to 42.2 12 vs. 38.8 9.2 to
38.7 10.3 mL/cmH2O; p ¼ 0 0.03). However, the results
were reported as not clinically relevant since the effect size
of the technique was considered small for mucus volume and
the overall pulmonary mechanics. Importantly, six patients
presented expiratory flow limitation during chest compressions, although it is uncertain whether this was due to the
technique or slight sedation of the patients (i.e., Ramsay
sedation scale 2–4). The aforementioned results were corroborated in a more recent laboratory study on a swine model of
prolonged IMV including objective radiopaque tracking of
natural secretions.69 Indeed, soft compressions promoted no
significant effects on mucus clearance, and the technique was
associated with a significant increase in lung elastance and a
decrease in cardiac output (23.6 6.9 to 24.6 7.2 cmH2O/L
and 3.2 1.1 to 2.4 0.7 L/min; p ¼ 0.0391). Conversely, hard
manual ribcage compressions significantly enhanced peak
expiratory flow rates and expiratory bias, thus the technique
improved mucus transport velocity toward the glottis when
compared with soft compressions and conventional IMV
(1.01 2.37 vs. –0.15 0.95 and –0.28 0.61 mm/min;
p ¼ 0.0283). Moreover, no adverse effects occurred during
the manoeuver.
The positive effects of abrupt manual chest compressions
may be enhanced when combined with vibrations and/or
positioning of the patient. A bench study70 reported peak
expiratory flow rates to significantly increase by up to a
mean (95% CI) of 8.8 (6.0–11.6) L/min when vibrations were
applied at the early expiration and 7.0 (4.3–9.9) L/min when
applied during the late inspiration, although this latest
variant may worryingly increase the inspiratory airway
pressure above safety levels. Finally, when combined with
a side-lying position or a head-down tilt, manual chest
compressions/vibrations have been associated with a lower
incidence of ventilator-associated pneumonia.71
Mechanical In-Exsufflation
Mechanical in-exsufflation (MI-E) is aimed to mimic cough
by using a dedicated electromechanical device that gradually
applies a positive inspiratory airway pressure, and then
rapidly shifts to a negative pressure to create high expiratory
flow rates.72 Therefore, MI-E is often employed to improve
clearance of proximal airway secretions in patients with
respiratory-pump failure (e.g., neuromuscular patients)
unable to produce adequate peak cough flows. In recent
years, MI-E has gained interest as a potential technique to
improve cough efficacy in critically ill patients on IMV
although research on the field is still scant. Gonçalves
et al73 first compared the intensive use of the technique
(i.e., three times per day before extubation, and each day
Martí et al.
within 48 hours following extubation) with standard care in
a randomized control trial on 75 intubated and mechanically
ventilated patients (including 10 subjects with AECOPD) that
successfully achieved a spontaneous breathing trial. Patients
undergoing MI-E presented significant lower reintubation
rates (17 vs. 48%; p < 0.05), and decreased time on mechanical ventilation (17.8 6.4 vs. 11.7 3.5 days; p < 0.05) and
ICU length of stay after extubation (3.1 2.5 vs. 9.8 6.7
days; p < 0.05). A randomized parallel group trial74 in 180
adult patients on IMV >24 hours compared the weight of
aspirated secretions during MI-E to a combination of respiratory physical therapy techniques. In comparison with the
control group, MI-E significantly increased the weight of
aspirated secretions (1.35 1.56 vs. 2.42 2.32 g, p < 0.001)
and the static lung compliance immediately after the intervention (0.57 4.85 mL/cmH2O vs. 1.76 4.90 mL/cmH2O,
p < 0.001), with no associated adverse events. Interestingly,
although the study was underpowered for detection of
subgroup effects, patients with COPD as comorbidity (i.e.,
14 patients in each group) resulted in significantly less
aspirated secretions. Finally, Coutinho et al75 performed a
randomized crossover trial in 43 adult patients invasively
ventilated for >48 hours to compare the volume of sputum
retrieved during MI-E or conventional tracheal suctioning.
No significant differences either in the primary outcome
or secondary outcomes such as pulmonary mechanics were
found between groups.
MI-E pressures of þ40/ 40 cm H2O are commonly set to
achieve comfortable and effective treatments in patients with
unaffected lung mechanics. However, higher inspiratory–expiratory pressures may be necessary in patients with pathologies
entailing an increase in respiratory resistances and/or decreased compliance (e.g., COPD).76 Moreover, elegant in vitro
research77 found artificial airways to markedly increase resistance to airflow due to the smaller internal diameter of the
tubes. Hence, in the critically ill patients on IMV, and particularly in patients with resistive/restrictive pulmonary mechanics, in-expiratory pressures up to 70 cm H2O should be
considered to achieve optimal peak cough expiratory flows.76
However, although no major adverse events have been
reported, the delivery of elevated pressures (i.e., beyond
30 cm H2O) to the lungs is not exempt of risk (e.g., barotrauma),
thus the use of MI-E in these patients must be carefully
considered, particularly when structural damage of the lung
parenchyma is present or suspected.
High-Frequency Oscillations
Intrapulmonary percussive ventilation (IPV) is an instrumental
technique aimed to reopen collapsed alveoli and enhance
mucus clearance within the peripheral airways. IPV is implemented through a dedicated device superimposed on spontaneous breathing or mechanical ventilation that delivers bursts
of small tidal volumes at high frequencies (i.e., up to 6 Hz).78
Thus, the resulting pressure-limited pulmonary beatings have
been suggested to safely recruit collapsed units and the asymmetric airflow pattern, which favors an expiratory flow bias,
may improve outward clearance of mucus. IPV has been little
investigated in hospitalized and noninvasively ventilated
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Physical Therapy and Rehabilitation in COPD Patients in ICUs
Physical Therapy and Rehabilitation in COPD Patients in ICUs
Muscle Reconditioning
Muscle retraining is an important strategy to maintain or
restore muscle strength and functionality of AECOPD
patients in the ICU. It can improve mass and cross-sectional
areas of the muscle, and the function of the oxidative
enzymes producing an increase in the oxygen extraction
and efficiency of the muscle. Evidence shows that early
physical activity is safe and is a feasible intervention after
the cardiopulmonary and neurological stabilization.81,82
Mobilization strategies may include passive and active
movements and turning in bed, active-assisted and active
exercises, cycloergometer (or cycling pedals) in bed, neuromuscular electrical stimulation (NMES), sitting on the edge
of the bed, standing, transferring to chair, chair exercises,
stepping and walking, and also inspiratory muscle training
(IMT).30,83–85
Peripheral Muscle
Bedside Cycle Ergometer
A bedside cycle ergometer is a stationary bicycle that allows
patients to receive passive (without work from the patient),
active and assisted, and active and resistive exercises by an
automatic mechanism during the bed-rest period. This
training modality has been shown to be safe and feasible
in a small sample size of patients with severe COPD confined
to bed, increasing the oxygen uptake, breathing frequency,
and minute ventilation both during active and passive
exercises.86
In a randomized controlled trial, 90 critically ill mechanical ventilated patients with an expected prolonged ICU stay
(>7 days) received a 20-minute session per day using a
bedside cycle ergometer for 5 days per week in addition to
standard care.87 No differences in mortality rate during the
hospital stay were observed. However, there were positive
results in short-term outcomes, such as increased isometric
quadriceps force and functional exercise capacity (measured by the 6-minute walk test) and higher self-perceived
functional status at hospital discharge in ICU survivors. The
bedside cycle ergometer was described as a safe and feasible method with no major adverse events (only 4% of
training sessions were stopped due to changes in oxygen
saturation).
Seminars in Respiratory and Critical Care Medicine
In the same way, a case series of 19 sedated and hemodynamically stable patients within the first 72 hours of mechanical ventilation were enrolled in a passive leg cycling exercise
(frequency of 30 rpm) during 20 minutes using an electric cycle
ergometer.88 The results showed no alterations in hemodynamic, respiratory, or metabolic variables, or safety concerns,
even while patients received a low dose of vasoactive drugs.
Recently, a protocol for a pilot randomized study of early
cycle ergometry versus standard physical therapy intervention in patients under IMV has been published.89 Bedside
cycle ergometry is a promising early ICU exercise intervention for mechanically ventilated patients because it targets
the legs, is easily provided both in sedated or awake patients,
and is human-resource-efficient. Further specific research in
AECOPD is required to establish the use of bedside cycle
ergometry as a part of the rehabilitation during the ICU stay.
Neuromuscular Electrical Stimulation
NMES is commonly used as a method to reduce ICU-acquired
muscle weakness. NMES uses conductive pads placed on the
skin to apply an electrical stimulation over the targeted
muscles of the patient and induce skeletal muscle contractions
by activation of the intramuscular nerve branches. In the
specific ICU setting, the objective of the intervention is focused
on gain in strength (rather than gain in endurance) because it is
more appropriate for patients with an evident peripheral
muscle weakness that limits even transfer movements.90
Although the quality of evidence is low to very low due to
the risk of bias within the studies and the small number of
studies, a Cochrane systematic review of NMES in patients
with COPD90 established that the application of the intervention on the most debilitated patients may increase the
functional recovery, especially in those patients with long
bed rest. Zanotti et al91 performed a randomized controlled
trial for studying the effects of NMES in bed-bound COPD
patients who were on mechanical ventilation and with
peripheral muscle hypotonia and atrophy in comparison to
standard care (active limb mobilization). The stimulator
generated bipolar, biphasic, and asymmetric rectangular
pulses, and the session consisted of 5 minutes at 8-Hz pulse
width 250 microseconds and then 25 minutes at 35-Hz pulse
width 350 microseconds. The treatment was performed
5 days per week for 4 weeks. Results showed that muscle
strength (quadriceps femoris and vastus glutei) was significantly improved and days to move from bed to chair decreased in the group treated with NMES, with no safety
concerns. More recently, Akar et al92 showed similar results
on muscle strength and, in addition, they demonstrated a
reduction of the levels of inflammatory cytokines [C-reactive
protein, interleukin (IL)-6, and IL-8) in patients treated with
NMES. In this case, the stimulator generated symmetrical
biphasic square 50-Hz waves and the amplitude was
switched between 20 and 25 mA with 6 seconds of contraction, 1.5 seconds of increase, and 0.75 second of decrease.
The intervention was 5 days per week for 20 sessions in total.
Out of the ICU setting, similar results have been shown in a
randomized controlled trial performed in severely dyspneic
COPD patients with muscle weakness that received high
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patients with AECOPD,79 overall reporting encouraging
results in outcomes such as need for ventilator assistance
or length of stay and, to the best of our knowledge, no
research specifically assessed the technique when these
patients required IMV due to critical illness. Nevertheless,
a randomized controlled trial80 on 40 tracheotomized
patients (including 11 COPD patients) from two different
weaning centers (i.e., patients were not sedated and/or
critically ill) compared CPT with or without additional
IPV during 10 minutes twice per day. The IPV group resulted
in improved oxygenation and maximal expiratory pressure
after 5 and 10 days of treatment, respectively, and presented a lower incidence of pneumonia 1 month after
discharge from the centers (two patients vs. none; p < 0.05).
Martí et al.
Physical Therapy and Rehabilitation in COPD Patients in ICUs
Respiratory Muscle
Diaphragmatic weakness during critical illness is commonly
present in patients with IMV since inspiratory activity is
supported by the ventilator.24 This is defined as ventilatorinduced diaphragmatic dysfunction (VIDD) and is one of the
most common complications associated with IMV.94 The term
refers to diaphragm dysfunction that may occur after initiating
the IMV. Up to 18 hours of IMV is associated with atrophy of
both slow- and fast-twitch fibers in the human diaphragm.95
Respiratory muscle weakness is twice as frequent as peripheral
muscle weakness, increases the duration of IMV, and prolongs
the period of weaning.24,96 Diaphragmatic weakness and
dysfunction are independently related to the time under IMV
and the ventilatory mode (being more frequent in controlled
modes than assisted-controlled modes).36
IMT is used to improve muscle strength and endurance of
inspiratory muscles in patients with ICU-acquired weakness
and VIDD,30 and it may benefit patients with weaning
failure.97 A recent systematic review98 showed that the
most common method used for IMT was inspiratory threshold loading (21 out of 28 studies). Usually, the threshold
loading is performed using a threshold valve in which, to
permit an inspiratory flow, the patient has to generate a
certain respiratory muscle pressure (training pressure). A
threshold load may also be applied directly through the
ventilator by setting a trigger pressure at a desired threshold
pressure level. Threshold loading training is performed by
applying a pressure >30% of the maximal inspiratory pressure (MIP) for a few repetitions (e.g., 5 sets of 6 breaths) or a
few minutes (e.g., 5 minutes twice per day). The load should
be increased progressively by 10% taking into account the
tolerance of the patient, or 1 to 2 cmH2O if the MIP is
reassessed. Finally, if baseline MIP is not measurable, IMT
load can be titrated manually via a “trial-and-error” method,
where the device is regulated at the lowest intensity to then
progressively increase resistance until the patient can only
complete up to six breaths during a set of repetitions.
Although previous literature reports that IMT is safe, well
tolerated and with no related adverse respiratory events
and/or hemodynamic instability,98 it is important to remark
that the patient–ventilator disconnection may be required to
provide the intervention. Importantly, a 1-minute pause
between sets is allowed to reconnect the patient to IMV
and avoid the risk of oxygen desaturation.
The muscle fibers of the diaphragm in patients with COPD
suffer cellular adaptations that increase resistance to fatigue,99 thus the effectiveness of IMT in stable COPD is still
controversial.100 However, since patients with AECOPD may
present weaning difficulties in the ICU setting, these could
obtain a benefit from the IMT intervention. In conclusion, the
role of IMT in ICU rehabilitation in AECOPD remains poorly
defined and studied.
Early Rehabilitation/Mobilization
To ameliorate the negative consequences of critical illness,
early rehabilitation and mobilization is recommended for
patients admitted to critical care. The term “early rehabilitation” within the ICU refers to interventions that commence
immediately after stabilization of physiologic derangements,101 with interventions aiming to start within 1 or
2 days of initiation of mechanical ventilation. This concept
becomes particularly important for those patients with
COPD, where pre-existing deconditioning and physical limitations may further exacerbate the impact of critical illness
related immobility and deconditioning. Certainly previous
research assessing frailty on admission to critical care has
found poor premorbid status to be associated with poor
outcomes and higher mortality in the first year following
critical care discharge.102 The theoretical concept therefore
for starting rehabilitation earlier would seem a simple one,
with the hypothesis being that starting early would reduce
impact of immobilization and corresponding muscle loss. To
support this, a recent meta-analysis of patient mobilization
concluded that early and progressive mobilization was both
safe and feasible for patients admitted to critical care.103
The time taken to first mobilize for patients admitted to
ICUs appears to have a significant impact on outcomes. A
study by Morris et al104 of 330 patients (including 32 with
COPD) evaluated the impact of introducing a mobility protocol delivered by a specialist mobility team within a medical
ICU. Patients receiving the early rehabilitation intervention
sat out of bed 6 days earlier (5 vs. 11 days, p < 0.001) in
comparison to control subjects. This earlier mobilization was
associated with a reduced length of stay in both the ICU (5.5
vs. 6.9 days, p ¼ 0.25) and hospital (11.2 vs. 14.5 days,
p ¼ 0.006). This was a similar finding to a randomized
controlled trial including 104 patients (10 of which had an
AECOPD) which evaluated the impact of introducing early
physical therapy and occupational therapy at two medical
ICUs.105 Patients in the early intervention arm mobilized out
of bed earlier in the ICU stay (1.7 vs. 6.6 days, p < 0.0001) and
while they were still invasively ventilated. This was associated with a reduced duration of mechanical ventilation (3.4
vs. 6.1 days, p ¼ 0.02), alongside an increased proportion of
patients returning to independent function at the point of
hospital discharge (59 vs. 35%, p ¼ 0.02).
At present to our knowledge no studies have been completed specifically evaluating the impact of early
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frequency (HF-NMES, at 75 Hz), low frequency (LF-NMES, at
15 Hz) or progressive strength training during an 8-week PR
program (twice a day, 5 days per week).93 Patients treated
with HF-NMES or strength training presented greater increase in muscle strength and exercise performance in
comparison to the LF-NMES group.
All these results may suggest that NMES intervention is
safe and effective to ameliorate muscle weakness and
improve muscle strength in patients with COPD. However,
further research is needed to establish the underlying mechanism by which NMES could prevent ICU-acquired muscle
weakness in AECOPD patients. Moreover, it would be important to define protocols (i.e., type of stimulation, frequency,
time), the response in specific groups of patients, and the
duration of the effects because as with any other exercise
training intervention, the benefits will disappear if there is
not a maintenance program.
Martí et al.
Martí et al.
rehabilitation for patients invasively ventilated following
AECOPD. A quality-improvement project of early rehabilitation completed by Needham et al106 did however include 57
patients of which 27 (47%) had a diagnosis of COPD. The
intervention included the introduction of a multidisciplinary
team (MDT) focused on reducing heavy sedation and
increasing physical therapy and occupational therapy contacts. The intervention group received significantly more
functional rehabilitation sessions (7 vs. 1, p < 0.001) with a
higher level of functional mobility (treatments involving
sitting or greater mobility, 56 vs. 78%, p ¼ 0.03). This
increased activity again was associated with reduced lengths
of stay in both the ICU and hospital.
To summarize, when implemented, programs of early
mobility have demonstrated numerous benefits to both the
patient and the organization. As a result, early mobilization is
now included as a key component in several national and
international guidelines.107,108 At a patient level, early mobilization helps to prevent the loss of muscle mass and minimize
the poor physical condition associated with prolonged bed
rest.81 This is particularly important for those patients admitted following an AECOPD, with programs of early mobilization
in general ICU populations associated with significant
improvements in the functional status, muscle strength, walking ability at discharge, and health-related quality of life.109 At
an organizational level, the introduction of early mobility
programs is associated with reduced health care costs resulting from a reduction in ICU and hospital length of stay and
subsequent improved patient flow, as well as a reduction in
both ICU and hospital readmissions.
present with higher baseline respiratory rates or the acceptance of lower oxygen saturation levels both at rest and on
activity. While patients are invasively ventilated, the process
of sitting a patient on the edge of the bed forms an important
part of the early patient assessment and subsequent provision of a structured rehabilitation program and seating plan.
This process provides vital information with regard to
patients’ sitting balance and readiness for sitting out of
bed, their physiological stability in response to activity and
positional change, as well as many other specific physical and
psychological benefits.
The process of sitting on the edge of the bed can at times
be labor intensive, particularly for patients who are obese, of
low arousal, or with profound ICU-acquired weakness, where
it may take four or even five members of staff to transfer
the patient to the edge of the bed. Alternatively, factors such
as a poorly tolerated airway, poor respiratory reserve, lowdose inotropic support, or postural hypotension may raise
safety concerns around the process of moving a patient onto
the edge of the bed. In these instances stretcher chairs can
be used, providing a safe and controlled method of assessing
or mobilizing these patients. Devices such as these can allow
earlier transfer out of bed for patients deemed to be high
risk,117 allowing safe and supportive seating positions to be
achieved gradually. Passive chair transfer is particularly
useful for those patients with low physiological reserve,
being significantly less demanding than sitting on the edge
of the bed.118 In these early stages, sitting should be limited
to a maximum of 1 hour to prevent the risk of developing
pressure ulcers or becoming overly fatigued.
Commencing Mobilization
Progressing Rehabilitation and Mobilization
Starting mobilization as early as clinically possible is an
important method of reducing the significant impact of critical
illness immobility. To aid this decision making, expert consensus guidelines have been produced which help guide the safety
of early mobilization, providing a stepwise approach to assessment and initiation of both in- and out-of-bed activities.110
Another potential solution, which may be suitable to help
decision making and guide practice, is through the use of early
mobility protocols. There is strong evidence to support the use
of protocols for other areas of care such as sedation minimization and ventilator weaning.111–113 Expanding protocol use to
include mobilization seems possible, and excellent examples
exist to help guide development.114–116 The combined use of
protocols and predefined safety criteria for mobilization has
several beneficial effects, helping to guide initiation and
identify patients who are deemed sufficiently hemodynamically stable and ready to start more active mobilization.
Numerous studies have explored the safety of progressive
mobility within ICU populations with a recent meta-analysis
demonstrating adverse events in only 0.6% of over 14,000
mobilization/rehabilitation sessions.109
For patients admitted to ICUs following AECOPD, ultimately the decision to commence mobilization should be
based on an assessment of cardiovascular stability and
respiratory reserve. This may require modifications to be
made from standard mobility practice, with patients likely to
Once early rehabilitation has been commenced, any protocol
should also provide a framework to progress activity and
ensure ongoing collaboration between team members. A
recent survey of current practice, including 951 ICUs from
four countries, provided useful insights into the key components required to support early mobility programs.119 The
presence of a dedicated physical therapist, written sedation
protocols, MDT ward rounds, and daily goal setting for rehabilitation were significantly associated with the presence of
established early mobility practice within the ICUs surveyed.
Establishing an open forum for MDT communication is vital to
support these processes. Previous findings have shown that in
the absence of specific MDT ward rounds health care professionals often prioritize information to reflect their own clinical
roles, which may in turn lead to errors in communication or
missed information.120
Patient-care rounds should be an important team activity
where the patient’s plan of care is discussed formally and tasks
prioritized. Given the complex nature of early rehabilitation in
patients with AECOPD, these rounds provide team members
with the opportunity to discuss the patients’ rehabilitation in
the context of medical stability, any current plan for weaning
of sedation and respiratory support, management of delirium,
and to highlight other team member tasks which may require
completion.119 This process allows the generation of individualized rehabilitation plans and the setting of goals to support
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Physical Therapy and Rehabilitation in COPD Patients in ICUs
Physical Therapy and Rehabilitation in COPD Patients in ICUs
3 Seemungal TAR, Donaldson GC, Paul EA, Bestall JC, Jeffries DJ,
4
5
6
7
8
9
10
11
Conclusion
12
COPD patients may require admission to the ICU and invasive
ventilatory support due to an acute exacerbation of the
pathology, increasing the risk for respiratory and/or neuromuscular complications that further deteriorate baseline
pulmonary and functional impairment. However, an adequate management of airway clearance and early muscular
retraining and rehabilitation may substantially attenuate the
impact of exacerbations, and improve clinical evolution in
this population of patients. Active humidification (i.e., HHs)
is preferred when hypersecretion and/or hypercapnia is
present, and respiratory physical therapy is considered a
potential strategy to enhance mucus clearance in patients
with mucus retention due to IMV, particularly when pulmonary hyperinflation and positioning are combined. Hence,
although specific evidence on patients with AECOPD requiring IMV is rare and inconclusive, they might benefit from
these interventions. Similarly, limb and respiratory muscle
reconditioning and early mobilization have been little investigated in the critically ill due to an AECOPD. However,
positive results from a mixed population of patients invasively ventilated in the ICU suggest that early rehabilitation
might also improve strength and functional capacities in
critically ill COPD patients.
Conflict of Interest
None declared.
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Physical Therapy and Rehabilitation in COPD Patients in ICUs