Chest physiotherapy in mechanically ventilated children: A review
Crit Care Med. 2000 May;28(5):1648-51.
Krause, Martin F. MD; Hoehn, Thomas MD
Author Information
From the Children's Hospital, Albert-Ludwigs-University, Freiburg, Germany.
Address requests for reprints to: Martin F. Krause, MD, University Children's Hospital, Mathildenstr. 1, D79106 Freiburg, Germany. E-mail: Krause@kkl200.ukl.uni-freiburg.de
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Abstract
Objective: Many physicians, nurses, and respiratory care practitioners consider chest physiotherapy
(CP) a standard therapy in mechanically ventilated children beyond the newborn period. CP includes
percussion, vibration, postural drainage, assisted coughing, and suctioning via the endotracheal tube.
Data Sources: We searched the medical literature by using the key words "chest physiotherapy" and
"chest physical therapy" (among others) by means of the MEDLINE and Current Contents databases.
Study Selection: Because of the paucity of objective data, we examined all reports dealing with this
topic, including studies on adult patients. For data extraction, not enough material existed to perform
a meta-analysis.
Data Synthesis: Despite its widespread use, almost no literature dealing with this treatment modality
in pediatric patients exists. Studies with mechanically ventilated pediatric and adult patients have
shown that CP is the most irritating routine intensive care procedure to patients. An increase in oxygen
consumption often occurs when a patient receives CP accompanied by an elevation in heart rate, blood
pressure, and intracranial pressure. CP leads to short-term decreases in oxygen, partial pressure in the
blood, and major fluctuations in cardiac output. Changes in these vital signs and other variables may
be even more pronounced in pediatric patients because the lung of a child is characterized by a higher
closing capacity and the chest walls are characterized by a much higher compliance, thus predisposing
the child to the development of atelectasis secondary to percussion and vibration.
Conclusion: CP in mechanically ventilated children may not be considered a standard therapy.
Controlled studies examining the impact of CP on the duration of mechanical ventilatory support,
critical illness, and hospital stay are needed.
Chest physiotherapy (CP) has been advocated in the field of pediatrics for >20 yrs and has emerged as
a standard treatment modality in young patients with pulmonary diseases (1). Different techniques of
CP have been studied in a variety of different lung diseases in children with an almost unpredictable
effect.
A "positive effect" of CP has, in general, been defined as an acute improvement in the patient's overall
appearance, lung auscultation, blood gas tensions, and chest radiographs (2). The volume of
expectorated lung secretions after CP will be underestimated because parts of the secretions will be
swallowed by the pediatric patient (3).
CP has produced different effects on spontaneously breathing patients with a variety of acute
pulmonary diseases. No improvement in lung function occurred in children with exacerbated bronchial
asthma who received CP (4). CP seems to be of little value in the treatment of bronchiolitis. No
favorable influence on lung mechanics (5), a rapid recovery, or earlier discharge from the hospital (6)
was detected. Studies in adult patients with pneumonia (7) failed to detect any influence on the
duration of fever, clearing of radiodensities on chest radiographs, duration of hospitalization, or
mortality rate. In a controlled study with young adults (8), CP led to prolonged fever and hospital stay
in the treated group.
In contrast, CP has emerged as a standard treatment modality for young patients with cystic fibrosis.
Its effectiveness has been proven by numerous studies (9, 10). However, CP does not improve
pulmonary status in all chronic lung diseases. Wollmer et al. (11) studied adult patients with acutely
exacerbated chronic bronchitis. Percussion, assisted coughing, and postural changes did not lead to
improvements in this condition.
A beneficence has been reported in pediatric lung abscess in children aged >7 yrs (12), acute lobar
atelectasis (13), and lung complications after traumatic quadriplegia (14). The latter two studies
included only adult patients. Therefore, we searched the literature for reports of the effectiveness of
CP in mechanically ventilated pediatric patients. Children usually develop respiratory failure because
of acute pulmonary diseases for which they receive mechanical ventilatory support. We limited our
search to studies involving patients treated with mechanical ventilatory support to overcome
respiratory failure caused by acute pulmonary diseases.
Literature Search. We searched the literature by using the key words "chest physiotherapy" or "chest
physical therapy," "mechanical ventilatory support," "children," and "vital signs" with the help of the
MEDLINE and Current Contents databases. Reference lists of all related articles were checked for
further articles of interest.
Chest Physiotherapy Techniques. The following CP techniques are thoroughly described in the
international literature for use in mechanically ventilated patients (1, 15): a) manual percussion with
proper cupping of hand or with a face mask; b) vibration of the chest wall transmitting energy through
the chest wall to loosen or move bronchial secretions; c) postural drainage using gravity to move
secretions from peripheral airways to the larger bronchi; d) assisted coughing to transport loosened
secretions from the bronchial tree to the trachea; and e) suctioning of secretions via the endotracheal
tube. Other CP techniques, such as with contact breathing or guided breathing, have been advocated.
No studies are available evaluating their effectiveness.
Studies in Mechanically Ventilated Children. Despite our extensive literature search, we found only the
following two studies that involve mechanically ventilated children beyond the neonatal age. Reines et
al. (16) describe the effects of CP in 44 cardiac patients aged 3 months through 9 yrs. Vibration and
percussion, postural drainage (including the head-down position), and endotracheal suctioning were all
used. In the CP group, 13/19 (68%) vs. 8/25 (32%) patients of the control group developed atelectasis
after cardiac surgery, with the consequence of a longer hospital stay for those patients in the CP
group. The two groups of patients showed no differences in age, incision site (sternotomy vs. lateral
thoracotomy), and percentage of cardiac lesions with left-to-right shunt. Reines et al. speculated that
this apparent reversal of expected results could be caused by a number of factors, such as an increase
in ventilation-perfusion mismatch resulting from mucus moving from peripheral to central airways,
lung compression from percussion, decrease in functional residual capacity because of pain induced by
CP and hypoventilation in the head-down position. This study did not provide data on the length of
mechanical ventilatory support postoperatively or the number of CP treatments during or after
mechanical ventilatory support. Zach et al. (17) observed a high solution quota (>95%) of atelectases in
children treated with CP. A minority of patients received mechanical ventilatory support. This study
used a historical control group for comparison of results, omitted distinguishing children receiving
mechanical ventilatory support from those breathing naturally, and did not describe the CP techniques
used.
Studies in Mechanically Ventilated Adult Patients. Applying the data from studies evaluating the
effectiveness of CP in mechanically ventilated adult patients when considering benefits and burdens of
CP in pediatric patients under these clinical conditions may be inappropriate because the specific
physiologic properties of lung and chest wall of children differ from adults. All of the following studies
used a variety of CP techniques mentioned above.
Laws and McIntyre (18) were first to investigate the influence of CP on oxygenation and cardiac output
in six mechanically ventilated patients in 1969. Their introduction states: "Chest physiotherapy has
become accepted as an essential and valuable adjunct to the care of patients undergoing artificial
ventilation for respiratory failure." No significant differences in oxygenation during and immediately
after CP could be detected when comparing the results to the situation before initiating CP. However,
a rise or fall by as much as 50% of the initial cardiac output was observed.
Gormezano and Branthwaite (19) looked for changes in gas exchange 5 to 30 mins after CP in 42
patients on ventilatory support for reasons of major general surgery, respiratory failure, and cardiac
diseases. Significant decreases in PaO2 and increases in PaCO2 could be detected, especially in those
patients with low cardiac output or respiratory failure. Gormezano and Branthwaite postulated that
the increase in intrathoracic pressure exerted by CP could lower the cardiac output so that for a given
shunt effect, mixed-venous PO2 and, hence, PaO2 would fall.
Similar results were obtained by Connors et al. (20) in 22 mechanically ventilated patients. Connors et
al. claimed that an increase in ventilation-perfusion mismatch as responsible for the deterioration in
oxygenation. Decrease in PaO2 was more pronounced in a subgroup of patients with less production of
lung secretions. These findings were backed up by the results of Tyler et al. (21) describing a decrease
of PaO2 by 18 mm Hg (75-57 mm Hg; 2.4, 9.9 to 7.6 kPa) during the sequence of CP. Tyler et al.
emphasized the necessity of a thorough monitoring of the patient's vital signs during CP, especially for
those patients with a low baseline PaO2.
Results vary in studies involving the influence of CP on gas exchange in mechanically ventilated
patients. Mackenzie et al. (22) could not detect any negative effect of CP on oxygenation during or
after intervention in 47 patients. They were convinced that the use of an end-expiratory pressure of 510 cm H2O (0.5-1.0 kPa) prevented the fall in PaO2 observed by other authors. Mackenzie and Shin (23)
found an improvement in oxygenation immediately and 2 hrs after CP, accompanied by small
improvements in lung compliance and intrapulmonary shunt. They reported marked individual changes
for cardiac index and intrapulmonary shunt among the patients.
Weissman and Kemper (24) calculated a mean increase in oxygen consumption during CP of +62% ± 29%
above the baseline level in 16 critically ill surgical patients. Weissman et al. (25) were able to identify
two different groups of patients regarding their hemodynamic response during CP. The intervention
resulted in an increase in oxygen consumption in all patients as verified by a significantly higher
oxygen extraction (35% to 50%) in the vascular periphery or by a higher oxygen supply through the
cardiorespiratory response that was reflected by an overall increase in heart rate, systemic blood
pressure, and minute ventilation. Those patients reacting with an increase in oxygen extraction in the
vascular periphery were those with an almost unchanged cardiac output reflecting absent cardiac
reserve.
The increased oxygen demand during CP is mainly because of increased muscle activity because
administration of a muscle relaxant (in combination with a sedative) leads to a complete abolition of
this side effect (26). Increases in heart rate and systemic blood pressure are not influenced by muscle
relaxants because these side effects are a result of increased sympathetic output.
Our literature search detected a single clinical study dealing with physiologic aspects other than gas
exchange and hemodynamics after CP. MacLean et al. (27) proved that CP positively influences
maximum expiratory flow rates in mechanically ventilated patients, and this effect could even be
augmented when administering an increased pressure on the epigastric area of the patient treated.
Weissman et al. (28) demonstrated in 23 mechanically ventilated patients that CP met with the most
pronounced variations of vital signs when compared with other routine daily intensive care activities.
CP caused an average increase in oxygen consumption of 38% and an 35% increase in CO 2 production as
well as marked increases in heart rate and systemic blood pressure when compared with spontaneous
movements, physical exam, presence of visitors, bathing, dressing, and taking chest radiographs.
Administration of 3 µg/kg fentanyl immediately before beginning CP clearly attenuated the
hemodynamic response (heart rate, systemic blood pressure, cardiac output, PaO 2, PaCO2 and minute
ventilation) to CP (29). In contrast, 1.5 µg/kg fentanyl was not superior to placebo when comparing
those above-mentioned vital signs.
We were unable to find a single study dealing with the influence of CP on the weaning process or
weaning strategy and the duration of mechanical ventilatory support. All available data are confined
to short-term effects such as hemodynamics, gas exchange, or lung function as acute changes after CP.
Therefore, we do not know from clinical data whether CP really contributes to shortening the duration
of mechanical ventilatory support.
Study with Research Animals. Zidulka et al. (30) demonstrated in mechanically ventilated dogs after
muscle relaxation that percussion of the lungs with cupped hands (comparable with the clinical
setting) leads to esophageal pressure swings of 10-17 cm H2O (1.0-1.7 kPa). Consecutive
histopathologic examinations of the lungs immediately after termination of the treatment and killing
of the animals showed large atelectatic areas adjacent to the areas of the chest wall where CP was
administered. Moreover, there were atelectatic areas on the surface of the opposite lung to be seen
that could be best described as a contra-coup effect. Zidulka et al. speculated that worsening of
oxygenation, demonstrated in numerous clinical studies during and immediately after CP, happens
because of the induction of atelectasis in treated lungs. They recommended giving patients a couple of
deep breaths after termination of CP to overcome ventilation-perfusion mismatch caused by the
formation of atelectases.
Special Properties of Lungs in Pediatric Patients. The special properties of the lungs in pediatric
patients must be considered when applying therapy for respiratory failure found to be beneficial in
adult patients to children. First, closing capacity refers to the volume of gas present in the lung at the
point that small conducting airways begin to collapse. In children aged >6 yrs, functional residual
capacity exceeds closing capacity. In infants and in children <6 yrs of age, however, the closing
capacity exceeds functional residual capacity (31).
Second, the increasing chest wall stiffness with age leads to a diminishing ratio of compliance of the
chest wall:lung compliance (Cw/Cl) with age. A value of ~3-6 occurs in infancy, 2 in early childhood,
unity in young adulthood, and 0.5 in the elderly (32). For these two reasons, infants and children are
more prone to developing atelectasis associated with a variety of pulmonary diseases and CP may lead
to atelectasis in young patients after the administration of vibration and percussion to the chest wall.
Burden of Chest Physiotherapy in Children. Vandenplas et al. (33) demonstrated a significant increase
in gastroesophageal reflux prevalence while administering CP in 63 spontaneously breathing infants,
ranging in age from 1 to 4 months. Gastroesophageal reflux was defined as an episode of esophageal
pH <4 as measured by an esophageal pH probe. All three components of CP (percussion, vibration, and
postural drainage) were linked with an increased prevalence of gastroesophageal reflux when
compared with a control group. Vandenplas et al. observed that there was no timely relation of
gastroesophageal reflux episodes and coughing during treatment. They concluded that CP should only
be administered in the fasting infant because of the potential risk of developing aspiration pneumonia.
Dependent head position as part of the postural drainage regimen in CP leads to an increase in
intracranial pressure (ICP) as demonstrated by Emery and Peabody (34) in 14 mechanically ventilated
newborns with or without perinatal asphyxia. Use of a 30° head-down position resulted in an increase
in ICP from 13.8 ± 2.5 cm H2O (1.38 ± 0.25 kPa) to 17.2 ± 2.0 cm H2O (1.72 ± 0.2 kPa) and was even
augmented by a concomitant lateral position to a maximum of 25.0 ± 2.6 cm H 2O (2.5 ± 0.26 kPa).
Perlman and Volpe (35) described a significant increase in cerebral blood flow velocity and ICP after
routine suctioning of 34 preterm infants. These increases subsided only gradually after cessation of the
procedure. Similar results were obtained in 12 comatose adult patients after suctioning or
hyperinflation of the lungs as part of a regimen to clear lung secretions. ICP rose by 34% and 31%,
respectively, in comparison with baseline values before commencement of these procedures. In some
patients, ICP increased by as much as +70 mm Hg (+9.3 kPa) (36).
Raval et al. (37) reported a frequency rate of grades III/IV intracranial hemorrhages in 5/10 preterm
infants treated with CP within the first 24 hrs of life vs. a frequency rate of 0/10 in an untreated
control group. McCulloch et al. (38) observed a marked increase in skin blood flow in mechanically
ventilated newborns who received CP.
In a recent study from Bloomfield et al. (39), 220 newborn infants of all gestational ages with
respiratory failure received periextubation CP or no CP to assess its effect on the prevention of postextubation atelectasis. Postextubation atelectasis occurred in 23% of the treated and in 15% of the
untreated infants (difference statistically not significant). Moreover, a larger subgroup of infants
receiving mechanical ventilatory support beyond 28 days of life could be identified in the group
treated with CP.
Summary of the Literature Reviewed. CP in mechanically ventilated adult patients is associated with
acute changes in the following physiologic variables: a) gas exchange-decrease in PaO2, increase in
PaCO2; b) sympathetic output-increases in heart rate and systemic blood pressure; c) lung physiologyincrease in minute ventilation, increase in maximum expiratory flow rate; d) increases in oxygen
consumption and oxygen extraction in the vascular periphery (the latter especially in patients who are
unable to increase their cardiac output); and e) increases in intracranial pressure.
CP administered in pediatric patients is associated with the following: a) a higher rate of atelectasis
and a longer hospital stay; b) a higher frequency rate of gastroesophageal reflux; and c) increases in
intracranial pressure, cerebral blood flow velocity and a higher rate of intracranial hemorrhage in
mechanically ventilated newborn infants.
Closing Remarks. In mechanically ventilated children, CP cannot be regarded as a standard treatment
modality. CP must be considered as the most stimulating and disturbing intensive care procedure in
mechanically ventilated patients and should not be administered in children with low cardiopulmonary
reserve attributable to an increased oxygen consumption and increases in intracranial pressure. CP
should only be administered to critically ill patients whose respiratory gas exchange and
hemodynamics are monitored. CP should be evaluated in controlled studies that consider the length of
mechanical ventilatory support, influence on weaning the patient from the ventilatory support,
occurrence of atelectases, and length of hospital stay. Variations of response to CP in different age
groups because of changing physiologic properties such as closing capacity and chest wall compliance
should also be assessed.
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Key Words: chest physiotherapy; mechanical ventilatory support; children; vital signs; closing capacity;
chest wall compliance; suctioning; oxygen consumption; cardiac output; intracranial pressure