Post-operative Mucus Clearance

University of Groningen

Clearance of bronchial secretions after major surgeryLeur, Johannes Peter van de

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Chapter 1

3

Post-operative Mucus Clearance

Johannes P. van de Leur 1 and Linda Denehy 2

1 Center for Rehabilitation, University Medical Center Groningen, The Netherlands

2 School of Physiotherapy, Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Australia

Summarized from a chapter published in: Therapy for Mucus-Clearance Disorders, pp 503-552

Edited by Bruce K. Rubin and Cees P. van der Schans In the series of Lung Biology in Health and Disease volume 188 Exclusive editor Claude Lefant Marcel Dekker Inc, New York 2004

Post-operative mucus clearance

4

Introduction

Post-operative pulmonary complications were identified as early as 1910 by

Pasteur [1], who thought it was due to a failure of respiratory power. In 1914,

Elliot and Dingley [2] proposed that post-operative lung collapse was the result

of occlusion of the airways by mucus. Subsequent work [3-5] reported the

findings of post-operative hypoxia and lung collapse by shallow breathing after

laparotomy. Notwithstanding subsequent advances in surgery and supportive

medications, the morbidity resulting from post-operative pulmonary

abnormalities remains a significant problem. Dilworth and White [6] found an

overall incidence of post-operative pulmonary complications of 20.5%. But in

patients with pre-existing respiratory disease characterized by chronic sputum

production and airflow obstruction on spirometry, and those who were current

smokers, the incidence of post-operative pulmonary complications were as high

as 50 and 84%. These authors concluded that mucus hypersecretion is one of the

essential determinants of post-operative pulmonary complications [6].

The proposed mechanisms for pathogenesis of post-operative pulmonary

abnormalities have altered little since early 20th century. There are still two

basic theories to explain their occurrence: regional hypoventilation and stasis of

mucus [7-10].

Regional hypoventilation

There are several physiological factors that may contribute to alveolar closure;

these relate to reductions in functional residual capacity (FRC), and an altered

relationship between functional residual capacity and closing volume.

Following upper-abdominal surgery, the functional residual capacity has been

shown to decrease to approximately 70% of pre-operative value [11,12]. As

functional residual capacity falls below closing volume, closure of dependent

small airways may occur, leading to arterial hypoxemia as perfusion of airless

lung units persists [8,11]. This altered relationship may exist regionally in the lung,

even when overall functional residual capacity exceeds overall closing volume

[11,12]. The reduction in functional residual capacity has been shown to be closely

Chapter 1

5

associated with the degree of arterial hypoxemia after surgery [11]. The

consequences of the reduction in functional residual capacity are reduced lung

compliance, altered surfactant property [11], impaired gas exchange, retention

of lung secretions, and atelectasis [8].

The precise sequence and relative contributions of each of the above

mechanisms are still unclear. It is possible that they vary between patients. In

addition, it is possible that both alveolar hypoventilation and secretion plugging

coexist to contribute to post-operative lung changes [9].

Stasis of mucus

Advocates of the mucus-blockade theory contend that the primary cause of

atelectasis is the absorption of alveolar air, distal to a mucus plug in the

proximal airway, causing eventual collapse unless fresh air enters through

collateral channels [9].

Stasis of mucus may be a result of changes in the cardio-respiratory

physiology during the post-operative period. A multi-factorial approach (figure

1) may be used to explain the rationale for the prevention of post-operative

pulmonary complications by characterizing patient categories and type of

surgery. This approach may be used for setting up treatment hypotheses of

post-operative pulmonary complications.


6

Pre-operative morbidity

Increasing age is considered in most surgical literature to be a risk factor for

developing post-operative pulmonary complications. However, the definition of

the critical age varies between studies. Many papers report that an age over 60

years increases risk after surgery [13-15], while others found that an age greater

than 70 [16,17] or 75 years [18,19] is a significant risk factor. Not all studies

analyzing risk factors found age to be important [6,20-22]. The closing capacity

of the lungs increases with age [23] and as it rises above functional residual

capacity, closure of small airways can occur. In fact, after the age of

approximately 65 years, this occurs in normal adult lungs during quiet breathing

in a seated position [23,24].

Obesity and malnutrition are frequently studied as clinical risk factors for

post-operative pulmonary complications. Weight greater than 30% of ideal has

been linked to increased risk of post-operative pulmonary complications. More

recent research defined a Body Mass Index (BMI) of greater than 25 [14] or 27

[13] as a pre-operative risk factor. In these two studies, BMI was found to be a

significant pre-operative risk factor for post-operative pulmonary complications

when analyzed using multivariate statistics. Brookes-Bunn [13] reported that a

BMI greater than 27 kg/m2 increased patient’s risk of developing post-operative

pulmonary complications by a factor of 2.8. The physiological changes

associated with obesity that may account for increased post-operative risks are

a reduction in FRC, produced mainly as a result of decreased chest wall

compliance, and a lower than normal Pa02 [24]. The reduction in FRC post-

operatively is aggravated by the use of the supine position [25].

Malnutrition has been recognized as a risk factor for more than 50 years [26],

but has not been widely addressed in recent literature. Pre-operative protein

depletion may contribute to respiratory muscle weakness, leading to a

reduction in diaphragmatic muscle mass [27], loss of periodic sighing [28],

hypoventilation, and impaired immune-system function [29].

The components of cigarette smoking have major adverse effects on

cardiovascular and respiratory function as described by Pearce and Jones [30].

The effect of smoking history on the development of post-operative pulmonary

Chapter 1

7

complications however, remains somewhat uncertain. A large body of literature

supports the inclusion of cigarette smoking as a pre-operative risk factor [6,13].

Bluman et al. [32] even reported a fourfold increase in post-operative

pulmonary complications, in current- compared with never-smokers following

elective non-cardiac surgery. In contrast, some studies report no association

between smoking and increased risk of post-operative pulmonary complications

[16,33].

Pre-existing Chronic Obstructive Pulmonary Disease (COPD) is often

considered an important risk factor for post-operative pulmonary complications

[17,20,34]. It has been suggested that mucus hyper secretion is the important

factor that increases risk in these patients [23,36]. Other predictive markers

studied extensively in COPD are pulmonary-function test indices.

Surgery

General anesthesia, irrespective of the anesthetic agents used, result in a

reduction in functional residual capacity of the magnitude of 20% [11,36,37].

Alterations in the chest wall and reduced lung volumes seem to be most

important in the etiology of functional abnormalities following anesthesia.

Carryover of these changes may occur post-operatively, when several factors

conspire to further reduce lung volumes and affect gas exchange and

mucociliary clearance [38]. However, there is no evidence that general

anesthesia per se causes post-operative pulmonary complications [29]. It is

generally agreed in literature that abdominal surgery of longer than two hours

duration carry increased risk of post-operative pulmonary complications [26],

and that those longer than 4 hours are associated with a significant risk of post-

operative pneumonia in patients following upper abdominal surgery [21]. The

risk associated with duration of surgery may reflect the complexity of the

surgical procedure itself rather than the length of anesthesia administration

[33].

The site of surgery has been identified as having a major influence on the

risk of post-operative pulmonary complications [38,39]. Patients undergoing

upper-abdominal or thoracic surgery are at a higher risk of developing

respiratory problems compared to patients who are having surgery on the lower


8

abdomen or the extremities [11,21,38,40]. In recent comparative reviews the site

of surgery has also been identified as a significant risk factor [13,14]. Celli [34] in

fact, states that the site of surgery may be the single most important risk factor.

The wide variation that exists after surgery in spirometry may be explained by

different incision sites [11,12,43,44] and operation techniques. The influence of site

of surgery as a significant risk factor is explained predominantly by alterations in

diaphragmatic function caused by surgery performed in close proximity to the

diaphragm [33,45]. Ford et al. [43] demonstrated that the diaphragmatic

contribution to tidal ventilation was reduced following upper-abdominal

surgery in 15 subjects who underwent open cholecystectomy. Blaney and Sawyer

[46] measured diaphragm displacement before and after upper-abdominal

surgery in 18 subjects, using ultrasonography, and found that mean diaphragm

displacement was reduced by 57% on the first day after surgery. Dureuil et al.

[47] reported significantly less diaphragm dysfunction in lower- compared to

upper-abdominal surgery. These authors postulated that a decrease in

diaphragmatic motion following upper-abdominal surgery might result in

diminished ventilation and expansion of the dependent lung zones. Pansard et

al. [48] found diaphragm inhibition in patients after upper-abdominal surgery

as measured by changes in diaphragmatic pressure and excursion of the chest

and abdomen. These authors suggested that inhibition of the phrenic nerve was

mainly a result of post-operative analgesia. The loss of diaphragm function also

occurs in minimally invasive surgery. Erice et al. [49] described changes in

maximum trans-diaphragmatic pressure after laparoscopic abdominal surgery.

The authors therefore, posed a second hypothesis of loss of diaphragmatic

function through stimulation of the mesenteric plexus. This hypothesis was

originally discussed by Reeve et al. [50]. However, the primary cause of post-

operative dysfunction appears to be the chest as site of surgery, which causes

reflex inhibition of the diaphragm and intercostal muscles [47,51,52]. Another

possible explanation may be increased intra-abdominal pressure because of

abdominal distension, which may limit normal diaphragmatic function [9].

Pulmonary complications following thoracic surgery relate to both the site of

incision and the removal of previous healthy lung tissue [29]. A vertical

laparotomy has been reported to increase morbidity compared to subcostal or

Chapter 1

9

transverse incisions [53]. Although median sternotomy for cardiac surgery has

been reported to have less impact on respiratory function than thoracotomy or

abdominal incisions; the effects of the cardiac surgical process may increase the

risk of developing post-operative pulmonary complications [52,54,55]. Left-

lower-lobe abnormality is a frequent finding after cardiac surgery [54,56]. The

reasons are unclear, but factors that may be of influence are diaphragmatic

dysfunction, lung trauma due to retraction, compression of the left-lower-lobe

by the heart during surgery, and pleurotomy [54].

Pain and pain control

The severity of post-surgical pain may depend on the type and site of surgery,

age of the patient and their individual response to the stress of the operation;

perhaps due to the patient's personality, previous pain experience, cultural

background, and conditioning. As in acute pain, post-operative pain is often

accompanied by changes in autonomic activity that is largely sympathetic and

may consist of hypertension, tachycardia, sweating, and decreased gut motility.

Most research measures a patient’s estimate of the severity of their pain.

Literature measuring the peri-operative incidence of post-operative pulmonary

complications and methods used in its reduction often report on a patient’s pain

by using verbal rating scales or visual analogue scales (VAS). Of these, the VAS is

the best established. Pain reduces with the natural healing process [57].

Reduction in post-operative pain intensity is essential for patient comfort but

also for reducing the incidence of severe or life-threatening post-operative

pulmonary complications. Sabanathan et al. [58] suggested that pain in the

early post-operative period may be the factor most responsible for ineffective

ventilation. More recent developments in pain management include the

introduction of post-operative pain services led by anesthetists or nurses,

recognition of the possible value of pre-emptive analgesia [59,60], use of

multimodal analgesic techniques rather than single-drug administration, more

sophisticated drug administration techniques such as patient-controlled

analgesia, and use of the epidural route on surgical wards. Perhaps in future

new developments in pain management will result in higher pulmonary

function and less pulmonary complications.


10

Ineffective cough

Leith [61] and Bouros [62] defined a cough as a complicated maneuver. An

effective cough is important for transport and expectoration of lung mucus.

Several elements contribute to the efficiency of the cough [62]. Primarily, it is

believed to be a function of peak airflow velocities in the airways. Several

elements may participate in producing the initial transient supramaximal flows

[63] that are characteristic of a cough: initial high lung volume, muscle-

generated pulmonary pressures, coordinated glottis participation, and airway

compression resulting in adequate expiratory flow.

Initial high lung volume

The initial high lung volume during cough has several effects. Greater

expiratory-muscle pressure and higher expiratory flow rate are achievable. Post

abdominal or thoracic surgery lung inspiratory volumes are reduced to initially

50% of pre-operative value [12]. This may influence the efficacy of coughing.

Muscle-generated pulmonary pressures

Adequate musculoskeletal function and pulmonary compliance must be

present for an efficient cough. Pressures generated are variable and limited by

age, gender, and physical condition [64]. In the peri-operative phase, these

pressures may be reduced [49]. Two limiting factors for the production of

pulmonary pressures must be considered in the peri-operative phase. First, the

velocity of shortening of expiratory muscles can be regarded as depending on

the rate of change of thoracic gas volume. Second, peak pressures are reached

after a substantial volume has been expired in combination with the closure of

the glottis or mouth. Higher lung volumes have an advantage in production of

peak pressures due to better muscle force-length relationship and geometry. In

the peri-operative phase, these two factors are relevant, but their effect is

limited. The abdominal muscles are more active during anesthesia in a non-

paralyzed patient. However, this activity has no significant effect on the

functional residual capacity post-surgery [65]. Some of the diaphragm muscle

function may be regained by administration of medication, such as

aminophylline [66,67].

Chapter 1

11

High expiratory flow is generated through the interaction of respiratory

muscle function and gravitational forces acting on the skeletal system. In the

post-operative phase, the diaphragmatic pressures are decreased by 22 ± 16%

according to a study by Pansard et al. [48]. In the post-operative phase,

expiratory flow may therefore be limited.

Coordinated glottis participation

Among the most interesting aspects of expiratory flow during a cough are those

associated with the extremely rapid collapse of intrathoracic airways when the

glottis opens. As the equal pressure point migrates upstream in the intrathoracic

airways, negative transmural pressures are applied to airways downstream

from it. The resulting dynamic compression accounts for most of the airway

volume change. In contrast, flow from the parenchyma is sustained over time,

falling relatively slowly as lung volume decreases. The timing of the rise of flow

from the parenchyma is uncertain. Effective lung clearance is not entirely

dependent on glottis closure. Further in this chapter clearing lower airways by

sharp forced expiration without glottis closure will be discussed.

Airway compression

Airway compression results in adequate expiratory flow during breathing,

airways narrowing during coughing, and dynamic compression and contraction

of smooth muscle occurring in the airway walls. This dynamic collapse of airways

contributes to increased flow velocities. Persistent coughing, however, can

precipitate wheezing and reduce expiratory flow, and may provoke asthma in

susceptible patients. As a result of anesthesia, the airway caliber is reduced. The

airway may therefore further increase in resistance and related obstruction.

Dynamic compression [68] of the intrathoracic airway is undoubtedly an

essential part of an effective cough, as compression makes it possible for the

high kinetic energy of the expiratory flow to shift material from the airway wall.

The potential kinetic energy of flowing gas may not change, except in coronary

artery surgery, when the force-velocity behavior of expiratory muscle is

changed. After abdominal surgery a decrease in maximum flow might occur.

The reductions of, for instance, peak expiratory flow rate could also be

explained by an impairment in the voluntary contraction of the abdominal

muscles or reduced motivation due to fear of pain. Cotes [69] and Nunn [70]


12

describe peak expiratory flow as having an effort-dependent element due to

many inhibiting factors, including motivation and muscular force. Therefore,

during the post-operative phase patients might be restrained in producing

maximal flows, which are needed to cough. A change in muscle force-length

relationships may also be involved.

Impaired broncho-elevation of mucus

Mucociliary clearance is a major function of the airway epithelium. The

respiratory epithelium consists of cilia, which contribute to the normal elevation

of mucus, bacteria, and debris. Gamsu et al. [71] measured clearance of

tantalum, a low radioactive powder, which adheres to airway mucus. Patients

experienced delayed clearance of the tantalum after abdominal but not after

orthopedic surgery. Pooling of tantalum powder always occurred in the region

of the lung where volume loss was evident. They concluded that impaired

mucociliary function and mucus transport are implicated in post-operative

atelectasis and that lung volume is important in mucociliary clearance. These

authors [71], and others [3,8,72], suggest that the cumulative effects of the peri-

operative process present a significant insult to mucus clearance.

Intubation and ventilation of the patient during and after surgery will influence

the internal milieu, by providing a bypass of the vocal cord and introducing

foreign substances such as anesthetic gasses. Endotracheal suctioning is an

intervention to remove accumulated mucus from the endotracheal tube,

trachea or lower airways. During intubation or endotracheal suctioning the

normal barrier is bypassed, the lower airway is opened for an intrusion of

bacteria, viruses, yeasts, and other foreign substances. Several of these post-

operative factors may contribute to the development of lower-airway infection

that in itself may contribute to impaired mucociliary transport. Impaired

mucociliary transport in intubated patients is associated with loss of cilia rather

than ultra structural abnormalities of cilia [73]. A cause of loss of cilia function

may be the mechanical trauma during endotracheal suctioning by introducing

a suction catheter in the trachea and main bronchi and applying negative

pressure. An old study by Plum and Dunning [74] described 25 tracheostomy

patients having had routinely endotracheal bronchial suctioning. They described

Chapter 1

13

extensive damage caused by this procedure. In a post-mortem follow-up of

eight of these patients, erosion of cartilage and smooth muscle surface was

found. Different types of suctioning catheters did not change the prevalence of

bronchial trauma [75]. In an animal study by Czarnik, no change in bronchial

trauma was found between intermittent and continuous suction techniques

[76]. During an endotracheal suctioning procedure, described by the American

Association for Respiratory Care, the patient is manually hyper inflated and

hyper oxygenated [77]. An increase in ciliary beat frequency with different

concentrations of oxygen at normobaric pressures has been observed in vitro by

Stanek et al. [78]. This effect might influence the efficacy of ciliary beat and

therefore impair mucus transport. In the peri-operative phase, there might be a

combination of effects on ciliary beat. Because of medical interventions during

surgery, the bronchociliary elevator can be impaired for a period ranging from 2

to 6 days post-operatively [71].

Changes in mucus production

Respiratory mucus represents the products derived from secretion of the

submucosal glands and the goblet cells. The relationship between humidity and

temperature of inspired gas and function of the airway mucosa, suggests there is

an optimal temperature and humidity above and below of which there is

impaired mucosal function. This optimal level of temperature and humidity is

core temperature and 100% relative humidity. However, existing data are only

sufficient to test this model for gas conditions below core temperature and 100%

relative humidity. The data concur with the model in that region. No studies

have yet looked at this relationship beyond 24 hours.

The main factors contributing to abnormalities in mucus clearance

during the post-operative phase are flow reduction and decreased relative

humidity. This could lead to changes in the mucus viscosity and accumulation of

mucus. In theory, if it progresses this might lead to obstruction of airways,

plugging, atelectasis, and gas exchange abnormalities.


14

Effect of mucus evacuating techniques on peri-operative respiratory

function

Rationale for mucus evacuating techniques

In 1910, Pasteur [1] described in elegant detail, several different types of post-

operative pulmonary complications. Although pulmonary treatment regimens

were not defined, Pasteur stated in his concluding words that the deficiency of

inspiratory power would occupy an important position in the search and

determination of causes of post-operative lung complications. Beecher [4]

confirmed this in laparotomy patients in 1933. The confirmation of the inhibitory

reflex was studied by Reeve et al. [50] in 1951. Several improvements have

taken place in post-operative care. Mechanical ventilation has changed from

volume controlled, to patient triggered pressure controlled. This improvement

may be responsible for a reduction in mucus production and retention. In the

1950’s endotracheal suctioning was a non-sterile procedure, with an orange

rubber tube, that was re-used after cleansing and drying at the bedside.

Nowadays endotracheal suctioning is a sterile procedure with single use,

transparent plastic catheters. This improvement may have been responsible for

a reduction in pneumonia and pulmonary infection. With respect to post-

operative lung complications after the intubation phase, breathing exercises,

concentrating on inspiratory volume and expiratory techniques, could be

essential elements in the prevention and treatment of problems of mucus

clearance. One of the earliest publications regarding increasing inspiratory effort

through breathing exercises and manual control during expiratory maneuvers

such as coughing was described by MacMahon in 1915 [79].

A review of well-recognized physiological changes of the post-operative

period provides empirical support for the role of physiotherapy treatment to

prevent or minimize hypoventilation and secretion plugging. Supporting

evidence for this role was provided almost 50 years ago [80]. Since then, several

randomized controlled trials have reported beneficial effects of prophylactic

physiotherapy in reducing the incidence of post-operative pulmonary

complications following major surgery [40,81-85]. In contrast, several other

studies report no additional benefit of prophylactic physiotherapy [56,86,87] .

Chapter 1

15

Respiratory physiotherapy may include pre-operative assessment and

education and post-operative management. Many physiotherapy techniques

may be used in treatment of patients after surgery, with the primary aims of

improving lung ventilation, clearing excess secretions, and thereby minimizing

the risk of post-operative pulmonary complications. These may include

endotracheal suctioning with or without additional airway-clearance

techniques, deep-breathing strategies, forced expiratory maneuvers and

mobilization.

Several studies suggest that pre-operative education alone may be

sufficient for patients having upper-abdominal surgery. A change in patient

management in many centers is the use of pre-admission clinics. Patients visit

the hospital as outpatients for admission details and information up to 1 to 3

weeks before surgery. They are then admitted as inpatients on the day of

surgery. If patients, undergoing upper-abdominal surgery or cardiothoracic

surgery, benefit from pre-operative physiotherapy, the physiotherapist needs to

be involved in the pre-admission of these patients. Research, particularly in

cardiac surgical patients, has shown positive peri-operative benefits from pre-

admission education [88,89]. It is essential that more research should be

performed in the identification of pre-operative risk factors, developing a risk-

factor model for clinical use and examining the efficacy of post-operative

physiotherapy in specific patient populations (especially thoracic and

esophageal surgery) using a no-treatment control group and multi-center

research if possible. More comparative research, including the use of no-

treatment control groups, is necessary to evaluate the specific continuing role of

physiotherapy for patients following major surgery. Furthermore, the

comparative efficacy of physiotherapy interventions, especially in relation to

mucus clearance, needs to be evaluated.

During the pre- and early post-operative phase patients are usually

intubated. Intubated patients have a tendency to retain mucus due to a

combination of various reasons: obstruction in mucus transport due to

ineffective cough, impaired broncho elevation of mucus (endotracheal tube,

mechanical ventilation, damaged cilia, reduced flow) and changes in mucus


16

production (increased amount or reduced viscosity). In these circumstances

endotracheal suctioning is usually performed.

In 1993, the American Association for Respiratory Care [77] described a

consensus guideline in performing endotracheal suctioning. This intervention

consists of patient preparation, the suction procedure and patient monitoring.

The patient’s preparation may include hyper oxygenation, with 100% oxygen,

longer than 30 seconds prior to the suctioning procedure. This could be

accomplished by adjustment of the mechanical ventilator or by manually

ventilating the patient with a resuscitation bag.

Manual hyperinflation as described by the American Association for

Respiratory Care [77] defined manual hyperinflation in the guideline for

endotracheal suctioning as a technique to hyperventilate with a resuscitation

bag by an increased rate and/or tidal volume. The goal of using manual

hyperinflation is to maintain oxygenation, to facilitate a sigh, to increase

expiratory flow rate [90], to increase sputum clearance [91] and to increase

inspiratory volume [91,92]. In a survey of manual hyperinflation in Australian

hospitals, Hodgson found that in 91% manual hyperinflation was used as a

physiotherapy treatment technique [93]. In a vitro setting, Maxwell et al. [90]

found that if PEEP was maintained by bag compression, a reduction in

expiratory flow rate was found. Clarke [94] suggested the increased potential of

baro-trauma during manual hyperinflation.

To increase expiratory flow manual chest wall compression can be

applied in conjunction with manual hyperinflation. In the rational on improving

expiratory flow, the technique of manual chest wall compression may be an

adjunct to the treatment rational, but in clinical practice, this technique may

oppose some problems in post-thoracic and abdominal surgery patients. To our

knowledge, data on chest wall compression with or without manual

hyperinflation has never been published.

The entire suctioning procedure, as well as the placement of a suction

catheter through an artificial airway into the lower airway, trachea and right or

left main bronchus, should be deployed as a sterile technique. Negative pressure

is applied as the catheter is being withdrawn from the airway. The duration of

each pass of a suction catheter into the artificial airway should be 10–15 seconds.

Chapter 1

17

Suction pressures should be as low as possible, to clear secretions effectively.

Indications are listed in this guideline:

coarse breath sounds or noisy breathing,

increased peak inspiratory pressures or decreased tidal volumes,

visible secretions in the airway,

changes in flow or pressure,

suspected aspiration,

clinically increased work of breathing,

deterioration of arterial blood gas values,

radiological changes consistent of mucus retention,

the need to obtain a sputum specimen,

the need to maintain patency and integrity of the artificial airway,

the need to stimulate a cough, and

presence of pulmonary atelectasis or consolidation.

Patient monitoring should consist of auscultation, interpretation of vital signs,

pulse rate, blood pressure, respiratory rate or pattern, cough effort, sputum

characteristics and ventilator parameters. These clinical “data” should be

monitored prior, during and after endotracheal suctioning to indicate and

evaluate the procedure. Evidence in literature for the indication to perform

endotracheal suctioning is not clear. The rationale for this intervention is to

maintain airway patency and reduce pulmonary complications. The assessment

for the indication to perform endotracheal suctioning should be clinically based

on objective indications and should include patient/ventilator system

interaction. Prevention of pulmonary infections and maintenance of airway

patency are cited as possible benefits. However, there are no clinical trials to

support these assumptions.

In 1976, Lefrock et al. [95] described a clinical trial of 68 patients, without

patient specifications, a prevalence of 26% infection rate. Similar prevalence

was described by Deppe et al. [96] in 1990, comparing two treatments in 84

patients. In a vitro study of 10 endotracheal tubes, Hagler [97] described that

the introduction of a suction catheter transported 60.000 colonies of bacteria to

the lower airways and the use of saline instillation transported 300.000 colonies

of bacteria to the lower airways. In theory this suggests that invading the lower


18

airways may be beneficial, but may also introduce a risk factor for pulmonary

complications.

Endotracheal suctioning may have undesired adverse effects: several

studies have reported cardiac arrhythmia [98] and oxygen desaturation [99-

101] during suctioning. Cardiac arrhythmia was seen by Stone et al. [98] during

suctioning in 26 patients post cardiac surgery. Adlkofer and Powaser [99]

reported a decrease in oxygen tension of 20 mmHg in 64 patients post cardiac

surgery. Eales [100] found a decrease in oxygen tension after suctioning of 12

mmHg. Brown et al. [101] described an oxygen desaturation of more than 4% in

a medical population of 22 patients. Several studies have reported the

discomfort of endotracheal suctioning in ICU patients [102-104]. These studies

show that endotracheal suctioning is remembered by at least 40% of the ICU

population. Evaluation of effects of endotracheal suctioning based on the

recollection and memory of patients is difficult because the recollection and

memory of this period is varied. Studies describing memories of the ICU period in

general describe a large population with no recollection, but also patients with

hallucinations or with detailed facts.

The use of additional specific airway-clearance techniques, like postural

drainage and percussion etc., may have limited value because of post-operative

pain and incision site. Patients with suppurative lung disease are at high risk of

developing post-operative pulmonary complications. These patients should be

assessed and treated by a physiotherapist in the immediate pre-operative

period, with the aim of reducing secretion volume. In these patients, it may be

necessary to delay surgical intervention to mid-morning in order to allow

clearance of secretions prior to anesthesia [105]. Close post-operative monitoring

is essential and effective analgesia is vital (even after minor procedures) to

enable patients to perform airway-clearance techniques [105]. The addition of

humidified supplemental oxygen may also be of benefit to this patient group,

both intra- and post-operatively [105,106], because reduced humidification

alters ciliary function [107]. Nebulized saline, and in some cases bronchodilators,

following surgery may be helpful in improving secretion clearance [106]. In

general however, the use of airway-clearance techniques is less common

following surgery for patients without suppurative lung disease.

Chapter 1

19

After the intubation phase patients need to maintain sufficient lung

volume to avoid pulmonary complications. To maintain sufficient lung volume

deep-breathing exercises could be used to increase the level of breathing above

closing capacity, a level where airways collapse. Deep-breathing strategies

aiming to improve lung volume are performed from functional residual

capacity to total lung capacity. They are aimed at increasing lung volume,

redistributing ventilation, improving gas exchange, increasing thoracic

movement, and helping in secretion mobilization [108]. These have been the

mainstay of physiotherapy for this patient group. The exercises commonly used

are directed at thoracic expansion exercises, diaphragmatic breathing and

sustained maximal inspiration.

Most deep-breathing exercises may also be used in combination with

gravity-assisted drainage and forced expiratory maneuvers. Variations in

inspiratory flow are thought to alter the distribution of ventilation [108]. To

improve ventilation to dependant lung regions, which are the most affected

following major surgery, a slow inspiratory flow is recommended. As lung

volume increases, the influence of flow on distribution of ventilation is reduced

[108]. Based on a study by Ferris and Pollard, the number of maximal

sequential breaths needed for physiological effects is thought to be five,

performed once every waking hour [109]. The time spent on breathing exercises

and respiratory maneuvers described as most beneficial is reported to be

approximately 20 minutes [84]. Blaney and Sawyer [46] studied diaphragmatic

motion using ultrasonography in 18 patients following upper-abdominal surgery.

The authors compared three breathing strategies with the patients sitting,

receiving verbal instruction to take only deep breaths, and coached in

diaphragmatic breathing and thoracic expansion exercises pre- and post-

operatively. Results showed a significant increase in diaphragmatic excursion

following surgery when the two tactile, or “hands-on”, breathing techniques

were compared with verbal instruction alone [46]. The addition of a 3-second

breath hold at total lung capacity has been recommended [110,111]. A sustained

maximal inspiration mimics a sigh or yawn and aims to increase

transpulmonary pressure [111]. It may also allow time for alveoli with slow time

constants to fill. Redistribution of gas into areas of low lung compliance utilizing


20

collateral ventilation pathways and lung interdependence may re-expand

collapsed alveoli [110,112]. If regional ventilation is reduced as a result of

secretion plugging, the re-expansion of collapsed alveoli may allow air to move

behind the secretions and assist their removal using forced expiration techniques

[113,114].

Incentive spirometry was developed to stimulate the patient to perform

deep-breathing exercises under supervision or independently. Various inspiration

devices have been invented to stimulate the patient visually to increase the

total lung capacity, either by marking the inspired volume in liters (or ml), or by

transporting one or more balls on inspired flow. Thruvol (Argyle Sherwood

Medical, USA) Coach (DHD, USA), and Airlife (Allegiance, USA) are examples of

incentive spirometers used in clinical situations. Different devices all aim to

stimulate the patient to increase inspiration and breathe better and avoid

pulmonary complications. Incentive spirometry volumes underestimate the

maximum inspiratory capacity. The incentive spirometers with a low flow rate

tend to use less work of breathing compared to the flow activated incentive

spirometers.

Many conflicting articles have been written about its physiological effects

[115-120] or absence of them [121-123]. Other benefits such as cost-effectiveness

have been described by Hall et al. [14] and refuted by Denehy et al. [124] and

others [125,126]. The use of incentive spirometry has been evaluated in different

patient categories such as those undergoing cardiac surgery and in a pediatric

population [127,128]. Many questions regarding its effectiveness remain

unanswered. The patient category most likely to benefit from this tool are high-

risk patients, after thoracic or upper-abdominal surgery [121,129]. In a recent

well-designed study, it was reported that the addition of incentive spirometry to

physiotherapy, including deep-breathing exercises and early mobilization, in 67

patients did not significantly alter the incidence of post-operative pulmonary

complications following thoracic and esophageal surgery [130].

Evidence supporting their efficacy in achieving these aims is scant [131-

133] and often conflicting. However, O'Donohue [134] and Celli [33] both stress

the importance of regular maximal inspirations in a prophylactic peri-operative

treatment regimen, whereas others question the need to include breathing

Chapter 1

21

exercises at all [56,135]. The effects of breathing exercises, in isolation, in aiding

secretion clearance, have not been studied. The efficacy of deep-breathing

strategies in clinical practice for reducing post-operative morbidity has been

studied by several authors. Different methods of post-operative prophylaxis

have been compared. It seems apparent from these studies that different

breathing strategies may be equally effective in thoracic patients [123,136,137]

and in abdominal patients [24,44,56,86] and that some form of deep breathing

is better than no intervention [33,81,84] in minimizing the incidence of post-

operative pulmonary complications.

With respect to expiratory techniques, like huffing and coughing, little

research exists that compares the efficacy of mucus-mobilizing techniques in the

post-operative phase. Forced expiration is one technique used for mobilizing

and expectorating excess bronchial secretions [114]. The technique incorporates

one or two forced expirations (huffs) and breathing control. Extensive

information outlining the definition and efficacy of this technique has been

published [114,138]. Much of this research was performed in medical patients

with copious secretions. The specific role of the forced expiratory technique in the

management of patients after surgery has not been studied. Many studies

support its efficacy in clearing excess secretions. However, teaching the correct

performance of the huff from mid-to-low lung volume with the glottis open

may be best done pre-operatively. Coughing with wound support should be

encouraged as part of any prophylactic treatment regimen following major

surgery.

The cardiovascular and respiratory effects of immobility and bed-rest

have been well documented [131,139-141]. These include reduced lung volumes

and capacities, especially functional residual capacity; reduced Pa02; decreased

V02 max, cardiac output, and stroke volume; increased heart rate; and

orthostatic intolerance [139]. A model of the interaction between pulmonary,

cardiac and muscular function was described by Wasserman [142].

The goal of ambulation of post-operative patients is exercise at a level

sufficient to increase minute ventilation and cardiac output, within safe

physiological limits [140]. Given the previously described physiological changes

associated with major surgery, a technique that can increase ventilation may


22

improve outcome in this patient group. Effective analgesia is necessary in order

to actively ambulate patients [58]. It has long been recognized that body

position affects respiratory parameters [143,144]. Adoption of the upright

position and increased tidal volumes may aid in recruitment of alveoli in

dependent lung zones, improve ventilation/perfusion (V/Q) matching, and

promote secretion evacuation [140,145].

Several studies have examined the efficacy of this technique in isolation.

Dull and Dull [146] and Jenkins et al. [147] advocate early ambulation in the

respiratory prophylaxis of patients following coronary artery surgery. No

additional benefits of breathing exercises or incentive spirometry were found in

either study. Hallböök et al. [136] reported similar results in patients following

cholecystectomy. Wolff et al. [148] studied the effects of exercise

hyperventilation compared with eucapnic hyperventilation using radioactive

isotopes in normal subjects. The authors reported a significant improvement in

secretion evacuation with exercise hyperventilation.

Summarizing, post-operative mucus clearance techniques should be used

to target high-risk patients (increasing age, history of respiratory disease,

morbidly obesity, cardiothoracic or upper-abdominal surgery) as the literature

to date suggests. The type, dosage, and frequency of post-operative

physiotherapy techniques in the Intensive Care Units utilized in different

countries (and within the same country) also vary significantly [149,150]. Within

Europe large differences occur between the work field of physiotherapists [149].

It seems that many methods of treatment may be effective for prophylaxis, and

the specific method used will ultimately depend on individual patients’ needs,

available resources [33], and, to some extent, the training and experience of the

physiotherapist.

Outcome measures used to test the efficacy of techniques used by

physiotherapists vary considerably, as does the definition of the same outcome

across numerous studies. Reassessment after surgery may be required to assess

post-operative risk factors (pain levels, ambulation). Ambulation should be

encouraged as soon as possible following surgery. Patients may need respiratory

physiotherapy management for 1 or 2 days after surgery.

Chapter 1

23

Post-operative mucus clearance in patients after high-abdominal and thoracic

surgery is daily routine. Our daily routine needs to be evaluated especially

during and after the intubated phase. Evidence based literature describes little

indications on endotracheal suctioning. The following questions were to be

answered:

1: Is an on-demand procedure of minimally invasive airway

suctioning bio-equivalent in ICU outcome compared to routine

procedure of endotracheal suctioning without its undesirable side

effects?

2: What is the difference in recollection during routine endotracheal

suctioning and minimally invasive airway suctioning?

3: What is the difference in stress-hormonal response in ICU patients

to the two procedures of airway suctioning; routine endotracheal

suctioning and minimally invasive airway suctioning?

4: What is the discomfort and memory of facts recalled by patients

post ICU stay?

5: Is the clinical observation of breathing and pain predictive for the

decline of pulmonary function in post surgical patients?

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132. Sampson MG, Smaldone GC: Voluntary induced alterations in regional ventilation in normal humans. Journal of Applied Physiology 1984, 56: 196-201.

133. Roussos CS, Fixley M, Genest J, Cosio M, Kelly S, Martin RR: Voluntary factors influencing the distribution of inspired gas. Am Rev Respir Dis 1977, 116: 457-467.

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135. Jenkins SC, Soutar SA, Forsyth A, Keates JR, Moxham J: Lung function after coronary artery surgery using the internal mammary artery and the saphenous vein. Thorax 1989, 44: 209-211.

136. Hallböök T, Lindblad B, Lindroth B, Wolff T: Prophylaxis against pulmonary complications in patients undergoing gall-bladder surgery. A comparison between early mobilization, physiotherapy with and without bronchodilatation. Annals Chirurg Gynaecology 1984, 73: 55-58.

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145. Jenkins S, Soutar SA, Gray B, Evans J, Moxham J: The acute effects of respiratory manoeuvers in post-operative patients. Physiotherapy Practice 1988, 4, 63-68.

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147. Jenkins SC, Soutar SA, Loukota JM, Johnson LC, Moxham J: Physiotherapy after coronary artery surgery: are breathing exercises necessary? Thorax 1989, 44: 634-639.

148. Wolff RK, Dolovich MB, Obminski G, Newhouse MT: Effects of exercise and eucapnic hyperventilation on bronchial clearance in man. Journal of Applied Physiology 1977, 43: 46-50.

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Post-operative Mucus Clearance