Mobilizing patients in the ICU: evidence and principles of practice.
This article describes the scientific literature supporting mobilizing patients in the ICU to achieve two goals; first to optimize oxygen transport and the function of its supporting systems and second to reduce multisystem complications and maximize functional recovery. These goals span the three levels of the ICFDH, namely, structure and function, activity, and social participation, which is viewed as being central to the individual's quality of life. These two goals need to be viewed as distinct by the physical therapist. The overall goal is to expedite recovery, reduce risk of complications, and discharge the patient home to the community with commensurate cost benefit.
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What is oxygen transport?
Oxygen transport refers to the delivery (DO2) and consumption (V[O.sub.2]) of oxygen in the body and reflects the transport of oxygen from the ambient air to each cell of each tissue. (3,4) Figure 2 shows the components of oxygen transport, D[O.sub.2] and V[O.sub.2]. This process reflects the quality of the air, and the integrity of the airways and lungs, the blood, the heart, the peripheral circulation, and the structures that support oxidative phosphorylation at the cellular level. For efficient oxygen transport, carbon dioxide, a by-product of respiration, needs to be removed. Improvements in oxygen transport result in reduced risk to life and complications associated with restricted mobility. The patient's capacity for activities of daily living and a quality of life are increased correspondingly.
General Distinctions between Patients who are Severely Acute vs. Chronically Ill
To understand the benefits of and the rationale for mobilizing patients in the ICU, physical therapists need a detailed understanding of the factors that threaten or impair oxygen transport. Such understanding provides the basis for the assessment, on-going evaluation, and prescription of interventions. The parameters of a mobilization intervention are comparable to the prescription of exercise for patients who are not acutely ill, and include the type of mobilization, its intensity, duration, frequency and course. This article supports the need for individualized decision making for optimal patient outcome and safety. It requires a process utilizing individualized clinical judgment, rather than advocating a clinical practice guideline or mobilization protocol which have been periodically advanced. (5,6)
Several factors distinguish mobilization prescribed for the patient who is acutely ill and exercise prescribed for the individual with one or more chronic conditions. One primary difference is the assessment of readiness for mobilization for a patient in the ICU. The criteria for readiness of a patient who is in the ICU necessitate that individual is able to cooperate, and is relatively hemodynamically stable and able to tolerate the increased physiological stress of mobilization, that is, D[O.sub.2] exceeds the V[O.sub.2] demand. (7) This means that the patient has good cardiac reserve and adequate oxygenation of the blood, well beyond the metabolic need. The therapist will need to carefully measure and consider the distinct variables represented in Figure 2. Prior to treatment and even assessment, the physical therapist needs to assess the patient's relative V[O.sub.2] demands to ensure that he or she has sufficient D[O.sub.2] capacity. In addition to the factors that can limit D[O.sub.2], V[O.sub.2] demands can be substantially altered in the patient in the ICU. For example, basal metabolic demands change with body temperature and circadian rhythm, (8) physical and psychological stress of illness or injury, post surgical healing and repair, and pharmacologic agents.
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Other considerations for a patient's readiness to be mobilized include musculoskeletal, neuromuscular, or surgical precautions such as spinal cord clearance for someone with a spinal injury, or intracerebral pressure and perfusion clearance for someone with a head injury. The therapist must work within whatever limitations are imposed hemodynamically and physically as body positioning and mobilization are progressed. Also, patients on neuromuscular blockade or who are unconscious for other reasons will not be able to be actively mobilized. Much can be done in the meantime until the patient becomes more aware and arousable.
Another difference in prescribing mobilization for patients who are acutely ill vs. exercise for those who are chronically ill includes the need to assess and monitor more organ systems. The status of acutely-ill patients can change quickly, thus, the patient is closely monitored at all times. Response-dependent management requires that the patient's moment-to-moment status is monitored by the physical therapist before, during and for a period after intervention.
The results of on-going assessment include evaluation of hemodynamic status, and the results of frequent laboratory findings, and response to medications. These parameters are used to guide each treatment session. In addition, mobilization challenges, e.g., patient care and nursing procedures and preparation for portable X-rays, replace maximal exercise tests to establish optimally therapeutic and safe mobilization parameters. The intensity of mobilization is usually low, duration short, and frequency high, compared with a person who is chronically ill who can exercise at a higher intensity for longer duration. In this latter case, the frequency of the exercise sessions can be less to achieve the conditioning benefits to oxygen transport and its supporting systems.
Profile of the Patient in the ICU: Four Factors than Threaten or Impair Oxygen Transport
The primary criterion for admission of patients to the ICU is oxygen transport threat or dysfunction. Oxygen transport can be threatened or impaired by four categories of factors (Table 1) that are described below. Each factor needs to be considered in explaining assessment findings. Any abnormal findings need to be remediated by addressing each of these factors directly whenever possible. The physical therapist needs to understand the role of each of these factors and the degree to which they can be addressed by physical therapy. In some cases the assessment may require modifications to the desired intervention.
In addition to the evidence over the past 60 years supporting mobilizing patients even when critically ill, the evidence supporting conventional physical therapies such as airway clearance including postural drainage are equivocal. (10,11) Methodological issues related to research design may explain in part the limitation of these time-honored procedures. One of the first clinical studies regarding the positive benefits of mobilizing acutely ill patients was published 45 years ago and was largely unnoticed. (12)
A patient can have pathology that affects oxygen transport, and such pathology can be categorized as acute, chronic or acute on chronic. Acute pathology, directly affecting oxygen transport, usually involves one or more steps in the oxygen transport pathway. Most commonly seen in patients in the ICU, such pathology includes obstructive and restrictive lung conditions, heart conditions, and hematological conditions. In addition, dysfunction of other systems can have a secondary effect on oxygen transport. (13) These include conditions of the musculoskeletal, neurological, gastrointestinal, renal, liver, integumentary and endocrine systems, and most notably diabetes and thyroid conditions, as well as nutritional disturbances such as obesity, cachexia and anorexia. Given the lifestyle conditions that are pandemic today, a combination of these conditions or their risk factors often presents concurrently.
The physical therapist needs to conduct a comprehensive assessment to determine precisely the adequacy of oxygen transport at each of its steps, and in turn, the degree to which each of the four factors threatens or impairs oxygen transport overall. Such an assessment will identify those interventions that warrant being exploited in the patient's care. Mobilization is considered in conjunction with body positioning given that the goal of mobilization is to have the patient 'upright and moving' in order to address oxygen transport threats and deficits first, and then functional capacity.
Recumbency and Restricted Mobility
Patients who are severely ill such as those who are candidates for ICU admission are often in bed, hence, recumbent and have restricted mobility. Being recumbent and being inactive have distinct physiologic consequences that compound the threat to oxygen transport or its dysfunction (Table 2). These effects have been well known for several decades, (33-36) and in more recent decades the mechanisms of these effects have been elucidated.
First, recumbency, that is, when the patient assumes a reclined position for prolonged periods, intravascular fluid is lost through the kidneys reducing circulating blood volume. Reduced blood volume predisposes the patient to thrombus formation in the deep veins and lethal emboli. This hemodynamic consequence of recumbency is considered more important as a determinant of bedrest deconditioning than its direct effect on deconditioning secondary to its effects on the lungs, the heart, the blood, and the peripheral muscles. Thus, the effects of recumbency must be managed from both perspectives. Positioning the patient upright as soon as possible and as often as possible is a therapeutic goal that is distinct from the goal of mobilization, at least in the patient's initial care.
When patients are medically unstable, body positioning becomes a predominant component of physical therapy used to maximize D[O.sub.2]. Sitting upright for example shifts circulating blood volume dependently, and facilitates diaphragmatic motion and lung volumes and capacities and reducing closing volume of the dependent airways. Body positioning studies often use more than one body position, usually a more erect position, and even so-called extreme body positions to show the simulated effect of moving a patient from one extreme body position to another so that it triggers a greater physiologic adjustment. (23,37-40)
Second, restricted mobility has multisystem effects. Systems affected include those involved in oxygen transport, e.g., the cardiovascular and respiratory systems, peripheral muscle and nerve function, peripheral circulation, skin integrity, and endocrine function, in particular, glucose metabolism. Mobilization is prescribed to exploit the benefits on the cardiovascular, respiratory, hematological, renal, as well as the musculoskeletal and neurological systems to support increasing levels of physiologic work demands. Secondary effects include reduction of multisystem complications of intensive care including pressure ulcers, myopathies and neuropathies, (24,41) and potentially psychoses and depression.
Studies of passive whole body movement, e.g., kinetic and rotating beds for patients who are severely ill have reported benefits of extreme body position changes. (42,43) Patients tended to have better outcomes when they were exposed to on-going body position changes rather than when they are more static or only changed passively every few hours. Mobilizing patients may possibly simulate these effects if the criteria for instituting whole body movement are met.
Methodological challenges are found in the literature related to evaluating the efficacy of physical therapy in the ICU. For example, most studies do not report the use of a mobilized control group when examining other physical therapy interventions that necessitate changing the patient's body position or having the patient assume a given position. Patient movement is often coupled with extreme changes in body position, e.g., from supine to upright. Because of the profound effects of both body positioning and mobilization on oxygenation, these warrant being exploited maximally. All physical therapy studies on interventions of potential relevance to the ICU need to control for these variables (namely, mobilizing, changing the body position or both) where feasible to avoid confounding their effects with those of the intervention of particular interest. (44)
Patients with chronic lung disease admitted to the ICU in acute respiratory failure have improved outcomes with greater mobilization. (45) Further, a patient's outcomes are worse the more deconditioned an individual may be prior to the ICU admission. (46) The benefits of upright and moving in the care of the patient in the ICU have been recently reviewed. (47)
Extrinsic Factors Related to the Patient's Care
Extrinsic factors are those related to the needs of interventions or the interventions themselves in the patient's care. Because of the severity of the threat to survival, patients in the ICU are treated aggressively. They often have one or more interventions that can adversely affect oxygen transport directly or indirectly. Medications for example, prescribed to reduce pain or anxiety, can reduce a patient's arousal and capacity to cooperate and participate actively throughout the treatment session. (48) Neuromuscular blockers can predispose a patient to myopathy and neuropathy. (49) Vasopressor medications are often prescribed for patients in the ICU. These drugs can interfere with a patient's capacity to respond appropriately to body position changes and movement. Supplemental oxygen is commonly administered to patients in the ICU to improve the driving pressure of oxygen, which reduces the work of breathing and of the heart. Oxygen support can thus reduce the physiological stress of oxygen delivery overall. However, noninvasive interventions associated with physical therapy, for example, body positioning and mobilization, are prescribed to augment D[O.sub.2] and help minimize the concentration of supplemental oxygen. When supplemental oxygen dosages exceed an Fi[O.sub.2] of 0.5 (50% oxygen), oxygen can contribute to atelectasis (de-nitrogen atelectasis), and prolonged periods of higher concentrations can lead to permanent lung damage.
Other interventions and monitoring requiring lines and leads may limit the movement of the patient and positioning alternatives. Surgical incisions can impair breathing effort and limit stress over the affected area. Both internal and external fracture fixation devices can limit body positioning alternatives and the capacity of the patient to weight bear and walk.
Intrinsic Factors Related to the Patient
Intrinsic factors are those related to the patient other than his or her primary pathology that can impair oxygen transport. Patients, particularly those who are older, can have complicated medical histories that can impact the oxygen transport status by compounding the effects of an immediate illness or medical concerns. Age is an independent risk factor for greater disease severity, poorer treatment response, and prolonged ICU stay. Gender in some situations could impact the patient's status. One example is the effect of pregnancy as a superimposed intrinsic factor for a given individual. Because lifestyle conditions can take several decades to emerge, these usually appear in middle to later life. Although a person may be asymptomatic for these conditions prior to admission, the stress of illness may lead to their manifestations. A patient with a smoking history, particularly if a current smoker, can be expected to have airway and lung damage and reduced lung function commensurate with years and amount smoked. This reduced lung function premorbidly may produce an extended period of intubation and prolonged dependence on mechanical ventilation. Although such dysfunction may not have manifested prior to this admission, it can complicate the patient's status and recovery.
A patient who is overweight or obese similarly can also be expected to have this factor confound the clinical presentation even though the individual may not have experienced any secondary effects of being overweight prior to this episode of illness. Being overweight predisposes the patient to increased risk of complications and poorer prognosis. Poor nutritional status secondary to poor food choices can compromise healing and immunity, hence recovery. A patient who has poor bone density pre-morbidly can be expected to have greater functional bone loss with prolonged ICU stay than someone with good bone density. A patient who is aerobically fit, that is, exercises regularly and has a well conditioned oxygen transport system, can also be expected to respond better to ICU care, have fewer complications, and if complications arise, the individual is likely to recover more quickly leading to a faster discharge. The poorer the patient's health at the time of the episode of care, the worse the prognosis and outcomes anticipated.
The physical therapist needs to be aware of the four categories of factors that can threaten or impair oxygen transport, specifically its delivery and consumption. Knowledge of those factors that confound a patient's presentation in the ICU will identify to the physical therapist those outcomes that need to be most closely monitored. In addition, knowledge of these factors will identify what interventions must be implemented. Such an assessment highlights the importance of addressing factors that impact oxygen transport directly, rather than working with a singular focus on pressure ulcers and deconditioning, as important as the prevention of these may be.
The physical therapist does not practice in isolation. She or he works closely with the team to effect whole body benefits through interventions to address impairments, activity limitation and social participation. Such holistic approach and teamwork is the focus of more published articles related to ICU care. (45,50,51) Also, mobilization in the ICU is strongly suggestive of improved outcomes of patients who are mechanically ventilated including weaning outcome. (52-56)
The International Classification of Functioning, Disability and Health (1) provides a meaningful schema for measures and outcomes of relevance to the patient. Contemporary care should include a quality of life measure and activity measures as well as measures of structure and function (impairment). Quality of life can be measured with established tools. If the patient is unable to respond to the questions, which is often the case in the ICU, valid responses can be provided by proxy through a relative or close friend.
Many invasive and non invasive measures and outcomes can be used to assess or evaluate the steps of the oxygen transport pathway. (57) Ratings of perceived exertion or breathlessness have a role in the management of patients who are able to respond appropriately. In addition, subjective pain responses are important to monitor and record when appropriate. Most importantly, when these measures and outcomes have been identified and assessed in the initial assessment, they need to be repeated at regular intervals to gauge the response to intervention over time. Progression of the mobilization stimulus is gauged in a response-dependent manner, vs. being based on the results of a graded exercise test in patients who have chronic conditions and are medically-stable. Although positive outcomes will likely reflect ICU care overall, short term changes in relevant measures over the course of a single treatment or successive treatments will identify to the physical therapist the mobilization parameters that lead to a positive outcome or to no change, or may introduce a potentially negative outcome. Attention to these outcomes will enable the therapist to change the mobilization prescription immediately so that positive outcomes are maximized and adverse ones minimized.
Although not in the initial assessment perhaps, activity measures will take the form of number of repetitions of an active exercise with or without resistance or assistance, number of steps or distance walked including the timing and number of rests. Such activity may be limited by certain criteria, for example, a given heart rate, blood pressure or oxygen saturation in arterial blood. Variants of such activities include number of steps taken in place or the number of limb movements that can be repeated. Changes in these outcomes can be used as an index of oxygen transport improvement over time. In the early stages of care, when the patient's status may be labile, the number of times the patient can sit over the edge of the bed over 24 hours, and the duration each time can be recorded. The number of transfers to chair over 24 hours, and the time spent in the chair at bedside, are also indices of progressive oxygen transport improvement and improved strength and endurance. Weights can be used judiciously to assess limb strength and endurance; both weight and number of repetitions can provide a measure of change over time. The level of assistance should also be recorded as this also reflects the level of intensity that the patient assumes on his or her own. During walking for example, more than one person may be required for support as well as safety reasons. The normal precautions are taken to ensure the resistive weight is not excessive and that breath-holding is avoided. Breath-holding increases intrathoracic and abdominal pressures and can reduce venous return and stroke volume, both determinants of cardiac output, hence, D[O.sub.2].
Over several decades, studies have shown the benefits of movement in a range of acutely ill medical and surgical patients, (36,58-60) and further, the effects of the upright position have been well established and may well contribute to the benefits of mobilization that often is conducted in the more erect or upright position. (16,17,34,61)
Similar to the prescription of exercise for healthy people or those with chronic conditions, mobilization is prescribed based on type, intensity, duration, frequency, and course. The acute physiologic multisystem effects of mobilization or low intensity exercise are clinically important and are exploited to reduce oxygen transport threats or reverse or mitigate impairment (Table 3). Fundamental yet qualitative distinctions exist between mobilization prescribed for individuals who are critically ill and exercise for those who are stable with chronic conditions. Table 4 compares these distinctions.
First, however, assessment of the four factors that can threaten or impair oxygen transport will identify factors that need to be addressed to optimize the parameters of the mobilization prescription. For example, those lines or leads that compromise body positioning and movement, need to be identified, and appropriately managed or clamped for the duration of the mobilization session. Thorough understanding of these lines and leads is essential in prescribing mobilization and body positioning safely and therapeutically. At rounds, medications need to be reviewed in the event that a patient is unable to cooperate with treatment because of being excessively sedated. Alternative pharmacologic agents can be discussed with the ICU pharmacologist.
Discussion with the team may be needed in challenging cases to confirm appropriate hemodynamic parameters set for the mobilization session. Oxygen concentration should be adjusted to meet the increased metabolic demands of the patient during and immediately after treatment. Depending on the norms of a given ICU, the team may need to be advised of the need for adjustment of oxygen demands before, during and after physical therapy. Nonetheless, working closely with the team and keeping team members informed will serve the secondary goal of educating health care colleagues about the key role of physical therapy in the ICU.
Principles of progressive mobilization
Unlike exercise for the person who is generally healthy or has a stable chronic condition and may have no contraindications for exercise testing, mobilization for patients in the ICU is progressively titrated based on their moment-to-moment status and responses. This may be referred to as "response-dependent" treatment, wherein the patient data from physiologic measures are interpreted and immediately integrated into the clinical decision making process. This requires detailed continuous assessment and evaluation before, during and after (immediately and some time later) each mobilization session to ensure that the prescription had the intended effect, and minimal untoward effects. On-going assessment and evaluation provides essential feedback to the physical therapist regarding progressing the mobilization prescription, or down-regulating the prescription so that it is perfectly matched to the patient's status at any given time, or in some instances, discontinuing treatment. This is an essential iterative, carefully titrated process that ensures optimal benefit with least risk during each physical therapy session. Two levels of risk are associated with mobilization: 'overprescribing' in which the mobilization parameters are excessive for the patient's hemodynamic status, and 'underprescribing' such that the patient is exposed to the risk of autonomic (loss of pressure and fluid volume regulating mechanisms) and multisystem deconditioning. The physical therapist prescribes interventions that place demands on D[O.sub.2] that can be threatened or impaired to varying degrees. Because the status of patients in the ICU can change quickly, patients are monitored closely before, during and after treatment for safety reasons as well as evaluation of response to intervention. (5) Body position and mobilization occur along with structured monitoring to comprise a mobilization test.
A mobilization test may consist of subjecting a patient to some physical stressor and monitoring the patient's responses to the requisite body position perturbations and stress on D[O.sub.2]. (67-69) Alternatively, such a test may be conducted during the nurse's daily care. Details of the clinical decision making process that extend the principles described in this article, are described in the subsequent article by Perme and Chandrashekar in this special issue.
Reducing the Knowledge Translation Gap Vis a Vis Mobilization as a Primary Intervention for Patients in the ICU
The biomedical model advocates that interventions are directed at a specific underlying etiology or pathology. In the management of patients with complex conditions, this reductionistic approach can be overly simplistic. Patients in the ICU for example, have multiple problems, and each problem may have a range of contributing or mediating factors (as described earlier with respect to four categories of factors that threaten or impair oxygen transport). Furthermore, mobilization needs to be titrated to a patient's specific needs and specific responses. A stringent standardized mobilization protocol that is required for well controlled studies is not consistent with practice needs. Such a protocol even with clearly defined guidelines could be excessive or suboptimal to effect the requisite short- and long-term oxygen transport outcomes. Not surprisingly, the findings of such scientifically controlled studies related to physical therapy in acute care are often equivocal.
In my view, substantial evidence supports the benefits of mobilization and exercise to health and well being in all people including the ICU setting (rather, the question is, why would it not be), and that the absence of these is deleterious. Given that this evidence is unequivocal, the need to have patients upright and moving across clinical settings can now be assumed, and does not need to be established in the ICU setting. Furthermore, most experts in the field would concur given the strength of this knowledge, conducting the appropriate experimental control of having patients remain recumbent and inactive would be unethical.
The critical focus in ICU care needs to be understanding and implementing a sound clinical decision making process so that the mobilization prescription is maximally safe and therapeutic for a given patient with respect to oxygen transport. The end goals will be the return of the patient quickly to independent living with the fewest number of complications, and the least hospital stay and expense. In my view, without attention to response-driven physical therapy intervention of patients in the ICU, randomized controlled clinical trials will continue to provide equivocal findings because of their unrealistic standardization and single impairment focus. Even with such a focus, no two patients can be considered the 'same' even if they share a single impairment. Serial single case studies based on single subject research designs have greater justification and support as a means to elucidate the clinical decision making process for mobilizing patients in the ICU. One such report was published by Wong and colleagues. (70)
The role of the physical therapist in the ICU is to expedite the patient's recovery through initially optimizing oxygen transport and physiologic conditioning and function, and then return to living in the community. The three levels of assessment and evaluation based on the International Classification of Functioning, Disability and Health were reviewed, and advocated as a basis for selecting outcomes measures.
The evidence supporting mobilizing patients who are severely ill has been mounting over the past 60 years. As early as the 1940s, reports of patients who were recumbent and immobile deteriorating were made, along with reports of patients improving more quickly and having fewer complications when they were upright and moving. The mechanisms for these observations were not understood until later. Despite this knowledge, physical therapists need to exploit our current understanding of the physiology underlying the benefits of the upright position alone, and in conjunction with mobilization. A detailed understanding of the four factors threatening or impairing oxygen transport, can offer physical therapists a way to target their interventions including mobilization to offset these threats and address impairments of oxygen transport. Progressive movement leads to the capacity to function independently and resume life in the community. Given inactivity is a primary determinant of lifestyle conditions, i.e., heart disease, hypertension and stroke, cancer, diabetes and obesity, recommendations to the patient about assuming an active lifestyle along with abstinence of smoking and optimal nutrition are an essential component of the physical therapist's comprehensive and holistic care of each patient. For patients who are hemodynamically unstable, the physical therapist's role is to perform serial assessments, to monitor when the patient is ready to commence progressive mobilization within safe and therapeutic limits, as well as conduct less aggressive forms of intervention as indicated, e.g., body positioning.
Future studies on mobilizing patients who are critically ill need to be predicated on the fact that movement is essential to augment oxygen delivery and to condition the oxygen transport system. Mobilization is the means for addressing the oxygen transport system threats and dysfunction, as well as a basis for functional recovery, thereby, addressing all three levels of the International Classification of Functioning, Activity and Social Participation. A focus on the clinical decision making process for prescribing the parameters for mobilization provides the mechanism for directing and applying the stimulus safely and effectively. Single subject design research has greater justification over randomized controlled clinical trials as the latter will only continue to result in equivocal findings.
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Elizabeth Dean, PT, PhD
Elizabeth Dean, PT, PhD, is Professor, Department of Physical Therapy, Faculty of Medicine, University of British Columbia, Canada. Contact e-mail: firstname.lastname@example.org
Dr Dean's academic and clinical career and experiences have focused on oxygen transport as a basis for the diagnosis and management of primary and secondary oxygen transport dysfunction, increasingly within the context of the WHO International Classification of Functioning, Disability and Health. She has co-edited with Dr. D. Frownfelter and contributed multiple chapters to the 4th edition of 'Cardiovascular and Pulmonary Physical Therapy: Evidence and Practice' and is author with Donna of its accompanying Case Study Guide (2nd edition). Elizabeth is an author of numerous peer-reviewed articles and book chapters and has been invited to speak in over 25 countries. Her work has a global arm that extends to Africa, Asia and the Middle East. She was invited to serve as Senior of the Cardiovascular/Cardiorespiratory Team on the Kuwait Dalhousie Project in Kuwait for over a year, and was a Visiting Professor at the Hong Kong Polytechnic University in Hong Kong for one year. Recently, Elizabeth has been re-appointed as a non-resident Visiting Professor at Leeds Metropolitan University in the UK. In 2007, at the 15th International World Confederation of Physical Therapy Congress, she was the convener of 'The First Physical Therapy Summit on Global Health'.
Table 1. Four factors determining oxygen transport status and their levels Factor Level Pathology Acute Chronic Acute on chronic Recumbency and Distinct physiologic effects of each restricted mobility with respect to hemodynamic and cardiovascular/respiratory effects, as well as other systems (see Table 2) Extrinsic factors * Bed rest relate to the patient's care * Bed type and features to reposition the patient or move him or her readily * Lines and leads; catheters; chest tubes Intravenous, arterial lines, and feeding tubes * Limitations from respiratory support equipment, e.g., supplemental oxygen, invasive/noninvasive mechanical ventilation * Medications, e.g., anxiolytics, sedatives, neuromuscular blockers, blood thinners, opiates * Surgical factors, e,g., type, location, incisions, internal and external fixation devices, duration of surgery, type and duration of anesthesia Airway and mechanical ventilation Intrinsic factors * Age related to the patient course * Smoking history; environmental exposure over life * Nutritional status * Aerobic fitness and strength * Obesity * Blood sugar * Blood pressure * Fear and anxiety * Pre morbid stress levels * Secondary diagnoses that are not contributing directly to this hospital admission Source: Reference 9 Table 2. Physiological consequences of bed rest Fluid volume redistribution [down arrow] Plasma and blood volume [down arrow] Total heart and left ventricular volumes [up arrow] Hematocrit and hemoglobin Diuresis and natriuresis Venous stasis Neuromuscular inactivity [up arrow] Insulin resistance [down arrow] Muscle mass [down arrow] Muscle strength [down arrow] Muscle endurance [down arrow] Nerve conduction Altered distribution of body weight and pressure Urine stasis, retention, tendency toward calculus formation Hypercalciuria Bone demineralization Local skin changes and ulceration Aerobic deconditioning [up arrow] Heart rate at rest and at all levels of activity [down arrow] Resting and maximum stroke volume [down arrow] Maximum cardiac output [up arrow] Risk of venous thrombosis and thromboembolism [down arrow] Orthostatic tolerance [down arrow] Aerobic conditioning [down arrow] V[O.sub.2 max] [up arrow] Venous compliance Other Respiratory muscle weakness Limb weakness Myopathies Neuropathies Catabolism Anorexia Paralytic ileus Constipation [up arrow] Sensitivity to thermal stimuli; increased sweating and hyperemia [up arrow] Anxiety, hostility, depression, psychosis [up arrow] Auditory threshold [up arrow] Focal point, decreased near point of visual acuity Alteration in clearance of some drugs Altered circadian rhythm Potential contributor to a systemic inflammatory response Source: References 14-32 Table 3. Acute physiological effects of mobilization and exercise Pulmonary System [up arrow] Regional ventilation [up arrow] Regional perfusion [up arrow] Regional diffusion [up arrow] Zone 2 (i.e., area of ventilation perfusion matching) [up arrow] Tidal volume Alter breathing frequency [up arrow] Minute ventilation [up arrow] Efficiency of respiratory mechanics [down arrow] Airflow resistance [up arrow] Flow rates [up arrow] Strength and quality of a cough [up arrow] Mucociliary transport and airway clearance [up arrow] Distribution and function of pulmonary immune factors Potential facilitation of weaning from mechanical ventilation Cardiovascular System Hemodynamic effects [up arrow] Venous return [up arrow] Stroke volume [up arrow] Heart rate [up arrow] Myocardial contractility [up arrow] Stroke volume, heart rate and cardiac output [up arrow] Coronary perfusion [up arrow] Circulating blood volume [up arrow] Chest tube drainage Peripheral circulatory effects [down arrow] Peripheral vascular resistance [up arrow] Peripheral blood flow [up arrow] Peripheral tissue oxygen extraction Lymphatic System [up arrow] Pulmonary lymphatic flow [up arrow] Pulmonary lymphatic drainage Hematologic System [up arrow] Circulatory transit times [down arrow] Circulatory stasis Neurological System [up arrow] Arousal [up arrow] Cerebral electrical activity [up arrow] Stimulus to breathe [up arrow] Sympathetic stimulation [up arrow] Postural reflexes Neuromuscular System [up arrow] Regional blood flow [up arrow] Oxygen extraction Endocrine System [up arrow] Release, distribution, and degradation of catecholamines Genitourinary System [up arrow] Glomerular filtration [up arrow] Urinary output [down arrow] Renal stasis Gastrointestinal System [up arrow] Gut motility [down arrow] Constipation Integumentary System [up arrow] Cutaneous circulation for thermoregulation Other Multisystem Effects [down arrow] Effects of anesthesia and sedation [down arrow] Deleterious cardiopulmonary effects of surgery [down arrow] Risk of loss of gravitational stimulus in conjunction with the upright position Source: References 62-66 Table 4. Comparison of mobilization prescription for patients in the ICU to exercise prescription for the generally well person or individual with a stable chronic condition Exercise Parameter Mobilization Type Active limb movements in lying (assisted and unassisted; with and without resistance) and in upright (supported and self-supporting) Ergometer pedaling in bed Sitting over the edge of the bed (with and without support) Standing (with or without support Stepping in place (with or without support Transfer to chair (with support or stand by assistance) Limb and trunk exercises in bedside chair Ergometer pedaling in chair Walking with assistance or unassisted with or without a walking aid Intensity Within a specific heart rate, BP, SpO2, (absence of aberrant ECG), and exertion; based on assessment findings, medical consultation, and mobilization test Duration As tolerated, i.e., responses remain within the limits specified by safety and therapeutic goals Frequency Typically, the shorter the duration of tolerable mobilization, the more frequent the sessions As the duration of the sessions increases, the frequency of sessions can be decreased, e.g., 3 sessions of 10 to 15 min daily, may become, 1 session of 30 minutes Course Goal: walking before discharge to ward or home; and basic strength to perform basic ADL Exercise Parameter Exercise Type Aerobic exercise: walking and cycling Strengthening exercise: Peripheral limb muscles Trunk muscles (core stability) Flexibility exercise: General flexibility and range of motion of all major peripheral and spinal joints and muscles Intensity Aerobic exercise: Prescribed at some proportion of maximal performance identified from an exercise test Strengthening exercise: Prescribed at a proportion of repetition maximum for each muscle group; 3 repetitions of 8-10 Duration Aerobic exercise: 20 to 40 min Strengthening exercise: N/A (dependent on the intensity and repetitions) Frequency Aerobic exercise: 3-5x/week Strengthening exercise: 2 to 3x/week Course 6 to 8 weeks for adaptation to occur; less if the individual is particularly deconditioned Person re-tested so prescription can be revised