CVR Physiotherapy › Technique cards › ICU and ventilation
Effects of bed rest and immobilisation, and early mobilisation
Bed rest was asked five times: as 3 marks (one effect on three systems, S19 and W21) and as 7 marks (complications of bed immobility in ICU, W17; complications on different systems, S24; effects on the cardiovascular and pulmonary systems, S26). Learn it system by system, with the mechanism and the prevention for each.
- Syllabus
- Ch 3(d) Complications of bed rest and immobilisation, and prevention
- Priority
- High yield. In 5 of 20 papers (2016–2026), 3 of them as 7 marks.
- Asked as
- 7m W17S24S26 3m S19W21
- Usual split
- 3-mark list (one effect per system); 7-mark system-wise effects with prevention
- Checked against
- Dallas bed rest study (1968); muscle wasting in critical illness (2013); ICU-acquired weakness definition (2002); early mobilisation trials. Full list under Sources.
- Content checked
- 19 October 2026. Next review due October 2027.
- My revision
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1Why bed rest harms
The body adapts to the load it carries. Lying flat removes two loads at once: gravity along the body (which keeps blood-pressure reflexes and fluid balance trained) and muscle work against gravity (which keeps muscle, bone and fitness). Within days every system starts to lose what it does not use. Older and critically ill patients lose it fastest.
3 weeks: fitness down about a quarter
In the Dallas bed rest study (1968), 3 weeks of bed rest cut young men's maximal oxygen uptake by about 27%. In critically ill patients the thigh muscle (rectus femoris) shrank by about 12.5% in the first week (Puthucheary, 2013).
2Cardiovascular and pulmonary effects (7 marks in S26)
| Effect | Mechanism | Prevention |
|---|---|---|
| Higher resting heart rate, smaller stroke volume | Blood volume falls and the heart is less filled; the heart adapts to less work | Sit out and stand early; active exercise |
| Orthostatic (postural) hypotension | Lying flat shifts fluid to the chest; the body passes more urine and plasma volume falls; blood-pressure reflexes are not used | Sit up in stages; dangle legs; tilt table; ankle pumps before standing; compression stockings as prescribed |
| Lower aerobic fitness (VO₂max) | Smaller stroke volume and cardiac output; muscles lose capillaries and mitochondria | Bed cycling, walking, graded endurance exercise |
| Deep vein thrombosis and pulmonary embolism | Stasis (no calf pump), plus a sticky blood state after illness or surgery | Ankle pumps 10 every hour, early walking, compression devices, anticoagulants as prescribed |
| Lower lung volumes, collapse at the bases | Abdominal contents push the diaphragm up when lying flat; shallow breathing; small airways close | Upright positions, deep breathing with a hold, turning, walking |
| Retained secretions and pneumonia | Secretions pool in dependent areas; weaker cough; slower mucus clearance; aspiration when flat | Turn 2–4-hourly, head up 30–45°, airway clearance, huffing and coughing |
| Weaker breathing muscles | Disuse; on a ventilator the diaphragm itself wastes | Spontaneous breathing as soon as possible; inspiratory muscle training |
3Effects on other systems (S24; W17 in ICU)
| System | Effects | Prevention |
|---|---|---|
| Muscles | Wasting and weakness, mostly in antigravity muscles (quadriceps, glutes, calf, back); lower endurance. A classic estimate is a strength loss of about 1–1.5% a day of strict bed rest; critical illness is faster | Active and resisted exercise, functional activity, electrical muscle stimulation in sedated patients |
| Joints and soft tissue | Contractures (ankle plantarflexion, hip and knee flexion, shoulder), stiffness | Daily ROM, positioning, splints |
| Bone | Bone loss (calcium leaves bone within days), raised calcium in urine | Weight-bearing (standing, tilt table) as early as possible |
| Skin | Pressure injuries over the sacrum, heels, hips and back of the head, within hours in high-risk patients | Turning schedule, pressure-relieving mattress, skin checks, nutrition |
| Metabolic and endocrine | Insulin resistance, protein loss (negative nitrogen balance), lower metabolic rate | Exercise; nutrition support |
| Kidney and bladder | Urinary stasis, infection and stones (with high urine calcium); retention | Upright positions, fluids, early toileting |
| Gut | Constipation, poor appetite, reflux | Mobility, fluids, fibre, sitting up for meals |
| Nervous system and mind | Poor balance and coordination; delirium and confusion; low mood, anxiety; poor sleep; sensory deprivation | Day–night routine, orientation, family visits, sitting out, early walking |
ICU-acquired weakness (W17: complications of bed immobility in ICU)
Generalised, symmetrical limb weakness that develops during critical illness with no other cause. Diagnosed at the bedside with the MRC sum score (6 muscle groups each side, 0–5 each, total 60): below 48 = ICU-acquired weakness. Risk factors: sepsis, multi-organ failure, long ventilation, immobility, high blood sugar, steroids and paralysing drugs. It slows weaning and can affect walking and work for months, so prevention by early mobilisation matters.
4Prevention: early mobilisation
- Assess safety first (see the ICU safety criteria).
- Positioning: turns every 2–4 hours, head up, upright sitting in bed.
- Range of motion: passive when sedated, then active-assisted and active.
- In-bed exercise: bed cycling, bridging, resisted limb exercise.
- Sitting over the edge of the bed, then standing (tilt table if BP falls or the patient is weak).
- Transfer to a chair; marching on the spot; walking, with the ventilator if needed.
- Breathing: deep breathing, airway clearance, inspiratory muscle training.
- Monitor before, during and after: HR, BP, SpO₂, respiratory rate, symptoms.
Classic answer vs current evidence: rest after illness
Classic
Strict bed rest for days or weeks after a heart attack, surgery or serious illness.
Current
Bed rest is a treatment with side effects, used only when needed and for as short a time as possible. Early mobilisation is safe within criteria and shortens delirium and recovery; the amount is matched to the patient.
Write in the exam
"Bed rest affects every system within days; prevention is early, graded mobilisation with positioning, breathing exercises and ROM."
5Exam corner
Past questions (MUHS, 2016–2026)
- 7-mark questionsComplications of bed immobility in an ICU patient (W17). Complications of bed rest on different physiological systems (S24). Adverse effects of bed rest on the cardiovascular and pulmonary systems (S26).
- 3-mark questionsOne effect of bed rest on any three systems (S19). Effects of long-term bed rest on any three systems (W21).
Heart, lungs, legs
Heart: postural hypotension. Lungs: basal collapse and pneumonia. Legs: muscle wasting and DVT. Add skin (pressure sores) or bone (osteoporosis) if asked for more.
Answer skeleton: 7 marks
- [1] One-line principle: unloading and lying flat cause every system to adapt downwards within days.
- [4] Table: system, effect, mechanism (cardiovascular and pulmonary in detail for S26).
- [2] Prevention: positioning, breathing exercises, ROM, early graded mobilisation, DVT and pressure care.
Test yourself
3 mWhy does a patient feel faint when first sat up after 10 days in bed?
Plasma volume has fallen (fluid shifts to the chest when lying flat and is passed as urine), the heart is less filled, and blood-pressure reflexes are out of practice. On sitting, blood pools in the legs and BP falls: postural hypotension. Sit up in stages, use ankle pumps and a tilt table.
MCQThe MRC sum score that defines ICU-acquired weakness is:A. Below 60B. Below 48C. Below 30D. Below 12
B. Below 48 out of 60.
Sources
- MUHS BPTh syllabus (2012) and MUHS IV BPTh question papers 2016–2026 (muhsonline.com, unofficial archive; Dhole Patil College of Physiotherapy past-paper page).
- Saltin B, et al. Response to exercise after bed rest and after training (Dallas Bed Rest and Training Study). Circulation 1968;38(5 Suppl):VII1–78.
- Puthucheary ZA, et al. Acute skeletal muscle wasting in critical illness. JAMA 2013;310:1591–600.
- De Jonghe B, et al. Paresis acquired in the intensive care unit: a prospective multicenter study. JAMA 2002;288:2859–67.
- Dittmer DK, Teasell R. Complications of immobilization and bed rest. Can Fam Physician 1993;39:1428–37.
- Structure and classical content: Frownfelter & Dean (2022); Hough, Physiotherapy in Respiratory and Cardiac Care; Kisner & Colby, Therapeutic Exercise.
Educational notes for exam preparation. Not medical advice.
Version 1. Content checked 19 October 2026. Next review October 2027.