CIP and CIM : Failure to Wean and Increase Risk Reintubation

CIP, CIM & extubation failure – at a glance

1. Does critical‑illness polyneuropathy (CIP) make it hard for patients with secretions to stay off the ventilator?

Yes. CIP – and its sibling critical‑illness myopathy (CIM) – weaken the diaphragm, expiratory muscles and bulbar/pharyngeal musculature. Patients do not produce more secretions, but they lose the cough strength and airway‑protective reflexes required to clear them. Retained mucus  →  atelectasis  →  increased work of breathing  →  fatigue  →  re‑intubation.

Table 1. Mechanisms by which CIP/CIM promote ventilator dependence

Primary deficit	Clinical consequence	Impact on extubation
Loss of expiratory muscle power	Peak cough flow often <60 L·min‑1	Inability to expel pooled secretions → clogging of larger airways
Diaphragmatic & phrenic‑nerve dysfunction	↓ Inspiratory capacity; ↑ WOB	Even a modest secretion load tips the balance into fatigue & hypercapnia
Bulbar / pharyngeal weakness	Blunted swallow & glottic closure; silent aspiration	Further secretion burden & atelectasis after extubation
Global limb weakness (MRC <48)	Correlates closely with ineffective cough	2‑ to 3‑fold increase in re‑intubation risk

Practical bedside rule: If peak cough flow <60 L·min^‑1 or MRC sum <48 at planned extubation, treat as high‑risk: clear secretions, augment cough (e.g., mechanical insufflation–exsufflation), bridge with HFNC ± NIV.

2. How are CIP and CIM treated in the meantime?

No single drug reverses CIP/CIM. Management bundles target (1) preventable drivers, (2) early mobilisation & muscle‑specific therapies, (3) optimum nutrition, (4) respiratory support during recovery.

2.1 Modifiable drivers

Table 2. Stop or minimise the insults

Driver	Bedside action	Evidence highlight
Sepsis / systemic inflammation	Source control, early ABx	Strongest CIP risk factor
Hyperglycaemia	Target 110‑180 mg/dL (6‑10 mmol/L)	Tight but safe control ↓ ICU‑AW ≈40 %
Deep sedation & NMBAs	Daily sedation breaks; keep NMBA <48 h	Independent predictors of CIP/CIM
High corticosteroid dose	Use lowest effective course	Dose‑response link to CIM

2.2 Early mobilisation & muscle‑specific therapies

Table 3. Mobilise & stimulate

Strategy	Practical application	2023‑25 evidence
Passive → active physiotherapy	Begin <48 h after haemodynamic stability	Earlier = less ICU‑AW, faster discharge
Neuromuscular electrical stimulation (NMES)	30‑60 min/day on quads & diaphragm	Meta‑analysis: ↑ MRC, ↓ MV duration ≈1.7 d
Inspiratory‑muscle training (IMT)	30 breaths BID at 30‑50 % PImax	2024 RCTs: ↓ re‑intubation, faster weaning

2.3 Nutrition & metabolism

Target 1.3‑2.0 g protein·kg^‑1·day^‑1, start enteral feeds within 24‑48 h, avoid early full PN.

2.4 Respiratory support bundle

• Secretion‑clearance: scheduled suction, mucolytics, cough‑assist.
• Extubate when cough ≥60 L·min^‑1; bridge with HFNC/NIV.
• Early tracheostomy (≥10‑14 d failed weaning) for severe weakness.

3. How is the diagnosis made with EMG & nerve‑conduction studies (NCS)?

Electrophysiology separates neuropathy (CIP) from myopathy (CIM). The stepwise algorithm below is widely used.

Table 4. Signature electrophysiologic patterns

Parameter	CIP	CIM
Motor CMAP amplitude	↓ (<80 % LLN)	↓ (<80 % LLN)
Sensory SNAP amplitude	↓	Normal
CMAP duration	Normal	Prolonged (>10 ms)
Direct‑muscle stimulation (DMS)	Preserved excitability	Reduced excitability
Nerve : muscle CMAP ratio	> 0.5	< 0.5
Typical conclusion	Diffuse axonal sensorimotor neuropathy	Primary myopathy

Low sensory amplitudes + preserved direct‑muscle response → CIP; Normal sensory amplitudes + muscle inexcitability → CIM.

4. How do I calculate the Medical Research Council (MRC) sum score?

Score six muscle groups (bilaterally), grade 0–5, then add the 12 numbers (max 60).

Table 5. MRC Sum‑Score worksheet

Limb	Muscle group	Grade R	Grade L
Upper	Shoulder abduction (deltoid)
	Elbow flexion (biceps)
	Wrist extension (ext. carpi)
Lower	Hip flexion (iliopsoas)
	Knee extension (quadriceps)
	Ankle dorsiflexion (tibialis ant.)
Subtotal each side
MRC sum score = R + L (max 60)

Table 6. MRC grading scale

Grade	Description
0	No visible/palpable contraction
1	Flicker/trace contraction, no movement
2	Active movement with gravity eliminated
3	Active movement against gravity
4	Active movement against gravity + resistance
5	Normal power

Interpretation: Sum < 48 = ICU‑AW likely; Sum < 36 = severe weakness → high risk of extubation failure & prolonged rehab.

Bottom line: CIP/CIM + heavy secretions = weak cough → retained mucus → atelectasis → fatigue → re‑intubation. Mitigate drivers early, mobilise daily, augment cough, and choose the right airway strategy.