From the Guidelines
The Intubation Difficulty Scale (IDS) is the most appropriate scoring system to assess the difficulty of endotracheal intubation, as it provides an objective and quantitative evaluation of the procedure's complexity. When evaluating the difficulty of intubation, it is essential to consider the various factors that can contribute to a complicated procedure, including peri-procedural complications and technical difficulty [ 1 ]. The IDS takes into account seven parameters, including the number of attempts, number of operators, number of alternative techniques, Cormack-Lehane grade, lifting force required, laryngeal pressure needed, and vocal cord mobility, to provide a comprehensive assessment of the intubation procedure [ 1 ]. Some of the key factors that can increase the difficulty of intubation include:
- Obesity and pregnancy, which can decrease functional residual capacity (FRC) and increase the risk of atelectasis [ 1 ]
- Acute respiratory failure or cardiovascular failure before intubation [ 1 ]
- Difficulty in intubation, which can be predicted using the MACOCHA score, a predictive score that assesses risk factors such as Mallampati score, obstructive sleep apnoea syndrome, reduced mobility of cervical spine, and limited mouth opening [ 1 ] The IDS should be calculated immediately after intubation to accurately document the procedure's complexity and to identify patients who may need special airway management in the future [ 1 ]. By using the IDS consistently, clinicians can communicate objectively about intubation challenges, identify patients at risk for difficult airways, and improve patient safety by standardizing documentation of airway management difficulties [ 1 ].
From the Research
Intubation Difficulty Score
The Intubation Difficulty Score (IDS) is a measure used to assess the difficulty of intubation, with higher scores indicating greater difficulty. Several studies have investigated the factors that contribute to difficult intubation and the predictive value of various airway assessment factors.
Predictive Factors
- Pathological conditions associated with difficult intubation, such as malformation of the face, acromegaly, and cervical rheumatism 2
- Mouth opening less than 3.5 cm 2
- Ratio of patient's height to thyromental distance ≥ 25 2
- Head and neck movement less than 80 degrees 2
- Mallampati class III or IV 2, 3, 4
- Thyromental distance ≤ 6cm 3
- Neck extension < 5cm 3
- Body mass index (BMI) ≥ 25 kg/m(2) 4
- Upper lip bite test (ULBT) class III 4
Assessment Tools
- Intubation Difficulty Scale (IDS) 2, 3, 4
- Modified Mallampati test 3, 4
- Thyromental distance test 3
- Neck extension test 3
- Upper lip bite test (ULBT) 4
Management of Difficult Intubation
- Anticipated difficult intubation: awake fibreoptic intubation is often the technique of choice 5
- Unforeseen difficult intubation: various techniques for control of the airway, such as videolaryngoscopy or fibreoptic bronchoscopy, may be used 6, 5
- Impossible tracheal intubation and lung ventilation: use of the laryngeal mask airway, Combitube, or transtracheal ventilation may be necessary 5