Intubation; Difficult
Conditions
Keywords
BMI < 50 kg/m2, Mallampatti class: III-IV, Reduced mouth opening < 4 cm, Neck circumference > 40 cm for females and > 43 cm for males, Thyromental distance < 6 cm, Ratio of the patient's height to thyromental distance ≥ 23.5, Sternomental distance < 12 cm
Brief summary
This study was designed to determine the first attempt success rate of tracheal intubation with the McGRATH™ MAC laryngoscope using direct visualization in patients with known difficult airways, as well as exploring the possibility of identifying a particular direct Cormack-Lehane (C-L) grade view where indirect (video) visualization can be most beneficial during laryngoscopy and intubation.
Interventions
DEVICEMcGrath MAC enhanced direct laryngoscope
The McGRATH® MAC enhanced direct laryngoscope (EDL) combines the familiarity of direct laryngoscopy with an inline video camera for an enhanced view. All 100 patients will be intubated using the McGRATH® MAC video laryngoscope, either through direct or indirect vision laryngoscopy. The LCD monitor of the McGRATH™ MAC was initially covered; if the anesthesiologist visualized a modified C-L grade 1-3 view, the patient was intubated utilizing this direct view. If the anesthesiologist observed a modified C-L grade 4 view during their initial direct view, the patient was intubated using the indirect method. If intubation via direct laryngoscopy was unsuccessful on the first attempt, the patient was intubated using the indirect view. If both methods of laryngoscopy were unsuccessful, the rescue intubation technique was performed at the discretion of the anesthesiologist.
Sponsors
Medtronic - MITG
The University of Texas Health Science Center, Houston
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
SUPPORTIVE_CARE
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
* BMI \< 50 kg/m2 * Two or more of the following inclusion criteria: Mallampati class: III-IV; Reduced mouth opening \< 4 cm; Neck circumference \> 40 cm for females and \> 43 cm for males; Thyromental distance \< 6 cm; Ratio of the patient's height to thyromental distance ≥ 23.5; Sternomental distance \< 12 cm
Exclusion criteria
* BMI ≥ 50 kg/m2 * emergency status * cervical injury or pathology * neck irradiation * known difficult airway * risk of gastric aspiration * hemodynamic instability * requiring rapid sequence intubation
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Number of Participants Successfully Intubated on First Attempt With Use of Either a Direct or Indirect Laryngoscopic View | after successful endotracheal tube placement | All 100 patients will be intubated using the McGRATH® MAC video laryngoscope, either through direct or indirect vision laryngoscopy. The LCD monitor of the McGRATH™ MAC was initially covered; if the anesthesiologist visualized a modified C-L grade 1-3 view, the patient was intubated utilizing this direct view. If the anesthesiologist observed a modified C-L grade 4 view during their initial direct view, the patient was intubated using the indirect method. If intubation via direct laryngoscopy was unsuccessful on the first attempt, the patient was intubated using the indirect view. If both methods of laryngoscopy were unsuccessful, the rescue intubation technique was performed at the discretion of the anesthesiologist. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Glottic View With Indirect Laryngoscopy | at the time of laryngoscopy | Glottic view as described by Cormack and Lehane (Samsoon GL, Young JR. Difficult tracheal intubation: A retrospective study. Anesthesia 1987; 42:487), scored as follows- Grade 1. Full view of glottis Grade 2a. Partial view of glottis Grade 2b. Arytenoids or posterior portion of cords just visible Grade 3. Only the epiglottis visible Grade 4. Neither epiglottis nor glottis visible |
| Time for Direct View Laryngoscopy During the First Attempt | at the time of laryngoscopy | Time from mouth opening to best direct laryngoscopic view |
| Time for Indirect View Laryngoscopy During the First Attempt | at the time of laryngoscopy | Time from mouth opening to best indirect laryngoscopic view |
| Time for Intubation | at the time of laryngoscopy | Time for laryngoscopy (either direct or indirect) plus the time for endotracheal tube (ETT) cuff to pass vocal cords. |
| Glottic View With Direct Laryngoscopy | at the time of laryngoscopy | Glottic view as described by Cormack and Lehane, scored as follows- Grade 1. Full view of glottis Grade 2a. Partial view of glottis Grade 2b. Arytenoids or posterior portion of cords just visible Grade 3. Only the epiglottis visible Grade 4. Neither epiglottis nor glottis visible |
| Number of Participants Who Received External Laryngeal Manipulation During the First Attempt | at the time of intubation | — |
| Number of Participants on Whom Bougie (Introducer) Was Used to Facilitate Intubation on the First Attempt | at the time of intubation | — |
| Subjective Ease of Laryngoscopy | at the time of laryngoscopy | The anesthesiologists rated the McGRATH™ MAC's ability in managing airways as very easy, easy, slight resistance, difficult, or not possible. The difficulty of laryngoscopy was evaluated during the insertion and placement of the McGRATH™ MAC, from the patient's lips, into their oropharynx, until a glottic view was obtained. |
| Subjective Ease of Intubation | at the time of laryngoscopy | The anesthesiologists rated the McGRATH™ MAC's ability in managing airways as very easy, easy, slight resistance, difficult, or not possible. The difficulty of endotracheal tube (ETT) delivery (that is, intubation) was evaluated during the insertion of the ETT into the patient's mouth, until the ETT passed the vocal cords. |
| Number of Intubation Attempts | at the time of intubation | — |
Countries
United States
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| McGrath Mac Intubations All 100 patients will be intubated using the McGRATH® MAC video laryngoscope, either through direct or indirect vision laryngoscopy. The LCD monitor of the McGRATH™ MAC was initially covered; if the anesthesiologist visualized a modified C-L grade 1-3 view, the patient was intubated utilizing this direct view. If the anesthesiologist observed a modified C-L grade 4 view during their initial direct view, the patient was intubated using the indirect method. If intubation via direct laryngoscopy was unsuccessful on the first attempt, the patient was intubated using the indirect view. If both methods of laryngoscopy were unsuccessful, the rescue intubation technique was performed at the discretion of the anesthesiologist. | 100 |
| Total | 100 |
Baseline characteristics
| Characteristic | McGrath Mac Intubations |
|---|---|
| Age, Continuous | 53.17 years STANDARD_DEVIATION 14.7 |
| Sex: Female, Male Female | 40 Participants |
| Sex: Female, Male Male | 60 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | — / — |
| other Total, other adverse events | 48 / 94 |
| serious Total, serious adverse events | 0 / 100 |
Outcome results
Primary
Number of Participants Successfully Intubated on First Attempt With Use of Either a Direct or Indirect Laryngoscopic View
All 100 patients will be intubated using the McGRATH® MAC video laryngoscope, either through direct or indirect vision laryngoscopy. The LCD monitor of the McGRATH™ MAC was initially covered; if the anesthesiologist visualized a modified C-L grade 1-3 view, the patient was intubated utilizing this direct view. If the anesthesiologist observed a modified C-L grade 4 view during their initial direct view, the patient was intubated using the indirect method. If intubation via direct laryngoscopy was unsuccessful on the first attempt, the patient was intubated using the indirect view. If both methods of laryngoscopy were unsuccessful, the rescue intubation technique was performed at the discretion of the anesthesiologist.
Time frame: after successful endotracheal tube placement
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Group | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Number of Participants Successfully Intubated on First Attempt With Use of Either a Direct or Indirect Laryngoscopic View | direct laryngoscopic view | 72 Participants |
| McGrath Mac Intubations | Number of Participants Successfully Intubated on First Attempt With Use of Either a Direct or Indirect Laryngoscopic View | indirect laryngoscopic view | 16 Participants |
Secondary
Glottic View With Direct Laryngoscopy
Glottic view as described by Cormack and Lehane, scored as follows- Grade 1. Full view of glottis Grade 2a. Partial view of glottis Grade 2b. Arytenoids or posterior portion of cords just visible Grade 3. Only the epiglottis visible Grade 4. Neither epiglottis nor glottis visible
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Category | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Glottic View With Direct Laryngoscopy | Grade 1 view | 11 Participants |
| McGrath Mac Intubations | Glottic View With Direct Laryngoscopy | Grade 2a view | 18 Participants |
| McGrath Mac Intubations | Glottic View With Direct Laryngoscopy | Grade 2b view | 27 Participants |
| McGrath Mac Intubations | Glottic View With Direct Laryngoscopy | Grade 3 view | 21 Participants |
| McGrath Mac Intubations | Glottic View With Direct Laryngoscopy | Grade 4 view | 17 Participants |
Secondary
Glottic View With Indirect Laryngoscopy
Glottic view as described by Cormack and Lehane (Samsoon GL, Young JR. Difficult tracheal intubation: A retrospective study. Anesthesia 1987; 42:487), scored as follows- Grade 1. Full view of glottis Grade 2a. Partial view of glottis Grade 2b. Arytenoids or posterior portion of cords just visible Grade 3. Only the epiglottis visible Grade 4. Neither epiglottis nor glottis visible
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Category | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Glottic View With Indirect Laryngoscopy | Grade 1 view | 51 Participants |
| McGrath Mac Intubations | Glottic View With Indirect Laryngoscopy | Grade 2b view | 17 Participants |
| McGrath Mac Intubations | Glottic View With Indirect Laryngoscopy | Grade 2a view | 16 Participants |
| McGrath Mac Intubations | Glottic View With Indirect Laryngoscopy | Grade 3 view | 6 Participants |
| McGrath Mac Intubations | Glottic View With Indirect Laryngoscopy | Grade 4 view | 4 Participants |
Secondary
Number of Intubation Attempts
Time frame: at the time of intubation
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Category | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Number of Intubation Attempts | 1 attempt | 88 Participants |
| McGrath Mac Intubations | Number of Intubation Attempts | 2 attempts | 5 Participants |
| McGrath Mac Intubations | Number of Intubation Attempts | 3 attempts | 1 Participants |
Secondary
Number of Participants on Whom Bougie (Introducer) Was Used to Facilitate Intubation on the First Attempt
Time frame: at the time of intubation
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|
| McGrath Mac Intubations | Number of Participants on Whom Bougie (Introducer) Was Used to Facilitate Intubation on the First Attempt | 12 Participants |
Secondary
Number of Participants Who Received External Laryngeal Manipulation During the First Attempt
Time frame: at the time of intubation
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|
| McGrath Mac Intubations | Number of Participants Who Received External Laryngeal Manipulation During the First Attempt | 42 Participants |
Secondary
Subjective Ease of Intubation
The anesthesiologists rated the McGRATH™ MAC's ability in managing airways as very easy, easy, slight resistance, difficult, or not possible. The difficulty of endotracheal tube (ETT) delivery (that is, intubation) was evaluated during the insertion of the ETT into the patient's mouth, until the ETT passed the vocal cords.
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Category | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Subjective Ease of Intubation | very easy | 20 Participants |
| McGrath Mac Intubations | Subjective Ease of Intubation | easy | 39 Participants |
| McGrath Mac Intubations | Subjective Ease of Intubation | slight resistance | 21 Participants |
| McGrath Mac Intubations | Subjective Ease of Intubation | difficult | 13 Participants |
| McGrath Mac Intubations | Subjective Ease of Intubation | not possible | 1 Participants |
Secondary
Subjective Ease of Laryngoscopy
The anesthesiologists rated the McGRATH™ MAC's ability in managing airways as very easy, easy, slight resistance, difficult, or not possible. The difficulty of laryngoscopy was evaluated during the insertion and placement of the McGRATH™ MAC, from the patient's lips, into their oropharynx, until a glottic view was obtained.
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Category | Value (COUNT_OF_PARTICIPANTS) |
|---|---|---|---|
| McGrath Mac Intubations | Subjective Ease of Laryngoscopy | very easy | 22 Participants |
| McGrath Mac Intubations | Subjective Ease of Laryngoscopy | easy | 29 Participants |
| McGrath Mac Intubations | Subjective Ease of Laryngoscopy | slight resistance | 23 Participants |
| McGrath Mac Intubations | Subjective Ease of Laryngoscopy | difficult | 19 Participants |
| McGrath Mac Intubations | Subjective Ease of Laryngoscopy | not possible | 1 Participants |
Secondary
Time for Direct View Laryngoscopy During the First Attempt
Time from mouth opening to best direct laryngoscopic view
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis, as describe in Outcome Measure 1's Analysis Population Description. 78 of the 94 analyzed had direct laryngoscopy, and thus 78 are analyzed in this outcome measure.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| McGrath Mac Intubations | Time for Direct View Laryngoscopy During the First Attempt | 12.41 seconds | Standard Deviation 7.13 |
Secondary
Time for Indirect View Laryngoscopy During the First Attempt
Time from mouth opening to best indirect laryngoscopic view
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis, as describe in Outcome Measure 1's Analysis Population Description. 16 of the 94 analyzed had direct laryngoscopy, and thus 16 are analyzed in this outcome measure.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| McGrath Mac Intubations | Time for Indirect View Laryngoscopy During the First Attempt | 14.73 seconds | Standard Deviation 9.99 |
Secondary
Time for Intubation
Time for laryngoscopy (either direct or indirect) plus the time for endotracheal tube (ETT) cuff to pass vocal cords.
Time frame: at the time of laryngoscopy
Population: Of the 100 patients recruited, 6 patients were excluded from data analysis. 4 patients were found to not meet inclusion criteria. One patient with glottic view grade 3 was erroneously intubated via the indirect method. For another patient, the anesthesiologist aborted the protocol due to encountered difficulties.
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| McGrath Mac Intubations | Time for Intubation | 35.91 seconds | Standard Deviation 22.66 |