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The accuracy of locating the cricothyroid membrane by palpation - an intergender study.

Campbell M, Shanahan H, Ash S, Royds J, Husarova V, McCaul C - BMC Anesthesiol (2014)

Bottom Line: Incorrect identification of the CTM was more common in females (29/36 vs. 11/36, P < 0.001) and the distance from the CTM in the vertical plane was greater (11.0 [6.5-20.0] vs. 0.0 [0.0-10.0] mm, P < 0.001).CTM localisation is more difficult in female subjects irrespective of body habitus.It may be prudent to localize this structure by additional means (e.g. ultrasound) in advance of any airway manoeuvres or to modify the cricothyrotomy technique in the event that it is necessary in an emergency.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesia, The Rotunda Hospital, Parnell Square, Dublin 1, Ireland.

ABSTRACT

Background: The cricothyroid membrane (CTM) is the recommended site of access to the airway during cricothyrotomy to provide emergency oxygenation. We sought to compare the ability of physicians to correctly identify the CTM in male and female patients.

Methods: In a prospective observational study, anaesthetists were asked to locate the CTM by palpation which was then identified using ultrasound and the distance between the actual and estimated margin of the CTM was measured. Participants assessed the ease of CTM palpation using a visual analog scale. In a second series, the angulation of the posterior junction of the thyroid laminae was measured using ultrasound.

Results: 23 anaesthetists and 44 subjects participated. A total of 36 assessments were carried out in each gender. Incorrect identification of the CTM was more common in females (29/36 vs. 11/36, P < 0.001) and the distance from the CTM in the vertical plane was greater (11.0 [6.5-20.0] vs. 0.0 [0.0-10.0] mm, P < 0.001). In females distance from the CTM correlated positively with neck circumference (P = 0.005) and BMI (P = 0.00005) and negatively with subject height (P = 0.01). Posterior thyroid cartilage angulation was greater in females (118.6 ± 9.4° vs. 95.9 ± 12.9°, P = 0.02) and was lower in patients with correctly identified CTMs (100.0 ± 14.9° vs. 115.6 ± 15.9°, P = 0.02). VRS palpation correlated with decreased posterior thyroid cartilage angulation (P = 0.04).

Conclusions: CTM localisation is more difficult in female subjects irrespective of body habitus. It may be prudent to localize this structure by additional means (e.g. ultrasound) in advance of any airway manoeuvres or to modify the cricothyrotomy technique in the event that it is necessary in an emergency.

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Image of thyroid cartilage using ultrasound in the transverse plane. The subject in panel A is male and is panel B is female.
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Fig4: Image of thyroid cartilage using ultrasound in the transverse plane. The subject in panel A is male and is panel B is female.

Mentions: It is intuitive that the largyngeal structures of males are more prominent than females (Figure 4). The existing literature on the subject is largely based on cadaveric dissection and goniometric measurement. Ajmani dissected the laryngeal cartilages of 28 male and 12 female adult Nigerian cadavers and found that the length, transverse diameter and anteroposterior dimensions of the larynx and the transverse and anteroposterior diameter of the cricoid cartilage were greater in male specimens [16]. Ajmani additionally demonstrated that the degree of angulation at the junction of the right and left thyroid cartilages in the midline anteriorly was 89 degrees in males and 106 degrees in females. The standard deviation of 28.3 degrees and the range of the thyroid cartilage angle in males (60 to 106 degrees) and females (88 – 132 degrees) in that series suggests that considerable anatomical variation and overlap exists in the structure within a normal population [16]. The angles observed in our study were 95.6° for males and 118.6° for females is consistent with the figures of 90° and 120° reported in cadaveric dissection of European subjects [17, 18]. Eckel reported thyroid angles in German subjects of 70.25° in males and 88.39° in females similar to that of a Swedish population [12, 19]. Angles of 85.25° and 97.85° were reported by Jain in Indian males and females respectively [20]. While confirming the intergender difference that we have demonstrated using ultrasound, these interethnic variations may have implications for accurate localization of the CTM in these populations. A further potential anatomic difference between genders that may lend itself to easier localization of the CTM in males is the consistently greater size of the adjacent cartilaginous structures which is supported by numerous cadaveric dissection studies [12, 16, 20–23].Both the vertical height and width of the CTM itself are greater in males which present a clinician with a larger target to locate [24]. Similar studies have also identified age related changes which may also have implications for locating these structures in younger subjects [25].Figure 4


The accuracy of locating the cricothyroid membrane by palpation - an intergender study.

Campbell M, Shanahan H, Ash S, Royds J, Husarova V, McCaul C - BMC Anesthesiol (2014)

Image of thyroid cartilage using ultrasound in the transverse plane. The subject in panel A is male and is panel B is female.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4384292&req=5

Fig4: Image of thyroid cartilage using ultrasound in the transverse plane. The subject in panel A is male and is panel B is female.
Mentions: It is intuitive that the largyngeal structures of males are more prominent than females (Figure 4). The existing literature on the subject is largely based on cadaveric dissection and goniometric measurement. Ajmani dissected the laryngeal cartilages of 28 male and 12 female adult Nigerian cadavers and found that the length, transverse diameter and anteroposterior dimensions of the larynx and the transverse and anteroposterior diameter of the cricoid cartilage were greater in male specimens [16]. Ajmani additionally demonstrated that the degree of angulation at the junction of the right and left thyroid cartilages in the midline anteriorly was 89 degrees in males and 106 degrees in females. The standard deviation of 28.3 degrees and the range of the thyroid cartilage angle in males (60 to 106 degrees) and females (88 – 132 degrees) in that series suggests that considerable anatomical variation and overlap exists in the structure within a normal population [16]. The angles observed in our study were 95.6° for males and 118.6° for females is consistent with the figures of 90° and 120° reported in cadaveric dissection of European subjects [17, 18]. Eckel reported thyroid angles in German subjects of 70.25° in males and 88.39° in females similar to that of a Swedish population [12, 19]. Angles of 85.25° and 97.85° were reported by Jain in Indian males and females respectively [20]. While confirming the intergender difference that we have demonstrated using ultrasound, these interethnic variations may have implications for accurate localization of the CTM in these populations. A further potential anatomic difference between genders that may lend itself to easier localization of the CTM in males is the consistently greater size of the adjacent cartilaginous structures which is supported by numerous cadaveric dissection studies [12, 16, 20–23].Both the vertical height and width of the CTM itself are greater in males which present a clinician with a larger target to locate [24]. Similar studies have also identified age related changes which may also have implications for locating these structures in younger subjects [25].Figure 4

Bottom Line: Incorrect identification of the CTM was more common in females (29/36 vs. 11/36, P < 0.001) and the distance from the CTM in the vertical plane was greater (11.0 [6.5-20.0] vs. 0.0 [0.0-10.0] mm, P < 0.001).CTM localisation is more difficult in female subjects irrespective of body habitus.It may be prudent to localize this structure by additional means (e.g. ultrasound) in advance of any airway manoeuvres or to modify the cricothyrotomy technique in the event that it is necessary in an emergency.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesia, The Rotunda Hospital, Parnell Square, Dublin 1, Ireland.

ABSTRACT

Background: The cricothyroid membrane (CTM) is the recommended site of access to the airway during cricothyrotomy to provide emergency oxygenation. We sought to compare the ability of physicians to correctly identify the CTM in male and female patients.

Methods: In a prospective observational study, anaesthetists were asked to locate the CTM by palpation which was then identified using ultrasound and the distance between the actual and estimated margin of the CTM was measured. Participants assessed the ease of CTM palpation using a visual analog scale. In a second series, the angulation of the posterior junction of the thyroid laminae was measured using ultrasound.

Results: 23 anaesthetists and 44 subjects participated. A total of 36 assessments were carried out in each gender. Incorrect identification of the CTM was more common in females (29/36 vs. 11/36, P < 0.001) and the distance from the CTM in the vertical plane was greater (11.0 [6.5-20.0] vs. 0.0 [0.0-10.0] mm, P < 0.001). In females distance from the CTM correlated positively with neck circumference (P = 0.005) and BMI (P = 0.00005) and negatively with subject height (P = 0.01). Posterior thyroid cartilage angulation was greater in females (118.6 ± 9.4° vs. 95.9 ± 12.9°, P = 0.02) and was lower in patients with correctly identified CTMs (100.0 ± 14.9° vs. 115.6 ± 15.9°, P = 0.02). VRS palpation correlated with decreased posterior thyroid cartilage angulation (P = 0.04).

Conclusions: CTM localisation is more difficult in female subjects irrespective of body habitus. It may be prudent to localize this structure by additional means (e.g. ultrasound) in advance of any airway manoeuvres or to modify the cricothyrotomy technique in the event that it is necessary in an emergency.

Show MeSH
Related in: MedlinePlus