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Clinical and ultrasonographic assessment of airway indices among non-pregnant, normotensive pregnant and pre-eclampsia patients: a prospective observational study
Abstract
Background:
Prediction of a difficult airway is of paramount importance for an anaesthesiologist. Various anatomical and physiological factors contribute to a difficult airway in pregnant females, especially those with pre-eclampsia. The aim of the study was to assess airway indices using both routinely used clinical methods and ultrasound.
Methods:
Fifty-five non-pregnant females, 55 normotensive pregnant females and 55 females with pre-eclampsia were included in this prospective study. Clinical airway assessment was the modified Mallampati score, thyromental distance, hyomental distance, hyomental distance ratio, chest circumference, neck circumference and chest-to-neck circumference ratio. Sonographic assessment included tongue width, tongue volume, anterior neck soft tissue thickness at the level of hyoid, epiglottis and vocal cords, subglottic diameter, ratio of pre-epiglottic space to anterior, posterior and midpoint of anterior and posterior vocal folds.
Results:
Several significant differences were observed between pregnant and non-pregnant females, with additional changes in pre-eclamptic females. These included clinical parameters such as the modified Mallampati score and sonographic measurements of tongue width, tongue volume, subglottic diameter, anterior neck soft tissue thickness at the level of hyoid, epiglottis and vocal cords, and the ratio of pre-epiglottic space to anterior, posterior and midpoint of anterior and posterior vocal folds.
Conclusion:
Routinely used clinical methods of airway assessment lack sensitivity and specificity. Ultrasound can visualise anatomical structures in the supraglottic and subglottic views and is encouraging as an airway assessment tool.
Background. The relevance of the review is due to the increasing development of ultrasound and its role in anesthesiological practice, in particular, as a method of predicting difficult cases of intubation of the respiratory tract. Objective. To analyze the literature on the clinical significance of ultrasound parameters for the diagnosis of difficult intubation. Material and methods. A total of 33 literature sources were analyzed. Results. Information was obtained on the presence in anesthesiological practice of a number of ultrasound parameters, that to one degree or another have a direct relation to difficult intubation. Conclusions. Based on research, it has been established that separately some ultrasound parameters have a fairly high sensitivity in predicting difficult intubation, but when several parameters are combined, their effectiveness as predictors of problems in prosthetics of the respiratory tract increases significantly, and in some cases these methods have greater prognostic value than the modified Mallampati score and the Kormack-Lehane score.
( Int J Obstet Anesth . 2023:54:103637)
Improper airway management is one of the leading causes of death for pregnant individuals. An ultrasound of the airway is a noninvasive tool that can be used to assess a patient’s airway and evaluate the risk of severe complications. This study aimed to compare the airways of pregnant and nonpregnant individuals using both a physical exam and an ultrasound exam.
Objective: The ultrasound-guided interventions have gained widespread popularity in several aspects of anesthesia practice. In this study, we aimed to compare the preoperative evaluation tests and sonographic measurements of the upper airway for the prediction of a potentially difficult airway. Material and Methods: In this prospective observational study, we enrolled 136 adult patients undergoing elective surgery under general anesthesia. The Modified Mallampati classification, thyromental distance, sternomental distance, and Cormack-Lehane scores were recorded. Sonographic measurements included pre-epiglottic space (PES), the distance between the midpoints of vocal cords and epiglottis (EVC). The ratio was interpreted. Main outcome is to determine the sensitivity and specificity of the upper airway ultrasound for the prediction of a potentially difficult airway. Results: There was no statistically significant relationship between body mass index value and thyromental distance, Thyromental/Sternomental Ratio and PES/EVC ratio, Cormack-Lehane, Mallampati classification and thyromental/sternomental distance ratio (p>0.05). The sonographic measurements of airway have no significance to predict the difficult intubation and the comparison between PES, EVC and the PES/EVC ratio and assessment tests (Cormack-Lehane, Mallampati classification, thyromental and sternomental distances) was insignificant. The sternomental distance measurement was predictive for the difficult airway only in patients having body mass index more than 31.6 kg m-2. Conclusion: Ultrasound is a useful tool for identifying the upper airway prior to anesthesia but the validity for the prediction of difficult airway is not clear. By increasing the clinical experiences and further investigations, a greater insight into its use will be gained.
Objective
To investigate the accuracy of using the ratio of pre-epiglottis space distance (Pre-E) and the distance between the epiglottis and the vocal folds (Pre-E/E-VF) measured by the ultrasound to predict potential difficult airway in the Chinese population.
Design
A prospective clinical study.
Setting
The pre-operative assessment service clinic of Tuen Mun Hospital.
Patients
Patients with age of 18 years or above, who were scheduled for elective surgery requiring general anesthesia with direct laryngoscopy and tracheal intubation.
Results
A total of 113 patients with direct laryngoscopic assessment during elective operations were included. Thirty-nine (34.5%) patients had potential difficult airway which was defined as documented Cormack–Lehane classification grade 2b, 3, or 4 by the anesthetists. Measurement of the distance from the epiglottis to the anterior vocal folds (Pre-E/aVF) ratio had better inter-rater reliability and accuracy comparing to the measurements of the distances from the epiglottis to the midpoint between the vocal folds and to the posterior vocal folds. The performance of using the Pre-E/aVF ratio to predict potential difficult airway was compared with other clinical tests (the Mallampati classification, the thyromental distance and the neck circumference to thyromental distance ratio). By using the Pre-E/aVF ratio of 1, the sensitivity and specificity to predict a potential difficult airway were 79.5% and 39.2%, respectively (p = 0.044). The ultrasound assessment method had a comparable predictive value as the Mallampati classification (the area under the receiver operator characteristic curves 0.648 vs 0.687). The negative likelihood ratio of the ultrasound assessment method was the lowest among all the other airway assessment methods.
Conclusion
The ultrasound airway assessment method could serve as a non-invasive test and supplement the currently used clinical assessment methods. A lower cut-off point of the Pre-E/E-VF ratio should be used in the Chinese population.
Background: Failed intubation in obstetrics remains the most common cause of death directly related to anesthesia. Neck circumference has been shown to be a predictor for difficult intubation in morbidly obese patients. The aim of this study was to determine an optimal cutoff point of neck circumference for prediction of difficult intubation in obstetric patients.
Methods: Ninety-four parturients scheduled for cesarean section under general anesthesia were included in the study. Preoperative airway assessment and neck circumference were measured. Difficult intubation was the primary outcome according to the intubation difficulty scale (IDS), intubation reported difficult if the IDS score was ≥5.
Results: Univariate analysis showed that Mallampati score and neck circumference were positive predictors for difficult intubation (P = 0.005 and P = 0.011, respectively). Mouth opening, thyromental distance, sternomental distance, and the hyomental distance ratio were not useful predictors (P = 0.68, P = 0.87, P = 0.48, and P = 0.27, respectively). Logistic regression for the Mallampati score and neck circumference negative results as independent predictors of difficult intubation in obstetric (P = 0.53). Sensitivity analysis showed that neck circumference of 33.5 cm is the cutoff point to detect difficult intubation with 100% sensitivity (95% confidence interval [CI]: 69.2–100) and 50% specificity (95% CI: 38.9–61.1). The area under the curve for neck circumference was 0.746 (95% CI: 0.646–0.830) with a positive predictive value of 19.2 (95% CI: 9.6–32.5), a negative predicative value of 100 (95% CI: 91.6–100), and a P < 0.0001.
Conclusions: In obstetric patients, a neck circumference ≥33.5 cm is a sensitive predictor for difficult intubation.
Background and Aims: Difficult tracheal intubation is associated with serious morbidity and mortality and cannot be always predicted based on preoperative airway assessment using conventional clinical predictors. Ultrasonographic airway assessment could be a useful adjunct, but at present, there are no well-defined sonographic criteria that can predict the possibility of encountering a difficult airway. The present study was conducted with the aim of finding some correlation between preoperative sonographic airway assessment parameters and the Cormack–Lehane (CL) grade at laryngoscopic view in adult patients.
Material and Methods: This was a prospective, double-blinded study on 130 patients undergoing elective surgery under general anesthesia. Preoperative clinical and ultrasonographic assessment of the airway was done to predict difficult intubation and was correlated with the CL grade noted at laryngoscopy. The sensitivity, specificity, positive predictive value, and negative predictive values of the parameters were assessed.
Results: The incidence of difficult intubation was 9.2%. Among the clinical predictors, the modified Mallampati classification had the maximum sensitivity and specificity, and among the sonographic parameters, the skin to epiglottis distance had the maximum sensitivity and specificity to predict difficult laryngoscopy. A combination of these two tests improved the sensitivity in predicting a difficult laryngoscopy.
Conclusions: The skin to epiglottis distance, as measured at the level of the thyrohyoid membrane, is a good predictor of difficult laryngoscopy. When combined with the modified Mallampati classification, the sensitivity of the combined parameter was found to be greater than any single parameter taken alone.
Introduction: Choosing the correct Endotracheal Tube (ETT) size
is important in paediatric anaesthesia. The subglottic diameter
being the narrowest diameter of the paediatric upper airway
plays an important role in appropriate ETT size selection.
Aim: This study was planned to determine the accuracy of
Ultrasonography (USG) to assess the appropriate ETT size and
compare it with physical indices based formulae. The secondary
outcome was to assess the number of times the tube was
changed based on air leak test for USG estimated tube size.
Materials and Methods: After ethical committee approval,
a prospective clinical observational study for a period of one
year was conducted on 75 children (power of study 80%,
confidence interval 95%) aged one to 14 years of American
Society of Anaesthesiologists Physical Status (ASA) I and II
undergoing elective surgery under general anaesthesia with
orotracheal intubation. Parental consent was obtained. Preanaesthetic ultrasonography was performed on every patient
at the subglottic region. The tracheal subglottic diameter was
estimated to select the ETT size for cuffed and uncuffed tubes.
The size estimated by USG and that based on age and height
based formulae were compared with clinically used appropriate
tube size. Data analysis was done using IBM Statistical Package
for the Social Sciences (SPSS) version 20.0; One-way Analysis
of Variance (ANOVA) and t-test for comparison were used.
Results: USG predicted the appropriate ETT size (p
Background and Aims
Accurate prediction of the Cormack-Lehane (CL) grade preoperatively can help in better airway management of the patient during induction of anaesthesia. Our aim was to determine the utility of ultrasonography in predicting CL grade.
Methods
We studied 100 patients undergoing general endotracheal anaesthesia. Mallampati (MP) class, thyromental distance (TMD) and sternomental distance (SMD) were noted. Ultrasound measurements of the anterior neck soft tissue thickness at the level of the hyoid (ANS-Hyoid), anterior neck soft tissue thickness at the level of the vocal cords (ANS-VC) and ratio of the depth of the pre-epiglottic space (Pre-E) to the distance from the epiglottis to the mid-point of the distance between the vocal cords (E-VC) were obtained. CL grade was noted during intubation. Chi-square test was employed to determine if there was any statistical difference in the measurements of patients with different CL grades. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were calculated for the various parameters.
Results
The incidence of difficult intubation was 14%. An ANS-VC >0.23 cm had a sensitivity of 85.7% in predicting a CL Grade of 3 or 4, which was higher than that of MP class, TMD and SMD. However, the specificity, PPV and accuracy were lower than the physical parameters. The NPV was comparable.
Conclusion
Ultrasound is a useful tool in airway assessment. ANS-VC >0.23 cm is a potential predictor of difficult intubation. ANS-Hyoid is not indicative of difficult intubation. The ratio Pre-E/E-VC has a low to moderate predictive value.
Background: Unexpected difficult intubation that maybe considered to failed intubation is a major factor to be related to mortality and morbidity following general anesthesia. We aimed to elucidate the role of hyomental Distance in fully extended and neutral position of neck with other prevailing test and their possible correlation in predicting difficult laryngoscopy in parturient undergoing cesarean section.
Materials and Methods: After institutional approval and obtaining inform consents, 716 consecutive parturient ASA physical status I and II scheduled for elective cesarean section under general anesthesia, were enrolled to this study. Each patient was evaluated regarding Hyomental distance in extended (HMDe) and neutral position of neck(HMDn), Neck circumference to Thyromental Distance(NC/TMD), Ratio of height to Thyromental Distance(RHTMD), Modified Mallampatti Test (MMT) and Upper Lip Bite Test(ULBT) before induction. Laryngoscopic result was graded according to Cormack-Lehane Classification. Sensitivity, specificity, positive predictive value and AUC or ROC for each airway predictor in isolation and in comparison with each other was established.
Results: The sensitivity of HMDe and HMDn was 49.2 and 47.7% respectively. Sensitivity of MMT as an old predictive test was 79.3% in comparison with sensitivity of NC/TMD, RHTMD and ULBT (58.3%, 41.6% and 50.7% respectively). The differences of Area under Curve in all tests except ULBT were statistically significant (P < 0.05).
Conclusion: In addition to MMT (as an ancient predictor), NC/TMD and HMD in neutral position and fully extended of the neck; in parturient are good and reliable predictors of difficult laryngoscopy and intubation.
Background: Unexpected difficult intubation that maybe considered to failed intubation is a major factor to be related to mortality and morbidity following general anesthesia. We aimed to elucidate the role of hyomental Distance in fully extended and neutral position of neck with other prevailing test and their possible correlation in predicting difficult laryngoscopy in parturient undergoing cesarean section.
Materials and Methods: After institutional approval and obtaining inform consents, 716 consecutive parturient ASA physical status I and II scheduled for elective cesarean section under general anesthesia, were enrolled to this study. Each patient was evaluated regarding Hyomental distance in extended (HMDe) and neutral position of neck(HMDn), Neck circumference to Thyromental Distance(NC/TMD), Ratio of height to Thyromental Distance(RHTMD), Modified Mallampatti Test (MMT) and Upper Lip Bite Test(ULBT) before induction. Laryngoscopic result was graded according to Cormack-Lehane Classification. Sensitivity, specificity, positive predictive value and AUC or ROC for each airway predictor in isolation and in comparison with each other was established.
Results: The sensitivity of HMDe and HMDn was 49.2 and 47.7% respectively. Sensitivity of MMT as an old predictive test was 79.3% in comparison with sensitivity of NC/TMD, RHTMD and ULBT (58.3%, 41.6% and 50.7% respectively). The differences of Area under Curve in all tests except ULBT were statistically significant (P < 0.05).
Conclusion: In addition to MMT (as an ancient predictor), NC/TMD and HMD in neutral position and fully extended of the neck; in parturient are good and reliable predictors of difficult laryngoscopy and intubation.
Background:
Endotracheal intubation is important to carry out various surgical procedures. The estimation of endotracheal tube size is governed by narrowest diameter of the upper airway. The objective of the study was to assess the narrowest tracheal diameter by ultrasound for selection of the appropriate size endotracheal tube.
Materials and Methods:
After the approval of institution ethical committee and written informed consent, 112 patients aged 3 to 18 years of both genders with normal airways, scheduled for surgery under general anesthesia and intubation, were enrolled for this prospective clinical observational study. Preanesthetic ultrasonography of the subglottic region was performed by experienced ultrasonologist with a high-resolution linear array transducer in sniffing position for every patient and the subglottic tracheal diameter was estimated to select the appropriate-size endotracheal tube. The endotracheal tube, calculated on the basis of physical indices and by ultrasound, was statistically correlated with the appropriate size endotracheal tube used clinically for intubation.
Results:
The ultrasound guided selection criterion has estimated the appropriate-sized endotracheal tube better than physical indices (age or height)-based formulas. The estimated endotracheal tube size by ultrasound was significantly correlated with the clinically used endotracheal tube.
Conclusion:
Ultrasonography may be used for the assessment of the subglottic diameter of trachea in children to estimate the appropriate size endotracheal tube for intubation.
Background and Aims:
Difficult airway assessment is based on various anatomic parameters of upper airway, much of it being concentrated on oral cavity and the pharyngeal structures. The diagnostic value of tests based on neck anatomy in predicting difficult laryngoscopy was assessed in this prospective, open cohort study.
Methods:
We studied 341 adult patients scheduled to receive general anaesthesia. Thyromental distance (TMD), sternomental distance (STMD), ratio of height to thyromental distance (RHTMD) and neck circumference (NC) were measured pre-operatively. The laryngoscopic view was classified according to the Cormack–Lehane Grade (1-4). Difficult laryngoscopy was defined as Cormack–Lehane Grade 3 or 4. The optimal cut-off points for each variable were identified by using receiver operating characteristic analysis. Sensitivity, specificity and positive predictive value and negative predictive value (NPV) were calculated for each test. Multivariate analysis with logistic regression, including all variables, was used to create a predictive model. Comparisons between genders were also performed.
Results:
Laryngoscopy was difficult in 12.6% of the patients. The cut-off values were: TMD ≤7 cm, STMD ≤15 cm, RHTMD >18.4 and NC >37.5 cm. The RHTMD had the highest sensitivity (88.4%) and NPV (95.2%), while TMD had the highest specificity (83.9%). The area under curve (AUC) for the TMD, STMD, RHTMD and NC was 0.63, 0.64, 0.62 and 0.54, respectively. The predictive model exhibited a higher and statistically significant diagnostic accuracy (AUC: 0.68, P < 0.001). Gender-specific cut-off points improved the predictive accuracy of NC in women (AUC: 0.65).
Conclusions:
The TMD, STMD, RHTMD and NC were found to be poor single predictors of difficult laryngoscopy, while a model including all four variables had a significant predictive accuracy. Among the studied tests, gender-specific cut-off points should be used for NC.
Currently, the role of ultrasound (US) in anaesthesia-related airway assessment and procedural interventions is encouraging, though it is still ill defined. US can visualise anatomical structures in the supraglottic, glottic and subglottic regions. The floor of the mouth can be visualised by both transcutaneous view of the neck and also by transoral or sublinguial views. However, imaging the epiglottis can be challenging as it is suspended in air. US may detect signs suggestive of difficult intubation, but the data are limited. Other possible applications in airway management include confirmation of correct endotracheal tube placement, prediction of post-extubation stridor, evaluation of soft tissue masses in the neck prior to intubation, assessment of subglottic diameter for determination of paediatric endotracheal tube size and percutaneous dilatational tracheostomy. With development of better probes, high-resolution imaging, real-time picture and clinical experience, US has become the potential first-line noninvasive airway assessment tool in anaesthesia and intensive care practice.
Background:
Prediction of difficult mask ventilation (DMV) is as challenging as difficult laryngoscopy. Ultrasound could be a helpful tool in the prediction of these difficulties.
Objectives:
The purpose of this study was to evaluate the ability of pre-operative ultrasound assessment of neck anatomy in predicting DMV and difficult laryngoscopy in patients undergoing during elective surgery requiring tracheal intubation.
Design:
Prospective, single blind, observational study.
Setting:
Operating theatre of a teaching hospital in Italy from April 2018 to July 2018.
Patients:
A total of 194 patients aged more than 18 years, without neck masses, previous thyroid surgery or tracheotomy undergoing general anaesthesia and tracheal intubation for elective ear, nose and throat-surgery were included in the study.
Outcome measures:
Ultrasound distances were recorded with a linear 6 to 13 MHz ultrasound transducer: measurements included the minimum distance from the thyroid isthmus to skin surface, the minimum distance from the hyoid bone to skin surface (DSHB), the minimum distance from skin to anterior commissure of the vocal cords, the minimum distance from skin to trachea at the level of the jugular notch and the distance from skin to epiglottis midway. The degree of DMV and difficult laryngoscopy was quantified.
Results:
The mean (SD) of DSHB was 0.88 (0.3) cm in the easy mask ventilation group, 1.4 (0.19) cm in DMV group. The mean of DSHB and of the other ultrasound distances increased according to the DMV and difficult laryngoscopy level. The DSHB was correlated with an increase in the risk for DMV (0.61 [IQR 0.5 to 0.69]). DMV groups were associated with a greater ultrasound-measured DSHB.
Conclusion:
The prospective observational study confirms the relationship between ultrasound assessment of the anterior soft tissues of the neck and difficult laryngoscopy and DMV. DSHB and the other distances extend the available evidence, not only for difficult laryngoscopy but also for DMV.
Trial registration:
Clinicaltrials.gov. identified NCT03592758.
Background:
Preeclampsia is associated with greater narrowing of the airway than normal pregnancy, but it is not known if these changes worsen during labor and delivery. The aim of the study was to evaluate the airway during and after labor in women with or without preeclampsia.
Methods:
Twenty-five normal and 25 severely preeclamptic pregnant women in early labor were recruited in this single-center, prospective, case-control study. Airway assessment was performed (a) before active labor (b) within one hour of delivery and (c) 24-48 h postpartum. The Mallampati grade was the primary outcome. Sonographic measurements of tongue thickness, anterior neck soft tissue at the level of the hyoid bone and the vocal cords, thyromental distance, and neck circumference, were secondary outcomes.
Results:
The Mallampati score increased from the pre-labor to the post-labor period in both preeclamptic and normotensive patients (P=0.001 and P=0.002 respectively). A significant difference in tissue thickness at the hyoid level was observed between preeclamptic and normotensive patients pre-labor (P=0.035), post-labor (T2; P=0.05) and postpartum (T3; P=0.05). There was no significant difference in thyromental distance or neck circumference between groups at any time. The total duration of labor and a Mallampati change by one grade correlated (Spearman correlation coefficient 0.473).
Conclusion:
Airway sonography may provide useful bedside anatomical information for prediction of difficult laryngoscopy. The change in airway dimensions and the Mallampati score during labor may persist for 48 h postpartum in both groups. Those with prolonged labor are more susceptible to changes in airway dimensions.
Prediction of difficult laryngoscopy in emergency care settings is challenging. The preintubation clinical screening tests may not be applied in a large number of emergency intubations due to the patient's clinical condition. The objectives of this study were 1) to determine the utility of sonographic measurements of thickness of the tongue, anterior neck soft tissue at the level of the hyoid bone, and thyrohyoid membrane in distinguishing difficult and easy laryngoscopies and 2) to examine the association between sonographic measurements (thickness of tongue and anterior neck soft tissue) and difficult airway clinical screening tests (modified Mallampati score, thyromental distance, and interincisor gap).
This was a prospective observational study at an academic medical center. Adult patients undergoing endotracheal intubation for an elective surgical procedure were included. The investigators involved in data collection were blinded to each other's assessments. Demographic variables were collected preoperatively. The clinical screening tests to predict a difficult airway were performed. The ultrasound (US) measurements of tongue and anterior neck soft tissue were obtained. The laryngoscopic view was graded using Cormack and Lehane classification by anesthesia providers on the day of surgery. To allow for comparisons between difficult airway and easy airway groups, a two-sided Student's t-test and Fisher's exact test were employed as appropriate. Spearman's rank correlation coefficients were used to examine the association between screening tests and sonographic measurements.
The mean (±standard deviation [SD]) age of 51 eligible patients (32 female, 19 male) was 53.1 (±13.2) years. Six of the 51 patients (12%, 95% confidence interval [CI] = 3% to 20%) were classified as having difficult laryngoscopy by anesthesia providers. The distribution of laryngoscopy grades for all subjects was 63, 25, 4, and 8% for grades 1, 2, 3, and 4, respectively. In this study, 83% of subjects with difficult airways were males. No other significant differences were noted in the demographic variables and difficult airway clinical screening tests between the two groups. The sonographic measurements of anterior neck soft tissue were greater in the difficult laryngoscopy group compared to the easy laryngoscopy group at the level of the hyoid bone (1.69, 95% CI = 1.19 to 2.19 vs. 1.37, 95% CI = 1.27 to 1.46) and thyrohyoid membrane (3.47, 95% CI = 2.88 to 4.07 vs. 2.37, 95% CI = 2.29 to 2.44). No significant correlation was found between sonographic measurements and clinical screening tests.
This pilot study demonstrated that sonographic measurements of anterior neck soft tissue thickness at the level of hyoid bone and thyrohyoid membrane can be used to distinguish difficult and easy laryngoscopies. Clinical screening tests did not correlate with US measurements, and US was able to detect difficult laryngoscopy, indicating the limitations of the conventional screening tests for predicting difficult laryngoscopy.
To provide a current review of the literature regarding airway problems in pregnancy and management.
Obstetrical anesthesia is considered to be a high-risk practice that exposes the anesthesiologist to increased medicolegal liability. Anesthetic management of a parturient is a challenge because it involves simultaneous care of both mother and baby. Failure to appropriately manage a difficult or failed intubation increases the risk of hypoxemic cardiopulmonary arrest and/or pulmonary aspiration, resulting in a high probability of maternal morbidity and mortality.
Anesthesia is the seventh leading cause of maternal mortality in the United States. Anatomic and physiologic changes during pregnancy place the parturient at increased risk for airway management problems. It is essential to perform a thorough preanesthetic evaluation and identify the factors predictive of difficult intubation. Airway devices such as the laryngeal mask airway, ProSeal, intubating laryngeal mask airway, Combitube, and laryngeal tube are described and have been used during failed intubation in pregnant patients.
Teamwork between an anesthesiologist and an obstetrician is absolutely essential for the safety of both the mother and baby. Most of us tend to agree that airway emergencies have a way of occurring at the worst possible times. It is essential that all anesthesia care practitioners must have a preconceived and well thought-out algorithm and emergency airway equipment to deal with airway emergencies during difficult or failed intubation of a parturient.
There are no prospective studies that evaluated airway changes during labor. The purpose of this study was to evaluate airway changes in women undergoing labor and delivery.
Two studies were undertaken to evaluate airway changes during labor. The first study used the conventional Samsoon modification of the Mallampati airway class. The airway was photographed at the onset and the end of labor. Women with class 4 airways were excluded from initial participation. In the second study, upper airway volumes were measured using acoustic reflectometry at the onset and the conclusion of labor. Acoustic reflectometry software computed the values for the components of upper airway, oral volume, and pharyngeal volume.
In study 1 (n = 61), there was a significant increase in airway class from prelabor to postlabor (P < 0.001). The airway increased one grade higher in 20 (33%) and two grades higher in 3 (5%) after labor. At the end of labor, there were 8 parturients with airway class 4 (P < 0.01) and 30 parturients with airway class 3 or class 4 (P < 0.001). In study 2 (n = 21), there were significant decreases in oral volume (n = 21; P < 0.05), and pharyngeal area (P < 0.05) and volume (P < 0.001) after labor and delivery. No correlation was observed between airway changes during labor and duration of labor, or fluids administered during labor in either study.
Airways can change during labor. Therefore, a careful airway evaluation is essential just before administering anesthesia during labor rather than obtaining this information from prelabor data.
202: Gestational Hypertension and Preeclampsia
- ACOG Practice Bulletin No
Airway management in obstetrics
- Rudra
Ultrasonographic modification of Cormack Lehane classification for pre-anesthetic airway assessment
- Gupta