Comparison of modified chin lift technique with EC technique for mask ventilation in adult apneic patients.

BACKGROUND: Mask ventilation (MV) is an essential basic life support skill. We used chin lift maneuver for MV and named as modified chin lift technique (MCL). EC technique is most common technique used for MV. AIMS: The aim of this study is to compare the efficacy of both techniques for MV in term of expired tidal volume (TV). Secondarily, we also assessed the effect of experience on the performance of these both techniques. SETTINGS AND
DESIGN: The study area was operation theater of our hospital. This was a prospective, randomized, crossover study.
METHODS: A total 108 adults undergoing elective surgery under general anesthesia were recruited. In all patients, operators (novice/anesthesiologist) randomly performed both techniques either to start with EC or MCL technique. Expired TV was measured for one minute for each technique. STATISTICAL ANALYSIS: Paired t-test was used to compare TV. RESULTS AND
CONCLUSION: The mean TV was significantly higher in MCL group than EC group (528.08 [104.96] ml vs. 483.39 [103] ml; P < 0.001). The novice (521.89 [117.9] ml vs. 478.70 [130.29] ml; P < 0.001) as well as anesthesiologists (534.27 [110.85] ml vs. 488.08 [111.6] ml; P < 0.001) was able to generate significantly more TV with MCL technique than EC technique. The TV did not differ significantly between novice and anesthesiologist for EC technique (P = 0.474) or MCL technique (P = 0.187). Novices as well as anesthesiologist felt MCL technique more satisfactory (70%). CLINICAL TRIAL REGISTRATION: CTRI/2016/04/006874.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Mask ventilation (MV) is an essential airway skill. In 2015 American Heart Association guidelines, the recommendation for ventilation for the rescuers has remained same.[1] Chin lift is the simplest skill to maintain airway patency. For performing MV, however, they recommend EC technique. To perform a triple airway maneuver, EC technique has never been validated in the past.[2] Till now no study has been done to assess the efficacy of chin lift maneuver for MV in term of expired tidal volume (TV).

We used chin lift maneuver for MV after giving sniffing position in anesthetized patients. Hence, we called this technique as a modified chin lift technique (MCL). While giving training for resuscitation on mannequin, we noticed novice struggle to adapt with EC technique but with chin lift technique they could ventilate efficiently. We hypothesized that health-care providers will provide equal TV with both techniques. Hence, we conducted the study primarily to compare the efficacy of chin lift technique with EC technique in adult patients. Secondarily, we also assess the effect of experience and operators satisfaction on these techniques.

METHODS

The study received hospital Ethical Committee approval. We conducted a prospective, randomized, crossover study from September 2015 to May 2016 in our institute, M. S. Ramaiah Medical College, Bengaluru. The study was registered on www.ctri.nic.in (CTRI/2016/04/006874).

Adult patients aged >18 years, the American Society of Anesthesiologists (ASA) Physical Status I–III, scheduled for elective surgery under general anesthesia were recruited for the study. Exclusion criteria were anticipated difficult intubation, pregnancy, body mass index >30 (kg/m2), presence of nasogastric tube, and edentulous, history of obstructive sleep apnea. Written informed consent was obtained. The sequence of the technique was divided into EC-MCL technique and MCL-EC technique. Patients were randomly allocated to start with either EC-MCL technique or MCL-EC technique.

To assess the effect of experience, we included novice in the study. The operators were divided into two groups, i.e., novices and experienced. Interns who have graduated from medical school and pursuing internship were included in novices group (N). There previous airway management experience ranged from no experience to limited experience. An anesthesiologist who have finished anesthesia training and practicing anesthesia independently were included in the experienced group (A).

In EC technique, thumb and index finger encircle the neck of the mask while middle and ring finger are placed on the body of the mandible and the little finger providing subluxation of the mandible by generating upward thrust at the angle of mandible [Figure 1]. In MCL technique, thumb and index finger encircle the neck of the mask while middle, ring, and little finger are approximated together to perform chin lift maneuver [Figures 2 and 3].

Figure 1

EC technique

Figure 2

Modified chin lift technique (side view)

Figure 3

Modified chin lift technique (front view)

One week before starting of the study, novices were given introductory training describing each specific technique. This was followed by a period for practice on mannequin as well as on anesthetized patients under supervision in the operation theater. For anesthesiologists, training for MCL technique was given and was asked to practice on the anesthetized patients. Training was given daily for 1 h everyday for 1 week.

Anesthesia machine (Datex Ohmeda Aestiva® & Datex Ohmeda S/5 Avance, GE Healthcare, Madison, WI, USA) was checked and calibrated before the start of the study. All patients received premedication as per hospital protocol. On arrival inside the operation theater, standard ASA monitor was attached (electrocardiogram, noninvasive blood pressure, SpO2). Monitoring was done throughout the study. Every patient was positioned with head on the standard pillow. Patients were preoxygenated with 6 L of oxygen for the period of 3 min by primary anesthesia care provider who is not involved in this study. Induction of anesthesia was done with intravenous (IV) propofol 2 mg/kg, IV fentanyl 2 ug/kg. Oral airway was inserted if felt necessary by primary anesthesia care provider. If ventilation was inadequate with one hand, and two hands were used and these patients were excluded from the study. Ventilation was initiated using pressure-controlled ventilation at 15 cmH2O, at a rate of 12 breaths/min. Anesthesia was maintained with isoflurane. IV propofol 0.5 mg/kg was repeated every 2 min to maintain adequate depth of anesthesia. Once cessation of spontaneous respiration confirmed, the study was started. Novices were asked to hold the mask (Intersurgical®, Berkshire, UK) with either of technique. If oral airway was inserted, it was left in situ till the end of the study. The investigator who was not involved in the study manually recorded, expired TV data from the anesthesia ventilator screen. Initial faulty reading resulting from circuit leak due to operator and technique changeover were excluded from the study. The readings were recorded after achieving normal capnographic trace. The exhaled TV readings were taken for 1 min for each technique. Anesthesiologist who was not involved in the study auscultated over the patient epigastrium to assess gastric insufflation throughout the study period. Once novices complete the task, anesthesiologist was asked to hold mask. Each operator performed both techniques in crossover fashion [Figure 4].

Figure 4

Flowchart of methodology

Baseline patient characteristics were noted and included age, sex, weight, height, and Mallampati grading. Baseline operator characteristics included sex and handspan. Operator was asked to maximally stretch his or her fingers of the left hand and then place on white blank paper. Two marks were made for the thumb and little finger. The distance between two marks was recorded as handspan.

Inadequate MV was defined as exhaled TV <4 ml/kg associated with inadequate chest rise or oxygen saturation <90%. If adequate MV was not achieved then, such cases were excluded from the study. In these patients, primary anesthesia provider intervened for necessary airway management. Operators were allowed to see rise and fall in the chest but were blinded from TV readings. No mask repositioning was allowed during the study period.

Outcomes

The primary outcome was difference in the expired TV between techniques. As secondary outcome, we assessed the effect of experience on the technique. For this mean TV between novice and anesthesiologist were analyzed for each technique. In addition to TV, mask leak was assessed as either audible or not and noted such. Similarly, gastric insufflation was noted. Other parameters such as EtCO2, SpO2 were noted. If oxygen saturation was < 90% or EtCO2 <20 mmHg, data were recorded. After completion of MV task, operator's satisfaction was assessed for each technique.

Sample size

Joffe et al.[3] study has observed that the mean TV with one hand technique was 6.80 (3.1) ml/kg and with two hand technique was found to be 8.6 (2.31) ml/kg. In this study expecting similar results and to get the precision of 90% power, 95% confidence level with effect size of 0.35 in the results, the study requires minimum of 87 subjects. We enrolled total 108 patients in the study. As this study was planned to detect difference between techniques, each operator and patient combination represented as its own control.

Statistical analysis

Data were analyzed using IBM SPSS software version 18.0 (IBM Corporation, NY, USA 2010). Data are expressed as mean (standard deviation) for continuous variables and count (%) for categorical variables. Paired t-test was used to compare TV between two techniques and for comparing between two operators (since the same subject were used for both the techniques).

RESULTS

A total of 108 patients were enrolled in the study. In three patients, primary anesthesia care provider felt ventilation was inadequate with one hand and hence used two hands. These patients were excluded from the study. In another three patients, novice could not achieve adequate TV with either technique. In one patient, novice was able to ventilate with MCL technique but not with EC technique. In all these patients, primary anesthesia care provider intervened to assist ventilation and put laryngeal mask airway (LMA). In two patients, the study was abandoned as novice could not complete the study due to hand fatigue and repositioned the face mask. In three patients, we could not maintain apnea till the end of the study. Patients started breathing spontaneously; hence, the study was abandoned. Thus, ventilation task was successfully completed in 96 patients, and we took their data for analysis.

The demographic data and baseline characteristics are presented in Table 1. Total 38 operators (18 anesthesiologists and 20 novices) performed the mask ventilating tasks. Twenty-two operators were male, and 16 operators were female. Handspan of anesthesiologists were higher than novices (19.95 [1.16] vs. 19.49 [1.05] cm; P = 0.005).

Table 1

Patients baseline characteristics

There was significant increase in mean TV generated by MCL technique over EC technique (528.08 [104.96] ml vs. 483.39 [103] ml; P < 0.001) [Table 2]. Further analysis for novices and anesthesiologist revealed similar significant increase in mean TV by MCL technique. In novice group mean TV by MCL technique was 521.89 (117.9) ml while in EC technique was 478.70 (130.29) ml (P < 0.001). Similarly in anesthesiologist group the mean TV by MCL technique was 534.27 (110.85) ml while in EC technique it was 488.08 (111.60) ml (P < 0.001).

Table 2

Comparison of tidal volume between techniques

There was no difference between the TV generated by novice and anesthesiologists for both techniques. The mean TV generated by novice with EC technique did not differ with anesthesiologist (478.70 [130.21] vs. 488.08 [111.60] ml; P = 0.474) [Table 2]. Similarly there was no difference for MCL technique (521.89 [117.97] vs. 534.27 [110.85] ml; P = 0.187).

In 69 patients, novices reported MCL technique was more comfortable than EC technique (71.9% vs. 28.1%). In 68 patients, anesthesiologists felt the MCL technique was more comfortable than EC technique (70.8% vs. 29.2%).

None of the technique demonstrated audible air leak around mask or gastric insufflation. In every patient, SpO2 remained above 90% and EtCO2 above 20 mmHg.

DISCUSSION

The main findings of our study are that MCL technique is superior to generic EC technique for providing ventilation by pressure control ventilation (PCV) in apneic patients under general anesthesia. The experience was not the factor to influence MV with either technique. Further, the ease and comfort were more with MCL technique.

The triple maneuver used to maintain open airway are head tilt, chin lift, jaw thrust.[4] There is dilemma amongst health care provider regarding which maneuver primarily to be used in EC technique.[5] Patency of upper airway depends on the stretch of the anterior neck structures between larynx and chin. Pioneering work done in the past has validated head extension as an effective maneuver to maintain upper airway patency.[67] We feel in MCL technique; the head extension is better achieved than EC technique. The middle, ring and little finger in MCL technique are approximated together to firmly lift the chin in the midline which results in optimal head extension. However, EC technique does not place middle and ring finger for optimal chin lift maneuver.[2]

Many standard anesthesia textbooks cites the fifth finger at the left mandibular angle while performing EC technique.[489] In EC technique, a relatively thinner fifth finger has to provide upward force to pull angle of mandible (subluxation). Hence, it may lead to fatigue in case of prolonged MV. In EC technique, pressure is applied unilaterally; thus, making mask seal relatively weaker on opposite side. In MCL technique, index finger and thumb can reach on the right side of mask providing more uniform mask seal. EC technique may not ideal as it holds the mandible body and tends to push the submandibular region.[10] Adult left-hand grip does neither generate nor maintain a measurable jaw thrust using this mask design.[2411] Change in the grip and facemask design with chin lift maneuver has been suggested to improve one-handed ventilation but are yet to be validated.[2512] Our study was able to achieve good TV with generic mask with simple chin lift maneuver.

In our study, we selected pressure-controlled ventilation. Inadequacy of face MV is indicated by low TV in pressure controlled ventilation and high airway pressure in volume controlled ventilation. Inability to ventilate the patient with 25 cmH2O of positive airway pressure should rule out upper airway obstruction.[4] The risk of gastric insufflation is least with an inspiratory pressure of 15 cmH2O without compromising an effective ventilation.[13] PCV allows standardization of airway pressure, inspiratory time, and thus representing TV as a good surrogate to upper airway patency.[3]

Even for an experienced anesthesiologist, a handspan may not be large enough to maintain adequate jaw thrust while keeping pressure on the facemask to create a tight seal. However, the majority of anesthesiologists handspan are usually large enough to perform chin lift maneuver. We are routinely using this technique in our hospital. Our experience says this technique is most valuable in patients with certain facial features such as hollowed cheeks, large face as well as for anesthesiologists with smaller handspan.

In our study, we avoided the use of muscle relaxants. Use of muscle relaxant has shown to enhance the effectiveness of MV by reducing tone of muscles and their cross-sectional area.[14] It is deemed risky for rescuers with limited experience in airway management to use muscle relaxants for MV. Since all patients were adequately preoxygenated before the induction of anesthesia, we did not take oxygen saturation as a marker of efficacy. Use of oropharyngeal airway in some patients would have improved the upper airway patency and that results for both techniques would have been similar.

Our study has various limitations. This study was done under general anesthesia. Rescuers frequently encounter a situation where MV is required in a patient with altered mentation. The results may be different in uncontrolled setting where self-inflating bag is used in nonanesthetized patients. We did not assess the mask leak objectively. Hence, small leaks would have got unnoticed. Our study excluded patients with difficult airway. Hence, results of our study cannot be generalized. Further research is required to see if this technique also helpful to this important subgroup. Future investigation should aim at specific patients who may be benefitted better by MCL technique. Similarly, the standard definitions for effective MV in term of expired TV, airway pressure, carbon dioxide elimination are needed to be searched.

Trainees achieves better competence in newer generation alternative airway (LMA) than conventional facemask ventilation.[15] Suboptimal use of facemask as an airway management tool highlights the need for extra training for facemask ventilation.[16] In our study, novices as well as anesthesiologist reported more ease and comfort with MCL technique. We noticed strain on the little finger, and wrist joint was less with MCL technique. MCL technique is an easy skill to learn. As the design of a facemask has remained static for so many years, we believe simple mechanical intervention to hold the mask may improve the efficacy of MV and operators comfort.

The mean increase in TV of 45 ml in our study may not be clinically significant in a healthy subject. The average physiological oxygen consumption in a healthy subject is approximately 250 ml/min. Hence an increase in TV of 45 ml at 12 breaths/min leads to approximately 540 ml of minute volume which doubles the oxygen reserve. This is potentially significant in a hypoxic subject.

CONCLUSION

To conclude MCL technique generated substantial greater TV than EC technique in adult apneic patients. MCL technique was found more comfortable than generic EC technique. We suggest MCL technique should be taught to all health-care providers as an alternative option to EC technique for single-handed MV.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.