a b s t r a c t

Purpose: We performed two prospective randomized crossover trials to evaluate the effect of head elevation or lateral Head rotation to facemask ventilation volume.

Methods: In the first trial, facemask ventilation was performed with a 12-cm high pillow (HP) and 4-cm low pil- low (LP) in 20 female patients who were scheduled to undergo general anesthesia. In the second trial, facemask ventilation was performed with and without lateral head rotation in another 20 female patients. Ventilation vol- ume was measured in a pressure-Controlled ventilation (PCV) manner at 10, 15, and 20 cmH₂O inspiratory pres- sures.

Results: In the first trial evaluating head elevation effect, facemask Ventilation volume was significantly higher with a HP than with a LP at 15 and 20 cmH₂O inspiratory pressure (15 cmH₂O: HP _median540 [_IQR480-605] mL, LP 460 [400-520] mL, P = 0.006, 20 cmH₂O: HP 705 [650-800] mL, LP 560 [520-677] mL, P b 0.001). In the sec-

ond trial, lateral head rotation did not significantly increase facemask ventilation volume at all inspiratory pres- sure.

Conclusion: Head elevation increased facemask ventilation volume in normal airway patients, while lateral head rotation did not.

(C) 2017

Introduction

Facemask ventilation is the essential technique for airway manage- ment during resuscitation. Emergency physicians frequently encounter difficult facemask ventilation due to airway obstruction [1]. Though nasal or oral airway is an effective device for upper airway obstruction release, difficult facemask ventilation still occurs in non-negligible num- ber of patients [2-4].

Emergency physicians empirically perform head elevation or lateral head rotation to facilitate facemask ventilation. Previous reports have investigated the efficacy of head positioning on upper airway patency [5,6]. However, no quantitative evaluation has been performed on the effects of head elevation/lateral rotation on facemask ventilation vol- ume. As such evaluation in emergency situation may be unethical, we decided to perform these evaluation in the operation room.

We hypothesized that head elevation and lateral head rotation may facilitate facemask ventilation by increasing ventilation volume. To test this hypothesis, we performed two independent crossover clinical trials to assess facemask ventilation volume using mechanical ventilation in a pressure-controlled ventilation (PCV) manner.

* Corresponding author at: Department of Anesthesiology, Osaka Medical College, Daigaku-machi 2-7, Takatsuki City, Osaka 569-8686, Japan.

E-mail address: [email protected] (N. Komasawa).

Methods

The institutional ethical review board of Osaka Medical College ap- proved the study protocol. We registered this study in the University hospital Medical Information Network Clinical Trials Registry (Registra- tion number: UMIN000021507, UMIN000023019).

In the first trial, conducted in March and April 2016, we assessed 22 female patients for eligibility (Fig. 1). No patient refused to participate and two were excluded for not fulfilling the eligibility criteria because their body mass index was over 35. After obtaining written informed consent, 20 female patients aged 20 to 75 years undergoing general an- esthesia in the supine position were recruited. We excluded male pa- tients to unify the clinical trial condition based on a previous study, which reported that male sex was a risk factor for facemask ventilation [4]. The following patients were also excluded from the present study:

(1) those with anticipated difficult facemask ventilation such as morbid obesity (body mass index over 35), apparent short neck, and Sleep apnea syndrome, and (2) those with high risk of aspirating stomach contents.

Facemask ventilation was performed in a PCV manner with both 12- cm high pillow (HP) and 4-cm low pillow (LP) in the supine position in all patients. Pillows were cut-out cushions (4 cm height) typically used during induction of anesthesia. For the HP trial, cushions were tripled- over, resulting in an approximate height of 12 cm [7]. The vertical

http://dx.doi.org/10.1016/j.ajem.2017.05.004

0735-6757/(C) 2017

1710 S. Matsunami et al. / American Journal of Emergency Medicine 35 (2017) 1709-1712

Fig. 1. CONSORT flowchart in the first trial.

gaze was maintained in both HP and LP trial. The order of HP and LP tri- als was randomly assigned by the envelope method [8].

In the second trial, conducted in July and August 2016, 23 female pa- tients were assessed for eligibility (Fig. 2). None refused to participate and three were excluded for not fulfilling the eligibility criteria (two were morbid obesity and one gastro-esophageal reflex disease). After obtaining written informed consent, 20 female patients aged 20 to 75 years undergoing general anesthesia in the supine position were re- cruited. Facemask ventilation was performed in all patients both with and without lateral head rotation. Lateral head rotation was achieved by 30 degree clockwise measured by protractor. We decided this angle from the viewpoint of patient safety and our routine practice.

In both trials, we did not administer any premedication to patients. Anesthesia was induced with remifentanil 0.3-0.5 ug kg^-1 min^-1 and propofol 1.5-2 mg kg^-1. Rocuronium 0.9 mg kg^-1 was administered as Neuromuscular blockade to eliminate the incidence of laryngospasm [9]. Anesthesiologists determined the doses of propofol and remifentanil does on the basis of the patient’s condition. After loss of consciousness, anesthesiologists with N 5 years of clinical experiences performed facemask ventilation with two hand maneuvers using 3-5% sevoflurane in oxygen with the double hand technique which perform E-C clamp with both hands for yielding sealing pressure [10]. Cases with b 20 cmH₂O leak pressure or insufficient ventilation were excluded from the viewpoint of patient safety.

Facemask ventilation volume was measured by the ventilator at- tached to the anesthesia machine (Fabius GS(R), Drager, Germany) in the PCV mode with an inspiratory pressure of 10, 15, or 20 cmH₂O at 8 breaths per minute and a 1:2 inspiratory to expiratory ratio. The mea- surement started after confirming the zero count of train-of-four using TOF watch(R) (NIHON KOHDEN, Tokyo, Japan) [11]. Facemask ventilation volume was the average volume measured during 1 min. Measurement was performed at PCV in order (10, 15, 20), and the order of interven- tions was randomly assigned using the envelope method at each pressure.

We performed statistical analysis using JMP(R) 11 (SAS Institute Inc., Cary, NC, USA). Facemask ventilation volume, the primary outcome, was assessed using the Wilcoxon matched-pairs signed rank test and com- pared between groups. Data are expressed as either number of patients, mean (standard deviation (SD)), or median [interquartile range (IQR)]. A P-value b 0.05 was considered statistically significant.

For sample size calculation in the first trial, facemask ventilation vol-

ume at PCV 15 cmH₂O was about 500 +- 200 mL with a normal height pillow, and 800 +- 200 mL with a HP. We considered this 300 mL differ- ence clinically significant, as it was approximately 60% of the facemask ventilation volume with a normal height pillow. To detect this differ- ence with 80% power and 5% significance level, 16 patients were re- quired. To adjust for potential missing data, we planned to recruit 20 patients to each group. For sample size calculation in the second trial,

Fig. 2. CONSORT flowchart in the second trial.

S. Matsunami et al. / American Journal of Emergency Medicine 35 (2017) 1709-1712 1711

Table 1

Patient characteristics in the first trial evaluating head elevation effect. Data are shown in average (SD) or number of patients.

N = 20

Age (years) 50 (15)

Body weight (kg) 56 (11)

Height (cm) 157 (5)

BMI (kg/m²) 23 (4)

Mallampati classification 1/2/3/4 14/5/1/0

Table 3 Patient characteristics in the second trial evaluating lateral head rota- tion effect. Data are shown in average (SD) or number of patients.

N = 20

Age (years) 59 (15)

Body weight (kg) 56 (10)

Height (cm) 155 (7)

BMI (kg/m²) 24 (4)

Mallampati classification 11/9/0/0

facemask ventilation volume at PCV 15 cmH₂O was about 500 +- 200 mL without lateral head rotation, and 700 +- 300 mL. We estimated that lat- eral head rotation would increase the facemask ventilation volume about 200 mL difference clinically significant, as it was approximately 40% of the facemask ventilation volume without lateral head rotation. To detect this difference with 80% power and 5% significance level, 16 patients were required. To adjust for potential missing data, we planned to recruit 20 patients to each group.

Results

Facemask ventilation volume with a HP or LP

Patient characteristics including age, gender, height, body weight, body mass index, and Mallampati classification in the first trial are shown in Table 1. No case was lost or abandoned during the trial.

Table 2 shows facemask ventilation volume with a HP or LP. While facemask ventilation volume did not differ between groups at 10 cm H₂O (P = 0.223), it significantly improved with a HP than with a LP at 15 and 20 cmH₂O inspiratory pressure (15 cmH₂O: HP _median540 [_IQR480-605] mL, LP 460 [400-520] mL, P = 0.006, 20 cmH₂O: HP 705 [650-800] mL, LP 560 [520-677] mL, P b 0.001).

Facemask ventilation volume with or without lateral head rotation

Patient characteristics including age, gender, height, body weight, body mass index, and Mallampati classification in the second trial are shown in Table 3. No case was lost or abandoned during the trial.

Facemask ventilation volume did not differ significantly with or without lateral head rotation at any inspiratory pressure (P = 0.946, P = 0.636, P = 0.234) (Table 4).

Discussion

Several studies have evaluated the optimal head and neck positions for facemask ventilation, including pillow height assessments, resulting in the recommendation of the sniffing position for facemask ventilation in adults [12]. The sniffing position has been shown to be effective for direct laryngoscopy and intubation in normal airway. It is also effective for facemask ventilation and supraglottic device insertion [13]. To achieve an appropriate sniffing position, the neck should be flexed onto the chest and the head slightly extended at the atlanto-occipital joint [14].

In the present study, facemask ventilation volume was significantly higher with a HP than with a LP at pressure controlled ventilation at 15 cmH₂O and 20 cmH₂O. One possible reason for this is that the former can release glossoptosis more efficiently. In contrast, lateral head rota- tion did not significantly affect facemask ventilation volume, resulting in increase in some patients and decrease in others. This suggests that lateral head rotation does not always facilitate facemask ventilation and sometimes impedes it.

There are several limitations to our present study. First, facemask holding was performed by experienced anesthesiologists. Future stud- ies evaluating the head elevation and rotation to facemask ventilation by less experienced doctors are warranted [15]. Second, the present study was not a blinded study. A double-blinded design can provide clearer results [16].

In conclusion, head elevation increased facemask ventilation volume in normal airway patients, while lateral head rotation did not.

Author contributions

S.M. and N.K. contributed to the study design and implementation, statistical analysis, and manuscript preparation; Y.K. contributed to data collection and offered criticism of both manuscript preparation and Data interpretation; and T.M. contributed to the study implementa- tion and manuscript preparation. All authors discussed the methods and results, and approved the final manuscript.

Disclosure of funding

Institutional own funding.

Trial registry number

UMIN000021507, UMIN000023019.

Individuals or organizations to be acknowledged

None.

Conflicts of interest

None.

Table 2 Comparison of factors related to airway management between groups in the first trial evaluating head elevation effect. Data are expressed as median [IQR]. Data were analysed using the Wilcoxon matched-pairs signed rank test. ?P b 0.05 was considered statistically significant.

	LP trial n = 20	HP trial n = 20	P value
Facemask ventilation volume at pressure controlled ventilation at 10 cmH2O (mL)	350 [405-315]	382 [443-345]	0.223
Facemask ventilation volume at pressure controlled ventilation at 15 cmH2O (mL)	460 [400-520]	540 [480-605]	95% CI for median difference 11-43 0.006?
Facemask ventilation volume at pressure controlled ventilation at 20 cmH2O (mL)	560 [520-677]	705 [650-800]	95% CI for median difference 39-105 b 0.001?
			95% CI for median difference 78-146
LP trial: facemask ventilation was performed with low pillow.
HP trial: facemask ventilation was performed with high pillow.

1712 S. Matsunami et al. / American Journal of Emergency Medicine 35 (2017) 1709-1712

Table 4

Comparison of factors related to airway management between groups in the second trial evaluating lateral head rotation effect. Data are expressed as median [IQR].Data were analysed using the Wilcoxon matched-pairs signed rank test. ?P b 0.05 was considered statistically significant.

	With lateral head rotation	Without lateral head rotation	P value
	n = 20	n = 20
Facemask ventilation volume at pressure controlled ventilation at 10 cmH2O (mL)	280 [200-346]	280 [252-320]	0.946 95% CI for median difference -
			33-45
Facemask ventilation volume at pressure controlled ventilation at 15 cmH2O (mL)	428 [338-495]	431 [379-483]	0.636 95% CI for median difference -
			56-85
Facemask ventilation volume at pressure controlled ventilation at 20 cmH2O (mL)	574 [488-675]	630 [577-668]	0.234 95% CI for median difference -
			7-124

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