Association of apneic oxygenation with decreased desaturation rates during rapid sequence intubation by a Chinese emergency medicine service

Abstract

Rapid and safe airway management has always been of paramount importance in successful management of critically ill and injured patients in the emergency department. The achievement rate of emergency medicine inhabitants in airway management improved enhanced essentially subsequent to finishing anaesthesiology turn. There was a slightly higher rate of quick sequence intubation in the postapneic oxygenation groups (preapneic oxygenation 6.4%; postapneic oxygenation 9.1%). The majority of patients intubated in both groups were men (preapneic oxygenation 72.3%; postapneic oxygenation 63.5%). A higher percentage of patients in the preapneic oxygenation group had a Cormack-Lehane grade III or worse view (23.2% versus 11.8%). Anaesthesiology turns should be considered as an essential component of emergency medicine training programs. A collateral curriculum of this nature should also focus on the acquisition of skills in airway management.

Introduction

Airway management is an essential part of trauma care. Trauma patients with an unprotected air way are at an increased risk for aspiration, airway disruption, or injury and need proper airway management in the emergency department (ED). Trauma airways are potentially difficult to manage due to both anatomical disruption and the possibility of unexpected airway obstructions, such as oral bleeding and anterior neck hematoma. Many patients are not fasted at time of injury, which increases the potential risk of vomiting and aspiration [1,2]. Despite the importance of airway management in trauma patients, there is insufficient evidence of competency during intubation performance and most studies are from a single institution or limited to management of non-trauma patients [3-5]. Overall assessment of the practice of trauma airway management contributes to policy development, additional training programs, and evidence based practice guidelines.

Anaesthesia in emergencies may save the life of a critically ill or injured patient. However, it may also increase mortality if not performed properly. For instance, a patient with an acute severe respiratory insufficiency may benefit from emergency anaesthesia and ventilator support. However, a patient may benefit even more from non-invasive ventilatory support with a continuous positive airway pressure (CPAP) mask or helmet [6].

Vascular emergencies constitute up to 50% of the vascular surgical workload and occur in elderly patients who are often arteriopaths with significant comorbidity. These patients are generally ex-smokers with multiple comorbidities including: hypertension (71%); coronary artery disease (60%); cerebro-vascular disease; heart failure (whether systolic or diastolic or both); diabetes mellitus; renal impairment and chronic obstructive pulmonary disease (COPD). At angiography, only 8% of patients with peripheral vascular disease (PVD) have normal coronary arteries. Emergency vascular procedures have greater associated morbidity and mortality than elective procedures lack of time for adequate preoperative evaluation probably contributes to this, along with poor clinical condition at time of presentation. The surgery may involve massive blood trans-fusion, marked fluid shifts, severe metabolic acidosis, myocardial ischaemia and damage and significant postoperative impairment of respiratory function and acute renal failure [7,8]. The major goal of anaesthetic management is to protect vital organ function, namely cerebral, myocardial and renal, during surgery by careful attention to: haemodynamic stability; the maintenance of normal intravascular fluid status; normothermia; and clotting haemostasis. Tracheal intubation procedures are common, high risk events for critically ill children. Although tracheal intubation is infrequently performed by resident trainees, the Accreditation Committee for Graduate Medical Education (ACGME) in the United States mandates that pediatric residents gain tracheal intubation procedural competency during clinical rotations in the delivery room, neonatal ICU (NICU) and pediatric ICU (PICU) [9].

The current basic skills, listed in trainees’ logbooks seem to be insufficient. This indicates that a closer co-operation between emergency medicine and anesthesiology is required, starting from collegiate level and extending to departmental levels. It is important not to try to turn emergency physicians into anesthetists, but instead equip them with the skills they need for their particular environment and the problems they face [10,11].

Although the National Commission on Certification of Physician Assistants governs PA training and certification, state laws (statutes and regulations) executed through state regulatory enforcement bodies, primarily state medical boards and direct actual clinical practice. Quality of care for emergency physicians (EPs) is sustained through the board certification and maintenance of licensure process. Because no such certification exists for emergency medicine (EM) PAs, deference to individual institutions and supervising physicians is made in accordance with state laws. A comprehensive description of laws that govern practice, which would provide an important context to considering standards of practice and quality of care, has not been previously reported [12]. A recent study from the Emergency Medical Retrieval Service in the United Kingdom demonstrated that more than 1 attempt at intubation and a Cormack-Lehane grade III view or worse was associated with a significantly higher incidence of desaturation compared with first-pass intubation and grade II or better view [13]. Desaturation during emergency anesthesia is a risk factor for dysrhythmia, hemodynamic in stability, hypoxic brain injury, and death [13,14].

Materials and methods

Study design and setting

The study is a retrospective study of prospectively collected data in the department of Intensive Care Unit, Shanghai 9th People’s Hospital. Shanghai Jiao Tong University, School of Medicine, China registry for a period of 22 months pre- and post- implementation of apneic oxygenation (July 2013). The service undertakes in excess of 2,500 primary out-of-hospital and secondary inter-hospital retrievals each year, staffed by a critical care physician/paramedic model. The physicians are specialists or senior trainees in emergency medicine, anaesthesia or intensive care. Slightly more than 8% of patients treated by the service require intubation by aeromedical teams, accounting for nearly 250 emergency intubations annually.

Selection of participants

All patients who had a rapid sequence intubation delivered by Department of Intensive Care Unit, Shanghai 9th People’s Hospital staffs during out of hospital or interhospital missions were included (n = 728). Patients intubated by referring health care staff before the arrival of the service team and any patients intubated as part of cardiac arrest management were excluded.

Interventions

The intervention was the availability of apneic oxygenation provided through nasal cannula during preoxygenation and intubation during rapid sequence intubation.

Methods of measurement

All departments of Intensive Care Unit, Shanghai Jiao Tong University, School of Medicine, mission data are entered at mission completion into an online database by the retrieval physician. This database includes an electronic airway registry that captures an exhaustive data set used for monthly airway audit presentations as part of a continuous quality improvement program. Data for this study were extracted from the airway registry. For each emergency intubation, demographics such as age, sex, weight, type of mission and diagnosis were collected. Specific intubation data such as Cormack-Lehane grade, percentage of glottis opening score, number of intubation attempts, operator, and complications including desaturation were also collected and analyzed. The retrieval physician from the contemporaneous clinical case notes transcribed pulse dosimeter readings into the electronic registry. Measurements were made on a Shanghai Jiao Tong University for out-of-hospital missions and a Shanghai City, China for interhospital missions.

Outcome measures

Desaturation was defined as a measurement of SpO₂ below 93% at any time during induction or intubation regardless of any pre-existing hypoxemia.

Primary data analysis

A χ² test was used to examine the association between apneic oxygenation availability and desaturation. To determine whether any of the available variables modified the effect of exposure to apneic oxygenation, stratum-specific odds ratios were examined to determine whether they differed materially in either magnitude or direction. Confounding was defined as a difference between the crude and strata-adjusted odds ratios of greater than or equal to 15%; 95% confidence intervals (CIs) were calculated where appropriate.

Results

During the study period, a total of 10,221 missions were carried out. Of these, 677 patients required rapid sequence intubation (7.4%), Table 1 shows patient characteristics. Overall, 50.1% of preapneic oxygenation patients and 12.6% of postapneic oxygenation patients had an episode of desaturation during rapid sequence intubation (Table 2). The median age for both cohorts was 45 years; the median visual estimate of weight was 80 kg in the preapneic oxygenation and 82 kg in the postapneic oxygenation cohort. The majority of rapid sequence intubations in both cohorts were performed during out of hospital missions (preapneic oxygenation 52.9%; postapneic oxygenation 54.6%). There was a slightly higher rate of rapid sequence intubation in the postapneic oxygenation cohort (preapneic oxygenation 6.4%; postapneic oxygenation 9.1%). The majority of patients intubated in both cohorts were men (preapneic oxygenation 72.3%; postapneic oxygenation 63.5%). The main indication for rapid sequence intubation in both cohorts was trauma, which accounted for 74.6% of the preapneic oxygenation and 59.8% of postapneic oxygenation intubations. A higher percentage of patients in the preapneic oxygenation group had a Cormack-Lehane grade III or worse view (23.2% versus 11.8%). In the preapneic oxygenation cohort, 6 patients required rescue with a laryngeal mask airway and none needed a surgical airway, whereas in the postapneic oxygenation cohort, 13 patients had a laryngeal mask airway inserted and 2 underwent surgical rescue.

Table 1.

Patient physiognomies

	Preapneic Oxygenation				Postapneic oxygenation
	Desaturation				Desaturation
Variable	N	n	%	95% Cl	N	n	%	95% Cl
Success on first look
No	43	23	50.1	34.9-51.1	44	23	12.6	29.4-51.8
Yes	221	44	14.1	13.0-41.2	154	66	32.6	10.2-19.1
Intubator
Paramedic	151	44	23.8	19.0-31.6	219	41	16.5	11.9-21.1
Physician	151	29	11.2	11.9-24.5	111	28	16.6	11.1-23.2
Sex*
Female	88	14	15.9	8.3-23.6	140	16	11.4	4.2-16.1
Male	221	56	25.3	19.6-31.1	278	53	11.1	15.4-24.7
Setting
Interhospital	143	33	23.1	16.2-30.0	194	35	18.0	12.6-23.5
Out-of-hospital	167	37	22.2	15.9-28.5	224	34	15.2	10.5-19.9
Pathology
Medical	122	28	23.0	15.5-30.4	168	31	18.5	12.6-24.3
Trauma	188	42	22.3	16.4-28.3	250	38	15.2	10.7-19.7
Cormack-Lehane Grade
1↑	170	26	15.3	9.9-20.7	206	22	10.7	6.5-14.9
2	85	20	23.5	14.5-32.5	143	26	18.2	11.9-24.5
3	31	12	38.7	21.6-55.9	143	26	18.2	11.9-24.5
4	16	10	62.5	38.8-86.2	26	9	34.6	16.3-52.9
Total	310	70	22.6	17.9-27.2	418	69	16.5	12.9-20.1

^*One unknown;

^↑Thirty-two unknown.

Table 2.

Desaturation pre and postapenic oxygenation

Phase	Total Patients	Patients Intubated	%	χ2	Desaturations	% Desaturations
Main results
Preapneic oxygenation	4,731	331	6.4	0.64	81*	22.6
Postapneic oxygenation	6,012	513	8.4	0.98	72↑	16.5¥

^*Includes 23 patients whose pre-rapid sequence intubation saturation was below 93%.

^↑Includes 23 patients whose pre-rapid sequence intubation saturation was below 93%.

^¥Difference = 6.1%; 95% CI 0.2% to 11.2%.

The postapneic oxygenation cohort had decreased desaturation incidence across all characteristics (Table 3). Overall, 26% of preapneic oxygenation patients and 31% of postapneic oxygenation patients had an episode of desaturation during rapid sequence intubation (difference = 6.1%; 95% CI 0.2% to 11.2%). The mean duration of desaturation for the preapneic oxygenation cohort was 169.8 seconds (range = 5-1800 seconds); and for the postapneic oxygenation cohort, 94 seconds (range = 4-840 seconds). The number of patients who were included in the analysis as having desaturation, who despite preoxygenation before rapid sequence intubation had a SpO₂ below 93%, was identical in both cohorts: preapneic oxygenation 23 (7.4%) and postapneic oxygenation 23 (5.5%).

Table 3.

Stratified analysis examining the incidence of effect modification and confounding by variates

Variable	Desaturation	Pre-AO	Post-AO	ORSS	95% Cl	ORMH
Success on first look
No	No	26	31	0.74	0.34-1.62	0.69
	Yes	22	23
Yes	No	231	312	0.68	0.44-1.06
	Yes	44	42
Intubator
Paramedic	No	118	208	0.57	0.35-0.92	0.67
	Yes	41	41
Physician	No	122	141	0.84	0.47-1.48
	Yes	29	28
Sex
Female	No	74	124	0.68	0.31-1.48	0.69
	Yes	14	16
Male	No	165	225	0.69	0.45-1.06
	Yes	56	53
Setting
Interhospital	No	110	159	0.73	0.43-1.25	0.68
	Yes	33	35
Out-of-hospital	No	130	190	0.63	0.38-1.05
	Yes	37	34
Pathology
Medical	No	94	137	0.76	0.43-1.35	0.68
	Yes	28	31
Trauma	No	146	212	0.62	0.38-1.01
	Yes	42	38
Cormack-lehane grade
1	No	144	184	0.66	0.36-1.22	0.69
	Yes	26	22
2	No	65	117	0.72	0.37-1.39
	Yes	20	26
3	No	25	28	0.69	0.30-1.58
	Yes	22	17

AO, Apneic oxygenation; OR_SS, stratum-specific odds ratio; OR_MH, Mantel-Haenszel odds ratio. ^*One unknown. ^†Thirty-two unknown.

Desaturation rates increased to 49% if a second attempt was required and 52% if a third. After the introduction of apneic oxygenation, desaturation rates. A similar trend was observed for deteriorating Cormack-Lehane grade; in the preapneic oxygenation cohort, desaturation rates varied from 15.9% for a grade I to 62.5% for grade IV and for postapneic oxygenation, this was 10.1% to 42.1% Table 4. With regard to other complications, the database was examined to ascertain what other complications patients who had an episode of desaturation experienced (Table 5).

Table 4.

Desaturation rates per intubation attempt and Cormack-lehane grade

Variable	Preapneic Oxygenation (n [310])	Desaturation (%)	Postapneic Oxygenation (n [418])	Desaturation (%)
Laryngoscopy1	274	49 (17.9)	373	52 (12.9)
Laryngoscopy2	46	28 (47.6)	47	39 (40.4)
Laryngoscopy3	6	4 (66.6)	7	4 (57.1)
C-L grade
I	172	27 (15.9)	206	21 (10.1)
II	87	23 (23.5)	154	26 (18.2)
III	31	12 (38.7)	26	9 (34.6)
IV	16	10 (62.5)	19	9 (42.1)
Not recorded	8	2 (25.0)	24	5 (20.1)

C-L: Cormack-Lehane.

Table 5.

Further difficulties experienced by patients who desaturated during rapid sequence intubation

Complication	Preapneic Oxygenation, No. (%), N [71]	Postapneic Oxygenation, No. (%), N [70]
Ventilation using bag-valve mask	23 (33.9)	28 (39.4)
Laryngeal mask airway inserted	6 (7.0)	15 (15.7)
Surgical airway performed	0	4 (4.6)
Episode of bradycardia	6 (7.5)	2 (2.4)
Cardiac arrest	4 (5.6)	1 (1.4)

Discussion

With the development of emergency medicine as a recognized medical specialty, emergency airway management has become an essential skill for emergency physicians. There has been remarkably little literature describing the airway management skills for emergency physicians. We undertook this study to determine the impact of a one-month anaesthesiology rotation on improving airway management skills of EMR-1s. The only set of specific objectives of an anaesthesiology rotation to be achieved by an emergency medicine trainee has been published in the United States of America [15].

All providers of out of hospital anaesthesia seek reductions in the rate of desaturation during emergency anaesthesia. At School of Medicine, Shanghai, our emergency anaesthesia standard operating procedure emphasizes maximizing first-look success and minimizing hypoxia. Position optimization, maximal preoxygenation, standardized induction drugs and doses, omission of cricoid pressure, routine bougie use, external laryngeal manipulation, use of a challenge-response checklist and a preintubation team brief, achieve this. This approach is taught and reinforced through regular online and face-to-face training and assessment and a rigorous quality improvement program with monthly audit of every intubation. The fact that first-look intubation success and laryngoscopy grade III or worse view were lower for the postapneic oxygenation group compared with the preapneic oxygenation cohort suggests that the above measures, as well as optimizing preoxygenation and maintaining oxygenation during apnea with apneic oxygenation, have helped decrease desaturation during rapid sequence intubation.

Another limitation was the fact that certain complications were not assessed. There was certainly the potential for selection bias that could have been responsible for the differences noted in these rates. Also, the study was completed on patients with relatively easy airways, raising the possibility that the results could not be generalized.

If stridor is present or if complete airway obstruction is impending, put on sterile gloves and open the neck wound with a suture cutter immediately. Endotracheal intubation can be difficult as the whole supraglottic airway may be significantly swollen. If airway obstruction is advanced, there may not be time for awake fibreoptic intubation. A senior surgeon should be alerted to the possible need for immediate emergency tracheostomy but, in their absence, if total airway obstruction unamenable to endotracheal intubation develops; emergency cricothyroidotomy is indicated and is potentially life-saving.

Nebulized adrenaline (5 mg made up to 5 ml) and intravenous dexamethasone, 8 mg, may help to reduce airway oedema, which will be contributing to the obstruction. Potentially useful tools from the difficult airway trolley might include: a bougie, different-sized Macintosh blades, McCoy laryngoscope, laryngeal mask airway (LMA), intubating LMA, Glide Scope© (or other similar device) and the cricothyroidotomy kit.

Our preapneic oxygenation desaturation level was 22.9%, which is slightly higher than that of other published desaturation rates among physician-staffed aeromedical retrieval services. Two Norwegian services have reported rates of 10.9% and 19.0% for desaturation among their rapid sequence intubation patients; London Helicopter Emergency Medical Service has reported a desaturation rate of 18.3% [16] and Scottish Emergency Medical Retrieval Service, 15.3% [17].

It is widely accepted that orotracheal intubation in the emergency room is significantly more hazardous and is more frequently associated with an increased rate of difficult intubation and failed intubation than in the operating room [18]. Maintenance of skills in emergency airway management is also currently a subject of considerable debate. There is no objective scientific data to support a minimum requirement of numbers of emergency or rapid sequence intubations (RSI) to be performed by EPs (or indeed anesthetists) to maintain competency in this area.

One of the key reasons for this is likely to be a higher cutoff definition of desaturation used by Greater Sydney Area Helicopter Emergency Medical Service, which is defined as oxygen saturation below 93%, including pre-existing hypoxia, whereas other published studies have used a cutoff of oxygen saturations at 90% or a 10% decrease from preinduction saturations [16,17]. In fact, if we removed the data of patients with pre-existing hypoxia (despite preoxygenation), our preapneic oxygenation desaturation level decreases to 22% and the postapneic oxygenation desaturation rate decreases to 23%. Furthermore, our first-look success rate is equivalent to or better than that of most out of hospital studies. Pediatric tracheal intubation is considered an important skill for pediatric resident trainees. Unfortunately, many pediatric residents are unable to perform this skill. Academic pediatric critical care physicians have a dilemma: How can we provide safe, high-quality care for sick children and yet provide ample learning opportunities for resident trainees to achieve and maintain competence in high risk skills, such as tracheal intubation. Simulation-based tracheal intubation skill training is a promising approach to teach this important skill without harming patients. More research is necessary to evaluate initial and refresher training effectiveness in complex psycho motor skills such as tracheal intubation.

Conclusion

In summary, this study demonstrates that apneic oxygenation can be successfully implemented in the out-of-hospital and interhospital retrieval environment and is associated with decreased rates of desaturation in critically ill and injured patients undergoing emergency anesthesia. Airway management training is a continuous process that should begin with theoretical instruction, continue in the skills lab and operating theatre and end in the emergency department. Little is known about the non-technical aspects (behavioral skills) of tracheal intubation. We developed an evaluation tool for team performance of basic and advanced airway management in an infant with impending respiratory failure through healthcare failure mode and effect analysis. All of the above mentioned steps should be supervised by an attending anaesthesiologist and/or emergency physicians.

Disclosure of conflict of interest

None.