Big data: Airway management at a university hospital over 16 years; a retrospective analysis.

PURPOSE: Little is known about the current practice of airway management in Germany and its development over the last decades. The present study was, therefore, designed to answer the following questions. Which airway management procedures have been performed over the last 16 years and how has the frequency of these procedures changed over time? Is there a relationship between patient characteristics or surgical specialisation and the type of airway management performed?
METHODS: In the present study, we used our in-house data acquisition and accounting system to retrospectively analyse airway management data for all patients who underwent a surgical or medical procedure with anaesthesiological care at our tertiary care facility over the past 16 years. 340,748 airway management procedures were analysed by type of procedure, medical/surgical specialty, and type of device used. Logistic regression was used to identify trends over time.
RESULTS: Oral intubation was the most common technique over 16 years (65.7%), followed by supraglottic airway devices (18.1%), nasal intubation (7.5%), mask ventilation (1.6%), tracheal cannula (1.3%), double lumen tube (0.7%), and jet ventilation (0.6%). On average, the odds ratio of using supraglottic airway devices increased by 17.0% per year (OR per year = 1.072, 95% CI = 1.071-1.088) while oral intubation rates decreased. In 2005, supraglottic airway devices were used in about 10% of all airway management procedures. Until 2020, this proportion steadily increased by 27%. Frequency of oral intubation on the other hand decreased and was about 75% in 2005 and 53% in 2020. Over time, second-generation supraglottic airway devices were used more frequently than first-generation supraglottic airway devices. While second-generation devices made up about 9% of all supraglottic airway devices in 2010, in 2020 they represented a proportion of 82%. The use of fibreoptic intubation increased over time in otorhinolaryngology and dental, oral, and maxillofacial surgery, but showed no significant trends over the entire 16-year period.
CONCLUSION: Our data represent the first large-scale evaluation of airway management procedures over a long time. There was a significant upward trend in the use of supraglottic airway devices, with an increase in the use of second-generation masks while a decrease in oral intubations was observed.

Introduction

As failed airway management can have serious impact on patient outcome, the development and optimisation of guidelines is crucial. These airway management guidelines can be further developed and improved based on large clinical data sets. Such datasets are collected, for example, in patient databases such as NAP4 in the UK and the Danish Anaesthesia Database [1,2]. Charlesworth and Agarwal point out in their editorial that secondary analysis of data routinely collected by healthcare providers can help maximise the value of these data and provide meaningful clinical implications [3]. Greenland and Irwin argue that the meaningful use of large-scale patient data is only possible if the variables are mandatorily documented and stored in national databases [4].

In Germany, such a database for airway management does not yet exist, so that little is known about the current practice of airway management in Germany and its development over the last decades [5]. The last assessment of airway management practices at German university hospitals and university-affiliated teaching hospitals was conducted by means of a questionnaire survey after the publication of the first guidelines on airway management in 2004 [6]. In an effort to make the best use of data generated in healthcare facilities, we used routinely collected clinical data from University Medical Centre Mainz in Germany, as suggested by Charlesworth and Agarwal [3]. We performed a retrospective analysis of data collected over the past 16 years to identify changes and trends in airway management over time. Our hypothesis was that airway management has changed during the last two decades in Germany. The research questions underlying the analysis were: Which airway management procedures have been performed over the last 16 years and how has the frequency of these procedures changed over time? Is there a relationship between patient characteristics or surgical specialisation and the type of airway management performed?

Such an analysis may be influenced by confounding factors and temporal biases [3,7,8], but the size of the dataset means that it can still provide information on the frequency and trend of different airway management techniques for specific indications over a long time period and serve as a basis for future adaptation of airway management guidelines.

Materials and methods

The study was performed in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement [9]. Ethical approval for this retrospective study was deemed not required by the ethical committee due to the absence of identifiable data, as stated in a letter by the local ethical committee (Ethik-Kommission der Landesärztekammer Rheinland-Pfalz). Records from the University Medical Centre Mainz internal data acquisition and accounting system (DAQ) of every patient undergoing an operation or medical intervention with anaesthesiologic attendance between January 1, 2005, and December 31, 2020, were screened for airway evaluation and intubation grading data (Mallampati category, neck reclination, thyromental distance, Cormack-Lehane score), airway management techniques (oral intubation, nasal intubation, mask ventilation, supraglottic airway device, tracheal cannula, double lumen intubation, jet ventilation), and patient characteristics (number of patients per specialisation, sex, age, ASA status, type of surgery: elective, urgent, emergency) to generate the final data set. With the intention to report long term trends, data from the beginning of the records were evaluated. Hence, a sample size was not previously determined. Screenshots of the internal DAQ are shown in S1 and S2 Figs.

The DAQ is based on the data set for external quality control in anaesthesia on behalf of the German Society of Anaesthesiology and Intensive Care Medicine (Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin, DGAI) and the Association of German Anaesthesiologists (Bund Deutscher Anästhesisten, BDA) [10]. Datasets can be subdivided by different medical/operative specialties (general surgery; neurosurgery; traumatology; urology; gynaecology; otorhinolaryngology; ophthalmology; dental, oral, and maxillofacial surgery; cardiac surgery; thoracic surgery; orthopaedics; paediatric surgery and medical diagnostics (dermatology, psychiatry, radiology)). Mandatory data input into the DAQ is carried out directly by the responsible anaesthesiologist.

Primary outcome measurements of the study were to analyse the frequency of tracheal intubations or supraglottic airway devices. The full dataset with anonymised patient characteristics was analysed focusing on airway evaluation data (Mallampati category, neck reclination, thyromental distance, Cormack-Lehane score), different airway management techniques (oral intubation, nasal intubation, mask ventilation, supraglottic airway device, tracheal cannula, double lumen intubation, jet ventilation) as well as the use of supraglottic airway devices and fibreoptic intubation in different subspecialties and over a period of 16 years. To differentiate between first- and second-generation supraglottic airway devices, the records of the internal hospital pharmacy were screened for supraglottic airway device purchases in the analysed time. First generation supraglottic airway devices included LMA uniqueTM and flexibleTM, AMBU® AuraFlexTM, Aura-iTM, AuraOnceTM and air-Q®sp. Second generation devices included LMA SupremeTM and AMBU® AuraGAINTM.

As further outcomes, demographic patient characteristics (number of patients per specialisation, sex, age, ASA status, type of surgery) were evaluated.

Statistical analysis

Patient characteristics were summarised using absolute and relative frequencies for categorical variables and means for continuous variables. Binomial logistic regression was used to assess time trends in the proportion of patient characteristics and airway management techniques. A polynomial spline of calendar year was used to model non-monotonic time trends, otherwise a log-linear trend was assumed. Differences in time trends between patient groups were assessed using an interaction term between numerical calendar year and the patient grouping variable of interest. We report adjusted odds ratios together with 95% confidence intervals and p-values from Wald tests based on heteroscedasticity and autocorrelation-consistent standard errors to account for autocorrelation of the time series [11]. The association between the number of supraglottic airway devices as registered in internal pharmacy records and the corresponding number from the DAQ was evaluated using Poisson regression with only an intercept and log number of masks from DAQ as the offset. The relative rate and 95% confidence interval were calculated using heteroscedasticity and autocorrelation-consistent standard errors. Results of statistical tests were considered significant if the p-value was under 0.05. Data was prepared in Microsoft Excel, analyses were performed using the statistical environment R (version 4.1.2) [12].

Results

Data from 414,843 patients requiring operation or medical intervention with anaesthesiologic attendance within a period of 16 years were analysed (Table 1).

Table 1

Characteristics of patients for anaesthesia at a tertiary university hospital in Germany between 2005 and 2020 by medical/operative subspecialty, age, sex, ASA status, and priority of operation.

Values are represented as means and relative proportion (%).

Year	2005	2006	2007	2008	2009	2010	2011	2012	2013	2014	2015	2016	2017	2018	2019	2020
Patients for anaesthesia	23,864	23,103	24,499	24,620	24,748	25,294	25,670	25,279	26,652	27,076	26,464	27,970	28,428	27,975	27,054	26,147
Specialty
General surgery	2,041	1,929	2,055	2,426	2,462	2,337	2,574	2,714	2,808	2,819	2,524	2,692	2,417	2,286	2,114	2,358
Neurosurgery	2,128	1,871	1,852	1,767	2,073	2,041	2,043	1,998	1,769	1,822	1,943	2,094	2,225	2,292	2,224	2,422
Traumatology	2,891	3,001	3,174	3,027	2,994	2,955	3,141	2,715	3,424	4,279	4,106	3,941	3,933	3,858	3,579	4,148
Urology	2,772	2,739	2,926	2,727	2,842	2,815	2,832	2,828	2,784	2,785	2,621	2,760	2,823	2,898	2,775	2,681
Gynaecology	2,504	2,432	2,643	2,799	2,794	2,977	3,382	3,369	3,235	3,205	3,238	3,763	3,910	3,787	3,799	3,369
Otorhinolaryngology	3,165	3.123	3.168	3,212	3,154	3,137	3,024	2,939	2,934	2,637	2,702	2,681	2,640	2,626	2,545	1,929
Ophthalmology	1,166	1,102	1,357	1,322	1,479	1,719	1,639	1,654	2,615	2,745	2,361	2,413	2,737	2,733	2,771	2,532
Dental, oral, and maxillofacial surgery	1,366	1,268	1,364	1,339	1,401	1,356	1,411	1,384	1,448	1,366	1,363	1,439	1,356	1,404	1,401	1,287
Cardiac surgery	2,217	2,186	2,479	2,617	2,646	2,656	2,563	2,806	3,169	3,421	3,479	3,634	3,653	3,364	3,101	2,672
Medical diagnostics	368	361	398	506	537	724	900	902	1,017	1,079	1,158	1,438	1,626	1,618	1,632	1,751
Orthopaedics	1,739	1,590	1,614	1,463	1,280	1,331	1,001	886	518	23	*	*	*	*	*	*
Paediatric surgery	1,178	1,191	1,156	1,095	849	985	890	918	892	890	969	1,115	1,108	1,109	1,113	998
Thoracic surgery	329	310	313	320	237	261	270	166	39	5	*	*	*	*	*	*
Mean age (years)	44	46	46	46	46	47	47	47	47	47	47	47	48	48	48	49
Sex (male), n	12,733	12,436	13,314	13,072	13,099	13,348	13,559	13,037	13,936	14,080	13,740	14,293	14,518	14,550	13,679	13,544
Sex (male), %	53	54	54	53	53	53	53	52	53	52	52	51	52	52	51	52
ASA status
I, n	3,395	2,952	3,006	3,018	3,421	3,378	3,498	3,608	3,776	3,345	3,210	3,319	3,401	3,687	3,446	3,166
I, %	14.2	12.8	12.3	12.3	13.8	13.4	13.6	14.3	14.2	12.4	12.2	11.9	12.1	13.1	12.9	12.1
II, n	10,461	10,260	10,963	11,094	11,323	11,927	12,076	11,662	12,161	12,390	11,485	12,098	11,928	12,055	11,489	10,876
II, %	43.8	44.4	44.7	45.0	45.8	47.2	47.1	46.2	45.8	45.8	43.6	43.5	42.4	43.1	43.0	41.6
III, n	7,354	7,162	7,725	7,592	7,192	7,227	7,556	7,659	8,290	9,030	9,047	9,425	9,547	9,310	8,998	9,125
III, %	30.8	31.0	31.5	30.8	29.1	28.6	29.5	30.3	31.2	33.4	34.3	33.9	33.9	33.3	33.7	34.9
IV, n	2,564	2,629	2,702	2,794	2,701	2,593	2,411	2,246	2,215	2,139	2,463	2,837	3,099	2,719	2,631	2,859
IV, %	10.7	11.4	11.0	11.3	11.0	10.3	9.4	8.9	8.3	7.9	9.3	10.2	11.0	9.7	9.9	11.0
V, n	82	98	96	112	95	105	96	71	106	115	143	115	140	161	125	113
V, %	0.3	0.4	0.4	0.5	0.4	0.4	0.4	0.3	0.4	0.4	0.5	0.4	0.5	0.6	0.5	0.4
H, n	8	2	7	10	15	19	13	7	3	6	6	5	7	6	11	8
H, %	0.03	0.01	0.03	0.04	0.06	0.08	0.05	0.03	0.01	0.02	0.02	0.02	0.02	0.02	0.04	0.03
Priority of operation
elective, n	19,742	18,545	19,708	19,356	19,826	20,179	20,476	19,979	21,132	21,265	20,564	21,613	21,760	21,998	20,890	19,834
elective, %	82.8	80.3	80.4	78.6	80.1	80.0	80.0	79.1	80.0	78.7	78.0	77.7	77.4	78.7	78.2	75.9
urgent, n	2,672	2,887	3,038	3,137	2,742	2,725	2,814	2,903	3,079	3,362	3,248	3,381	3,246	3,144	3,328	3,752
urgent, %	11.2	12.5	12.4	12.7	11.1	10.8	11.0	11.5	11.6	12.4	12.3	12.2	11.5	11.3	12.5	14.3
emergency, n	1,450	1,671	1,753	2,127	2,180	2,345	2,360	2,371	2,340	2,398	2,542	2,805	3,116	2,796	2,482	2,561
emergency, %	6.1	7.2	7.2	8.6	8.8	9.3	9.2	9.4	8.8	8.9	9.6	10.1	11.1	10.0	9.3	9.8

*In 2015, the Orthopaedics department was merged with the Traumatology department and the Thoracic Surgery department with the Cardiac Surgery department.

The mean patient age increased from 44 years in 2005 to 49 years in 2020. The proportion of male patients decreased consistently from 53.3% to 51.8% (OR per year = 0.993, 95% CI = 0.990–0.995. The frequency of ASA status changed over time, with the frequency of ASA III patients slightly increasing and that of ASA I and ASA II patients slightly decreasing. In terms of priority of the operation, elective surgeries showed a slight downward trend over time.

To assess whether airway procedures changed over time, 340,748 airway procedures were analysed by type of procedure (Fig 1).

Fig 1

Types of airway procedures used from 2005 to 2020.

(oral intubation = red, supraglottic airway device = brown, nasal intubation = green, mask ventilation = turquoise, tracheal cannula = blue, double lumen intubation = purple, jet ventilation = black).

223,835 of these procedures (65.7%) were performed as oral intubation, 61,558 (18.1%) with supraglottic airway devices, 25,574 (7.5%) as nasal intubation, 5,382 (1.6%) with mask ventilation, 4,364 (1.3%) by tracheal cannula, 2,364 (0.7%) with a double lumen tube, and 1,915 (0.6%) by jet ventilation. For 15,756 anaesthesia patients (4.6%) the type of procedure was not evaluated. The proportion of patients anaesthetised with supraglottic airway devices showed an upward trend (overall increase of 17.0 percentage points, OR per year = 1.072, 95% CI = 1.071–1.088), while the frequency of oral intubation constantly decreased (overall decrease of 21.9 percentage points, OR per year = 0.936, 95% CI = 0.927–0.944).

In 2005, supraglottic airway devices were used in about 10% of all airway management procedures. Until 2020, this proportion steadily increased about 27%. Frequency of oral intubation decreased to about 75% in 2005 and 53% in 2020).

Fig 2 shows the OR per year for supraglottic airway devices use according to operative/medical specialty and a comparison of time trends of oral intubation and supraglottic airway devices.

Fig 2

Odds ratios per year with 95% confidence intervals for supraglottic airway device use according to operative/medical specialty.

The highest OR per year for supraglottic airway device use was observed for anaesthesia in ophthalmology, with a predicted increase of odds of 26.4% per year. When comparing oral intubation with supraglottic airway device use by operative/medical specialty, differences between the specialties were observed both in the general habits of their use and in the development over time (Fig 3).

Fig 3

Supraglottic airway device (red) use over time compared to oral intubation (turquoise) trends over time by operative/medical specialty.

For example, in neurosurgery, traumatology, and otorhinolaryngology, oral intubation was consistently preferred throughout the entire period, while in ophthalmology, a continuous switch from oral intubation to supraglottic airway device use was obviated.

Data on the type of supraglottic airway devices used for anaesthesia was obtained by analysing the records of the in-house pharmacy for supraglottic airway device purchases, as this was the only way to determine retrospectively the frequency of use for each mask type. The purchase and use of supraglottic airway devices correlated strongly (Pearson’s correlation coefficient r = 0.92, p < 0.001, CI 0.77; 0.97). Purchasing records for supraglottic airway devices were 35.2% higher on average than use of supraglottic airway devices as documented in the DAQ. The purchase of second-generation supraglottic airway devices started in 2010. When differentiating the type of supraglottic airway device used by generation, the use of first-generation supraglottic airway devices decreased, while the use of second-generation supraglottic airway devices increased over time (interaction calendar year by mask generation). (Fig 4). While second-generation devices made up about 9% of all supraglottic airway devices in 2010, 2020 they represented a proportion of 82%.

Fig 4

Purchase of first- (red) and second-generation (turquoise) supraglottic airway devices over time (records of the internal hospital pharmacy).

Mallampati categories exhibited a different trend over time. The frequency of the Mallampati I category decreased from 56.7% to 30.2% while the Mallampati II category increased from 26.6% to 43.9% over the 16. years.

Cormack-Lehane scores II, III, and IV remained stable over the 16-year time, while the frequency of Cormack-Lehane I decreased. The number of unevaluable Cormack-Lehane scores constantly increased over time.

A total of 18,614 fibreoptic intubations were performed (5.5% of all airway management procedures). Otorhinolaryngology as well as dental, oral, and maxillofacial surgery were the specialties with most frequent fibreoptic intubation use (6,873 and 6,361 fibreoptic intubations, respectively). Overall, the numbers of fibreoptic intubation use showed non-linear variations over the years (Fig 5).

Fig 5

Relative frequency of fibreoptic intubations by specialty.

(otorhinolaryngology = turquoise, dental, oral, and maxillofacial surgery = green, traumatology = purple, neurosurgery = red).

Discussion

The present study is the first large-scale analysis of longitudinal data on procedures used in periinterventional airway management over a 16-year period. This enabled us to assess long-term trends in the use of specific airway management procedures and devices. In the future, these datasets can serve as a basis for optimizing recommendations for procedures and guidelines for airway management.

The dataset of the present longitudinal-study includes 340,748 airway interventions over a 16-year period. To our knowledge, there are only few studies with a comparable large data set of airway-interventions, which, however, do not cover this vast period of time. In the United Kingdom, a national census of airway management techniques collected 114,904 data from patients undergoing general anesthesia in 309 hospitals over a 2-week period in 2008 [13]. While the dataset of the latter study represents only one point in time in 2008, the present study reflects a longitudinal development over 16 years and has collected about three times as much data. This should be taken into account when comparing these two studies. In the UK study, a supraglottic airway device was used in 56.2% of cases, followed by tracheal tube (38.4%) and facemask (5.3%) [13]. In the present study, the frequency of tracheal intubation decreased from 75.4% initially to 58.5% in 2020, while at the same time the supraglottic airway device was used in only 10.4% of patients in 2005, which increased to 27.4% in 2020. This shows a clear trend that the use of supraglottic airway devices in Germany increased over time, but even in 2020, half as many supraglottic airway devices were used at our hospital as in the UK [14] in 2008. Data from another German university hospital including 167,349 anesthetic records over a 6-year period (2005–2011) revealed a proportion of 20.6% for the use of supraglottic airway devices [14]. In comparison, our data resulted in a proportion of 13.1% between 2005 and 2011. One possible reason for the difference between data sets of the two university hospitals in Germany and the data of the UK cross-sectional study could be the more complex surgical procedures in a university setting requiring tracheal intubation. Overall, it must be assumed that the nationally and institutionally differences of supraglottic airway device use seem influenced by an emotional discussion about the “safe” airway (intubation) and the “unsafe” airway (supraglottic airway device). Regardless, any method is only as good as its use and patient safety should always be paramount.

Woodall and Cook´s data showed also that only 10% of supraglottic airway devices used in 2008 were second-generation [13]. In the present analysis, purchase of second-generation supraglottic airway devices started in 2010 and since 2015, more second-generation than first-generation supraglottic airway devices have been applied. The replacement of first-generation with second-generation masks is a desirable trend, as noted by Cook et al. because second-generation masks are superior in regards to their efficacy and safety, particularly for expanded indications [15]. Second-generation supraglottic airway devices are characterised by reduced oropharyngeal leak and the possibility of inserting a gastric tube, which increases patient safety. The present study was able to confirm that second-generation supraglottic airway devices have gained acceptance over time due to their clear advantages. The observed trend of replacing oral intubation with supraglottic airway devices is particularly evident in operative/medical specialities that benefit from the expanded indications of second-generation masks. The improved seal and the identification of possible malpositions have led to an increased use in areas with limited access to the airway, such as in ophthalmology or medical diagnostics (e.g., radiology).

Surprisingly, the frequency of Mallampati categories I and II have changed over time. One possible reason for the decrease in the Mallampati category I in favour of Mallampati category II could be that anaesthesiologists are less afraid of managing a difficult airway due to the increased availability of videolaryngoscopy and supraglottic airway devices compared to the past. This made the preoperative assessment of a difficult airway less relevant, which may have led to less familiarity with the score and, in case of doubt, to an overestimation of the Mallampati category. This assumption was confirmed by a survey of European anaesthesiologists on theoretical knowledge and practical skills regarding the Mallampati category. The survey revealed large knowledge gaps among anaesthetists, which were attributed to the lack of interest or insufficient training in airway assessment [16]. Therefore, in future, anaesthesiologists’ training should again place more emphasis on carefully communicating the high value of preoperative assessment of a potentially difficult airway.

Another important score for airway management also changed over time. Intubation conditions were increasingly rarely rated as very good in terms of a Cormack-Lehane score I. At the same time, the frequency of the Cormack-Lehane scores II-IV remained unchanged. One explanation could be the simultaneous increase in the frequency of “not evaluable” Cormack-Lehane scores. This could be due to the fact that over time, supraglottic airway devices have been increasingly used, and since this airway device does not allow a view of the glottis, the Cormack-Lehane score could not be determined. At the same time, videolaryngoscopy was increasingly used in our department. Although the current German guidelines recommend the evaluation of the Cormack-Lehane score also for videolaryngoscopy [17] due to its simplicity and lack of an accepted alternative, many anaesthetists are under the impression that the Cormack-Lehane score is not suitable for videolaryngoscopy. This could be another reason for the prevalence of the “not evaluable” score. In the future, more emphasis should be placed on an adoption of a more suitable alternative of the Cormack-Lehane score during videolaryngoscopy (e.g., digital videolaryngoscopic images within health records) to ensure patient safety by providing reliable a clearly understandable documentation of a potentially severe airway [18].

Compared to the other specialities, fibreoptic intubation has been used much more frequently in otorhinolaryngology and maxillofacial surgery. Due to the underlying pathologies, patients in the otorhinolaryngology and maxillofacial surgery are more likely to have a difficult airway. Thus, it was observed that in maxillofacial surgery, the use of fibreoptic intubation doubled between the years 2005 and 2010 and remained relatively stable thereafter. This can be attributed to fluctuating numbers of major cancer surgery in the department.

Although one might assume that videolaryngoscopy would replace fibreoptic intubation over the years, surprisingly no decline in fibreoptic intubation was observed [19]. This could possibly be due to the fact that fibreoptic intubation is considered an important procedure in our hospital. Every anaesthetist must be well trained for fibreoptic intubation, as according to guidelines, videolaryngoscopy is not an adequate substitute for the management of an anticipated difficult airway [20,21]. Therefore, the indication for fibreoptic intubation is generously given in our clinic to ensure adequate training, which is reflected in the increase of fibreoptic intubation use over time. This is in accordance with the recent Difficult Airway Society recommendations for awake tracheal intubation in adults [22].

We acknowledge that our data analysis has certain limitations. First, it does not allow for correlation of the type of airway management procedure with complications or the outcome of the patient, as this information was not documented in the DAQ. It would be interesting to align trends with patient outcome to allow for an assessment of the efficacy of airway management techniques and devices. Second, we have no data on videolaryngoscopy, which could help to conclusively evaluate the observed changes in fibreoptic intubation and the Cormack-Lehane scores. Last, although a large number of patients was evaluated, they were all treated in a single centre and hence the trends may differ in other clinics according to local preferences. University Medical Centre Mainz hosts a large department of oral and maxillofacial surgery, as well as a large department of otorhinolaryngology. We therefore treat an exceptional number of patients with a difficult airway. Patients with large tumors and abscesses in the airway and patients with rare syndromal and anatomical peculiarities belong to our complex patient population. Due to this condition, the results of this analysis cannot be transferred to other health care institutions. Consequently, external validity is therefore limited.

Concerning the assessment of data quality, it can be stated that objectively evaluated data like patient demographics and frequency of airway management techniques are unlikely to contain misclassification errors whereas evaluation of patient characteristics has limited reliability, and thus has potentially higher probability of misclassification. In particular data extraction procedures from the DAQ were automated to avoid errors from manual repetitive tasks.

In summary, a retrospective analysis from our in-house data acquisition revealed the pattern and changes in airway management over the last 16 years in a German university hospital. During this period, 340,748 documented airway procedures were performed, with oral intubation being the most frequent technique, followed by the use of supraglottic airway devices and fibreoptic intubations. Of note, there was a significant upward trend in the use of supraglottic airway devices, with an increase in the use of second-generation masks due to their improved characteristics compared to first-generation masks, while a decrease in oral intubations was observed.

Guidelines are intended to ensure a high degree of patient safety and at the same time recommend a corridor of action for the treating anesthesiologist. It is useful and necessary to adapt the respective guidelines to one’s own everyday life and to the existing circumstances. The clinical (regional or local) context should be considered an important factor for enhancing adherence to the recommendations by physicians and health systems [23]. Developing and updating practice-based guidelines to improve airway management and patient safety requires identification of changes and trends resulting from such retrospective, long-term data evaluations, but should ideally be correlated with clinical outcomes in future studies.

The establishment of an international registry with data on current airway management practice and detailed description of associated serious complications would be a milestone in airway management.

Screenshot of the internal data acquisition system (DAQ) showing patient and airway evaluation.

Purple boxes are mandatory fields. English translation of relevant text elements (red box): Hirntod = brain death, Eingriffsart = type of surgery, Wahleingriff = elective, dringlicher Eingriff = urgent, Noteingriff = emergency, Kopfreklination = neck reclination, unauffällig = normal, fraglich = questionable, pathologisch = pathological, nicht beurteilbar = not evaluated, nicht untersucht = not analysed, Kinn/Hals = thyromental distance.

(GIF)

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Screenshot of the internal data acquisition system (DAQ) showing anaesthesia technique, administered medication, and utilised airway management technique.

English translation of relevant text elements (red box): Luftweg = airway management technique.

(GIF)

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(CSV)

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(CSV)

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(CSV)

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(CSV)

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30 May 2022

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Marcus Tolentino Silva

Academic Editor

PLOS ONE

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Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Peer review PONE

Big data: Airway management at a university hospital over 16 years; a retrospective analysis

In the age of ever-increasing knowledge regarding airway management, to know details and trends in time about the procedures, techniques and uses of the approaches remains very useful. I appreciate the opportunity to carefully read and comment regarding the submission “Big data: Airway management at a university hospital over 16 years; a retrospective analysis”. The idea and the availability of data to examining the trends over time in such a big number of procedures is commendable and with major clinical application.

Major comments,

• Most analytic goals for studies can be viewed as either seeking evidence of causality or prediction. From my early view, I feel you really present a descriptive analysis, and this is wonderful. I really congratulate about that. Many people think if they are not doing exploratory analysis o some related are not doing good science and that is a big mistake (https://doi.org/10.1038/s41416-020-1019-z). Research studies that focus on describing a population of interest are essential building blocks for both causal and predictive frameworks, and do not typically require control for additional variables. To understand the purpose of a study (i.e., descriptive, causal, or predictive), it is vital that the goals of the research be clearly explained. Please consider adjusting your purposes section of the abstract to become it more transparent and clearer (see below).

• Please, do not emphasize in the whole text any analysis on the basis of confounding. Here, I can see a great use of descriptive epidemiology beyond any causal purpose.

Minor comments per section,

Abstract

• I find the abstract quite difficult to understand. First, the purpose does not clarify in detail the aims of this study limiting itself to the need of data in this area. Please, consider clarifying the aims of this study at the end of the first section: “purpose”.

• Let’s consider adding to the methods section if you are including only adults, children, pregnant patients, etc.

• In the results section, please avoid the use of only significance testing during reporting of results. Quote “Over time, second generation laryngeal masks were used more frequently than first-generation laryngeal masks (p < 0.001)” can be adjusted by adding the degree of reduction over time, or at least over two extreme years.

• The conclusion seems to be a repetition of the results. Please conclude by following your results, perhaps regarding the trends directly and the reduction on the use of certain techniques over time.

Introduction

• It is clear the aims of your study after reading the full introduction.

Methods

• It is quite impressive that in such amount of data you do not have missing values. Methods section describes very well the process of data collection from the system, but it does not mention at all any relevant information for potential information bias from that system, how did you address that? is there any potential variable to be missed or at least biased?

• Following the previous comment, STROBE request information about how missing data or potential biases were addressed. It is quite relevant to provide information about to enhance completeness of you report. Please add relevant information.

• Results section mention “For 15,756 anaesthesia patients (4.6%) the type of procedure was not evaluated.”. Please, would you clarify why? Are those patients considered as missing values from the analysis?

• I may understand you used all data from your collection system. Anyway, it is relevant ot provide information to reader about sample size. It was not calculated so that should be stated and mentioned. Explain how the study size was arrived at?

Results

• Study cohort and characteristics. Always it is a good idea to provide a Flowchart regarding data sources and inclusion/exclusion criteria used. Indeed, completeness checklist includes a flowchart diagram as initial part of results section. Please, consider adding that flowchart of patient selection and inclusion. Report numbers of individuals at each stage of study—eg. numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analyzed

• Figures 1-6 are very well presented and attractive. Please add all relevant information to each Figure to the reader, including colors.

Discussion

• While I agree with this point “To our knowledge, there are only few studies with a comparable large data set of …”, I would like to add also this fact reduces external validity of your results. I do not see any section of the discussion taking about the type of patients in terms of complexity you receive in your center. Are those patients reflecting the common clinical practice in other health care systems? In what extent? Please, expand about that and discuss the generalizability (external validity) of the study results

• Discussion is very well conducted and interesting enough. To me, as a reader it was very nice to explore.

• You mention clear limitations. However, measurement error was not included explicitly. Quite complex in retrospective datasets. Any potential to misclassify exposure, outcome or included covariates. Any consideration about steps taken to ensure accurate measurement (double extraction, double check). Thank you for expanding on these details.

• You mention several times in the text the importance of this data to clinical practice guidelines. Quote “…and serve as a basis for future adaptation of airway management guidelines.”. Do your consider people in your hospital or perhaps country is following current guidelines in airway management and that is reflected in your data? I would like to suggest citing and mention that current guidelines in airway management seems to be well developed but poorly able to be adapted to clinical practice (CPGs show low applicability of their recommendations to real clinical practice) (https://doi.org/10.1097/eja.0000000000001195 ). Please, could you expand on this topic perhaps a final paragraph.

Reviewer #2: This is an interesting well written manuscript that in my opinion is adequate for publication after minor revision.

I only have two comments:

In limitations it should be mentioned that data comes from single hospital, so the external validity is limited.

Study period goes until just before the COVID 19 pandemic started. Some comment on the effect of the pandemic on the results could be interesting

Reviewer #3: I would like to commend the authors for looking at 16 years of data and in excess of 340,000 airway management procedures. This is big data.

Specific comments:

Page 5 line 50-64: This portion may not be immediately relevant to the study and can be shortened or summarized.

Page 7 line 93: Cormack and Lehane grading may not be airway evaluation data but rather intubation grading data.

Page 10 line 150: Data from 414,843 patients were analyzed but only 340748 patients were included. Could the authors explain in more detail why this was so?

General comments about the intrinsic limitations of the study as presented by the authors:

1. 16 years ago airway management may be different. Use of 2nd generation supraglottic airway devices and video laryngoscopes more widespread in the last decade. I wonder if limiting the period to 10 years may be more relevant to practicing Anaesthesiologists.

2. Use of laryngeal mask only 27% in 2020. That figure seems a little low and is not in keeping with international data and my own experience. It should be closer to 50%, of course depending on the type of cases that are performed.

3. One main finding is that laryngeal mask use has increased over time. This has been very well reported in the literature. It would be interesting to know if the use of video laryngoscopes have likewise increased over time.

4. A more interesting slant may also be a subgroup analysis of the use of fibreoptic intubation, e.g. indications, complications, failure rate, etc.

5. There are generally too many figures. These should be reduced.

6. Conclusions by the author are not novel and many (if not all) of these have been espoused in other prior publications or are intuitive.

Minor comment:

1. Consider using the term supraglottic airway device instead of laryngeal mask (which is a brand name). Consider detailing the types of supraglottic airway devices used during the 16 year period (e.g. Ambu AuraGain, LMA Protector, Igel, etc)

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6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

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Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Jose Andres Calvache

Reviewer #2: No

Reviewer #3: No

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Submitted filename: Peer review PONE.docx

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19 Jul 2022

Please find the response in the uploaded file "Response to Reviewers"

Submitted filename: Response to Reviewers.docx

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11 Aug 2022

Big data: Airway management at a university hospital over 16 years; a retrospective analysis

PONE-D-22-11287R1

Dear Dr. Pirlich,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Marcus Tolentino Silva

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Partly

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: I Don't Know

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Thank you for addressing all comments I made. This initiative is a good approach to big data information in anesthesiology. Congrats for this great manuscript !

Reviewer #2: The authors have answered all the comments to the reviewers. So in my oppinion the manuscript is ready for publication

Reviewer #3: I would like to thank the authors for responding to the comments. The revised manuscript has addressed some of the inaccuracies from the original manuscript and highlighted relevant limitations.

This is a study analyzing more than a decade of airway management experience in a tertiary hospital in Europe.

The findings and final conclusion, however, are not novel. It points towards something which is well known from the existing literature, vis-a-vis the increase in use of supraglottic airway devices and decrease in tracheal intubations. This is especially so with the proliferation of second generation supraglottic airway devices.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Jose A. Calvache

Reviewer #2: No

Reviewer #3: No

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12 Sep 2022

PONE-D-22-11287R1

Big data: Airway management at a university hospital over 16 years; a retrospective analysis

Dear Dr. Pirlich:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Marcus Tolentino Silva

Academic Editor

PLOS ONE