European Journal of Cardiovascular Medicine

Airway management is the cornerstone of resuscitation and is one of the defining skills for an Emergency Physician. Most patients who require emergency intubation on arrival to the ED pose great challenges as they are not pre-evaluated ^1,2,3 . An important step in Intubation is pre-oxygenation, however, there is an apneic period following administration of paralytic agent during which there is a phase where oxygenation is not given. This “Apneic period” during intubation, though brief; puts patients at risk for dysrhythmias, hemodynamic decompensation, hypoxic brain injury and death ⁴.

Methods were developed just to decrease the morbidity and mortality associated with this brief yet life-threatening moment. These techniques include insufflation of O2 using a nasal prongs, nasopharyngeal catheter, intratracheal catheter, and high-flow transnasal humidified O2 ^5,6 .

Studies were conducted using these various techniques and proven to be beneficial. Studies comparing nasal prongs versus nasopharyngeal catheters have yielded results favoring nasopharyngeal catheters ⁷.

Current research on endotracheal catheters and laryngoscopes showed that the use of apneic oxygenation resulted in a significantly lower incidence of desaturation and smaller declines in oxygen saturation ⁸. However, research into these advanced apneic oxygenation techniques have increased costs involved and may be difficult to carry out currently in our Indian setting.

Most of the research done on the basic apneic oxygenation techniques in India is in controlled environments and studies in the Emergency Department and pre-hospital settings are scant ⁹. In this research work, we aim to study the effects of apneic oxygenation using the nasopharyngeal catheter in comparison to the conventional method in which there is no oxygenation during this period.

There are very few Indian studies regarding apneic oxygenation and among the existing studies most of them are done in controlled and closed environments like the operating rooms and intensive care units.

Aims & Objectives:

Aim: To compare the effectiveness of nasopharyngeal oxygenation versus conventional method during the apneic phase of endotracheal intubation

Objectives:

1. To compare the incidence of de-oxygenation during the apneic period between both techniques
2. To compare the extent of de-oxygenation during the apneic period between both techniques
3. To compare the complications encountered between the two groups.
4. To study the overall indication for endotracheal intubation in critically ill patients presenting to emergency department

This was a Single blinded Randomized control study conducted in the department of Emergency Medicine, Subbaiah Institute of Medical Sciences and Research Centre, Shivamogga during a period of one year from November 2024 to October 2025. Inclusion criteria: All patients on whom rapid sequence intubation is performed in our Emergency department were included in the study. Exclusion criteria: Age < 18 years Patients with nasal bone fractures, maxillary and mandidular fractures Head Injury Data collection: Study is initiated after the approval from ethical committee. Once the patient is received and fits into inclusion criteria, he/she were randomized using computer generated randomization to either study or control group. Control group: In this group, the current standard process of RSI is practiced. Study group: In this group, nasopharyngeal tube was inserted. The steps include Informed consent. Preoxygenation with 100% oxygen is administered for 3 minutes which ensures adequate oxygen reservoir. Administration of a pretreatment induction agent by IV is initiated. Once the patient starts to get sedated, a 6-8 Fr infant feeding tube is inserted into the nares. Catheter depth is determined by measuring from the base of the nose to the tragus. Once the adequate depth is reached, the tubing is secured to the skin with adhesive pads. The catheter is connected to Oxygen tubing and flow rate is set at 5L/min. Once the O2 flow is initiated, intubating dose of a neuromuscular blocking agent is administered. The remaining part of the processes follow the same steps as Rapid Sequence Intubation. Sample size: As per the study done in USA, Eight studies (1953 patients) revealed the absolute risk of clinically significant hypoxemia was 27.6% in the usual care group and 19.1% in the apneic oxygenation group thus inferring that 30% of the patients who underwent conventional intubation desaturated 10; we are expecting 30% difference (in study and conventional groups), power 80% and with 95% confidence interval the minimum required sample size is 38 in each group. “nMaster” was used for the sample size calculation. Sample size Formula n={Z1-α/2*(2*p ̅*(1-p ̅))1/2+Z1-β*(P1*(1-P1)+P2*(1-P2))1/2}2/(P1-P2)2 where, P ̅ ={P1+P2}/2 P1 : Proportion in the first group P2 :Proportion in the second group α :Significance level 1-β :Power of the study Calculation Sample size, n={1.96*(2*0.65*(1-0.65))1/2+0.84*(0.80*(1-0.80)+0.50*(1-0.50))1/2}2/(0.80-0.50)2 =38/group Statistical method: Statistical analysis was performed by using the software SPSS 22.0 version. Descriptive statistics were reported as mean ± standard deviation, median [interquartile range (IQR)] for continuous variables and for categorical variables as percentages or frequencies. The normality of quantitative data was checked by measures of Kolmogorov-Smirnov tests of normality. Independent t-test was used to find the significant difference in the means of two groups. To find the association between categorical outcomes chi-square test or Fishers Exact test or Chi square test was used. p value <0.05 was considered as statistically significant. Statistical analysis[11-14]: Data was entered into Microsoft excel data sheet and was analyzed using SPSS version 22 (IBM SPSS Statistics, Somers NY, USA) software. Categorical data was represented in the form of Frequencies and proportions. Chi-square test was used as test of significance for qualitative data. Continuous data was represented as mean and standard deviation. Independent t test was used as test of significance to identify the mean difference between two quantitative variables. Paired t test is the test of significance for paired data. MS Excel and MS word was used to obtain various types of graphs such as bar diagram, Pie diagram. p value (Probability that the result is true) of <0.05 was considered as statistically significant after assuming all the rules of statistical tests.

Data of total of 76 patients requiring emergency endotracheal intubations attending Department of Emergency Medicine were analysed and final results and observations are tabulated as below.

Table 1: Age and gender wise Distribution of patients among two groups

In Group A, majority of subjects were in the age group <30 years (23.68%) and in Group B, majority of subjects were in the age group <30 years (28.95%). There was no significant difference in age distribution between two groups.

In Group A, 65.79% were males and 34.21% were females and in Group B, 68.42% were males and 31.58% were females. There was no significant difference in Gender between two group

Table 3: Overall Indication for Emergency Intubation.

Table 4: Cormack Lehane Grade Distribution of patients among two groups

Table 2: Overall indications / Diagnosis for intubation

In Group A, 84.21% had Grade 1, 7.89% had Grade 2A, 5.26% had Grade 2B and 2.63% had Grade 3. In Group B, 92.11% had Grade 1, 5.26% had Grade 2A, 2.63% had Grade 2B and 0% had Grade 3. There was no significant difference in Cormack Lehane Grade between two groups.

Figure 1 : Bar Diagram for Cormack Lehane Grade Distribution of patients among two groups

Table 5: Mean SBP, DBP, HR and RR comparison distribution of patients among two groups

Mean SBP in Group A was 129.74 ± 38.80 mmHg and in Group B, was 120.00 ± 40.80. There was no significant difference in SBP between two groups. Mean DBP in Group A was 78.95 ± 16.89 mmHg and in Group B, was 75.79 ±

21.26. There was no significant difference in DBP between two groups

Mean HR in Group A was 101.45 ± 25.22 bpm and in Group B, was 102.16 ± 23.03 bpm. There was no significant difference in HR between two groups. Mean RR in Group A was 23.92 ± 9.66 cpm and in Group B, was 24.21 ± 13.07 cpm. There was no significant difference in RR between two groups

Table 6: Mean Comparison of SPO2 and Apneic period (Deoxygenation) SPO2 within groups.

In Group A, on arrival SpO2 was 91.32 ± 6.33 % and at de-oxygenation was 95.92 ± 4.01. In Group B, on arrival SpO2 was 91.00 ± 5.78 % and at de oxygenation was 97.11 ± 3.25. There was no significant difference in mean on arrival SPO2 and De-oxygenation SpO2 between two groups. With in Group A and Group B there was significant increase in De-Oxygenation SPO2 compared to on arrival SpO2.

Figure 2: Bar Diagram for Mean SPO2 and De-Oxygenation SPO2 comparison distribution of patients among two groups.

Table 7: Incidence of Desaturation comparison between two groups

χ 2 =0.835, df =1, p =0.361

In Group A, 21.1% had SpO2 <93% at De-oxygenation and 78.9% had SpO2 >93%. In Group B, 13.2% had SpO2 <93% at De-oxygenation and 86.8% had SpO2 >93%. There was no significant difference in extent of Desaturation between two groups.

Table 8: Extent of Change in SpO2 (Desaturation) comparison between two groups

In Group A, percentage change in SpO2 at Deoxygenation was 5.42 ± 7.21% and in Group B was 7.03 ± 6.24 compared to SpO2 on arrival. There was no significant difference in extent of Change in SpO2 between two groups. 

Table 9: Complication distribution of patients among two groups

In Group A, 2.63% had cardiac arrest and in Group B, 2.63% had Subcutaneous Emphysema. There was no significant difference in complications between two groups.

Hypoxia is one of the most common and serious risks of tracheal intubation. There is a growing body of evidence that apneic oxygenation has the potential to minimize the risk of hypoxia in patients requiring intubation. The use of apneic oxygenation during intubation appears to be associated with increased peri-intubation oxygen saturation and first-pass success rates, as well as decreased incidence of hypoxemia in patients intubated in the ED or ICU15.

This current study is a single blinded randomised control study done in Department of Emergency medicine.

We enrolled total of 76 patients requiring emergent intubation to either standard preoxygenation using a BVM (Group A, 38 patients) or preoxygenation with BMV and apneic oxygenation with an infant feeding tube (Group B, 38 patients). In Group A preoxygenation was performed over a 3-min period with BVM set at 15 L/min oxygen flow, held in place to ensure appropriate mask seal. In group B preoxygenation was performed by routine BMV with 15L/min O2 flow along with apneic oxygenation using a infant feeding tube of 6-8Fr with 5L/min of oxygen.

After preoxygenation, patients underwent a rapid sequence induction, the specifics of which were left to the discretion of the treating clinician. In patients randomized to group B infant feeding tube was left on throughout the intubation process in an attempt to achieve some degree of apneic oxygenation.

On further comparison, majority of the patients in both groups were of age less than 30 years (i.e. 23.68% in group A and 28.95% in group B) and rest of the patients’ age were as quoted above, and this age distribution was statistically not significant[TAB & FIG 1] . In the study done by Wimalasena Y , et al, the median age group of patients in the study was 46 years. In study done by Alexander J, et al, at Barts and the London School of Anaesthesia, the mean age groups of patients varied from 56 to 60 years with underlying co-morbidities. In the present study 23.69% and 31.58% of patients in group A and group B respectively belonged to age group of 40-60 years which were similar to the above mentioned studies16,17.

On further analysis in group A, 65.79% were males and 34.21% were females and in group B, 68.42% were males and 31.58% were females. There was no significant difference in Gender distribution between two groups[TAB & FIG 2] .In a study done by Caputo N, et al, 58% in usual care and 59% in AO groups were male patients and rest of the patients were females. In Semler, et al, study 58.4% in usual care and 63% in AO groups were males and remainder being females18,19. Similarly in our study we found predominantly male patients compared to females.

On analyzing the overall indication for emergency endotracheal intubation we found that, 24.9% of the patients had respiratory cause (CAP, ARDS, COPD/Asthma exacerbation, pulmonary embolism, pneumothorax), 22.6% had neurological cause (CVA, CVT, status epilepticus), 13% had multi organ dysfunction syndrome (AKI, septic shock, metabolic acidosis, encephalopathy), 7.8% had renal issues (CKD with acute pulmonary edema) and 31.7% had other causes such as trauma, metabolic derangements, poisoning, hanging, snake bite etc.

 In a study by Alexander J, et al, at Barts and the London School of Anaesthesia, among 71 patients included in the study, 26.7% (19/71) had respiratory cause, 12.6% (9/71) had neurological cause as an indication for emergency intubation17. In Caputo N, et al, study the ENDAO trial involving 206 patients, overall 57.7% (119/206) patients had respiratory cause, 11.6% (24/206) had traumatic, 7.2%(15/206) had neurological and 17.4% (36/206)had other causes as indication for emergency intubation18. In another study by Semler, Janz, Lentz, et al, Apneic Oxygenation for Emergent Intubation, among 196 patients 55%-57% of the patients had respiratory cause (hypoxia, hypercarbia) and 18%-21% patients had neurological (encephalopathy, altered mental status) cause as indication for emergency intubation19.

Further comparing the Cormack-Lehane (C-L) grading, in group A, 84.21% had Grade 1, 7.89% had Grade 2A, 5.26% had Grade 2B and 2.63% had Grade 3. In Group B, 92.11% had Grade 1, 5.26% had Grade 2A, 2.63% had Grade 2B and 0% had Grade 3. There was no significant difference in C-L Grade between two groups. In a study by Alexander J, et al, The C-L grade ranged from 1 to 4 (grade 1, 59%; grade 2, 27%; grade 3, 13%; grade 4, 1%). In Caputo N, et al, the mean C-L grade was 1.41 there by concluding that majority of the study patients had lower C-L grading17,18.

In the present study, the BP variations were compared and the Mean SBP and DBP in Group A were 129.74 ± 38.80 mmHg and 78.95 ± 16.89 mmHg and in group B were 120.00 ± 40.80 mmHg and 75.79 ± 21.26 mmHg respectively (MAP 87-95 mmHg). There was no significant difference and drop in SBP and DBP between two groups. In Semler MV, et al, study patients overall blood pressures varied between a MAP of 57-80mmHg including AO and usual care group with very few patients requiring ionotropic support19.

On further comparison of mean+SD SpO2 between two groups, patients in group A, had prior preoxygenation SpO2 of 91.32 ± 6.33 % and in group B had, 91.00 ± 5.78 %. The mean SpO2 at apneic period and first look were 95.92 ± 4.01% in group A. and 97.11 ± 3.25% in group B. There was no significant difference in mean on arrival (prior preoxygenation) SpO2 and deoxygenation (apneic period and first look) SpO2 between two groups (p=0.162). With in Group A and Group B there was significant increase in apneic period and first look SpO2 compared to on SpO2 on arrival. The study by Caputo N, et al, also had a mean SpO2 92% prior preoxygenation in both groups and a mean SpO2 of 98% at apneic period and at first look18 which were comparable with our study.

In the present study we had the primary objective of comparing the incidence, extent of deoxygenation and complications between the two groups during apneic period. We found that In Group A, 21.1% (8/38) had SpO2 <93% and 78.9% (30/38) had SpO2 >93%. In Group B, 13.2% (5/38) had SpO2 <93% and 86.8% (33/38) had SpO2 >93%. There was no significant difference in incidence and extent of desaturation between two groups, however more number of patients in group B had a SpO2 levels >93% and less desaturation which are clinically relevant.

In The ENDAO Trial (Emergency Department use of Apneic Oxygenation Versus Usual Care During Rapid Sequence Intubation: a randomized controlled trial), 206 patients requiring emergency intubations were allocated to receive either apneic oxygenation (n = 100) or usual care (n = 100) by predetermined randomization in a 1:1 ratio. The study concluded that there was no difference in lowest mean oxygen saturation between the two groups (92, 95% confidence interval [CI] = 91 to 93 in AO vs. 93, 95% CI = 92 to 94 in UC; p = 0.11) and application of AO during RSI did not prevent desaturation of patients in that study population18.

In the FELLOW Trial (Facilitating EndotracheaL Intubation by Laryngoscopy technique and apneic Oxygenation Within the intensive care unit) a randomized, open-label, pragmatic trial in which 150 adults undergoing endotracheal intubation were randomized to apneic oxygenation or usual care groups. The primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after completion of endotracheal intubation. The results showed no difference between apneic oxygenation and usual care in incidence of oxygen saturation less than 90% (44.7 vs. 47.2%;P = 0.87), oxygen saturation less than 80% (15.8 vs. 25.0%; P = 0.22),or decrease in oxygen saturation greater than 3% (53.9 vs. 55.6%;P = 0.87 ) and concluded that Apneic oxygenation does not seem to increase lowest arterial oxygen saturation during endotracheal intubation of critically ill patients compared with usual care. These findings do not support routine use of apneic oxygenation during endotracheal intubation of critically ill adults19.

In a study by Guitton et al from April 2016 to June 2017 the authors reported no significant difference in their primary outcome, the median lowest SpO2 during intubation, 100% vs 99% (P=0.30), in the HFNC and BVM groups respectively20.

Eight studies (1953 patients) in USA revealed the absolute risk of clinically significant hypoxemia was 27.6% in the usual care group and 19.1% in the apneic oxygenation group. Apneic oxygenation reduced the relative risk of hypoxemia by 30%10.

The use of apneic oxygenation has been reported in four small randomized trials in the operating room and two before-after studies of emergent intubation. Miguel-Montanes and co-workers observed higher oxygen saturation during intubation after their  ICU switched from apneic oxygenation at 6 L/min to 60 L/min and Wimalasena and co-workers reported a 6% decrease in the incidence of desaturation after their helicopter emergency medical service adopted apneic oxygenation at 15 L/min by nasal cannula 16,21.

Seventeen studies including 2422 patients in Australia till November 2016 revealed a significant reduction in the incidence of desaturation[<90%] and critical desaturation [<80%] with implication of apneic oxygenation49. Our trial showed no difference between apneic oxygenation  and  usual care which were in contrast to these studies  and  the  potential explanations  would  be  these  studies  were “before-after” designs  in  which  other  changes over time may have confounded the perceived impact of apneic  oxygenation and may have predisposed  to observer  bias. patients intubated primarily for traumatic, hemodynamic, or  neurologic  conditions,  most patients in our study were intubated for respiratory failure16,21.

 On comparing further, 2.63% patients in group A and Group B, had cardiac arrest and subcutaneous emphysema as a complication during endotracheal intubation respectively. There was no significant difference in complications between two groups.

However patient in group A who had cardiac arrest had a diagnosis of massive pulmonary embolism which probably was the cause for cardiac arrest. In group B patient had a blunt chest injury and had a pneumothorax that worsened to subcutaneous emphysema post positive pressure ventilation. Hence the above complications may not be directly attributable to the procedure of endotracheal intubation or apneic oxygenation.

On comparing the effectiveness of apneic oxygenation versus conventional method during the apneic phase of endotracheal intubation, the mean SpO2 at apneic period was 95.92 ± 4.01% in conventional group (group A) and 97.11 ± 3.25% in apneic oxygenation group (group B). There was no significant difference in mean SpO2 between two groups of (p=0.162). The incidence and extent of deoxygenation during the apneic period in Group A was 21.1% (8/38) and in Group B it was 13.2% (5/38) to an SpO2 of <93%. There was no significant difference in the incidence and extent of deoxygenation between two groups (p=0.361). On comparing the complications, 2.63% patients in group A and 2.63% in Group B, had cardiac arrest and subcutaneous emphysema respectively. There was no significant difference in complication between the two groups (p= 0.368).However these complications cannot be directly attributed to the procedure of endotracheal intubation or apneic oxygenation. Overall, 24.9% of the patients had respiratory cause, 22.6% had neurological cause, 13% had multi organ dysfunction syndrome, 7.8% had renal cause and 31.7% had other causes (trauma, metabolic derangements, poisoning, hanging, snake bite) as the indication for emergency endotracheal intubation. LIMITATIONS • Study was conducted in one Emergency Department may limit generalizability. • High compliance with preoxygenation, patient positioning, and equipment preparation best practices may have reduced the potential additive impact of apneic oxygenation.

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