Esophageal pressure monitoring for airway management during catheter ablation of atrial fibrillation.

BACKGROUND: Respiratory management during catheter ablation of atrial fibrillation (AF) is important for the efficacy and safety of the procedure. Obstructive apnea due to an upper airway obstruction might cause serious complications including air embolisms and cardiac tamponade. However, real time monitoring of upper airway obstructions during catheter ablation has not been established. The purpose of the present study was to evaluate esophageal pressure monitoring for respiratory management during catheter ablation of AF. METHODS AND
RESULTS: Twenty-four consecutive patients (20 men and 4 women; mean age, 61 ± 13 years) with AF who underwent esophageal pressure monitoring during catheter ablation of AF were retrospectively analyzed. The patients were divided into 2 groups. One was the obstructive apnea (OA) group (n = 17), which required airway management tools including nasal airways and/or non-invasive positive airway pressure (NPPV) and the other was the control group (n = 7), which did not require airway management. Esophageal pressure measurements were obtained in all patients, and the OA group exhibited a substantial negative esophageal pressure as compared to the control group (-41.48 ± 19.58 vs. -12.42 ± 5.77 mmHg, p < 0.001). Airway management in the OA group immediately improved the negative esophageal pressure and returned to a normal range (-41.48 ± 19.58 vs. -16 ± 8.1 mmHg, 0 < 0.001) along with a recovery from desaturation.
CONCLUSIONS: Esophageal pressure monitoring was a simple and effective method for the evaluation and management of obstructive apnea during AF catheter ablation.

Introduction

Atrial fibrillation (AF) is one of the most common arrhythmias, and the prevalence of AF has been increasing for decades [1]. Catheter ablation of AF has been shown to be beneficial in patients not only refractory to pharmacological treatment,[2] but also with heart failure.[3] Recently, the number of catheter ablation procedures for AF has been increasing in Japan. Although, the efficacy and safety of the ablation procedure for AF has been improved by recent advancements in 3-dimensional mapping systems and catheter technologies with contact force and balloon ablation systems,[4] the incidence of complications related to the catheter procedures is not rare even in high-volume centers [5]. Respiratory management for obstructive apnea (OA) during catheter ablation is important to prevent serious complications associated with the procedure including cardiac tamponade and air embolisms. The J-CARAF study revealed that 38.9% of ablation cases were performed with deep sedation, which might cause OA requiring airway management.[6] General anesthesia by an anesthesiologist could establish an optimal respiratory management for catheter ablation, however, the majority of AF catheter ablation cases are performed with moderate or deep conscious sedation.[6] Although a nasal airway and/or non-invasive positive airway pressure ventilation (NPPV) are useful for the management of an upper airway obstruction due to deep conscious sedation,[7], [8] insufficient airway management might cause a deep negative intra-thoracic pressure associated with an upper airway obstruction. Therefore, it would be useful if we could measure the real-time intra-thoracic pressure. However, real time monitoring of an upper airway obstruction during catheter ablation has not been established. In the present study, we developed a novel esophageal pressure monitoring system in order to evaluate the real-time esophageal pressure indicating the intra-thoracic pressure during catheter ablation of AF.

Methods

Study population

Twenty-four consecutive patients (20 men and 4 women; mean age, 61 ± 13 years) with AF who underwent esophageal pressure monitoring during radiofrequency catheter ablation between April 2015 and September 2015 at Nippon Medical School Hospital were retrospectively analyzed. The patients were divided into 2 groups. One was the OA group, which required airway management tools including nasal airways and/or NPPV and the other one was a control group which did not require airway management. This study was approved by the institutional ethics committee at Nippon Medical School Hospital.

Esophageal pressure monitoring system

Esophageal pressure monitoring was performed in all patients. The esophageal pressure was measured by a conventional drip infusion line with an internal diameter of 1.0 mm. The esophageal pressure line was parallelly fixed with a 3–0 silk suture to the esophageal temperature probe (SensiTherm, Abbot). A side hole was made at the distal portion of the esophageal pressure line in order to achieve a real time measurement of the esophageal pressure (Fig. 1). An esophageal temperature probe along with the esophageal pressure line was inserted into the esophagus and positioned at the left atrial posterior level. The position of the temperature probe was confirmed by fluoroscopy and normal saline was injected into the esophageal pressure line, which was connected to a conventional pressure transducer, and the zero level was calibrated at atmospheric pressure. The scale for the esophageal pressure was set at a range between +50 and −50 mmHg. The ECG, SpO2, esophageal pressure, and non-invasive blood pressure were recorded on a polygraph system (FCL-2000, Fukuda Denshi).

Fig. 1

Esophageal pressure monitoring system combined with the esophageal temperature probe. An esophageal pressure line was connected to a pressure transducer.

Conscious sedation during the ablation procedure

After written informed consent was obtained, radiofrequency catheter ablation of AF was performed. Bispectral index (BIS, A-2000, Nihon Kohden, Tokyo) monitoring was obtained. The intracardiac electrograms and 12-Lead ECG were recorded using an EP Workmate (St. Jude Medical, Minneapolis, MN USA). Deep conscious sedation was established by the intravenous administration of midazolam (10 mg), pentazocine (15 mg), and hydroxyzine (25 mg) and were followed by a continuous infusion of dexmedetomidine (7 μg/kg/hr for 10 min). The dose of dexmedetomidine was adjusted by BIS monitoring ranging from 50 to 60.

Statistical analysis

The data are expressed as the mean ± standard deviation for continuous variables and as absolute frequencies and percentages for categorical variables. For continuous variables and categorical variables, the differences between the groups were compared with a Student’s t-test and Fisher’s exact test, respectively. P-values less than 0.05 were considered statistically significant. All analyses were performed with GraphPad Prism version 7.0 software (GraphPad Software, Inc., California).

Results

Patients characteristics

The patient characteristics are shown in Table 1. In 24 patients, desaturation developed due to OA, and airway management was performed in 17 patients (OA group), and no desaturation occurred in the remaining 7 patients (control group). Sixteen patients received a nasal air way and 5 received NPPV (3 patients used both a nasal airway and NPPV). There were no significant differences in the body weight and BMI between the 2 groups (see Table 2).

Table 1

Baseline characteristics of the study subjects.

		OA group			Control group
		(n = 17)			(n = 7)			p-value
Age	(y/o)	61.2	±	10.7	60.7	±	12.9	0.931
Gender (Male/Female)		14/3			6/1			0.780
Body weight	(kg)	74.7	±	15.0	75.0	±	18.5	0.971
Body mass index	(kg/m2)	26.9	±	4.8	25.0	±	4.7	0.381
AF type (PAF/non-PAF)		12/5			7/0			0.150
Systolic blood pressure	(mmHg)	116.1	±	13.1	120.7	±	12.4	0.440
Diastolic blood pressure	(mmHg)	62.4	±	13.4	68.7	±	7.8	0.164
Heart rate	(bpm)	73.0	±	16.9	77.7	±	13.1	0.475

Table 2

Esophageal pressure and percutaneous oxygen saturation.

		OA group			Control group
		(n = 17)			(n = 7)			p-value
Baseline Eso P	(mmHg)	13.2	±	15.1	−0.4	±	2.8	0.002
Nadir Eso P	(mmHg)	−41.5	±	19.6	−12.4	±	5.8	<0.001
SpO2	(%)	91.1	±	4.6	98.0	±	2.0	<0.001
Breathing rate	(/min)	14.7	±	3.3	13.9	±	2.4	0.667

Eso P; esophageal pressure, OA; obstructive apnea.

Esophageal pressure during obstructive apnea

The esophageal pressure was successfully measured in all patients with the custom-made esophageal pressure monitoring system. Fig. 2 shows the esophageal pressure changes during deep conscious sedation without any obvious OA. A periodical esophageal pressure curve associated with the respiratory cycle was confirmed and it became negative (≈−15 mmHg) during the inspiratory phase and returned to baseline during the end expiratory phase (≈0mmHg). On the other hand, the patients with OA exhibited dynamic periodical changes of the esophageal pressure with a substantial negative pressure (≈−50 mmHg). The SpO2 was significantly lower in the OA group than control group (98.0 ± 2.1 vs 91.1 ± 4.6 mmHg, p < 0.001). The OA group had a much greater negative esophageal pressure as compared to the control group. The nadir of the esophageal pressure was more negative in the OA group than control group (−41.48 ± 19.58 vs. −12.42 ± 5.77 mmHg, p < 0.001). A negative esophageal pressure below −30 mmHg preceded the desaturation (SpO2 < 90%) by 52 ± 23 sec.

Fig. 2

A: Esophageal pressure curve without obstructive apnea. There are periodical changes in the esophageal pressure associated with the respiratory cycle. The nadir of the esophageal pressure was approximately −10 to −15 mmHg. B: Esophageal pressure curve during obstructive apnea. A substantial deep negative esophageal pressure was recorded, and the nadir of the esophageal pressure was −50 mmHg.

Airway management and esophageal pressure

The OA group had a substantial negative esophageal pressure, which was restored to a normal range with airway management such as a nasal airway and/or NPPV.

The nasal airway insertion dramatically improved the airway obstruction resulting in a normalization of a substantial negative esophageal pressure (Fig. 3). The deep negative esophageal pressure significantly improved after the airway management with the nasal airway and/or NPPV in the OA group (−41.48 ± 19.58 vs. −16 ± 8.1 mmHg, 0 < 0.001). The SpO2 significantly increased with the airway management in the OA group (91.3 ± 4.58 vs. 97.7 ± 2.0 mmHg, 0 < 0.001).

Fig. 3

A: Time course of the effect of the nasal airway during the obstructive apnea. The nasal airway insertion immediately improved the substantial negative esophageal pressure. B: The effect of the airway management on the esophageal pressure and oxygen saturation in the obstructive apnea group. Pre: Before the airway management, Post: After the airway management.

Complications with esophageal pressure monitoring systems

Total procedure time was not different between the 2 groups (OA group: 189.5 ± 57.0 vs. control group: 162.14 ± 50.2 min, p = 0.26). There were 2 cases of minor nasal bleeding associated with the esophageal catheter insertion in OA group and 1 case in the control group. None of the patients developed any major nasal bleeding requiring otolaryngologic intervention.

Discussion

The esophageal pressure recording is the gold standard for respiratory effort measurements in the patients with sleep related respiratory disorders.[9] It has been reported that OA causes repetitive forced respirations against an upper airway obstruction, which generates a substantial negative pressure (−65 mmHg) in the chest cavity.[10] However, the invasive nature of esophageal catheters, which need to be inserted during sleep, is not tolerated by many patients with obstructive sleep apnea in clinical practice. On the other hand, patients undergoing AF catheter ablation with deep sedation usually undergo esophageal temperature monitoring using an esophageal temperature probe. Therefore, an esophageal pressure line along with the temperature probe could be easily placed in the esophagus during catheter ablation in the same manner. We developed a novel esophageal pressure monitoring system, which could measure real-time esophageal pressures during catheter ablation without any additional procedures or complications.

Obstructive apnea during AF catheter ablation

Obstructive sleep apnea (OSA) is one of the independent risk factors for the development of AF.[11] In addition, the prevalence of OSA in patients with AF is 50%.[12] Anatomical factors including obesity and a small jaw might be associated with the occurrence of OSA.[13] Moreover, deep conscious sedation is often performed for anesthesia and analgesia during catheter ablation of AF. Therefore, the incidence of the occurrence of OA with deep conscious sedation during catheter ablation procedures is inevitably high in patients with AF. We need to focus on the management of OA during AF catheter ablation for a safe and effective procedure.

In the present study, we confirmed that the esophageal pressure could be continuously monitored by a custom-made pressure catheter attached to a conventional esophageal temperature probe during catheter ablation. There were no time consuming or no additional invasive techniques or medical materials needed for the esophageal pressure monitoring. The insertion of the esophageal temperature probe with the pressure monitoring system could be safely achieved during the same procedure as usual.

We reconfirmed that an enormous negative intra-thoracic pressure developed, which reached less than −50mmmHg during OA episodes in AF ablation procedures. The esophageal pressure was measured during OA episodes. The results of a negative esophageal pressure were consistent with the previous basic and clinical investigations.[12], [14], [15], [16] It has been reported that obstructive sleep apnea generates a deep negative esophageal pressure, which could reach −50 to −60 mmHg. These results implied the importance of airway management during ablation procedures. That is because, an inappropriate airway management could cause a deep negative intra-thoracic pressure, which might lead to serious complications. The dynamic motion of the diaphragm during the OA episode has the potential risk of causing a myocardial perforation especially on the left atrial roof, which could lead to cardiac tamponade, and insufficient radiofrequency energy deliveries at the bottom of the pulmonary veins might cause a reconnection between the pulmonary veins and left atrium. Moreover, a deep negative intra-thoracic pressure might cause an air embolization during catheter and sheath manipulation.[17] In the present study, the airway management using a nasal airway and/or NPPV, significantly improved the deep negative esophageal pressure along with a recovery from a desaturation. Esophageal pressure monitoring could immediately detect the development of OA during the procedure. Early detection of OA would make the airway management earlier. There were no serious complications associated with the esophageal pressure monitoring.

Application of the esophageal pressure monitoring

The esophageal pressure monitoring system could be utilized without any additional expensive medical equipment or materials. It was able to immediately detect the occurrence of OA before the occurrence of a desaturation. It could be used not only for the clinical use during AF catheter ablation but also for the evaluation of hemodynamic changes during OA. Deep conscious sedation during the ablation procedure mimics clinically occurring OSA syndrome. Esophageal pressure monitoring with hemodynamic measurements could provide a broad pathophysiological evaluation in patients with OA.

Limitations

There were several limitations to the present study. Firstly, this study was a retrospective and single-center study with a small population. Therefore, the use of a nasal airway and/or NPPV was at the operators’ decision. However, the aim of this study was a preliminary study to evaluate the feasibility and safety of esophageal pressure monitoring during catheter ablation of AF by using a custom-made pressure monitoring system. Secondly, there were no capnometer data that would be sensitive to detect apnea. Further randomized with large scale clinical study will be needed to elucidate the effect of esophageal pressure monitor guided airway management in the catheter ablation of AF.

Conclusion

Esophageal pressure monitoring was a simple and effective method for the evaluation and management of OA during AF catheter ablation procedures.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.