INTRODUCTION
Tracheal stenting under anaesthesia can be a definitive or palliative treatment for
many patients with tracheal obstruction due to various benign and malignant aetiologies.[1
2] Deep sedation is preferred in mild to moderate grades of tracheal stenosis over
general anaesthesia due to surgical accessibility, greater cost-effectiveness, good
patient and operator satisfaction.[3
4
5]
Oxygenation and airway management become difficult during this procedure due to a
shared airway and a stenotic trachea. Intermittent ventilation can also interrupt
the procedure. STRIVE Hi can mitigate this problem by delivering up to 70 Lmin-1 of
heated and humidified air--oxygen mixture up to 100% FiO2via a specialised nasal cannula.
This review assesses the safety and efficacy of STRIVE Hi in patients undergoing tracheal
stenting surgery.
METHODS
This is a retrospective review which was conducted in a tertiary level regional cancer
center. After obtaining a waiver from the institutional review board, data from August
2017 to July 2018 were collected retrospectively from the hospital electronic medical
record (EMR) of the Hospital Management System (HMS) Software Version 1.2.0 of our
hospital.
A total number of ten patients (n = 10) who underwent tracheal stenting with HFNO
support during that period were included. In all the patients, HFNO was delivered
using an AIRVO 2™ device (Fisher and Paykel Healthcare, Auckland, New Zealand).
Preprocedural preparations included intravenous (IV) injection of glycopyrrolate 4
μg/kg body weight and inj. ondansetron 4 mg. The airway was nebulised with 5 ml of
4% lignocaine topical solution in the preparation area under monitoring. The HFNO
humidifier was turned on in the operating room for at least 10 min before the arrival
of the patient, to allow the humidifier to warm. SpO2, Non Invasive Blood Pressure
(NIBP), Electrocardiography (ECG), and respiratory waveform from the ECG leads were
continuously monitored during the procedures.
The specialised HFNO nasal cannula was attached and preoxygenation was carried out
with 100% oxygen at 30 L min-1, which was continued until sedation was administered.
The treating anaesthesiologist then administered a translaryngeal injection 4 ml of
4% lignocaine through the cricothyroid membrane to block the recurrent laryngeal nerve.
A 10% lignocaine spray was given orally to the oropharynx and posterior pharyngeal
area. A bite block was used in all patients to protect the bronchoscope. Sedative
agents, such as midazolam, fentanyl, and/or propofol, were given, at the discretion
of the anaesthesiologist, and titrated the sedation depth to the target of 'Deep Sedation'
(Approved by the ASA House of Delegates on October 13, 1999, and last amended on October
15, 2014).[6] Sedation was maintained with intermittent intravenous boluses of the
sedative agents. The spontaneous respiration was ensured by continuous clinical monitoring
of chest excursion and respiratory waveform from the ECG leads.
The oxygen flow rate was increased to 50 L min-1 immediately after sedative agents
were given and was maintained at 30--70 L min-1 during the procedure, according to
the requirement and patient tolerance. At the end of the procedure, the patient was
shifted to the recovery area with Hudson Mask and moist oxygen flow at 4--6 L min.-1
The age, sex, American Society of Anesthesiologists (ASA) physical status grading,
associated comorbidities, and primary diagnosis were noted. Baseline data included
SpO2before and after preoxygenation was noted. Procedural data including the number
of hypoxic episodes (SpO2below 90%); duration of hypoxia; minimum SpO2recorded; the
number of interruptions during the procedure to allow anaesthetic interventions, duration
of the procedure, any other complications including arrhythmia and cardiac arrest
were noted.
RESULTS
The number of patients underwent tracheal stenting was ten (n = 10). Mean age was
59.2 years with SD of 5.45. Seven were male and three were females. One patient was
of ASA I, two were of II and seven patients were of ASA III with common comorbidities
like hypertension, diabetes mellitus, and hypothyroidism. The primary diagnosis was
of lung carcinoma in five patients, oesophageal carcinoma in four patients, and one
patient developed tracheo-oesophageal fistula as a result of oesophageal carcinoma
[Table 1].
Table 1
Demographic data
Serial number
Age
Sex
ASA grading1
Primary diagnosis
Comorbidity
1
55
M
2
Ca2 esophagus
HTN3, DM4
2
55
M
2
Ca lungs
HTN
3
60
F
3
Ca lungs
HTN
4
61
M
2
Ca esophagus
DM, hypothyroid
5
54
F
2
Ca esophagus with TOF5
HTN, DM
6
63
M
2
Ca lungs
DM
7
53
M
1
Ca esophagus
No
8
67
F
2
Ca lungs
DM
9
56
M
2
Ca esophagus
HTN
10
68
M
3
Ca lungs
HTN, hypothyroid
Mean
59.2
SD6
5.45
Median
2
1American Society of Anesthesiologists physical status classification, 2Carcinoma,
3Hypertension, 4Diabetes mellitus, 5Tracheooesophageal fistula, 6Standard deviation
Preoperatively mean room air SpO2was 96.7% with an SD of 1.25%, which improved following
preoxygenation. Mean post-pre-oxygenation SpO299.6% with an SD of 0.699%. The mean
minimum SpO2during the procedure was 92.7% with an SD of 4.667. The median minimum
SpO2 during the procedure was 94.5% [Table 2].
Table 2
Study observations
Serial number
Baseline SpO2
1 in room air (%)
Post-pre - oxygenation SpO2 (%)
Number of hypoxic episodes
Duration of hypoxic episodes (s)
Minimum SpO2 (%)
Number of interruptions during the procedure
Duration of the procedure (min)
Complications if any
1
98
100
0
NA2
98
Nil
55
no
2
98
100
1
15
85
Nil
55
no
3
98
100
0
NA
94
Nil
50
no
4
96
100
0
NA
96
Nil
60
no
5
95
98
1
10
89
Nil
45
no
6
97
100
0
NA
96
Nil
60
no
7
95
99
0
NA
95
Nil
70
no
8
96
100
0
NA
94
Nil
45
no
9
98
100
0
NA
95
Nil
50
no
10
96
99
1
10
85
Nil
55
no
Mean
96.7
99.6
11.667
92.7
54.5
SD
1.25
0.699
2.886
4.667
7.619
Median
94.5
1Oxygen saturation percentage, 2Not applicable
Only three out of ten patients had a single hypoxic episode of SpO2below 90%. The
mean duration of hypoxia was 11.67 s with an SD of 2.89 s. The mean duration of the
procedure was 54.5 min with an SD of 7.62 min. There were no interruptions for anaesthetic
interventions or need for additional oxygenation during the procedure. No complications
occurred during the procedure [Table 2].
DISCUSSION
Management of airway during tracheal stenting under deep sedation is often considered
challenging which requires a constant effort to avoid desaturation and subsequent
interruption during the procedure. This are the main disadvantages of deep sedation.[1
2
3
4
5] In this regard, General anaesthesia with tracheal intubation is beneficial to maintain
adequate oxygenation and ventilation. Endotracheal intubation can be very difficult
at times and can cause traumatic airway injury in a stenosed trachea.[7] Second, muscle
paralysis with positive pressure ventilation may push the blood and the secretions
to deeper parts of the lungs. Deep sedation with spontaneous respiration without endotracheal
intubation (tubeless anaesthesia) has definite advantages over general anaesthesia
as the oral aperture, larynx, face, neck, and all other areas apart from the nose
remains free to be operated upon. This could include cases with a partially obstructed
airway or patients undergoing instrumentation in the airway.[8] The addition of STRIVE
Hi technique can make it safer by preventing desaturation.
Although no specific literature is available regarding the use of STRIVE Hi during
tracheal stenting procedures, many studies have been published showing the efficacy
of STRIVE Hi technique in other airway surgeries.[5
8
9] The safety of this technique is attributed to its mechanism of action which includes
washout of pharyngeal dead space, reduction of work of breathing and airway resistance,
effect of positive end expiratory pressure (mean values ranging between 2.7 and 7.4
cm H2O), continuous positive airway pressure (CPAP), and delivery of a constant fraction
of inspired oxygen up to 100%.[10
11
12] It also has good tolerability in awake patients. These properties made this device
useful particularly during emergence from anaesthesia; hence, it can be used comfortably
till the patient becomes fully awake in the recovery.
HFNO can be beneficial for procedures requiring periods of apnoea. Rise in carbon
dioxide can be a major concern in patients undergoing HFNO therapy during apneic oxygenation
(THRIVE).[9] However, it is reported to be insignificant in patients undergoing HFNO
therapy during spontaneous breathing (STRIVE Hi), where expiration is not abolished.[6]
Risk of oxygen toxicity with the use of HFNO can be minimised by decreasing the FiO2,
as much of the benefit of HFNO is due to the high flow and less due to high FiO2.
Risk of worsening of pneumothorax is also present with HFNO due to its CPAP effect
and hence it should be practiced with caution. Laser surgeries are to be done with
caution using less FiO2, though not absolutely contraindicated.[9]
Our review was conducted to assess the adequacy of HFNO in spontaneously breathing
patients which can avoid frequently associated problems of desaturation and procedural
interruption. All patients were evaluated prior to the procedure by the pulmonologist
with bronchoscopy for the site and the feasibility of passing the flexible bronchoscope
through the stenosed area. Patients with Cotton--Myer grading II (50--70%) and III
(70--90%), without extension of tracheal stenosis to any part of the bronchus, were
planned for stenting with a flexible bronchoscope. Hence, no patient underwent Y-stenting
and none of them had a critical stenosis. Patients with emergency obstruction and
severe narrowing of trachea underwent stenting procedures without HFNO using rigid
bronchoscopy and hence not included in this review. As patent airway is a necessary
for STRIVE Hi to work efficiently, appropriate sedation and a mechanism to keep airway
patent has to be ensured.
The elective cases which underwent stenting only through flexible bronchoscope with
HFNO support were included. Out of the ten patients we have observed, only three patients
had an episode of desaturation below 90% with a mean duration of 11.67 s, the lowest
SpO2being 85%, all of which recovered spontaneously or needed minimum intervention
like head tilt, chin lift, and jaw thrust only, but neither of them caused any interruption
in the procedure. Our results are consistent with studies showing benefits of STRIVE
Hi in various clinical scenarios.[10
11
12]
However, our review specifically considers the subset of patients who underwent tracheal
stenting procedures in our hospital setup. As tracheal stenting is not a very common
procedure, small sample size is the limitation of this review.
CONCLUSION
Spontaneous respiration and titrated sedation with HFNO STRIVE Hi provides adequate
oxygenation during tracheal stenting procedures. HFNO STRIVE Hi is associated with
a low incidence of desaturation and a low frequency of interruption in the procedure
by the need to mechanically ventilate patients' lungs.
Financial support and sponsorship
Tata Medical Center, Kolkata.
Conflicts of interest
There are no conflicts of interest.