The course of anesthesia was divided into five phases. First: induction and intubation, a critical period. Second: dissection, a period of relative calm during which lesion is defined. Third: open airway, a crucial period in which anastomosis is being constructed. Fourth: closure and emergence and fifth: extubation [9], [16], [18].
Most of the patients with narrow airways admission to hospital due to shortness of breath, there are 03 cases of patients who can not lie, 02 cases of life-threatening who have to do the emergency surgery.
Induction is a critical period that needs to combine many flexible methods to control ventilation. The results in Table 5 show that depending on the severity and location of the stenosis, there may be various choices for airway management in the period of induction. The endotracheal tube may be placed above (25 %) or through the lesion (37.5 %), there are 3 patients (18.75 %) showing the distance from the vocal cord to the lesion very short (< 2 cm). We had to use a laryngeal mask (LMAP). It is an effective solution in the first phase.
Patients with severe tracheal stenosis > 90% with a high risk of airway obstruction ensure safety Bricker DL [3]; C.L Chiu [5], CHEN Hai-hong [17] applied the method of cardiopulmonary bypass. Although it is an easy way to ensure gas exchange, systemic anticoagulation theoretically increases bleeding risk, especially if the dissection is extensive, and lung manipulation is unavoidable.
Before the induction, we prepared all emergency equipment to prevent tracheal obstruction. Small-sized catheters to pass through the narrow for jet ventilation, surgeons, as well as surgical facilities, are prepared for tracheotomy. In 2 of our patients with tracheal stenosis > 90%, 01 patients can be intubated and ventilated above the narrow space. For the other, we had to use a small jet catheter pushed through the stenosis for jet ventilation with oxygen pure 100% before the open airway phase.
The open airway phase is a critical period in which anastomosis is being constructed. Once the airway is opened, a flexible endotracheal tube 6.5–7.5 Fr was inserted to the distal airway and ventilated, waiting for ET through the glottis and connected to the high-flow oxygen system. When the surgeon started anastomosis, open the oxygen flow 35–40 l.min-1 so that the oxygen is provided across the surgical field to the distant trachea. The time for apnoeic oxygenation or the time of anastomosis was 16–28 mins, but this time depends on the surgeon's experience. If the apnoea time is too long, which can lead to unsafety like hypercapnia or hypoxia (SpO2 < 90%, blood pH < 7.1)
In the period of anastomosis being constructed 10 and 20 mins (T2, T3), with high flow oxygen 35–40 l.min-1, the blood oxygen pressure improved significantly compared to the time of T0 with PaO2 > 170 mmHg. The acute respiratory acidosis present, the lowest at T3 with pH was 7.17 ± 0.05, and PaCO2 was 79.63 ± 13.39 HCO3- increased significantly but returned to normal immediately after 15 mins mechanical ventilation at T4.
Tracheal resection and reconstruction require the anesthesiologist and the surgeon to share the airway. The greatest benefit of high flow is creating a free surgical field, optimal conditions for anastomosis, and no interruption of surgery without endotracheal intubation and ventilation [7]
Apnoeic oxygenation is the ability to oxygenate a patient in the absence of lung movement. At the onset of apnoea, there is a continued transfer of oxygen from the alveolus to the blood in order to fulfill the metabolic demands of the body. This oxygen transfer leads to emptying of alveoli and a fall in alveolar pressure, which is initially compensated for by reducing alveolar volume from elastic recoil and by carbon dioxide movement from blood to the alveolus. These compensatory mechanisms are rapidly exhausted, and a pressure gradient develops for oxygenation between the upper airway and the alveolus [4], [11], [12].
M Egan and et al also applied oxygen 100% at a flow-rate of 40 l.min‐1 delivered across an open trachea in an apnoeic female patient with subglottic tracheal stenosis. This permitted 42 mins of uninterrupted surgery; oxygen saturations remained above 96% during the apnoeic period and arterial blood gas parameters within acceptable limits. No urgent interruption of surgery or rescue mechanical ventilation was required [4], [7].
Lyons; M. Callaghan et al applied the study between November 2016 and May 2017. 28 patients underwent tubeless laryngeal or tracheal surgery under apnoeic conditions with high-flow nasal oxygen. The median apnoea time was 19 (15–24) mins. Four patients experienced a transient episode of oxygen desaturation to a value between 85% and 90%. The partial pressure of carbon dioxide (PaCO2) of 6.29 (0.71) kPa at baseline and 9.44 (1.12) kPa after 15 min of apnoea. The authors concluded that high-flow nasal oxygen under apnoeic conditions could provide a satisfactory gas exchange to allow tubeless anesthesia for laryngeal surgery [4].
The safe breathing time was calculated from the time when the patient stopped breathing until SaO2 decreased < 90%. Alveoli will continue to take up oxygen even without diaphragmatic movements or lung expansion. In a healthy apnoeic patient, ~ 200–250 ml /min oxygen will move from the alveoli into the bloodstream, only 8–20 ml/min of carbon dioxide moves into the alveoli during apnoea, with the remainder being buffered in the bloodstream given the high water solubility of CO2. In healthy people under ideal circumstances, PaO2 can be maintained at > 100 mmHg for up to 100 mins without a single breath. However, the lack of ventilation will eventually cause marked hypercapnia and significant acidosis, many authors have demonstrated that acute respiratory acidosis within pH > 7.15 is the safety limits are acceptable in the absence of contraindications [6], [7], [12].
The results of Tables 8 and 9 showed that during procedure hemodynamics, oxygen pressure, oxygen saturation (SpO2) were within normal limits. Only 1 patient with hypoxia during surgery is the case of patients with pneumonia in the right lower lobe should support oxygen through the distant airway.
High-flow oxygen under apnoeic conditions can provide a satisfactory gas exchange with gas exchange data improved than before surgery. The surgical field is especially completely spacious, optimal conditions for anastomosis, and no interruption of operation without endotracheal intubation.