basics of mechanical ventilation

mechanical ventilation part 1

1. Basics of mechanical ventilation part 1 Radhwan Hazem Alkhashab Consultant anaesthesia & ICU 2022

2. Introduction A  Mechanical Ventilator  is a device that is used to provide positive pressure ventilation in order to help normalize a patient’s arterial blood gas levels to maintain an adequate acid-base balance

3. Indication of Mechanical Ventilation (R espiratory conditions) Insufficient Oxygenation  – Inadequate oxygenation, which is known as hypoxemia. Insufficient Ventilation   :the patient have hypoxia & hypercarbia. Acute Lung Injury   : occurs from an event such as sepsis, pneumonia, aspiration, or trauma .

4. Indication (non- respiratory condition )   Control of intracranial pressure in head injury. Airway protection following drug overdose. Following cardiac arrest . For recovery after prolonged major surgery or trauma. Severe Hypotension  : such as with shock, sepsis, and Congestive Heart Failure (CHF).

5. What are the Benefits of Mechanical Ventilation ? These include the following: It helps decrease the patient’s work of breathing which helps the respiratory muscles rest and recover.  It helps the patient get adequate amounts of oxygen. It provides stability and allows medications to work while the patient heals. It helps the patient achieve adequate ventilation by removing carbon dioxide for effective gas exchange.

6. Modes of Mechanical Ventilation The two primary control variables are  Volume Control  and  Pressure Control . In Volume Control, the operator has the ability to set (and control) the patient’s tidal volume. In Pressure Control, the operator can set (and control) the pressure level in order to achieve a desired tidal volume.

7. Mechanical Ventilation Settings Examples of the Basic Ventilator Settings: Mode Tidal Volume: The recommended tidal volume is 4-8 mL/kg , Peak pressures should be maintained at less than 30cm H 2 O, and plateau pressures at less than 15 cm H 2 O.  This means that the patients should be ventilated at faster rates and lower tidal volumes to prevent barotrauma. Frequency (Rate ): should be set at higher than normal, 18-25 breaths per minute. FiO2 I:E Ratio PEEP Alarms

8. I:E ratio Inspiratory to Expiratory ratio: (I: E) normally this ratio is 1:3 meaning it takes longer to expire than it does to inspire.  By decreasing the ratio to 1:2 or 1:1, this allows more time to inspire in oxygen, but it will cause the CO 2  to rise.  This technique can also cause  breath stacking  and lead to a pneumothorax.

9. Weaning from Mechanical Ventilation Weaning is the process by which the patient’s dependence on mechanical ventilation is gradually reduced to the point where spontaneous breathing sufficient to meet metabolic needs is sustained .

10. The patient should be : A wake and co-operative with intact neuromuscular function. Have stable cardiovascular function with minimal requirements for inotropic or vasopressor drugs. Not have a marked ongoing respiratory metabolic acidosis Have inspired oxygen requirements < 50 %. Be able to generate a vital capacity >15 mL/kg , tidal volumes > 5 mL/kg , and a negative inspiratory pressure >- 20 cmH2O. Have low sputum production and be able to generate a good cough. Have adequate nutritional status.

11. Weaning involve reduction in level of ventilatory support. Pressure support ventilation (PSV) and synchronized intermiĴent mandatory ventilation (SIMV) are the most commonly used ventilatory modes and these techniques are forms of partial ventilatory support. Weaning may also be facilitated by the use of a tracheostomy tube, which has the advantage of reducing dead space and allowing sedation to be discontinued.

12. There are several parameters used for extubation including the Rapid-Shallow Breathing Index and the PaO 2 /FiO 2  ratio. In general, a PaO 2 /FiO 2  ratio of 300 or greater, and a RSBI of < 80 indicate that the patient is ready to wean from mechanical ventilation.  Patients should not be considered for extubation if they require an Fi02 of more than 40% or a PEEP > 5 to maintain oxygenation.

13. Early versus late tracheotomy in ICU patients Studies have already shown the advantages of tracheotomy compared with endotracheal intubation, including: S horter ICU or hospital stay. L owered airway resistance. I mproved pulmonary toilet. F ewer lung infections. P rotection for direct laryngeal injury. F acilitated nursing care. Improved patient comfort. B enefits for oral feeding, which are associated with the administration of smaller amounts of sedative. Early versus late tracheotomy in ICU patients: A meta-analys... : Medicine (lww.com)

14. What are the Risks and Complications of Mechanical Ventilation? Barotrauma – This is a condition in which the alveoli of the lungs rupture due to overinflation from increased pressure levels . Volutrauma – This condition occurs when the alveoli become filled with fluid due to high tidal volumes. commonly occurs in patients with Acute Respiratory Distress Syndrome (ARDS ). Ventilator-Associated Pneumonia (VAP)  – This condition is a lung infection that develops 48 hours or more after a patient has been intubated and placed on the ventilator.

15. Auto-PEEP  – Auto-PEEP, or Intrinsic PEEP, is characterized by over-inflation of the lungs due to large tidal volumes, restrictive airways, or a prolonged inhalation time. If left untreated, this condition can progress to barotrauma and collapsed lungs . Oxygen Toxicity  – This occurs when a patient receives too much oxygen for too long of a period of time. In general, patients who receive an FiO2 > 60% for extended periods of time are at risk of oxygen toxicity .

16. End of basic mechanical ventilation Part 1