Patients who are critically ill and need oxygen support are usually attached to mechanical ventilator. That’s why, nurses who are in the assigned in the intensive or critical unit should be competent in caring for the patient with mechanical ventilator. Though there are technicalities that a nurse should consider, in this article, we will be learning about this machine in a nutshell.
So, what are the usual indications why patients are intubated and attached to life support device?
Indication for mechanical ventilator use:
- Continuous decrease in oxygenation
- Increase arterial carbon dioxide
- Persistent acidosis
- Other conditions that may lead to respiratory failure
|PaO2 <50 mmHg with FiO2 with >0.60PaO2 > 50 mmHg with pH <7.25
Vital capacity <2 times tidal volume
(Reference: Smeltzer, et al. 2010)
What are the different mechanical ventilator modes?
Volume-cycled ventilators guarantees volume at expense of letting airway pressure vary. Once preset volume is delivered to the patient, the ventilator cycles off and exhalation occurs passively.
Preset tidal volume is delivered unless a specified pressure limit is exceeded (upper airway pressure alarm is set) or patient’s cuff or ventilator tubing has air leaks that cause a decrease in tidal volume delivered. (Grossbach, 2011)
Examples of volume-targeted mechanical ventilator mode are:
- Controlled mechanical ventilation- the client receives a set tidal volume at a set rate. (Silvestri, 2008) This is commonly used for patient who cannot initiate his/her own breathing.
- Assist-controlled (AC )- provides full ventilator support to the patient. A set tidal volume (if set to volume control) or a set pressure and time (if set to pressure control) is delivered at a minimum rate. Additional ventilator breaths are given if triggered by the patient.
- Synchronized intermittent mandatory ventilations (SIMV) – Breaths are given are given at a set minimal rate, however if the patient chooses to breath over the set rate no additional support is given
One advantage of SIMV is that it allows patients to breath on their own. SIMV is usually associated with greater work of breathing than AC ventilation and therefore is less frequently used as the initial ventilator mode
Like AC, SIMV can deliver set tidal volumes (volume control) or a set pressure and time (pressure control). Negative inspiratory pressure generated by spontaneous breathing leads to increased venous return, which theoretically may help cardiac output and function.
Pressure-cycled ventilator guarantees pressure at expense of letting tidal volume vary. Inspiration is also terminated when preset pressure reached. Volume is variable and determined by set pressure level, airway resistance, and lung compliance factors, specified time or flow cycling criteria. (Grossbach, 2011)
Example of this mode
- Pressure support ventilation (PSV) – The patient controls the respiratory rate and exerts a major influence on the duration of inspiration, inspiratory flow rate and tidal volume. The model provides pressure support to overcome the increased work of breathing imposed by the disease process, the endotracheal tube, the inspiratory valves and other mechanical aspects of ventilator support.
What are basic ventilator settings and controls?
Nurses especially in the critical care unit must understand the basics of mechanical ventilation settings and controls.
Ventilator settings and controls:
- Tidal Volume (TV) – Air that the client receives per breathing. Percentage in the mechanical ventilator is adjusted depending on client’s needs (40-100%). The normal value of tidal volume is ½ L or 500 ml.
- Fraction of inspired oxygen (FiO2) – the oxygen concentration delivered to the client. ABG is usually determined before adjusting FiO2 levels. It is adjusted from 40%-100%.
- Peak Flow Rate (PFR) – The peak flow rate is the maximum flow delivered by the ventilator during inspiration. Peak flow rates of 60 L per minute may be sufficient, although higher rates are frequently necessary.
- Back-up Rate (BUR) – for spontaneous or time mode ventilator, back-up rate is set so that the client may receive a minimum number of breaths per minutes if the client fail to breath. If the client’s breathing rate is slower, it will cycle inhale / exhale pressure at the set rate. The usual setting for BUR ranges from 12-22 breaths per minute, depending on the physician’s order.
- Pressure end-expiratory pressure (PEEP) – is exerted during the expiration phase of ventilation, which improves oxygenation by enhancing gas exchange and preventing atelectasis. Not all clients with mechanical ventilator is attached to PEEP. A typical initial applied PEEP is 5 cmH2O. However, up to 20 cmH2O may be used in patients undergoing low tidal volume ventilation for acute respiratory distress syndrome (ARDS)
- Continuous positive airway pressure (CPAP) – used for spontaneously breathing clients. Positive airway pressure is introduced during the respiratory cycle.
- Sensitivity- used to describe the ventilator’s responsiveness to the patient’s breathing effort. Sensitivity adjusts the level of negative pressure required to trigger the ventilator. With assisted ventilation, the sensitivity typically is set at -1 to -2 cm H2 O.
Now, that you know the technical terms of this machine, let’s move on in discussing the things a nurse should consider while caring for a patient with life support device.
How to troubleshoot ventilator alarms?
Alarms are designed to warn nurses that there is something wrong either to the patient or to the mechanical ventilator. But sometimes, alarms can give nurses apprehensions especially if the alarm is non-stop and we don’t know how to troubleshoot the problem.
So as a nurse, how will you manage if there’s an alarm? First, assess the patient if he/she is in distress. Identify the alarm whether high pressure or low pressure. Some mechanical ventilators have their own indicators and shows the cause of the alarm, so it’s important to check your machine as well.
A. Low Pressure alarm
Low pressures alarm may indicate leak in the patient’s tube, disconnection of the tube, or the patient stops to breath.
What are your interventions for low pressure alarm?
- Check the tube connections.
- Reconnect patient to the ventilator.
- Replace leaking tubes by manually ventilating the patient.
- Auscultate patient’s lung fields for bilateral lung sounds.
- Monitor respiratory rate and breathing patterns.
- Evaluate cuff pressure. Reinflate if needed.
B. High Pressure alarm
High pressure alarm may indicate displacement of the ET tube, increased secretions, obstruction in the tube, bronchospasms, or the patient is coughing or biting the tube.
- Assess your patient.
- Auscultate lung fields for secretions. This should be done at least every 2 hours or more.
- Suction secretions as needed. Oxygenate patient manually before suctioning.
- If patient is biting the tube, provide bite block.
- Sedate patient if necessary especially when patient is fighting the vent. Make sure this is ordered by the attending physician or hospitalist on duty.
- Monitor pulse oximeter continuously if cardiac monitor and pulse oximeter devices are present.
What are the bundles of care to avoid Ventilator-associated Pneumonia (VAP)?
Bundles of care for VAP should be strictly observed by the Critical Care Nurses or nurses in any department.
- Strict hand washing. The best way to prevent cross-contamination of any disease is hand washing.
- Oral hygiene. Nurses should always perform oral care to patient attached to mechanical ventilator. Know your hospital policies regarding your standard oral hygiene procedures.
- Initiate closed suction system. Change the system at least every 72 hours or as indicated/needed.
- Avoid pressure ulcers. Turn patient to sides every 2 hours or as needed. Apply cream or ointment to bony prominences or as indicated by the physician.
- Elevate head of bed >30 degrees. Always observe aspiration precaution.
- Assess patient daily for extubation readiness. Early extubation can greatly prevent VAP.
- Daily interruption of sedation.
How to perform closed system suctioning?
- Sterile Closed Suction Kit
- Normal Saline Irrigation
- Suctioning machine or device: wall or portable
- Oxygen source
- Personal protective equipment
- 10 cc syringe
- Pulse oximeter
- Check the guidelines or standard procedure of your unit for closed-suctioning system.
- Prepare all needed equipment. Position all supplies so that they are easily accessible. Check suction setup for correct functioning. Read instructions of the closed-suction kit.
- Explain the procedure to the client. Explain the benefits of closed-suctioning system and how it can prevent infection.
- Assess patient first. Auscultate patient’s lung fields for abnormal breath sounds. Attach patient to continuous pulse oximeter monitoring device.
- Wear personal protective equipment. Perform hand washing.
- Attach closed suction catheter system between ventilator circuit and patient airway.
- Ensure that wall or portable suction is turned on (no higher than 120 mmHg). Set vacuum setting according to policy of your unit.
- Attach suction tubing from setup to suction port of catheter.
- Hyperoxygenate patient to 100% 02 for 2 – 5 minutes.
- Attach saline to irrigation port. You may use also a 10 cc syringe for introducing saline irrigation or depending upon the set-up of your closed-suction kit.
- Introduce catheter before instilling saline – lavage on inspiration.
- Introduce catheter until a restriction is met or until you can stimulate cough reflex.
- Withdraw the catheter slowly while applying intermittent suction. Suction should not be applied for more than 15-20 seconds.
- Upon completion of suctioning, withdraw catheter, ensuring that tip is completely withdrawn from airway.
- Rinse suction catheter after each suctioning by depressing thumb control and squeezing a new saline irrigation using the 10cc syringe or depending on the set-up of your close suction kit.
- Repeat suctioning process until the patient’s airway is clear.
- Discard personal protective equipment and wash hands.
- Evaluate patient’s condition by auscultating the lung fields and by monitoring patient’s oxygenation using pulse oximeter.
Caring for a patient with mechanical ventilator can be challenging but also very manageable. This should be learned by nurses not only at the critical care unit but also nurses in every department.
At first, technicalities may overwhelm a novice nurse, but experience is a very good teacher. If you are unsure of what to do, always go back to the fundamentals of nursing. Don’t be afraid to ask. Check standards and guidelines of your hospital.
As you hone your skills of taking care of patients with life support, you are also gaining competence and confidence.
Never settle down. Never cease to learn!
- Grossbach, I., Chlan, L., & Tracy, M.(2011). Overview of Mechanical Ventilatory Support and Management of Patient- and Ventilator-Related Responses. Critical Care Nurse Vol 31, No. 3, June 2011 retrieved at ccnonline.org last April 10, 2015
- Myers, E. (2006). RNotes: Nurse’s Clinical Pocket Guide. F. A. Davis Company. Philadelphia. 2nd edition.
- Silvestri, L. (2008). Comprehensive Review for the NCLEX-RN Examination. Saunders Elsevier. 4th edition.
- Smeltzer, S., Bare, B., Hinkle, J., Cheever, K. (2010). Brunner & Suddarth’s Textbook of Medical-Surgical Nursing. Lippincott Williams & Wilkins. 12th edition