Noninvasive Forms of Mechanical Ventilation
Some patients need ventilatory support, but may not require an artificial airway. Candidates for noninvasive positive pressure ventilation (NIPPV) include patients who don’t have oxygenation problems, who are able to manage their secretions, and who don’t have an upper airway obstruction. A prime example is a patient with sleep apnea who only requires ventilatory assistance during sleep. The following are the most common types of NIPPV.
Continuous Positive Airway Pressure (CPAP) was mentioned above as a spontaneous breathing mode that can be delivered by a ventilator through an ETT or tracheostomy. CPAP can also be delivered through either a nasal mask or a full face mask. There are pros and cons to each of these. Full face masks minimize air leaks, but they are more claustrophobic, and they must be removed for the patient to speak or expectorate secretions. Also, a smaller air leak leads to greater pressure buildup and gastric distention. Nasal masks are less claustrophobic and don’t have to be removed to speak or expectorate, but they usually have large air leaks. A customized mouthpiece with a lip seal may be used for chronic CPAP application. This is the ideal delivery method, since the seal is maintained even when the facial muscles are relaxed. A separate CPAP machine is used to deliver noninvasive CPAP rather than the ICU ventilator.
As mentioned above, CPAP maintains constant airway pressure. Remember that the effect is like blowing up a balloon and not letting it completely deflate before blowing it up again. Resistance and the work of breathing are decreased.
Bilevel Positive Airway Pressure (BiPAP) is similar to CPAP, and in practice, the two are often confused. BiPAP maintains positive airway pressure during both inspiration and expiration. The two levels are referred to as inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). The machine cycles between IPAP and EPAP either in response to the patient’s respiratory efforts, or at a specific time determined by the respiratory rate and inspiratory time settings. The benefits of IPAP include increased tidal volume and minute ventilation, decreased PaCO2 level, relief of dyspnea, and reduced use of accessory muscles. Benefits of EPAP include increased functional residual capacity, resulting in an increased PaO2 level.
In the acute care setting, BiPap is usually delivered through a full facemask or a face shield. In the home setting, a patient being treated with Bipap will usually use a nasal mask, allowing exhalation through the mouth.
Intermittent Positive Pressure Breathing (IPPB) is used in some institutions to assist patients to take deeper breaths, especially after surgery or for a short time after mechanical ventilation has been discontinued. The IPPB machine is a pressure-cycled ventilator that delivers compressed gas under positive pressure into the patient’s airway. It’s triggered when the patient inhales, but it allows passive expiration. The specific pressure and volume used are ordered by the physician for each patient. Usually, 10-20 breaths are given every 1-2 hours for 24 hours. Benefits of IPPB include prevention of atelectasis, promotion of full-lung expansion, and improved oxygenation.
Nursing Care of the Mechanically Ventilated Patient
Nursing Care of the Endotracheal Tube (ETT)
ETT management consists of ensuring a patent airway, suctioning pulmonary and oral secretions, and providing frequent oral and/or nasal care. If the patient is restless or agitated, any activities that involve loosening the straps that hold the ETT in place should be rescheduled for when the patient is calm or after a sedative has been given. Otherwise, the ETT may be inadvertently removed.
A primary portion of ETT management is suctioning down the tube every two hours or as needed. This is a sterile procedure. The color and amount of any sputum return should be noted since the ETT provides a direct connection to the lungs, making these patients highly susceptible to infection. The oral cavity should also be suctioned as these patients often have difficulty swallowing saliva.
The patient must also be monitored for skin breakdown in either the oral or nasal cavity, depending on where the ETT is located. Thorough oral care should be provided every eight hours and as needed. If the patient has a bite block to prevent them from biting on the tube, it must be removed and cleaned or replaced every eight hours. The tube should be repositioned so that it is not continuously exerting pressure in the same area. If the tube is taped to the patient’s face, the tape must be removed and replaced on the opposite side of the face at least once per day and as needed.
The ETT has a cuff that is inflated with air to hold the tube in place in the trachea. The amount of air in the cuff should be checked every eight hours to ensure that the cuff is not exerting too much pressure on the trachea walls. This is often done by the respiratory therapist but may be done by the nurse.
Any needed supplies for endotracheal tube care should be at the bedside prior to beginning the procedure. This includes a sterile suction kit; a bottle of sterile 0.9% sodium chloride; sterile gloves; a clean bite block, if necessary; and tape torn into appropriately sized pieces. It’s recommended that another healthcare professional firmly hold the ETT in place during any activity that requires loosening the straps that hold the tube. The patient should also be preoxygenated with 100% oxygen prior to suctioning.
After ETT care, the patient’s respiratory status should be reassessed. The insertion point (in centimeters) of the ETT should be confirmed to be the same as prior to the procedure, unless the purpose of the procedure was to change the depth of the tube.
Nursing Care of the Tracheostomy Tube
Tracheostomy (trach) care should be done every eight hours and involves cleaning around the incision, as well as replacing the inner cannula if the patient has a double-lumen tube. After the site heals, the entire trach tube is replaced once or twice per week, depending on the physician’s order. The goals of tracheostomy care are to maintain the patency of the airway, prevent breakdown of the skin surrounding the site, and prevent infection.
Extra precautions should be taken when performing site care during the first few days after the tracheostomy is surgically created. The site is prone to bleeding and is sensitive to movements of the tube. It’s recommended that another healthcare professional securely hold the tube while site care is performed. Tracheostomy care should not be done while the patient is restless or agitated, since this increases the chance that the tube may be pulled out and the airway lost.
Trach care begins with suctioning the patient’s airway, both via the tracheostomy and orally. The patient should be preoxygenated with 100% oxygen prior to suctioning, and sterile technique must be used during the procedure. The gauze dressing is removed and the amount and color of drainage should be noted. Using sterile technique, the skin and external portion of the tube is cleaned with hydrogen peroxide. Cotton-tipped applicators should be used to clean close around the stoma. The condition of the skin and stoma should be noted. The area is then wiped with gauze dampened in 0.9% sodium chloride and a new dressing is applied.
If the patient has a disposable inner cannula, the old cannula can simply be removed and discarded. A new cannula is inserted using sterile technique. If the inner cannula isn’t disposable, it must be cleaned with hydrogen peroxide, rinsed with 0.9% sodium chloride, and reinserted using sterile technique. The cannula should be tapped against the side of the sterile container to remove excess fluid; it shouldn’t be completely dried since the film of saline facilitates reinsertion.
All supplies needed for tracheostomy care should be at the bedside prior to beginning the procedure. There are prepackaged kits available that contain gauze pads, cotton-tipped applicators, a tracheostomy dressing, and hydrogen peroxide. In addition, a container of 0.9% sodium chloride solution, a suction kit, and sterile gloves are needed. The velcro straps or ties that hold the tracheostomy tube in place may need to be replaced as well.
If the patient is agitated, a sedative should be given and the procedure rescheduled for a later time when he or she is calm. Pain medication should be offered, especially during the first few days after surgery when manipulating the incision can cause discomfort.
After tracheostomy care is finished, the soiled dressing and supplies should be discarded, either in the garbage or in a biohazard container if there is a large amount of blood. The patient may need to be suctioned again and his or her respiratory status should be reassessed. Again, pain medication should be offered, as appropriate.
Suctioning consists of inserting a sterile suction catheter into the airway in order to remove secretions. This is an extremely important part of caring for a patient with an artificial airway since the normal reflex of coughing to expectorate secretions is not effective. The patient will experience respiratory distress if the tube is obstructed by sputum. Suctioning should be performed only when the patient needs it; however, the need should be assessed at least every two hours.
A number of studies have been done to determine ways to minimize the complications of suctioning. Sterile technique should be used to decrease the risk of infection. There are now closed suction systems available that are attached to the ventilator tubing on one end and to the artificial airway on the other. The catheter remains protected inside a sterile plastic sleeve and is changed every 24 hours. This system limits the amount of times the tubing must be disconnected from the airway, thus reducing exposure of the trachea to environmental contaminants.
Suctioning causes oxygen deprivation for the time that the suction is applied. Hypoxemia can be minimized by preoxygenating the patient with 100% oxygen prior to suctioning and between each pass of the suction catheter. This can be done by either pushing the 100% oxygen button on the ventilator or by using a manual resuscitation bag. The patient’s pulse oximetry should be monitored while suctioning. The duration of each suction pass should be limited to ten seconds and the number of passes should be limited to three or less, if possible. This decreases hypoxemia and airway trauma. Studies have shown that using intermittent suction is no more beneficial than continuous suction.
Installation of a small amount of saline prior to suctioning was a common procedure in the past. It was thought that saline helped loosen and remove secretions; however, research has shown this to be a false assumption. On the contrary, saline installation has been shown to increase infection rates and to cause decreased oxygen levels for longer periods than suctioning without saline use. Therefore, saline installation should not be used routinely (Kuriakose, 2008).