Respiratory complications and resort to invasive airway tubes (e.g. tracheostomy tubes) continue to be the most common causes of morbidity and mortality for people with breathing and/or coughing muscle weakness. Just as invasive airway tubes can be used to support breathing muscle function (i.e. support lung ventilation) and expulse airway debris by airway suctioning, so too can noninvasive respiratory techniques be used. These noninvasive respiratory muscle aids are commonly known as noninvasive ventilatory support (NVS) and mechanical insufflation-exsufflation (MIE).
Nobody wants or prefers invasive management and yet physicians and healthcare providers in busy emergency rooms and intensive care units (ICUs) too often fail to administer preferred noninvasive ventilatory care without persistent demands by patients and their families. Tracheostomy is rarely, if ever necessary for cognitively intact infants, children, or adults who are able to cooperate with the use of nasal NVS even if they have no ability to breathe on their own and are being managed by invasive airway tubes.
Indeed, there are patients dependent (24 hours a day) on continuous (C)NVS for over 60 years who will never need them.
In the 1950s and 1960s, many people who have little or no respiratory muscle strength or ability to breathe without support quit iron lungs and other body ventilators to ventilate their lungs during daytime hours by receiving air via a mouthpiece connected to tubing that was connected to blowers, and after 1957, positive pressure ventilators. People would take the amount of air they needed for normal breaths and then release the mouthpiece until the next breath. They would receive the air via simple mouthpieces that they kept gripped in their mouths during sleep (sleeping but alert brains permit gripping of mouthpieces even during sleep). After 1964, the mouthpiece was secured in the mouth by a lip cover retention (“lipseal”). These users of CNVS did not have the benefit of polysomnograms (“sleep studies”), pulmonary function laboratories, or respirators with security alarms, but they thrived anyway, in many cases now for over 60 years. Whether they received air from high pressure blowers, pressure-preset machines that delivered breaths at 20 cm H2O pressure that provided 500 to 700 mL tidal volumes, or from volumes preset at 500 to 700 mL from manual resuscitators or older pre-1957 ventilators that, in turn, created positive inspiratory pressure in the lungs of about 20 cm H2O pressure, their lung ventilation was normal with absolutely normal blood CO2 levels.
It was and has continued to remain obvious that for people with 0 mL of vital capacity (VC), that is, no ability to breathe at all, lung ventilation could remain normal indefinitely without invasive airway tubes. Along with the development of pulmonary function testing designed predominately for lung and airways disease patients and, in the 1970s, polysomnography for people with the obstructive and central sleep apneas and hypopneas of sleep disordered breathing, physicians used to treating sleep disordered breathing patients applied the same reasoning to patients with respiratory muscle weakness and paralysis. Instead of providing full pressure- or volume-preset ventilator settings for full ventilatory support or to more completely rest inspiratory muscles during sleep, with the advent of bi-level positive airway pressure (PAP), inadequate low spans are typically used for people with respiratory muscle weakness. Suboptimal bi-level PAP often inadequately normalizes lung ventilation and provides minimal inspiratory muscle rest, so that with advancing disease, the patients must eventually inevitably develop acute respiratory failure which the clinicians interpret as a “failure of noninvasive ventilation” and a cue to resorting to tracheotomy. Because the problem in this patient population is muscle weakness rather than central or obstructive apneas, this patient population does not generally need polysomnograms, pulmonary function laboratories, expiratory positive airway pressure, supplemental oxygen, or invasive airway tubes, but rather requires clinicians with the knowledge of how to humanely manage them noninvasively. This is widely lacking.
Our goal is to present all possible clinical scenarios for people with breathing muscle weakness and explain the necessary steps to avoid tracheostomy tubes in favor of humane noninvasive ventilatory care.
When you understand the following concepts, you will better comprehend medical texts and articles that you can share with your doctor. Ask you doctor about NVS.
NONINVASIVE VENTILATORY SUPPORT DELIVERY SYSTEMS
During the daytime, NVS can fully support the inspiratory muscles and normalize lung ventilation by the user receiving air from a portable ventilator via a 15-mm angled mouthpiece or nasal prongs. Receiving air via the nose and/or mouth to breathe is called intermittent positive pressure ventilation (IPPV) and then applying negative pressure (cough) is called "mechanical insufflation-exsufflation" or MIE. A mouthpiece can be arranged to be accessible for the user so that he or she can easily grab it to use NVS or MIE. MIE can also be administered via oronasal interface or invasive airway tube.
NVS is delivered air via nasal or oronasal interface for nocturnal (sleep) support. Nasal interfaces are often used for sleep but if air leakage out of the mouth during sleep causes the user to awaken short of breath (as occurs in about 3% of cases), then oral or oronasal interfaces are used.
There are over 100 noninvasive mouthpiece, nasal, and oronasal interface styles available for use during the day or at night. It is our recommendation that patients try several and choose the one that is most comfortable.
Mouthpiece or nasal NVS via a portable ventilator assists or supports the inspiratory muscles. Mouthpiece or nasal NVS via a portable ventilator assists or supports the inspiratory muscles. It also improves the clinical picture by resting respiratory muscles, decreasing metabolic demand, resetting chemoreceptors, opening atelectatic airways, maintaining airway patency, and improving ventilation/perfusion matching.
Portable ventilators such as:
Trilogy[TM], Philips-Respironics Inc.
LTV[TM] series, Pulmonetic Systems Inc., Colton, CA
Newport HT50[TM] Newport NMI, Inc., Newport Beach, CA
are used to deliver breaths. Portable ventilators should be set up to deliver positive pressure air only during inspiration to increase inspiratory (breathing) volume and not during expiration which prevents full exhalation. Thus, it is a common error to use “bi-level positive airway pressure (PAP) machines” which deliver positive airway pressure during both inspiration and expiration and thereby prevent full passive exhalation. Noninvasive ventilatory support is neither low-span bi-level PAP nor continuous PAP (CPAP).
Ventilators are set up on volume-preset at 700 to 1500 mL, the maximum volume that the user finds comfortable, with a backup respiratory rate of 10 to 14 breaths per minute for both daytime and nocturnal (sleep) ventilation for older children and adults. For infants and small children, pressures are preset at approximately 18 to 20 cm H2O with a normal physiological backup respiratory rate dependent on age.
"Active ventilator circuits" (those with “exhalation valves”) are generally best for daytime mouthpiece NVS as opposed to the passive circuits used without exhalation valves for bi-level PAP. Bi-level PAP is only indicated for patients with upper airway collapse and stridor due to upper motor neuron/central nervous system diseases (e.g. amyotrophic lateral sclerosis, cerebral palsy, traumatic brain injury). Bi-level PAP is not indicated for people with simple respiratory muscle weakness.
OXIMETRY FEEDBACK PROTOCOL
All people with breathing or coughing muscle weakness should have an oximeter at home. Oximeters monitor the oxygen saturation (O2 sat) of hemoglobin in the blood. Normal O2 sat is 95% or greater. Provided that supplemental oxygen administration is avoided, oximetry provides very useful information. Anytime the O2 sat decreases below 95%, one of following three respiratory conditions are present:
Lung under (hypo) ventilation causes increased carbon dioxide levels (or hypercapnia). The two important gases in the blood are oxygen (O2) and carbon dioxide (CO2). As respiratory muscles weaken, breathing becomes too shallow to effectively clear CO2 from the blood. Normal metabolic processes continue to produce CO2 and blood CO2 levels rise. This makes people feel tired, sleepy, anxious, depressed, have poor appetites, and if not treated with NVS, eventually develop confusion, obtundation, and respiratory arrest. Lung ventilation is driven by a low O2 sat. However, supplemental oxygen normalizes the O2 sat but diminishes ventilatory drive and CO2 increases. Thus, oxygen administration should never be a substitute for NVS and MIE.
The airways are congested with secretions and other debris due to an ineffective cough: During upper respiratory tract infections (URIs), such as pharyngitis, laryngitis, bronchitis, the flu, and the common cold, if a person's expiratory (coughing) muscles are weak, then their cough flows are diminished and ineffective to clear airway secretions.
If assisted coughing is not used to clear the sputum and NVS is not used on an "as needed" basis, the O2 sat remains below 95% and bacteria multiply in the accumulated secretions causing pneumonia and respiratory failure, lung collapse, and atelectasis (collapse of lung units), and the patient needs to be hospitalized and maybe "intubated."
Thus, people with coughing muscle weakness must be equipped and trained to use noninvasive ventilatory support and mechanical insufflation-exsufflation especially during upper respiratory tract infections to reverse desaturations and maintain normal O2 sat.
For adults with infrequent chest colds, rapid access to MIE during colds may be all that is necessary. Thus, they use oximetry for feedback to gauge the success of their use of NVS and MIE.
Oximetry feedback protocol and use of NVS/MIE is also especially important to prepare an intubated patient for extubation and immediately post-extubation, as well as during decannulation from tracheostomy mechanical ventilation.
Oxygen therapy renders the oximeter useless as a gauge of lung ventilation, decreases the central drive to breath, and exacerbates CO2 levels in the blood.
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