Ventilator-Assisted Living©

Fall 1995, Vol. 9, No. 2

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Suggestions for Avoiding Respiratory Complications

John R. Bach, MD, University Hospital, Newark, New Jersey

The best ways to avoid respiratory complications commonly associated with having weak inspiratory and expiratory muscles are:

Failure to effectively remove airway secretions is the main reason people with weak respiratory muscles develop pneumonia. People who have muscles with normal strength remove airway secretions by coughing. Those who have not destroyed the connective tissue that holds their lungs together by cigarette smoking and who, therefore, do not have irreversible obstructive lung disease, and who have sufficient throat muscle strength to fully open their vocal cords, can cough effectively either by manually assisted coughing or by mechanically assisted coughing with the In-exsufflator.

The In-exsufflator provides mechanical insufflation/exsufflation by delivering a deep breath through a mask covering the nose and mouth. The positive pressure is followed by negative pressure for forced exhalation. This method can also be used through a tracheostomy tube, instead of tracheal suctioning, because it is more comfortable and effective than suctioning. When suctioning routinely, it is next to impossible to get the suction catheter into the left airway for anatomical reasons. Thus, most pneumonias are in the left lung. In-exsufflation does not damage airway tissues, and it is necessary for anyone with throat muscle function for whom manually assisted coughing is not very effective.

It is advisable to have your maximum cough flow measured by an Access Peak Flow Meter (HealthScan, Inc., Cedar Grove, New Jersey). This device costs about $8. You simply cough through it and measure the flow. If your vital capacity (VC) is less than 1.5 L, cough through it after receiving a maximum deep breath (inspiration). Then cough through it after receiving a maximum insufflation and having someone give you an abdominal thrust. The latter measure is the most important. Anyone who can generate 180 L/min (3 L/s) of cough flow in this manner does not need a tracheostomy tube whether the VC is 3000 ml or nothing at all.

If maximum flows are under 4-5 L/s be certain that you obtain or have rapid access to an Inexsufflator. Do not hesitate to use it every 10-15 minutes around the clock and at pressures from +50cm H20 to -50 cm H20 when you have secretions. Your local home care company should be able to obtain one for you within two hours if you develop a cold, need surgery, or have airway secretions for any reason. If you have not had a deep breath in a long time, increase the positive pressure gradually or else a deep insufflation can cause a muscle pull in the chest.

The second part of avoiding respiratory complications is maintaining normal ventilation. Your oxygen saturation (SaO2) should always be over 94%. This can be measured with an oximeter (new models cost under $1,000).

People who have been using body ventilators are almost always underventilated, and they should consider switching to the use of nocturnal mouthpiece -- lipseal -- intermittent positive pressure ventilation (IPPV) or nasal IPPV. Anyone can maintain normal ventilation by properly using these techniques. It is critical, however, that normal ventilation be maintained both during the day and the night. BIPAP® systems are not usually appropriate for people with neuromuscular conditions who need or who will need aid during the day as well as the night because you cannot take a deep breath (air stack) with a BIPAP® system.

When SaO2 is below 95%, it means you are underventilated and should be using noninvasive IPPV, or you have a mucus plug which needs to be removed by manually or mechanically assisted coughing immediately, or you waited too long to remove the mucus plug and you now have pneumonia.

A baseline SaO2 of 92-94% while maintaining normal ventilation and optimally removing mucus usually indicates microscopic atelectasis. The chest X-ray is usually normal, and the SaO2 baseline returns to normal by continuing to maintain normal ventilation and by effectively removing mucus. When the baseline is below 92%, the mucus has been left too long, and you may have developed pneumonia or other serious complications which may then become an emergency.

Unfortunately, when one has pneumonia and the baseline SaO2 is under 90%, oxygen therapy may be necessary, noninvasive inspiratory aids are often no longer effective, and tracheal intubation may become necessary. DO NOT LET YOURSELF GET INTO THIS SITUATION. If you cannot avoid being intubated, however, continue using mechanical in-exsufflation through the endotracheal tube until baseline SaO2 goes over 92%. When the pneumonia shows signs of clearing, return to the use of noninvasive IPPV. Do not accept a tracheostomy tube unless the intubation lasts over 2-3 weeks. If you undergo tracheostomy, but still have functional throat muscles, have the tube removed and return to using noninvasive aids. If you absolutely require surgery, be certain that you are returned to your noninvasive aids as soon as you wake up (barring excessive sedative and narcotic use) whether you can breathe or not. The longer you are intubated, the greater the risk of respiratory complications. In other words, you must be prepared for emergency situations, and, if possible, you should prepare your local hospital for such emergencies so that they are familiar with you and with your equipment.

A warning about oxygen therapy: it decreases one's own ventilation, increases blood carbon dioxide (CO2) levels, and can lead to people stopping breathing completely. It also prevents one from using an oximeter to indicate underventilation and mucus plugs. It should only be used when one requires intensive care.

Only YOU can prevent your lungs from becoming diseased. If throat muscles weaken to the point that maximum peak assisted coughing flows can not exceed 3 L/s and the upper airway is too closed for the In-exsufflator to be effective (such as in people with ALS and infantile SMA), a tracheostomy becomes the only option and invasive management routines can be followed. Polio survivors, people with Duchenne muscular dystrophy, and people with high level SCI who can swallow rarely ever need tracheostomy tubes.

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