Management of Chronic Alveolar Hypoventilation by Nasal Ventilation: RESULTS OF LONG-TERM NIPPV
Table 2 lists the signs and symptoms alleviated by long-term nocturnal intermittent positive airway pressure assisted ventilation for the 45 symptomatic patients. Of the 52 patients who underwent trials of nocturnal NIPPV 40 continued it on a long-term basis. The average length of use of NIPPV by the 42 patients who have used NIPPV for one month or more was 21 (three to 67) months. All 18 patients who were dependent on nocturnal assistance alone demonstrated significant improvement and in most cases normalization of daytime ABG off aid. Relief of the signs and/or symptoms of САН occurred in all 40 patients on long-term nocturnal NIPPV without added 02. Two patients had dramatic relief of right ventricular failure and edema (No. 6 and 13). The symptoms of the other five patients were relieved by long-term nocturnal MIPPV.
The NIPPV was initially delivered via a CPAP mask interface (Respironics Co, Inc, Monroeville, PA) but 29 patients complained of excessive pressure on the nasal bridge and upper lip and leak into the eyes. Ten patients could not sleep undisturbed because of NIPPV discomfort and leak. Three who could sleep undisturbed for at least three hours demonstrated no improvement in Sa02 with NIPPV over unaided sleep. Six of the ten were placed on and successfully supported by MIPPV, one by SONI-IPPV, and three by Pulmowrap. A custom molded nasal interface was fabricated for the other 19 patients who were successful using NIPPV with a CPAP mask for at least one night. This interface was found to be more comfortable, to be more cosmetic and to support higher pressures with less interface leak than the CPAP mask for all but two patients. Repeat sleep blood gas monitoring demonstrated at least as effective assisted ventilation with this interface. It has been used for an average of nine (three to 13) months by 17 of these patients. Two patients, including one with Bells palsy, went back to using the CPAP mask interfaces.
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Of the 35 patients who had a trial of or were using body ventilators at the time of referral, 34 preferred the use of noninvasive positive airway pressure ventilation because of comfort, convenience and greater facility for travel and for sleeping with a significant other. Thirteen of 17 of these patients who had been on body ventilators for >five years had demonstrated decreasing assisted minute ventilation and end-tidal Pco2 exceeding 45 mm Hg during body ventilator use at routine yearly reevaluations. In all, 23 patients converted from body ventilators to noninvasive positive airway pressure alternatives with 17 of these using NIPPV Two patients who were comfortable on rocking beds continued their use and had the rocking bed activity trigger NIPPV on assist control mode. One patient used MIPPV and NIPPV on alternate nights.
Four patients who presented with severe САН and who were not using ventilatory aid complained of loss of autonomous respiration during the day (decreased free time) within one month of having been placed on nocturnal intermittent positive airway pressure assisted ventilation. Three of the four patients were found to have had significant improvement in daytime ABG and continuous daytime SaO£ and end-tidal Pco2 levels unaided without a change in VC. In two of these three, free time decreased to <15 min. The third patient complained of dyspnea as soon as he discontinued NIPPV in the morning and required regular periods of MIPPV during the day. The fourth patient with multiple sclerosis had an exacerbation with a sudden decrease in VC to 250 ml. She was placed on NIPPV and became dependent on it 24 h a day. Her VC reached a low of 100 ml and her free time became negligible on the morning after beginning NIPPV.
Avoidance of tracheostomy permitted mastery of GPB by ten of the patients requiring 24-h aid. Nine of ten had <15 min of free time without GPB; yet five had an hour or more with GPB. This gave security in the event of ventilator failure. Effective GPB also normalized speech, the ability to shout and enhanced the ability to cough. The mean VC of these ten patients was 540 ±377 ml sitting. Their mean GPB maximum single-breath capacity was 2,494 ±1,431 ml.
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During URI and acute episodes of nasal congestion or bronchorrhea of any etiology, most of the 40 patients on long-term nocturnal NIPPV used assisted ventilation around the clock because of significantly weaker respiratory muscles and the need for deeper breaths for coughing. Most patients used decongestant drops or pseudoephedrine orally at bedtime to open nasal passages. The NIPPV pressure helped keep these passageways open. When congestion returned, the patient awakened, repeated decongestant use and returned to NIPPV Although 16 patients on NIPPV continued to use it during these episodes, eight others used body ventilators and six MIPPV The mobilization of secretions was facilitated by a combination of aggressive chest therapy, assisted coughing, oral suctioning and the use of a mechanical forced exsufflation device up to five times per hour. In many patients, mucus plugging caused acute oxygen desaturation which was quickly reversed with the use of this device. One patient with Duchenne muscular dystrophy and a VC of 240 ml has had five URI while on nocturnal NIPPV Three of these episodes included hyperpyrexia exceeding 40°C and elevated white blood cell counts. During at least two of these episodes, gas exchange was altered with Sa02 chronically depressed despite 24-h support by NIPPV and MIPPV. All of these episodes were successfully treated by effective mobilization of secretions as described before without intubation, and the patient was hospitalized on only one occasion for hydration and closer observation. Ten patients have not yet had an URI since beginning NIPPV
Two patients were reintubated a total of498 patient- years (average, 9.2 years/patient) since beginning noninvasive aids: one with no significant free time who arrested off aid while traveling in a van and who was intubated in a local hospital, and one who developed severe oropharyngeal muscle weakness.
In the 210 patient-years from the first hospitalization for respiratory impairment to the onset of definitive noninvasive aid, 32 patients were hospitalized a total of 131 times (0.7 time per year). This included 21 patients who had been treated for pneumonia a total of 74 times. In all, the 49 patients dependent on noninvasive aids >one month were treated for a total of 24 pneumonias and have had 47 respiratory hospitalizations in 498 patient-years (0.095 per year). The patients with no significant free time who require 24-h aid have had no episodes of pneumonia and have had only eight respiratory hospitalizations for management of respiratory tract infections with iron lung support and general medical care in 169 patient-years (0.047 per year).
