Management of Chronic Alveolar Hypoventilation by Nasal Ventilation: RESULTS OF PATIENT TRIALS
The 52 patients had a mean sitting VC of 766 ± 639 ml (16.3 ± 12.5 percent predicted) and a mean supine VC of 407 ± 257 ml (9.9 ±2.3 percent). This included who could not remain off ventilatory assistance for 24 h without severe dyspnea, hypercapnia and hypoxia. The complaints of dyspnea and fatigue that necessi¬tated reinstitution of assisted ventilation and termi¬nated the trial of free time were generally accompa¬nied by a decrease in Sa02 of >5 percent and an elevation of Pco2 of >7 mm Hg from baseline levels. The free time that a patient had was related to his VC. None of the 20 patients with VC supine <12 percent of predicted had more than 15 min of free time supine except for three patients with Duchenne muscular dystrophy for whom significant free time was accompanied by severe hypoventilation. Nineteen patients with supine VC between 12 to 26 percent had varying amounts of free time, often at the expense of significant hypercapnia, and could not go overnight without ventilatory aid. In all, 35 patients had <6 h of free time supine with 23 having <15 min. Although up to 22 patients could sleep supine for varying periods of time unaided, any decrease in the customary aid schedule was accompanied by deterioration in ABG or overt respiratory failure in a matter of days.
Seventeen of the 22 patients who could sleep unaided prior to introduction of NIPPV had at least two overnight continuous Sa02 and end-tidal Pco2 studies during unaided respiration and then repeat studies on NIPPV The results of the overnight sleep monitoring of these patients are shown in Table 3. There was a statistically significant improvement in Sa02 from 81.8±11.0 percent to 94.1 ±3.4 percent (p<0.0001) on NIPPV The maximum end-tidal Pco2 improved from 68 ±18 mm Hg to 46 ±5.9 mm Hg (p<0.001) for the ten patients in whom end-tidal Pco2 was studied. These patients also had end-tidal Pco2 >50 mm Hg for 31 ± 21 min/h unaided and 5.5 ± 10.6 min/h on NIPPV. canadian pharmacy cialis
Sixteen of the remaining 30 patients were tried on and eventually converted to NIPPV from other methods of overnight assisted ventilation. They also had at least two overnight continuous SaO£ and end-tidal Pco2 studies on their former ventilatory aid and then had the studies repeated on NIPPV These patients had <400 ml of VC supine and <15 min of supine free time. Their mean SaOz was 95.9 ±2.6 percent during the sleep studies on NIPPV Fifteen of the 16 patients had an average Sa02 of 95 percent or greater and an average Sa02 during their worst hour of 91 percent or greater. Nine of 11 patients for whom it was studied had a maximum Pco2 <46 mm Hg. Seven of these 16 patients had had <90 percent mean Sa02 during sleep on their previous aids. Five were on body ventilators and two on MIPPV without a Bennett lip seal (Puritan-Bennett Inc, Boulder, CO).
Four patterns of insufflation leak and oxygen desat- uration were observed to be predominant in 36 patients during trials of NIPPV
1. Fourteen patients had minimal leak and no significant desaturation. For these patients the lips remained closed, were plugged by tongue movement with each breath, or oral leak was blocked by the passive mechanical effect of nasal ventilation sealing the soft palate against the tongue. For the patients who had plugged hp opening with the tip of the tongue with each breath, the floor of the mouth moved up and out with each insufflation. This appeared to be a passive mechanical effect because the one patient who had electromyographic monitoring of the genioglossus during sleep on NIPPV demonstrated no increase in electrical activity during this movement.
2. Seventeen patients had predominantly a continual, limited leak out of the mouth creating a snoring effect with the lips vibrating. Insufflation pressures dropped with resulting periods of mild hypercapnia and oxyhemoglobin desaturation throughout the night.
3. Two patients had predominantly intermittent leak with the mouth open. Desaturation by four to 15 percent occurred at regular 45- to 60-s intervals. This caused arousal reflex tongue and pharyngeal move¬ments which cut off leak and the Pco2 and Sa02 returned to baseline prior to the next leak episode. The resulting sawtooth pattern of desaturation is more commonly seen in patients on MIPPV
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4. Three patients had severe oral leak and ineffec¬tive ventilation. The trial of NIPPV was discontinued in favor of MIPPV or SONI-IPPV
