Nocturnal oximetry and transcutaneous carbon dioxide in home-ventilated neuromuscular patients.

BACKGROUND: Pulse oximetry alone has been suggested to determine which patients on home mechanical ventilation (MV) require further investigation of nocturnal gas exchange. In patients with neuromuscular diseases, alveolar hypoventilation (AH) is rarely accompanied with ventilation-perfusion ratio heterogeneity, and, therefore, oximetry may be less sensitive for detecting AH than in patients with lung disease. OBJECTIVE: To determine whether pulse oximetry (S(pO(2))) and transcutaneous carbon dioxide (P(tcCO(2))) during the same night were interchangeable or complementary for assessing home MV efficiency in patients with neuromuscular diseases. METHODS: Data were collected retrospectively from the charts of 58 patients with chronic neuromuscular respiratory failure receiving follow-up at a home MV unit. S(pO(2)) and P(tcCO(2)) were recorded during a 1-night hospital stay as part of standard patient care. We compared AH detection rates by P(tcCO(2)), S(pO(2)), and both. RESULTS: AH was detected based on P(tcCO(2)) alone in 24 (41%) patients, and based on S(pO(2)) alone with 3 different cutoffs in 3 (5%), 8 (14%), and 13 (22%) patients, respectively. Using both P(tcCO(2)) and S(pO(2)) showed AH in 25 (43%) patients. CONCLUSIONS: Pulse oximetry alone is not sufficient to exclude AH when assessing home MV efficiency in patients with neuromuscular diseases. Both P(tcCO(2)) and S(pO(2)) should be recorded overnight as the first-line investigation in this population.

Automatic air-leak compensation in neuromuscular patients: a feasibility study.

Air leaks often result in alveolar hypoventilation in mechanically ventilated patients with neuromuscular disease. The primary objective of this study was to assess the feasibility, efficacy and tolerance of a ventilator equipped with an automated air-leak compensation system in a clinical situation. Fourteen neuromuscular patients with nocturnal air leaks during home ventilation were included in a prospective randomised crossover study. A modified VS Ultra ventilator was studied during two consecutive nights and patients were randomly ventilated with and without a leak-compensation system, respectively. Tolerance, minute ventilation, blood gas values, sleep parameters, and nocturnal oxygen saturation were assessed. Leak compensation significantly increased the mean inspiratory and expiratory tidal volumes (731+/-312 vs. 1094+/-432 ml [p=0.002] and 329+/-130 vs. 496+/-388 ml [p=0.006], respectively) and inspiratory and expiratory flows (51.7+/-8.2 vs. 61.8+/-12.4 l/min [p=0.016] and 63.3+/-26.2 vs. 83.3+/-37.8 l/min [p=0.013], respectively). The system acted by increasing both inspiratory time (from 1355+/-230 to 1527+/-159 ms, p=0.038) and inspiratory pressure (from 14.0+/-2.8 to 18.3+/-3.4 cm H(2)O, p=0.002). Leak compensation improved arterial PCO(2) (6.18+/-0.9 vs. 5.21+/-1.0 kPa, p=0.004), slow-wave-sleep latency (119+/-69 vs. 87+/-35 min, p=0.04), and tolerance. Air-leak compensation is feasible and may produce beneficial effects in neuromuscular patients. The automatic air-leak compensation system tested here should be evaluated in long-term efficacy and tolerance studies and compared to other ventilation modes capable of compensating for leaks, such as pressure support.