Correction of Paradoxical Ribcage Motion in Scoliosis by Noninvasive Ventilation.

STUDY DESIGN: Observational study of ribcage motion in scoliosis. OBJECTIVE: To see whether noninvasive ventilation corrected paradoxical inward motion of the ribs during inspiration. SUMMARY OF BACKGROUND DATA: Paradoxical inward motion of the ribs is observed after rib fractures, low cervical cord injury, and in chronic obstructive pulmonary disease. It is not well recognized in scoliosis and the mechanism in this group has not been studied. METHODS: Linearized magnetometers were used to measure the diameter of the ribcage. Changes in diameter during tidal breathing were recorded during spontaneous ventilation and noninvasive ventilation in 10 subjects with idiopathic or congenital thoracic scoliosis. RESULTS: During spontaneous breathing, the median change in ribcage diameter during inspiration was -1.5 (range -2.3 to -0.8) cm. The median change in ribcage diameter during noninvasive ventilation was +0.5 (range -1.1 to +1.2) cm. Noninvasive ventilation improved paradoxical motion in all subjects, completely correcting it in six. CONCLUSION: Paradoxical inward motion of the ribcage is seen in some subjects with severe scoliosis. This abnormal motion is improved or abolished by noninvasive ventilation. Since noninvasive ventilation takes over the work of breathing from the respiratory muscles, we suggest that inspiratory muscle contraction causes distortion of part of the ribcage in scoliosis, probably because of the abnormal orientation of diaphragmatic muscle fibers. LEVEL OF EVIDENCE: 2.

Enhanced delivery of nebulised salbutamol during non-invasive ventilation.

Non-invasive ventilation (NIV) is used to treat acute respiratory failure. Nebulised drugs can be delivered concurrently with NIV or during breaks from ventilatory support. We hypothesised that the amount of nebulised salbutamol inhaled when delivered via bi-level ventilation would be no different to the amount available directly from the same nebuliser. A standard bi-level ventilation circuit was attached to a lung model simulating adult respiration. Drug delivery was compared when salbutamol (5 mg) was nebulised at different positions in the circuit and separately, with no ventilator. The amount of salbutamol contained in various particle size fractions was also determined. Nebuliser position within the NIV circuit was critically important for drug delivery. Optimal delivery of salbutamol occurred with the expiration port between the facemask and nebuliser (647+/-67 micro g). This was significantly better than nebulisation without the ventilator (424+/-61 micro g; P < 0.01). Delivery when the nebuliser was positioned between the facemask and expiration port was 544+/-85 micro g. The amount of salbutamol contained in particles < 5 micro m was significantly increased when the nebuliser was used in conjunction with bi-level ventilation (576+/-60 micro g vs 300+/-43 micro g, P < 0.001). We conclude that nebulised bronchodilator therapy, using a Cirrus jet nebuliser, during bi-level ventilation increases respirable particles likely to be inhaled when the nebuliser is optimally positioned within the circuit.