High intensity non-invasive ventilation (HI-NIV), a controlled form of positive pressure ventilation with high inspiratory pressure, is currently recognized as the most effective means of improving physiological and clinical parameters in patients with hypercapnic chronic obstructive pulmonary disease (COPD). However, the constant high inspiratory pressures are not well tolerated by all patients, and it has been suggested that HI-NIV may impair cardiac function. Alternative means of mechanical ventilation may prove beneficial.
Ventilation modes that target a set tidal volume are an alternative to this traditional fixed inflation pressure ventilation. Volume targeting controls the amount of air entering the lungs with each breath in order to ensure adequate ventilation for a given person’s lung volume with reduced risk of lung trauma.
A study by Windisch’s group in Germany has investigated whether target tidal volume non-invasive ventilation (VT NIV) may be a valuable alternative to HI-NIV for patients with COPD. To date, this mode of ventilation has been studied mainly in subjects with obesity hypoventilation syndrome, and little is known of its efficacy for COPD patients. Can VT NIV provide additional clinical benefits in these patients already established on HI-NIV?
Subjects with COPD and chronic hypercapnia who were established on HI-NIV for at least 3 months, and who reported good compliance to overnight HI-NIV, were eligible for the study. Care was first taken to select each patient’s optimal target VT NIV setting from one of two estimates calculated according to either 8mL/kg ideal body weight or 110% of individual tidal volume during HI-NIV. The target value producing a lower mean nocturnal transcutaneous partial pressure of carbon dioxide was selected. Subjects were then discharged for home mechanical ventilation with these target VT NIV settings and reassessed for defined parameters after 3 months.
Two major findings of the study were that: 1) the transfer of patients to optimal target VT NIVdid not improve sleep efficiency and overall sleep quality, and 2) VT NIV produced similarly effective results as HI-NIV therapy in terms of outcome parameters such as the control of nocturnal hypoventilation, daytime hypercapnia, overnight ventilation patterns, subjects’ tolerance, health related quality of life, lung function and exercise capability. Thus they conclude that VT NIV does not offer additional clinical benefits compared to well establishedHI-NIV in chronic hypercapnic subjects with COPD, and switching modes of mechanical ventilation is not generally recommended.
Despite a relatively high drop out rate (4 of 14 subjects) and thus a low sample size, the authors point out that their findings potentially show aggressive forms of target VT NIV are not harmful to patients with COPD. This suggests investigation of VT NIV as an alternative forCOPD patients unable to tolerate HI-NIV is warranted.
JH Storre, E Matrosovich, E Ekkernkamp, DJ Walker, C Schmoor, M Dreher et al, ‘Home mechanical ventilation for COPD: high-intensity versus target volume noninvasive ventilation’, Respiratory Care, 2014;59:1389-97.