Oxygen Supplementation in Noninvasive Home Mechanical Ventilation: The Crucial Roles of CO₂Exhalation Systems and Leakages

Abstract

BACKGROUND: When supplemental oxygen is added to noninvasive ventilation using a non-ICU ventilator, it is usually introduced with a preset flow into the circuit near the ventilator; however, the impact of different CO 2 exhalation systems and leaks on the actual F IO 2 and gas exchange has not been elucidated. METHODS: In a randomized, open-label, 4-treatment (2-by-2), 4-period crossover design, 4 daytime measurements (60 min each) were performed in 20 subjects receiving home mechanical noninvasive ventilation plus supplemental oxygen (> 2 L/min) inserted near the ventilator: active valve circuit or leak port circuit with or without artificial leakage (4 mm inner diameter). Oxygen concentration near the ventilator, oxygen concentration at the mask, and blood gases were measured. RESULTS: Overall, oxygen concentration at the mask (29 ؎ 5%) was lower than oxygen concentration at the ventilator (34 ؎ 4%), with a mean difference of 5.1% (95% CI 4.2-5.9%, P < .001)%. With the leak port circuit, oxygen concentration at the mask decreased by 3.2% (95% CI 2.6 to 3.9%, P < .001), compared to the active valve circuit. When artificial leakage was introduced into the circuit, oxygen concentration at the mask decreased by 5.7% (95% CI 5.1 to 6.4%, P < .001)%, P aO 2 by 10.4 mm Hg (95% CI 3.1 to 17.7 mm Hg, P ‫؍‬ .006), and P aCO 2 increased by 1.8 mm Hg (95% CI 0.5 to 3.1 mm Hg, P ‫؍‬ .008). CONCLUSIONS: The use of a leak port circuit and the occurrence of leak around the interface significantly reduced oxygen concentration at the mask and negatively impacted gas exchange in subjects receiving home noninvasive ventilation and supplemental oxygen. (German Clinical Trials Registry, www.drks.de, DRKS00000449).

Choosing the Proper Interface for Positive Airway Pressure Therapy in Subjects With Acute Respiratory Failure

“…When oxygen is bled into the circuit or interface, the actual level of inspired F IO 2 can vary under the influence of several factors, such as intentional and unintentional leak through the interface or circuit, inspiratory and expiratory pressure settings of NIV, the interface, oxygen flow, and the oxygen administration site. [77][78][79] Oxygen supply is frequently administered via an oxygen port already built into the frame of the interface. The site of oxygen delivery into the circuit is the most important factor in determining inspired F IO 2 .…”

“…77 Administering oxygen into interface results in exhaustion of oxygen out of the exhalation port. 79 Furthermore, oxygen may leak unintentionally between the interface and the face, resulting in low F IO 2 and, hence, low arterial P aO 2 and oxygen saturation. Consequently, when oxygen is administered directly into an interface with a leak port, patients may receive very low oxygen concentrations, which may result in low oxygen saturation in the blood.…”

“…Consequently, when oxygen is administered directly into an interface with a leak port, patients may receive very low oxygen concentrations, which may result in low oxygen saturation in the blood. 78,79 Therefore, during NIV of patients with ARF, using a ventilator in which F IO 2 can be precisely controlled is recommended.…”

Hot Topics in Noninvasive Ventilation: Report of a Working Group at the International Symposium on Sleep-Disordered Breathing in Leuven, Belgium

“…135 Leaks may decrease the F IO 2 when supplemental oxygen is administered during NIV and may lead to significant pressure drops, poor inspiratory triggering, increases in duration of inspiratory pressurization, and even inversion of the inspiratory-expiratory ratio. [135][136][137] Pressure drops induced by unintentional leaks depend on the ventilators tested because leak compensation varies markedly from one ventilator to another (Fig. 2).…”

“…132 Leaks have a clinically relevant deleterious impact in NIV. [134][135][136] In volume-cycled NIV, they lead to insufficient compensation of hypoventilation, lower V T , and lower PEEP and affect the ability of the patient to trigger the ventilator (Fig. 1).…”