Paul C Stillwell, MD F.C.C.P.;[Unke...

Paul C Stillwell, MD F.C.C.P.;[Unkeyable] James D Quick, B R.R.T.;[Unkeyable] Patricial R Munro RRT; Section and George B Mallory, Jr MD F.C.C.P.[Unkeyable]

The combination of helium with oxygen is les thick than air and as similar has been beneficial to patients with airflow obstruction within the large airways. The project of this study was to evaluate the effectiveness of delivering [He-O.sub.2] through open-circuit systems by measuring [DDsub50] in five adult offers The mean ([+ or -] 1 SD) [DDsub50] with a nonrebreathing mask was 132 [+ or -] 089 with a simple mask was 121 [+ or -] 087 and with a nasal cannula was 100 [+ or -] 013; the [DDsub50] with the nonrebreathing mask and the simple mask was statistically greater than with the cannula (p<005) pair infant oxygen hoods were assessed by way of measuring the nitrogen concentration at different locations in the cloaks The [N.sub.2] concentration increased progressively from top to bottom, indicating that the helium was concentrated at the top. We close that the nonrebreathing mask and simple masks are probably satisfactory [He-O.sub.2] delivery theorys that the infant oxyhood may be suboptimal, and that the nasal cannula is ineffective.

(Chest 1989;95 1222-24)

Therapeutically, a helium-oxygen mixture has been used to put to the test to reduce complications related to airflow obstruction in asthmatic subjects[1] in patients with partial upper airway obstruction,[2,3] in infants with bronchopulmonary dysplasia,[4] and in patients with COPD[5] During tidal breathing of a lower density gas, the transpulmonary crushing required for a given tidal turn is less because there is les resistance to airflow.[2,4,6] The potential benefits of lowered resistance to run are several: decreased work of breathing; les dynamic airway collapse; and les hyperinflation. These physiologic advantages may avoid respiratory muscle fatigue and following acute respiratory failure in near patients.[2,3]

The [He-O.sub.2] mixture is les condensed than air and allows a higher melt rate throughout the vital capacity, excluding at very low pulmonary volume[7] The quality of DD of maximal airflow can be measured from MEFV winds as the ratio of melt breathing [He-O.sub.2] to the come breathing air at a given pulmonary volume[7] For optimal therapeutic benefit, [He-O.sub.2] should be delivered in a closed-circuit arrangement to avoid entertainment of latitude air, which will dilute the [He-O.sub.2] and thus increase the density of the gas mixture. in the same state [i]or[/i] condition systems can be cumbersome and hard to utilize in uncooperative patients or in pediatric patients. The project of this study was to examine the delivery of [He-O.sub.2] in a less degree than open-circuit conditions.

MATERIALS AND METHODS

Delivery of [He-O.sub.2] was evaluated in sum of two units open-circuit systems (nasal cannula and simple face mask) and the same closed-circuit system (standard nonrebreathing mask). The effectiveness of [He-O.sub.2] delivery for each connected view was measured by calculating the [DDsub50] anticipating that inefficient gas delivery would breed a low DD. A commercially available mixture of 80 percent helium and 20 percent oxygen (Mid southward Oxygen) was delivered to controls by each of the three classifications for a minimum of five minutes, as shown in the following tabulation detailing the testing sequence:

Standing air spirometry

Supine air spiometry Supine [He-O.sub.2] nonrebreathing mask (13 L/min for five minutes) Supine [He-O.sub.2] spirometry

Air breathing (> five minutes) Supine air spirometry Supine [He-O.sub.2] nasal cannula (6 L/min for five minutes) Supine [He-O.sub.2] spirometry

Air breathing (> five minutes) Supine air spirometry Supine [He-O.sub.2] face mask (6 L/min for five minutes) Supine [He-O.sub.2] spirometry

The emanate rate with the nonrebreathing mask was generally 13 L/min The issue rate used with the simple mask and nasal prong was 6 L/min. These melt rates were determined by an oxygen flowmeter (Ohio protoplast 304-5501-800) and were not corrected for [He-O.sub.2]; the same flowmeter was used for each delivery method studies.

Five healthy adult offers (three male and two female subjects; mean age, 332 years) who were all previously experienced in spirometric maneuvers, participated in the consideration Standing room-air spirometry was performed initially to assure normal baseline pulmonary function.[8] All measurements were made with a 13-L wedge spirometer (525 Pulmonizer, M Science) with computer-assisted data printout that provided the two MEFV curves and spirometric values. Testing was done in the supine position to simulate actual clinical conditions. Maximal expiratory maneuvers were performed breathing air prior to each archetype of [He-O.sub.2] delivery system, in this way that each calculation of DD was made with an FEF50 (air) obtained immediately prior to the FEF50 ([He-O.sub.2]). The [DDsub50] was calculated as the ratio of FEF50 ([He-O.sub.2]) to FEF50 (air). The nonrebreathing rule was tested first in each enthrall to assure a normal [DDsub50] The nasal prong were evaluated nearest followed by the simple mask. Several minutes elapsed between the testing of each delivery body to allow adequate washout of [He-O.sub.2] before the nearest air test. Each expose mastered the technique of taking a moderate maximal inhalation through both the simple mask and the nonrebreathing mask, holding their breath at maximal inhalation while transferring from the mask to the mouthpiece of the spirometer, then beginning the forced exhalation maneuvers. This was to avoid exceeding the arise rate of [He-O.sub.2] during inspiration, entraining sweep air, and decreasing the difference in density of gases. While breathing [He-O.sub.2] by the agency of the nasal prongs, each make subordinate breathed only through his or her nose and took moderate maximum inspiration through the nose prior to beginning the spirometry. Testing was repeated until the FVC between ordeals varied less than 5 percent