Helium-oxygen Mixture Research Articles

Using helium-oxygen mixtures in the management of acute upper airway obstruction: Skrinskas GJ, Hyland RH, Hutcheon MA Can Med Assoc J 128:555–558 Mar 1983

Using helium-oxygen mixtures in the management of acute upper airway obstruction: Skrinskas GJ, Hyland RH, Hutcheon MA Can Med Assoc J 128:555–558 Mar 1983

Site of airflow obstruction in immediate and late reactions to bronchial challenge with Dermatophagoides pteronyssinus.

The density dependence of maximum flow in ten atopic asthmatics was assessed by response to breathing a helium-oxygen mixture. They were then subjected to bronchial challenge by Dermatophagoides pteronyssinus and density dependence re-assessed during early and late bronchial reactions. There was considerable individual variation in the density dependence before challenge and in the change in density dependence during induced bronchospasm. However, for any given individual the results were similar during early and late reactions. This suggests that the major site of airflow obstruction may vary from one asthmatic to another but that when antigen challenge is followed by a dual early and late reaction the site of obstruction is similar at each stage.

Changes in the air-blood barrier of the lungs during inhalation of helium-oxygen mixtures

Changes in the air-blood barrier of the lungs during inhalation of helium-oxygen mixtures

Determinants of forced expiratory flows in newborn infants.

Maximal flows at functional residual capacity (VmaxFRC) from partial expiratory flow-volume (PEFV) curves (achieved with rapid compression of the chest) were obtained on 11 healthy newborn babies. Mean VmaxFRC, size corrected by dividing absolute values by measured thoracic gas volume, was 1.90 TGV's/s. Specific upstream conductances were high, and the cross-sectional area of the flow-limiting segment was estimated to be approximately 0.30 cm2 in the three infants on whom recoil pressures at FRC were also measured. The cross-sectional area of the major bronchi in the neonate is approximately 0.26-0.30 cm2. PEFV curves were convex to the volume axis. Many of the neonates increased their flows while breathing a helium-oxygen gas mixture. These results suggest 1) size-corrected flows are higher in the neonate than in older children or adults; 2) the site of the flow-limiting segment at FRC during maximal expiratory maneuvers is in large proximal airways, similar to the adult; and 3) the relationship of airway size to parenchymal size may be similar in neonates and adults or, in fact, airways may be larger, relative to parenchyma, in neonates. These physiological data do not support the hypothesis, based on pathological studies, that peripheral airways are disproportionately smaller (when compared with central airways) in infants than in adults.

Long term pulmonary consequences of oesophageal atresia with tracheo-oesophageal fistula.

Lung function was studied in 20 children, aged 8-17 years, who had successfully repaired oesophageal atresia with tracheo-oesophageal fistula. Spirometry and plethysmography showed mild restrictive lung disease. Airways obstruction was assessed using maximal expiratory and inspiratory flow-volume loops in air and after breathing a helium-oxygen mixture. Analysis of the flow-volume data demonstrated significant obstruction at the level of the trachea and little evidence of small airways disease. Bronchial hyperreactivity, as assessed by histamine challenge, was present in 22% of subjects. Respiratory and oesophageal symptoms were common, but decreased in frequency with increasing age. The mechanisms involved in the frequent respiratory symptoms these children suffer are discussed in the light of the physiological findings.

Respiratory Morbidity Among Processing and Mill Workers

Three hundred seventy workers in three tire-manufacturing plants were studied to determine the presence of respiratory morbidity among workers with relatively low current exposure to respirable dust (range, 0.04 to 0.70 mg/m3). Workers in the processing, milling, and less dusty areas of the plants were divided into three groups on the basis of their current and past exposure to respirable dust. Significantly more eye irritation (p less than .01) was found among workers in the milling areas. Workers in the milling areas who were current cigarette smokers had significantly (p less than .05) more chronic bronchitis and loose or productive objective cough than all other current cigarette smokers. The mean forced expiratory volume in 1 s (FEV1), when corrected for age and height, decreased significantly (p less than .01) with increasing duration of cigarette smoking. The mean FEV1 and the forced vital capacity (FVC), when corrected for age, height and cigarette smoking, were the lowest in the group with the lowest dust exposure and highest in the group with moderate dust exposure (the milling areas). The measurement of the difference in flow at 50% of FVC on air and on a helium-oxygen mixture is a sensitive test for small-airway obstruction in the laboratory. In the field, however, the helium-oxygen flow difference did not vary with duration of cigarette smoking as expected, and there was no significant variation by exposure category.

Diurnal variation of air and helium-oxygen flow-volume curves in asthmatic children

In order to assess diurnal variation of flow-volume curves and to determine whether small airways are involved in the diurnal variation of pulmonary function in asthmatic children, we studied eight asthmatics who were attending an asthma summer camp. Spirometry and maximal expiratory flow-volume curves with air and a helium-oxygen mixture were obtained in the morning and afternoon over a 10-day period. We found that significant increases in maximal expiratory flows at all lung volumes occurred in the afternoon. However, the increase in flows with helium (helium response) was unchanged from morning to afternoon. These results suggest that both large and small airways are involved in the diurnal variation of pulmonary function in asthmatic children.

The Maximum Expiratory Flow-Volume Curve with Air and a Low-Density Gas Mixture: An Analysis of Subject and Observer Variability

The subject and intra- and inter-observer variability of three measurements derived from the maximal expiratory flow-volume (MEFV) curve with air and helium-oxygen (HeO2) mixture was determined in ten normal subjects who produced curves in the morning and afternoon of three consecutive days and again on one day a month later. The measurements examined were the maximum flow at 50% vital capacity (V50), the percentage increases in V50 when breathing the He-O2 mixture (delta V50), and the volume at which the curves on air and He-O2 first meet or intersect (VisoV). The delta V50 and VisoV were shown to have a greater degree of variability than the V50 and, in the case of VisoV, this was contributed to significantly by the observer variability. The within-subject variability of the delta V50 and VisoV was so great that the usefulness of these tests in following changes in lung function of individual patients must be questioned.

Temperature regulation in the dog in helium-oxygen environments.

Helium-oxygen mixtures have been reported to alter thermoregulation in humans and animals because of convective heat transfer differences between a helium-oxygen and a nitrogen-oxygen environment. Thermoregulation in unrestrained dogs was tested in a chamber at temperatures of 23, 33, and 43 degrees C, in air or 80% helium-20% oxygen (HeO). Respirations in air in these temperatures were 15, 134, and 322 breaths/min, respectively. Heart rates increased with chamber temperature, averaging 69 at 23, 82 at 33, and 103 beats/min at 43 degrees C. In HeO, responses to increasing temperatures differed from air. Respiration was 13 at 23, 49 at 33, and 336 breaths/min at 43 degrees C. Heart rates were 79 at 23, 70 at 33, and 97 at 43 degrees C. Rectal temperatures rose in both atmospheres at 43 degrees C. Shivering occurred in dogs in HeO at 23 degrees C but not in air. Results indicated that the dogs' thermoregulatory responses were markedly different in the two gas mixtures due to convective heat transfer differences, which were especially noticeable when responses in HeO at 33 degrees C were compared to those in air.

Predominant Site of Airway Resistance in Chronic Obstructive Pulmonary Disease

The purpose of the present clinical research was to establish the major site of resistance and obstruction in patients with severe, symptomatic chronic obstructive pulmonary disease. We used a noninvasive technique by measuring airflow in a plethysmograph after patients breathed air and after breathing a mixture of 80 percent helium and 20 percent oxygen. In group 1 were 14 patients (mean age, 63 +/- 7 years [+/- 1 SD]) with bronchitis. The ratio of their forced expiratory volume in one second over the vital capacity (FEV1/VC) was 43 +/- 10 percent (mean +/- 1 SD), and their single-breath carbon monoxide diffusing capacity (Dsb) was normal (125 +/- 41 percent of the predicted value). In group 2 were 13 patients with emphysema (mean age, 60 +/- 10 years), whose FEV1/VC was 33 +/- 11 percent and Dsb was 55 +/- 14 percent of predicted. All patients had abnormally low increases in the maximum expiratory flow at midvital capacity after breathing the helium-oxygen mixture. The range in group 1 was -11 percent to +14 percent and in group 2 was -10 percent to +15 percent. Normal subjects in our laboratory show increases of at least +24 percent. This indicates that the limitation of airflow occurs primarily in the small (less than 2 mm in internal diameter) and not the large airways.

Mechanism of initiation of oscillatory motion in human glottis.

Phonatory onsets of 17 normal subjects under usual speech conditions were investigated by measuring the cross-sectional area of the glottic aperture, using a photoelectric device. During a normal soft or breathy onset of phonation, the vocal fold vibration begins with an open glottis; the pattern of the optical signal is a sine wave of increasing amplitude with one to eight cycles before steady state oscillation is achieved. The first deflection of the base-line is either towards adduction or towards abduction. The classically assumed--since van den Berg et al. (1957)--retro-aspiration phenomenon, consisting in a narrowing of the glottic chink due to the accelerated air flow, according to Bernoulli's law, is incompatible with these observations. An aerodynamic study, with accurate calibration of the photoelectric transducer in one trained subject, as well as flux and subglottic pressure measurements, suggests that the gas flux (air as well as a helium-oxygen mixture) reaches the condition of turbulence at the level of the glottic nozzle, just before vocal folds are set into oscillatory motion. The setting in motion of the free edge of the vocal folds in normal soft or breathy onset of phonation can be explained by a sudden modification of flow conditions within the expiratory gas : the flow is laminar in the trachea and suddenly becomes turbulent at the level of the glottic nozzle. On the other hand, approximately normal atmospheric pressure values are attained due to a Bernoulli-effect at that level, allowing the vocal folds to oscillate sinusoidally about their vibration axes, corresponding to their virtual resting position, like a forced oscillator.

Helium-Oxygen Mixtures during Bronchoscopy

Fiberoptic bronchoscopy in mechanically ventilated patients has been limited to endotracheal tubes of 8.0--8.5 mm diameter. When performed through smaller tubes, pressures exceeding ventilator limits may occur, alveolar ventilation may become impaired, or progressive hyperinflation from airway obstruction during expiration may result. In this study, the efficacy of a 70% helium-30% oxygen ventilating gas mixture was compared to 30% oxygen in air in a laboratory mechanical lung analog and during 15 bronchoscopies in 7 intubated patients. One patient with a 7.5 mm tube was studied. With the helium-oxygen mixture, ventilator pressures were not exceeded, alveolar ventilation was uncompromised, and hyperinflation did not occur. Bronchoscopy may be safely performed through endotracheal tubes smaller than 8.0 mm using a helium-oxygen mixture.

Antagonism of ethanol narcosis in mice by hyperbaric pressures of 4-8 atmospheres.

Hyperbaric treatment with 100% oxygen or oxygen-helium mixtures at 4-8 atmospheres absolute significantly reduced ethanol sleep-time and increased wake-up blood ethanol concentrations in C57 mice. The results indicate that the antagonism does not result from direct effects of oxygen nor from enhanced ethanol elimination, but appears to involve a direct effect of hyper-baric treatment.

Infection of mice by aerosols of Klebsiella pneumoniae under hyperbaric conditions.

Both the physical behavior of aerosols and survival of airborne Serratia marcescens in hyperbaric chambers with a helium-air mixture at 20 atm of pressure was approximately the same as in the system at ambient pressures. Exposure of mice to aerosols of Klebsiella pneumoniae at 1-, 2-, and 17-atm (ca. 101-, 203-, and 1,722-kPa) pressures of helium-oxygen mixture showed that the number of viable organisms constituting a 50% lethal dose was not significantly affected by the hyperbaric conditions.

Efficacy of Helium-Oxygen Mixtures in the Management of Severe Viral and Post-Intubation Croup

An appreciable number of children with viral or post-intubation croup progress to respiratory failure necessitating an artificial airway. We report seven such patients with critical airway narrowing in whom we reduced the work of breathing by developing helium rather than air as a carrier gas for oxygen. Assessment of patients by a croup-scoring system and blood gas analysis suggests helium-oxygen mixtures to be a useful alternative to intervention with tracheostomy or tracheal intubation. The rationale and limitations of this treatment are discussed.

Low-density gas breathing during exercise in chronic obstructive lung disease.

Because breathing low-density helium-oxygen gas mixture has been reported as improving ventilatory mechanics in chronic obstructive pulmonary disease (COPD) patients and reducing the oxygen cost of ventilation in exercising normal subjects, it might prove useful in COPD physical conditioning programs. 7 COPD patients performed incremental exercise to tolerance while breathing either air on 79% helium-21% oxygen mixture. There was a tendency for low-density gas breathing to stimulate a higher ventilation at any given work load. As a result there was a tendency to greater tolerance with air breathing. Throughout exercise there was no statistically significant difference in endurance, oxygen consumption, heart rate, or ventilatory parameters suggesting that the helium-oxygen mixture was not beneficial to exercise performance.

NSMRL calibration of microphones at depth in dry hyperbaric chambers

A history is given of the primary calibration of microphones in the NSMRL hyperbaric chamber. A Western Electric 640-AA 1-in. condenser microphone was first calibrated by White [NSMRL Report 261 (1955)] using, in a reciprocity technique, a 4-in. and an 8-in. loudspeaker from 125–8000 Hz in air compressed in 50-ft steps to 250 ft simulated sea water (fsw). Most recently Miller calibrated a Bruel and Kjaer (BK) 4144 1-in. microphone in compressed air at 33-ft steps to 132 fsw, using an electrostatic actuator. Data are comparable for these and for three intervening NSMRL studies. They are further comparable to data in the literature for the BK 4132 1-in. condenser microphone collected at a selection of depths to 1023 fsw in compressed air using an electrostatic actuator and for the BK 4144 unit in a helium–oxygen mixture at a selection of depths from 250–870 fsw. It was found that depths to perhaps 400–500 fsw yield a fairly regular linear loss in sensitivity at frequencies to 2 kHz, amounting to 5–9 dB at 200 fsw, and that nonlinearities and resonances occur depending on the microphone used, the depth, and the gas at higher frequencies. Differences among units are such that for careful studies of acoustic noise in such chambers, the calibration of earphones or other transducers, or for the recording of speech in hyperbaric conditions, a facility should arrange for a calibration of its microphone (s) in the gas/depth conditions of interest.

Tremor and somatosensory studies during chamber He-O2 compressions to 13.1, 25.2, 37.3, and 49.4 ATA

Comparison was made between intentional and postural tremor amplitudes with a 2-to 50-Hz bandwidth in four men rapidly compressed from surface to 13.1, 25.2, and 37.3 ATA in 4 h while breathing helium-oxygen mixtures (Predictive Studies IV, University of Pennsylvania). Excursions with compression rates of 20 and 40 ft/min were then made to 49.4 ATA on exposure days 2 and 3, returning to saturation at 37.3 ATA for 6 additional days. During compression from 25.2 to 37.3 ATA, there were increases in tremor amplitudes for both intentional and postural tremor in the 3-to 7-Hz and 8- to 12-Hz ranges. Both types of tremor showed increases in amplitudes at 49.4 ATA on exposure days 2 and 3. Amplitude changes in postural tremor, which occurred only on the fastest compression to 49.4 ATA, were less evident than those in intentional tremor during the remaining dive profile, and adaptation to pressure exposure could be defined by day 8. Intentional tremors did not show adaptation at pressure.

Mechanisms of increased maximum expiratory flow during HeO2 breathing in dogs.

We used the retrograde-catheter technique to investigate the effect of a helium-oxygen gas mixture (HeO2) on resistance to maximum expiratory flow (Vmax) in airways subsegments between alveoli and the equal pressure point (EPP), and between EPP and the flow-limiting segment (FLS). FLS were found at the same site in main-stem bronchi on both air and HeO2 in most dogs studied. Static elastic recoil pressure (Pel = 7 +/- 1 cmH2O) and the lateral pressure at FLS (Ptm' = 11 +/- cmH2O) were not different on the two gases, and delta Vmax averaged 33 +/- 12%. EPP were located on HeO2 in segmental bronchi (7 +/- 2 mm ID), and EPP on air were always located more downstream. There was no density dependence of resistance between alveoli and EPP on HeO2, and delta Vmax was due to the marked density dependence of the pressure losses of convective acceleration in the short airway segment between EPP HeO2 and FLS. Assuming that FLS is the "choke point," these findings are consistent with wave-speed theory of flow limitation modified to account for viscous pressure losses in peripheral airways. These results and conclusions question previous interpretations of delta Vmax as an index of peripheral airways obstruction, and demonstrate the utility of wave-speed theory in explaining complicated mechanisms of expiratory flow limitation.

Esca applied to polymers. XXIII. RF glow discharge modification of polymers in pure oxygen and helium–oxygen mixtures

AbstractThe oxidation of polyethylene, polypropylene, and polystyrene by exposure to plasmas excited in pure oxygen and helium–oxygen mixtures at low power levels has been studied. A detailed curve resolution procedure is outlined, and the rate of oxidation is shown to be a strong function of the polymer structure for pure oxygen plasmas, as is the composition of the oxidized layer; this is not the case, however, for oxidation effected by helium–oxygen mixtures. It seems likely, from a consideration of the available data, that the oxidation is confined to the outermost monolayer and is initiated by a crosslinking mechanism that involves oxygen‐containing functionalities.