Difference In Airway Resistance Research Articles

Early and late effects of volatile sedation with sevoflurane on respiratory mechanics of critically ill COPD patients

BackgroundThe objective was to compare sevoflurane, a volatile sedation agent with potential bronchodilatory properties, with propofol on respiratory mechanics in critically ill patients with COPD exacerbation.MethodsProspective study in an ICU enrolling critically ill intubated patients with severe COPD exacerbation and comparing propofol and sevoflurane after 1:1 randomisation. Respiratory system mechanics (airway resistance, PEEPi, trapped volume, ventilatory ratio and respiratory system compliance), gas exchange, vitals, safety and outcome were measured at inclusion and then until H48. Total airway resistance change from baseline to H48 in both sevoflurane and propofol groups was the main endpoint.ResultsSixteen patients were enrolled and were sedated for 126 h(61–228) in the propofol group and 207 h(171–216) in the sevoflurane group. At baseline, airway resistance was 21.6cmH2O/l/s(19.8–21.6) in the propofol group and 20.4cmH2O/l/s(18.6–26.4) in the sevoflurane group, (p = 0.73); trapped volume was 260 ml(176–290) in the propofol group and 73 ml(35–126) in the sevoflurane group, p = 0.02. Intrinsic PEEP was 1.5cmH2O(1–3) in both groups after external PEEP optimization. There was neither early (H4) or late (H48) significant difference in airway resistance and respiratory mechanics parameters between the two groups.ConclusionsIn critically ill patients intubated with COPD exacerbation, there was no significant difference in respiratory mechanics between sevoflurane and propofol from inclusion to H4 and H48.

A computational analysis on the impact of multilevel laryngotracheal stenosis on airflow and drug particle dynamics in the upper airway.

Laryngotracheal stenosis (LTS) is a type of airway narrowing that is frequently caused by intubation-related trauma. LTS can occur at one or multiple locations in the larynx and/or trachea. This study characterizes airflow dynamics and drug delivery in patients with multilevel stenosis. Two subjects with multilevel stenosis (S1 = glottis + trachea, S2 = glottis + subglottis) and one normal subject were retrospectively selected. Computed tomography scans were used to create subject-specific upper airway models. Computational fluid dynamics modeling was used to simulate airflow at inhalation pressures of 10, 25, and 40 Pa, and orally inhaled drug transport with particle velocities of 1, 5, and 10 m/s, and particle size range of 100 nm-40 µm. Subjects had increased airflow velocity and resistance at stenosis with decreased cross-sectional area (CSA): S1 had the smallest CSA at trachea (0.23 cm2) and resistance = 0.3 Pa·s/mL; S2 had the smallest CSA at glottis (0.44 cm2), and resistance = 0.16 Pa·s/mL. S1 maximal stenotic deposition was 4.15% at trachea; S2 maximal deposition was 2.28% at glottis. Particles of 11-20 µm had the greatest deposition, 13.25% (S1-trachea) and 7.81% (S2-subglottis). Results showed differences in airway resistance and drug delivery between subjects with LTS. Less than 4.2% of orally inhaled particles deposited at stenosis. Particle sizes with most stenotic deposition were 11-20 µm and may not represent typical particle sizes emitted by current-use inhalers.

Airway morphological abnormalities of bronchiolitis assessed by endobronchial optical coherence tomography.

A few studies have reported the medium-sized and small airway morphological abnormalities of bronchiolitis. Whether spirometry or impulse oscillometry (IOS) is correlated with airway remodeling of bronchiolitis remains unclear. Aiming to demonstrate the airway morphological abnormalities of bronchiolitis obliterans (BO) and diffuse panbronchiolitis (DPB) assessed by endobronchial optical coherence tomography (EB-OCT), and elucidate whether spirometric and IOS parameters have correlation with the airway remodeling of bronchiolitis. We recruited 18 patients with bronchiolitis (BO, n = 9; DPB, n = 9) and 17 control subjects. Assessments of clinical features, St. George's respiratory questionnaire (SGRQ), chest computed tomography (CT), spirometry, IOS, and EB-OCT were performed in all enrolled subjects. The correlation between EB-OCT and lung function parameters was studied and analyzed. The magnitude of abnormalities of spirometric and IOS parameters was significantly greater in patients with bronchiolitis than that in control subjects (p < 0.05). Patients with BO had notably lower forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, maximal mid-expiratory flow (MMEF)% pred and higher resonant frequency (Fres), and area of reactance (AX) than those with DPB (p < 0.05). The EB-OCT measurement among patients with bronchiolitis and between the bronchus in the left and the right lung demonstrated a heterogeneous distribution of airway calibers, presenting a high intra- and inter-individual variability. Patients with bronchiolitis had notably greater airway wall area (p < 0.05) compared with control, while BO presented greater magnitude of airway abnormalities than DPB. Fres and the difference in airway resistance at 5 and 20 Hz (R5-R20) correlated negatively with medium-sized and small airway inner area, and correlated positively with airway wall area (p < 0.05), whose correlation coefficients were higher than those of spirometric parameters. Bronchiolitis, BO and DPB, manifested a heterogeneous distribution of airway calibers with significant intra- and inter-individual variability. IOS parameters, rather than spirometry, correlated better with medium-sized and small airway remodeling in bronchiolitis assessed by EB-OCT measurement.

Characteristics of airway resistance in obstructive sleep apnea patients with asthma on oscillometry

Background: Asthma and obstructive sleep apnea (OSA) are prevalent chronic respiratory disorders with a high tendency to coexist. Both diseases involve increased airway resistance in the upright position because of narrow upper or lower airways. Moreover, there is a marked increase in airway resistance in the supine position in patients with OSA. We verified the characteristics of OSA in combination with asthma. Methods: Airway resistance was measured by oscillometry in the upright and supine position in 11 healthy participants (control), 59 patients with OSA alone, and 33 OSA patients with asthma (coexistence) in the hospital between April 2014 and July 2020. We compared the differences in airway resistance between the upright and supine positions among the three groups. In addition, we performed cephalometry to evaluate the upper airway structure in patients with OSA alone and in patients with both OSA and asthma. Results: A marked increase in airway resistance due to postural change was observed in the “OSA alone” group compared to that in the control group. However, this was not observed in the “coexistence” and control groups. Moreover, the “coexistence” group had fewer structural abnormalities in the upper airway than the “OSA alone” group on cephalometry. Conclusions: The airway resistance of patients with OSA alone markedly increased with posture change because of upper airway abnormalities. However, there was a smaller increase with postural changes in OSA patients with asthma, suggesting the possibility of a smaller degree of upper airway abnormality compared to patients with OSA alone. Clinical Trial Registration number: This study is approved by the research ethics committee of the Shinshu University School of Medicine (permission number: 4272)

Children with Asthma Have Fixed Airway Obstruction through Childhood Unaffected by Exacerbations

Children with asthma may have a disease course with or without exacerbations, but the relationship between exacerbations and lung function development is poorly understood. To compare lung function trajectories from birth till adolescence in asthmatic children with and without exacerbations. Children with asthma from the Copenhagen Prospective Studies on Asthma in Childhood2000 (COPSAC2000) birth cohort had lung function and bronchial reactivity assessed repeatedly from 1 month to 13 years. Exacerbations were diagnosed at the COPSAC clinic defined as symptoms requiring hospitalization, oral or high-dose inhaled corticosteroid treatment. Mixed models were applied to analyze lung function trajectories. Children with asthma with exacerbations (N= 50) had a trajectory of increased, fixed airway obstruction compared with children without exacerbations (N= 47): z-score difference in airway resistance (sRawz) (95% confidence interval [CI]):+0.34 (+0.03;+0.66), P= .03, and maximal mid-expiratory flow (MMEFz):-0.41 (-0.69;-0.13), P= .004, but no differences in forced expiratory volume (FEVz):-0.14 (-0.41;+0.13), P= .29, or bronchial reactivity to methacholine (PDz):+0.08 (-0.26;+0.42), P= .65. This did not change comparing lung function trajectories before and after exacerbations: z-score difference (95% CI) sRawz:-0.04 (-0.35; 0.27), P= .80; MMEFz: 0.01 (-0.02; 0.04), P= .55; FEVz: 0.02 (-0.02; 0.05), P= .42; and PDz:-0.01 (-0.06; 0.05), P= .88. Children with asthma with exacerbations compared with children with asthma without exacerbations are characterized by increased airway obstruction since infancy through childhood. The airway obstruction is a fixed trajectory without progression due to exacerbations, suggesting that exacerbations are a consequence rather than a cause of diminished airway caliber in childhood.

Comparison of pressure-regulated volume control ventilation and pressure control ventilation in patients with abdominal compartment syndrome.

Mechanical ventilation support is commonly required in abdominal compartment syndrome (ACS). In the present study, pressure-regulated volume control ventilation (PRVCV) was compared to pressure control ventilation (PCV) in patients with ACS. The prospective study included 40 patients with ACS who were randomized into the PCV or PRVCV groups and subjected to the different modes of ventilation. After 6 h of ventilation, arterial blood gas, respiratory mechanics and hemodynamics parameters, as well as the intra-abdominal pressure (IAP) and Sequential Organ Failure Assessment (SOFA) scores were calculated. Compared to the PCV mode, mechanical ventilation with PRVCV lead to a significant decrease in the partial pressure of carbon dioxide, the peak inspiratory pressure, the mean inspiratory pressure, the central venous pressure, the heart rate and the extravascular lung water index. In addition, a marked improvement in pH, partial pressure of oxygen, oxygenation index and pulmonary static compliance was noted. However, no significant differences in airway resistance, mean arterial pressure, or IAP and SOFA scores were obtained. In conclusion, the PRVCV mode is better than the PCV mode in ventilation patients with ACS, and should therefore be used as a lung protective strategy. The present study was registered at Chictr.org (no. ChiCTR1800016869).

Contributions of Kinetic Energy and Viscous Dissipation to Airway Resistance in Pulmonary Inspiratory and Expiratory Airflows in Successive Symmetric Airway Models With Various Bifurcation Angles.

The aim of this study was to investigate and quantify contributions of kinetic energy and viscous dissipation to airway resistance during inspiration and expiration at various flow rates in airway models of different bifurcation angles. We employed symmetric airway models up to the 20th generation with the following five different bifurcation angles at a tracheal flow rate of 20 L/min: 15 deg, 25 deg, 35 deg, 45 deg, and 55 deg. Thus, a total of ten computational fluid dynamics (CFD) simulations for both inspiration and expiration were conducted. Furthermore, we performed additional four simulations with tracheal flow rate values of 10 and 40 L/min for a bifurcation angle of 35 deg to study the effect of flow rate on inspiration and expiration. Using an energy balance equation, we quantified contributions of the pressure drop associated with kinetic energy and viscous dissipation. Kinetic energy was found to be a key variable that explained the differences in airway resistance on inspiration and expiration. The total pressure drop and airway resistance were larger during expiration than inspiration, whereas wall shear stress and viscous dissipation were larger during inspiration than expiration. The dimensional analysis demonstrated that the coefficients of kinetic energy and viscous dissipation were strongly correlated with generation number. In addition, the viscous dissipation coefficient was significantly correlated with bifurcation angle and tracheal flow rate. We performed multiple linear regressions to determine the coefficients of kinetic energy and viscous dissipation, which could be utilized to better estimate the pressure drop in broader ranges of successive bifurcation structures.

Specific airway resistance in healthy young Vietnamese and Caucasian adults

In healthy Vietnamese children the respiratory resistance has been suggested to be similar at 110cm height but larger at 130cm when compared with data in Caucasians from the literature, suggesting smaller airways in older Vietnamese children (Vu et al., 2008). The hypothesis tested here is whether the difference in airway resistance remains consistent throughout growth, and if it is larger in adult Vietnamese than in Caucasians. Airway resistance and Functional Residual Capacity were measured in healthy young Caucasian and Vietnamese adults in their respective native country using identical equipment and protocols. Ninety five subjects in Vietnam (60 males) and 101 in France (41 males) were recruited. Airway resistance was significantly larger in Vietnamese than in Caucasians and in females than in males, consistent with difference in body dimensions. Specific airway resistance however was not different by ethnicity or gender. The findings do not support the hypothesis that airway size at adult age – once normalized for lung volume – differs between Vietnamese and Caucasians.

Abr, a Negative Regulator of Rac, Attenuates Cockroach Allergen–Induced Asthma in a Mouse Model

Abr deactivates Ras-related C3 botulinum toxin substrate (Rac), a master molecular switch that positively regulates many immune cell functions, by converting it to its GDP-bound conformation. In this article, we report that, in the absence of Abr function, cockroach allergen (CRA)-immunized mice experienced a fatal asthma attack when challenged with CRA. The asthma in abr(-/-) mice was characterized by increased pulmonary mucus production, elevated serum IgE, and leukocyte airway infiltration. Decreased pulmonary compliance was further documented by increased airway resistance upon methacholine challenge. Peribronchial and bronchoalveolar lavage eosinophils, key cells associated with allergic asthma, were increased in abr(-/-) mice, but adoptive transfer of this cell type from immunized mice to naive controls, followed by CRA challenge, showed that eosinophils are not primarily responsible for differences in airway resistance between controls and abr-null mutants. CD4(+) T cell numbers in the airways of CRA-challenged abr(-/-) mice also were significantly increased compared with controls, as were the Th2 T cell-secreted cytokines IL-4 and IL-5 in total lung. Interestingly, when control and abr(-/-) CD4(+) T cells from CRA-immunized mice were transferred to wild-type animals, airway resistance upon challenge with CRA was significantly higher in mice transplanted with T cells lacking Abr function. CD4(+) T cells from CRA-immunized and challenged abr(-/-) mice contained elevated levels of activated GTP-bound Rac compared with wild-type controls. Functionally, abr(-/-) CD4(+) T cells from CRA-exposed mice showed significantly enhanced chemotaxis toward CCL21. These results identify Abr-regulated CD4(+) T cell migration as an important component of severe CRA-evoked allergic asthma in mice.

Airway resistance, inflammation and oxidative stress following exposure to diesel exhaust particle in angiotensin II-induced hypertension in mice

Exposure to particulate matter is a risk factor for respiratory and cardiovascular diseases. However, the mechanisms underlying these effects are not well understood. Here, we compared the impact of diesel exhaust particles (DEP) on airway resistance, inflammation and oxidative stress in normal mice, or mice made hypertensive by implanting osmotic minipump infusing angiotensin II. On day 13 after the onset of infusion, angiotensin II induced significant increase in heart rate (P<0.05) and systolic blood pressure (P<0.0001). On the same day, mice were intratracheally instilled with either DEP (15μg/mouse) or saline. Twenty-four hour later, the measurement of airway reactivity to methacholine (0–10mg/ml) in vivo by a forced oscillation technique showed a significant and dose dependent increase in airway resistance in normotensive mice exposed to DEP compared to those exposed to saline. In hypertensive mice, there was no difference in airway resistance in DEP versus saline exposed mice. However, following exposure to DEP, airway resistance significantly increased in normotensive versus hypertensive mice. Bronchoalveolar lavage (BAL) fluid analysis showed a significant increase in macrophage numbers in normotensive mice exposed to DEP compared to those exposed to saline, and to hypertensive mice exposed to DEP. Neutrophil numbers were significantly increased in both normotensive and hypertensive mice exposed to DEP compared with their respective control groups. Superoxide dismutase activity was significantly decreased following DEP exposure in both normotensive and hypertensive mice compared to their respective controls. However, total proteins, a marker for increase of epithelial permeability, and malondialdehyde, a reflection of lipid peroxidation, were only increased in normotensive mice exposed to DEP. Therefore, our data suggest that DEP do not aggravate airway resistance and inflammation in angiotensin II-induced hypertensive mice. On the contrary, at the dose of DEP and time point investigated, airway resistance, inflammation and oxidative stress are increased in normotensive compared to hypertensive mice.

Gender Differences in Airway Resistance via Impulse Oscillometry at 5Hz in Pediatric Patients

Gender Differences in Airway Resistance via Impulse Oscillometry at 5Hz in Pediatric Patients

No evidence for interstitial lung oedema by extensive pulmonary function testing at 4,559 m

The aim of the present study was to better understand previously reported changes in lung function at high altitude. Comprehensive pulmonary function testing utilising body plethysmography and assessment of changes in closing volume were carried out at sea level and repeatedly over 2 days at high altitude (4,559 m) in 34 mountaineers. In subjects without high-altitude pulmonary oedema (HAPE), there was no significant difference in total lung capacity, forced vital capacity, closing volume and lung compliance between low and high altitude, whereas lung diffusing capacity for carbon monoxide increased at high altitude. Bronchoconstriction at high altitude could be excluded as the cause of changes in closing volume because there was no difference in airway resistance and bronchodilator responsiveness to salbutamol. There were no significant differences in these parameters between mountaineers with and without acute mountain sickness. Mild alveolar oedema on radiographs in HAPE was associated only with minor decreases in forced vital capacity, diffusing capacity and lung compliance and minor increases in closing volume. Comprehensive lung function testing provided no evidence of interstitial pulmonary oedema in mountaineers without HAPE during the first 2 days at 4,559 m. Data obtained in mountaineers with early mild HAPE suggest that these methods may not be sensitive enough for the detection of interstitial pulmonary fluid accumulation.

Effect of Esophageal Acid and Prophylactic Rabeprazole on Performance in Runners

Acid reflux occurs during exercise. The effects of esophageal acid and prophylactic antisecretory treatment on exercise performance are unknown. To determine 1) the effect of esophageal acid perfusion during exercise on pulmonary function and exercise performance, and 2) whether acid suppression with rabeprazole (RAB) 20 mg x d(-1) increases exercise performance during esophageal acid infusion. This was a two-phase study. Twenty-four conditioned runners (11 with heartburn, 13 without) completed phase 1. Sixteen runners with heartburn completed phase 2 (RAB). For phase 1, esophageal evaluation, baseline maximum exertion test, and a standard Bruce protocol maximal stress test were performed. Runners were randomized to sham esophageal infusion (NG tube placed in the distal esophagus, no fluid) or esophageal acid perfusion (0.1 N HCl perfused) during exercise. Subjects were crossed over to the alternate perfusion. For phase 2, runners underwent three sessions with both acid and sham perfusion during running; the sessions were randomly conducted on different days at baseline and 8 and 12 wk of RAB 20 mg. For phase 1, esophageal function and sensitivity were normal. There was no difference in airway resistance or work capacity between groups. The acid-perfusion group significantly decreased time to exhaustion in the no-heartburn group (23.13 to 20.66 min) with a decrease in energy expenditure. For phase 2, time to exhaustion was significantly decreased with acid perfusion at all time points (P < 0.05). Total energy expenditure during exercise was less in each acid-perfusion test. No difference in pulmonary function was present at week 12 versus baseline. Esophageal acid perfusion decreased performance. In runners with heartburn, suppression of endogenous acid secretion did not improve exercise performance. Changes in cardiopulmonary function do not explain the decreased exercise performance during acid perfusion.

Methylprednisolone reduces airway microvascular permeability but not airway resistance induced by N-formylmethionine leucyl-phenylalanine in the rabbit.

The aim of this study was to determine the effect of corticosteroids on the increase in airway microvascular permeability (MVP) and airway resistance induced by N-formylmethionine leucyl-phenylalanine in the rabbit. After pretreatment with methylprednisolone (for 1 day or 1 week) rabbits were nebulized with N-formylmethionine leucyl-phenylalanine and MVP was assessed using the Evans blue dye technique (on the trachea, bronchi and bronchioles), while airway resistance was measured using a volume displacement plethysmograph. There were no significant differences in airway resistance between the steroid treated group and the control group for either steroid treatment regime. The degree of extravasation of Evans blue dye was significantly inhibited in the bronchioles after both the 1-day and 1-week treatment with methylprednisolone. There were no significant differences in MVP in the trachea or bronchi between the treated groups and the control groups. These results show that methylprednisolone can significantly reduce N-formylmethionine leucyl-phenylalanine-induced MVP without affecting airway resistance.

Gender differences in airway resistance during sleep

At the onset of non-rapid-eye-movement (NREM) sleep there is a fall in ventilation and an increase in upper airway resistance (UAR). In healthy men there is a progressive increase in UAR as NREM sleep deepens. This study compared the pattern of change in UAR and ventilation in 14 men and 14 women (aged 18-25 yr) both during sleep onset and over the NREM phase of a sleep cycle (from wakefulness to slow-wave sleep). During sleep onset, fluctuations between electroencephalographic alpha and theta activity were associated with mean alterations in inspiratory minute ventilation and UAR of between 1 and 4.5 l/min and between 0.70 and 5.0 cmH2O . l-1 . s, respectively, with no significant effect of gender on either change (P > 0.05). During NREM sleep, however, the increment in UAR was larger in men than in women (P < 0.01), such that the mean levels of UAR at peak flow reached during slow-wave sleep were approximately 25 and 10 cmH2O . l-1 . s in men and women, respectively. We speculate that the greater increase in UAR in healthy young men may represent a gender-related susceptibility to sleep-disordered breathing that, in conjunction with other predisposing factors, may contribute to the development of obstructive sleep apnea.

Differential lung ventilation: Applications beyond the operating room

Mechanical ventilatory support in the setting of unilateral lung disease offers unique problems in management. When the difference in airway resistance or lung compliance between the two lungs is exaggerated, conventional mechanical ventilation might lead to preferential ventilation with hyperexpansion of one lung and gradual collapse of the other. Differential ventilation has been advocated to avert this problem. We illustrate the use of this technique in the management of two patients with different underlying pathologic conditions.

Human exposure to 3-carene by inhalation: Toxicokinetics, effects on pulmonary function and occurrence of irritative and CNS symptoms

Terpenes, especially 3-carene, may irritate the skin and mucous membranes and prolonged exposure may result in allergic contact dermatitis or chronic lung function impairment. The toxicokinetics of 3-carene were studied in human volunteers exposed by inhalation (2 hr 50 W) in an exposure chamber on three occasions. The exposure concentrations were approximately 10, 225, and 450 mg/m3 3-carene. The relative pulmonary uptake was high, approximately 70% for the higher exposure levels. Total uptake increased linearly with increasing exposure. The blood clearance of 3-carene observed in this study, 0.9 liter.kg-1.hr-1, indicates that 3-carene is fairly readily metabolized. About 3% of the total uptake was eliminated unchanged via the lungs while less than 0.001% was eliminated in the urine after the end of exposure. A long half time in blood was observed in the terminal phase which indicates a high affinity to adipose tissues. A statistically significant divergence between ratings of irritation during the high exposure level and during the medium and control levels was observed. The difference in airway resistance after exposure to a high concentration of 3-carene compared to control level was not significant (P = 0.02).

The effects of theophylline on the physical performance and work capacity of well-trained athletes

Theophylline, a pharmacologic agent presently permitted during international sporting competition, has come under scrutiny because of the suggestion that it may be ergogenic. This study examined the effects of serum theophylline levels of 10 to 20 mg/L and the administration of a placebo on selected measures of physical performance and work capacity to determine any ergogenic outcomes. Seven male and three female elite athletes from a variety of team sports and aged 18 to 30 years participated in the study. The variables measured were height, mass, maximal oxygen consumption, muscular endurance, muscular power, muscular strength, FVC, FEV 1, and reaction time. When the scores obtained after ingestion of theophylline and a placebo with a double-blind, crossover technique were compared, no significant difference was found for any of these variables. A two-way analysis of variance of FEV 1 scores obtained before and after maximal exercise revealed no significant “F” ratios. This indicated that none of these trained athletes demonstrated exercise-induced asthma and that there was no difference in airway resistance after maximal exercise while they were under the influence of theophylline or placebo. We conclude that no ergogenic effects were attributable to theophylline therapy which should therefore remain an acceptable means of management of athletes with asthma participating in international sporting events.

Ventilation and arousal responses to hypercapnia in normal sleeping humans.

We measured arousal and ventilatory responses to rebreathing from a small bag, initially approximately 7% CO2 in 40% O2, via a nose mask in 13 normal human adults. With deepening non-rapid-eye-movement sleep (NREM), males aroused at increasing alveolar PCO2 (mean +/- SE: stage II 58.6 +/- 1.7, stage III 61.2 +/- 1.0, stage IV 63.8 +/- 0.8 Torr), whereas in rapid-eye-movement sleep (REM), arousal alveolar PCO2 was 57.7 +/- 0.7 Torr, i.e., much lower than in stage III and IV NREM. Females showed no significant change in arousal alveolar PCO2, (II 57.6 +/- 0.9, III 57.3 +/- 1.3, IV 59.4 +/- 0.9, REM 56.3 +/- 1.0 Torr). Male ventilatory response was 2.5 +/- 0.1 (SE) 1 X min-1 X Torr-1 and fell by 49% in NREM (1.29 +/- 0.13) and by 69% in REM (0.78 +/- 0.18). Female response was little affected by state, being similar to male NREM response (wake 1.39 +/- 0.14, NREM 1.40 +/- 0.13, REM 1.11 +/- 0.26 1 X min-1 X Torr-1). In NREM tests, there was no change in sleep state until arousal, whereas in REM, subjects awoke abruptly with the onset of rebreathing (11 cases), showed a transient arousal with onset but continued in REM until final arousal (21 cases), or changed to NREM at onset (2 cases). These arousal results contrast sharply with findings in tracheostomized dogs and in obstructive sleep apnea syndrome, where asphyxic arousal is later in REM than in NREM, suggesting that the events at test onset in REM in the present study may be related to upper airway sensitivity to CO2 specific to REM.

Inspiratory flow rate and ventilation distribution in normal subjects and in patients with simple chronic bronchitis.

1. Seated subjects stopped ventilation briefly at end expiration while a 5 ml bolus of 133Xe was injected close to the mouth. They then inspired air at different flow rates and the distribution of radioactivity in the lungs was measured with a scanning technique during a period of breath-holding at maximal inspiration. 2. In five normal subjects the dependent zones received a greater fraction of the 133Xe bolus than the apex during slow inspirations, but apical distribution exceeded basal for fast inspirations. The volume history of the lungs before the bolus injection had no effect on the slow/fast difference in four out of five subjects. 3. In five patients with clinical bronchitis but normal forced expired volume, dependent zone ventilation was much reduced on a slow inspiration compared with normals, but at fast flow rates the distribution was normal. 4. Insofar as the bolus in the fast inspiration was distributed according to regional airway conductances, these results suggest that in normal subjects differences in airway resistance exist between the upper and lower zones of the upright lung. An early abnormality in bronchitis appears to be a reduction of compliance in the dependent zones, as judged from the decrease in basal ventilation on a slow inspiration.