End-expiratory Volume Research Articles

Acute Airway Obstruction Caused by the New Single Use Laryngeal Mask Airway Supreme™

Acute Airway Obstruction Caused by the New Single Use Laryngeal Mask Airway Supreme™

Symptoms and Signs

Dyspnea is a general term used to characterize a range of qualitatively distinct descriptors which may contribute to our understanding of the mechanisms of dyspnea. In general the language of dyspnea complements physiological measurements, essential to a comprehensive understanding of exercise tolerance and dyspnea. Like leg exercise, arm exercise is associated with increased dynamic hyperinflation which correlates with increases in dyspnea, and arm effort in moderately to severely obstructed patients. These patients speak in an interrupted fashion, unable to sustain long sentence because the downstream excursion in end expiratory lung volume is likely to increase the amount of tidal expiratory flow limitation and dyspnea. Patients often spontaneously employ breathing retraining strategies to relieve dyspnea. Pursed-lip breathing, impacts on dyspnea by decreasing end expiratory volumes of the chest wall. Finally, a method is proposed to quantify the presence and degree of Hoovers sign and evaluate the agreement between clinical and quantitative analysis.

Paradoxical movement of the lower ribcage at rest and during exercise in COPD patients

Paradoxical inward displacement of the costal margin during inspiration is observed in many chronic obstructive pulmonary disease patients at rest but its importance is unclear. The current authors studied 20 patients (forced expiratory volume in one second 32.6+/-11.7, functional residual capacity 186+/-32% predicted) and 10 healthy controls at rest and during symptom-limited incremental exercise. With optoelectronic plethysmography, the phase shift between pulmonary and abdominal ribcage volumes and the percentage of inspiratory time the ribcage compartments moved in opposite directions were quantified, using control data to define the normal range of movement. Eight patients showed lower ribcage inspiratory paradox at rest (P+), while 12 patients did not (P-). This was unrelated to resting lung function or exercise tolerance. Total end-expiratory chest wall volume (EEV(cw)) increased immediately when exercise began in P+ patients, but later in exercise in P- patients. This difference in EEV(cw) was mainly due to a greater increase of end-expiratory pulmonary ribcage volume in P+ patients. During exercise, dyspnoea increased similarly in the two groups, while leg effort increased more markedly in the patients without paradox. In conclusion, lower ribcage paradox at rest is reproducible and associated with early-onset hyperinflation of the chest wall and predominant dyspnoea at end-exercise. When paradox is absent, the sense of leg effort becomes a more important symptom limiting exercise.

Relative impact of respiratory muscle activity on tidal flow and end expiratory volume in healthy neonates

It has been suggested that infants dynamically regulate their tidal flow and end-expiratory volume level. The interaction between muscle activity, flow and lung volume in spontaneously sleeping neonates is poorly studied, since it requires the assessment of transcutaneous electromyography of respiratory muscles (rEMG) in matched comparison to lung function measurements. After determining feasibility and repeatability of rEMG in 20 spontaneously sleeping healthy neonates, we measured the relative impact of intercostal and diaphragmatic EMG activity in direct comparison to the resulting tidal flow and FRC. We found good feasibility, repeatability and correlation of timing indices between rEMG activity and flow. The rEMG amplitude was significantly dependent on the resistive load of the face mask. Diaphragm and intercostal muscle activity commenced prior to the onset of flow and remained active during the expiratory cycle. The relative contribution of intercostal and diaphragmatic activity to flow was variable and changed dynamically. Using matched rEMG, air flow and lung volume measurements, we have found good feasibility and repeatability of intercostal and diaphragm rEMG measurements and provide the first quantitative measures of the temporal relationship between muscle activity and flow in spontaneously sleeping healthy neonates. Lung mechanical function is dynamically regulated and adapts on a breath to breath basis. So, non-invasive rEMG measurements alone or in combination with lung function might provide a more comprehensive picture of pulmonary mechanics in future studies. The data describing the timing of EMG and flow may be important for future studies of EMG triggered mechanical ventilation.

From Liquid to Air: Breathing after Birth

The first breaths after birth are characterized by a rapid transition from liquid- to air-filled lungs. Air is drawn into the lung during inspiration, and some remains at end expiration to establish an end-expiratory gas volume or functional residual capacity (FRC). This is usually marked by a cry, often misinterpreted as a protest from the baby. Some infants, especially those born preterm, require respiratory support during this transitional phase. To do this effectively, we need to understand the normal physiological processes occurring at this time. Sometimes it can be difficult to aerate the lungs of preterm infants with intermittent positive pressure ventilation with pressures recommended in international guidelines, particularly when the infant does not breathe and aeration is completely dependent on the inflation pressures. Studies have shown that intermittent positive pressure ventilation should be performed without high tidal volumes to avoid damaging the lung while establishing the FRC. 1,2 However, since the use of antenatal steroids, more very preterm infants breathe spontaneously at birth, only requiring support from nasal continuous positive airway pressure. Understanding the normal spontaneous breathing pattern after birth is essential for developing safe, efficient ventilatory strategies when breathing is inadequate. Numerous physiological studies immediately after birth of spontaneously breathing infants were published between 1960 and 1986. 3-10 However, little new data are currently available on this topic, reflecting the difficulties of performing these studies. This review will discuss what happens during the first breaths of air with the emphasis on where the liquid goes and the current knowledge about the spontaneous breathing pattern adopted by infants immediately after birth.

Chest wall volume regulation during exercise in COPD patients with GOLD stages II to IV

The present study investigated how end-expiratory ribcage and abdominal volume regulation during exercise is related to the degree of dynamic chest wall hyperinflation in patients with different spirometric severity of chronic obstructive pulmonary disease (COPD) based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification. In total, 42 COPD patients and 11 age-matched healthy subjects were studied during a ramp-incremental cycling test to the limit of tolerance (W(peak)). Volume variations of the chest wall (at end expiration (EEV(cw)) and end inspiration) and its compartments (ribcage (V(rc)) and abdominal (V(ab))) were computed by optoelectronic plethysmography. At W(peak), only patients in GOLD stages III and IV exhibited a significant increase in EEV(cw) (increase of 454+/-509 and 562+/-363 mL, respectively). These patients did not significantly reduce end-expiratory V(ab), whereas patients in GOLD stage II resembled healthy subjects with significantly reduced end-expiratory V(ab) (decrease of 287+/-350 mL). In patients, the greater the increase in EEV(cw) at W(peak), the smaller the reductions in end-expiratory V(ab) and the greater the increase in end-expiratory V(rc). In chronic obstructive pulmonary disease patients with different spirometric disease severity, greater degrees of exercise-induced dynamic chest wall hyperinflation were accompanied by lower degrees of end-expiratory abdominal volume displacement and larger increases in end-expiratory ribcage volume.

Fentanyl decreases end-expiratory lung volume in patients anaesthetized with sevoflurane

In patients breathing spontaneously during anaesthesia, expiratory muscle activity can be a prominent feature. This activity is triggered or exaggerated by opioid administration, which causes a prompt increase in intra-abdominal pressure. The effect of this increased expiratory activity on end-expiratory lung volume is not described. Nine patients having minor gynaecological procedures were studied during stable anaesthetic conditions, breathing sevoflurane (end tidal 2.6%) through a laryngeal mask airway, in a circle system. The spill valve was closed and the fresh gas flow was temporarily reduced to approximate the oxygen uptake. The volume of the reservoir bag was then measured by placing it in a hinged, wedge-shaped container. Fentanyl (0.5 microg kg(-1) ideal body weight) was given after 1 min of stable recording, and the change in end-expiratory volume measured after 3 min. End-expiratory lung volume decreased in all patients by 160 (111) ml (mean, SD) (P<0.01). The decrease did not relate to obesity. During sevoflurane anaesthesia, fentanyl causes a rapid reduction in functional residual capacity. This is caused by increased activity of expiratory muscles and an increase in intra-abdominal pressure.

The Effect of Lung Expansion and Positive End-Expiratory Pressure on Respiratory Mechanics in Anesthetized Children

Imaging studies have shown that general anesthesia in children results in atelectasis. Lung recruitment total lung capacity (TLC) maneuvers plus positive end-expiratory pressure (PEEP) are effective in preventing atelectasis. However, physiological changes in children during general anesthesia have not been elucidated. In eight anesthetized and mechanically ventilated children (median age: 3.5 years; range: 2.3-6.5), we measured static respiratory system elastance (E(st)), flow resistance (R(int)), and elastance and resistance components resulting from tissue viscoelasticity (deltaE and deltaR, respectively) using the constant inflow, end-inspiratory occlusion method preceded by TLC maneuvers, both with zero PEEP (ZEEP) and PEEP (5 cm H2O) for comparison. With constant inspiratory flow V(I) and ZEEP, increases in end-inspiratory lung volume above relaxation volume (tidal volume, V(T)) from 8 to 20 mL x kg(-1) resulted in decreases in E(st) from 1.06 to 0.82 cm H2O x mL(-1) x kg, deltaE from 0.16 to 0.09, and R(int) from 0.13 to 0.11 cm H2O x mL(-1) x s x kg, whereas deltaR increased from 0.08 to 0.12 (P < 0.05). Similar relationships were found with PEEP. Increases in V(I) (8 to 26 mL x s(-1) x kg) with constant V(T) and ZEEP resulted in decreases in E(st) from 1.09 to 0.9 and deltaR from 0.17 to 0.06 (P < 0.01), whereas deltaE and R(int) did not change. There was a similar flow and volume dependence of elastance and resistance with PEEP. The observed steady decreases in E(st) with increasing V(T) (up to 16 mL/kg with PEEP) indicate marked reductions in end-expiratory relaxation volume (functional residual capacity) even with PEEP. Similarity in results with ZEEP and PEEP suggests that TLC-maneuvers and O2-N2 ventilation prevented airway closure throughout the study.

Raising End-Expiratory Volume Relieves Air Hunger in Mechanically Ventilated Healthy Adults.

Raising End-Expiratory Volume Relieves Air Hunger in Mechanically Ventilated Healthy Adults.

High-resolution computed tomography evaluation of airway distensibility in asthmatic and healthy subjects

Airway-wall remodelling may result in reduced airway distensibility in bronchial asthma. This study evaluated the baseline airway calibre and distensibility in asthmatic patients by means of high-resolution computed tomography (HRCT). We studied seven patients (two men, age range 36-69 years) with chronic asthma [forced expiratory volume in the first second (FEV(1)) range: 30%-87% of predicted; FEV1/forced vital capacity (FVC) range 48%-75% of predicted) under stable clinical conditions and six healthy control subjects (three men, age range 29-50 years). In all subjects, HRCT scanning, at suspended end-expiratory volume, was performed at rest and during ventilation with 6 and 12 cmH(2)O by nasal insufflation with continuous positive airway pressure (nCPAP), both at baseline and after inhalation of 200 mug oxitropium bromide metered dose inhaler (MDI). External and lumen diameter (mm) of the right apical upper lobe bronchus were measured in all HRCT scans. In asthmatics, 12 cmH(2)O insufflation significantly changed baseline lumen (3.3+/-0.7 mm vs. 3.8+/-0.6 mm; p<0.01) and external diameter (6.2+/-0.9 mm vs. 6.7+/-0.8 mm; p<0.05), whereas in healthy controls, both 6 and 12 cmH(2)O insufflation significantly changed baseline lumen diameter (4.0+/-1.6 mm vs. 4.8+/-1.6 mm and 4.7+/-1.7 mm; p<0.01). In asthmatic patients, oxitropium bromide inhalation significantly changed baseline lumen diameter (3.3+/-0.7 mm vs. 4.4+/-0.6 mm; p<0.05), whereas the application of 6 or 12 cmH(2)O insufflation did not modify any bronchial diameters. In healthy controls, oxitropium bromide inhalation significantly changed baseline lumen diameter (4.0+/-.6 mm vs. 5+/-1.5 mm; p<0.05). The application of 12 cmH(2)O but not of 6 cmH(2)O induced a significant change in lumen diameter (5.0+/-1.5 mm vs. 6,0+/-1.6 mm; p<0.05). Our results show that airway distensibility in asthmatic patients, as assessed by HRCT, can differ compared with that of healthy controls. HRCT can provide useful information on airway distensibility.

Chest wall kinematics during voluntary cough in neuromuscular patients

Muscular diseases are characterized by progressive loss of muscle strength, resulting in cough ineffectiveness with its deleterious effects on the respiratory system. Assessment of cough effectiveness is therefore a prominent component of the clinical evaluation and respiratory care in these patients. Owing to uneven distribution of muscle weakness in neuromuscular patients, we hypothesized that forces acting on the chest wall may impact on the compartmental distribution of gas volume resulting in a decrease in cough effectiveness. Pulmonary volumes, respiratory muscle strength, peak cough flow and chest wall kinematics by optoelectronic plethysmography were studied in 8 patients and 12 healthy subjects as controls. Chest wall volume was modeled as the sum of volumes of the rib cage and abdomen. The plot of the volumes of upper to lower rib cage allowed assessment of rib cage distortion. Unlike controls, patients were unable to reduce end-expiratory chest wall volume, and exhibited greater rib cage distortion during cough. Peak cough flow was negatively correlated with rib cage distortion (the greater the former, the smaller the latter), but not with respiratory muscle strength. In conclusion, insufficient deflation of chest wall compartments and marked rib cage distortion resulted in cough ineffectiveness in these neuromuscular patients.

Respiratory-Gated Helical Computed Tomography of Lung: Reproducibility of Small Volumes in an Ex Vivo Model

Motion-adapted radiotherapy with gated irradiation or tracking of tumor positions requires dedicated imaging techniques such as four-dimensional (4D) helical computed tomography (CT) for patient selection and treatment planning. The objective was to evaluate the reproducibility of spatial information for small objects on respiratory-gated 4D helical CT using computer-assisted volumetry of lung nodules in a ventilated ex vivo system. Five porcine lungs were inflated inside a chest phantom and prepared with 55 artificial nodules (mean diameter, 8.4 mm +/- 1.8). The lungs were respirated by a flexible diaphragm and scanned with 40-row detector CT (collimation, 24 x 1.2 mm; pitch, 0.1; rotation time, 1 s; slice thickness, 1.5 mm; increment, 0.8 mm). The 4D-CT scans acquired during respiration (eight per minute) and reconstructed at 0-100% inspiration and equivalent static scans were scored for motion-related artifacts (0 or absent to 3 or relevant). The reproducibility of nodule volumetry (three readers) was assessed using the variation coefficient (VC). The mean volumes from the static and dynamic inspiratory scans were equal (364.9 and 360.8 mm3, respectively, p = 0.24). The static and dynamic end-expiratory volumes were slightly greater (371.9 and 369.7 mm3, respectively, p = 0.019). The VC for volumetry (static) was 3.1%, with no significant difference between 20 apical and 20 caudal nodules (2.6% and 3.5%, p = 0.25). In dynamic scans, the VC was greater (3.9%, p = 0.004; apical and caudal, 2.6% and 4.9%; p = 0.004), with a significant difference between static and dynamic in the 20 caudal nodules (3.5% and 4.9%, p = 0.015). This was consistent with greater motion-related artifacts and image noise at the diaphragm (p <0.05). The VC for interobserver variability was 0.6%. Residual motion-related artifacts had only minimal influence on volumetry of small solid lesions. This indicates a high reproducibility of spatial information for small objects in low pitch helical 4D-CT reconstructions.

Minimally invasive lung volume reduction treated with bronchi occlusion emphysema model

目的 评价钢圈加生物胶封堵法治疗兔肺气肿的有效性和可行性.方法 制备兔肺气肿模型16只,分为封堵组10只,对照组6只.封堵组兔行钢圈加生物胶法封堵两前叶支气管,分别测量兔气肿前、气肿后、术后1周及4周4个时间点2组的静态气道压(Pmax)、最大呼气流量(PEF)、呼气末肺容积(EEV)及血氧分压(PO2),并观察封堵组钢圈咳出(或移位)和肺萎陷情况.结果 封堵组的Pmax在气肿前、后分别为(20.0±1.3)和(17.1±1.4)cm H2O(1 cm H2O=0.098 kPa).术后1周时封堵组Pmax为(19.2±1.4)cm H2O,对照组为(17.1±1.5)cm H2O(F=6.68,P＜0.05).术后4周时封堵组Pmax为(19.2±1.4)cm H2O,对照组为(16.6±1.2)cm H2O(F=12.10,P＜0.01);封堵组EEV为(86±8)ml,对照组为(96±4)ml(F=5.72,P＜0.05).封堵组封堵术后1周及4周Pmax均比气肿后高(P值均＜0.01);气肿后EEV比气肿前增加(P＜0.01),术后1周比气肿后减少(P＜0.05).结论 应用钢圈加生物胶封堵法进行兔肺减容术,能改善肺功能,且这种作用能较长期存在。

End-expiratory and tidal volumes measured in conscious mice using single projection x-ray images

The evaluation of airway resistance (R(aw)) in conscious mice requires both end-expiratory (V(e)) and tidal volumes (V(t)) (Lai-Fook SJ and Lai YL. J Appl Physiol 98: 2204-2218, 2005). In anesthetized BALB/c mice we measured lung area (A(L)) from ventral-to-dorsal x-ray images taken at FRC (V(e)) and after air inflation with 0.25 and 0.50 ml (DeltaV(L)). Total lung volume (V(L)) described by equation: V(L) = DeltaV(L) + V(FRC) = KA(L)(1.5) assumed uniform (isotropic) inflation. Total V(FRC) averaged 0.55 ml, consisting of 0.10 ml tissue, 0.21 ml blood and 0.24 ml air. K averaged 1.84. In conscious mice in a sealed box, we measured the peak-to-peak box pressure excursions (DeltaP(b)) and x-rays during several cycles. K was used to convert measured A(L)(1.5) to V(L) values. We calculated V(e) and V(t) from the plot of V(L) vs. cos(alpha - phi). Phase angle alpha was the minimum point of the P(b) cycle to the x-ray exposure. Phase difference between the P(b) and V(L) cycles (phi) was measured from DeltaP(b) values using both room- and body-temperature humidified box air. A similar analysis was used after aerosol exposures to bronchoconstrictor methacholine (Mch), except that phi depended also on increased R(aw). In conscious mice, V(e) (0.24 ml) doubled after Mch (50-125 mg/ml) aerosol exposure with constant V(t), frequency (f), DeltaP(b), and R(aw). In anesthetized mice, in addition to an increased V(e), repeated 100 mg/ml Mch exposures increased both DeltaP(b) and R(aw) and decreased f to apnea in 10 min. Thus conscious mice adapted to Mch by limiting R(aw), while anesthesia resulted in airway closure followed by diaphragm fatigue and failure.

Marcos F. Vidal Melo, M.D., Ph.D., Recipient of the 2007 Presidential Scholar Award

Marcos F. Vidal Melo, M.D., Ph.D., Recipient of the 2007 Presidential Scholar Award

Assessment of regional lung recruitment and derecruitment during a PEEP trial based on electrical impedance tomography

To investigate whether electrical impedance tomography (EIT) is capable of monitoring regional lung recruitment and lung collapse during a positive end-expiratory pressure (PEEP) trial. Experimental animal study of acute lung injury. Six pigs with saline-lavage-induced acute lung injury. An incremental and decremental PEEP trial at ten pressure levels was performed. Ventilatory, gas exchange, and hemodynamic parameters were automatically recorded. EIT and computed tomography (CT) scans of the same slice were simultaneously taken at each PEEP level. A significant correlation between EIT and CT analyses of end-expiratory gas volumes (r=0.98 up to 0.99) and tidal volumes (r=0.55 up to r=0.88) could be demonstrated. Changes in global and regional tidal volumes and arterial oxygenation (PaO2/FiO2) demonstrated recruitment/derecruitment during the trial, but at different onsets. During the decremental trial, derecruitment first occurred in dependent lung areas. This was indicated by lowered regional tidal volumes measured in this area and by a decrease of PaO2/FiO2. At the same time, the global tidal volume still continued to increase, because the increase of ventilation of the non-dependent areas was higher than the loss in the dependent areas. This indicates that opposing regional changes might cancel each other out when combined in a global parameter. EIT is suitable for monitoring the dynamic effects of PEEP variations on the regional change of tidal volume. It is superior to global ventilation parameters in assessing the beginning of alveolar recruitment and lung collapse.

Acute effects of thixotropy conditioning of inspiratory muscles on end-expiratory chest wall volume

Acute effects of thixotropy conditioning of inspiratory muscles on end-expiratory chest wall volume

Heavy breathing

Heavy breathing

Raising end-expiratory volume relieves air hunger in mechanically ventilated healthy adults

Air hunger is an unpleasant urge to breathe and a distressing respiratory symptom of cardiopulmonary patients. An increase in tidal volume relieves air hunger, possibly by increasing pulmonary stretch receptor cycle amplitude. The purpose of this study was to determine whether increasing end-expiratory volume (EEV) also relieves air hunger. Six healthy volunteers (3 women, 31 +/- 4 yr old) were mechanically ventilated via a mouthpiece (12 breaths/min, constant end-tidal Pco(2)) at high minute ventilation (Ve; 12 +/- 2 l/min, control) and low Ve (6 +/- 1 l/min, air hunger). EEV was raised to approximately 150, 400, 725, and 1,000 ml by increasing positive end-expiratory pressure (PEEP) to 2, 4, 6, and 8 cmH(2)O, respectively, for 1 min during high and low Ve. The protocol was repeated with the subjects in the seated and supine positions to test for the effect of shifting baseline EEV. Air hunger intensity was rated at the end of each breath on a visual analog scale. The increase in EEV was the same in the seated and supine positions; however, air hunger was reduced to a greater extent in the seated position (13, 30, 31, and 44% seated vs. 3, 9, 23, and 27% supine at 2, 4, 6, and 8 cmH(2)O PEEP, respectively, P < 0.05). Removing PEEP produced a slight increase in air hunger that was greater than pre-PEEP levels (P < 0.05). Air hunger is relieved by increases in EEV and tidal volume (presumably via an increase in mean pulmonary stretch receptor activity and cycle amplitude, respectively).

Speaking-Related Dyspnea in Healthy Adults

To reveal the qualities and intensity of speaking-related dyspnea in healthy adults under conditions of high ventilatory drive, in which the behavioral and metabolic control of breathing must compete. Eleven adults read aloud while breathing different levels of inspired carbon dioxide (CO(2)). After the highest level, participants provided unguided descriptions of their experiences and then selected descriptors from a list. On a subsequent day, participants read aloud while breathing high CO(2) as before, then rated air hunger, physical exertion, and mental effort (with definitions provided). Recordings were made of ventilation (with respiratory magnetometers), end-tidal partial pressure of CO(2), transcutaneous PCO(2), oxygen saturation, noninvasive blood pressure, heart rate, and the speech signal. Unguided descriptions were found to reflect the qualities of air hunger, physical exertion (work), mental effort, and speech-related observations. As CO(2) stimulus strength increased, participants experienced increased perception of air hunger, physical exertion, and mental effort. Simultaneous increases were observed in ventilation, tidal volume, end-inspiratory and end-expiratory volumes, expiratory flow during speaking, nonlinguistic junctures, and nonspeech expirations. Two qualities of speaking-related dyspnea--air hunger and physical exertion--are the same as those reported for many other types of nonspeech dyspnea conditions and, therefore, may share the same physiological mechanisms. The mental effort quality associated with speaking-related dyspnea may reflect a conscious drive to balance speech requirements and ventilatory demands. These findings have implications for developing better ways to evaluate and manage clients with respiratory-based speech problems.