Functional residual capacity

Respiratory mechanics, chest wall configuration, and lung morphometry were determined in rats before and at 30 (PTX.30) and 60 (PTX.60) min after pneumothorax induction (intrathoracic injection of 8 ml of room air; 50% collapse). Pneumothorax increased respiratory system and lung elastances and viscoelastic/inhomogeneous pressures in both groups, but respiratory system and lung resistive pressures increased only in PTX.60 group. Antero-posterior diameters at the third intercostal space and xiphoid levels, circumference at xiphoid level, and thoracic cephalo-caudal diameter increased significantly after pneumothorax induction independently of temporal evolution. In both groups lung collapse, hyperinflation, and interstitial and alveolar edema were present. Additionally, in PTX.60 group the central airways calibre diminished in relation to PTX.30. In conclusion pneumothorax yields changes in respiratory system and lung elastic and viscoelastic parameters, which are related to alveolar collapse and edema, respectively. Temporal evolution of pneumothorax also leads to changes in lung resistive pressure, probably because of airway narrowing.

Body plethysmography allows to assess functional residual capacity (FRC(pleth)) and specific airway resistance (sRaw) as primary measures. In combination with deep expirations and inspirations, total lung capacity (TLC) and residual volume (RV) can be determined. Airway resistance (Raw) is calculated as the ratio of sRaw to FRC(pleth). Raw is a measure of airway obstruction and indicates the alveolar pressure needed to establish a flow rate of 1 L s(-1). In contrast, sRaw can be interpreted as the work to be performed by volume displacement to establish this flow rate. These measures represent different functional aspects and should both be considered. The measurement relies on the fact that generation of airflow needs generation of pressure. Pressure generation means that a mass of air is compressed or decompressed relative to its equilibrium volume. This difference is called "shift volume". As the body box is sealed and has rigid walls, its free volume experiences the sa...

This study aimed to evaluate the involvement of airway cross-sectional area and shape, and functional residual capacity (FRC), in the genesis of obstructive sleep apnoea (OSA) in patients with supine-predominant OSA. Three groups were recruited: (i) supine OSA, defined as a supine apnoea-hyponoea index (AHI) at least twice that of the non-supine AHI; (ii) rapid eye movement (REM) OSA, defined as REM AHI at least twice the non-REM AHI and also selected to have supine AHI less than twice that of the non-supine AHI (i.e. to be non-positional); and (iii) no OSA, defined as an AHI less than five events per hour. The groups were matched for age, gender and body mass index. Patients underwent four-dimensional computed tomography scanning of the upper airway in the supine and lateral decubitus positions. FRC was measured in the seated, supine and lateral decubitus positions. Patients with supine OSA demonstrated a significant decrease in FRC of 340 mL (P = 0.026) when moving from the latera...

In metropolitan cities, rapidly increased new construction development activities and every new development has its own traffic impact which can be affect the surrounding road network. In this research we study the systematic method to analyze traffic impact of a new construction development which can generate and attract traffic demand around the road network according to survey and analysis of existing traffic condition. To analyze, Regression method is used; evaluation of traffic growth rate is done according to past traffic data and forecast future traffic condition after development in terms of Level of service (LOS) of road. The distribution of traffic volume orderly to make sure the balance of the project won't affect the existing traffic condition. The traffic impact analysis can help to forecast the traffic volume activities for later on years, basically to investigate the different traffic elements having sway on movement conditions after improvement. Traffic assignment is involving the pattern, which is generated traffic will be distributed on according to residual capacity of surrounding roads. The traffic impact research can help to detect projected traffic condition, thus planning is made to provide facilities to minimize the traffic problems after complete commercial developments. An attempt has been done to reduce the traffic impact be mitigated by staggered office timing and carpooling 30% reduced generation and attraction traffic of Corporate Park, Carpooling introducing some AC buses and transportation facilities. Due to staggered office timing and carpooling have been observed and the traffic volume will be diverted to the proposed transportation amenities constructed which is front of study area thus the traffic condition will be reduced and LOS will be improved.

Mechanical ventilation of the newborn infant has increased neonatal survival. However, this increased survival has come at the expense of increased morbidity, in the form of bronchopulmonary dysplasia, and at the cost of an expensive technology. Continuous positive airway pressure (CPAP) is accepted as conferring clinical benefit in supporting the recently extubated preterm infant and in the management of apnea of prematurity. Attention is now being drawn to physiologic and clinical evidence to support CPAP use, with or without early surfactant, as a primary treatment of hyaline membrane disease. The purpose of this review is to explore these proposed benefits of non invasive ventilation and place them in the context of current clinical evidence.

The mechanism by which deep inspirations protect against increased airway responsiveness in nonasthmatic subjects is not known. The aim was to investigate the role of airway closure and airway narrowing in deep inspiration bronchoprotection. Twelve nonasthmatic and nine asthmatic subjects avoided deep inspirations (DI) for 20 min, then took five DI expired to functional residual capaciy (DI-FRC) or, on a separate day, no DI (no DI) before inhaling a single dose of methacholine. On another day, eight nonasthmatic subjects took five DI expired to residual volume (DI-RV). Peripheral airway function was measured by respiratory system reactance (Xrs), using the forced oscillation technique, and by forced vital capacity (FVC) as an index of airway closure. Respiratory system resistance (Rrs) and forced expiratory volume in 1 s (FEV1)/FVC were measured as indexes of airway narrowing. In nonasthmatic subjects, DI-FRC reduced the response measured by FEV1 ( P = 0.019), Xrs ( P = 0.02), and F...

We examined pulmonary diffusing capacity (D(LCO)) and its partition in pulmonary vascular diseases without evident parenchymal disease to assess the pattern and proportionality of change in membrane diffusion (D(m)) and capillary blood volume (V(c)). Disproportionate reduction in D(m) relative to V(c) (low D(m)/V(c)) in these diseases has been attributed to associated alveolar membrane/parenchymal disease, thus providing a potentially important diagnostic tool. Diseases included: idiopathic pulmonary arterial hypertension (n=6), chronic thromboembolic disease (n=5), and intravenous drug use (n=14), providing a spectrum of pulmonary vascular diseases. V(c) and D(m) were determined as described by Roughton and Forster. All diseases showed a reduced V(c) (59+/-10, 69+/-14, 71+/-21 % predicted, respectively) and D(m) (76+/-22, 53+/-19, 63+/-16 % predicted, respectively) with no differences between groups (p>0.05). Disproportionate reduction of D(m) (D(m)/V(c) % predicted <1) was s...

In 10 anesthetized adult rabbits, we studied the effect of spontaneous breathing and positive pressure ventilation on pleural pressure on the costal lung surface (Ppl) and in the zone of apposition of the rib cage to the diaphragm (Papp). Ppl and Papp were measured by rib capsules installed in the 5th or 6th rib and 11th or 12th rib, respectively. Esophageal (Pes) and gastric (Pga) pressures were measured with air-filled balloons. At end expiration (functional residual capacity), Ppl was subatmospheric (−2.5 ± 1.4 cm H2O), decreased during spontaneous inspiration, and was in phase with Pes. In contrast, Papp was above atmospheric pressure (2.1 ± 1.8 cm H2O), increased during inspiration, and was in phase with Pga. Papp lagged Ppl by 180° during spontaneous inspiration but was in phase with Ppl during mechanical ventilation. Changes in Ppl (ΔPpl) during inspiration were greater in magnitude than either ΔPapp or ΔPga. Changes in transdiaphragmatic pressure in the zone of apposition (ΔPga - ΔPapp) were near zero (−0.4 ± 0.3 cm H2O), much smaller in magnitude than those (ΔPga - ΔPpl) associated with the lung (3.0 ± 1.5 cm H2O). These results are consistent with the concept that during breathing, abdominal pressure is transmitted to the zone of apposition of the rib cage to the abdomen. During spontaneous breathing at rest, the pleural space in the zone of apposition is mechanically independent of the pleural space associated with the lung.

Pressure-volume (PV) curves constructed over the entire lung volume range can reliably detect functional changes in mouse models of lung diseases. In the present study, we constructed full-range PV curves in healthy and elastase-treated mice using either a classic manually-operated technique or an automated approach using a computer-controlled piston ventilator (flexiVent FX; SCIREQ Inc, Montreal, Qc, Canada). On the day of the experiment, subjects were anaesthetized, tracheotomized and mechanically ventilated. Following an initial respiratory mechanics scan and degassing of the lungs with 100% O2, full-range PV curves were constructed using either the classic or the automated technique. In control mice, superimposable curves were obtained and statistical equivalence was attained between the two methodologies. In the elastase-treated ones, where significant changes in respiratory mechanics and lung volumes were expected, very small differences were observed between the two technique...