Functional Residual Capacity Level Research Articles

Expression and localization of the MMP inhibitor RECK in a rat model of COPD: its involvement in the development of COPD.

To unravel the potential function of reversion-inducing cysteine-rich protein with Kazal motifs (RECK) as the matrix metalloproteinase (MMP) inhibitor in the development of chronic obstructive pulmonary disease (COPD). Twelve specific pathogen-free Sprague Dawley rats were randomly assigned to the control cohort (n = 6) or the COPD cohort (n = 6). COPD model was developed by tobacco smoke exposure. Functional residual capacity (FRC), static lung compliance (Cchord), ratio of forced expiratory volume in 0.1 s to forced vital capacity (FEV0.1/FVC), and peak expiratory flow (PEF) were detected by respiratory function tests. Immunohistochemistry was performed to determine the pathological changes as well as the expression and localization of RECK in pulmonary tissue. RECK expression was further quantified by real-time polymerase chain reaction (PCR) and Western blot assays. COPD rats had significantly reduced FEV0.1/FVC% and PEF values but increased FRC and Cchord levels, as compared to the control cohort (p < 0.05). Hematoxylin and eosin (HE) staining indicated typical COPD pathological changes, including leukocyte infiltration, airway thickening, alveoli fusion, etc., in the COPD rats. IHC indicated reduced expression of RECK in the COPD cohort, which was mainly expressed on the epithelium and partly expressed on subepithelial cells and inflammatory cells. Real-time PCR and Western blot assays further revealed the significantly lower expression of RECK in lung tissue from the COPD cohort. RECK is mainly expressed on airway epithelial cells. COPD rats expressed significantly lower RECK levels, indicating that RECK exhibits a protective function in the development of COPD.

Comparison of Ventilator’s Work of Breath Cased on Constant Flow Nasal CPAP Through Pressure Limited and Electronic Feedback Pressure Control Mechanisms in the Treatment of RDS in Neonates Weighing About 1000 Grams

Background: Continuous distending pressure (CDP) is considered as standard care in neonates with decreased pulmonary compliance. Concerns regarding the implementation of non-invasive CDP in a respiratory cycle in order to establish an optimal level of functional residual capacity (FRC) abound in the related literature. Examples include how to manage gas leakage in the interface, no imposed increased work of breath (WOB) on patients and prevention of applying trans-pulmonary pressure levels leading to metabolic acidosis. Following the development of autoflow hardware, pressure control (PC) respiratory pattern was defined in the field of mechanical ventilation (MV) in order to compensate for gas leakage in interface or compensate for pressure drop and increased CDP pressure level in respiratory phases of inspiration and expiration. Objectives: The study aimed at decreasing WOB in neonates with RDS using pressure control-nCPAP. Methods: This study was a retrospective clinical trial performed on 70 neonates weighing about 1000 grams with RDS. Participants were randomly assigned into two respiratory support groups based on the use of pressure limited nCPAP (PL-nCPAP) and pressure control nCPAP (PC-nCPAP). Each group consisted of 35 infants compared in terms of their demographic characteristics, duration of non-invasive respiratory support, rapid shallow breathing (RSB) index, ventilator’s WOB, need for MV, need for surfactant administration, chronic lung diseases, pneumothorax, intra-ventricular hemorrhage (IVH) and death. Results: No significant difference was observed between the mean time of non-invasive respiratory support and the need for MV, between the incidence of pneumothorax and IVH and also between the mortality rate and degree of involvement in chronic lung diseases in the two groups. The mean respiratory ventilation rate of ventilator’s WOB in PC-nCPAP group was significantly higher than that of PL-nCPAP group. The mean RSB index was also significantly higher in PL-nCPAP group than in PC-nCPAP group. Finally, the mean of surfactant administration in PL-nCPAP group was significantly higher than that in PC-nCPAP group. Conclusions: In this study, ventilator’s WOB in PC-nCPAP group, which was significantly higher than that of PL-nCPAP group, can be explained by significantly higher RSB index in PL-nCPAP group and significantly lower mean surfactant prescription in PC-nCPAP group.

Effects of increased functional residual capacity on finger-floor distance in healthy young adults.

[Purpose] To investigate the effect of increased functional residual capacity on the finger-floor distance and to assess spinal curvature in the sagittal plane using the Spinal Mouse in healthy young participants. [Participants and Methods] Thirty-nine healthy volunteers (age=21.2 ± 0.8 years) participated in this study. The finger-floor distance was used to measure trunk flexion and was recorded at the resting expiration level and at 2 different functional residual capacity levels: 1,000 and 2,000 ml air inhaled at the resting expiration level. Spinal curvature morphology was evaluated using the Spinal Mouse in the sagittal plane when flexion was completed under the 2 increased functional residual capacity and resting expiration level conditions during finger-floor distance measurement. Finger-floor distance and spinal curvature were assessed according to functional residual capacity using one-way repeated measures analysis of variance and post-hoc analysis. [Results] Significant effects and differences were found for the finger-floor distance under all conditions. No significant effect was found for spinal curvature. [Conclusion] An increase in functional residual capacity may decrease trunk flexion. This correlation might also be observed in patients with chronic obstructive pulmonary disease.

Electroacupuncture Intervention Improved Pulmonary Function via Promoting Immunoregulation in Chronic Obstructive Pulmonary Disease Rats

To observe the immunoregulatory effect of electroacupuncture (EA) intervention for muscular dystrophy chronic obstructive pulmonary disease (COPD) rats, so as to investigate its underlying mechanism in improving respiratory function. Forty male SD rats were randomly divided into 5 groups: normal, model, EA, exercise, and EA+ exercise (n=8 in each). The muscular dystrophy COPD model was established by placing the rats in a closed box to be exposed to cigarette smoke (3-10 cigarettes/time) for 60 min, twice daily, 6 days a week for 90 days. The EA, exercise and EA+exercise interventions were given beginning from day 80 after exposure to cigarette smoke. EA (2 Hz/40 Hz, 6 mA) was applied to "Danzhong" (CV 17), "Qihai" (CV 6), "Zhongwan" (CV 12), "Liangmen" (ST 21) and bilateral "Quchi" (LI 11) for 10 min, once every other day, for 20 times. The swimming exercise was conducted by forcing the rat to swim in a water box for 10 min, once every other day, for 20 times. The rat's lung function including the resistance of inspiration (RI), functional residual capacity(FRC), pulmonary dynamic compliance (Cdyn), etc., was detected under anesthesia. Pathological changes of the lung tissue were detected by H.E. staining, and the contents of serum TNF-alpha, IL-6 and IL-1 beta assayed by ELISA. After 80 days' exposure to the cigarette smoke, the rats' body weight values in the model, EA, exercise and EA+exercise groups were significantly lower than that of the normal group(P<0.05). Moreover, the RI and FRC levels were significantly increased, and the Cdyn level was remarkably decreased in the model group relevant to the normal group (P<0.01). Following the intervention, both RI and FRC levels were significantly down-regulated in the EA, exercise and EA+exercise groups relevant to the model group (P<0.05), suggesting an improvement of the lung function. But the decreased Cdyn level had no marked improvement in the 3 treatment groups relevant to the model group (P>0.05). The numbers of monocytes and lymphocytes of the lung tissue, and the contents of serum TNF-α, IL-6 and IL-1 β were significantly higher in the model group than in the normal group (P< 0.01), and significantly lower in the EA, exercise and EA+exercise groups than in the model group (P<0.05), except monocytes in the exercise group (P>0.05). No significant differences were found among the EA, exercise and EA+exercise groups in the levels of RI and FRC, pulmonary monocytes and serum IL-6 and IL-1 β (P>0.05). The body weight was significantly higher in the exercise and EA+exercise groups than in the EA group, and the pulmonary lymphocytes and serum TNF-α obviously lowered in the EA group than in the exercise group (P<0.05). H.E. staining showed deformation of the bronchial tube cavity, detachment and flattening of the bronchial mucosal epithelial cilia, hyperplasia of Goblet cells, infiltration of abundant inflammatory cells in the submucosal layer and muscular layer, more secretions in the bronchovascular cavity, incomplete alveolar structure, thinning and rupture of the alveolar wall, and expansion of the alveolar cavity to form large pulmonary vesicles after modeling, which was obviously milder in the 3 treatment groups. EA intervention can improve the pulmonary function and pathological changes in pulmonary muscular dystrophy COPD rats, which is associated with its effects in reducing pulmonary monocytes and lymphocytes and serum TNF-α, IL-6 and IL-1 β contents, suggesting an enhancement of immunoregulation.

Effect of increased functional residual capacity on the active range of thoracic axial rotation in healthy young men.

[Purpose] To understand the effect of increased functional residual capacity (FRC) on the active range of thoracic axial rotation (AROTAR) in healthy young men. [Subjects and Methods] Thirty-nine right-handed healthy male volunteers (age=20.1 ± 1.6 years) participated in this study. A standard plastic goniometer was used to measure the AROTAR in the supine position with both glenohumeral joints fully flexed. AROTAR was recorded at the resting expiration level (REL) and for 4 different FRC levels: 500, 1,000, 1,500, and 2,000 ml air inhaled at REL. FRC volumes and laterality were analyzed using a two-way repeated measure of ANOVA and post-hoc analysis. Relationships between the relative value (AROTAR for each increased FRC level / REL AROTAR × 100) and AROTAR for each increased FRC level were analyzed using Pearson’s correlation coefficient. [Results] A significant main effect was found for only FRC factor. AROTAR had a positive moderate correlation with relative value. The correlation coefficient was higher than 0.5 for in 1,500 and 2,000 ml. [Conclusion] An increase in FRC might decrease AROTAR and if the REL AROTAR is high, the decrease in AROTAR due to increased FRC is lesser. It is suggested that maintaining the thoracic mobility could minimize a COPD patient’s AROTAR limitation and maintain physical ability.

Functional respiratory imaging to assess the interaction between systemic roflumilast and inhaled ICS/LABA/LAMA.

BackgroundPatients with COPD show a significant reduction of the lobar hyperinflation at the functional residual capacity level in the patients who improved >120 mL in forced expiratory volume in 1 second (FEV1) after 6 months of treatment with roflumilast in addition to inhaled corticosteroids (ICSs)/long-acting beta-2 agonists (LABAs)/long-acting muscarinic antagonists (LAMAs).MethodsFunctional respiratory imaging was used to quantify lobar hyperinflation, blood vessel density, ventilation, aerosol deposition, and bronchodilation. To investigate the exact mode of action of roflumilast, correlations between lobar and global measures have been tested using a mixed-model approach with nested random factors and Pearson correlation, respectively.ResultsThe reduction in lobar hyperinflation appears to be associated with a larger blood vessel density in the respective lobes (t=−2.154, P=0.040); lobes with a higher percentage of blood vessels reduce more in hyperinflation in the responder group. Subsequently, it can be observed that lobes that reduce in hyperinflation after treatment are better ventilated (t=−5.368, P<0.001). Functional respiratory imaging (FRI)-based aerosol deposition showed that enhanced ventilation leads to more peripheral particle deposition of ICS/LABA/LAMA in the better-ventilated areas (t=2.407, P=0.024). Finally, the study showed that areas receiving more particles have increased FRI-based bronchodilation (t=2.564, P=0.017), leading to an increase in FEV1 (R=0.348, P=0.029).ConclusionThe study demonstrated that orally administered roflumilast supports the reduction of regional hyperinflation in areas previously undertreated by inhalation medication. The local reduction in hyperinflation induces a redistribution of ventilation and aerosol deposition, leading to enhanced efficacy of the concomitant ICS/LABA/LAMA therapy. FRI appears to be a sensitive tool to describe the mode of action of novel compounds in chronic obstructive pulmonary disease. Future studies need to confirm the enhanced sensitivity and the potential of FRI parameters to act as surrogates for clinically relevant, but more difficult to measure, end points such as exacerbations.

Effect of high-dose N-acetylcysteine on airway geometry, inflammation, and oxidative stress in COPD patients

BackgroundPrevious studies have demonstrated the potential beneficial effect of N-acetylcysteine (NAC) in chronic obstructive pulmonary disease (COPD). However, the required dose and responder phenotype remain unclear. The current study investigated the effect of high-dose NAC on airway geometry, inflammation, and oxidative stress in COPD patients. Novel functional respiratory imaging methods combining multislice computed tomography images and computer-based flow simulations were used with high sensitivity for detecting changes induced by the therapy.MethodsTwelve patients with Global Initiative for Chronic Obstructive Lung Disease stage II COPD were randomized to receive NAC 1800 mg or placebo daily for 3 months and were then crossed over to the alternative treatment for a further 3 months.ResultsSignificant correlations were found between image-based resistance values and glutathione levels after treatment with NAC (P = 0.011) and glutathione peroxidase at baseline (P = 0.036). Image-based resistance values appeared to be a good predictor for glutathione peroxidase levels after NAC (P = 0.02), changes in glutathione peroxidase levels (P = 0.035), and reduction in lobar functional residual capacity levels (P = 0.00084). In the limited set of responders to NAC therapy, the changes in airway resistance were in the same order as changes induced by budesonide/formoterol.ConclusionA combination of glutathione, glutathione peroxidase, and imaging parameters could potentially be used to phenotype COPD patients who would benefit from addition of NAC to their current therapy. The findings of this small pilot study need to be confirmed in a larger pivotal trial.

Dynamic surface tension of natural surfactant extract under superimposed oscillations

Surfactant dysfunction plays a major role in respiratory distress syndrome (RDS). This research seeks to determine whether the use of natural surfactant, Curosurf™ (Cheisi Farmaceutici, Parma, Italy), accompanied with pressure oscillations at the level of the alveoli can reduce the surface tension in the lung, thereby making it easier for infants with RDS to maintain the required level of functional residual capacity (FRC) without collapse. To simulate the alveolar environment, dynamic surface tension measurements were performed on a modified pulsating bubble surfactometer (PBS) type device and showed that introducing superimposed oscillations about the tidal volume excursion between 10 and 70 Hz in a surfactant bubble lowers interfacial surface tension below values observed using tidal volume excursion alone. The specific mechanisms responsible for this improvement are yet to be established; however it is believed that one mechanism may be the rapid transient changes in the interfacial area increase the number of interfacial binding sites for surfactant molecules, increasing adsorption and diffusion to the interface, thereby decreasing interfacial surface tension. Existing mathematical models in the literature reproduce trends noticed in experiments in the range of breathing frequencies only. Thus, a modification is introduced to an existing model to both incorporate superimposed pressure oscillations and demonstrate that these may improve the dynamic surface tension in the alveoli.

Lung Aeration During Sleep

Background:During sleep, ventilation and functional residual capacity (FRC) decrease slightly. This study addresses regional lung aeration during wakefulness and sleep.Methods:Ten healthy subjects underwent spirometry awake and with polysomnography, including pulse oximetry, and also CT when awake and during sleep. Lung aeration in different lung regions was analyzed. Another three subjects were studied awake to develop a protocol for dynamic CT scanning during breathing.Results:Aeration in the dorsal, dependent lung region decreased from a mean of 1.14 ± 0.34 mL (± SD) of gas per gram of lung tissue during wakefulness to 1.04 ± 0.29 mL/g during non-rapid eye movement (NREM) sleep (− 9%) [p = 0.034]. In contrast, aeration increased in the most ventral, nondependent lung region, from 3.52 ± 0.77 to 3.73 ± 0.83 mL/g (+ 6%) [p = 0.007]. In one subject studied during rapid eye movement (REM) sleep, aeration decreased from 0.84 to 0.65 mL/g (− 23%). The fall in dorsal lung aeration during sleep correlated to awake FRC (R2= 0.60; p = 0.008). Airway closure, measured awake, occurred near and sometimes above the FRC level. Ventilation tended to be larger in dependent, dorsal lung regions, both awake and during sleep (upper region vs lower region, 3.8% vs 4.9% awake, p = 0.16, and 4.5% vs 5.5% asleep, p = 0.09, respectively).Conclusions:Aeration is reduced in dependent lung regions and increased in ventral regions during NREM and REM sleep. Ventilation was more uniformly distributed between upper and lower lung regions than has previously been reported in awake, upright subjects. Reduced respiratory muscle tone and airway closure are likely causative factors.

The inhibitory influence of pulmonary vagal afferents on respiratory distress induced by airway occlusion in halothane-anesthetized cats.

Although the sensation of dyspnea is common, the mechanisms underlying the sensation have not been fully elucidated. Dyspnea, which is a subjective sensation induced by various respiratory and nonrespiratory stimuli, ranges in intensity from an awareness of difficulty in breathing to an incapacitating state of respiratory distress. It need not be an all or none concept when tolerable; however, intolerable dyspnea is often accompanied by some kind of escape response. In a previous study, we developed a new concept of minimum alveolar anesthetic concentration for airway occlusion (MAC-AOR). Using this model, we assessed the influence of pulmonary vagal afferents on respiratory distress induced by airway occlusion. Adult cats (n = 13) of both sexes weighing 2.7-5.6 kg (3.9 +/- 0.3 kg, mean +/- SE) were anesthetized with halothane and tracheally intubated. After determination of MAC-AOR, anesthesia was maintained with the highest concentration of halothane permitting the positive motor response identified by visual inspection or electromyogram (EMG) of the forearm, usually of the head or extremities. Twisting or jerking of the head was considered a positive response, but twitching or grimacing was not. A slight movement of the shoulder and/or the extremities was not considered positive, nor were coughing, swallowing and chewing, or rigidity recognized as the increase of tonic activity on the forearm EMG. The duration from the start of airway occlusion to the onset of the positive response (DOCCL) was considered as behavioral measures of the tolerable limit of respiratory distress. DOCCL was measured before (Control 1), during, and after (Control 2) lung expansion induced by the injection of the inhaled gas of 5 mL/kg or 10 mL/kg (LE5 or LE10) at functional residual capacity level. Subsequently, 6 of 13 cats received bilateral vagotomies, and the same procedure was repeated at the same concentration as stated above. Then, MAC-AOR after vagotomy was determined again. Before vagotomy, the values of DOCCL during lung expansion (238 +/- 30 s during LE5 and 288 +/- 24 s during LE10) were significantly longer than Control 1 (169 +/- 29 s) and Control 2 (154 +/- 29 s) values (P < 0.01). After vagotomy, the effect of lung expansion on DOCCL was totally abolished. MAC-AOR after vagotomy (1.4% +/- 0.1%) was significantly higher than that before vagotomy (1.1% +/- 0.1%) (P < 0.01). We have demonstrated that vagotomy abolishes the prolongation effect of the lung expansion on DOCCL and increases the value of MAC-AOR in this animal model. These results suggest that pulmonary vagal afferents play an important role in relief of respiratory distress developed during airway occlusion. In anesthetized cats, we found that lung expansion reduces the tolerable limit to airway occlusion and vagotomy decreased minimum alveolar anesthetic concentration for airway occlusion, which suggests that pulmonary vagal afferents play an important role in relief of respiratory distress.

Acute Oxygen Supplementation Does Not Relieve the Impairment of Respiratory Muscle Strength in Hypoxemic COPD

To verify whether hypoxemia affects respiratory muscle strength in the absence of malnutrition and whether such effect, if present, is reversible with an acute oxygen supplementation. Case series analysis, before-after trial. Outpatient pneumology departments of two university hospitals. One hundred twenty patients affected by COPD in stable conditions having actual to ideal body weight ratio of > or =90%. Maximal inspiratory pressure (MIP) was measured at functional residual capacity level in the whole sample of subjects and during oxygen supplementation in 58 patients having a PaO2< or =60 mm Hg when breathing in room air. Predictors of MIP were assessed by a multivariate analysis. MIP values before and after oxygen supplementation were compared by a paired t test. MIP was independently correlated with FVC (p<0.001), PaO2 (p<0.01), and age (p<0.01). In the subgroup of hypoxemic patients, MIP values did not change significantly after oxygen supplementation (3.08+/-1.74 vs 3.03+/-1.91 kPa, t=0.43, not significant). Hypoxemia is an important negative correlate of MIP even in well-nourished COPD patients. Its effect is not reversible with an acute oxygen supplementation.

The Inhibitory Influence of Pulmonary Vagal Afferents on Respiratory Distress Induced by Airway Occlusion in Halothane-Anesthetized Cats

Although the sensation of dyspnea is common, the mechanisms underlying the sensation have not been fully elucidated.Dyspnea, which is a subjective sensation induced by various respiratory and nonrespiratory stimuli, ranges in intensity from an awareness of difficulty in breathing to an incapacitating state of respiratory distress. It need not be an all or none concept when tolerable; however, intolerable dyspnea is often accompanied by some kind of escape response. In a previous study, we developed a new concept of minimum alveolar anesthetic concentration for airway occlusion (MAC-AOR). Using this model, we assessed the influence of pulmonary vagal afferents on respiratory distress induced by airway occlusion. Adult cats (n = 13) of both sexes weighing 2.7-5.6 kg (3.9 +/- 0.3 kg, mean +/- SE) were anesthetized with halothane and tracheally intubated. After determination of MAC-AOR, anesthesia was maintained with the highest concentration of halothane permitting the positive motor response identified by visual inspection or electromyogram (EMG) of the forearm, usually of the head or extremities. Twisting or jerking of the head was considered a positive response, but twitching or grimacing was not. A slight movement of the shoulder and/or the extremities was not considered positive, nor were coughing, swallowing and chewing, or rigidity recognized as the increase of tonic activity on the forearm EMG. The duration from the start of airway occlusion to the onset of the positive response (DOCCL) was considered as behavioral measures of the tolerable limit of respiratory distress. DOCCL was measured before (Control 1), during, and after (Control 2) lung expansion induced by the injection of the inhaled gas of 5 mL/kg or 10 mL/kg (LE5 or LE10) at functional residual capacity level. Subsequently, 6 of 13 cats received bilateral vagotomies, and the same procedure was repeated at the same concentration as stated above. Then, MAC-AOR after vagotomy was determined again. Before vagotomy, the values of DOCCL during lung expansion (238 +/- 30 s during LE5 and 288 +/- 24 s during LE10) were significantly longer than Control 1 (169 +/- 29 s) and Control 2 (154 +/- 29 s) values (P < 0.01). After vagotomy, the effect of lung expansion on DOCCL was totally abolished. MAC-AOR after vagotomy (1.4% +/- 0.1%) was significantly higher than that before vagotomy (1.1% +/- 0.1%) (P < 0.01). We have demonstrated that vagotomy abolishes the prolongation effect of the lung expansion on DOCCL and increases the value of MAC-AOR in this animal model. These results suggest that pulmonary vagal afferents play an important role in relief of respiratory distress developed during airway occlusion. Implications: In anesthetized cats, we found that lung expansion reduces the tolerable limit to airway occlusion and vagotomy decreased minimum alveolar anesthetic concentration for airway occlusion, which suggests that pulmonary vagal afferents play an important role in relief of respiratory distress. (Anesth Analg 1998;86:398-402)

EMG study of respiratory muscles in humans immersed at different water temperatures

The electromyograms of the rectus abdominis (EMGra) and of the diaphragm (EMGdi) have been recorded on human subjects immersed at two bath temperatures (TW), 25 and 40 degrees C. The recordings were obtained during a calibrated isometric contraction sustained for 20 s against a closed stopcock at functional residual capacity (FRC) level for EMGra (expiratory effort) and at pulmonary volume greater than 90% vital capacity for EMGdi and EMGra (inspiratory effort). After eliminating the electrocardiographic artifact, the EMG signal was processed to obtain its root-mean-square (rms) value and three parameters of its frequency spectrum, total energy (Etot), centroid frequency (fc), and high-to-low ratio (H/L). The results show that EMGdi is not modified by TW. On the other hand rms and Etot of EMGra are always increased at TW = 25 degrees C compared with TW = 40 degrees C, whereas fc and H/L decrease with temperature during the expiratory effort at FRC level but do not vary during inspiratory effort at high pulmonary volume. These results, compared with those previously published for cooled limb muscles, show that TW can elicit EMG alterations on the superficial respiratory muscles through two mechanisms, an intrinsic mechanism due to the local variation in muscle temperature and an extrinsic mechanism acting upon the control system of the muscle contraction. Linked alterations of the muscular mechanical activity probably account for the observed effects of TW on the statics and the dynamics of the pulmonary volumes.

Diaphragmatic electromyography using a multiple electrode array.

We have developed a new technique for diaphragmatic electromyography using an array of seven sequential electrode pairs at 1.0-cm spacing on an esophageal catheter. This array provides information about the spatial distribution of the electrical field generated by the diaphragm and reveals a sharply peaked variation of electrical potential with distance along the esophagus. The rectified and integrated information from each of the seven pairs is summed to give an approximation to the total electrical activity over the span of the array, providing a signal that is relatively insensitive to the position of the array over approximately 4 cm of catheter movement and removes the requirement for balloon stabilization of the catheter. With our array, we have confirmed the artifact in the evoked compound muscle action potential that seems to be related to diaphragmatic shape as reported by others who used supramaximal phrenic nerve stimulation, but the magnitude of this artifact (compared with the functional residual capacity level) was modest near functional residual capacity, averaging 12 +/- 14% (SD) for lung volumes 1.0 l above and -4 +/- 15% for lung volumes 1.0 l below functional residual capacity along the rib cage-abdomen relaxation line.

Calibration of respiratory inductive plethysmograph during natural breathing.

We describe a single-posture method for deriving the proportionality constant (K) between rib cage (RC) and abdominal (AB) amplifiers of the respiratory inductive plethysmograph (RIP). Qualitative diagnostic calibration (QDC) is based on equations of the isovolume maneuver calibration (ISOCAL) and is carried out during a 5-min period of natural breathing without using mouthpiece or mask. In this situation, K approximates the ratio of standard deviations (SD) of the uncalibrated changes of AB-to-RC volume deflections. Validity of calibration was evaluated by 1) analyzing RIP waveforms during an isovolume maneuver and 2) comparing changes of tidal volume (VT) amplitude and functional residual capacity (FRC) level measured by spirometry (SP) with RIP values. Comparisons of VT(RIP) to VT(SP) were also obtained in a variety of postures during natural (uninstructed) preferential RC and AB breathing and with voluntary changes of VT amplitude and FRC level. VT(RIP)-to-VT(SP) comparisons were equal to or closer than published reports for single posture, ISOCAL, multiple- and linear-regression procedures. QDC of RIP in supine posture with comparisons to SP in that posture and others showed better accuracy in horizontal than upright postures.

Maximal expiratory flow at FRC, adjusted for absolute lung volume: specific Vmax FRC.

Maximal expiratory flow-volume curves were recorded in 85 healthy subjects, aged from 18 to 78 years. The maximal expiratory flow was measured at 75, 50 and 25% of the vital capacity (VmaxVC), at 60 and 40% of the total lung capacity (VmaxTLC), and at the functional residual capacity level (VmaxFRC). The latter was adjusted for the lung volume at which it was measured. The new parameter was named specific VmaxFRC (SVmaxFRC) and expressed in s-1. Normal values and prediction formulas based on height, weight, age and sex were established. It was found that: (1) adjustment for lung volume narrowed the interindividual variability of SVmaxFRC from 47 to 37%; (2) did not diminish the influence of age (p less than 0.001); (3) erased the influence of height and VC; (4) reduced the correlation with FEV1 (p less than 0.05), and (5) unveiled a borderline correlation with specific conductance (p less than 0.05).

Pulmonary function values and growth in Belgian white and blue double-muscled cattle

Seventy-five double-muscled cattle of the Belgian white and blue breed, two days to 50 months old and weighing 45 to 680 kg, were investigated. Transpulmonary pressure changes, measured with an oesophageal balloon, variations of air flow and volume at the mouth were obtained during spontaneous breathing to calculate pulmonary function data. Oxygen and carbon dioxide tensions in arterial blood were also recorded. Growth related changes of the pulmonary function values were similar to those observed in other bovine breeds. Total pulmonary resistance, specific total pulmonary resistance, viscous work, power of breathing, specific viscous work, respiratory frequency and peak-to-peak change in transpulmonary pressure were greater in Belgian white and blue cattle than in Friesian cattle. In the former, tidal volume, specific tidal volume, lowest transpulmonary pressure during expiration, transpulmonary pressure at the functional residual capacity level, dynamic lung compliance and oxygen tension in arterial blood were smaller. Airflow, minute volume and carbon dioxide tension in arterial blood were similar in the Belgian white and blue and Friesian cattle. These results were related to the great sensitivity of double-muscled cattle of the Belgian white and blue breed to laryngitis and bronchopneumonia.

Cardiopulmonary function of cats with respiratory distress induced by N-nitroso N-methylurethane.

The purposes of this study were to determine the effects of positive end-expiratory pressure (PEEP) and end-expiratory lung volume on systemic blood flow, whether PEEP levels yielding maximum systemic oxygen transport are associated with maximum lung compliance, and the effects of end-expiratory lung volume on pulmonary resistance to gas flow, in an animal model of respiratory distress. Twelve cats were inoculated with 12 mg/kg N-Nitroso N-Methylurethane (NNNMU) to induce respiratory distress. The NNNMU caused a 76% decrease in disaturated phosphatidyl-choline of lung lavage, a 34% decrease in functional residual capacity (FRC), an 80% decrease in lung compliance, an 88% increase in pulmonary resistance to gas flow, a 43% decrease in PaO2, and a 37% decrease in oxygen consumption. Systemic blood flow and systemic oxygen transport were not significantly altered by the chemically induced respiratory distress. PEEP levels of 5.1 +/- 0.8 cm H2O returned end-expiratory lung volume to normal FRC levels. Increases in PEEP caused systemic blood flow to decrease even when end-expiratory lung volume was below or equal to normal FRC levels but did not significantly affect systemic oxygen transport, lung compliance, or pulmonary resistance. We conclude that in cats with NNNMU-induced respiratory distress: PEEP causes decreases in systemic blood flow, lung compliance and systemic oxygen transport are not clear indicators of optimal PEEP level, and returning end-expiratory lung volume to normal FRC does not significantly reduce pulmonary resistance to gas flow.

Combined Heart and Lung Autotransplantation and Regulation of Breathing

The effects of en bloc autotransplantation of the heart and both lungs on the regulation of breathing were studied in four mongrel dogs. Tidal volume, respiratory rate, airflow, airway pressure and electromyograms from the intercostal muscles and diaphragm were recorded before and after the transplantation. The dogs breathed air or a mixture of 5% CO2 and air. Airway closure at functional residual capacity (FRC) level and after insufflation of 200 ml air was used as a mechanical stimulus. The following observations were made. 1) Stimulation by 5% CO2 after the transplantation increased the ventilatory minute volume by increasing the tidal volume while the respiratory rate remained unaltered. Before transplantation, both tidal volume and respiratory rate increased in response to CO2 stimulation. 2) After transplantation, stretching of the airways did not cause apnea (Hearing-Breuer reflex abolished) as it did preoperatively. 3) CO2 inhalation increased the efficiency of the respiratory muscles as expressed by the ratio of mechanical work (tidal volume or pressure impulse) to electrical activities of the respiratory muscles. This was most obvious in the dogs with transplant when the airways were closed at FRC level. Elimination of the afferent impulses due to en bloc transplantation of the heart and both lungs therefore modified the efferent impulses to the respiratory muscles. This effect was seen after both chemical and mechanical stimuli.

A Kr-81m Inhalation Method for Detection of Absence of Uniform Ventilation in Asthma

In an attempt to compare inhalation methods in detecting abnormal patterns of ventilation, the following four techniques were applied in 12 asthmatic patients: spontaneous respiration with a Kr-81m gas-air mixture (SP technique); serial inhalation of a Kr-81m gas-air mixture from the level of residual volume to total lung capacity (VC technique); bolus inhalation of 10 ml or Kr-81m gas from the level of residual volume, followed by air, to total lung capacity (RV technique); bolus inhalation of 10 ml of Kr-81m gas from the level of functional residual capacity, followed by air, to total lung capacity (FRC technique). Before exercise, abnormalities were detected by the RV and FRC techniques, but no abnormalities were detected by SP and VC techniques. On studies done after exercise, the abnormalities were detected by all the described techniques. However, they were best demonstrated by the RV technique and shown least well by the VC method.