Alterations In Lung Volume Research Articles

Lung Volume Changes in Stable Preterm Infants Weaned From Nasal CPAP to High Flow: A Prospective Cohort Study

BackgroundWeaning preterm infants off nasal continuous positive airway pressure (nCPAP) using nasal high-flow therapy has gained popularity. The effects of such a weaning strategy on lung volumes are unclear. Research QuestionHow does the transition from nCPAP to high-flow as well as varying flow levels affect lung volumes in stable preterm infants? Study Design and MethodsThis was a prospective cohort study in infants 30-35 weeks postmenstrual age. After a baseline period on nCPAP 5 cm H2O, infants were switched to high-flow 8 L/min for 30 minutes. The flow level was reduced by 2 L/min every 30 minutes to a minimum of 2 L/min and subsequently increased to the initial level of 8 L/min, followed by another nCPAP period. Using electrical impedance tomography (EIT), end-expiratory lung impedance (EELZ) as a proxy for end-expiratory lung volume (EELV) and cardiorespiratory parameters were recorded at each flow level and compared to baseline. ResultsOverall, 8438 breaths from 19 infants were analyzed. EELV changed significantly during the study (P = 0.002), which was mainly attributable to a loss of EELV when high-flow was reduced to 6 and 4 L/min and re-escalated to 4, 6, and 8 L/min. Apart from a reduction in minute ventilation (P = 0.004), no other significant changes were found in EIT ventilation parameters. Alterations in lung volume were accompanied by an increase in heart rate (P = 0.02) and a decrease in SpO2/FiO2 ratio (P < 0.001). InterpretationThe transition from nCPAP to high-flow is likely to result in a reduced EELV, accompanied by physiological responses in heart rate and oxygenation. Despite a stepwise escalation to pre-weaning flow levels, only partial recovery of lung volume losses is achievable with high-flow. Clinical Trial RegistrationClinicalTrials.gov (NCT05237622)

Preservation vs. dissection of inferior pulmonary ligament for thoracoscopic upper lobectomy: a prospective randomized controlled trial

ObjectivesThe proper procedure for inferior pulmonary ligament (IPL) during upper lobectomy remains a topic of debate. To address this matter, we carried out a trial comparing the clinical outcomes of IPL preservation versus IPL dissection during thoracoscopic upper lobectomy (TUL).MethodsPatients undergoing thoracoscopic left/right upper lobectomy (TLUL/TRUL) were assigned to either the dissection group (Group D) or the preservation group (Group P). Our primary objective was to quantify and compare the alterations in postoperative residual bronchial angle and lung volume changes between the two groups. Our secondary objective encompassed the assessment of various other intraoperative and postoperative outcomes.ResultsFollowing adherence to the inclusion and exclusion criteria, we enrolled 100 patients (41 left and 59 right) in Group P and 108 patients (41 left and 67 right) in Group D for the study. Our findings revealed that in TLUL, Group P was able to reduce the degree of postoperative residual bronchial angle change (P < 0.05). Conversely, the situation was distinct for TRUL. We found no notable disparity between the two groups (P > 0.05) with regard to alterations in lung volume or the occurrence of postoperative complications—except for the duration of postoperative hospital stay (P < 0.05).ConclusionsOur study suggests IPL preservation especially for TLUL when compared to TRUL, which have important implications for the clinical management of patients undergoing upper lobectomy.

Functional assessment of allergic asthmatic children while asymptomatic

The aim of this study was to detect the best test lung function to identify abnormalities in asthmatic children while asymptomatic. We studied 200 asthmatic children. Patients were evaluated by questionnaire to evaluate the presence of symptoms and drug consumption in the previous 3 months. Allergological evaluation by skin-prick tests and seric-specific IgE determination for relevant local inhalant allergens was made. Lung function was studied evaluating expiratory flows and measuring lung volumes by nitrogen washout technique. One hundred twenty-seven of 200 (63%) children showed functional abnormalities: 21 (10.5%) children had flow reductions, 56 (28%) children had volume modifications, and 50 (25%) children had either flow and lung volume alterations, respectively. We observed increased total lung capacity (TLC), residual volume (RV), and ratio RV/TLC values more often in patients with mild and moderate persistent asthma than in patients with intermittent asthma. No significant difference was detected considering expiratory flows. Measurements of lung volumes are an important tool to evaluate "air trapping" in asthmatic patients and this could be related to disease severity. According to the literature, our data suggest that an increase of RV, functional residual capacity RV/TLC could be the only functional airway dysfunction present in asthmatic children during asymptomatic period.

Effect of smoking cessation on pulmonary and cardiovascular function and structure: analysis of guinea pig model

To assess the pulmonary structural and functional effects of smoking cessation, we exposed groups of guinea pigs to cigarette smoke for 4 and 8 mo and included a group of animals in which smoke exposure was stopped at 4 mo (ex-smokers). We found that, compared with control nonsmokers, the smokers at both 4 and 8 mo showed airflow obstruction with alterations in lung volume and morphological evidence of emphysema with increased alveolar air space size and decreased alveolar surface area-to-volume ratio. There was an alteration in the pulmonary vascular structure, with increased numbers of muscularized arterioles, in the smokers at both time periods, and this was associated with significantly increased pulmonary arterial pressure at 8 mo. Cessation of smoke exposure appeared to halt, but not reverse, these structural changes. The smokers at 8 mo showed clear evidence for a "healthy smoker" effect, underscoring the necessity for longitudinal studies even when using an animal model. We conclude that cessation of exposure to cigarette smoke is associated with an apparent halt, but not a reversal, of emphysematous lung enlargement and pulmonary arteriolar muscularization. However, the magnitude of improvement in pulmonary function is not as great as the apparent structural differences would imply, and there is no clear effect on the pulmonary arterial pressure.

Diaphragmatic Electromyogram Power-Spectral Analysis as a Function of Reduced End-Expiratory Lung Volume

We examined the centroid frequency (Fc) of the electromyogram power-frequency spectra from the costal (EMGco) and crural (EMGcr) diaphragms at functional residual capacity and at reduced end-expiratory lung volume (EELV) (induced by abdominal banding) in six anesthetized newborn piglets. EMGco and EMGcr were recorded from bipolar electrodes embedded in the costal and crural diaphragms respectively. A fast Fourier transformation of ECG free EMGco and EMGcr was used to compute the power-frequency spectra and calculate the Fc of EMGco and EMGcr. The nitrogen washout technique was used to measure EELV. Abdominal banding induced a reduction in EELV of 30.6% functional residual capacity (range 22-39%). The mean Fc of EMGcr was not significantly altered by the reduction in EELV, whereas the mean Fc of the EMGco fell in every animal at reduced EELV by 13 +/- 8% of baseline Fc (p less than 0.05). We conclude that alterations in lung volume alone can determine changes in the EMGco power spectrum and Fc. Investigators performing EMGco power spectral analysis should consider EELV status when interpreting their findings.

Changes in aerosol-derived airspace diameter induced by bronchoconstrictors and alterations in lung volume

Inhaled aerosols have been used to estimate the size of pulmonary airspaces, yet little is known regarding the sensitivity of this technique to detect changes. To evaluate this, we measured aerosol-derived airspace diameter (ADAD) in the lungs of four dogs at different volumes as well as before and after bronchoconstriction induced by intravenous methacholine (MCH) or prostaglandin F 2 α(PGF)

Time course of lung volume changes during prolonged treadmill exercise.

It has been known since the 1920s that runners completing marathon races have reduced forced vital capacity (FVC) values. To investigate the time course of these lung volume alterations, we measured FVC and residual volume (RV) in 11 runners before, after, and at 30-min intervals during a 2.5-h treadmill run at just under their marathon pace (70% VO2max). Mean distance run was 21.5 +/- 1.5 (SD) miles in the 2.5-h period. During the first 60 min, both RV and total lung capacity (TLC) decreased by 110 ml, however, this change was not significant (P greater than 0.05). A high correlation (r = 0.93) was observed between delta RV and delta TLC during the first 5 min, while FVC remained unchanged. From 60-90 min, all lung volumes remained constant. From 90-150 min, lung volumes changed in a direction similar to that observed after a marathon, i.e., FVC decreased significantly (5.51 to 5.37 liter between 90 and 150 min, P less than 0.05), TLC remained unchanged (7.41 vs 7.42 liter, P greater than 0.05), and RV showed a nonsignificant increase from 1.90 to 2.05 liter (P greater than 0.05). The data are consistent with multiple mechanisms playing a role in pulmonary function changes during prolonged exercise. The smaller mean decrease in FVC observed in this study, as compared to that found during a marathon, suggested that the marathon imposes a greater demand on the lungs than did treadmill exercise of the duration and relative intensity used in this study.

Positional Hypoxemia in Unilateral Lung Disease

BODY position may affect gas exchange by altering the matching of ventilation to perfusion within the lungs.1 2 3 In normal subjects breathing normally, both blood flow and ventilation are greater in the dependent lung zones. When subjects breathe deeply so that lung volume falls below that present at the end of normal expiration, the nondependent lung zones are preferentially ventilated.4 These considerations may assume clinical importance in unilateral lung disease, in which alterations in lung volume and regional perfusion complicate the predictability of the gravitational effects on gas exchange.5 We have encountered positionally related cardiac arrhythmias and dyspnea induced by lying . . .

Positional hypoxemia in unilateral lung disease.

BODY position may affect gas exchange by altering the matching of ventilation to perfusion within the lungs.1 2 3 In normal subjects breathing normally, both blood flow and ventilation are greater in the dependent lung zones. When subjects breathe deeply so that lung volume falls below that present at the end of normal expiration, the nondependent lung zones are preferentially ventilated.4 These considerations may assume clinical importance in unilateral lung disease, in which alterations in lung volume and regional perfusion complicate the predictability of the gravitational effects on gas exchange.5 We have encountered positionally related cardiac arrhythmias and dyspnea induced by lying . . .

Alterations in lung volume and pulmonary function in relation to hemodynamic changes in acute myocardial infarction.

To characterize the changes in lung volumes after acute myocardial infarction (AMI), and the relationship of these changes to other alterations in lung function which correlate with the severity of pulmonary vascular congestion, we made measurements of pulmonary hemodynamics, lung volume, closing volume, frequency dependence of total pulmonary resistance to forced oscillation, and arterial PO2 in 18 subjects with AMI. The most consistent finding was reduced lung volume which correlated with the severity of pulmonary diastolic hypertension. Frequency dependence of resistance showed a small but significant correlation with pulmonary hemodynamics. Closing volume measurements by the resident gas method in nine subjects was not related to hemodynamics. Follow-up studies at the time of hospital discharge revealed a significant return toward normal for arterial PO2, all lung volumes, and total pulmonary resistance at 9 Hz. Based on measurements in healthy subjects, the reduced lung volume after AMI may explain the changes in resistance. In acute and follow-up studies the degree of lung volume reduction and the severity of hypoxemia were strongly correlated.

ALTERATIONS IN NEONATAL RESPIRATORY FUNCTION FOLLOWING CHEST PHYSIOTHERAPY

Percussion, suctioning and hyperventilation have been recommended for airway management in neonates requiring endotracheal tubes. To investigate physiological alterations in respiratory function due to chest physiotherapy, we measured arterial blood gases, respiratory patterns, lung mechanics, and functional residual capacity (FRC) in 10 neonates, weights (1.25 to 3.20 kg) during the control period, post vibration of the chest and suctioning, after hyperventilation, and 2 hours post suctioning. Post suctioning compared to controls mean (± SEM) PaO2 decreased 75.2 (± 9.3) to 44.0 (±3.1) mm Hg (P<0.01) while lung compliance and FRC were unchanged. There was a decrease in inspiratory resistance (RI) from 81.8 (± 14.6) to 59.0 (± 10.6) cm H2O/L/sec. (P<0.02) and I:E ratio increased from 0.93 (± 0.04) to 1.04 (± 0.06) (P<0.07). Hyperventilation compared to post suctioning resulted in an increase in mean (± SEM) PaO2 to 63.9 (± 10.0) mmHg (P<0.01), and RI to 98.3 (± 22.0) cm H2O/L/sec. (P<0.05). FRC, CL, VT were unchanged. Two hour followup values for all parameters studied were similar to control values except for a trend toward increased compliance. There were no significant differences at any stage of the study for PaCO2, pH, base excess, VT, or minute ventilation. This study indicates that there is a significant decrease in PaO2 after chest vibration and suctioning increase in PaO2 after hyperventilation but these changes do not appear to be related to alterations in lung volume.

Airway closure and lung volumes in surgical positions.

The closure of small airways in gravity-dependent lung regions (airway closure) is thought to be an important factor influencing ventilation-perfusion (v/q) relationships. Airway closure has been noted by other authors as predisposing to atelectasis, under appropriate circumstances. We have assessed airway closure by a modified single breath nitrogen technique in ten normal male subjects in several surgical positions. Functional residual capacity (frc) was measured by a closed-circuit helium technique, to allow correlation of the airway closure findings with the alterations in lung volume associated with the posture changes. Functional consequences of airway closure are likely when the closing volume (the lung volume at which airway closure starts to occur) is abovefrc, with closure then occurring within the range of tidal breathing. Subjects were studied in the seated, supine, 15° head-down, and combined lithotomy plus 15° head-down position. Airway closure was found to involve increasing lung volumes with increasing subjects’ ages, in agreement with previous observations. In the seated position the age at which the closing volume exceededfrc was 49 years. This age decreased to 36 in the supine position, 35.5 head-down, and 32 in the combined lithotomy and head-down position. Body position, therefore, has an important effect on the critical relationship between the closing volume andfrc, and hence on the functional consequences of airway closure. *** DIRECT SUPPORT *** A00LO001 00003

The reflex effects of alterations in lung volume on systemic vascular resistance in the dog.

1. The reflex effects of alterations in lung volume on systemic vascular resistance have been studied in anaesthetized dogs under conditions in which the systemic circulation was perfused at constant blood flow. The pressures in the isolated perfused carotid sinuses and aortic arch, and the arterial blood P(O2) and P(CO2) were maintained constant.2. A maintained inflation of the lungs produced by injection of air into the trachea caused a fall in systemic arterial perfusion pressure, indicating vasodilatation. The size of the systemic vasodilator response varied directly with the pressure and volume of gas used to inflate the lungs. A similar effect was observed when the tidal volume of lungs ventilated by an intermittent positive pressure was increased.3. Collapse of the lungs by creating a pneumothorax in closed-chest spontaneously breathing animals evoked a systemic vasoconstrictor response which was reversed when the lungs were re-expanded.4. These vasodilator responses were abolished by dividing the pulmonary branches of the thoracic vagosympathetic nerves. Evidence is presented that the afferent fibres run in the cervical vagosympathetic nerves and through the stellate ganglia.5. The responses were unaffected by atropine, but were abolished by hexamethonium, guanethidine and by bretylium tosylate, indicating that they are mediated via the sympathetic nervous system.6. Evidence is presented that the lungs are a constant course of afferent impulses inhibiting the ;vasomotor centre', and that the lung inflation-systemic vasodilator reflex is a potential mechanism operating in eupnoeic breathing.