Lung function changes and exercise-induced ventilatory responses to external resistive loads in normal subjects

Pulmonary function with expiratory resistive loading in healthy volunteers

Expiratory flow limitation is a key characteristic in obstructive pulmonary diseases. To study abnormal lung mechanics isolated from heterogeneities of obstructive disease, we measured pulmonary function in healthy adults with expiratory loading. Thirty-seven volunteers (25±5 yr) completed spirometry and body plethysmography under control and threshold expiratory loading of 7, 11 cmH2O, and a subset at 20 cmH2O (n = 11). We analyzed the shape of the flow-volume relationship with rectangular area ratio (RAR; Ma et al., Respir Med 2010). Airway resistance was increased (p<0.0001) with 7 and 11 cmH2O loading vs control (9.20±1.02 and 11.76±1.68 vs. 2.53± 0.80 cmH2O/L/s). RAR was reduced (p = 0.0319) in loading vs control (0.45±0.07 and 0.47±0.09L vs. 0.48±0.08). FEV1 was reduced (p<0.0001) in loading vs control (3.24±0.81 and 3.23±0.80 vs. 4.04±1.05 L). FVC was reduced (p<0.0001) in loading vs control (4.11±1.01 and 4.14±1.03 vs. 5.03±1.34 L). Peak expiratory flow (PEF) was reduced (p<0.0001) in loading vs control (6.03±1.67 and 6.02±1.84 vs. 8.50±2.81 L/s). FEV1/FVC (p<0.0068) was not clinically significant and FRC (p = 0.4) was not different in loading vs control. Supra-physiologic loading at 20 cmH2O did not result in further limitation. Expiratory loading reduced FEV1, FVC, PEF, but there were no clinically meaningful differences in FEV1/FVC, FRC, or RAR. Imposed expiratory loading likely leads to high airway pressures that resist dynamic airway compression. Thus, a concave expiratory flow-volume relationship was consistently absent-a key limitation for model comparison with pulmonary function in COPD. Threshold loading may be a useful strategy to increase work of breathing or induce dynamic hyperinflation.

Utility of Routine Spirometry Measures for Surveillance of Idiopathic Subglottic Stenosis

Importance

Because of the recurrent nature of idiopathic subglottic stenosis, routine follow-up is necessary for monitoring progression of stenosis. However, no easily accessible, standardized objective measure exists to monitor disease progression.

Objective

To determine whether peak expiratory flow (PEF) can be used as a reliable and easily accessible biometric indicator of disease progression relative to other validated spirometry measures in patients with idiopathic subglottic stenosis.

Design, Setting, and Participants

Prospectively collected data on PEF, expiratory disproportion index (EDI), and total peak flow (TPF) from 42 women with idiopathic subglottic stenosis without comorbid lower airway or parenchymal lung disease who were treated at a single tertiary referral center between 2014 and 2018 were analyzed. The mean follow-up period was 18.2 months (range, 2-40 months). Ten patients initially screened were not included in the analysis owing to comorbid glottic or supraglottic stenosis or nonidiopathic etiology.

Main Outcomes and Measures

Measurements of PEF, EDI, and TPF were taken at preoperative visits and at all other visits.

Results

Forty-two women (mean age, 51.5 years; 98% white [n = 41]) met the inclusion criteria. The area under the curve for PEF was 0.855 (95% CI, 0.784-0.926). The optimal cutoff value was 4.4 liters per second (264 L/min), with a sensitivity and specificity of 84.4% and 82.0%, respectively. The area under the curve for EDI was 0.853 (95% CI, 0.782-0.925). For TPF, this was 0.836 (95% CI, 0.757-0.916).

Conclusions and Relevance

This study provides evidence supporting the use of PEF as a simple, efficient, and accessible way of monitoring progression of idiopathic subglottic stenosis and predicting receipt of surgical intervention. Sensitivity and specificity of PEF were comparable to those of the more complex measures of TPF and EDI.

Novel Pulmonary Function Parameter Shifts in High-Grade Upper Airway Stenoses

Upper airway stenosis (UAS) is a common problem for anesthesiologists in laryngology as well as head and neck surgery, but it may lead to life-threatening situations if it is undetected. This retrospective case series was performed on patients who had UAS and presented with severe dyspnea or encountered difficulties in airway management. To assess the severity of UAS, the degree of stenosis was calculated using computed tomography scans and direct endoscopy. Lung function test was collected, and measured values were extracted as percentage of predicted reference values. Lower and higher grade stenoses were defined by Cotton-Myer classification and median degree of stenosis. Median of detected stenoses was 73% (64%-85%), with 7 of 10 patients classified as Cotton-Myer grade 3. Lung function tests showed typical parameter shifts as known from obstructive pulmonary diseases (OPDs). Furthermore, statistical analyses showed a significant higher value of residual volume (RV)/total lung capacity (TLC) in patients with higher grade stenosis (P < .05), whereas forced expiratory volume in 1 second /vital capacity (FEV1/VC) did not show a significant difference in same subgroups. In conclusion, the elevation of RV/TLC with concomitant normal FEV1/VC in symptomatic patients could be used to demarcate rare UAS from common OPD. Moreover, RV-TLC ratio might be used to distinguish between low- and high-grade UAS. But further epidemiological studies will be necessary to validate these findings. Level of evidence: 4.

Increased respiratory neural drive and work of breathing in exercise-induced laryngeal obstruction

Exercise-induced laryngeal obstruction (EILO), a phenomenon in which the larynx closes inappropriately during physical activity, is a prevalent cause of exertional dyspnea in young individuals. The physiological ventilatory impact of EILO and its relationship to dyspnea are poorly understood. The objective of this study was to evaluate exercise-related changes in laryngeal aperture on ventilation, pulmonary mechanics, and respiratory neural drive. We prospectively evaluated 12 subjects (6 with EILO and 6 healthy age- and gender-matched controls). Subjects underwent baseline spirometry and a symptom-limited incremental exercise test with simultaneous and synchronized recording of endoscopic video and gastric, esophageal, and transdiaphragmatic pressures, diaphragm electromyography, and respiratory airflow. The EILO and control groups had similar peak work rates and minute ventilation (V̇e) (work rate: 227 ± 35 vs. 237 ± 35 W; V̇e: 103 ± 20 vs. 98 ± 23 l/min; P > 0.05). At submaximal work rates (140-240 W), subjects with EILO demonstrated increased work of breathing ( P < 0.05) and respiratory neural drive ( P < 0.05), developing in close temporal association with onset of endoscopic evidence of laryngeal closure ( P < 0.05). Unexpectedly, a ventilatory increase ( P < 0.05), driven by augmented tidal volume ( P < 0.05), was seen in subjects with EILO before the onset of laryngeal closure; there were however no differences in dyspnea intensity between groups. Using simultaneous measurements of respiratory mechanics and diaphragm electromyography with endoscopic video, we demonstrate, for the first time, increased work of breathing and respiratory neural drive in association with the development of EILO. Future detailed investigations are now needed to understand the role of upper airway closure in causing exertional dyspnea and exercise limitation. NEW & NOTEWORTHY Exercise-induced laryngeal obstruction is a prevalent cause of exertional dyspnea in young individuals; yet, how laryngeal closure affects breathing is unknown. In this study we synchronized endoscopic video with respiratory physiological measurements, thus providing the first detailed commensurate assessment of respiratory mechanics and neural drive in relation to laryngeal closure. Laryngeal closure was associated with increased work of breathing and respiratory neural drive preceded by an augmented tidal volume and a rise in minute ventilation.

Using Pulmonary Function Data to Assess Outcomes in the Endoscopic Management of Subglottic Stenosis

Objective:

This study aimed to examine the authors’ experience with endoscopic management of idiopathic subglottic stenosis (iSGS), and to identify pulmonary function test (PFT) values that can be used to quantify outcomes.

Methods:

Retrospective review.

Results:

Twenty-five patients with a new diagnosis of iSGS were seen between 2006 and 2012. Median age at surgery was 45.3 years (interquartile range [IQR], 38.5-67.0), and median body mass index was 28.7 kg/m2 (IQR, 23.5-32.1). Forty-five procedures were performed. Median preoperative stenosis was 56.8% (Cotton-Myer grade 2). The typical stenosis began 15 mm below the true vocal folds and was 12 mm long. Median follow-up was 21.4 months (IQR, 5.1-43.1). For patients receiving multiple dilations, median time between procedures was 23.7 months. Four PFT parameters demonstrated significant improvement after intervention: (1) PEF (absolute change = 2.54 L/s), (2) PIF (absolute change = 1.57 L/s), (3) FEV1/PEF (absolute change = 0.44), and (4) FIF50% (absolute change = 1.71 L/s). PIF was the only parameter affected by using a larger balloon ( P = .047).

Conclusion:

PEF, PIF, FEV1/PEF, and FIF50% improved significantly after endoscopic incision and dilation of iSGS, and this could potentially be used as a metric by which to evaluate outcomes in the endoscopic management of subglottic stenosis.

Pulmonary functions in yogic and sedentary population

Background:

The Pulmonary Function Tests are important for measuring the fitness of an individual from a physiological point of view. Lung function parameters tend to have a relationship with lifestyle such as regular yoga, an ancient system of Indian Philosophy. Yoga is probably the best lifestyle ever devised in the history of mankind. Hence the present analytical study was undertaken to assess the effects of yoga on respiratory system when compared with sedentary subjects.

Objective:

To compare the pulmonary function test among the yogic and sedentary groups.

Materials and Methods:

The present study was conducted on 50 subjects practicing yoga and 50 sedentary subjects in the age group of 20-40 years. They were assessed for pulmonary function test in which sedentary group acted as controls. The tests which were recorded as per standard procedure using Medspiror as determinants of pulmonary function were FVC, FEV1, FEV3, PEFR and FVC/FEV1 ratio.

Results:

Pulmonary Functions were compared between the yoga practitioners and sedentary group. Yoga exercise significantly increased chest wall expansion as observed by higher values of pulmonary functions compared with sedentary controls. The study group were having higher mean of percentage value of FVC 109.1 ± 18.2%, FEV1 of 116.3 ± 15.9%, FEV3 of 105.7 ± 14.9 %, PEFR of 109.2 ± 21.3% and FEV1/FVC ratio of 111.3 ± 6.9% as compared to sedentary group.

Conclusions:

Regular Yoga practice increases the vital capacity, timed vital capacity, maximum voluntary ventilation, breath holding time and maximal inspiratory and expiratory pressures.

Cardio-respiratory fitness markers among Kenyan university students using a 20m shuttle run test (SRT)

AIM

To assess Cardio-respiratory fitness (CF) markers among university students using a 20m shuttle run test (SRT).

METHODS

Markers of CF were assessed in 80 males aged 21.4±1.8 years, randomly selected from Moi University, Kenya. Assessed at different stages of SRT protocol included heart rate (HR), systolic and diastolic blood pressure (SBP & DBP). VO2max was also determined. Data were analyzed using Stata v10. Comparisons were based on subjects exercise regimes.

RESULTS

Subjects with either regular or irregular regimes attained lower HR in 4(th) minute of SRT compared to non-exercise group (174.5±11.6 and 172.2±10.8 vs 182.8±6.8 b/m; p=0.04 and p=0.01 respectively). Lower HRs were maintained among irregularly exercising after 5(th) minute (176.5±10.1 vs 186.7±6.3 b/m; p=0.02). Regularly exercising subjects obtained lowest DBP at exhaustion compared to irregular and non-exercising (58.58±15.0, 62.43±12.9 and 64.1±8.8 mmhg respectively). VO2maxpredictors included year of study (r=-0.40), age (r=-0.41) and weight (r=-0.23). The regularly exercising had higher VO2max than irregular (p<0.01) and non-exercising (p<0.001). No demonstrable difference in VO2max existed between irregular and non-exercise subjects.

CONCLUSION

Exercise regimes should be emphasized amongst university students, albeit with less regard to regularity, which should be encouraged for those in higher study years and those with higher DBP at exhaustion.

Plastic cordotomy in the treatment of bilateral vocal fold immobility

BACKGROUND

The purpose of this study was to evaluate a new surgical method, plastic cordotomy for treatment of bilateral vocal fold immobility.

METHODS

We used cadaver experiments on 20 larynges to measure the widening of the glottis after bilateral plastic cordotomy. We conducted a prospective study of 21 female patients operated on with bilateral plastic cordotomy.

RESULTS

Bilateral plastic cordotomy enlarged the width of glottis to 9.55 (range, 8.3-10) mm in men and 8.5 (range, 7.4-8.8) mm in women and the area of glottis to 110.5 mm(2) (range, 88-149 mm(2) ) in men and to 84.5 mm(2) (range, 59-107 mm(2) ) in women. Clinical study revealed that the mean of peak inspiratory flow increased from 1.09 (0.41) L/seconds before surgery to 2.85 (0.67) L/seconds in long-term.

CONCLUSION

Plastic cordotomy is an effective, anatomically based method to alleviate obstruction in bilateral vocal fold immobility patients. The main advantage of plastic cordotomy is long-term stability of results due to prevention of restenosis.

Quantifying the Physiology of Laryngotracheal Stenosis: Changes in Pulmonary Dynamics in Response to Graded Extrathoracic Resistive Loading

OBJECTIVES/HYPOTHESIS

A model of airway obstruction was developed to study the impact of changes in airway resistance on ventilatory mechanics. This was used to derive quantitative indices of airway obstruction to aid in the objective diagnosis and physiological monitoring of adult patients with laryngotracheal stenosis (LTS).

METHODS

Six airway resistors, the characteristics of which mirrored the selective impediment to inspiratory airflow that occurs in patients with LTS, were created and calibrated. Maximum-effort flow-volume loops were obtained from 15 volunteers with resistors placed in series with the spirometer. Diagnostic and monitoring performances of various flow-volume indices were assessed with receiver-operating characteristics (ROC) and analysis of variance (ANOVA), respectively. Promising indices were further evaluated in patients with LTS.

RESULTS

Experimentally, the ratio of expiratory and inspiratory flows at midvital capacity (MEF50/MIF50) and peak expiratory to inspiratory flow ratio (PEF/PIF) had diagnostic sensitivities of 87% and 89%, respectively. The best index, both experimentally and clinically, was the ratio of area under the expiratory and inspiratory curves (ratio of integrals), with experimental and clinical sensitivities of 97% and 100%, respectively. A clinical specificity of 95%, and area under the curve of 0.965 were achieved for this index. Both PEF/PIF and the ratio of integrals could identify step changes in airway resistance greater than 10 cmH2O . sec . L (P < .05; ANOVA).

CONCLUSIONS

Flow-volume testing is simple and noninvasive and can be used to quantify the diagnosis and physiological monitoring of patients with LTS. The ratio of areas under the expiratory and inspiratory curves appears to be the optimal index for this purpose.

[Dyspnea of effort associated with a congenital aortic malformation]

INTRODUCTION

We report the case of a young woman presenting with dyspnoea of effort. Her records noted that correction of a double aortic arch had been performed in the neonatal period. At rest her flow/volume loop showed a moderate reduction of peak flow without an expiratory plateau. Exercise capacity was limited by sudden onset, during the last 2 stages of the test, of inspiratory dyspnea and tachypnea. During recovery there was no evidence of bronchospasm.

CASE REPORT

With this picture we suspected upper airway obstruction and bronchoscopy revealed tracheal compression to 50% of normal. CT scan with 3 dimensional reconstruction showed the trachea compressed between 2 aortic branches. In order to confirm that the tracheal compression increased during exercise we induced sympathetic stimulation by a "handgrip" test that reproduced the inspiratory dyspnea and lead to a reduction in inspiratory flows.

CONCLUSION

We have thus demonstrated that the increase in tracheal compression leading to limitation of airflow on exercise was due to an increase in aortic pressure and not to an increase in ventilatory flows.

Forced oscillation technique to evaluate tracheostenosis in patients with neurologic injury

STUDY OBJECTIVES

To determine the utility of forced oscillation technique (FOT) for measuring pulmonary resistance and reactance in patients with central nervous system injuries, for detection and follow-up of posttracheostomy tracheal stenosis.

DESIGN

Case series.

SETTING

A rehabilitation hospital, Brasilia, Distrito Federal, Brazil.

PATIENTS

Ten consecutive neurologically impaired patients, who had previously undergone tracheostomies, with tracheostenosis without current tracheostomy or other tracheal lesion.

INTERVENTIONS AND MEASUREMENTS

FOT evaluations were compared to tracheal diameter before and after bronchoscopic tracheostenosis dilatation procedures. Forced spirometry examinations were also obtained and compared.

RESULTS

Tracheal stenotic lesions were characterized by marked increase in resistance and reduction in reactance at low frequency and a marked increase in resonance frequency (Rf). Consistent reversal of this pattern with large reductions in total impedance of the respiratory system (Zresp) Rf and resistance at 5 Hz (R 5 Hz) were noted in all patients after each successful dilatation. Diameter of the stenosis was strongly correlated with Rf, Zresp, and R 5 Hz. The change in diameter before and after dilatation was similarly correlated with the changes in FOT values of Rf and Zresp. Spirometry values did not correlate well with the diameter of the tracheal stenosis.

CONCLUSION

The strong correlation of Rf, Zresp, and R 5 Hz to diameter of tracheostenosis suggests a previously unappreciated role for FOT in the noninvasive detection and follow-up of airway stenosis. This may be especially useful for patients with concomitant neurologic disabilities who are at risk of airway stenosis.

Measuring in situ central airway resistance in patients with laryngotracheal stenosis

OBJECTIVES

To evaluate a newly developed bronchoscopic technique for the assessment of intratracheal pressures.

STUDY DESIGN

In situ measurement of central airway resistance in 20 consecutive spontaneously breathing subjects. Thirteen patients had benign glottic or subglottic stenosis. Seven patients without central airway disease served as normal control subjects.

METHODS

A pressure catheter was introduced into the trachea via the working channel. The pressure swing was measured upstream and downstream of the stenosis. Central airflow was monitored simultaneously using a commercial pneumotachograph attached to a mouthpiece. Data acquisition frequency was 500 Hz. Prestenotic and poststenotic inspiratory and expiratory resistances could be calculated and displayed from the raw data off-line.

RESULTS

Inspiratory and expiratory resistances measured in mid-trachea or below the stenosis (subglottic) were 0.36 +/- 0.13 and 0.35 +/- 0.13 kPa.s/L for the control subjects (C), 1.11 +/- 0.47 and 0.65 +/- 0.26 kPa.s/L for patients who did not need to be operated on (NOOP), 7.11 +/- 7.19 and 3.35 +/- 2.25 kPa.s/L respectively for those who required surgical correction (OP). Supraglottic inspiratory and expiratory resistances for C were 0.22 +/- 0.09 and 0.25 +/- 0.06 kPa.s/L, for NOOP 0.15 +/- 0.10 and 0.14 +/- 0.11 kPa.s/L, and for OP 0.26 +/- 0.13 and 0.24 +/- 0.07 kPa.s/L respectively. The cut-off point for surgical correction was estimated to be > 2.5 kPa.s/L of inspiratory resistance. Concurrent expiratory values showed a considerable overlap between OP and NOOP. No correlation could be established between local resistance values and dyspnea score.

CONCLUSIONS

In situ subglottic flow-pressure tracing in spontaneously breathing patients who present with benign obstruction of the upper airways is well tolerated and may help to identify patients who need surgical correction.

Emergency stenting of malignant obstruction of the upper airways: long-term follow-up with two types of silicone prostheses

We report on 10 patients with severe malignant "mixed-type" obstruction of the proximal trachea or distal trachea plus both main stem bronchi. They had far-advanced inoperable tumors (esophageal cancer in 4 patients, lung cancer in 3, and recurrent laryngeal, uvular, and thyroid cancers in 1 each). Emergency treatment consisted of a dilating bougie maneuver followed by the insertion of a large one-way (4 patients) or Y-shaped (6) silicone prosthesis. Subsequent to the intervention, there was long-lasting clinical improvement. The median survival from stent insertion was 8 months for all patients irrespective of tumor type; it was 5 months for lung carcinoma patients and 8 months for those with esophageal cancer. The results are in accordance with those of other studies using different therapeutic modalities. Stent exchange proved necessary in 5 patients. The main reasons were continuing tumor growth beyond the proximal and distal boundaries and recurrent productive bronchial infection. Patients died of pneumonia (4 patients), pulmonary lymphangitic spread (1), heart failure (2, one of whom also had pneumonia), and fatal hemorrhage (1). As of December 1995, 3 patients were still alive, 2, 5, and 8 months after stent implantation. As evidenced by clinical efficacy and length of palliation, endoscopic placement of silicone-based one-way and bifurcated prostheses in far-advanced tumor of the central airways is technically feasible and ethically justifiable.

Emergency stenting of malignant obstruction of the upper airways: long-term follow-up with two types of silicone prostheses

OBJECTIVE

We evaluated the long-term prognosis of stents placed on an emergency basis in the trachea and its bifurcation for malignant stenosis.

METHODS

We retrospectively analyzed all bronchologic treatments of obstructing airway lesions from January 1993 to December 1995.

RESULTS

We report on 10 patients with severe malignant "mixed-type" obstruction of the proximal trachea or distal trachea plus both main-stem bronchi. They had far-advanced inoperable tumor (esophageal cancer: n = 4; lung cancer: n = 3; recurrent laryngeal, uvula, and thyroid cancer: n = 1 each). Emergency treatment consisted of a dilating bougie maneuver followed by the insertion of a large one-way (n = 4) or Y-shaped silicone prosthesis (n = 6). After the intervention, there was a long-lasting clinical improvement. Median survival from stent insertion was 8 months for all patients irrespective of tumor type; it was 5 months for patients with lung carcinoma and 8 months for those with esophageal cancer. The results are in accordance with other studies using different therapeutic modalities. Stent exchange was necessary in five patients. Main reasons were continuing tumor growth beyond the proximal and distal boundaries and recurrent productive bronchial infection. Patients died of pneumonia (n = 4), pulmonary lymphatic spread (n = 1), cardiac failure (n = 2), and fatal hemorrhage (n = 1). As of December 1995, three patients were still alive 2, 5, and 8 months after implantation.

CONCLUSIONS

As evidenced by clinical efficiency and length of palliation, endoscopic placement of silicone-based one-way and bifurcational prostheses in far-advanced tumor of the central airways is technically feasible and ethically justifiable.