Inspiratory Flow Ratio Research Articles

Accuracy of Real-Time Data Provided by Mechanical Insufflation-Exsufflation Devices.

Mechanical insufflation-exsufflation (MI-E) is crucial to assist patients with impaired cough, especially those with neuromuscular diseases. Despite recent advancements that enable real-time display of peak expiratory flow (PEF) and inspiratory volume, accurately monitoring these parameters with MI-E devices during treatment can still present challenges. A bench study that used a mechanical lung connected to 3 MI-E devices (EOVE-70; E-70 and Comfort Cough II) was conducted to evaluate PEF and inspiratory volume monitoring accuracy. Two clinical conditions were tested, low and normal compliance, with 6 different MI-E settings tested: +20/-20, +30/-30, +40/-40, +40/-50, +40/-60, and +40/-70 cm H2O. PEF (L/min) and inspiratory volume (mL) displayed on the screen were recorded cycle by cycle, while a pneumotachograph connected to the mechanical lung was used to measure the actual PEF and inspiratory volume for data comparison. Flow bias was assessed by calculating the difference (PEF - peak inspiratory flow) and ratio (PEF to peak inspiratory flow) between flows. All devices systematically underestimated PEF, with device A showing the smallest estimation error (-7.4 [-10.1; -6] %). Devices B and C exhibited larger errors (-26.5 [-29.2; -25.6] and (-29.9 [-30.7; -28.7] %, respectively). All the devices underestimated inspiratory volume, with device B showing the smallest estimation error (-15.1 [-21.2; -12.3] %). Device A exhibited a significantly larger error (-26.9 [-30.3; -24.8] %). The error from device C (-17.7 [-34.5; -13.8] %) was not statistically different from device B. Device type, high pressure settings (> +40/-40 cm H2O), and a lung model compliance of 60 mL/cm H2O were the main contributors to error in estimating PEF and inspiratory volume. Finally, we observed differences of PEF-to-peak inspiratory flow ratio and PEF minus peak inspiratory flow differences achieved. Our study highlighted consistent underestimation of PEF and inspiratory volume across MI-E devices. Improving device monitoring is essential for guiding MI-E therapy and ensuring patient safety.

Changes in Breathing Patterns after Surgery in Severe Laryngomalacia.

Background: Most of the studies regarding the surgical treatment of severe laryngomalacia (LM) have been aimed at describing the efficacy of the treatment in terms of improvement of clinical symptoms or anatomical findings. There are no studies specifically aimed at analyzing the changes in breathing patterns following surgical treatment for severe LM. Objective: To review the breathing pattern changes before and after corrective surgery in infants with severe LM. Study design: A series of retrospective cases at a tertiary referral children’s hospital. Methods: Retrospective chart review of 81 infants who underwent supra-glottoplasty (SGP) for severe laryngomalacia between 2011 and 2020 at Bambino Gesù Children’s Hospital of Rome, Italy. Among the patients, 47 (58%) were male and 34 (42%) were female. Twenty-one patients (26%) had one or more comorbidities condition. The data collected included age, symptoms, a polysomnography/pulse oximetry study, growth rate, the findings from flexible endoscopy, pre- and post-supra-glottoplasty (SGP) pulmonary function tests (PFTs) and, when indicated, 24 h pH-metry. Breathing patterns were studied during restful, normal sleep, using an ultrasonic flow-meter (Exhalyzer, Viasys) which measured: Tidal Volume (Vt), Respiratory Rate (RR), time to peak expiratory flow/expiratory time ratio (tPTEF/Te, an index of the patency of the lower airways) and mean expiratory/mean inspiratory flow ratio (MEF/MIF, an index of the patency of the upper airways) evaluated before surgical procedure (T1) and 3–6 weeks after (T2). Pre- and post-operative mean data were calculated and comparisons made with a Student T-test. Results: The surgical procedure was well tolerated by all infants and no intraoperative or post-operatory long-term complications were noted. In T1, breathing patterns were characterized by low tidal volume and high tPTEF/Te and MEF/MIF ratios, suggesting a severe reduction in the patency of the upper airways in all patients. After surgery (T2), all the previously mentioned variables significantly improved, reaching normal values for the child’s age. Conclusions: Supra-glottoplasty, as already described in several studies, is a safe and efficient procedure to treat severe laryngomalacia during infancy. The improvement in breathing patterns after surgery was reliably confirmed by a lung function test in our study, which showed the diagnostic value of testing respiratory functionality in the laryngomalacia and comparing them to clinical and endoscopic data. Moreover, considering the results obtained, we also propose the use of this available, dependable test to verify its therapeutic effects (post-surgery) and to monitor future respiratory development in these infants. Moreover, we believe that further studies will provide detailed grading guidelines for gravity of the LM, based on these functional lung tests.

Feasibility of structured light plethysmography for the evaluation of lung function in preschool children with asthma.

Structured light plethysmography (SLP) is a new noninvasive technology to capture the movement of the thoracic and abdominal wall, and to assess some parameters indicative for lung function. The purpose of the study was to evaluate the feasibility of SLP in children with asthma. A total of 52 patients were enrolled: 25 with asthma exacerbation (group 1), 13 with well-controlled asthma (group 2), and 14 healthy controls (group 3). Every patient underwent SLP evaluation and a lung function test. SLP evaluations showed that the ratio of inspiratory flow at 50% of tidal volume (Vt) to expiratory flow at 50% of Vt, in which Vt is taken to be the exhaled chest wall movement, and flow is taken to be the time derivative of the chest wall movement (IE50) value increased in group 1 compared with groups 2 and 3, with statistical significance (p = 0.018); the data were consistent with the spirometry parameter. A correlation between the IE50 and forced expiratory volume in the first second of expiration was highlighted (r = -0.35, p = 0.019). SLP assessed airway obstruction, and its use in clinical practice could be applied in preschool children in future studies.

Changing Breathing Pattern in Laryngomalacia after Surgery

Objective: Most of the studies on the surgical treatment of severe laryngomalacia have aimed to describe the efficacy of the treatment in terms of improvement of clinical symptoms or anatomical findings. The aim of this study is to analyze the changes in breathing patterns following aryepiglottoplasty for severe laryngomalacia. Method: A series of retrospective cases at a tertiary referral children’s hospital. Between 2005 and 2010, 40 infants with severe laryngomalacia were studied before (T1) and after surgery (T2). Breathing patterns were studied using an ultrasonic flow-meter measuring: tidal volume, respiratory rate, time to peak and mean expiratory flow/expiratory time ratio. Results: The surgical procedure was well tolerated in all the infants and no perioperative and long-term complications were present. In T1, the breathing pattern is characterized by low tidal volume and high flow/expiratory time ratio (tPTEF/Te) and mean expiratory/mean inspiratory flow ratio (MEF/MIF), suggesting a severe reduction in upper airways patency for all patients. After surgery (T2), all above mentioned variables significantly improved, reaching normal values for the age. Conclusion: Pulmonary function test in this study showed the diagnostic value of testing respiratory functionality in severe laryngomalacia and comparing them to clinical and endoscopic data. Moreover, we also propose the use of this available test to verify the therapeutic effects and to monitor future respiratory development in these infants.

Intrapulmonary Effects of Setting Parameters in Portable Intrapulmonary Percussive Ventilation Devices

Despite potential benefits of intrapulmonary percussive ventilation (IPV) in various respiratory diseases, the impact of setting parameters on the mechanical effects produced by IPV in the lungs is unknown. We hypothesized that changing the parameters on IPV would modulate these effects. This in vitro study aimed at comparing the changes in intrapulmonary effects resulting from changes in parameters in 3 portable IPV devices (IMP2, Impulsator, and Pegaso). Parameters were set in 72 combinations of frequency (90-250 cycles/min), inspiratory to expiratory (I/E) time ratio (from 1/2 to 3/1), and pressure (10-60 cm H(2)O). Four resulting effects were recorded on a test lung via a pneumotachometer: the expiratory to inspiratory flow ratio (E/I flow ratio), the PEEP, the ventilation, and the percussion. Percussion was assessed by the end-slope of the pressure curve. Analysis of variance was used for data analysis. E/I flow ratio increased with increasing I/E time ratio (P < .001). The Pegaso produced the lowest E/I flow ratio. PEEP raised 6 cm H(2)O in both IMP2 and Impulsator, and 17 cm H(2)O in the Pegaso with increasing frequency (P < .01), pressure, and I/E time ratio (P < .001). In all devices, ventilation increased with increasing pressure and decreasing frequency (P < .001). Percussion increased with increasing frequency and decreasing I/E time ratio (P < .001), and with increasing pressure when I/E time ratio was 1/1 or less. The Pegaso provided the poorest percussion. This study suggests that changing the parameters considerably modulates the mechanical effects produced by portable IPV devices in the lungs. Increasing frequency increased PEEP and percussion, but decreased ventilation. Increasing I/E time increased PEEP and E/I flow ratio, and decreased percussion. Finally, increasing pressure increased PEEP and ventilation. The Pegaso produced the highest PEEP, least percussion, and smallest change in E/I flow ratio.

The unique contribution of manual chest compression–vibrations to airflow during physiotherapy in sedated, fully ventilated children*

This study aimed to quantify the specific effects of manual lung inflations with chest compression-vibrations, commonly used to assist airway clearance in ventilated patients. The hypothesis was that force applied during the compressions made a significant additional contribution to increases in peak expiratory flow and expiratory to inspiratory flow ratio over and above that resulting from accompanying increases in inflation volume. Prospective observational study. Cardiac and general pediatric intensive care. Sedated, fully ventilated children. Customized force-sensing mats and a commercial respiratory monitor recorded force and respiration during physiotherapy. Percentage changes in peak expiratory flow, peak expiratory to inspiratory flow ratios, inflation volume, and peak inflation pressure between baseline and manual inflations with and without compression-vibrations were calculated. Analysis of covariance determined the relative contribution of changes in pressure, volume, and force to influence changes in peak expiratory flow and peak expiratory to inspiratory flow ratio. Data from 105 children were analyzed (median age, 1.3 yrs; range, 1 wk to 15.9 yrs). Force during compressions ranged from 15 to 179 N (median, 46 N). Peak expiratory flow increased on average by 76% during compressions compared with baseline ventilation. Increases in peak expiratory flow were significantly related to increases in inflation volume, peak inflation pressure, and force with peak expiratory flow increasing by, on average, 4% for every 10% increase in inflation volume (p < .001), 5% for every 10% increase in peak inflation pressure (p = .005), and 3% for each 10 N of applied force (p < .001). By contrast, increase in peak expiratory to inspiratory flow ratio was only related to applied force with a 4% increase for each 10 N of force (p < .001). These results provide evidence of the unique contribution of compression forces in increasing peak expiratory flow and peak expiratory to inspiratory flow ratio bias over and above that related to accompanying changes from manual hyperinflations. Force generated during compression-vibrations was the single significant factor in multivariable analysis to explain the increases in expiratory flow bias. Such increases in the expiratory bias provide theoretically optimal physiological conditions for cephalad mucus movement in fully ventilated children.

Supranormal Expiratory Airflow after Bilateral Lung Transplantation Is Associated with Improved Survival

flow volume loops (FVL) in some bilateral lung transplant (BLT) and heart-lung transplant (HLT) patients suggest variable extrathoracic obstruction in the absence of identifiable causes. These FVLs usually have supranormal expiratory and normal inspiratory flow rates (SUPRA pattern). characterize the relationship of the SUPRA pattern to predicted donor and recipient lung volumes, airway size, and survival. we performed a retrospective review of adult BLT/HLT patients. We defined the SUPRA FVL pattern as: (1) mid-vital capacity expiratory to inspiratory flow ratio (Ve50:Vi50) > 1.0, (2) absence of identifiable causes of extrathoracic obstruction, and (3) Ve50/FVC ≥ 1.5 s(-1). We calculated predicted total lung capacity (pTLC) ratio by dividing the donor pTLC by the recipient pTLC. We measured airway luminal areas on thoracic computer tomographic scans. We compared survival in patients with and without the SUPRA pattern. the SUPRA FVL pattern occurred in 56% of the 89 patients who qualified for the analysis. The pTLC ratio of SUPRA and non-SUPRA patients was 1.11 and 0.99, respectively (P = 0.004). A higher pTLC ratio was correlated with increased probability of the SUPRA pattern (P = 0.0072). Airway luminal areas were larger in SUPRA patients (P = 0.009). Survival was better in the SUPRA cohort (P = 0.009). the SUPRA FVL pattern was frequent in BLT/HLT patients. High expiratory flows in SUPRA patients could result from increased lung elastic recoil or reduced airway resistance, both of which could be caused by the pTLC mismatch. Improved survival in the SUPRA cohort suggests potential therapeutic approaches to improve outcomes in BLT/HLT patients.

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

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). 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. 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). 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.

Vocal cord dysfunction concurrent with a nutcracker esophagus and the role of gastroesophageal reflux disease

Psychological disorders were originally thought to be the sole cause of vocal cord dysfunction (VCD). Subsequently, other organic diseases, including structural laryngeal abnormalities, have also been reported to be associated with VCD. To describe the first patient with VCD concurrent with a nutcracker esophagus and to establish the association between VCD and gastroesophageal reflux disease (GERD) by using the Bernstein test. Symptom assessments, neuropsychiatric evaluations, fiberoptic laryngoscopy, pulmonary function tests, allergic skin prick tests, radiographs of the chest and sinuses, esophageal manometry (including 24-hour ambulatory esophageal pH monitoring), and the Bernstein test were performed. A 36-year-old woman had dyspnea, hoarseness, chest pain, and wheezes without relief for a decade. Neuropsychiatric evaluations disclosed mild depression. Fiberoptic laryngoscopy showed posterior laryngitis and paradoxical vocal cord adduction with audible inspiratory stridor. Pulmonary function tests showed attenuation of the inspiratory limb with notching in both flow-volume loops and a mid-vital capacity expiratory to inspiratory flow ratio of 4. All the symptoms except chest pain were improved dramatically by speech therapy and empirical treatment for GERD. Esophageal manometry revealed a nutcracker esophagus; 24-hour ambulatory esophageal pH monitoring demonstrated multiple short reflux episodes. The Bernstein test was conducted, and all the manifestations were reproduced with 0.1 N hydrochloric acid but not with isotonic sodium chloride infusion. This is the first human case report confirming that GERD can trigger an acute attack of VCD and may induce chest pain as a nutcracker esophagus in patients with VCD. It strengthens this association and expands our knowledge of diverse manifestations of this clinical entity.

Evaluation of respiratory function by barometric whole-body plethysmography in healthy dogs

The objective of the present study was to assess the validity of barometric whole-body plethysmography (BWBP), to establish reference values, and to standardise a bronchoprovocative test to investigate airway responsiveness using BWBP in healthy dogs. BWBP measurements were obtained from six healthy beagle dogs using different protocols: (1) during three consecutive periods (3.5 min each) in two morning and two evening sessions; (2) before and after administration of two protocols of sedation; (3) before and after nebulisation of saline and increasing concentrations of carbachol and histamine both in conscious dogs and in dogs under both protocols of sedation. Enhanced pause (PENH) was used as index of bronchoconstriction. Basal BWBP measurements were also obtained in 22 healthy dogs of different breeds, age and weight. No significant influence of either time spent in the chamber or daytime was found for most respiratory variables but a significant dog effect was detected for most variables. A significant body weight effect was found on tidal volume and peak flow values ( P < 0.05). Response to carbachol was not reproducible and always associated with side effects. Nebulisation of histamine induced a significant increase in respiratory rate, peak expiratory flow, peak expiratory flow/peak inspiratory flow ratio and PENH ( P < 0.05). The response was reproduced in each dog at different concentrations of histamine. Sedation with acepromazine + buprenorphine had little influence on basal measurements and did not change the results of histamine challenge. It was concluded that BWBP is a safe, non invasive and reliable technique of investigation of lung function in dogs which provides new opportunities to characterise respiratory status, to evaluate airway hyperresponsiveness and to assess therapeutic interventions.

Subtotal Carbon Dioxide Laser Arytenoidectomy for the Treatment of Bilateral Vocal Fold Immobility: Long-Term Results

Sixty-nine patients underwent subtotal carbon dioxide laser arytenoidectomy for treatment of bilateral vocal fold immobility between 1985 and 2000. The population included 69 patients whose mean age was 56 years (SD, 16 years; range, 11 to 82 years). The mean follow-up was 50 months (SD, 44 months; range, 1 to 181 months). The overall postoperative peak expiratory/peak inspiratory flow ratio (normal value, 1) significantly improved (closer to 1; p = .0036). Voice analyses were also undertaken for 27 patients, almost exclusively after operation, given the context of initial emergency. The maximum phonation time averaged 6.57 seconds (median, 6 seconds). The phonation quotient remained high, with a mean of 503 (median, 440), and the mean conversational voice intensity remained around 59 dB. The median frequency analysis type was 3. The advantage of subtotal arytenoidectomy lies in the fact that it maintains a certain degree of rigidity along the posterior limit of the arytenoid frame, preventing inward collapse of the mucosa and thus lowering the risk of aspiration.

Detection of inspiratory flow limitation during sleep by computer assisted respiratory inductive plethysmography.

The potential of respiratory inductive plethysmography (RIP) to detect inspiratory flow limitation during sleep was investigated. Sixteen sleep apnoea patients underwent polysomnography. Airflow by a flowmeter attached to a nasal mask, oesophageal and mask pressure were recorded along with calibrated RIP. Presence of inspiratory flow limitation was defined by constant or decreasing flow without pressure dependence throughout significant portions of inspiration, its absence by a linear or mildly alinear pressure:airflow relationship. Based on this standard, three of various computerized RIP derived parameters, with highest performance to detect flow limitation, were identified. They were combined to an inspiratory flow limitation, (IFL)-Index(RIP), which was validated prospectively in another 10 sleep apnoea patients. RIP derived fractional inspiratory time, peak to mean inspiratory flow ratio, and ribcage contribution to tidal volume had the highest accuracy to detect flow limitation (area under the receiver operating characteristic (ROC) curves 0.81, 0.76, 0.76, respectively, 160 comparisons). Prospective validation revealed an area under the ROC curve for the IFL-Index(RIP) to detect flow limitation of 0.89 (95% confidence interval 0.85 to 0.93, 200 comparisons) with sensitivity and specificity at the point of equality of 80%. It is concluded that inspiratory flow limitation may be assessed by computer assisted analysis of respiratory inductive plethysmography derived breathing patterns with clinically acceptable accuracy.

Subtotal Carbon Dioxide Laser Arytenoidectomy by Endoscopic Approach for Treatment of Bilateral Cord Immobility in Adduction

Subtotal carbon dioxide (CO2) laser arytenoidectomy for endoscopic treatment of bilateral immobility of the vocal folds in adduction is a variant of total arytenoidectomy. The principal modification involves preservation of a thin posterior shell providing good postoperative fixation of the arytenoid region. The risk of aspiration is thus averted and collapse of arytenoid mucosa into the larynx during inspiration is prevented. The risk of synechia with the posterior commissure is avoided. The CO2 laser is operated at a working distance of 400 mm with a continuous 7-W beam in superpulse mode. Operation time is thus reduced to approximately half an hour and the risk of postoperative edema is reduced. Tracheotomy is not necessary. Forty-one patients, including 16 men and 25 women, were treated by this technique between 1985 and 1994. Their mean age was 55 +/- 17 years, ranging from 11 to 83 years. Follow-up ranged from 1 month to 111 months (9 years 3 months), with a mean of 56 +/- 29 months (4 years 8 months). The mean peak forced expiratory flow-peak inspiratory flow ratio (normal = 1), which permits a measurement of respiratory quality, is improved from 3.7 +/- 1.4 preoperatively to 1.6 +/- 0.5 postoperatively (p<.001). Postoperative voice measurements show a mean vocal intensity of 61 +/- 3 dB hearing level, a mean maximum phonation time of 8 +/- 4 seconds, and a mean phonation quotient of 397 +/- 150 mL/s. As for vocal quality, 38% of the patients now have a near-normal voice according to our high-resolution frequency analysis, and all of the patients retained satisfactory voice quality.

Posterior cordectomy and subtotal arytenoidectomy for the treatment of bilateral vocal fold immobility: functional results.

We report vocal and respiratory results following endoscopic CO2 laser therapy for bilateral vocal fold immobility in adduction. Two techniques were used: posterior cordectomy (PC) and subtotal arytenoidectomy (SA). Respiratory improvement was demonstrated by the peak expiratory flow/peak inspiratory flow ratio (PEF/PIF, normal = 1), which was less than 2 for 83% of patients following PC and for 81% following SA. As for vocal results, there were no significant quantitative differences between the two techniques. Mean maximum phonation time (/a/) was 6.8 +/- 2.6 s after SA and 7.8 +/- 1.6 s following PC. The phonation quotient was 288 +/- 116 ml/s after SA and 304 +/- 92 ml/s after PC. Mean vocal intensity was 62 +/- 4 dB after SA and 59 +/- 3 dB after PC. Vocal quality was measured by high-resolution vocal frequency analysis, as represented by a histogram. Peaks corresponding to fundamental frequency and first harmonics were preserved in more than 60% of patients in the two groups. Vocal preservation is better when the paralyzed folds are in the paramedian position, with the possibility of adduction (Gerhardt syndrome). SA is performed in our procedure, though it is longer and more difficult to perform than PC. PC often requires two procedures to achieve satisfactory results.