The Effect of Pressure Changes During Mechanical Insufflation-Exsufflation on Respiratory and Airway Physiology

BACKGROUND

Respiratory muscle weakness can impair cough function, leading to lower respiratory tract infections. These infections are an important contributor to morbidity and mortality in patients with neuromuscular disease. Mechanical insufflation-exsufflation (MIE) is used to augment cough function in these patients. Although MIE is widely used, there are few data to advise on the optimal technique. Since the introduction of MIE, the recommended pressures to be delivered have increased. There are concerns regarding the use of higher pressures and their potential to cause lung derecruitment and upper airway closure.

RESEARCH QUESTION

What is the impact of high-pressure MIE (HP-MIE) on lung recruitment, respiratory drive, upper airway flow, and patient comfort, compared with low-pressure MIE (LP-MIE), in patients with respiratory muscle weakness?

STUDY DESIGN AND METHODS

Clinically stable patients using domiciliary MIE with respiratory muscle weakness secondary to Duchenne muscle dystrophy, spinal cord injury, or long-term tracheostomy ventilation received LP-MIE (30/-30 cm H2O) and HP-MIE (60/-60 cm H2O) in a random sequence. Lung recruitment, neural respiratory drive, and cough peak expiratory flow were measured throughout, and patients reported comfort and breathlessness following each intervention.

RESULTS

A total of 29 patients (10 with Duchenne muscle dystrophy, eight with spinal cord injury, and 11 with long-term tracheostomy ventilation) were included in this study. HP-MIE augmented cough peak expiratory flow compared with LP-MIE (mean cough peak expiratory flow HP-MIE 228 ± 81 L/min vs LP-MIE 179 ± 67 L/min; P = .0001) without any significant change in lung recruitment, neural respiratory drive, or patient-reported breathlessness. However, in patients with more pronounced respiratory muscle weakness, HP-MIE resulted in an increased rate of upper airway closure and patient discomfort that may have an impact on clinical efficacy.

INTERPRETATION

HP-MIE did not lead to lung derecruitment or breathlessness compared with LP-MIE. However, it was poorly tolerated in individuals with advanced respiratory muscle weakness. HP-MIE generates more upper airway closure than LP-MIE, which may be missed if cough peak expiratory flow is used as the sole titration target.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT02753959; URL: www.

CLINICALTRIALS

gov.

Evaluation of a Closed Suction System with Integrated Tube Scraping Technology: A Randomized Controlled Trial

BACKGROUND: Endotracheal tube (ETT) scraping or sweeping refers to mucus removal from an ETT that can increase airway resistance. The study objective was to evaluate the effect of ETT scraping on the duration of mechanical ventilation (MV), time to first successful spontaneous breathing trial (SBT), duration of hospital stay, and occurrence of ventilator-associated events (VAE).METHODS: This was a single-center, randomized clinical trial of adult subjects intubated between October 2019 and October 2021. Subjects were randomly assigned to either ETT suctioning via a standard in-line suction catheter (control group) or ETT suctioning and scraping via a suction catheter with balloon sweeping technology (experimental group). Airway suctioning was performed as clinically indicated, and ETT was scraped every time a respiratory therapist suctioned the patient. The study outcome was duration of MV, time to first successful SBT, hospital stay, and VAE rate. Intent to treat statistical analysis was performed.RESULTS: Of 272 randomized subjects, the median age was 63 (IQR 52-73) years, 143 (53%) were males, and 154 (57%) had a primary diagnosis of acute respiratory failure. There were no significant differences between the groups in median duration (hours) of MV [72.2 (37-187) vs 70.6 (37-148); P = 0.58]. There was no significant difference between the study groups in median time (hours) to the first successful SBT [46.7 (IQR 30-87) vs 45.7 (IQR 27-95), P = 0.81], length of hospital stay (P = 0.76), the incidences of ventilator-associated conditions (P = 0.13), or infection-related ventilator-associated complications (P = 0.47).CONCLUSION: ETT suctioning plus scraping, compared to ETT suctioning alone, did not significantly improve the duration of mechanical ventilation, time to first successful SBT, length of hospital stay, and VAE. These study findings do not support the routine use of ETT scraping for mechanically ventilated patients.

Comparison of 6 Oscillatory Positive Expiratory Pressure Devices During Active Expiratory Flow

BACKGROUND

Air-flow oscillations generated by exhaling through oscillatory positive expiratory pressure (OPEP) devices favor airway clearance. Variations in mechanical properties between different devices may influence therapeutic efficacy. The objective of this study was to assess mechanical properties in vitro and to compare the performance of 6 OPEP devices at different resistance levels under active expiratory flow patterns.

METHODS

4 gravity-dependent OPEP devices (ie, Flutter, Gelomuc, Pari O-PEP, Shaker Medic Plus) and 2 gravity-independent OPEP devices (ie, Acapella Choice and Aerobika) were each tested at low, medium, and high resistance settings. All devices were independently connected to a pulmonary waveform generator that reproduced active exhalation flows. Expiratory flow-volume curves were retrieved from 4 subjects with different stages of obstruction severity and were scaled according to either peak expiratory flow (4, 6, and 8 L/s) or volumes (2, 3 and 4 L), thus amounting to 24 active exhalations. Resulting waveforms were divided into 4 parts and the 2 middle parts were used to extract the following mechanical data: positive expiratory pressure (PEP), maximum expiratory pressure (P_peak), oscillation frequency, and flow oscillation amplitude. The percentage of tests achieving oscillation frequencies ≥ 12 Hz and PEP ≥ 10 cm H₂O was calculated for each device.

RESULTS

Mechanistic effects of the Acapella, Aerobika, and Shaker devices were not comparable. The Flutter, Gelomuc, and Pari devices behaved similarly and achieved more tests with optimum oscillation frequency and PEP values than the other devices. These 3 devices also produced the highest oscillation amplitudes at the low-resistance level, whereas the Aerobika elicited higher and consistent oscillation amplitudes at medium and high resistance settings.

CONCLUSIONS

Operational parameters differed between and within devices, yet the Flutter, Gelomuc, and Pari devices were similar in many aspects. Therapeutic efficacy may depend on the selected OPEP device and set resistance.

Should Early Prone Positioning Be a Standard of Care in ARDS With Refractory Hypoxemia?

For the past 4 decades, the prone position has been employed as an occasional rescue option for patients with severe hypoxemia unresponsive to conventional measures applied in the supine orientation. Proning offers a high likelihood of significantly improved arterial oxygenation to well selected patients, but until the results of a convincing randomized trial were published, its potential to reduce mortality risk remained in serious doubt. Proning does not benefit patients of all disease severities and stages but may be life-saving for others. Because it requires advanced nursing skills and escalation of monitoring surveillance to deploy safely, its place as an early stage standard of care depends on the definition of that label.

Airway clearance therapy: finding the evidence

Disease processes can impair ciliary function, alter secretion production and mucus rheology, and interfere with the cough reflex. Airway clearance therapy has been a cornerstone of therapy aimed at minimizing the devastating effects of airway obstruction, infection, and inflammation due to mucus stasis on the conducting airways and lung parenchyma. Although challenges to performing clinical studies evaluating the effectiveness of airway clearance therapeutic modalities exist, resources are available in the literature. In addition to device evaluations and original clinical research, the expert opinion, systematic reviews, and evidence-based practice guidelines can be found. These tools can be used to develop protocols and pathways to guide our practice. Monitoring and reporting patient, process, and financial outcomes are essential steps germane to the implementation of evidence-based care.

High-frequency chest wall compression therapy in neurologically impaired children

BACKGROUND

Children with neurological impairment often suffer from insufficient airway secretion clearance, which substantially increases their respiratory morbidity. The goal of the study was to assess the clinical feasibility of high-frequency chest wall compression (HFCWC) therapy in neurologically impaired children with respiratory symptoms.

METHODS

This was a single-center, investigator initiated, prospective study. Twenty-two subjects were studied for 12 months before and 12 months after initiation of HFCWC therapy, and 15 subjects were followed for an additional 12 months. The threshold of adherence to HFCWC therapy was 70%. The number of pulmonary exacerbations that required hospitalization was recorded.

RESULTS

Forty-five percent of the subjects required hospital admission before initiation of HFCWC therapy. This rate decreased to 36% after the first year with HFCWC, and to 13% after the second year with HFCWC. There was a statistically significant reduction of the number of hospital days at follow-up, relative to before treatment. Use of an assisted-cough device or the presence of tracheostomy did not significantly affect hospitalization days.

CONCLUSIONS

Regular HFCWC therapy may reduce the number of hospitalizations in neurologically impaired children.

Bench assessment of a new insufflation-exsufflation device

BACKGROUND

The Nippy Clearway is a new mechanical insufflation-exsufflation device used to assist cough.

METHODS

We compared the peak expiratory flow (PEF) with the Nippy Clearway versus the CoughAssist in a bench experiment. The relationship between PEF and pressure at the airway opening during exsufflation (minimum expiratory PAO) was investigated under 6 combinations of compliance (30 or 60 mL/cm H2O) (C30 and C60) and resistance (0, 5, or 20 cm H2O/L/s) (R0, R5, and R20) over a 25-50 cm H2O range of set P(AO). The intercepts and slopes of the linear regression performed over PEF and P(AO) relationships were compared for both devices.

RESULTS

For the C30R0, C30R5, and C60R5 conditions, the change in both the intercepts and slopes was significant with the Nippy Clearway, compared to the CoughAssist, averaging -2.96 L/s and -0.03 L/s/cm H2O, -1.46 L/s and 0.02 L/s/cm H2O, and -1.02 L/s and -0.04 L/s/cm H2O, respectively. As a result, at any minimum expiratory P(AO), PEF was significantly greater with the Nippy Clearway. For C30R20 and C60R20, the regression lines were similar for the Nippy Clearway and CoughAssist.

CONCLUSIONS

In this bench study, PEF with the Nippy Clearway was greater than with the CoughAssist at low respiratory-system compliance.