Peak Cough Flow Fails to Detect Upper Airway Collapse During Negative Pressure Titration for Cough-Assist.

OBJECTIVE: To study the ability of peak cough flow (PCF) and effective cough volume, defined as the volume exsufflated >3 L/s, to detect upper airway collapse during mechanical insufflation-exsufflation (MI-E) titration in neuromuscular patients. DESIGN: Prospective observational study. SETTING: Rehabilitation hospital. PARTICIPANTS: Patients (N=27) with neuromuscular disease causing significant impairment of chest wall and/or diaphragmatic movement. INTERVENTIONS: The lowest insufflation pressure producing the highest inspiratory capacity was used. Exsufflation pressure was decreased from -20 cm H2O to -60/-70 cm H2O, in 10-cm H2O decrements, until upper airway collapse was detected using the reference standard of flow-volume curve analysis (after PCF, abrupt flattening or flow decrease vs previous less negative exsufflation pressure). MAIN OUTCOME MEASURES: PCF and effective cough volume profiles during expiration with MI-E. RESULTS: Upper airway collapse occurred in 10 patients during titration. Effective cough volume increased with decreasing expiratory pressure then decreased upon upper airway collapse occurrence. PCF continued to increase after upper airway collapse occurrence. In 5 other patients, upper airway collapse occurred at the initial -20 cm H2O exsufflation pressure, and during titration, PCF increased and effective cough volume remained unchanged at <200 mL. PCF had 0% sensitivity for upper airway collapse, whereas effective cough volume had 100% sensitivity and specificity. CONCLUSION: Of 27 patients, 15 experienced upper airway collapse during MI-E titration. Upper airway collapse was associated with an effective cough volume decrease or plateau and with increasing PCF. Accordingly, effective cough volume, but not PCF, can detect upper airway collapse.

Comparison of three cough-augmentation techniques in neuromuscular patients: mechanical insufflation combined with manually assisted cough, insufflation-exsufflation alone and insufflation-exsufflation combined with manually assisted cough.

BACKGROUND: Mechanical insufflation-exsufflation (MI-E), more commonly known as 'cough assist therapy', is a method which produces inspiratory and expiratory assistance to improve cough performances. However, other alternatives or combinations are possible. OBJECTIVE: The objective was to compare the effects of mechanical insufflation combined with manually assisted coughing (MAC), insufflation-exsufflation alone and insufflation-exsufflation combined with MAC in neuromuscular patients requiring cough assistance. METHODS: Eighteen neuromuscular patients with severe respiratory muscle dysfunction and peak cough flow (PCF) lower than 3 liters/s or maximal expiratory pressure (MEP) lower than +45 cm H2O were studied. Patients were studied under three cough-assisted conditions, which were used in random order: insufflation by intermittent positive-pressure breathing (IPPB) combined with MAC, MI-E and MI-E + MAC. RESULTS: Overall, PCF was higher with IPPB + MAC than with MI-E + MAC or MI-E alone. Among the 12 patients who had higher PCF values with IPPB + MAC than with the two other techniques, 9 exhibited mask pressure swings during MI-E exsufflation, with a transient positive-pressure value due to the expiratory flow produced by the combined patient cough effort and MAC. Each of these 9 patients had higher PCF values (>5 liters/s) than did the other 9 patients when using IPPB + MAC. CONCLUSION: Our results indicate that adding the MI-E device to MAC is unhelpful in patients whose PCF with an insufflation technique and MAC exceeds 5 liters/s. This is because the expiratory flow produced by the patient's effort and MAC transitorily exceeds the vacuum capacity of the MI-E device, which therefore becomes a transient load against the PCF.

Longitudinal high-resolution imaging through a flexible intravital imaging window.

Intravital microscopy (IVM) is a powerful technique that enables imaging of internal tissues at (sub)cellular resolutions in living animals. Here, we present a silicone-based imaging window consisting of a fully flexible, sutureless design that is ideally suited for long-term, longitudinal IVM of growing tissues and tumors. Crucially, we show that this window, without any customization, is suitable for numerous anatomical locations in mice using a rapid and standardized implantation procedure. This low-cost device represents a substantial technological and performance advance that facilitates intravital imaging in diverse contexts in higher organisms, opening previously unattainable avenues for in vivo imaging of soft and fragile tissues.

Comparison of Two Cough-Augmentation Techniques Delivered by a Home Ventilator in Subjects With Neuromuscular Disease.

BACKGROUND: Breath-stacking, which consists of taking 2 or more consecutive ventilator insufflations without exhaling, is a noninvasive and inexpensive cough-assistance technique for patients with neuromuscular disease. Volumetric cough mode (VCM) is a recently introduced ventilator mode consisting of a programmable intermittent deep breath equal to a set percentage of the baseline tidal volume. Here, our objective was to compare VCM to breath-stacking during volume-control continuous mandatory ventilation in subjects on long-term noninvasive mechanical ventilation at home. METHODS: We included 20 subjects with neuromuscular disease causing severe respiratory muscle dysfunction with a cough peak flow (CPF) < 270 L/min or maximum expiratory pressure < 45 cm H2O. Each subject tested breath-stacking and VCM in random order. RESULTS: CPF increased with both techniques but was higher with VCM than with breath-stacking in 16 subjects. In 17 subjects, CPF was highest with the technique that produced the greatest inspiratory capacity. CONCLUSION: Our results indicate that both breath-stacking and VCM are useful cough-augmentation techniques. Displaying insufflated volumes on the ventilator screen is a simple and accessible method for selecting the most efficient cough-augmentation technique delivered by a home ventilator.

Assisted vital capacity to assess recruitment level in neuromuscular diseases.

Respiratory muscle weakness and chest wall abnormalities in neuromuscular diseases (NMD) may lead to decreased pulmonary volumes. We assessed the reversibility of vital capacity (VC) reduction with mechanical In-Exsufflation (MI-E). We evaluated the effects of positive inspiratory and negative expiratory pressures on spirometric variables under passive (without patients' participation) and active (with active participation) application in 47 NMD patients. VC, inspiratory capacity (IC), expiratory reserve volume (ERV) were measured during maneuvers without and with MI-E assistance, delivering inspiratory assistance (+40cmH2O), expiratory assistance (-40cmH2O) and both (±40cmH2O). Passive and active assistance improved significantly VC and IC compared to baseline (P<0.0001 for both). ERV improved only with active assistance which normalized VC in 10, IC in 18 and ERV in 6 patients, mainly in patients with late-onset NMD. MI-E assistance produced greater increases in IC than in ERV, resulting in a VC increase enhanced by patients' active participation. This type of evaluation may help to evaluate the potential reversibility of restrictive ventilatory pattern in NMDs.