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Mechanical exsufflation, noninvasive ventilation, and new strategies for pulmonary rehabilitation and sleep disordered breathing.

Manual and mechanical exsufflation are important but underutilized ways to clear airway secretions. These methods are especially useful when used in concert with noninvasive intermittent positive airway pressure ventilatory assistance to facilitate extubation and ventilator weaning. This can be used as much as 24 hours a day as an alternative to tracheostomy ventilation or body ventilator use for patients with paralytic restrictive ventilatory insufficiency. These techniques expedite community management of ventilator assisted individuals by avoiding tracheostomy and need for invasive suctioning and ongoing wound care. For these techniques to be effective and to prevent further suppression of ventilatory drive, supplemental oxygen administration must be avoided unless pO2 is less than 60 mm Hg despite normalization of pCO2. Custom molded interfaces for the delivery of noninvasive intermittent positive airway pressure ventilatory assistance can also be used to facilitate the delivery of variable inspiratory expiratory positive airway pressure for patients with obstructive sleep apnea. Noninvasive intermittent positive airway pressure ventilatory assistance or body ventilator use can rest the respiratory muscles of patients with advanced chronic obstructive pulmonary disease. This and pulmonary rehabilitation programs geared to exercise reconditioning are therapeutic options that significantly improve the quality of life of these patients. For both paralytic restrictive and obstructive pulmonary patients, these techniques decrease cost and frequency of hospitalizations.

Humans

Interventions with a significant mortality difference in acute respiratory distress syndrome: A systematic review and comparison with Guidelines.

INTRODUCTION: Acute respiratory distress syndrome (ARDS) has a high mortality rate. European Society of Intensive Care Medicine (ESICM) and American Thoracic Society (ATS) Guidelines are the worldwide reference for clinicians in management of ARDS. Mortality represents one of the most important outcomes in intensive care practice and randomized controlled trials (RCTs) the highest level of evidence. We compared Guidelines recommendations with RCT results to highlight differences and find potential new therapeutic opportunities. METHODS: We performed a systematic review of all RCTs reporting a statistically significant mortality difference in ARDS and a subsequent comparison with ESICM and ATS Guidelines recommendations. RESULTS: We identified 33 RCTs and 23 interventions with mortality difference in ARDS patients. Seven interventions relate to invasive ventilation strategies, two to noninvasive ventilation strategies, one to extracorporeal membrane oxygenation (ECMO), 12 to drugs and one to nutritional support. In 25/33 (76%) RCTs the intervention was associated with mortality reduction and in 8/33 with mortality increase (24%). Multicenter studies were 24/33 (73%) while blinding was adopted in 19/33 (58%) studies. Guidelines recommendations supported by RCTs with mortality impact include: the use of low tidal volume ventilation, prone positioning, venovenous ECMO, steroids and the avoidance of high frequency oscillatory ventilation. Eight of the interventions identified were not mentioned by Guidelines but demonstrated reduced mortality, and five further interventions demonstrated increased mortality. CONCLUSIONS: This systematic review highlights potential gaps between RCTs results and Guidelines that could be used to plan future research or highlight topics to be discussed in future Guidelines.

Humans

Triggering modalities to synchronise non-invasive respiratory support in preterm infants: a systematic review and meta-analysis.

BACKGROUND: Increasing evidence suggests that synchronised nasal intermittent positive pressure ventilation (sNIPPV) may be the optimal mode of non-invasive respiratory support. However, no comprehensive review of sNIPPV modes is available. This review aims to describe different synchronisation methods for sNIPPV and compare their effectiveness in clinical, physiological and technical outcomes with other modes of non-invasive respiratory support. METHODS: This review identified all clinical studies in preterm infants that compared sNIPPV to other non-invasive respiratory support modes or compared different trigger modalities between 1990 and 2026. A search was carried out in MEDLINE, Embase and the Cochrane Library. Main outcomes were categorised as clinical (eg, extubation failure (EF)), physiological (eg, breathing effort) and technical (eg, synchronisation rate). RESULTS: 49 studies (2864 infants) were included, with a low to moderate risk of bias. Meta-analysis showed a reduction in EF (risk ratio=0.38; 95% CI 0.17 to 0.85; p=0.03) in favour of sNIPPV compared with nasal continuous positive airway pressure (nCPAP). Physiological outcomes were significantly improved during sNIPPV compared with nCPAP and nasal intermittent positive pressure ventilation (NIPPV), especially breathing effort. When reviewing technical outcomes, non-invasive neurally adjusted ventilatory assist showed lower patient-ventilator asynchrony (PVA) (index ranging from 7% to 50%), a higher synchronisation rate (80%-99%) and a shorter trigger delay (35 ms) compared with other sNIPPV modes. CONCLUSIONS: This review shows that synchronising NIPPV results in consistent physiological (reduced patient effort) and technical benefits (reduced PVA). However, evidence on positive effects on (long-term) major clinical outcomes remains limited and requires further studies. PROSPERO REGISTRATION NUMBER: CRD420251022479.

Humans

Ventilation-perfusion ratio obtained by a noninvasive frequency response technique.

Results of animal experiments using sinusoidal changes in inspired halothane concentration showed that the ratio of variation in end-expired concentration to the variation in inspired concentration reached a plateau in the Bode diagram. With the help of an uptake and distribution model, the interpretation of the results showed that the level of the plateau is determined by the overall ventilation-perfusion ratio. With a good selection of input frequency, tracer agent, and known ventilation, the ventilation-perfusion ratio and the lung perfusion can be consequently obtained noninvasively. Mean ventilation-perfusion ratio was determined with 20 human voluteers. At rest a mean ratio was found of 0.87 +/- 0.28 (SD). At a work load of 90 W a mean ratio was found of 1.19 +/- 0.19 (SD). In two individuals reproducibility and influence of CO2 was studied. At rest without additional CO2 the ventilation-perfusion ratio was 0.71 +/- 0.06 (SD) obtained with a constant breathing rate of 10/min. At an end-expired CO2 level of 6% the ventilation-perfusion ratio was increased almost 2.5 times. The calculated perfusion with and without increased end-expired CO2 levels under the same work load were well reproducible.

Carbon Dioxide

Maturation of ventilation and ventilatory pattern in normal sleeping infants.

Noninvasive studies of ventilation and ventilatory pattern were performed serially in 15 normal infants in the first 4 mo of life during REM and quiet sleep with the barometric method. We measured tidal volume (VT), total respiratory cycle time (Ttot), inspiratory time (Ti), expiratory time (TE), mean inspiratory flow (VT/TI), and respiratory "duty cycle" (TI/Ttot). Vt, Ttot, TI, TE, VT/TI, and VT/Ttot but not TI/Ttot increased with age. In all age groups, Ttot, TI, and TE but not VT/TI were greater in quiet than in REM sleep. In the first 2 mo of life, VT was greater in quiet than in REM sleep; in the older infants, VT/Ttot was smaller in quiet than in REM sleep. TI/Ttot was not dependent on sleep state. Thus, because VT/Ttot = VT/TI X TI/Ttot, the increase in VT/Ttot with age results from an increase in mean inspiratory flow rather than from changes in respiratory "duty cycle". Further, the "on-switching" as well as the "off-switching" of inspiratory activity depends on sleep state.

Aging

High-Flow Nasal Oxygen Versus Conventional Oxygen Therapy and Non-Invasive Ventilation for Acute Respiratory Failure in the Emergency Department: A Systematic Review and Meta-Analysis.

This systematic review and meta-analysis compares the use of high-flow nasal oxygen (HFNO) with conventional oxygen therapy (COT) and non-invasive ventilation (NIV) in the management of acute respiratory failure (ARF) in the emergency department (ED). A comprehensive search of relevant sources was undertaken. Randomised controlled trials (RCTs) assessing adult patients (≥ 18 years) treated in the ED for ARF and comparing HFNO to COT/NIV were included. The primary outcome was the need for endotracheal intubation and mechanical ventilation (IMV). Secondary outcomes included physiological and biochemical parameters, ICU admission, hospital length of stay, dyspnoea scores and mortality. A total of 17 RCTs (1955 patients) were included. There was a significant reduction in IMV favouring the HFNO group compared to COT and NIV (RR 0.64, 95% CI 0.47-0.88). HFNO showed significant improvements in RR, SpO2, PaO2 and Modified Borg Dyspnoea Scale. Subgroup analysis showed reduced rates of IMV with HFNO compared to COT (RR 0.61, 95% CI 0.41-0.91), but not compared to NIV (RR 0.69, 95% CI 0.42-1.14). HFNO additionally showed a reduction of IMV compared to NIV and COT in undifferentiated patients (RR 0.61, 95% CI 0.41-0.93), but not in exacerbations of COPD or acute heart failure. Ten of the 17 studies had at least some concern for risk of bias, with several analyses having notable heterogeneity. HFNO showed a significant reduction in rates of IMV, improvement in peripheral oxygen saturations, PaO2, respiratory rate and patient dyspnoea scores compared to COT and NIV.

Humans

Rebreathing pulmonary capillary and tissue volume in normals after saline infusion.

A rebreathing technique was utilized to assess changes in diffusing capacity (DCO), pulmonary capillary blood volume (Vc), pulmonary parenchymal tissue volume (Vt), and cardiac output (Qc), after infusion of 2 liters of 0.9% saline intravenously in 13-25 min in five healthy subjects. Blood hemoglobin concentration decreased an average of 17%. Vc increased strikingly in all five subjects. No significant changes in Vt, or in Vt per unit lung volume were observed. Radiographic evidence of interstitial pulmonary edema was present in four of the five subjects. Radiographic total lung capacity was reduced significantly in four of the five subjects. Significant reductions in forced vital capacity (FVC), forced expiratory volume in 1.0 and 3.0 s, and mean forced expiratory flow during the middle half of the FVC occurred in three of the five subjects. No dyspnea, cough, or physical examination abnormalities of lungs or heart occurred. This noninvasive, ventilation-limited, rebreathing technique appears capable of detecting early changes in pulmonary congestion, at a time when definitive radiographic changes and changes in the physical examination are absent. It appears capable of detecting the increase in Vc associated with hypervolemia in man.

Adult

Walker modification for ventilator-assisted individuals. Case report.

A case is presented of a 53-yr-old ambulatory ventilator-dependent individual who demonstrated that functional ambulation could be possible with a modified rolling walker. The patient used intermittent positive pressure ventilation delivered by noninvasive methods 24 h a day. For potentially ambulatory ventilator users, intensive rehabilitation and the use of a modified walker can improve medical, psychological and social status and permit the resumption of vocational activities. Mouth intermittent positive pressure ventilation is the method of choice for daytime ventilatory support during ambulation for individuals with severe chronic alveolar hypoventilation because of predominantly restrictive pulmonary syndromes.

Activities of Daily Living

Psychosocial adjustment of post-poliomyelitis ventilator assisted individuals.

The effect of severe disability, tracheostomy, and ventilator use on psychosocial functioning, gainful employment, life satisfaction, and perceived well-being were studied for a population of 395 ventilator assisted post-poliomyelitis individuals (PVAIs). Standard psychosocial survey instruments and other general questioning were used. Two-hundred-seventy-three physically intact health care professionals served as controls. They were surveyed about their own life satisfaction and perceived well-being and were asked to judge how severely disabled ventilator assisted individuals would respond to such questioning. The relative distress associated with ventilator use was also evaluated in a similar manner. Fifty six of 380 responding PVAIs (14.7%) expressed dissatisfaction with their lives in general. This compares with 8.5% of the controls and 7% of a previously studied general population. The controls significantly underestimated the patients' life satisfaction and well-being scores and significantly overestimated the relative hardship associated with ventilator use. The post-polio individuals using noninvasive methods of assisted ventilation were also significantly more satisfied with their lives than were those ventilated via tracheostomy. Fifty-seven of 148 (39%) individuals married and 165 of 395 (42%) individuals were gainfully employed during long-term ventilator use. We conclude that many severely disabled post-poliomyelitis ventilator users lead productive lives. The vast majority have a positive affect and are satisfied with life. Noninvasive ventilatory support alternatives may lend to greater life satisfaction for these individuals than ventilation delivered via an indwelling tracheostomy. Health care professionals may significantly underestimate their patients' satisfaction with life and this may have a bearing on patient management.

Adult

Breathing patterns during varied activities.

The level of ventilation attained and breathing patterns adopted during activity have important implications for the distribution and deposition of particles that are inhaled. However, breathing patterns and levels of ventilation adopted during specific physical activities are unknown. We used a noninvasive means of measuring ventilation in subjects performing a variety of activities (bicycling, arm ergometry, lifting, and pulling) during unencumbered (no mouthpiece) breathing and while breathing through a mouthpiece. Minute ventilation (VE), tidal volume (VT), inspiratory time (TI), and total breathing cycle time (TT) were measured initially both spirometrically and from body surface displacements. When a mouthpiece was used, VE and breathing patterns were significantly altered during all activities such that VE, VT, and TT increased by 16, 34, and 20%, respectively. This mouthpiece effect was attenuated at the higher levels of VE. A task dependency of breathing pattern was also noted such that there was much greater variability of VT and TI for a given VE during the lifting activity compared with bicycling (coefficient of variation for VT of 0.39 +/- 0.09 vs. 0.20 +/- 0.07, P less than 0.01; and for TI of 0.38 +/- 0.08 vs. 0.21 +/- 0.08, P less than 0.01). We conclude that a mouthpiece significantly alters breathing pattern during varied types and intensities of activities, and breathing patterns may differ significantly from one activity to another. When the total dose of particulates inhaled in the lung are assessed, the mouthpiece effect and activity effect on breathing pattern must be considered.

Adult

The diagnosis of acute pulmonary embolism in patients with chronic obstructive pulmonary disease.

The clinical features and noninvasive tests, including ventilation perfusion (V/Q) lung scans, were assessed in 108 patients with chronic obstructive pulmonary disease (COPD) suspected of having pulmonary embolism (PE). Twenty-one (19 percent) of 108 patients had PE. In the majority of patients, it was impossible to distinguish between patients with and without PE by clinical assessment alone. However, when a high clinical index of suspicion was present, PE was confirmed by angiography in three of three patients, but the V/Q scan was of intermediate probability. No roentgenographic abnormalities distinguished between PE and no PE. There was no difference between the alveolar-arterial oxygen gradients in either group, nor was there evidence of a reduction in the PaCO2 in patients with PE who had prior hypercapnia. Among the 108 patients with COPD, high, intermediate, low, and normal/near normal probability scans were present in 5 percent, 60 percent, 30 percent, and 5 percent, respectively. The frequency of PE in these V/Q scan categories was five (100 percent) of five, 14 (22 percent) of 65, two (6 percent) of 33, and zero (0 percent) of five, respectively. In conclusion, in the majority of patients, the V/Q scan diagnosis is usually intermediate and such patients require further investigational studies, including angiography. However, among the few patients who demonstrated a high probability lung scan, there was a high positive predictive value for PE effectively avoiding the need for further studies. In those patients with low probability or near normal/normal V/Q scans, the negative predictive value was not lower than the general hospital population.

Acute Disease

Ventilation of the paranasal sinuses studied with dynamic emission computer tomography.

This investigation's aim was to study a noninvasive method for determining the ventilation of the nasal sinuses. For this purpose, different insufflation techniques using xenon 133 were tried, along with different scintillation camera techniques. Xenon 133 gas was used for insufflation in the nose and sinuses, and the half-time of the washout curves was determined with the aid of digital scintillation cameras, one of which was capable of dynamic tomography. The tomographic procedure was superior because it made it possible to study the washout from the ethmoidal/sphenoidal sinuses as well. The washout was followed for up to 150 minutes. Great variations in washout were found between different sinuses and also in the same sinus over time. The single photon emission computed tomography (SPECT) technique, which is easy to perform and gives a limited absorbed dose to the patient, seems promising for the future evaluation of sinus ventilation and ostial function.

Absorption

Ventilator use by muscular dystrophy association patients.

Two hundred seventy-three Muscular Dystrophy Association (MDA) clinic directors and codirectors of 167 of the 220 clinics responded to a survey designed to study patterns of use of mechanical ventilation. Ventilatory assistance was recommended and used on an elective basis in 43 of the 167 clinics. In 68 clinics, the policy was to discourage its use, and 62 clinics were managing no ventilator users at the time of the survey. The most common reason given for discouraging ventilator use was poor patient quality of life. Only two physicians who discouraged use of mechanical ventilation were familiar with newly described methods of noninvasive ventilatory aid. The clinic directors were also asked to estimate the satisfaction with life of Duchenne muscular dystrophy (DMD) ventilator users. Eighty DMD ventilator users also responded to a separate and identical life satisfaction survey. The clinic directors significantly underestimated the users' reported life satisfaction. The directors who discouraged ventilator use more significantly underestimated the users' life satisfaction than those who recommended it. We conclude that the MDA clinic directors' estimation of ventilator users' quality of life and satisfaction with life is positively correlated with the likelihood of their discussing and recommending ventilator use to prolong life. Despite the wider recognition and availability of more convenient noninvasive methods of ventilatory assistance, the use of mechanical ventilation by MDA clinics has not changed significantly since 1985.

Adult

Dynamic pulmonary imaging: performance properties of a digital fluoroscopy system.

The physical characteristics of dynamic pulmonary imaging with digital fluoroscopy, which differ from those in DSA equipment, have been determined. The spectral distributions and mean energies were calculated and corresponding exposures with varying high voltage and copper filtration (60-100 kVp, 0-2.83 mm Cu) were measured. The utilization of 90-100 kVp with a filter consisting of 1.39 mm Cu and 3 mm Al minimized disturbing skeletal artifacts and reduced the radiation exposure by a factor of approximately 5 in comparison with imaging at 60 kVp without copper filtration. Simultaneously, the measured signal decreased by about 25%. The mean energy of this spectrum exceeded that of 140 kVp chest imaging. The dynamic pulmonary imaging method produces logarithmically transformed x-ray transmittance values linearly related (r = -0.999) to water thickness between 7-10.5 cm, which is equivalent to the normal range of the chest in pediatric patients. A good linear correlation (r = 0.933,N = 92) was obtained when the change in transmitted radiation was compared with tidal volume measured in a rabbit model using a pneumotachometer. The results indicate that the method is applicable for quantitative measurements of pulmonary ventilation. Changes in tidal ventilation can be measured with this noninvasive x-ray imaging technique.

Animals

Recent experience with a respiratory monitoring system in intensive care.

Computer based instrumentation for continuous monitoring of airway flow, pressure, O2 and CO2 concentration offers an improved noninvasive management technique for patients on mechanical ventilators. Computation of these basic signals provides routinely the following measurements: respiratory rate, tidal volume in and out, minute ventilation, positive end-expiratory pressure, mean airway pressure, inspiration-expiration ra measurements, except for O2 consumption and partially for tco2 production. The system works as a monitor of the respirator (detection of malfunction) and as a monitor of the lung function of the patient. It is particularly useful when adjusting the respirator and at time of weaning a patient from the respirator. These maneuvers can be made more safely because they are based on objective measurements and followed by immediate new sets of data. Defining the optimal values of tidal volume and positive end-expiratory pressure has been simplified by the use of pressure-volume plots. A "fighting", is now used as a measure of the severity of "fighting", that is of the effort of the patient to breathe spontaneously while being ventilated. It can detect fighting before it is diagnosed clinically and so can provide a warning that significant physiological changes will occur unless the fighting is controlled. New information about the distribution of ventilation-perfusion ratio can be derived from the expired concentration curve for CO2. Quantitative measurement of the distribution of ventilation shows a very close correlation with clinical events and can be carried out automatically during the normal routine of care of the patient. These on-line quantitative measurements, with the immediate reporting of results, appear to make a positive contribution to patient care.

Belgium

Utilization of pressure-volume curves in the pediatric patient.

Seven patients treated with continuous mechanical ventialtion were monitored with static and dynamic pressure-volume curves. Three patients developed no pulmonary complications, and mechanical ventilation was discontinued within 96 hr. In four patients, pressure-volume curves were used as a diagnostic aid in the detection of the physiologic defect resulting from bronchoconstriction, atelectasis, loculated pleural fluid, pulmonary edema, and mucous plugging. These measurements were also utilized to evaluate the effectivess of therapeutic modalities such as treatment of bronchoconstriction with bronchodilators, mucous plugging with adequate suctioning, and drainage of loculated pleural effusion. Pressure-v-lume measurements are simple, noninvasive, and require the smae equipment used in continuous mechanical ventilation. Pressure-volume monitoring of pediatric patients with curves warrants further investigation to evaluate its value.

Adolescent

Regional lung function studies and radionuclide angiography in D-transposition of the great arteries.

Thirty-nine ventilation and perfusion lung studies with xenon 313 were perfomed in 29 patients with D-transposition of the great arteries (DTGA). Fifteen patients had simple DTGA and 14 more complex anatomic features. Inequalitiies of ventilation (V) were present in 23% (9/39) and perfusion (Q) in 44% (17/39) of studies. Six patients with simple DTGA showed abnormal distribution of perfusion, all with increased flow to the right lung. Among the 14 patients with complex DTGA, eight (57%) had abnormal distribution of perfusion. In patients with pulmonary artery band, increased flow was directed toward the left lung, and in those with an aorticopulmonary anastomosis, increased flow was to the side of the shunt. Radionuclide angiograms were performed in 17 patients with DTGA, both before and after surgical repair. In all, an abnormal circulatory pattern was noted. Complete superior vena cava obstruction present in four patients and residual left to right shunt (Qp/qs greater than 1.7/liter) in three was confirmed at cardiac catheterization. Ventilation perfusion studies with xenon-313 and technetium-99m radionuclide angiogram were effective noninvasive techniques in assessing pulmonary function and hemodynamics in patients with DTGA.

Adolescent