Respiratory Care Management of COPD Exacerbations

A COPD exacerbation is characterized by an increase in symptoms such as dyspnea, cough, and sputum production that worsens over a period of 2 weeks. Exacerbations are common. Respiratory therapists and physicians in an acute care setting often treat these patients. Targeted O₂ therapy improves outcomes and should be titrated to an S_pO2 of 88-92%. Arterial blood gases remain the standard approach to assessing gas exchange in patients with COPD exacerbation. The limitations of arterial blood gas surrogates (pulse oximetry, capnography, transcutaneous monitoring, peripheral venous blood gases) should be appreciated so that they can be used wisely. Inhaled short-acting bronchodilators can be provided by nebulizer (jet or mesh), pressurized metered-dose inhaler (pMDI), pMDI with spacer or valved holding chamber, soft mist inhaler, or dry powder inhaler. The available evidence for the use of heliox for COPD exacerbation is weak. Noninvasive ventilation (NIV) is standard therapy for patients who present with COPD exacerbation and is supported by clinical practice guidelines. Robust high-level evidence with patient important outcomes is lacking for the use of high-flow nasal cannula in patients with COPD exacerbation. Management of auto-PEEP is the priority in mechanically ventilated patients with COPD. This is achieved by reducing airway resistance and decreasing minute ventilation. Trigger asynchrony and cycle asynchrony are addressed to improve patient-ventilator interaction. Patients with COPD should be extubated to NIV. Additional high-level evidence is needed before widespread use of extracorporeal CO₂ removal. Care coordination can improve the effectiveness of care for patients with COPD exacerbation. Evidence-based practices improve outcomes in patients with COPD exacerbation.

How I Teach Auto-PEEP: Applying the Physiology of Expiration

Teaching complex topics in mechanical ventilation can prove challenging for clinical educators, both at the bedside and in the classroom setting. Some of these topics, such as the topic of auto-positive end-expiratory pressure (auto-PEEP), consist of complicated physiological principles that can be difficult to convey in an organized and intuitive manner. In this entry of "How I Teach," we provide an approach to teaching the concept of auto-PEEP to senior residents and fellows working in the intensive care unit. We offer a framework for educators to effectively present the concepts of auto-PEEP to learners, either at the bedside or in the classroom setting, by summarizing key concepts and including concrete examples of the educational techniques we use. This framework includes specific content we emphasize, how to present this content using a variety of educational resources, assessing learner understanding, and how to modify the topic on the basis of location, time, or resource constraints.

Pediatric Simulation of Intrinsic PEEP and Patient-Ventilator Trigger Asynchrony During Mechanical Ventilation

BACKGROUND

Intrinsic PEEP during mechanical ventilation occurs when there is insufficient time for expiration to functional residual capacity before the next inspiration, resulting in air trapping. Increased expiratory resistance (R_E), too rapid of a patient or ventilator breathing rate, or a longer inspiratory to expiratory time ratio (T_I/T_E) can all be causes of intrinsic PEEP. Intrinsic PEEP can result in increased work of breathing and patient-ventilator asynchrony (PVA) during patient-triggered breaths. We hypothesized that the difference between intrinsic PEEP and ventilator PEEP acts as an inspiratory load resulting in trigger asynchrony that needs to be overcome by increased respiratory muscle pressure (P_mus).

METHODS

Using a Servo lung model (ASL 5000) and LTV 1200 ventilator in pressure control mode, we developed a passive model demonstrating how elevated R_E increases intrinsic PEEP above ventilator PEEP. We also developed an active model investigating the effects of R_E and intrinsic PEEP on trigger asynchrony (expressed as percentage of patient-initiated breaths that failed to trigger). We then studied if trigger asynchrony could be reduced by increased P_mus.

RESULTS

Intrinsic PEEP increased significantly with increasing R_E (r = 0.97, P = .006). Multivariate logistic regression analysis showed that both R_E and negative P_mus levels affect trigger asynchrony (P < .001).

CONCLUSIONS

A passive lung model describes the development of increasing intrinsic PEEP with increasing R_E at a given ventilator breathing rate. An active lung model shows how this can lead to trigger asynchrony since the P_mus needed to trigger a breath is greater with increased R_E, as the inspiratory muscles must overcome intrinsic PEEP. This model will lend itself to the study of intrinsic PEEP engendered by a higher ventilator breathing rate, as well as higher T_I/T_E, and will be useful in ventilator simulation scenarios of PVA. The model also suggests that increasing ventilator PEEP to match intrinsic PEEP can improve trigger asynchrony through a reduction in R_E.

Usefulness of P0.1 in the Follow-Up of Individuals With Air Trapping and Home Noninvasive Ventilation and CPAP

BACKGROUND

The ventilatory mechanics of patients with COPD and obesity-hypoventilation syndrome (OHS) are changed when there is air trapping and auto-PEEP, which increase respiratory effort. P0.1 measures the ventilatory drive and, indirectly, respiratory effort. The aim of the study was to measure P0.1 in subjects with COPD or OHS on treatment with positive pressure and to analyze their changes in P0.1 after treatment.

METHODS

With a prospective design, subjects with COPD and OHS were studied in whom positive airway pressure was applied in their treatment. P0.1 was determined at study inclusion and after 6 months of treatment.

RESULTS

A total of 88 subjects were analyzed: 56% were males, and the mean age of 65 ± 9 y old. Fifty-four (61%) had OHS, and 34 (39%) had COPD. Fifty (56%) had air trapping, with an initial P0.1 value of 3.0 ± 1.3 cm H2O compared with 2.1 ± 0.7 cm H2O for subjects who did not have air trapping (P = .001). After 6 months of treatment, subjects who had air trapping had similar P0.1 as those who did not: 2.3 ± 1.1 and 2.1 ± 1 cm H2O, respectively (P = .53). In subjects with COPD, initial P0.1 was 2.9 ± 1.4 cm H2O and at 6 months 2.2 ± 1.1 cm H2O (P = .02). In subjects with OHS, initial P0.1 was 2.4 ± 1.1 cm H2O and at 6 months 2.2 ± 1.0 cm H2O (P = .28).

CONCLUSIONS

COPD and air trapping were associated with greater P0.1 as a marker of respiratory effort. A decrease in P0.1 indicates less respiratory effort after treatment.

Neonates With Tracheomalacia Generate Auto-Positive End-Expiratory Pressure via Glottis Closure

BACKGROUND

In pediatrics, tracheomalacia is an airway condition that causes tracheal lumen collapse during breathing and may lead to the patient requiring respiratory support. Adult patients can narrow their glottis to self-generate positive end-expiratory pressure (PEEP) to raise the pressure in the trachea and prevent collapse. However, auto-PEEP has not been studied in newborns with tracheomalacia. The objective of this study was to measure the glottis cross-sectional area throughout the breathing cycle and to quantify total pressure difference through the glottis in patients with and without tracheomalacia.

RESEARCH QUESTION

Do neonates with tracheomalacia narrow their glottises? How does the glottis narrowing affect the total pressure along the airway?

STUDY DESIGN AND METHODS

Ultrashort echo time MRI was performed in 21 neonatal ICU patients (11 with tracheomalacia, 10 without tracheomalacia). MRI scans were reconstructed at four different phases of breathing. All patients were breathing room air or using noninvasive respiratory support at the time of MRI. Computational fluid dynamics simulations were performed on patient-specific virtual airway models with airway anatomic features and motion derived via MRI to quantify the total pressure difference through the glottis and trachea.

RESULTS

The mean glottis cross-sectional area at peak expiration in the patients with tracheomalacia was less than half that in patients without tracheomalacia (4.0 ± 1.1 mm2 vs 10.3 ± 4.4 mm2; P = .002). The mean total pressure difference through the glottis at peak expiration was more than 10 times higher in patients with tracheomalacia compared with patients without tracheomalacia (2.88 ± 2.29 cm H2O vs 0.26 ± 0.16 cm H2O; P = .005).

INTERPRETATION

Neonates with tracheomalacia narrow their glottises, which raises pressure in the trachea during expiration, thereby acting as auto-PEEP.

The Degradation of Airway Epithelial Tight Junctions in Asthma Under High Airway Pressure Is Probably Mediated by Piezo-1

Full functioning of the airway physical barrier depends on cellular integrity, which is coordinated by a series of tight junction (TJ) proteins. Due to airway spasm, edema, and mucus obstruction, positive end-expiratory alveolar pressure (also termed auto-PEEP) is a common pathophysiological phenomenon, especially in acute asthma attack. However, the influence of auto-PEEP on small airway epithelial TJs is currently unclear. We performed studies to investigate the effect of extra pressure on small airway epithelial TJs and its mechanism. The results first confirmed that a novel mechanosensitive receptor, piezo-1, was highly expressed in the airway epithelium of asthmatic mice. Extra pressure induced the degradation of occludin, ZO-1 and claudin-18 in primary human small airway epithelial cells (HSAECs), resulting in a decrease in transepithelial electrical resistance (TER) and an increase in cell layer permeability. Through in vitro investigations, we observed that exogenous pressure stimulation could elevate the intracellular calcium concentration ([Ca²⁺]_i) in HSAECs. Downregulation of piezo-1 with siRNA and pretreatment with BAPTA-AM or ALLN reduced the degradation of TJs and attenuated the impairment of TJ function induced by exogenous pressure. These findings indicate the critical role of piezo-1/[Ca²⁺]_i/calpain signaling in the regulation of small airway TJs under extra pressure stimulation.

Just-In-Time Tools for Training Non-Critical Care Providers. Troubleshooting Problems in the Ventilated Patient

Due to the limited number of critical care providers in the United States, even well-staffed hospitals are at risk of exhausting both physical and human resources during the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One potential response to this problem is redeployment of non–critical care providers to increase the supply of available clinicians. To support efforts to increase capacity as part of surge preparation for the coronavirus disease (COVID-19) outbreak, we created an online educational resource for non-intensivist providers to learn basic critical care content. Among those materials, we created a series of one-page learning guides for the management of common problems encountered in the intensive care unit (ICU). These guides were meant to be used as just-in-time tools to guide problem-solving during the provision of ICU care. This article presents five guides related to managing complications that can arise in patients receiving invasive mechanical ventilation.

Synchronized abdominal compression as a novel treatment of life-threatening preschool asthma

Introduction: In severe asthma, management of life-threatening air trapping that persists despite initiation of standard asthma treatment is difficult in the absence of extracorporeal membranous oxygenation.Case study: Three children with life-threatening asthma could not be adequately ventilated despite maximum conventional treatment because of severe air trapping. A novel method of active expiration by abdominal compression with a standard ventilator was adopted with immediate effect with significant improvement in ventilation.Conclusion: Synchronized abdominal compression is a novel and simple method that allows an effective treatment of severe air trapping in an intubated paralyzed asthma child.

Application of mid-frequency ventilation in an animal model of lung injury: a pilot study

BACKGROUND

Mid-frequency ventilation (MFV) is a mode of pressure control ventilation based on an optimal targeting scheme that maximizes alveolar ventilation and minimizes tidal volume (VT). This study was designed to compare the effects of conventional mechanical ventilation using a lung-protective strategy with MFV in a porcine model of lung injury. Our hypothesis was that MFV can maximize ventilation at higher frequencies without adverse consequences. We compared ventilation and hemodynamic outcomes between conventional ventilation and MFV.

METHODS

This was a prospective study of 6 live Yorkshire pigs (10 ± 0.5 kg). The animals were subjected to lung injury induced by saline lavage and injurious conventional mechanical ventilation. Baseline conventional pressure control continuous mandatory ventilation was applied with V(T) = 6 mL/kg and PEEP determined using a decremental PEEP trial. A manual decision support algorithm was used to implement MFV using the same conventional ventilator. We measured P(aCO2), P(aO2), end-tidal carbon dioxide, cardiac output, arterial and venous blood oxygen saturation, pulmonary and systemic vascular pressures, and lactic acid.

RESULTS

The MFV algorithm produced the same minute ventilation as conventional ventilation but with lower V(T) (-1 ± 0.7 mL/kg) and higher frequency (32.1 ± 6.8 vs 55.7 ± 15.8 breaths/min, P < .002). There were no differences between conventional ventilation and MFV for mean airway pressures (16.1 ± 1.3 vs 16.4 ± 2 cm H2O, P = .75) even when auto-PEEP was higher (0.6 ± 0.9 vs 2.4 ± 1.1 cm H2O, P = .02). There were no significant differences in any hemodynamic measurements, although heart rate was higher during MFV.

CONCLUSIONS

In this pilot study, we demonstrate that MFV allows the use of higher breathing frequencies and lower V(T) than conventional ventilation to maximize alveolar ventilation. We describe the ventilatory or hemodynamic effects of MFV. We also demonstrate that the application of a decision support algorithm to manage MFV is feasible.