Myofunctional training with negative airway pressure for obstructive sleep apnea: a prospective non-randomized cohort feasibility study

Background: Orofacial myofunctional therapy (OMT), for obstructive sleep apnea (OSA) is emerging with recognition of specific phenotypes. Since many OSA sufferers are already familiar with positive airway pressure machines, we designed an OMT protocol involving the modification of such a machine to deliver negative airway pressure. We hypothesized that a three-month trial of using this protocol while awake would reduce the signs and symptoms of OSA. Methods: Fifteen adults with OSA enrolled for 30-minute sessions/three days a week for a three-month trial of “upper airway muscle physical therapy” while awake. Overnight sleep studies were performed before and after the intervention to determine each subject’s apnea hypopnea index (AHI), the primary outcome measure. Negative airway pressure application was determined by estimation of each subject’s one-repetition maximum (an exercise physiology measure of strength capacity). Exercise sessions consisted of subjects breathing against this pressure for a series of repetitions, and sets. Results: While the mean post study AHI was slightly improved (-4.3 ± 12.0 [ -10.9, 2.3], mean ± standard deviation, 95% confidence interval), it was not statistically significant. The results were similar when the AHI was divided by the sleep state (REM vs. non-REM). The nadir saturation was also essentially unchanged. The eight subjects with mild or moderate OSA (AHI < 30) showed similar results. Conclusions: Though there was no significant reduction in AHI in this small cohort, the methods elucidate a new daytime use for a machine with which many OSA sufferers are familiar. Trial registration: ClinicalTrials.gov NCT02109731 (registered on April 10th 2015)

Effects of mechanical ventilation with expiratory negative airway pressure on porcine pulmonary and systemic circulation: mechano-physiology and potential application

We studied the impact of mechanically regulated, expiratory negative airway pressure (ENAP) ventilation on pulmonary and systemic circulation including its mechanisms and potential applications. Microminipigs weighing about 10 kg were anesthetized (n = 5). First, hemodynamic variables were evaluated without and with ENAP to approximately −16 cmH2O. ENAP significantly increased heart rate and cardiac output, but decreased right atrial, pulmonary arterial and pulmonary capillary wedge pressures. Second, the evaluation was repeated following pharmacological adrenergic blockade, modestly blunting ENAP effects. Third, fluvoxamine (10 mg/kg) was intravenously administered to intentionally induce cardiovascular collapse in the presence of adrenergic blockade. ENAP was started when systolic pressure was < 40 mmHg in the animals assigned to ENAP treatment-group. Fluvoxamine induced cardiovascular collapse within 4 out of 5 animals. ENAP increased systolic pressure to > 50 mmHg (n = 2): both animals fully recovered without neurological deficit, whereas without ENAP both animals died of cardiac arrest (n = 2). ENAP may become an innovative treatment for drug-induced cardiovascular collapse.

Aerosolized Particle Reduction: A Novel Cadaveric Model and a Negative Airway Pressure Respirator (NAPR) System to Protect Health Care Workers From COVID-19

Objectives This study aimed to identify escape of small-particle aerosols from a variety of masks using simulated breathing conditions. This study also aimed to evaluate the efficacy of a negative-pressure environment around the face in preventing the escape of small aerosolized particles. Study Design This study is an evaluation study with specific methodology described below. Setting This study was performed in our institution’s fresh tissue laboratory. Subjects and Methods A fixed cadaver head was placed in a controlled environment with a black background, and small-particle aerosols were created using joss incense sticks (mass-median aerosol diameter of 0.28 µ). Smoke was passed through the cadaver head, and images were taken with a high-resolution camera in a standardized manner. Digital image processing was used to calculate relative amounts of small-particle escape from a variety of masks, including a standard surgical mask, a modified Ambu mask, and our negative airway pressure respirator (NAPR). Results Significant amounts of aerosolized particles escaped during the trials with no mask, a standard surgical mask, and the NAPR without suction. When suction was applied to the NAPR, creating a negative-pressure system, no particle escape was noted. Conclusion We present a new and effective method for the study of small-particle aerosols as a step toward better understanding the spread of these particles and the transmission of coronavirus disease 2019. We also present the concept of an NAPR to better protect health care workers from aerosols generated from the upper and lower airways.

Inspiratory muscle activation via ventral lower thoracic high-frequency spinal cord stimulation

In animals, high-frequency spinal cord stimulation (HF-SCS) applied on the ventral epidural surface at the T2 level results in negative airway pressure generation consistent with inspiratory muscle activation. In the present study, in anesthetized dogs, we found that ventral HF-SCS (500 Hz) applied at all thoracic levels resulted in negative airway pressure generation. In the region of the lower thoracic spinal cord, negative airway pressure generation was most pronounced at the T9 level. At this level, airway pressure generation was monitored: 1) during ventral HF-SCS over a wide range of stimulus amplitudes (0.5–15 mA) and frequencies (50–1,000 Hz) and 2) following spinal sections at C8 (to assess potential diaphragm activation) and subsequently at T6 (to assess potential intercostal muscle activation). The application of low stimulus currents between 1 and 2 mA and high stimulus frequencies (>300 Hz) resulted in the development of large negative airway pressure generation. Stimulation with 1 mA, 500 Hz resulted in a highest negative airway pressure generation of 47 ± 2 cmH2O. Increasing stimulus current was associated with progressive reductions in the magnitude of negative airway pressure generation. HF-SCS (500 Hz) with 15 mA resulted in a negative airway pressure generation of 7 ± 3 cmH2O. C8 section markedly reduced negative airway pressure generation, and subsequent T6 section resulted in positive airway pressure generation after HF-SCS. Our results indicate the existence of pathways with connections to both the phrenic and inspiratory intercostal motoneuron pools in the ventral part of the lower thoracic spinal cord. We speculate that the circuits mediating the previously described excitatory intercostal-to-phrenic reflex mediate the observed responses. NEW & NOTEWORTHY This study suggests that, in contrast to dorsal high-frequency spinal cord stimulation at the T9 spinal level, which results in positive pressure generation, ventral high-frequency spinal cord stimulation at the same spinal level results in large negative airway pressure generation with low stimulus currents. This method, therefore, may provide an alternative method to restore ventilation in ventilator-dependent spinal cord-injured patients.

Continuous negative airway pressure “CNAP”: Novel nasal foreign body removal

<p class="abstract"><span lang="EN-IN">We report on a novel and innovative method used to extricate nasal foreign bodies in infants and young children– a common presentation in pediatric emergency care that can at times have potentially serious consequences. In the case of a three-year-old girl, ‘continuous negative airway pressure (CNAP)’ using a continuous positive airway pressure (CPAP) mask and a domestic vacuum cleaner, a nasal foreign body was removed quickly and effectively in a simple and painless procedure. While more cases are needed to confirm safety and efficacy, the principles underlying this technique could have great potential for future clinical use due to its simplicity and accessibility, particularly when compared to other techniques currently used in the home and in the emergency department.</span></p>