Etiology and Management of Hypoventilation Syndromes

A number of diseases affecting central ventilation, breathing mechanics or both, characterize hypoventilation syndromes. The incidence of hypoventilation syndromes varies according to the underlying reason. The hypoventilation syndrome's clinical symptoms are generally vague and are in most cases due to the underlying clinical condition. More individuals develop hypercapnia and hypoxemia as hypoventilation continues to worsen. Therefore, clinical indications of hypoxemia such as cyanosis, and evidence of hypercapnia may also be present. Regardless of the etiology, successful hypoventilation therapy focuses on the underlying illness and noninvasive ventilation. Treatment for these diseases includes integrated main disorder treatment and, increasingly, non-invasive positive pressure breathing. In this paper, we overview current evidence regarding different etiologies and management of hypoventilation syndromes. Data was collected during the period of 6 months searching Pubmed, EPISCO, Web of science, Google scholar databases to include papers with relative topics.

Temporary Extrathoracic Vacuum Therapy Splint in Chest Wall Reconstruction

Background Paradoxical respiration is a sinister consequence of bony chest cage defects which can persist even post chest wall reconstruction. It leads to prolonged dependence on mechanical ventilation postoperatively, thereby delaying recovery. Methods Negative pressure wound therapy (NPWT) was applied in early postoperative period to a patient with chest wall defect reconstructed with folded prolene mesh and free anterolateral thigh flap. Arterial blood gas (ABG), fraction of inspired oxygen (FiO2), peak end expiratory pressure (PEEP), oxygen saturation (SpO2), and blood pressure (BP) readings pre and post NPWT application were compared. Results There was marked improvement in the breathing mechanics and related parameters post NPWT application over the flap. Conclusions Negative extrathoracic pressure in the form of a temporary splint can enable early weaning off the ventilator and a smoother postoperative recovery in reconstructed chest wall defects.

The influence of the post-pulmonary septum and submersion on the pulmonary mechanics of Trachemys scripta (Cryptodira: Emydidae)

The respiratory system of chelonians needs to function within a mostly solid carapace, with ventilation depending on movements of the flanks. When submerged, inspiration has to work against a hydrostatic pressure and we examined breathing mechanics in Trachemys scripta while underwater. Furthermore, the respiratory system of T. scripta possesses a well-developed post-pulmonary septum (PPS), and we investigated its role on breathing mechanics of lungs with and without their PPS attached. Static compliance was significantly increased in submerged animals and in animals with and without their PPS, while the removal of the PPS did not result in a significantly different static compliance. Dynamic compliance was significantly affected by changes in volume and frequency in every treatment, with submergence significantly decreasing dynamic compliance. The presence of the PPS significantly increased dynamic compliance. Submersion did not alter significantly work per ventilation, but caused minute work of breathing to be much greater at any frequency and ventilation level analyzed. Lungs with or without their PPS did not show significantly different work per ventilation when compared to intact animal. Our results demonstrate that submersion results in significantly altered breathing mechanics, increasing minute work of breathing greatly. The PPS was shown to maintain a constant volume within the animal's body cavity, wherein the lungs can be ventilated more easily, highlighting the importance of this coelomic subdivision in the chelonian body cavity.

Broad individual immersion-scattering of respiratory compliance likely substantiates dissimilar breathing mechanics

Head-out water immersion alters respiratory compliance which underpins defining pressure at a “Lung centroid” and the breathing “Static Lung Load”. In diving medicine as in designing dive-breathing devices a single value of lung centroid pressure is presumed as everyone’s standard. On the contrary, we considered that immersed respiratory compliance is disparate among a homogenous adult group (young, healthy, sporty). We wanted to substantiate this ample scattering for two reasons: (i) it may question the European standard used in designing dive-breathing devices; (ii) it may contribute to understand the diverse individual figures of immersed work of breathing. Resting spirometric measurements of lung volumes and the pressure–volume curve of the respiratory system were assessed for 18 subjects in two body positions (upright Up, and supine Sup). Measurements were taken in air (Air) and with subjects immersed up to the sternal notch (Imm). Compliance of the respiratory system (Crs) was calculated from pressure–volume curves for each condition. A median 60.45% reduction in Crs was recorded between Up-Air and Up-Imm (1.68 vs 0.66 L/kPa), with individual reductions ranging from 16.8 to 82.7%. We hypothesize that the previously disregarded scattering of immersion-reduced respiratory compliance might participate to substantial differences in immersed work of breathing.

Systolic Reserve Maintains Left Ventricular-Vascular Coupling When Challenged by Adverse Breathing Mechanics and Hypertension in Healthy Adults

Augmented negative intrathoracic pressures (nITP) and dynamic hyperinflation (DH) are adverse breathing mechanics (ABM) associated with chronic obstructive pulmonary disease that attenuate left ventricular (LV) preload and augment afterload. In COPD, hypertension (elevated systemic arterial load) commonly adds additional afterload to the LV. Combined ABM and hypertension may profoundly challenge ventricular-vascular coupling and attenuate stroke volume (SV), particularly if LV systolic reserve is limited. However, even in the healthy heart, the combined impact of ABM and systemic arterial loading on LV function and ventricular-vascular coupling has not been fully elucidated. Healthy volunteers (10M/9F, 24±3 years) were challenged with Mild (-10cmH2O nITP and 25% DH) and Severe (-20cmH2O nITP and 100% DH) ABM, without and with post-exercise ischemia (PEI) at each severity. LV SV, chamber geometry, and end-systolic elastance (Ees), arterial elastance (Ea), and ventricular-vascular coupling (Ees:Ea) were quantified using echocardiography. Compared to resting Control (58±13mL), SV decreased during Mild ABM (51±13mL), Mild ABM+PEI (51±11mL), Severe ABM (50±12mL), and Severe ABM+PEI (47±11mL) (P<0.001); similar trends were observed for LV end-diastolic volume. The end-diastolic radius of septal curvature increased, indicating direct ventricular interaction, during Severe ABM and Severe ABM+PEI (P<0.001). Compared to Control (1.99±0.41mmHg/mL), Ea increased progressively with Mild ABM (2.21±0.47mmHg/mL) and Severe ABM (2.50±0.56mmHg/mL); at each severity Ea was greater with superimposed PEI (P<0.001). However, well-matched Ees increases occurred, and Ees:Ea was unchanged throughout. ABM pose a challenge to ventricular-vascular coupling that is accentuated by superimposed PEI; however, in healthy younger adults, the LV has substantial systolic reserveto maintain coupling.

Circumventing surface tension: tadpoles suck bubbles to breathe air

The surface tension of water provides a thin, elastic membrane upon which many tiny animals are adapted to live and move. We show that it may be equally important to the minute animals living beneath it by examining air-breathing mechanics in five species (three families) of anuran (frog) tadpoles. Air-breathing is essential for survival and development in most tadpoles, yet we found that all tadpoles at small body sizes were unable to break through the water's surface to access air. Nevertheless, by 3 days post-hatch and only 3 mm body length, all began to breathe air and fill the lungs. High-speed macrovideography revealed that surface tension was circumvented by a novel behaviour we call ‘bubble-sucking’: mouth attachment to the water's undersurface, the surface drawn into the mouth by suction, a bubble ‘pinched off’ within the mouth, then compressed and forced into the lungs. Growing tadpoles transitioned to air-breathing via typical surface breaching. Salamander larvae and pulmonate snails were also discovered to ‘bubble-suck’, and two insects used other means of circumvention, suggesting that surface tension may have a broader impact on animal phenotypes than hitherto appreciated.