Respiratory Care Clinics of North America 

About: Respiratory Care Clinics of North America is an academic journal. The journal publishes majorly in the area(s): Mechanical ventilation & Lung injury. It has an ISSN identifier of 1078-5337. Over the lifetime, 339 publications have been published receiving 4176 citations.

Hyperbaric oxygen in the treatment of life-threatening soft-tissue infections.

Abstract: Necrotizing soft-tissue infections are rapidly spreading bacterial infections that account for a relatively small proportion of infections, but are aggressive in nature and nearly uniformly fatal if left untreated. Prompt recognition, antibiotic therapy, aggressive surgical debridement, and hyperbaric oxygen (HBO) therapy have reduced the mortality resulting from these infections. Oxygen, at increased pressures, augments tissue oxygen partial pressure, allowing increased bacterial killing by providing substrate for the formation of oxygen free radicals and augmenting respiratory burst. During the healing process, hyperoxia causes increased formation of capillaries for oxygen, nutrient, and antibiotic delivery, leading to increased efficacy of some antibiotics in the high oxygen environment, and possibly more rapid overall wound healing. Although there are no randomized trials of HBO in these infections, in vitro data and meta-analysis of clinical cases strongly support the use of HBO.

Neurophysiology of sleep and wakefulness

Abstract: Wakefulness, NREM sleep, and REM sleep are three distinct states of existence. Each state has characteristic behavioral and physiologic patterns,and each has specific neurophysiologic mechanisms associated with its generation and control. Structures in the brainstem use various neurotransmitters to influence higher brain structures in the midbrain and cortex. The ARAS provides cholinergic, noradrenergic, and glutaminergic stimulation to the thalamus, hypothalamus, and basal forebrain resulting in cholinergic and glutaminergic excitation of the cortex. An active cortex that exhibits a characteristic pattern of desynchronized EEG manifests wakefulness. Various factors affect the need and timing of sleep onset. These factors influence the nucleus tractus solitarius, causing its noradrenergic projections to midbrain and forebrain structures to inhibit activity in the ARAS, resulting inactivation of inhibitory GABAergic thalamocortical projections to the cor-tex. During a state of decreased activation, the cortex exhibits a pattern of synchronized EEG. Transition between NREM sleep and REM sleep is controlled by noradrenergic neurons in the loci coeruleus and serotoninergic neurons in the raphe called REM-off cells and cholinergic neurons in the nucleus reticularis pontis oralis called REM-on cells. Other brain structures are involved in generation and control of REM sleep-related phenomena, such as eye movement and muscle atonia. During wakefulness, there is increased sympathetic tone and decreased parasympathetic tone that maintains most organ systems in a state of action or readiness. During NREM sleep, there is decreased sympathetic tone and increased parasympathetic activity that creates a state of reduced activity. REM sleep is characterized by increased parasympathetic activity and variable sympathetic activity associated with increased activation of certain brain functions. The states of wakefulness and sleep are characterized as stages that are defined by stereotypical EEG, EMG, and EOG patterns. Wakefulness stage has an EEG pattern predominated by the alpha rhythm. With onset of stage 1 sleep, the alpha rhythm attenuates, and an EEG pattern of relatively low voltage and mixed frequency is seen. Progression to stage 2 sleep is defined by the appearance of sleep spindles or K-complexes. Further progression into the deepest sleep stages 3 and 4 is defined by the occurrence of high-amplitude, low-frequency EEG activity. The progression of sleep stages occurs in cycles of 60 to 120 minutes throughout the sleep period. Various circadian environmental and ontologic factors affect the pattern of sleep stage occurrence.

Tissue diagnosis of suspected lung cancer: selecting between bronchoscopy, transthoracic needle aspiration, and resectional biopsy.

Abstract: In pursuing a tissue diagnosis of a suspected lung cancer, there is a range of procedures to choose from. The principal goals are ideally to diagnose and pathologically stage the patient's lung cancer at the same time, preferably by using the safest, least invasive, and least costly tests. If there is clinical or radiographic evidence of extrapulmonary spread of disease, including supraclavicular N3 nodal involvement or a malignant pleural effusion, then radiology-guided or open biopsy will confirm tumor cell type and stage the patient as unresectable. For patients with symptoms, such as increasing cough or hemoptysis, that are suggestive of airways involvement. with or without radiographic finding of central lesions, sputum cytology is the least invasive study with a high specificity. A positive finding of cancer is especially helpful if the patient is not a surgical candidate because of anatomic location of the lesion or severe physiologic limitations. The limited sensitivity of sputum cytology and poor NPV may improve with improved sputum induction and collection and processing techniques. Bronchoscopy with direct examination of the visible airways is most often the preferred invasive diagnostic procedure. Although the procedure should be geared toward sampling the highest staged lesion to provide an accurate tissue staging at the time of diagnosis, additional procedures can be performed in sequence to sample different nodal stations, is well as the primary lung mass. The incidental finding of an unexpected central airways lesions or a synchronous second endobronchial lung primary will also affect plans for treatment. Autofluorescence bronchoscopy can improve the sensitivity for detecting early intraepithelial neoplasia. Bronchoscopy for central and peripheral lung masses that are suspected to be lung cancer should be performed with ROSE whenever available. For visible endobronchial lesions, given the similar yield of EBBX and EBNA, EBNA may provide an immediate diagnosis, thus obviating additional, possibly morbid, procedures such as BB or EBBX. For submucosal lesions, EBNA is superior. For central cancers that are peribronchial, TBNA performed as for regional nodal sampling should have a yield that is comparable to TBNA for staging. TBBX and TBNA of peripheral nodules that are smaller than 3 cm have a lower diagnostic yield. Coming generations of thin bronchoscopes and improved radiographic guidance systems may improve our ability to biopsy these lesions with greater accuracy and safety. Under all circumstances, immediate cytology feedback with ROSE will confirm the adequacy of the retrieved specimen for a definitive tissue diagnosis, thus avoiding the need for extra biopsies, or worse yet, the need for a second invasive procedure because of insufficient diagnostic material. ROSE is educational to the clinician and fellow-in-training in getting immediate feedback on the procedural techniques and in learning pulmonary pathology, as well. The diagnostic sensitivity of TTNA is high, especially for the larger peripheral-based lung lesion, and TTNA is a relatively rapid procedure. TTNA's sensitivity falls for smaller or more central lesions, where the false negative rate can approach 25% to 30%; the risk of pneumothoraces and bleeding increases with central biopsies. Furthermore, TTNA usually does not provide information about nodal staging, unless the TTNA is initially directed toward central lymph nodes. The central airways are not examined in the same appointment to address issues of resection margins when there may be central spread of disease. TTNA should, therefore, be held in reserve for cases in which the sputum cytology and subsequent bronchoscopy are negative, and the patient is not a surgical candidate or refuses surgery, even if the cancer is potentially resectable. TTNA may then provide the tissue diagnosis to permit initiation of cytotoxic chemotherapy and radiotherapy. TTNA may also be helpful in cases where the likelihood of cancer is only intermediate, such that a specific benign diagnosis or an adequate sample without cancer will greatly reduce the likelihood ratio of missing a cancer, and justify to the patient and physician an approach of careful observation. To maximize the yield of these diagnostic procedures, there must be continued improvement in the hands-on teaching of clinical fellows and pulmonary practitioners in the use of the various techniques of TBNA and TBBX, as well as the applications of new endoscopic technology, such as EBUS. Definitive curative surgery remains the goal for patients with lung cancer, with accurate pathological staging performed intraoperatively. Complete lobectomy or pneumonectomy remains the standard resectional approach. Therefore, for patients with sufficient cardiopulmonary reserve who can be clinically staged as IA or IB, either by good quality CT with contrast or increasingly with 18-FDG PET, the initial tissue diagnosis may be at the time of surgery, when a frozen section preceding a complete lobectomy with lymph node sampling will combine diagnosis and therapy.

Adaptive support ventilation.

Abstract: Adaptive support ventilation (ASV) is a newer form of closed-loop ventilation control available on the Galileo ventilator (Hamilton Medical). ASV provides automated selection of initial ventilator parameters based on measurements of patient lung mechanics and breathing effort. After initiation, ASV will "titrate" ventilator output (mandatory breath rate, tidal volume, inspiratory pressure, inspiratory time, and I to E ratio) to maintain a calculated optimal breathing pattern that ensures delivery of a clinician selected minute ventilation target. ASV may be thought of as an "electronic" ventilator management protocol that may improve the safety and efficacy of mechanical ventilation. Additional clinical investigations regarding the effect of ASV on outcome, ventilator days, and so forth are forthcoming.

Consequences of under- and over-humidification.

Abstract: Respiratory mucosal and lung structures and functions may be severely impaired in mechanically ventilated patients when delivered gases are not adequately conditioned. Although under- and over-humidification of respiratory gases have not been defined clearly, a safe range of temperature and humidity may be suggested. During mechanical ventilation, gas entering the trachea should reach at least physiologic conditions (32 degrees C-34 degrees C and 100%relative humidity) to keep the ISB at its normal location. Clinicians must keep in mind that relative humidity is more important than absolute humidity: the warmer the gas, the higher the risk of tracheal mucosa dehydration and proximal airway obstruction. Practical assessment of the adequacy of the humidification system in use is not easy. The consistency (thin, moderate, or thick) of the patient's sputum should be evaluated regularly [47]. Full saturation of inspiratory gases is likely when water condensation is observed in the flex tube [91,92]. Nevertheless, no clinical parameter is accurate enough to detect all the effects of inadequate conditioning [45]. When mechanical ventilation is extended beyond several days, adequate conditioning of respiratory gases becomes increasingly crucial to prevent retention of secretions and to maximize mucociliary function; a requirement that respiratory gases reach at least physiologic conditions is appropriate.