Resp Care
-
The beneficial effects of ambulatory home oxygen have been demonstrated since the 1950s, when Cotes and Gibson gave oxygen to ambulatory COPD patients from small portable high pressures cylinders in the United Kingdom. Over the ensuing 7 decades, oxygen has been prescribed to millions of COPD patients in the home setting. Additionally, it is common clinical practice to prescribe supplemental oxygen when chronic hypoxemic respiratory failure not due to COPD (eg, interstitial lung disease, pulmonary hypertension, kyphoscoliosis, and cystic fibrosis) is present or in patients with hypoxemia at hospital discharge following flares of their underlying chronic respiratory disorder, without any substantial evidence. ⋯ Research conducted in the 1970s and 1980s still provides the basis for clinical decision making and insurance coverage policies regarding long-term oxygen administration. Remarkably, little current research is being conducted to extend our knowledge regarding the indications, mechanisms, and benefits of long-term oxygen therapy. This review will focus on our current knowledge of the end points for supplemental oxygen at home, such as mortality, effects on functional performance, sensation of dyspnea, cognitive function, and quality of life, and highlight areas where future research is needed.
-
The nasal cannula has been a commonly used patient interface to provide supplemental oxygen since its introduction in the 1940s. Traditionally, it has been categorized as a low-flow device and capable of delivering a 0.4 F(IO(2)) with flows up to 6 L/min to adults with normal minute ventilation. However, there is considerable performance variability among patients and design, which results in an exponential decline in delivered F(IO(2)) as breathing frequencies increase. ⋯ HFNC therapy has also been considered valuable in perinatal care in treating the respiratory distress syndrome or supporting patients after extubation similar to nasal CPAP. At present, research-based evidence for the role of HFNC for its perinatal applications remains unclear. This review will identify proposed mechanisms for therapeutic effectiveness, current delivery equipment, guidelines for rational patient application, and direction for further research.
-
Prolonged breathing of very high F(IO(2)) (F(IO(2)) ≥ 0.9) uniformly causes severe hyperoxic acute lung injury (HALI) and, without a reduction of F(IO(2)), is usually fatal. The severity of HALI is directly proportional to P(O(2)) (particularly above 450 mm Hg, or an F(IO(2)) of 0.6) and exposure duration. Hyperoxia produces extraordinary amounts of reactive O(2) species that overwhelms natural anti-oxidant defenses and destroys cellular structures through several pathways. ⋯ During the 1960s, confusion regarding the incidence and relevance of HALI largely reflected such issues as the primitive control of F(IO(2)), the absence of PEEP, and the fact that at the time both ALI and ventilator-induced lung injury were unknown. The advent of PEEP and precise control over F(IO(2)), as well as lung-protective ventilation, and other adjunctive therapies for severe hypoxemia, has greatly reduced the risk of HALI for the vast majority of patients requiring mechanical ventilation in the 21st century. However, a subset of patients with very severe ARDS requiring hyperoxic therapy is at substantial risk for developing HALI, therefore justifying the use of such adjunctive therapies.
-
Strategies to support oxygenation can cause substantial harm through lung stretch injury, oxygen toxicity, transfusion risks and cardiac over-stimulation. Traditional goals of maintaining near normal cardiorespiratory parameters are most likely overly simplistic and are insensitive and nonspecific for tissue hypoxic effects. ⋯ We also need to learn better ways of monitoring tissue oxygenation, especially in "mission critical" tissues. Ultimately clinical trials will be needed to determine appropriate oxygenation targets to allow permissive hypoxemia.
-
The management of patients with traumatic brain injury has evolved in the last several years, due to the introduction of new, invasive monitoring devices. The ability to monitor parameters other than measurements related to pressures has generated substantial interest. Brain tissue oxygenation monitoring has been consistently shown to provide prognostic information, as indicated by poor prognosis associated with low brain tissue oxygen values. ⋯ Retrospective studies suggest benefit, while prospective studies have shown a higher intensity of therapeutic interventions with no outcome differences. Data from high quality randomized trials are necessary to determine if brain-oxygenation-guided therapy is beneficial. An oxygen challenge (transient increase in F(IO(2)) to 0.6 up to 1.0) to assess the responsiveness of the monitoring and ascertain the presence of technical malfunction is an accepted practice.