Oxygen-saturation targets and outcomes in extremely preterm infants

BACKGROUND

Physiological studies have shown that chronic hypoxemia may occur in preterm infants who require supplemental oxygen for extended periods and that this hypoxemia may contribute to poor growth and development. Anecdotal reports and uncontrolled observational studies have suggested that a higher oxygen-saturation range may be beneficial in terms of growth and development.

METHODS

We conducted a multicenter, double-blind, randomized, controlled trial involving 358 infants born at less than 30 weeks of gestation who remained dependent on supplemental oxygen at 32 weeks of postmenstrual age. They were randomly assigned to a target functional oxygen-saturation range of either 91 to 94 percent (standard-saturation group) or 95 to 98 percent (high-saturation group); this target was maintained for the duration of supplemental-oxygen therapy. The primary outcomes were growth and neurodevelopmental measures at a corrected age of 12 months.

RESULTS

There were no significant differences between the groups in weight, length, or head circumference at a corrected age of 12 months. The frequency of major developmental abnormalities also did not differ significantly between the standard-saturation group and the high-saturation group (24 percent and 23 percent, respectively, P=0.85). There were six deaths due to pulmonary causes in the high-saturation group and one such death in the standard-saturation group (P=0.12). The high-saturation group received oxygen for a longer period after randomization (median, 40 days vs. 18 days; P<0.001) and had a significantly higher rate of dependence on supplemental oxygen at 36 weeks of postmenstrual age and a significantly higher frequency of home-based oxygen therapy.

CONCLUSIONS

Targeting a higher oxygen-saturation range in extremely preterm infants who were dependent on supplemental oxygen conferred no significant benefit with respect to growth and development and resulted in an increased burden on health services.

The prescribing and follow-up of domiciliary oxygen--whose responsibility? A survey of prescribing from primary care

Domiciliary oxygen is expensive and is frequently used outside the prescribing guidelines, which include the need for blood oxygen measures, a hospital-based facility. Ongoing prescriptions are generally provided by general practitioners (GPs). A survey in the north-east of England found that the origin of the initial prescription was often obscure and that there was no record of the responsible clinician or of structured follow-up for the majority of patients. Many patients received oxygen outside the prescribing guidelines. There is a need for better organised, conjoint follow-up of patients on domiciliary oxygen.

[Reliability of Venturi oxygen therapy systems]

Venturi systems are among the most widely used devices for delivering oxygen therapy. Nevertheless, rigorous quality control of their reliability is lacking. In this study we used mass spectrometry to evaluate Venturi systems sold by various companies in Spain. We also studied tolerance under various conditions (changes in oxygen flow and with increased system resistance). Fixed systems were found to comply well with recommendations, whereas none of the variable systems complied. One system (Oxigem Variable) was unable to provide an oxygen concentration below 31% when set to deliver at 24% to 28%. We conclude that the variable masks available in Spain do not comply with European Union recommendations and the range of error of one of them (Oxigem Variable) means it is not clinically useful. Fixed systems were the most reliable ones in our market, and airlife and intersurgical devices were the variable systems that best approximated the reliability of fixed systems.

Has oxygen administration delayed appropriate respiratory care? Fallacies regarding oxygen therapy

Modern clinical use of supplemental oxygen supposes that: (1) exposure to F(IO)(2) < or = 60% is without adverse effects, (2) an individual at risk of developing arterial hypoxemia can be protected by administering high F(IO)(2), and (3) routine administration of supplemental oxygen is useful, harmless, and clinically indicated. There is now substantial evidence that none of those 3 suppositions are correct, and, on the contrary, supplemental oxygen is actually detrimental to many of the patients who receive it. Supplemental oxygen is much overused and its use should be limited to the few conditions and situations in which it is truly effective, useful, and non-detrimental.

[Standard indication of home oxygen therapy for terminal cancer patients]

Home oxygen therapy for terminal cancer patients is not suitable for present standard. As the result of the questionnaire answered by home care doctors, many of them agreed to reconsider the present standard. We propose the following revision, 1. Standard that highly regard clinical symptoms, 2. subdivision of the fee, 3. addition of home care fee.

Preoxygenation time versus decompression sickness incidence

Preoxygenation, breathing 100% oxygen prior to decompression, has been used for well over half of this century to reduce decompression sickness (DCS) incidence. Duration of preoxygenation has been reported to be inversely related to subsequent DCS incidence. A direct comparison of DCS incidence at 30,000 ft versus preoxygenation time is needed to allow better-informed decisions regarding the cost vs. benefit of increasing preoxygenation time to prevent DCS. To obtain such a comparison, we accomplished a retrospective study of exposures to 30,000 ft (226 mm Hg; 4.37 psia) while performing mild exercise. The 86 male exposures were preceded by preoxygenation times of one to four hours. Venous gas emboli (VGE) and DCS symptom development were monitored and recorded. Although more protection was demonstrated with increasing preoxygenation time, the cost-to-benefit ratio also increases with each additional increment of preoxygenation time. The diminishing return of increasing preoxygenation to reduce DCS would eventually impact mission planning and crew duty limitations. Alteration in the physiology of denitrogenation, such as inclusion of exercise during preoxygenation, may provide better and more cost-effective DCS protection than simply increasing preoxygenation time.

An audit of oxygen prescribing in acute general medical wards

Oxygen therapy is highly specialised and must be tailored to the individual. In an audit in one hospital, less than a fifth of the patients receiving this therapy had the prescription written in their medical notes. This problem could have possible legal implications and requires nurses to be vigilant in ensuring oxygen is properly prescribed and administered.

[CBO guideline 'Oxygen therapy at home']

In the Netherlands, domiciliary oxygen therapy is regularly prescribed incorrectly and thus inefficiently, and the policies surrounding this therapy are inconsistent. This applies particularly to patients with chronic hypoxaemia due to chronic obstructive pulmonary disease (COPD). In order to establish a scientific basis for a uniform prescription policy, guidelines have been developed under the auspices of the Dutch Thoracic Society with the support of the Dutch Institute for Health Care Improvement. Based on scientific research, recommendations have been formulated for the indications and aims of domiciliary oxygen therapy and long-term oxygen therapy (LTOT). The most important recommendations (summarised on the back of an oxygen application form) are: domiciliary oxygen therapy is only indicated for severe hypoxaemia by day at rest; if domiciliary oxygen therapy was prescribed following recovery from an acute exacerbation or hospitalisation, the arterial oxygen tension should be rechecked within three months of starting oxygen therapy; prescription of LTOT is only justified in case of an optimal (non-)medical regimen, clinical stability, and chronic hypoxaemia, and providing a number of preconditions, such as smoking cessation (partly due to the fire hazard), have been met; LTOT is a lifelong therapy that should be prescribed for at least 15, and preferably 24, hours per day, and the oxygen flow rate settings for rest, exertion and sleep should be adjusted to meet the patient's needs; for ambulatory patients, the prescribing physician should consider the portability of the oxygen equipment; as patient education and supervision are essential to secure the success of LTOT, the prescribing physician should cooperate with the general practitioner, the district nurse and the oxygen supplier in this respect.

Adaptive pressure support servo-ventilation: a novel treatment for Cheyne-Stokes respiration in heart failure

Adaptive servo-ventilation (ASV) is a novel method of ventilatory support designed for Cheyne-Stokes respiration (CSR) in heart failure. The aim of our study was to compare the effect of one night of ASV on sleep and breathing with the effect of other treatments. Fourteen subjects with stable cardiac failure and receiving optimal medical treatment were tested untreated and on four treatment nights in random order: nasal oxygen (2 L/min), continuous positive airway pressure (CPAP) (mean 9.25 cm H(2)O), bilevel (mean 13.5/5.2 cm H(2)O), or ASV largely at the default settings (mean pressure 7 to 9 cm H(2)O) during polysomnography. Thermistor apnea + hypopnea index (AHI) declined from 44.5 +/- 3.4/h (SEM) untreated to 28.2 +/- 3.4/h oxygen and 26.8 +/- 4.6/h CPAP (both p < 0.001 versus control), 14.8 +/- 2.3/h bilevel, and 6.3 +/- 0.9/h ASV (p < 0.001 versus bilevel). Effort band AHI behaved similarly. Arousal index decreased from 65.1 +/- 3.9/h untreated to 29.8 +/- 2.8/h oxygen and 29.9 +/- 3.2/h CPAP, to 16.0 +/- 1.3/h bilevel and 14.7 +/- 1.8/h ASV (p < 0.01 versus all except bilevel). There were large increases in slow-wave and rapid eye movement (REM) sleep with ASV but not with oxygen or CPAP. All subjects preferred ASV to CPAP. One night ASV suppresses central sleep apnea and/or CSR (CSA/CSR) in heart failure and improves sleep quality better than CPAP or 2 L/min oxygen.

[Monitoring domiciliary oxygen therapy from a district hospital]

OBJECTIVES

This study aimed a) to evaluate correct use of domiciliary oxygen therapy (DOT); b) to estimate the prevalence of DOT, and c) to evaluate DOT based on the same parameters after intervention by the monitoring team.

PATIENTS AND METHOD

Cross-sectional, prospective study of all patients receiving DOT before and after initiation of monitoring. We administered spirometric tests, analyzed indications for and compliance with DOT and monitored pulse oxymetry in order to adjust oxygen flow.

RESULTS

Seventy-six patients were receiving DOT (63/100,000 inhabitants). Among the 60 patients with COPD, half met ideal indications for prescribing DOT, 65% complied with over 15 h of DOT, and hypoxemia was not corrected for 26%. Monitoring resulted in withdrawal of DOT from 28 patients (reduction of 37%), and DOT was prescribed for 27 new patients, 11 of whom received liquid oxygen. At the end of the study, 46 patients were receiving DOT (38/100,000 inhabitants).

CONCLUSIONS

a) Ideal indications for DOT, adequate compliance and correction of hypoxemia were observed in 54% of the patients undergoing therapy; b) creation of a special service to care for patients receiving DOT improves monitoring, and c) the prevalence of DOT in our area has been reduced from 63 to 38/100,000 inhabitants.

Effects of continuous, expiratory, reverse, and bi-directional tracheal gas insufflation in conjunction with a flow relief valve on delivered tidal volume, total positive end-expiratory pressure, and carbon dioxide elimination: a bench study

INTRODUCTION

Tracheal gas insufflation (TGI) can increase total positive end-expiratory pressure (total-PEEP) when flow is delivered in a forward direction, necessitating adjustments to maintain total-PEEP constant. When TGI is delivered throughout the respiratory cycle, additional adjustments are needed to maintain tidal volume (V(T)) constant.

OBJECTIVE

Determine if bi-directional TGI (bi-TGI) (simultaneous flows toward the lungs and upper airway) in combination with a flow relief valve eliminates the increase in total-PEEP and maintains a constant V(T), thus simplifying TGI administration.

METHODS

Using an artificial lung model and pressure control ventilation, we studied the effect of TGI at 10 L/min on inspired V(T), total-PEEP, and CO(2) elimination during 6 conditions: (1) control (no TGI, no catheter in the airway), (2) baseline (catheter in the airway but no TGI), (3) continuous TGI, (4) expiratory TGI, (5) reverse TGI, and (6) bi-TGI. Each condition was studied under 3 inspiration-expiration ratios (1:1, 1:2, and 2:1). A preset flow relief valve was inserted into the ventilator circuit during all TGI conditions with continuous flow.

SETTING

University research laboratory.

RESULTS

CO(2) elimination efficiency was similar under all conditions. Total-PEEP increased with continuous TGI and expiratory TGI, decreased during reverse TGI, and was unchanged during bi-TGI. With the flow relief valve in place, and no adjustment in mechanical ventilation, the change in minute ventilation ranged from 0% to 10%, with the least change during bi-TGI (0-5%). During bi-TGI, gas flow was equivalent in both directions during dynamic conditions and the flow relief valve consistently removed gas at 10 L/min under various pressures.

CONCLUSIONS

Our data from an artificial lung model support that continuous bi-TGI minimizes the change in total-PEEP seen during other TGI modalities. The flow relief valve compensated for the extra gas volume delivered by the TGI catheter, thereby eliminating the need to make ventilator adjustments. Used in combination with a flow relief valve, bi-TGI appears to offer unique advantages by providing a simpler method to deliver TGI. Further testing is indicated to determine if similar benefits occur in the clinical setting.

Development and testing of formal protocols for oxygen prescribing

The absence of standardized assessment protocols with well- defined measurement properties limits comparison of outcomes among those receiving long-term oxygen therapy (LTOT). We describe simple protocols for a hospital test, a simulated home test, and an actual home test, their reliability and relationship to each other. Stable patients with exercise hypoxemia participated. In 74 patients who completed four exercise tests, correlations between tests ranged from 0.85 to 0.78. Of these 27.0% had the same prescription from all four tests. In 46% prescriptions were within 1 L/ min and in 27% within 2 L/min. During exercise the hospital tests suggested slightly higher oxygen prescriptions than did the simulated home tests (2.5 L/min versus 2.0 L/min, p < 0.001). In 23 patients who participated in actual home assessments, the correlations between the home test, the hospital, and the simulated home tests were 0.22 (95% CI -0.24 to 0.67) and 0.27 (95% CI -0.18 to 0.72). In conclusion, standardizing tests for the assessment of LTOT is important. We describe simple hospital and simulated home tests that are reproducible, easy to carry out, and correlate well with each other.

Assessment of a breathless patient

This article discusses a systematic approach to the assessment of a breathless patient and outlines the principles of oxygen delivery. The indications for oxygen administration, different methods of delivery and the nursing management of oxygen therapy are examined.

Reevaluation of continuous oxygen therapy after initial prescription in patients with chronic obstructive pulmonary disease

BACKGROUND

Long-term oxygen therapy improves survival and quality of life in hypoxemic patients with chronic obstructive pulmonary disease (COPD). The need for long-term oxygen therapy should be determined when patients are medically stable. The Third Oxygen Consensus Conference recommended reevaluating patients 1-3 months after continuous oxygen therapy (COT) is initiated, if initiated when the patient is medically unstable.

METHODS

A cross-sectional study was performed to examine how often orders for COT are reevaluated pursuant to the guidelines promulgated by the Third Oxygen Therapy Consensus Conference, and to assess the impact that following these guidelines would have on the cost of COT.

RESULTS

Of 226 patients prescribed home oxygen therapy, 92 had COPD as a primary diagnosis and 57 were prescribed COT. Only 19 (35%) of 55 patients who returned to the clinics were appropriately reevaluated. The rate of appropriate reevaluation was significantly higher among pulmonary physicians than among primary care physicians (65% vs 17%; odds ratio: 9.0; 95% confidence interval: 2.5-32). Of 19 patients who were appropriately reevaluated, 11 (58%) were discontinued from COT. The patients who were discontinued from COT had a significantly higher percent of predicted forced expiratory volume in the first second than those who were not (34 +/- 8.6% vs 25 +/- 8.8%; p = 0.04).

CONCLUSIONS

In our study, most patients were clinically unstable when COT was prescribed, and a significant number of patients remained on COT without reevaluation. Up to 60% of those patients could potentially be discontinued from COT if appropriately reevaluated. Referring a patient initiated on COT to a pulmonary specialist for the proper use of oxygen is strongly recommended. Reevaluating such patients in a timely fashion and discontinuing unnecessary oxygen concentrators could possibly save $106-153 million per year in the United States.

[Does the present medical care system satisfy patients with home oxygen therapy (HOT) and home therapy with assisted ventilation (HTAV) in Japan?: an answer from a questionnaire analysis]

The aim of this study was to determine whether the present Japanese medical care system for home oxygen therapy (HOT) and home therapy with assisted ventilation (HTAV) satisfies patients (HOT & HTAV Pts) who receive these therapies. To clarify this issue, we sent questionnaires to 807 patients with HOT and HTAV, 816 practitioners (DRs), and 110 nursing stations (NSs) in metropolitan Tokyo. Responses were eventually received from 79.9% of HOT & HTAV Pts, 32.7% of Drs and 60.9% of NSs. As a result, going to hospitals on regular basis itself (1.3 times a month) forces HOT & HTAV Pts to spend a lot of money and time at present (22.4% spent more than 5,000 yen, and 15.5% more than 60 minutes for a consultation). Although a majority of HOT & HTAV Pts now see a respiratory specialist in larger hospitals, HOT & HTAV Pts wish to see DRs, if the DRs have sufficient ability in HOT and HTAV management. On the other hand, both DRs (86.9%) and NSs (90.6%) consider that case conferences and lectures regarding HOT and HTAV on a regular basis are essential. These meetings are attended by respiratory specialists, DRs, NSs, medical equipment dealers, HOT & HTAV Pts's family members and so forth, because both DRs and NSs feel a certain anxiety about seeing HOT & HTAV Pts (68.3% DRs and 7.5% NSs do not want to see HOT & HTAV Pts). In summary, 1) a majority of HOT & HTAV Pts remain unsatisfied with the present medical care system, 2) a vague anxiety about seeing HOT & HTAV Pts makes DRs tend to avoid HOT & HTAV Pts consultations, 3) NSs frequently feel unsure how to recognize and respond properly to problems concerning HOT & HTAV Pts (62.3%). We therefore conclude that if we could succeed in organizing a better medical care system for HOT & HTAV Pts than the present one, we could turn substantially improve the quality of life of HOT & HTAV Pts in Japan.

[Efficacy and indications of home oxygen therapy for patients with chronic obstructive pulmonary disease]

Efficacy of home oxygen therapy (HOT) is well established for patients with chronic obstructive pulmonary disease who fall into chronic respiratory failure. We should consider now how the quality of life improves with HOT in those patients. According to the guideline of the Japanese Respiratory Society, indications of HOT are as follows: 1) A PaO2 of less than 55 Torr at rest while breathing room air, 2) A PaO2 between 55 Torr and 60 Torr in the presence of clear evidence of cor pulmonale, pulmonary hypertension, or a long history of severe hypoxemia during sleep or during exercise. Further studies are definitely required to pick up the patients who do not necessarily meet these indications but who may benefit from HOT.

Indications for long-term oxygen therapy: a reappraisal

Domiciliary long-term oxygen therapy (LTOT) is a routine modality of treatment in advanced chronic obstructive pulmonary disease (COPD). More than 1 million patients worldwide receive LTOT. The patients who are eligible for LTOT are those who, in the steady state, present with severe hypoxaemia (arterial oxygen tension (Pa,O2 < or = 7.3 kPa (55 mmHg). Patients with a Pa,O2 of 7.4-7.8 kPa (56-59 mmHg) are also eligible if such hypoxaemia is accompanied by an elevated haematocrit and clinical signs of cor pulmonale. LTOT was found to prolong life expectancy, improve sleep, cognitive functions and emotional status and prevent the progression of hypoxic pulmonary hypertension. It seems that such effects apply to patients with severe hypoxaemia. Recent studies have demonstrated that, in patients with moderate hypoxaemia, Pa,O2 > 7.3 kPa (55 mmHg), LTOT does not prolong life. The effects of LTOT on quality of life in that group of patients remain to be elucidated. Some chronic obstructive pulmonary disease patients with a satisfactory arterial oxygen tension at rest and awake desaturate during sleep and receive nocturnal oxygen supplementation. The patients who qualify for oxygen treatment during sleep are those in whom arterial oxygen saturation during sleep falls below 90% for > or = 2 h. The long-term physiological effects of oxygen administered only during sleep are controversial. Some data suggest that oxygen supplementation in patients desaturating during sleep prevents the progression of hypoxic pulmonary hypertension and prolongs life. Other studies do not confirm those findings.

[Usefulness of home visits in the control and evaluation of the appropriate use of home continuous oxygen therapy]

The aim of this study was to determine the usefulness of home visits to monitor and evaluate the appropriate use of domiciliary oxygen therapy (DOT). Appropriateness was based on the coincidence of circumstances needed to predict benefit from DOT: appropriate indications correct hypoxemia and patient compliance. All patients receiving DOT residing in the town of L'Hospitalet (Barcelona) in June 1994 were enrolled. During a home visit to each patient a questionnaire was administered and spirometric variables, CO in exhaled air and pulse oximetry were recorded. If DOT was not considered appropriate, the patient was referred to the hospital clinic for reevaluation of the prescription. One hundred twenty-eight patients (74% men) were visited. Mean age was 68 years. Use of DOT was seen to be appropriate in only 26% of patients. The prescription of DOT was considered strictly correct in 73 patients (49%); 13 of them were seen to have continued smoking. Of the 60 remaining patients, hypoxemia was correct with oxygen therapy in 46, and of these only 33 complied with DOT. The home visit combined with hospital monitoring allowed us to withdraw DOT from 20 patients, for whom the indications had been incorrect, and to introduce changes in oxygen supply sources for 16 patients who carried pumps. Fourteen started using a concentrator and 2 began using liquid oxygen. Periodic review is necessary for optimal treatment of DOT. The home visit is a good tool for improving DOT follow-up, as it allows the patient to be assessed in the setting where DOT is really applied. It is a monitoring method that is well accepted by the patient.

Outcome of children with carbon monoxide poisoning treated with normobaric oxygen

OBJECTIVE

To evaluate the clinical characteristics and neurologic outcome of children with carbon monoxide poisoning treated with normobaric oxygen therapy.

METHODS

We reviewed the medical records of all children with a diagnosis of carbon monoxide exposure admitted during a 10-year period. Exposures were categorized as (1) severely toxic, carboxyhemoglobin level >25%; (2) toxic, carboxyhemoglobin level 10.1 to 25%; (3) suspected toxic, carboxyhemoglobin level < or = 10% with acute neurologic manifestations; or (4) nontoxic, carboxyhemoglobin < or = 10% without acute neurologic manifestations.

RESULTS

One hundred six patients (median age, 3.5 years; range, 0.1-14.9 years) were identified, 37 with severe toxic, 37 with toxic, 13 with suspected toxic, and 19 with nontoxic exposures. The most common presenting signs or symptoms included altered level of consciousness, metabolic acidosis, tachycardia, and hypertension. All patients received normobaric oxygen for 5.5 hours (range, 0.6-44 hours). Carboxyhemoglobin levels decreased to less than 3% in 3.6 hours (range, 0-15.5 hours). Fifteen patients died, three from massive burn injury, eight from hypoxic-ischemic encephalopathy after cardiopulmonary arrest at presentation, and four from late complications of burn injury. Seven survivors did not recover their premorbid neurologic state, four of whom had respiratory arrest when rescued. Two patients had initial neurologic recovery followed by transient deterioration at 4 and 14 days after exposure. One patient developed seizures and was found to have bilateral occipital lobe infarctions 51 days after exposure.

CONCLUSION

Acute neurologic manifestations after carbon monoxide exposure are common in children. These resolve rapidly with normobaric oxygen, however. Persistent sequelae are primarily related to asphyxia. Delayed neurologic syndromes are uncommon in children treated with normobaric oxygen.

Audit of oxygen therapy

We audited the use of oxygen in our hospital. Over three days we found 119 patients using oxygen, 21 wearing their mask incorrectly or not at all. The commonest indication was chronic obstructive pulmonary disease. Forty patients had no record of arterial gas analysis. Of those who had, 29 did not require oxygen and the average time from last arterial gas analysis was 5.7 days and only eight patients were being monitored with an oximeter. Taking into account the risk of exacerbating carbon dioxide retention and the problems that arise when discharging a patient who has been receiving oxygen therapy for the duration of their admission, we fee oxygen therapy should only be administered with the knowledge of the arterial gases and with frequent reassessment during therapy.

Endoscopic placement of a tracheal oxygen catheter: a new technique

OBJECTIVE

In patients with chronic obstructive pulmonary disease (COPD), intratracheal oxygen insufflation (ITO) is an established therapeutic approach. We developed a new endoscopic technique of intratracheal catheter placement. The aim of this pilot study was to demonstrate its short-term feasibility in acutely extubated patients with moderate to severe COPD who require oxygen therapy.

DESIGN

A guide wire was inserted through a nasally passed bronchoscope and was positioned such that its tip was placed intratracheally. Using a "Seldinger technique", the tracheal catheter was then inserted over the wire to a point 2-3 cm proximal to the carina and positioned under direct vision from the bronchoscope inserted through the contralateral nose. After catheter insertion, the guide wire was removed. The patients scored catheter-associated local discomfort using a visual analogue scale. In a randomly assigned, crossover design, the effectiveness of the endoscopically (e) inserted ITO catheter was assessed by measuring the capillary blood gases, respiratory rate (RR), tidal volume (Vt) and minute ventilation (MV) after 1 h breathing room air without eITO and 1 h after eITO (flow: 3 l/min).

MEASUREMENTS AND RESULTS

The eITO catheter was placed in all patients without complications and with only minimal discomfort in two patients (spontaneously reversible cough). Compared to breathing room air, capillary O2 pressure increased (from 54.7 +/- 9.4 to 82.8 +/- 21.8 mmHg) whereas Vt (from 458.7 +/- 86.8 to 358.3 +/- 75.1 ml) and MV (from 7.7 +/- 1.5 to 5.5 +/- 1.1 l/ min) decreased significantly (each p < 0.0001) with eITO in all patients. The capillary CO2 pressure and RR did not change.

CONCLUSIONS

Acutely extubated patients in whom oxygen therapy is indicated may profit from eITO. This new technique works immediately and is thus an effective short-term intervention of potential value in the intensive care unit.

Does increasing oxygen delivery improve outcome? Yes

Increasing DO2 to supranormal levels, spontaneously or therapeutically, correlates with better survival in the critically ill patient, but not all patients who attain a DO2I greater than 600 mL/min/m2 survive. Conversely, there is often a 50% or greater survival rate in patients who do not reach normal DO2I values. No investigator has been able to show an incremental increase in survival with increasing DO2I; but studies have shown improved survival rates with increasing SVO2. The observations support the idea that absolute values for DO2I are not as important as the ability to normalize SVO2 when SVO2 is low. Therapeutic interventions may be most effective in those patients demonstrating increased peripheral oxygen extraction (SVO2 = 40% to 60%). These "type A" patients are mounting an appropriate response to increased needs. Several authors have noted increased mortality rates for patients unable to increase a low VO2 despite increased DO2. This is McClave's "type B" physiologic response. Flow dependency is not correlated with mortality. In fact, it is the patient who can raise VO2 when DO2 is increased who tends to survive. Dantzker, Giunta, and Hotchkiss propose that the flow dependency of VO2 may be a normal physiologic response. Clinical outcomes continue to support the necessity of maintaining an optimal DO2 in critically ill patients. The question of what is optimal DO2 has yet to be answered. Vincent nicely summaries the present "state of the art" in treating the critically ill: "Rather than aim at achieving arbitrary target values in all patients, we believe that this process should be based on a careful clinical evaluation of the individual patient, complemented by measurements of cardiac output, determinations of mixed venous oxygen saturation (or the oxygen-extraction ratio), and other measurements of tissue perfusion, such as the base deficit, blood lactate level, or gastric intramucosal pH." In addition, the type or stage of physiologic response should be identified. Independent markers of tissue ischemia should be sought and abnormalities corrected by increasing DO2. SVO2 should be normalized when low, again by increasing DO2. Data continue to support clinical interventions aimed at optimizing DO2. Does increasing DO2 increase the survival rates of critically ill patients? Sometimes.

Does increasing oxygen delivery improve outcome in the critically ill? No

The strategy of treating critically ill patients by increasing oxygen delivery and consumption to values previously observed among survivors of critical illness (supranormal values) is based on the belief that (1) tissue hypoxia may persist in critically ill patients despite aggressive early resuscitation to traditional endpoints of adequate tissue perfusion and (2) that increasing oxygen delivery can reverse tissue hypoxia. This article addresses the question of whether increasing oxygen delivery improves outcomes in critically ill patients by reviewing the relationship between whole-body oxygen delivery and consumption and by critically examining the randomized controlled trials that have increased oxygen delivery to supranormal values.

Home oxygen therapy

Both the efficacy and the indications for LTOT have been well defined. Most of the studies performed have focused on patients with hypoxemia caused by COPD, and the benefits observed are assumed to apply to all patients with correctable hypoxemia. For Medicare patients, oxygen is reimbursed under a prospective payment system with all delivery systems considered to be cost and therapeutically equal. Because there are, in fact, substantial clinical differences in the medical indications for individual oxygen delivery systems, it is imperative that the prescribing physician be prepared to order the therapy that is most appropriate for each patient. Most home oxygen therapy is now being ordered by primary care physicians, often functioning as gatekeepers in managed care organizations. Education of primary care physicians in this area is often inadequate, and decisions for therapy should not be delegated to the equipment suppliers. If the study of home oxygen therapy conducted by the Office of the Inspector General were repeated today, less misuse of home oxygen would probably be found because of more clearly defined indications and requirements for therapy, but it is likely that the study would find that the level of knowledge of the prescribing physician has not maintained pace with the advances in technology. Continuing education for primary care physicians in this area of respiratory care is essential for appropriate medical management now and in the future.

[Appropriate use and effectiveness of chronic domiciliary oxygen therapy in Catalonia]

BACKGROUND

The aim of this study was to study the pattern of the use of chronic domiciliary oxigenotherapy (CDO) in Catalonia, Spain.

METHODS

A transversal study including 110 patients randomly selected from a list of all the subjects with CDO (n = 3,585) was made. A domiciliary survey on the characteristics of the indication for CDO and its fulfillment was carried out. Two pulsioximetries were also performed one breathing room air and another with oxigen.

RESULTS

Of the 70 eligible patients the following factors were simultaneously observed in only 14 (20% of the total): adequate indication for CDO, use of oxigen at a flow which corrected the hypoxemia, and prescription fulfillment. The most important cause of inadequate usage of CDO was inappropriate indication since only 19 patients (27%) presented SaO2 less than or equal to 88%. Hypoxemia was not corrected in four of these 19 patients. Thirty-seven percent of the total admitted bad fulfillment, bot only one of the 15 patients with SaO2 less than or equal to 88% and in whom hypoxemia was corrected, recognized bad fulfillment. Sixty-nine percent of the patients had a document explaining the way and length of time they should receive the oxigen.

CONCLUSIONS

The inappropriate indication of CDO is the main factor influencing the low effectiveness of chronic domiciliary oxigenotherapy in Catalonia.

The impact of a postoperative oxygen therapy protocol on use of pulse oximetry and oxygen therapy

BACKGROUND

Recent evidence suggests that both pulse oximetry monitoring and oxygen (O2) therapy may be used inappropriately at times, implying the need for improved use of pulse oximetry by health-care providers.

METHODS

We studied the clinical and financial impact of a postoperative O2-therapy protocol in 2 groups of patients. Group 1 (n = 20) was comprised of patients whose physicians made all O2 therapy management decisions. Group 2 (n = 20) was comprised of patients whose O2 therapy management was performed by respiratory therapists according to an algorithm with a stop criterion of SpO2 > or = 92%. The duration of postoperative O2 therapy, the frequency of unnecessary O2 therapy, and group totals of SpO2 measurements were compared between groups using the Mann-Whitney Rank Sum Test.

RESULTS

O2 therapy was used on average (SD) 3.45 (1.28) days/patient in Group 1 and 2.1 (0.64) days/patient in Group 2 (p < 0.003). Sixteen Group-1 patients continued to receive O2 at least 24 hours after achieving a room-air SpO2 > or = 92%. Group 1 had 57 SpO2 measurements and Group 2 had 24 (p < 0.003). No adverse clinical events ascribed to hypoxemia were noted in either group.

CONCLUSIONS

Our experience suggest that implementing a uniform, clinically appropriate 'stop criterion' for low-flow O2 therapy in nonthoracic postoperative patients can shorten the duration of O2 therapy and reduce the number of SpO2 measurements without incurring additional complications.

Transtracheal oxygen--setting up a home care program

Available care for patients with transtracheal oxygen is becoming more diverse. This program uses strict standards that include staff training to ensure quality care for a specific population of patients, setting an example for other high-tech programs in home care.

Interruption of oxygen therapy during intrahospital transport of non-ICU patients: elimination of a common problem through caregiver education

Hospital inpatients frequently leave their rooms for diagnostic procedures and for other reasons. For some, interruption of oxygen therapy during transport could lead to serious complications. In our institution, non-ICU patient transport is done mainly by nonclinical personnel from an independent transport service.

MATERIALS & METHODS

We reviewed respiratory care department and transport service records for 5 arbitrarily selected days to determine the number of non-ICU patients receiving O2 therapy, the number of times these patients were transported, and the number of occasions on which O2 was used during the transport. We then interviewed the primary nurse for each patient transported without O2 and reviewed the charts of those patients to determine whether this practice was consistent with the therapy as it had been ordered. After our initial investigation showed a high rate of transport without prescribed O2, we sent memoranda to all nursing units describing proper procedures for transport of patients for whom O2 had been ordered. We then repeated the audit. Because the second audit showed the need, we conducted education sessions with all nursing personnel on the affected units and posted guidelines for O2 use during transport. A third audit was then conducted. In addition, we performed a telephone survey of respiratory care department managers to learn the patient-transport practices in all hospitals in our state with more than 200 beds, using a structured questionnaire.

RESULTS

During the initial 125 patient-days of O2 therapy, O2 accompanied patients on only 30 of 55 transports (55%). After distribution of memoranda, O2 use increased to 28 of 35 transports (80%) during 82 patient-days. The second educational effort resulted in O2 use with all 35 transports (100%) performed during 99 patient-days. Survey results from 24 hospitals with 225-680 beds showed that 11 (46%) had separate transport services and that decisions on O2 use during patient transport were generally made by nursing staff. Although respiratory care departments supplied the O2 equipment, their personnel were involved in non-ICU transports in only 5/24 hospitals.

CONCLUSIONS

Patients receiving O2 therapy on acute-care wards are often transported to other areas of the hospital without O2. This potentially dangerous practice can be corrected by respiratory care practitioners through educational efforts targeted toward those responsible for administering O2 therapy in non-ICU hospital areas.

Identification of the critical oxygen delivery for anaerobic metabolism in critically ill septic and nonseptic humans

OBJECTIVES

To determine the critical oxygen delivery threshold for anaerobic metabolism and to compare its value between septic and nonseptic critically ill patients.

DESIGN

Cohort analytic study, consecutive sample.

SETTING

Two tertiary care medical and surgical intensive care units in university hospitals.

PATIENTS

Nine septic and nine nonseptic critically ill humans. A diagnosis of sepsis was established by the presence of sepsis syndrome, positive cultures obtained within 48 hours of study, and autopsy evidence of a source of infection.

METHODS AND INTERVENTIONS

The O2 consumption (determined by indirect calorimetry), O2 delivery (calculated from the Fick equation), and concentration of arterial plasma lactate were simultaneously determined at 5- to 20-minute intervals while life support was discontinued.

MAIN OUTCOME MEASURES

Critical O2 delivery, critical O2 extraction ratio, and maximal O2 extraction ratio.

RESULTS

In all septic and eight nonseptic patients, O2 delivery and O2 consumption displayed a biphasic relationship over the range of O2 delivery studied. There were no differences in critical O2 delivery threshold (3.8 +/- 1.5 vs 4.5 +/- 1.3 mL.min-1 x kg-1; P > .28), critical O2 extraction ratio (0.61 +/- 0.05 vs 0.59 +/- 0.16; P > .64), and maximal O2 extraction ratio (0.74 +/- 0.08 vs 0.80 +/- 0.11; P > .29) between septic and nonseptic patients. These data have greater than 90% power to detect a difference of 2 mL.min-1 x kg-1 in the critical O2 delivery and 0.1 in the critical and maximal O2 extraction ratios between the septic and nonseptic groups.

CONCLUSIONS

The critical O2 delivery for anaerobic metabolism was identified from the biphasic relationship between O2 delivery and O2 consumption in individual humans. The critical O2 delivery is considerably lower than previously reported in humans with the use of pooled group data. Sepsis does not alter the critical O2 delivery for anaerobic metabolism or tissue O2 extraction ability. Interventions to increase O2 delivery to supranormal levels in critically ill humans in the hope of increasing O2 consumption may be inappropriate.