Rebreathing during oxygen treatment with face mask. The effect of oxygen flow rates on ventilation

Thoracic Society of Australia and New Zealand Position Statement on Acute Oxygen Use in Adults: 'Swimming between the flags'

Oxygen is a life-saving therapy but, when given inappropriately, may also be hazardous. Therefore, in the acute medical setting, oxygen should only be given as treatment for hypoxaemia and requires appropriate prescription, monitoring and review. This update to the Thoracic Society of Australia and New Zealand (TSANZ) guidance on acute oxygen therapy is a brief and practical resource for all healthcare workers involved with administering oxygen therapy to adults in the acute medical setting. It does not apply to intubated or paediatric patients. Recommendations are made in the following six clinical areas: assessment of hypoxaemia (including use of arterial blood gases); prescription of oxygen; peripheral oxygen saturation targets; delivery, including non-invasive ventilation and humidified high-flow nasal cannulae; the significance of high oxygen requirements; and acute hypercapnic respiratory failure. There are three sections which provide (1) a brief summary, (2) recommendations in detail with practice points and (3) a detailed explanation of the reasoning and evidence behind the recommendations. It is anticipated that these recommendations will be disseminated widely in structured programmes across Australia and New Zealand.

Noninvasive Ventilation and Oxygenation Strategies

Noninvasive ventilation (NIV) provides respiratory support without the use of invasive ventilation with techniques that do not bypass the upper airway. NIV is particularly attractive given its associated reduced risk of complications associated with intubation. Available NIV modes include nasal cannula, simple mask, nonrebreather, high flow nasal cannula, continuous positive airway pressure (CPAP), and bilevel positive airway pressure. Acute exacerbation of COPD, cardiogenic pulmonary edema, and COVID-19 are conditions for which NIV has shown to be beneficial, whereas there is no consensus among the use of NIV in trauma patients and ARDS.

German S3 Guideline: Oxygen Therapy in the Acute Care of Adult Patients

BACKGROUND

Oxygen (O2) is a drug with specific biochemical and physiological properties, a range of effective doses and may have side effects. In 2015, 14% of over 55,000 hospital patients in the UK were using oxygen. 42% of patients received this supplemental oxygen without a valid prescription. Health care professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

A national S3 guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. A literature search was performed until February 1, 2021, to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the quality of evidence and for grading guideline recommendation, and a formal consensus-building process was performed.

RESULTS

The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O2 therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are based depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

This is the first national guideline on the use of oxygen in acute care. It addresses health care professionals using oxygen in acute out-of-hospital and in-hospital settings.

Superiority of OxyMaskTM with less carbon dioxide rebreathing in children

Despite the growing importance of oxygen-delivery devices worldwide, there are only a few reports of physiological data on various oxygen masks in children. The possibility of carbon dioxide (CO₂) rebreathing has been a prevalent concern with the use of oxygen-delivery devices. OxyMask Kid^TM (Southmedic Inc. Canada; hereafter OxyMask) is expected to reduce CO₂ rebreathing even at low oxygen flow rates because of its structural features. Biological data using OxyMask in children have not been well investigated. Measured respiratory parameters of OxyMask with those of a simple oxygen mask in healthy children were compared. Ten subjects were enrolled, with a median age of 5.4 years. All subjects used both OxyMask and a simple oxygen mask. The fraction of inspiratory oxygen (F_IO₂), partial pressure of inspiratory CO₂ (P_ICO₂), and partial pressure of end-tidal CO₂ were measured using a sidestream gas-sampling monitor in all subjects. The oxygen flow rate was set at 1, 3, 5, and 10 L/min. F_IO₂ levels were higher with OxyMask than those with the simple oxygen mask at 3 L/min of oxygen. P_ICO₂ levels were significantly lower with OxyMask than those with the simple oxygen mask (1.5 mmHg vs. 3.7 mmHg at 1 L/min, P = 0.005; 1.0 mmHg vs. 2.7 mmHg at 3 L/min, P = 0.005, respectively), whereas P_ICO₂ levels were higher at low oxygen flow rates with both masks.Conclusion: Our results showed that higher F_IO₂ and less CO₂ rebreathing were achieved with OxyMask than those with a simple oxygen mask at low flow rates of oxygen in healthy children. What is Known: • OxyMask is expected to reduce carbon dioxide rebreathing even at low oxygen flow rates because of its structural features. • Efficacy has been demonstrated in experimental models and adult data, but clinical data on the use of the OxyMask in children are limited. What is New: • Higher fraction of inspiratory oxygen and lesser carbon dioxide rebreathing were achieved with OxyMask than with a simple oxygen mask at low flow rates of oxygen in healthy children.

[German S3 Guideline - Oxygen Therapy in the Acute Care of Adult Patients]

BACKGROUND

 Oxygen (O₂) is a drug with specific biochemical and physiologic properties, a range of effective doses and may have side effects. In 2015, 14 % of over 55 000 hospital patients in the UK were using oxygen. 42 % of patients received this supplemental oxygen without a valid prescription. Healthcare professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

 A S3-guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. Literature search was performed until Feb 1st 2021 to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used and for assessing the quality of evidence and for grading guideline recommendation and a formal consensus-building process was performed.

RESULTS

 The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O₂ therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

 This is the first national guideline on the use of oxygen in acute care. It addresses healthcare professionals using oxygen in acute out-of-hospital and in-hospital settings. The guideline will be valid for 3 years until June 30, 2024.

Effect of High-Flow Nasal Cannula Oxygen Therapy on Pediatric Patients With Congenital Heart Disease in Procedural Sedation: A Prospective, Randomized Trial

OBJECTIVES

The study was conducted to compare the outcome of high-flow nasal cannula (HFNC) oxygen therapy with conventional oxygen therapy through a simple oxygen mask for pediatric patients with congenital heart disease during percutaneous intervention while under procedural sedation.

DESIGN

Prospective, randomized and controlled trial.

SETTING

A Cantonese cardiac center in China.

PARTICIPANTS

Two hundred American Society of Anesthesiologists classification II pediatric patients were enrolled from April 25, 2018 to November 28, 2018.

INTERVENTIONS

Patients scheduled for percutaneous closure of a heart defect under deep sedation with propofol, midazolam and fentanyl by an anesthesiologist were randomized (1:1) to receive oxygen therapy through a simple oxygen mask or through the HFNC system.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the lowest oxygen saturation (SpO₂). Secondary outcomes included the incidence of hypoxia (SpO₂ < 90%), requirement for noninvasive respiratory support, change in the gastric antrum area and other adverse events. Blood gas analysis results also were compared. Oxygen therapy through the HFNC system improved the lowest SpO₂ (99% [94%-100%]), as compared with the mask group (99% [72%-100%]), p < 0.001. Seven patients out of 99 (7.1%) in the mask group had hypoxia or required bag-mask ventilation, whereas no such patient was reported in the HFNC group, p < 0.001. There were no differences between the groups in terms of gastric distention, procedure length, total propofol dose, atropine use or other complications.

CONCLUSION

When compared with simple mask oxygenation, HFNC could reduce the incidence of desaturation, the need for airway assisted ventilation and risk of carbon dioxide retention without causing hemodynamic instability or gastric distention. It is effective for pediatric patients with non-cyanotic congenital heart disease who require procedural sedation.

Rapid reduction of macular edema due to retinal vein occlusion with low-dose normobaric hyperoxia

PURPOSE

We investigated the effects of a relatively inexpensive, non-invasive, short-term treatment with low-dose normobaric hyperoxia (NBH) on macular edema in patients with retinal vein occlusion (RVO).

METHODS

Participants with macular edema associated with RVO were treated with 5 LPM of NBH via facemask (40% fraction of inspired oxygen, FIO2) for 3 h. Patients with non-fovea involving edema who elected to be observed returned for a second treatment 1 month later to test reproducibility.

RESULTS

A 3-h session of NBH (n = 45) resulted in decreased maximum macular thickness (MMT) (mean 7.10%, t₃₄=9.63 P<.001) and central macular thickness (CMT) (mean 4.64%, t₃₄=6.90, P<.001) when compared to untreated eyes with RVO measured over the same period of time (n = 12) or their healthy fellow eye (n = 34; MMT:t₃₄=-9.60, P<.001;CMT: t₃₄=-6.72, P<.001). Patients who had a second NBH treatment 1 month later experienced a recurrence of their edema, but demonstrated a similar significant reduction in MMT and CMT after the second NBH treatment.

CONCLUSIONS

Three-hour treatment with 40% FIO2 NBH results in a significant reduction in MMT and CMT. This study supports an ischemic mechanism for macular edema associated with retinal vein occlusion.

TRANSLATIONAL RELEVANCE

Short-term low-dose normobaric hyperoxia is a simple, inexpensive, and ubiquitous treatment that may provide an alternate or adjunctive approach to treating macular edema in patients who are resistant to or cannot afford anti-VEGF medications.

High-Flow Oxygen through Nasal Cannula vs. Non-Invasive Ventilation in Hypercapnic Respiratory Failure: A Randomized Clinical Trial

High-flow oxygen through nasal cannula (HFNC) provides adequate oxygenation and can be an alternative to noninvasive ventilation (NIV) for patients with hypoxemic respiratory failure. The aim of the present study was to assess the efficacy of HFNC versus NIV in hypercapnic respiratory failure. Patients (n = 40) who were admitted to the Emergency Department of Alexandra Hospital due to hypercapnic respiratory failure (PaCO₂ ≥ 45 mmHg) were randomized assigned into two groups, i.e., an intervention group (use of HFNC, n = 20) and a control group (use of NIV, n = 20). During their hospitalization in the Intensive Care Unit, vital signs (respiratory and heart rate, arterial blood pressure) and arterial blood gases (ABG) were closely monitored on admission, after 24 h and at discharge. No difference between the two groups regarding the duration of hospitalization and the use of HFNC or NIV was observed (p > 0.05). On admission, the two groups did not differ in terms of gender, age, body mass index, APACHE score, predicted death rate, heart rate, arterial blood pressure and arterial blood gases (p > 0.05). Respiratory rate in the HFNC group was lower than in the NIV group (p = 0.023). At discharge, partial carbon dioxide arterial pressure (PaCO₂) in the HFNC group was lower than in the NIV group (50.8 ± 9.4 mmHg versus 59.6 ± 13.9 mmHg, p = 0.024). The lowerPaCO₂ in the HFNC group than in the NIV group indicated that HFNC was superior to NIV in the management of hypercapnic respiratory failure.

Carbon dioxide narcosis due to inappropriate oxygen delivery: a case report

BACKGROUND

Oxygen delivery to patients with chronic obstructive pulmonary disease may be challenging because of their potential hypoxic ventilatory drive. However, some oxygen delivery systems such as non-rebreathing face masks with an oxygen reservoir bag require high oxygen flow for adequate oxygenation and to avoid carbon dioxide rebreathing.

CASE PRESENTATION

A 72-year-old Caucasian man with severe chronic obstructive pulmonary disease was admitted to the emergency department because of worsening dyspnea and an oxygen saturation of 81% measured by pulse oximetry. Oxygen was administered using a non-rebreathing mask with an oxygen reservoir bag attached. For fear of removing the hypoxic stimulus to respiration the oxygen flow was inappropriately limited to 4L/minute. The patient developed carbon dioxide narcosis and had to be intubated and mechanically ventilated.

CONCLUSIONS

Non-rebreathing masks with oxygen reservoir bags must be fed with an oxygen flow exceeding the patient's minute ventilation (>6-10 L/minute.). If not, the amount of oxygen delivered will be too small to effectively increase the arterial oxygen saturation. Moreover, the risk of carbon dioxide rebreathing dramatically increases if the flow of oxygen to a non-rebreathing mask is lower than the minute ventilation, especially in patients with chronic obstructive pulmonary disease and low tidal volumes. Non-rebreathing masks (with oxygen reservoir bags) must be used cautiously by experienced medical staff and with an appropriately high oxygen flow of 10-15 L/minute. Nevertheless, arterial blood gases must be analyzed regularly for early detection of a rise in partial pressure of carbon dioxide in arterial blood in patients with chronic obstructive pulmonary disease and a hypoxic ventilatory drive. These patients are more safely managed using a nasal cannula with an oxygen flow of 1-2L/minute or a simple face mask with an oxygen flow of 5L/minute.

Capnographic Analysis of Minimum Mandatory Flow Rate for Hudson Face Mask: A Randomized Double-blind Study

BACKGROUND

Oxygen supplementation through Hudson type face mask is frequently used in perioperative settings. Hudson mask is a variable rate performance device with the risk of rebreathing. Studies using capnography to find out an actual fraction of rebreathing in spontaneously breathing patients are not available.

AIMS

In this study, we analyzed the effects of different flow rates through Hudson mask with capnography on fractional inspired carbon dioxide (FiCO₂).

SETTING AND DESIGNS

Forty patients posted for minor surgeries under monitored anesthesia care were divided into four groups. They received oxygen flow rate of 3 L/min, 4 L/min, 5 L/min, and 6 L/min as per group division, through Hudson mask.

MATERIALS AND METHODS

Parameters such as pulse rate, noninvasive blood pressure, oxygen saturation, respiratory rate (RR), end-tidal carbon dioxide (EtCO₂), and FiCO₂ were noted at baseline. After starting oxygen supplementation, these parameters were monitored every minute for ten minutes. Statistical analysis was done using analysis of variance and Kruskal-Wallis test. Pearson correlation was used to establish a relation between RR and FiCO₂.

RESULTS AND CONCLUSIONS

EtCO₂ and FiCO₂ were comparable in all four groups with no statistical significance. There was strong positive correlation seen between RR and FiCO₂ at a flow rate of 3 L/min while negative correlation in other groups. We conclude that FiCO₂ is similar at all flow rates while breathing through Hudson mask. Increase in RR can cause increase in FiCO₂ at lower flow rate, which is within physiological tolerance limits.

Low- versus high-flow oxygen delivery systems in children with lower respiratory infection

BACKGROUND

Delivery of supplemental oxygen is the initial vital management of hypoxemic acute lower respiratory infection (HALRI). Oxygen delivery systems include low-flow and high-flow devices. In high-flow devices such as the Venturi mask, a constant mixture of oxygen is delivered. As a result, increased rate of breathing does not affect the concentration of oxygen delivered. In this study, we compared the efficacy of oxygen masks and Venturi masks in the management of hypoxemia in pediatric patients.

METHODS

A total of 65 children, aged 3-36 months, diagnosed with HALRI, were enrolled. Patients were allocated into groups, via simple alternate randomization, to receive oxygen through an oxygen mask or through a Venturi mask. Respiratory rate, heart rate, retraction, blood gas parameters, oxygen saturation, length of hospitalization, and oxygenation were recorded before and after oxygen treatment.

RESULTS

After 24 h of treatment, respiratory rate was significantly lower among patients in the Venturi mask group compared with the oxygen mask group. Duration of supplemental oxygen and length of hospitalization were significantly lower in the Venturi mask group compared with the oxygen mask group.

CONCLUSION

In both groups, there was marked improvement in all measured parameters following introduction of supplemental oxygen. Oxygen was delivered more efficiently, however, by high-flow systems. The Venturi mask may decrease the total duration of oxygen usage time as well as the length of hospitalization among young children with HALRI through rapid symptom resolution.

Thoracic Society of Australia and New Zealand oxygen guidelines for acute oxygen use in adults: 'Swimming between the flags'

The purpose of the Thoracic Society of Australia and New Zealand guidelines is to provide simple, practical evidence-based recommendations for the acute use of oxygen in adults in clinical practice. The intended users are all health professionals responsible for the administration and/or monitoring of oxygen therapy in the management of acute medical patients in the community and hospital settings (excluding perioperative and intensive care patients), those responsible for the training of such health professionals, and both public and private health care organizations that deliver oxygen therapy.

Performance of a new oxygen delivery device for potentially infectious critically ill patients

In patients with highly contagious diseases that are spread by respiratory droplets or air-borne particles, the use of high-flow oxygen may carry a significant risk of nosocomial transmission. We tested a new oxygen delivery device designed to address these problems by simulating 108 patients with sepsis and respiratory failure. The device being tested consisted of an airtight mask, a bacterial and viral filter, a T-shaped reservoir (50 and 100 ml) and oxygen delivery tubing connected directly to the mask. When tested with a 50-ml reservoir, a high fractional oxygen concentration was achieved: mean (SD) 0.83 (0.11) at a flow of 15 l.min(-1) oxygen. The 50-ml reservoir, when compared with the 100-ml reservoir, was associated with reduced carbon dioxide rebreathing (mean (SD) inspired fractional carbon dioxide concentration 2.5 (1.0) vs 3.0 (1.1), respectively, p = 0.009) and reduced inspiratory resistive work of breathing (mean (SD) 1.0 (0.6) J.l(-1) vs 1.2 (0.5) J.l(-1), respectively, p = 0.028). However, rebreathing and work of breathing were relatively high if a high respiratory rate was simulated. We conclude that the novel oxygen device we describe, equipped with the 50-ml T-shaped reservoir, is suitable for potentially infectious patients with type-1 respiratory failure but without marked tachypnoea.

Postoperative oxygen therapy

Much has been published in the medical literature concerning adverse events relating to the surgical patient. Among the notable disorders requiring the expertise of the postanesthesia care unit nurse are the diagnosis and management of respiratory dysfunction acutely attributable to the effects of surgery and anesthesia. Inhalational and/or intravenous anesthetic agents contribute to pathophysiological alterations that lend to the development of hypoxemia in the postoperative period. When patients present with preexisting respiratory disease, their care is frequently more complex and challenging. This review session will address the oxygenation component of respiration and the perioperative influences that alter it as well as treatment considerations for normalizing oxygenation.

Role of dissolved plasma oxygen in hyperoxia-induced contrast

Currently, hyperoxia is being investigated as a method for producing contrast in magnetic resonance images of the brain, solid tumors, and the eye. However, the underlying physiological mechanisms involved in this type of contrast are still not completely understood. For example, under what conditions would dissolved plasma oxygen contribute to the hyperoxia-induced contrast? Using the eye as a model system, we varied the level of dissolved plasma oxygen and observed different patterns of contrast in the vitreous. The observed contrast changes were consistent with tissue oxygen buffering by hemoglobin at an arterial PO2 of 200 mm Hg and dissolved oxygen offloading at arterial PO2's > 350 mm Hg. These data demonstrate that dissolved plasma oxygen does not become an important contrast mechanism until the arterial oxygen tension exceeds approximately 350 mm Hg. The implication of this result to studies in other organs is discussed.

A comparison of three variable performance devices for postoperative oxygen therapy

Eleven patients in the intensive care unit following major abdominal surgery with a nasogastric tube in situ and receiving oxygen via facemask were allocated to receive in a random sequence oxygen at 4 l.min-1 via a Hudson mask, nasal cannulae or a nasal catheter with foam collar at the distal end. A significantly greater PaO2 was achieved using both the nasal catheter with foam collar (p < 0.01) and Hudson mask (p < 0.05) compared to the nasal cannulae. There were no significant differences in the PaCO2 or SpO2 values obtained between the devices. In the majority of postoperative patients in whom a variable performance device is indicated, nasal devices appear preferable in terms of patient comfort and compliance. The nasal catheter with foam collar produced a significantly greater PaO2 than nasal cannulae in patients with a nasogastric tube in situ.

The rebreathing characteristics of the Hudson oxygen mask

A lung model was used to study the effect of varying minute ventilation, oxygen flow and inspiratory : expiratory ratio on the rebreathing characteristics of the Hudson oxygen mask. The onset of rebreathing was detected using two different sets of criteria; those defined by Kain et al. and Humphrey. The onset of rebreathing was also quantified in terms of the inspired volume of carbon dioxide and increases in deadspace. The magnitude of rebreathing was increased by reducing oxygen inflow and increasing minute ventilation. Variation in I : E ratio between 1 : 1 and 1 : 4 had little effect on rebreathing. Using the clinical criteria of Kain et al, the onset of rebreathing was detected when oxygen inflow/minute ventilation ratio was reduced below 0.78 on average. With the other criterion, rebreathing occurred when the ratio was 0.46.