Automatic adjustment of oxygen concentration during high-flow nasal cannula treatment using a targeted SpO2 feedback system.

AIM: To test whether targeted SpO2 feedback (TSF), an automatic control system for fraction of inspired oxygen (FiO2), achieves more time in the optimal SpO2 range and/or reduces the frequency of manual adjustments to administered FiO2 compared with conventional manual titration in patients with hypoxia on high-flow nasal cannula (HFNC) therapy. STUDY DESIGN: Twenty-two patients were recruited from two hospitals. For each, two sessions of manual mode and two sessions of TSF were applied in a random order, each session lasting 2 h. The target SpO2 on TSF was 95%. Oxygen monitoring levels were classified into four SpO2 ranges: hypoxia (≤ 89%), borderline (90%-93%), optimal (94%-96%) and hyperoxia (≥ 97%). The two modes were compared based on the proportion of time spent in each SpO2 range and the number of manual FiO2 adjustments. RESULTS: The proportion of time in the optimal SpO2 range was 20.5% under manual titration mode and 65.4% under TSF (p < .01). The proportions of time in the hypoxia range were 1.1% and 0.4%, respectively (p = .31), in the borderline range 4.7% and 3.5%, respectively (p = .54), and in the hyperoxia range 73.7% and 30.7%, respectively (p < .01). There were statistical differences only in the optimal and hyperoxia SpO2 ranges. During the 8 h, the frequency of manual FiO2 adjustment was 0.7 times for the manual mode and 0.2 times for TSF, showing no statistically significant difference (p = 0.076). CONCLUSION: Compared with manual titration, TSF achieved greater time of the optimal SpO2 and less time of hyperoxia during HFNC. The frequency of manual adjustments on TSF tended to be less than on manual titration mode. RELEVANCE TO CLINICAL PRACTICE: Automatic closed-loop algorithm FiO2 monitoring systems can achieve better oxygen treatments than conventional monitoring and may reduce nurse workloads. In the era of pandemic respiratory diseases, this system can also facilitate contactless SpO2 monitoring during HFNC therapy.

Predictors of early hospital readmission in patients receiving home mechanical ventilation.

BACKGROUND: Although the proportion of patients with chronic respiratory failure requiring home mechanical ventilation (HMV) is increasing, hospital readmissions in these patients are also increasing. OBJECTIVE: We investigated the factors for early readmission in patients receiving HMV. METHODS: We retrospectively analyzed the data of adult patients readmitted to the hospital within a year who first received HMV and were discharged from the Asan Medical Center between March 2014 and February 2019. We compared the clinical characteristics at discharge before readmission between the early (readmission within 30 days) and late readmission groups (readmission between day 31 and 1 year) and investigated the clinical characteristics and outcomes at readmission. RESULTS: Of the 116 patients identified, 36.2% had been readmitted early. The patients who received invasive HMV had a higher rate of early readmission than those who received non-invasive HMV. Pneumonia was the most common reason of readmission in the two groups. The rate of aspiration was significantly higher in the early readmission group (28.6% vs. 8.1%; P = .003). In multivariate logistic regression analysis, nasogastric tube feeding, sequelae of pneumonia or acute respiratory distress syndrome, and central nervous system disorders as causes for HMV were significantly associated with early readmission. CONCLUSION: Feeding methods and causes for HMV were associated with early readmission. Educating caregivers on respiratory care (suction and feeding methods) is important for preventing early readmission.

Effects of high-flow nasal cannula in patients with mild to moderate hypercapnia: a prospective observational study.

BACKGROUND: Evidence for using high-flow nasal cannula (HFNC) in hypercapnia is still limited. Most of the clinical studies had been conducted retrospectively, and there had been conflicting reports for the effects of HFNC on hypercapnia correction in prospective studies. Therefore, more evidence is needed to understand the effect of the HFNC in hypercapnia. METHODS: We conducted a multicenter prospective observational study after applying HFNC to 45 hospitalized subjects who had moderate hypercapnia (arterial partial pressure of carbon dioxide [PaCO2], 43-70 mm Hg) without severe respiratory acidosis (pH <7.30). The primary outcome was a change in PaCO2 level in the first 24 hours of HFNC use. The secondary outcomes were changes in other parameters of arterial blood gas analysis, changes in respiration rates, and clinical outcomes. RESULTS: There was a significant decrease in PaCO2 in the first hour of HFNC application (-3.80 mm Hg; 95% confidence interval, -6.35 to -1.24; P<0.001). Reduction of PaCO2 was more prominent in subjects who did not have underlying obstructive lung disease. There was a correction in pH, but no significant changes in respiratory rate, bicarbonate, and arterial partial pressure of oxygen/fraction of inspired oxygen ratio. Mechanical ventilation was not required for 93.3% (42/45) of our study population. CONCLUSIONS: We suggest that HFNC could be a safe alternative for oxygen delivery in hypercapnia patients who do not need immediate mechanical ventilation. With HFNC oxygenation, correction of hypercapnia could be expected, especially in patients who do not have obstructive lung diseases.

Global and Regional Ventilation during High Flow Nasal Cannula in Patients with Hypoxia.

BACKGROUND: High flow nasal cannula (HFNC) is known to increase global ventilation volume in healthy subjects. We sought to investigate the effect of HFNC on global and regional ventilation patterns in patients with hypoxia. METHODS: Patients were randomized to receive one of two oxygen therapies in sequence: nasal cannula (NC) followed by HFNC or HFNC followed by NC. Global and regional ventilation was assessed using electric impedance tomography. RESULTS: Twenty-four patients participated. Global tidal variation (TV) in the lung was higher during HFNC (NC, 2,241 ± 1,381 arbitrary units (AU); HFNC, 2,543 ± 1,534 AU; P < 0.001). Regional TVs for four iso-gravitational quadrants of the lung were also all higher during HFNC than NC. The coefficient of variation for the four quadrants of the lung was 0.90 ± 0.61 during NC and 0.77 ± 0.48 during HFNC (P = 0.035). Within the four gravitational layers of the lung, regional TVs were higher in the two middle layers during HFNC when compared to NC. Regional TV values in the most ventral and dorsal layers of the lung were not higher during HFNC compared with NC. The coefficient of variation for the four gravitational layers of the lung were 1.00 ± 0.57 during NC and 0.97 ± 0.42 during HFNC (P = 0.574). CONCLUSIONS: In patients with hypoxia, ventilation of iso-gravitational regions of the lung during HFNC was higher and more homogenized compared with NC. However, ventilation of gravitational layers increased only in the middle layers. (Clinical trials registration number: NCT02943863).

Clinical outcomes of cardiac arrest patients according to opioid use history.

PURPOSE: Opioid analgesics are potent respiratory depressants. The purpose of this study was to describe the effects of opioids administered within 24hours before cardiac arrest on clinical outcomes. MATERIALS AND METHODS: We retrospectively collected the cardiac arrest data of noncancer patients who were admitted to the general ward of Asan Medical Center from January 2008 to August 2012. We investigated the proportion of these patients who received opioids within 24hours of a cardiac arrest event, as well as the cardiac arrest characteristics, survival rates, and opioid administration patterns. RESULTS: Of the 193 patients identified, 58 (30%) had been administered opioids within the previous 24hours (the opioid group), whereas the remaining 135 (70%) had not been administered opioids (the nonopioid group). The survival rate did not differ significantly between these 2 groups. In the opioid group, as-needed opioid administration was associated with a lower 24-hour survival rate than regular opioid administration (9 [33.3%] of 27 patients vs 20 [64.5%] of 31 patients; P=.030). In multivariate logistic regression analysis, as-needed opioid administration was negatively associated with 24-hour survival. CONCLUSIONS: Opioid administration within 24hours before cardiac arrest per se was not associated with adverse outcomes. However, administration of opioid analgesics on an as-needed basis was associated with poorer survival outcomes than regular dosing. Greater attention should be paid to patients who receive as-needed opioid administration in the general ward.

Failure of high-flow nasal cannula therapy may delay intubation and increase mortality.

PURPOSE: Intubation in patients with respiratory failure can be avoided by high-flow nasal cannula (HFNC) use. However, it is unclear whether waiting until HFNC fails, which would delay intubation, has adverse effects. The present retrospective observational study assessed overall ICU mortality and other hospital outcomes of patients who received HFNC therapy that failed. METHODS: All consecutive patients in one tertiary hospital who received HFNC therapy that failed and who then required intubation between January 2013 and March 2014 were enrolled and classified according to whether intubation started early (within 48 h) or late (at least 48 h) after commencing HFNC. RESULTS: Of the 175 enrolled patients, 130 (74.3 %) and 45 (25.7 %) were intubated before and after 48 h of HFNC, respectively. The groups were similar in terms of most baseline characteristics. The early intubated patients had better overall ICU mortality (39.2 vs. 66.7 %; P = 0.001) than late intubated patients. A similar pattern was seen with extubation success (37.7 vs. 15.6 %; P = 0.006), ventilator weaning (55.4 vs. 28.9 %; P = 0.002), and ventilator-free days (8.6 ± 10.1 vs. 3.6 ± 7.5; P = 0.011). In propensity-adjusted and -matched analysis, early intubation was also associated with better overall ICU mortality [adjusted odds ratio (OR) = 0.317, P = 0.005; matched OR = 0.369, P = 0.046]. CONCLUSIONS: Failure of HFNC might cause delayed intubation and worse clinical outcomes in patients with respiratory failure. Large prospective and randomized controlled studies on HFNC failure are needed to draw a definitive conclusion.