Use of high-flow nasal cannula oxygen and risk factors for high-flow nasal cannula oxygen failure in critically-ill patients with COVID-19.

BACKGROUND: High-flow nasal oxygen therapy (HFNC) may be an attractive first-line ventilatory support in COVID-19 patients. However, HNFC use for the management of COVID-19 patients and risk factors for HFNC failure remain to be determined. METHODS: In this retrospective study, we included all consecutive COVID-19 patients admitted to our intensive care unit (ICU) in the first (Mars-May 2020) and second (August 2020- February 202) French pandemic waves. Patients with limitations for intubation were excluded. HFNC failure was defined as the need for intubation after ICU admission. The impact of HFNC use was analyzed in the whole cohort and after constructing a propensity score. Risk factors for HNFC failure were identified through a landmark time-dependent cause-specific Cox model. The ability of the 6-h ROX index to detect HFNC failure was assessed by generating receiver operating characteristic (ROC) curve. RESULTS: 200 patients were included: HFNC was used in 114(57%) patients, non-invasive ventilation in 25(12%) patients and 145(72%) patients were intubated with a median delay of 0 (0-2) days after ICU admission. Overall, 78(68%) patients had HFNC failure. Patients with HFNC failure had a higher ICU mortality rate (34 vs. 11%, p = 0.02) than those without. At landmark time of 48 and 72 h, SAPS-2 score, extent of CT-Scan abnormalities > 75% and HFNC duration (cause specific hazard ratio (CSH) = 0.11, 95% CI (0.04-0.28), per + 1 day, p < 0.001 at 48 h and CSH = 0.06, 95% CI (0.02-0.23), per + 1 day, p < 0.001 at 72 h) were associated with HFNC failure. The 6-h ROX index was lower in patients with HFNC failure but could not reliably predicted HFNC failure with an area under ROC curve of 0.65 (95% CI(0.52-0.78), p = 0.02). In the matched cohort, HFNC use was associated with a lower risk of intubation (CSH = 0.32, 95% CI (0.19-0.57), p < 0.001). CONCLUSIONS: In critically-ill COVID-19 patients, while HFNC use as first-line ventilatory support was associated with a lower risk of intubation, more than half of patients had HFNC failure. Risk factors for HFNC failure were SAPS-2 score and extent of CT-Scan abnormalities > 75%. The risk of HFNC failure could not be predicted by the 6-h ROX index but decreased after a 48-h HFNC duration.

Effect of Ambulatory Oxygen on the Respiratory Pattern during the 6 Min Walking Test in Patients with Interstitial Lung Diseases.

INTRODUCTION: Patients with pulmonary fibrosis experience early oxyhemoglobin desaturation under effort, which limits their ability to exercise and their quality of life. Recent studies have shown that in resting normoxaemic patients who become hypoxemic under exertion, administration of outpatient oxygen significantly improves stress dyspnoea and quality of life. It is unclear how this happens, since oxygen administration does not act directly on dyspnoea, and does not appear to have much effect on the heart rate and pulmonary artery pressure. We tested the hypothesis that correcting the hypoxaemia could reduce the increase in respiratory effort during the 6 min walking test, recording the breathing pattern during administration of oxygen or placebo. METHODS: We evaluated 20 patients with fibrotic interstitial lung diseases (17 males and 3 females; mean age 72 ± 2 years; M ± SE) with a resting SpO2 ≥92 that fell to ≤88% during the 6 min walk test (6MWT). After first establishing the oxygen flow necessary to prevent desaturation, the patients underwent two further 6MWT, 15-20 min apart, one with administration of medical air and one with oxygen at the same flow, in randomized double-blind order. During the test, SpO2, heart rate, respiratory rate, tidal volume and minute ventilation (VE) were recorded, using a Spiropalm spirometer (Cosmed, Rome, Italy). RESULTS: Oxygen saturation during the 6MWT decreased to a minimum value of 82.3% (95% CI 80.1-84.5%) during placebo and to 92% (90.3-93.7%) during oxygen with an average difference of 9.7% (7.8-11.6%, p < 0.0001). On the contrary, heart rate showed an increasing trend with walking time reaching a significantly higher maximum rate during placebo, with a difference of 5.4 bpm (2.9-8.7, p < 0.005) compared to oxygen. The distance walked was slightly but significantly greater after oxygen by 28 m (2-53, p < 0.05) and end of test dyspnoea after placebo by 0.6 points (0.1-1.1, p < 0.05). Respiratory rate increased over time, without differences between oxygen and placebo in the first minute of walking, then increasing significantly more during placebo (p < 0.0005). With placebo, tidal volume increased rapidly reaching a plateau at about 48% of FVC after 3 min, while with oxygen, the increase was slower, reaching a maximum of about 45% of FVC at the end of the test. Nevertheless, the difference was highly significant (p < 0.0005) at all the time points. Minute ventilation also increased significantly with walking time but remained at a highly significant lower level during oxygen than placebo at all the time points. Mean reduction in VE during the test with oxygen compared to placebo was 4.4 L/min (3.9-4.9, p < 0.0005). CONCLUSION: In our ILD patients, administration of outpatient oxygen during walking was related to a reduced increase in heart rate, respiratory rate, tidal volume and minute ventilation necessary to meet increased oxygen requirements, resulting in a lower workload on the cardiovascular system and on respiratory muscles and a consequent reduction in dyspnoea.

Oxigenoterapia en vuelos nacionales e internacionales en la Argentina / Oxygen therapy during Argentine-based national and international flights

No existe estudio que evalúe el estado de la oxigenoterapia en vuelo (OV) en nuestro país. El objetivo de este estudio fue evaluar los requisitos, dificultades, sistemas y costos de la OV de las companías aéreas nacionales (N) e internacionales (I) que operan desde Buenos Aires. Se utilizó la misma encuesta telefónica y metodología que el estudio de Stoller y col.12. Los autores se comunicaron telefónicamente con 25 aerolíneas que operaban en los dos aeropuertos de Buenos Aires en julio de 2007, y se interrogó sobre los requisitos necesarios para viajar, sistemas y costos. Se usaron técnicas estadísticas convencionales siendo significativa p<0.05. De 25 aerolíneas, se descartaron seis (24%) por falta de información (60% de las N y 16% de las I). El 100% de las N permitían la OV vs. 80% de las I (p<0.05). El 100% de las N y 94% de las I exigían certificado médico (p=NS). El 71% de las N requerían de aviso previo vs. 100% de las I (p<0.05). El 50% de las N proveían interfases de administración de oxígeno vs. 87% de las I (p=NS). El 100% de las N disponían del oxígeno sin cargo, vs. 50% de las I (p=NS). El costo oscilaba entre 70 a 300 dólares por escala. En conclusión, se observó una marcada dificultad en la provisión de información de las compañías aéreas, y restricciones de su uso. El costo es muy variable y se da principalmente en las compañías aéreas I. Consideramos necesario implementar acciones que faciliten el acceso de los pacientes y médicos a la información pertinente de cada compañía aérea sobre OV.

There are no data about supplemental oxygen in flight in our country. The objective of our study was to evaluate arranging in-flight-oxygen required by a simulated traveler, system of administration and costs, and to compare the results between Argentine-based (A) and international (I) airlines. The questionnaire used was similar to that of Stoller et al12. Data collection consisted of telephone calls placed by one of the authors to all commercial air carriers listed in our two Buenos Aires City airports during July 2007. A structured interview with questions was addressed on issues that an oxygen-using air traveler would need to arrange in-flight oxygen. Of the 25 airlines, 6 were discarded because of lack of information (24%, three A -60%-and one I-16%-). All A allowed in-flightoxygen vs. 80% of I (p<0.05), 100% of A and 94% of I required a medical certificate (p=NS); 71% of A and 100% of I required previous notification (p<0.05); 50% of A and 87% of I provided patient interphases of oxygen administration (p=NS). Free of charge oxygen could be provided by 100% of A and 50% of I, with airline charge between 70 to 300 dollars. In conclusion, we observed different policies, rules, availability, and a pronounced lack of standardization of airline information. The cost of oxygen was very different between airlines and it was superior on I. It will be necessary to carry out actions to facilitate patient access to oxygentherapy and to standardize medical information among airlines in our country.

Avaliação ventilométrica e hemogasométrica da oxigenoterapia por cateterização nasal em cães após toracotomia lateral intercostal / Ventilometric and hemogasometric evaluation of oxygenotherapy by nasal catheter in dogs after lateral intercostal thoracotomy

Doze cães, sem raça definida, foram submetidos à toracotomia lateral intercostal e divididos em dois grupos de diferentes tratamentos pós-operatórios, sendo que seis animais receberam oxigenoterapia por cateterização nasal e os demais não receberam este tratamento. Os animais de ambos os grupos estiveram sob cuidados intensivos em sala de recuperação por quatro horas de período pós-operatório, quando foram monitorados o volume corrente pulmonar, a gasometria arterial, o tempo de reperfusão capilar, a coloração de mucosas ocular e oral, as frequências respiratória e cardíaca, a temperatura retal e a tolerância ao uso do cateter nasal. Os resultados obtidos demonstraram que ocorre diminuição dos valores de pressão parcial arterial de oxigênio abaixo dos índices fisiológicos. A análise estatística dos dados revelou diferença significativa entre os cães que receberam oxigênio via cateter nasal e os não tratados, no período pós-toracotomia.

Lateral intercostal thoracotomy was performed in twelve mongrel dogs divided in two groups for different postoperative treatments. Six animais received oxigen by nasal catheter after surgery. Both groups were maintained in a recovery room during four hours in wich were monitored the pulmonary tidal volume, the arterial blood gas values, the capilar refil l time, the mucous membrane color, the respiratory and heart rates, the rectal temperature, and the tolerance to the nasal catheter. The results demonstrated a reduction on the arterial oxygen parcial pressure levels after the thoracotomy. The comparativo statistical analyse showed a significant diference between the group that received oxygen by nasal catheter and the group that recived no treatment.