Saudi Journal of Anaesthesia

: 2022  |  Volume : 16  |  Issue : 2  |  Page : 267--268

HACOR score to predict failure of non-invasive ventilation in patients with acute hypoxemic respiratory failure: When simplicity is best

Abhijit Nair1, Antonio Esquinas2,  
1 Department of Anaesthesiology, Ibra Hospital, Ministry of Health-Oman, P.O. Box 275, Ibra-414, Sultanate of Oman
2 Intensive Care Unit, Hospital Morales Meseguer, Murcia, Spain

Correspondence Address:
Abhijit Nair
Department of Anaesthesiology, Ibra Hospital, Ministry of Health-Oman, P.O. Box 275, Ibra-414
Sultanate of Oman

How to cite this article:
Nair A, Esquinas A. HACOR score to predict failure of non-invasive ventilation in patients with acute hypoxemic respiratory failure: When simplicity is best.Saudi J Anaesth 2022;16:267-268

How to cite this URL:
Nair A, Esquinas A. HACOR score to predict failure of non-invasive ventilation in patients with acute hypoxemic respiratory failure: When simplicity is best. Saudi J Anaesth [serial online] 2022 [cited 2022 Nov 28 ];16:267-268
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There is indeed no doubt that non-invasive ventilation (NIV) is extremely useful in patients who present with acute hypoxemic respiratory failure (AHRF). The advantages of NIV are several like it can be managed in wards by nurses and respiratory therapists and does not require physicians, intensivists, or anaesthesiologists all the time. Although NIV reduces work of breathing and avoids intubation in many patients, the rate of failure of NIV is very high (25-49%).[1]

To predict and identify patients on NIV who could eventually fail NIV trial and require invasive ventilation, Duan et al.[2] described the heart rate, acidosis, consciousness, oxygenation, respiratory rate (HACOR) score. This scale takes into account heart rate (H), acidosis- based on pH (A), consciousness- based on Glasgow Coma Scale (C), oxygenation (O), and respiratory rate (R), all of which are easily available at the bedside for consideration. In a test cohort of 449 patients with AHRF, the authors found that the failure rate with NIV was 47.8 and 39.4% in the test and validation cohorts. The authors concluded that patients with a HACOR score of more than 5 had a very high risk of NIV failure and would require early intubation to reduce hospital mortality.

Later on, Duan et al.[3] recruited 500 chronic obstructive pulmonary disease (COPD) patients in a derivation cohort to validate the HACOR scale in these patients to predict NIV failure. The HACOR score was collected at 1–2 h of NIV initiation in order to predict NIV failure. On analysis, the authors concluded that HACOR scores demonstrated good predictive power for NIV failure in patients with COPD, and predicted early NIV failure (in less than 48 h). High-risk patients who were identified with NIV failure were intubated early which eventually led to decreased hospital mortality.

Guia et al.[4] conducted a prospective, multicentric study in 128 patients admitted with COVID19 pneumonia and presented with AHRF and were initiated on continuous positive airway pressure (CPAP). HACOR score was calculated 1 hour after initiation of CPAP which was compared to the PaO2/FiO2 (P/F) ratio. A total of 35 patients (27.3%) failed CPAP and were intubated. The accuracy of the HACOR score for predicting CPAP failure on analysis of the data was found to be 82.03% when compared to PaO2/FiO2 which was 81.25%. The authors concluded that although the HACOR score could identify patients who would eventually fail CPAP, still the P/F ratio was a better predictor of failure.

In another study by Ding et al.,[5] the authors included 148 non-COPD patients with AHRF (sleep apnea-hypopnea syndrome-52, chronic thoracic sequelae-34, bronchiectasis- 31, chest wall deformity-14, obesity-hypoventilation syndrome-5, and miscellaneous-12). On analysis, the authors found that for 24 h from the time of NIV initiation, patients with a high HACOR score eventually failed the NIV trial. A total of 19 patients (13%) underwent tracheal intubation owing to NIV failure. The authors concluded that the HACOR score has high sensitivity and specificity (at 1-2h, the score of 5 with a sensitivity of 90% and a specificity of 85%, after 12h-4 with a sensitivity of 82% and a specificity of 91%, after 24h- 2 with a sensitivity of 100% and a specificity of 76%) for predicting NIV failure among non-COPD patients for acute-on-chronic respiratory failure with respiratory acidosis.

Later on, Magdy et al.[6] assessed the validity of HACOR score in AHRF patients who were initiated on high-flow nasal cannula (HFNC). Of the total 150 patients enrolled in this study, 100 (66.7%) had a successful treatment while 50 (33.3%) failed HFNC therapy. They found out that the patients with HFNC failure had a higher HACOR score at initiation and thereafter at 1, 12, 24, and 48 h, and required invasive ventilation. They concluded that a HACOR score of less than 6 after 1 h with HFNC correlated with less than 85% risk of failure.

HACOR scale appears to be a useful scoring system to predict failure of NIV and HFNC trials in patients with AHRF. Well-designed, adequately powered studies are necessary to establish its efficiency to identify the failure of non-invasive modalities in patients with AHRF.

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Conflicts of interest

There are no conflicts of interest.


1Chen Q, Liu M, Liu B, Li W, Gao D, Xie L, et al. Predictive factors for failure of noninvasive ventilation in adult intensive care unit: A retrospective clinical study. Can Respir J 2020;2020:1324348.
2Duan J, Han X, Bai L, Zhou L, Huang S. Assessment of heart rate, acidosis, consciousness, oxygenation, and respiratory rate to predict noninvasive ventilation failure in hypoxemic patients. Intensive Care Med 2017;43:192-9.
3Duan J, Wang S, Liu P, Han X, Tian Y, Gao F, et al. Early prediction of noninvasive ventilation failure in COPD patients: Derivation, internal validation, and external validation of a simple risk score. Ann Intensive Care 2019;9:108.
4Guia MF, Boléo-Tomé JP, Imitazione P, Polistina GE, Alves C, Ishikawa O, et al. Usefulness of the HACOR score in predicting success of CPAP in COVID-19-related hypoxemia. Respir Med 2021;187:106550.
5Ding M, Han X, Bai L, Huang S, Duan J. Impact of HACOR score on noninvasive ventilation failure in non-COPD patients with acute-on-chronic respiratory failure. Can Respir J 2021;2021:9960667.
6Magdy DM, Metwally A. The utility of HACOR score in predicting failure of high-flow nasal oxygen in acute hypoxemic respiratory failure. Adv Respir Med 2021;89:23-9.