Occurrence of hypoxia in the wards of a teaching hospital.

OBJECTIVE: Appearance of hypoxia in a patient may be an indicator of a serious medical condition that can have grave consequences. Clinical evaluation fails to detect majority of the patients of hypoxia, and therefore, it may remain unnoticed in the wards. We planned to assess the magnitude of hypoxia in different wards of our tertiary care hospital.
MATERIALS AND METHODS: We studied all the patients admitted in various medical and surgical wards during 1 week of study. Oxygen saturation (SpO(2)) was measured with the help of a pulse oximeter in all the patients who remained admitted for at least 24 h. Hypoxia was diagnosed in a patient when he had SpO(2) less than 90%.
RESULTS: During the study period, 1167 patients were admitted in various wards of the hospital. Hypoxia was detected in 121 patients (10.36%). Among them, 7 (0.59%) patients were already having a diagnosis of respiratory failure, but were not on oxygen therapy while 5 (0.42%) patients were having SpO(2) less than 90% despite of oxygen therapy. In 109 (9.34%) patients, hypoxia was detected incidentally.
CONCLUSION: Unnoticed hypoxia was detected in a significant number of the patients admitted in the wards of the hospital. Therefore, it is concluded that oxygen saturation measurements should be included with other vital parameters like pulse, temperature, and blood pressure, in the monitoring chart of all the admitted patients.

INTRODUCTION

Hypoxia may indicate presence of critical conditions where immediate oxygen therapy is required. Oxygen therapy is essential in clinical states of respiratory failure such as pneumonia, severe asthma, chronic bronchitis, myocardial infarction, and postoperative states.[1-3] Unnoticed hypoxia has been reported in admitted patients in many studies.[1-3] In various rural hospitals in the Papua New Guinea, 10% to 40% children had oxygen saturation less than 90%.[4] Similarly, 20% patients in post-anesthetic recovery room had hypoxia after intravenous sedation given for maxillofacial surgery.[5]

In care of the patients, oxygen is still prescribed on the basis of clinical evaluation in majority of the hospitals. It may not be an accurate and reliable method. Though oximetry is available in some wards, it remains underutilized. We planned this study to assess the magnitude of unnoticed hypoxia in the patients admitted in the wards of our tertiary care hospital with the help of pulse oximetry.

MATERIALS AND METHODS

All the patients admitted for more than 24 h in various medical and surgical wards including intensive care units were studied. After obtaining an informed consent, the diagnosis and demographic data such as name, age, sex, and smoking history were noted from bedside ticket. Pulse and oxygen saturation were recorded. If the finger had nail paint, it was removed with the help of spirit.

Oxygen saturation (SpO2) was measured with a pulse oximeter (PALCO)[6] for 1 min. The pulse oximeters are pre-calibrated against direct measurements of arterial blood oxygen saturation (SpO2) in volunteers. Resulting calibration algorithm is stored in a digital microprocessor within the pulse oximeter. During subsequent use, the calibration curve is used to generate the oximeter estimate of SpO2.

SpO2 reading less than 90% was taken as a warning sign of impending hypoxia and respiratory failure. Whenever hypoxia was detected in a patient, it was reported to the respective ward doctors so that they could add O2 inhalation in the treatment.

RESULTS

In this study, a total of 1,167 patients were evaluated. Out of them, 867 were males and 300 were females. Of all the patients, 121 (10.36%) were found to be having SpO 2 less than 90% [Figure 1]. Among 121 patients of hypoxia, 35 (28.29%) were females and 86 (71.71%) were males. In patients with normal oxygen saturation, 265 (25.33%) were females and 781 (74.66%) were males. Thirty two (26.44%) of all the hypoxic patients were smokers while 89 (73.56%) were non-smokers.

Figure 1

Distribution of oxygen saturation among patients

Hypoxia was also noted in 12 patients who already had the diagnosis of respiratory failure [Figure 1]. Among them, 7 (0.59%) were already diagnosed as having respiratory failure, but still were not on oxygen therapy, and 5 patients (0.42%) were hypoxic despite of being on oxygen therapy. Thus, in 109 (9.34%) patients, previously unnoticed hypoxia was seen.

Tachycardia was more consistently (42.14%) found in the patients of hypoxia as compared to those with normal oxygen saturation (25.05%) [Figure 2].

Figure 2

Distribution of subjects with hypoxia and with normal oxygen saturation according to pulse rate

Maximum number of the patients with unnoticed hypoxia was found in general medicine wards [Table 1]. Such patients were also observed in all wards of the hospital including surgical wards. In general medicine wards, stroke (18.18%) was the most common diagnosis among the patients of hypoxia while in general surgery ward, it was gut perforation (15.78%). In other medical wards, it was end-stage renal disease (35.71%) while in other surgical wards, it was head injury (17.30%). In medical ICU, none of the patients had hypoxia.

Table 1

Distribution of hypoxia in various wards of the hospital

DISCUSSION

Undiagnosed hypoxia may prove fatal. Successful treatment of tissue hypoxia requires early recognition. The diagnosis of hypoxia is often difficult and is delayed because the clinical features are non-specific and may be related to the underlying conditions. Symptoms of hypoxia such as altered mental state, cyanosis, dyspnea, tachypnea or hypoventilation, arrhythmias, peripheral vasodilatation, systemic hypotension, nausea, vomiting, gastrointestinal disturbances, and coma are not confirmatory.[7]

Pulse oximeter is a reasonably good indicator of oxygenation status of the patient although it has its limitations in low cardiac output states, anemia, and carbon-dioxide retention.[7] Despite this, pulse oximeter should be used even as a portable device in the wards to screen the patients of unnoticed respiratory failure. In this study, 10.36% of the total patients admitted in the hospital had hypoxia. In previous studies[458] carried out in various hospitals, 7.8% to 40% of the study subjects had hypoxia. In medical wards, the most common diagnosis among the patients of hypoxia was stroke in our study. In an earlier study,[9] nocturnal hypoxia was found to be very common in the patients of stroke, and even nocturnal oxygen therapy was suggested for them.

Importantly, in a country like India where the doctor-to patient or nurse-to-patient ratio is very low, continuous monitoring of every patient is not possible. A handy device like pulse oximeter may prove beneficial in early recognition of a previously undiagnosed hypoxia. In our study, 92.08% of the total hypoxic patients were diagnosed for the first time. In an earlier study at Riyadh,[10] only 1.55% of the patients were found to have unnoticed hypoxia. Better health, staff-to-patient ratio, and consequently better monitoring may explain lower occurrence of hypoxia in their study.

Moreover, contrary to the common belief that respiratory failure is a problem of medical wards, it was found that sizeable numbers of such patients in our study were seen in all wards of the hospital, including surgical wards. Therefore, monitoring of the patients in these wards should also include pulse oximetry. By an early recognition, this major group of the patients can be saved from serious consequences of hypoxia i.e. cardiac and respiratory arrest, hypotension, and metabolic acidosis.[6]

CONCLUSION

Hypoxia should be detected at an early stage so as to prevent serious consequences. Pulse oximeter is a simple, non-invasive, and reliable method to detect it and also for proper monitoring of oxygen therapy after diagnosis of hypoxia. Therefore, it should be included in the daily monitoring chart of all the admitted patients.