Natl. J. Physiol. Pharm. Pharmacol. (2025), Vol. 15(1): 58–62

Research Article

10.5455/NJPPP.2025.v15.i1.10

A comparative study of peak expiratory flow rate between midozolam induced and propofol induced post anesthetic patients in recovery phase conducted at Government Hospital Chittoor- a district of South India

Seema Sankeshwari^1*, Ambuja Sambrani², Mahajabeen Madarkar³, Sangeeta Dhulappanavar Ravi⁴ and Devarapalli Srikanth⁵

¹Department of Physiology, Apollo Institute of Medical Sciences and Research, Chittoor India

²Department of Physiology, Karnataka Institute of Medical Sciences, Hubballi, India

³Department of Dermatology, S.R.Patil Medical College Hospital and Rsearch Center, Bilgi, India

⁴Resident Ochsner LSU Health, Monroe, LA

⁵B.Sc Anesthesia and Operation Theatre Technology, Department of Allied Health Sciences, The Apollo University, Chittoor, India

*Corresponding Author: Seema Sankeshwari. Department of Physiology, Apollo Institute of Medical Sciences and Research, Chittoor, India. Email: seemashridharsankeshwari [at] yahoo.com

Submitted: 19/10/2024 Accepted: 07/12/2024 Published: 31/01/2025

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Abstract

Background: Most airway obstruction, i.e., about 89% occurs during general anesthesia and 70% involve upper airway. Henceforth, choosing an appropriate choice of sedative to decrease respiratory morbidity during post anesthetic period is of utmost importance.

Aim: To analyze the peak expiratory flow rate (PEFR) in propofol and midazolam induced post anesthetic patients separately and compare.

Methods: This is a comparative study of measuring PEFR in post anesthetic patients between propofol-induced and midazolam-induced patients. A sample size of 30 was taken, among which 15 were propofol-induced and 15 were midazolam-induced subjects.

Results: Mean values of Avg PEFR readings of propofol and midazolam showed a p-value of 0.0001 which is statistically significant. Mean PEFR values of males and females in propofol induction showed a p-value of 0.0007 which is statistically significant. Mean PEFR values of males and females in midazolam induction showed a p-value of 0.0092 which is statistically significant.

Conclusion: Midazolam significantly depresses the respiratory system more than propofol. And females irrespective of the anesthetic drug used for induction showed low PEFR values as compared to males.

Keywords: Propofol, Midazolam, PEFR in anesthesia, Anesthesia in respiratory illness, Comparison between midazolam and propofol in sedation.

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Introduction

Airway obstruction during sedation can cause clinically significant adverse effects (Norton et al., 2006). Most of which involve the upper airways. Midazolam and propofol are the most commonly used sedatives for moderate sedation during a variety of medical procedures performed in INDIA. Henceforth, it becomes of utmost importance to choose the drug of choice for induction especially in people with pre-existing illness. One such variable to measure dynamic lung function is “Peak expiratory flow rate (PEFR)” also termed as PEFR.

PEFR values can reflect large airway flow which depends on various factors in healthy individuals such as gender, intra and extra thoracic diameters, ability of alveolar expansion, elastic recoiling ability of the lungs, voluntary efforts, and strength of the respiratory muscles. Therefore, PEFR values of the patients preoperative and postoperatively will reflect the effect of general anesthesia on lungs and respiration. The peak expiratory flow (PEF), other synonyms being PEFR and peak flow measurement, is a person’s maximum speed of expiration—as measured with a peak flow meter “a small hand-held device” used to monitor a person’s ability to breathe out air. It measures the airflow through the bronchi. PEF is typically measured in units of liters per minute (l/min) (Ji et al., 2021).

Now coming to the drugs par; Midazolam is a short-acting benzodiazepine, it is water soluble, non—irritating to veins, faster, and shorter acting (t_1/2–2 hours). Because of the short duration of action, midazolam is the only benzodiazepine suitable for the sedation of intubated and mechanically ventilated patients. It is being used frequently in critical care anesthesia (Tripathi, 2019). Based on the pharmaceutical literature available so far, benzodiazepines are known alveolar ventilation depressors there by decreasing respiratory drive leading to hypoxic drive. These effects can exaggerate the respiratory morbidity in patients with pre-existing respiratory illnesses such as COPD. Whereas, propofol is the most frequently used parenteral anesthetic. The induction dose of propofol in a healthy adult is 2–2.5 mg/kg. Reduced doses are recommended for the elderly and children. Studies have shown that an induction dose of propofol produces notable respiratory depression by decreasing tidal volume, respiratory rate, and sometimes minute ventilation. A deeper level of anesthesia can lead to a significant decrease in the functional residual capacity and increased lung clearance index, an index for ventilation distribution (von Ungern-Sternberg et al., 2007). Controversial to former statements few studies have also pointed out at Propofol’s mild Broncho-dilatory effect in patients with COPD (Miller, 2010; Laurence Bruton, 2011).

Most airway obstruction, i.e., about 89% occurs during general anaesthesia and 70% involve upper airway. There are no significant studies to show the comparison between Midazolam and Propofol induction effect on respiratory depression which can indirectly point to respiratory strength regain during post-anesthetic recovery period. Because both Midazolam and propofol are the most commonly used induction drugs—we aimed: after the results, will be able to suggest their appropriate application in induction for patients with pre-existing respiratory illnesses. Also, we can implicate this project’s results in choosing the right choice of drug in day-to-day anesthetic procedures, especially to COPD patients, where PEFR values play a vital role in depicting the dynamic lung function.

Aims and objectives of the study

Primary objectives: 1) to analyze the PEFR in midazolam-induced post-anesthetic patients. 2) to analyze the PEFR in propofol-induced post-anesthetic patients. 3) to compare the mean values of PEFR between Midazolam induced and propofol induced in the post-anesthetic patients. Secondary objective: To analyze the risk of respiratory obstruction and compare in post-anesthetic recovery of midazolam and propofol induction.

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Materials and Methods

This comparative study was conducted in the Apollo District Headquarters Hospital, Murukambattu, Chittoor-517001 Andhra Pradesh, India. Ethical clearance was taken prior to the proposal from the institute. Both male and female genders were included aged between 20 and 50 years were included. Subjects who were undergoing general anesthesia and whose respiratory examination was completely normal in pre anesthetic evaluation were included. Patients with Musculoskeletal anomalies, unstable vitals, and with history of repeated cardiorespiratory complaints were excluded.

The study was conducted in the Government hospital Chittoor with the help of the Anesthesia department to compare the PEFR between midazolam-induced, propofol-induced post-anesthetic patients. A total of 30 subjects who fulfilled the selection criteria and who were willing to participate were taken. All 30 subjects were explained about the procedure in their own vernacular language and written consent was obtained from them. This procedure was conducted 6 hours after post-anesthesia when the patient was conscious, alert, oriented to time place, and person, at least able to seat in sitting position and obey directions of the researcher to undergo the PEFR test.

PEFR values were measured using the device “mini-wright’s peak flow meter”, the procedure to measure PEFR is: insert the mouth piece into the meter and ensure the pointer is set at zero (l/Min). Ask the patient to hold the device without obstructing the holes of the instrument. In a sitting position ask the patient to take a deep breath and then blow as fast and hard the patient can (note- Tell the subjects to close both the nostrils while blowing) Note the value. Return the pointer to zero (l/Min) and repeat the procedure twice. An average of three readings will be noted. The dose of Midazolam used for induction is 3–4 mg. The dose of propofol used for induction is 100–130 mg. A total of 30 subjects were divided into two groups for comparison. Later, Statistical analysis was done by using SPSS Software. Statistical data was done using unpaired t test.

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Results

Abbreviations used-PEFR: Peak expiratory flow rate; AVG: Average SD: standard deviation; SEM: standard error of mean; Df: degree of freedom; N: number of samples; L/min: liter per minute (unit value pf PEFR); p value of less than 0.001 is taken as statistical significant (SS). On comparison of mean values of Avg PEFR readings of propofol and midazolam showed a p-value of 0.0001 which is statistically significant (Table 1, Fig. 1). Similarly when we look at the individual PEFR values of subjects (Fig. 2) there are consecutive dips in the readings of Midazolam-induced patients, line not crossing above the values of 320 l/minute, whereas when compared to individual readings of propofol PEFR values shows a constancy above 300 l/minute. On comparison between mean PEFR values of males and females in propofol induction showed a p-value of 0.0007 which is statistically significant (Tables 2, 3 and Figs. 3, 4) depicting females show considerably low PEFR values in general as compared to males irrespective of the drug of induction used.

Table 1. Comparing mean values of Avg PEFR readings of propofol and midazolam.

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Discussion

Norton et al. (2006) conducted a study to observe “Differences between Midazolam and Propofol Sedation on Upper Airway Collapsibility Using Dynamic Negative Airway Pressure”. After attaining equivalent sedation, they concluded that at the mild to moderate level of sedation studied, midazolam and propofol sedation resulted in the same propensity for UAO. However, when comparing the findings of this study; our study showed significantly decreased PEFR values in females as compared to males irrespective of either of the anesthetic used, i.e., for both propofol and midazolam showed statistically significant values of p-value less than 0.001. This may be attributed to individual physical factors such as body mass index, body surface, voluntary efforts of the individual, muscle strength as compared to females, and anatomical variation in thorax between the genders. Montravers et al. (1992) conducted a study on “EFFECTS OF I.V. MIDAZOLAM ON UPPER AIRWAY RESISTANCE”. Supraglottic pressures were measured using a balloon-tipped catheter and air flow with a pneumotachograph. Even though the method of analyzing the respiratory function was different from our method, their finding of being midazolam a potent respiratory depressor remained the same. They believed that the observed increase in upper airway resistance midazolam induction resulted from diminished pharyngeal muscle tone. Hence, the results of the current study, i.e., midazolam depresses the respiratory system more than that of propofol can be attributed to one of their mentioned causes. Molliex et al. (1993) in their study of “Effects of Midazolam on respiratory muscles on humans” have mentioned- there were no significant dynamic lung function changes observed in healthy volunteers except a slight increase in large airway resistance during sleep. Liu et al. (2017) in their study of “Effects of Propofol on Respiratory Drive and Patient-ventilator Synchrony during Pressure Support Ventilation in Postoperative Patients: A Prospective Study” got the following results: Increasing the depth of sedation reduced the peak, and decrease in respiratory drive, decrease in Minute ventilation and inspiratory cycle while tidal volume remained unchanged. This study supports the findings of our study where PEFR readings after propofol induction were not as severe as compared to midazolam induction.

Fig. 1. Comparing mean values of average PEFR readings of propofol and midazolam.

Fig. 2. Comparing individual variations PEFR values between propofol and midazolam.

Table 2. Comparison between mean PEFR values of males and females in propofol induction.

Table 3. Comparison between mean PEFR values of males and females in midazolam induction.

Fig. 3. Comparison between mean PEFR values of males and females in propofol induction.

Fig. 4. Comparison between mean PEFR values of males and females in midazolam induction.

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Conclusion

Based on the above results study concludes that; midazolam significantly delays the recovery of respiratory muscles as it depresses the respiratory system more than propofol. Henceforth, propofol can be taken as a first-line drug in patients suffering from pre-existing respiratory illnesses or COPD especially those who are suffering from asthma since PEFR is considered to be a very specific and sensitive parameter to assess respiratory function in asthmatic individuals. The current study also suggests doses of propofol, as well as midazolam, should be strictly monitored while giving to female patients since PEFR values of females were low in both the groups irrespective of the induction drug used in this study. This study also implicates and motivates other medical folks to undertake more studies with commonly used drugs to decrease respiratory morbidity in post-anesthetic period, especially using dynamic lung function tests.

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Acknowledgment

None.

Conflict of interest

The author reports that there is no conflict of Interest.

Funding

None.

Ethics approval

Not applicable.

Data availability

The author does not have permission to share data.

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