Preinduction incentive spirometry versus deep breathing to improve apnea tolerance during induction of anesthesia in patients of abdominal sepsis: A randomized trialM Tripathi1, A Subedi2, A Raimajhi2, K Pokharel2, M Pandey3
1 Department of Anaesthesiology and Critical Care, BP Koirala Institute of Health Sciences, Dharan, Nepal; Department of Anaesthesiology, SGPG Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
2 Department of Anaesthesiology and Critical Care, BP Koirala Institute of Health Sciences, Dharan, Nepal
3 Department of Anaesthesiology, SGPG Institute of Medical Sciences, Lucknow, Uttar Pradesh, India
Correspondence Address: Source of Support: Institutional funding for the research project, Conflict of Interest: None DOI: 10.4103/0022-3859.123154
Source of Support: Institutional funding for the research project, Conflict of Interest: None
Background: Abdominal sepsis is associated with varied degree of hypoxemia and atelactasis in the lung and can enhance the onset of desaturation of arterial blood during apnea. Aims : This study looked at methods to improve safety margin of apnea during induction of anesthesia in these high-risk patients. Settings and Design: It was a randomized, single blind study on adult patients presenting for emergency laparotomy due to peritonitis in a university teaching hospital setting. Materials and Methods: In group 1 (IS) (n = 32), three sessions of incentive spirometry (IS) were performed within one hour before induction of anesthesia. In group 2 (DB) (n = 34), patients were subjected to deep breathing sessions in a similar manner. All patients received preoxygenation (100%) by mask for 3 min, followed by rapid-sequence induction of anesthesia using fentanyl, thiopental, and suxamethonium and endotracheal intubation. Patients were subjected to a period of apnea by keeping the end of the endotracheal tube open to air till they developed 95% hemoglobin saturation (SpO 2 ) by pulse oxymetry. Positive pressure ventilation was resumed at the end. We observed for hemodynamic changes, apnea time, and SpO 2 (100%) recovery time on resuming ventilation. Arterial blood gas samples were taken before intervention, after IS or DB, after preoxygenation, and at the end of apnea. Statistical analysis used: One-way analysis of variance (ANOVA), X 2 test, Kaplan-Meier graph, and log-rank tests were applied to compare the two study groups. Results: Oxygenation level in group 1 (265 ± 76.7 mmHg) patients was significantly (P < 0.001) higher than in group 2 (221 ± 61.8 mmHg)at the end of preoxygenation. The apnea time (median: lower bound - upper bound Confidence Interval apnea time) (272:240-279 s) in group 1 (IS) patients was significantly higher P < 0.05) than in group 2 (180:163-209 s) patients. Saturation recovery time (35:34-46 s) in group 1 (IS) patients was also quicker than in group 2 patients (48:44-58 s). Conclusions: IS in the preoperative period is superior to deep breathing sessions for improving apnea tolerance during induction of anesthesia in abdominal sepsis patients.
Keywords: Abdominal sepsis, anesthesia induction, apnea, hypoxemia, incentive spirometry, preoxygenation
Patient with abdominal sepsis frequently undergo emergency laparotomy under general anesthesia. These patients are prone to develop basal atelectasis of the lungs due to splinting effect of tense and distended abdomen, and this can progress to acute respiratory distress syndrome associated with varied degree of hypoxemia. , Atelectasis results in a decrease in functional residual capacity (FRC) with subsequent reduction in oxygen reserve and an increase in intra-pulmonary shunting.  Quick onset of atelactasis has also been documented during the induction of anesthesia, leading to mild-to-moderate hypoxemia (SpO 2 from 85% to 90%) in nearly half of the anesthetized patients during elective surgery. , Maneuvers such as preoxygenation with 100% oxygen for 3 min and vital capacity breathing have been described to improve apnea tolerance during induction of anesthesia and intubation.  These methods have shown varied degree of improvement in apnea tolerance in young and healthy and elderly groups of patients. , Continuous positive airway pressure (CPAP) or positive end expiratory pressure (PEEP) has also been shown to improve atelactasis, and hence the oxygenation and improved margin of safety during induction apnea.  Deep breathing during incentive spirometry (IS) is associated with alveolar recruitment to resolve atelectasis and pulmonary complications in postoperative period.  We hypothesized that preinduction incentive spirometry would improve arterial oxygenation and prolong the safe period of apnea. The present study aimed to compare the effects of incentive spirometry with deep breathing exercises on apnea tolerance in patients of acute peritonitis presenting for exploratory laparotomy under general anesthesia.
This prospective, single-blind, randomized, controlled clinical study was conducted in a university teaching hospital between October 2009 and July 2010. The study was funded by the Institutes Research Committee and approval was obtained from the Ethics Committee of the Institute for Human Studies. Written and informed consent was also obtained from all patients.
The sample size was calculated on the basis of reported onset time (mean ±SD = 315 ± 69.5 s) of desaturation to 95% after 3 min preoxygenation,  and an assumption that prolongation of the onset of time of desaturation by 60 s is a clinically significant improvement by the compared interventions. The a priori computed sample size was calculated using t-test for difference between two independent means at α-error of 0.05 and 1-β error of 90%. The required number of patients was 34 in each group. After explaining the procedure and the nature of study, written informed consent was taken from all 70 patients included in the study. We included patients who were admitted in the emergency room with peritonitis due to various abdominal causes. Patients younger than 14 years or older than 60 years, suffering from obesity (body mass index >27 kg/m 2 ), with cognitive impairments, or an uncooperative patient toward the IS, a preexisting lung disease (COPD, asthma), ischemic heart disease, upper airway obstruction, mean arterial blood pressure (MAP) <60 mmHg, chest X-ray with pleural effusion or bilateral diffuse lung infiltrates, PaO 2 <60 mmHg, hypercapnia (PaCO 2 >45 mmHg) and severe acidosis (pH < 7.2), American Society of Anesthesiologists status-V, anticipated difficult mask ventilation and intubation, or hemoglobin concentration (<10g/dl) were excluded from the study.
The patients were randomly assigned to two study groups of 35 patients each by a sealed envelope technique. Patients in group 1 had preoperative intervention by incentive spirometry (IS) and those in group 2 by vital capacity deep breathing (DB). In the preoperative holding area, IS was performed in the group 1 patients using a flow-oriented incentive spirometer (Tri-Ball, Romsons Ltd., Delhi, India), which has three chambers containing balls. The balls are raised in their respective chambers on the generation of three different rates of inspiratory flow rates (600, 900, and 1200 mL/s) by patients breathing through the mouthpiece. All patients were explained about the use of IS by the doctors. After a quiet expiration, they were encouraged to take maximal inspirations through the mouthpiece of the device and to hold each breath for as long as possible. Corresponding to inspiratory flow, the balls were lifted and kept suspended by the sustained inspiratory flow. The balls served as a visible feedback of the generation of the inspiratory flow to lift them inside the chambers. The patients were encouraged to use the device for 5-10 breaths per session, , for three sessions within an hour of preinduction of anesthesia. Similarly, patients in group 2 were asked to take 5-10 deep breaths (vital breathing) for at least three sessions in the preoperative holding area within an hour before inducing anesthesia.
In the operation theater, all the patients were preoxygenated by traditional preoxygenation technique of 3 min of tidal volume breathing using a 100% oxygen flow of 5 l/min followed by a rapid-sequence induction of anesthesia using fentanyl (1.5 μg/kg body weight) and thiopental (3-5 mg/kg) titrated till loss of eye-lash reflex. Suxamethonium (1.5 mg/kg) was used for muscle relaxation. Face-mask oxygenation was continued until apnea occurred; thereafter, the trachea was intubated and the proximal end of the tube was left open to room air to judge apnea tolerance. Study endpoint was at the desaturation (SpO 2 -95%) of hemoglobin by pulse oxymetry. Ventilation was started with 100% oxygen at the end of apnea.
Peripheral oxygen saturation was monitored via a finger probe (HPM 1190A, Hewlett Packard, Boeblingen, Germany). A radial artery was percutaneously cannulated in the preoperative holding area under local anesthesia. Arterial blood gas analysis was performed using calibrated automated blood gas analyzer (ABL India, Ltd.). The arterial blood samples in a pre-heparized syringe were obtained at four study points - before the therapeutic intervention of either IS or deep breathing, at the end of last session of breathing intervention, at the end of preoxygenation, and then at the end of apnea point.
We observed for hemodynamic parameters, Sp0 2 , and arterial blood gas parameters at different study points as stated above. We observed for the SpO 2 (100%) recovery time by pulse oximetry as a secondary end point of study to see the response of ventilation. We also noted any side effect during the study period.
Statistical Analysis; All data were entered in Microsoft Excel worksheet and then into statistical package (SPSS-15 for Windows, SPSS Inc., Chicago, IL, USA) for data analysis. The physical characteristics of the two study groups and the mean value of different studied data were analyzed using one-way analysis of variance (ANOVA) test. We also compared the median value of apnea time and saturation recovery time by the Box-plot method and X 2 test for the proportions. Time to desaturation (safe apnea time) was compared in the two groups using Kaplan - Meier graph and the log-rank test. For this, the end of 300 s (5 min) was considered the end point to censor the patients in the two study groups. At 95% confidence a calculated value of P < 0.05 was considered a statistically significant difference. No adjustments were made for multiple comparisons.
Patients included in the study groups were similar in terms of age, gender distribution, body weights, heights, and body surface area. Patients included in the study were operated for appendicitis (24), duodenal perforation (16), acute intestinal obstruction (18), and strangulated hernia (12). Lung injury (PaO 2 /FiO 2 ratio), arterial blood pH, and arterial carbon dioxide (PaCO 2 ) levels were also similar in both the study groups [Table 1]. Two patients in group 1 (IS) were excluded as they could not generate sufficient effort to lift even one ball and one patient was excluded in group 2 (DB) as the arterial blood gas analysis samples collected could not be analyzed due to clotting.
Oxygenation parameters did not improve significantly either after IS or after DB. However, arterial blood oxygenation improved significantly (P < 0.001) during preoxygenation in both the study groups. The increase in PaO 2 levels (265 + 76.7 mmHg) in group 1 than in group 2 (221 + 61.8 mmHg) was statistically significant (P < 0.05) at the end of preoxygenation. However, it decreased significantly (P < 0.001) in both the study groups at the end of apnea [Table 2] and [Figure 1].
Hemodynamically, patients were stable and showed similar changes in both the study groups throughout the preoxygenation period but developed significant (P < 0.05) tachycardia (group 1 - 112 + 10.5 bpm versus group 2 - 117 + 11.7 bpm) and systolic hypertension (group 1-131+18.2 mmHg versus group 2-133+16.7 mmHg) at the end of apnea in both the groups. Heart rate settled down significantly (P < 0.05) in group 1 (90 + 13.3) patients during preoxygenation than in the group 2 (97 + 10.2) patients [Table 2].
Although patients in both the study groups attained 100% SpO 2 levels, the safety margin of apnea improved significantly (P < 0.05) in terms of higher arterial blood oxygen levels in group 1 (265+76.7 mmHg) than in group 2 (221 + 61.8 mmHg) patients. Alveolar arterial oxygen difference (A-aDpO 2 ) was significantly lower in group 1 (IS) (68+42.5 mmHg) patients than in group 2 (DB) (113+35.6 mmHg) suggesting better alveolar ventilation. PaCO 2 showed similar changes in both the study groups at all study points and patients of both the groups developed significant hypercarbia (group 1 - 59 + 4.1 mmHg versus group 2 - 56 + 7.6 mmHg) at the end of apnea [Table 3].
The safety margin of apnea also improved significantly (P < 0.001) in terms of apnea time in group 1 (259 ± 53.9 s) than in group 2 (186 ± 64.53 s) patients [Table 4]. Kaplan-Meier analysis and Log-rank test also showed a significant (P<0.001) difference between the two study groups and 11/32 (34%) patients were censored in group 1 with apnea time >300 s or 5 min and 3/34 (9%) patients in group 2 [Figure 2].
We also observed that the saturation (SpO 2 -100%) recovery time on resuming ventilation with 100% oxygen at the end of apnea time was significantly (P < 0.05) quicker in group 1 (40 ± 16.81 s) than in group 2 (51 ±2 0.3 s) patients [Table 4] [Figure 3]. Even after resuming ventilation with 100% oxygen, patients in both the groups developed a significant desaturation (<90%) before returning to 100%. Incidences of various cardiac side effects in the patients of the two study group are listed in [Table 4].
Patients presenting for emergency laparotomy showed lesser values for mild ARDS (PaO 2 /FiO 2 ) than normal and probably had lung injury.  Incentive spirometry performed preoperatively improved arterial blood oxygen levels and the Pao 2 /FiO 2 values after 3 min preoxygenation more than the voluntary deep breathing. There was a significant increase in apnea time before significant desaturation (95%) and 33% patients tolerated apnea time of 300 s or 5 min among the patients of IS intervention. The SpO 2 (100%) recovery time was also significantly quicker in patients subjected to IS intervention. We also observed a similar degree of hypoxemia, hypercarbia, and tachycardia at the termination of the apnea. On resuming ventilation, quicker recovery time to SpO 2 (100%) was observed in the IS group than the DB group patients.
Clowes et al. have shown by clinical and experimental observations that respiratory insufficiency sets in after the onset of non-thoracic sepsis. , In early phases, usually there are clear fields in the chest X-ray, but hypoxemia is present due to pulmonary shunt. ,, The respiratory changes in these patients are characterized by focal alveolar collapse, septal edema, vascular congestion, and intravascular shunt.  In emergency, sepsis is reported to be present in 91% patients who had pulmonary failure and required respiratory support, and of all patients who became septic, 42% had serious respiratory problems.  Since the patients included in the study were from emergency having abdominal sepsis due to various intra-abdominal septic conditions, they had a similar degree of respiratory failure as suggested by the decreased PaO 2 /FiO 2 ratio and was probably related to focal lung atelectasis.
Induction of anesthesia is also characterized by development of lung atelectasis and diminished margin of safety for hypoxemia during apnea. , Patients for elective surgery are reported to develop desaturation (95%) by SpO 2 around 5 min.  Our patients could tolerate apnea for similar desaturation levels well below this time interval after classical preoxygenation and again suggested early-onset lung injury in our patients due to septic pathology in emergency patients.
Deep lung insufflations improve lung compliance and partial pressure of oxygen (PaO 2 ).  Several methods have been studied, such as intermittent positive pressure ventilation, exercises with deep breathing, incentives spirometry, and conventional chest physiotherapy; nevertheless, a meta-analysis confirmed that all the studied protocols and methods were equally effective in reducing the frequency of pulmonary complications after upper abdominal surgery.  Prophylactic use of IS has reduced the incidence of respiratory complications after upper abdominal surgery.  We observed that the IS and DB per se did not improve arterial blood oxygen levels probably due to arterio-venous shunting in early ALI. However, oxygen-enriched inhalation significantly improved arterial oxygen levels and reduced alveolar-arterial difference in oxygen levels, suggesting better ventilated lung zones after IS where patients generated a high inspiratory air flow rate (>900 l/min) at least. The incentive spirometer encourages a patient, through a visual feedback, to maintain a maximum inspiratory flow rate to lift the balls inside the chamber. It has been one of the most commonly used strategies to reduce postoperative respiratory complications.  It also helps to improve the safety margin of apnea during induction of anesthesia in emergency patients.
Greater shunting in septic patients leads to the argument that more nonventilated or poorly ventilated alveoli are being perfused in postshock patients.  This concept, in addition to greater noncompliance, indicates that focal alveolar collapse and interstitial edema are principally responsible for these changes that appear to be significantly greater in sepsis, even more so if broncho-pneumonia is present. Probably, normal recruitment of pulmonary capillaries, as cardiac output increases, is accomplished by overcoming the critical closing pressure. It appears that edema and other factors may be responsible for a reduction of functional residual capacity and for a greater critical closing pressure in the lungs of septic patients, leading to greater pulmonary arterial pressures and perfusion pressure gradients found in sepsis.  At the same time, as alveoli are reexpanded, the resistance to blood flow in the capillaries around them appears to be reduced. In both the postshock and septic states, as PIP and pulmonary shunt were reduced, the pulmonary artery pressure and gradient of pressure to the left atrium declined.  We observed that IS improved significantly the alveolar-arterial partial pressure oxygen difference, suggesting that IS improved lung recruitment significantly more than the voluntary deep breathing sessions in similar conditions of patients.
Failing improvement of shunting, positive end-expiratory pressure (PEEP) is of value in reduction of alveolar collapse and restoration of a more normal ventilation perfusion ratio.  Venous return may be reduced and pulmonary capillary resistance may rise accompanied by a fall in cardiac output if excessive PEEP is employed.  Without monitoring pulmonary hemodynamics and cardiac output, PEEP in excess of 15 cmH 2 0 should not be employed.  Furthermore, its use is risky in emergency patients where gastric emptying is doubtful.
It was also interesting to note the quicker saturation recovery time in patients subjected to IS in the preoperative period. It further supported the theory that the number of aerated lung units improved significantly after incentive spirometry than after deep breathing. We also noticed that at the end of desaturation, a significant desaturation continued even after resuming ventilation with 100% oxygen and patients developed side effects such as tachycardia, cardiac arrhythmia, and hypertension in both the study groups probably related to hypoxemia and hypercarbia that developed during apnea. The limitation of the study remains that the study could not be double blinded. The IS also depends on the understanding and the effort of the patient who must lift at least two balls.
In conclusion, the use of IS in the preoperative period among patients who are at high risk for respiratory failure improves the safety margin of apnea during induction of rapid-sequence general anesthesia in emergency settings.
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4]