Respiratory Compromise is Common, Costly, and Deadly

Respiratory compromise—which includes respiratory insufficiency, arrest and failure—is a critical perioperative complication associated with increased costs and poor outcomes.

  • Current monitoring strategies for the early identification of postoperative respiratory compromise may be inadequate.
  • A comprehensive and continuous patient monitoring strategy encompassing respiratory rate, pulse oximetry and capnography has the potential to reduce the incidence and severity of postoperative respiratory compromise, and improve patient outcomes and reduce the cost of care.
  • A 2010 AHRQ statistical brief lists respiratory insufficiency, arrest and failure (RIAF) as one of the five conditions resulting in the most rapidly increasing hospital costs for Medicare-covered stays in the U.S.[1] In 2007, respiratory insufficiency, arrest and failure were related to 385,800 inpatient stays costing $7.7 billion.[1]
  • Inpatients with RIAF originating on the general care floor had higher mortality rates (34.6%) than non-RIAF cases (1.2%) and longer lengths of hospital and ICU stays (11.5, 5.8 days) than non-RIAF cases (4.1, 2.9 days).[2]
  • Postoperative respiratory failure has become a hospital focus under Medicare’s Inpatient Quality Reporting Program (Patient Safety Indicator #11).[3] Current monitoring regimens may be inadequate for preventing respiratory compromise and other adverse events.
  • Approximately 77% of patients suffering adverse events have at least one vital sign immediately before the event missing from documentation.[4]
  • Delayed interventions occur in 50% of patients with respiratory distress, with a median duration of delay of 12 hours.[5] Adverse events are frequently preceded by respiratory abnormalities.
  • Respiratory abnormalities are the most common abnormalities prior to ICU admission.[6]
  • Bradypnea on the general care floor is independently associated with a high risk for subsequent death.[7]


Continuous monitoring of respiratory function provides notification to the medical professional of conditions which may, if unaddressed, lead to adverse events.

  • The Anesthesia Patient Safety Foundation recommends that healthcare professionals “consider the potential safety value of continuous monitoring of oxygenation (pulse oximetry) and ventilation in patients receiving PCA or neuraxial opioids in the postoperative period.”[8]
  • In patients undergoing patient-controlled analgesia, continuous oximetry and capnography monitoring reveal frequent desaturation and bradypnea.[9]
  • Continuous monitoring with pulse oximetry provides early detection of physiological decline, which has been shown to reduce rescue events and ICU transfers.[10]
 

Key Resources:

References:

1. Wier LM, Henke R, Friedman B. Diagnostic Groups with Rapidly Increasing Costs, by Payer, 2001-2007: Statistical Brief #91. Healthcare Cost and Utilization Project (HCUP) Statistical Briefs. Rockville MD2010. [ View Abstract ]

2. Kelley SA, Agarwal S, Parikh N, Erslon M, Morris P. Respiratory insufficiency, arrest and failure among medical patients on the general care floor. Crit Care Med. 2012;40(12):764. [ View Abstract ]

3. Zhan C, Miller MR. Excess length of stay, charges, and mortality attributable to medical injuries during hospitalization. JAMA. 2003;290(14):1868-1874. [ View Abstract ]

4. Chen J, Hillman K, Bellomo R, Flabouris A, Finfer S, Cretikos M. The impact of introducing medical emergency team system on the documentations of vital signs. Resuscitation. 2009;80(1):35-43.
[ View Abstract ]

5. Quach JL, Downey AW, Haase M, Haase-Fielitz A, Jones D, Bellomo R. Characteristics and outcomes of patients receiving a medical emergency team review for respiratory distress or hypotension. J Crit Care. 2008;23(3):325-331. [ View Abstract ]

6. Peberdy MA, Ornato JP, Larkin GL, et al. Survival from in-hospital cardiac arrest during nights and weekends. JAMA. 2008;299(7):785-792. [ View Abstract ]

7. Buist M, Bernard S, Nguyen TV, Moore G, Anderson J. Association between clinically abnormal observations and subsequent in-hospital mortality: a prospective study. Resuscitation. 2004;62(2):137-141. [ View Abstract ]

8. Weingarten TN, Kor DJ, Gali B, Sprung J. Predicting postoperative pulmonary complications in high-risk populations. Curr Opin Anaesthesiol. 2013;26(2):116-125. [ View Abstract ]

9. Overdyk FJ, Carter R, Maddox RR, Callura J, Herrin AE, Henriquez C. Continuous oximetry/capnometry monitoring reveals frequent desaturation and bradypnea during patient-controlled analgesia. Anesth Analg. 2007;105(2):412-418. [ View Abstract ]

10. Taenzer AH, Pyke JB, McGrath SP, Blike GT. Impact of pulse oximetry surveillance on rescue events and intensive care unit transfers: a before-and-after concurrence study. Anesthesiology. 2010;112(2):282-287. [ View Abstract ]


Incidence

The incidence of respiratory compromise is influenced by definition and criteria. The table below summarizes the literature investigating the incidence of respiratory compromise across multiple definitions and criteria.

Please use the buttons below to show which citations you would like to see:

Citation

Outcome

Outcome Definition

Inclusion Criteria

N

Incidence

Grosse-Sundrup 20121

Respiratory depression

SpO2 < 90

Burn, gynecology, neurosurgery, urology, cardiac, general, oral/maxillofacial, orthopedic, pediatric, plastic, thoracic, transplant, trauma and vascular, and oncology surgical patients

18,579

5.00%

Bloom 20102

Respiratory depression

Naloxone administration

Intra-abdominal surgical patients

809,340

3.70%

Cashman 20043

Respiratory depression

RR < 8-10 BPM

Abdominal, major gynecology, major orthopedic, thoracic surgical patients

29,607

1.10%

Cashman 20043

Respiratory depression

SpO2 < 90

Abdominal, major gynecology, major orthopedic, thoracic surgical patients

1,516

17%

Cashman 20043

Respiratory depression

PACO2 > 6.5 kPa or 50 mm Hg

Abdominal, major gynecology, major orthopedic, thoracic surgical patients

3,170

3.30%

Cashman 20043

Respiratory depression

Naloxone administration

Abdominal, major gynecology, major orthopedic, thoracic surgical patients

55,404

0.30%

Shapiro 20054

Respiratory depression

RR of < 10 BPM

All post-op patients

1,524

1.20%

Filsberg 20035

Respiratory depression

RR < 8 BPM

Post-op patients receiving acute pain service

1,026

1.26%

Filsberg 20035

Respiratory depression

RR < 8 BPM

Post-op patients receiving acute pain service

1,670

0.40%

Gupta 20126

Respiratory failure

Unplanned intubation during surgery or postoperatively, reintubation once extubated or mechanical ventilation for more than 48 hours postoperatively. (NSQIP definition)

Anorectal, aortic, bariatric, brain, breast, cardiac, ENT, GBAAS, FG/HPB, hernia, intestine, neck, nonesophageal thoracic, OB/GYN, orthopedic, other abdomen, peripheral vascular, skin, spine, urology, vein surgical patients

468,795

3.10%

Johnson 20077

Respiratory failure

Postoperative mechanical ventilation for longer than 48 hours or unanticipated reintubation.

Vascular and general surgical patients

180,359

3.00%

Fischer 20138

Respiratory failure

Unanticipated intubation during the postoperative period, or failure to wean from mechanical ventilation in 48 hours.

Complex abdominal wall reconstruction surgical patients

1,706

6%

Bloom 20119

Respiratory failure

ICD-9-CM codes associated with respiratory failure

Adult post-op inpatients

197,216

2.40%

Linde-Zwirble 201010

Respiratory failure

ICD-9-CM codes associated with respiratory failure

Elective surgical patients

738,039

1.70%

Arozullah 200311

Respiratory failure

Greater than 48 hours of ventilator assistance or postoperative reintubation

Upper abdominal, thoracic, Peripheral vascular, abdominal aortic aneurysm repair, neck, neurosurgery, other

103,176

0.29%

Agarwal 201112

RIAF

ICD-9-CM codes associated with RIAF

Inpatient adults receiving parenteral opioids

150,284

2.80%

Kelley 201213

RIAF

ICD-9-CM codes associated with RIAF

Open or laparoscopic appendectomy, cholecystectomy, Colectomy and Roux-en-Y gastric bypass surgical patients

94,154

2.60%

Grosse-Sundrup 20121

Unplanned intubation

Reintubation after surgery in the post-anesthesia care unit, on the surgical floor or on the ICU

All surgical patients receiving intraoperative neuromuscular blockade

18,579

0.80%

Ramachandran 201114

Unplanned intubation

Unanticipated early post-op intubation

Nonemergent, noncardiac surgical patients

222,094

0.83%

Brueckmann 201315

Unplanned intubation

Reintubation in the hospital after primary extubation in the operating room, leading to unplanned mechanical ventilation within the first three postoperative days.

Burn, gynecology, neurosurgery, urology, cardiac, general, oral/maxillofacial, orthopedic, plastic, pediatric, thoracic, transplant, trauma and vascular surgery and oncology surgical patients

29,924

0.41%

Hua 201216

Unplanned intubation

Requiring placement of an endotracheal tube secondary to the onset of respiratory or cardiac failure as evidenced by severe respiratory distress, hypoxia, hypercarbia or respiratory acidosis within 30 days of the operation

Major surgery, carotid endarterectomy, inguinal herniorrhaphy, parathyroidectomy, thyroidectomy, breast lumpectomy and endovascular abdominal aortic aneurysm repair surgical patients

231,548

2.20%

References:

1. Grosse-Sundrup M, Henneman JP, Sandberg WS, et al. Intermediate acting non-depolarizing neuromuscular blocking agents and risk of postoperative respiratory complications: prospective propensity score matched cohort study. BMJ. 2012;345:e6329. [ View Abstract ]

2. Bloom JD, Lu M, Sigl J, Hansell DM. Postoperative naloxone rescue following parenteral opioids after abdominal surgery: Incidence and cohort morbidity and mortality. Intensive Care Med.. 2010;36(Suppl 2):S283. [ View Abstract ]

3. Cashman JN, Dolin SJ. Respiratory and haemodynamic effects of acute postoperative pain management: evidence from published data. Br J Anaesth. 2004;93(2):212-223. [ View Abstract ]

4. Shapiro A, Zohar E, Zaslansky R, Hoppenstein D, Shabat S, Fredman B. The frequency and timing of respiratory depression in 1524 postoperative patients treated with systemic or neuraxial morphine. J Clin Anesth. 2005;17(7):537-542. [ View Abstract ]

5. Flisberg P, Rudin A, Linner R, Lundberg CJ. Pain relief and safety after major surgery. A prospective study of epidural and intravenous analgesia in 2696 patients. Acta Anaesthesiol Scand. 2003;47(4):457-465. [ View Abstract ]

6. Gupta PK, Gupta H, Natarajan B, et al. Postoperative respiratory failure after thyroid and parathyroid surgery: analysis of national surgical quality improvement program. Head Neck. 2012;34(3):321-327. [ View Abstract ]

7. Johnson RG, Arozullah AM, Neumayer L, Henderson WG, Hosokawa P, Khuri SF. Multivariable predictors of postoperative respiratory failure after general and vascular surgery: results from the patient safety in surgery study. J Am Coll Surg. 2007;204(6):1188-1198. [ View Abstract ]

8. Fischer JP, Shang EK, Butler CE, et al. Validated model for predicting postoperative respiratory failure: analysis of 1706 abdominal wall reconstructions. Plast Reconstr Surg. 2013;132(5):826e-835e. [ View Abstract ]

9. Bloom J, Agarwal S, Erslon M, Mestek M, Hansell D. Incidence and economic impact of and risk factors for respiratory failure after abdominal surgery. Surg Endosc. 2011;25:P441. [ View Abstract ]

10. Linde-Zwirble W, Bloom J, Mecca R, Hansell D. Postoperative pulmonary complications in adult elective surgery patients in the US: severity, outcomes and resources use. Crit Care. 2010;14 (Suppl 1):P210. [ View Abstract ]

11. Arozullah AM, Henderson WG, Khuri SF, Daley J. Postoperative mortality and pulmonary complication rankings: how well do they correlate at the hospital level? Med Care. 2003;41(8):979-991.
[ View Abstract ]

12. Agarwal S, Erslon M, Seda J, Kelley S. Large national database highlights significant risk factors for respiratory complications and mortality after abdominal surgery. Crit Care Med. 2011;39(Suppl 12):588. [ View Abstract ]

13. Kelley SD, Agarwal SJ, Erslon MG, Seda J, Lautz DB. Risk factors for respiratory insufficiency, arrest and failure among selected open and laparoscopic procedures - analysis of 90,000+ procedures. Surg Endosc. 2012;26(Suppl 1):P565. [ View Abstract ]

14. Ramachandran SK, Nafiu OO, Ghaferi A, Tremper KK, Shanks A, Kheterpal S. Independent predictors and outcomes of unanticipated early postoperative tracheal intubation after nonemergent, noncardiac surgery. Anesthesiology. 2011;115(1):44-53. [ View Abstract ]

15. Brueckmann B, Villa-Uribe JL, Bateman BT, et al. Development and validation of a score for prediction of postoperative respiratory complications. Anesthesiology. 2013;118(6):1276-1285.
[ View Abstract ]

16. Hua M, Brady JE, Li G. A scoring system to predict unplanned intubation in patients having undergone major surgical procedures. Anesth Analg. 2012;115(1):88-94. [ View Abstract ]

Outcomes

Respiratory compromise leads to a greater risk of mortality, longer length of stay and higher costs per patient.

Mortality (%) in respiratory failure (RF) cases vs. controls.

View Data
Hide Data
Cases
Control
Mortality %
30.00%
25.00%
20.00%
15.00%
10.00%
5.00%
Gupta 2012(1)- RF (p < 0.0001) Fischer 2013(2)- RF (p < 0.001) Ramachandran 2011(3)- RF (p < 0.001) Hua 2012(4)- RF (p < 0.0001)
15.66%
5.00%
14.70%
0.10%
15.00%
1.00%
28.10%
1.50%

Hospitalization length of stay (LOS) (D) in respiratory insufficiency, arrest and failure (RIAF) or respiratory failure (RF) cases vs. controls.

View Data
Hide Data
Agarwal 2011(6)- RIAF (p < 0.001)
Agarwal 2011(6)- RIAF (p < 0.001)
Fischer 2013(2)- RF (p < 0.001)
Bloom 2011(7)- RF (p < 0.0001)
Gupta 2012(1)- RF (p < 0.0001)
Gupta 2012(1)- RF (p < 0.0001)
Hospitalization Length of Stay (LOS)(D)
100
90
80
70
60
50
40
30
20
10
Cases Control
Cases Cases LOS Control LOS
Agarwal 2011(6)- RIAF (p < 0.001) 9.1 1.1
Agarwal 2011(6)- RIAF (p < 0.001) 16 8
Fischer 2013(2)- RF (p < 0.001) 17 6
Bloom 2011(7)- RF (p < 0.0001) 21 5.9
Gupta 2012(1)- RF (p < 0.0001) 17.2 8.3
Gupta 2012(1)- RF (p < 0.0001) 11.4 7.29
9.1
16
17
21
17.2
11.4
1.1
8
6
5.9
8.3
7.29

Hospitalization costs ($) in respiratory insufficiency, arrest and failure (RIAF) or respiratory failure (RF) cases vs. controls.

View Data
Hide Data
Kelley 2013(10)- RIAF (p < 0.001)
Kelley 2012(5)- RIAF (p < 0.001)
Agarwal 2011(6)- RIAF (p < 0.001)
Bloom 2011(7)- RF (p < 0.0001)
Bloom 2010(8)- RF (p < 0.001)
Hospitalization Costs ($)
200,000
180,000
160,000
140,000
120,000
100,000
80,000
60,000
40,000
20,000
Cases Control
Cases Cases Costs Control Costs
Kelley 2013(10)- RIAF (p < 0.001) $25,283 $12,291
Kelley 2012(5)- RIAF (p < 0.001) $24,578 $6,370
Agarwal 2011(6)- RIAF (p < 0.001) $48,487 $19,211
Bloom 2011(7)- RF (p < 0.0001) $48,775 $13,823
Bloom 2010(8)- RF (p < 0.001) $37,293 $18,971

References:

1. Gupta PK, Gupta H, Natarajan B, et al. Postoperative respiratory failure after thyroid and parathyroid surgery: analysis of national surgical quality improvement program. Head Neck. 2012;34(3):321-327. [ View Abstract ]

2. Fischer JP, Shang EK, Butler CE, et al. Validated model for predicting postoperative respiratory failure: analysis of 1706 abdominal wall reconstructions. Plast Reconstr Surg. 2013;132(5):826e-835e. [ View Abstract ]

3. Ramachandran SK, Nafiu OO, Ghaferi A, Tremper KK, Shanks A, Kheterpal S. Independent predictors and outcomes of unanticipated early postoperative tracheal intubation after nonemergent, noncardiac surgery. Anesthesiology. 2011;115(1):44-53. [ View Abstract ]

4. Hua M, Brady JE, Li G. A scoring system to predict unplanned intubation in patients having undergone major surgical procedures. Anesth Analgesia. 2012;115(1):88-94. [ View Abstract ]

5. Kelley SA, Agarwal S, Parikh N, Erslon M, Morris P. Respiratory insufficiency, arrest and failure among medical patients on the general care floor. Crit Care Med. 2012;40(12):764. [ View Abstract ]

6. Agarwal S, Erslon M, Seda J, Kelley S. Large national database highlights significant risk factors for respiratory complications and mortality after abdominal surgery. Crit Care Med. 2011;39(Suppl 12):588. [ View Abstract ]

7. Bloom J, Agarwal S, Erslon M, Mestek M, Hansell D. Incidence and economic impact of and risk factors for respiratory failure after abdominal surgery. Surg Endosc. 2011;25:P441. [ View Abstract ]

8. Bloom JD, Lu M, Sigl J, Hansell DM. Postoperative naloxone rescue following parenteral opioids after abdominal surgery: Incidence and cohort morbidity and mortality. Intensive Care Med. 2010;36(Suppl 2):S283. [ View Abstract ]

9. Kelley SA, Agarwal S, Parikh N, Erslon M, Morris P. Respiratory insufficiency, arrest and failure among medical patients on the general care floor. Crit Care Med. 2012;40(12):764. [ View Abstract ]

10. Kelley S, Kelly E, Hashemi L, Erslon M, Weinmann M. Clinical And Economic Burden Of Respiratory Insufficiency, Arrest And Failure Not Present On Admission In Patients With Sepsis. Am J Respir Crit Care Med. 2013;187(Meeting Abstracts):A5304. [ View Abstract ]

Respiratory Failure

The pathogenesis of respiratory failure or arrest is influenced by so many patient-specific comorbidities or clinical interventions acting synergistically that it is difficult to define a single causative factor for respiratory compromise The most common factors leading to respiratory failure can be categorized as contributing to one or more of three processes: pulmonary shunt[1], perioperative respiratory muscle dysfunction[2] or opioid-induced respiratory depression.[3]

Pulmonary Shunt

  • Pulmonary shunt is a principal clinical reason for hypoxemia so severe that it would result in respiratory failure. [1]
  • Pulmonary shunt results from diseases that cause either edema or collapse of alveoli. [1]
Table 1. Conditions that lead to edema or collapse of the alveoli.[1]
Pneumonia
Pulmonary edema
Trauma
Inflammatory diseases
Atelectasis
Airway obstruction

 

Respiratory muscle dysfunction

Multiple perioperative interventions and preoperative comorbidities negatively influence the upper airway muscles and respiratory pump muscles, predisposing patients for airway obstruction and respiratory pump muscle fatigue.[2]

 

Opioid-induced respiratory depression

It is well known that opioid administration is associated with risk for respiratory depression, which can lead to respiratory failure or death. The intensity and duration of the respiratory depressant effects of opioids are dependent on a number of factors, including:

  • The pharmacological characteristics and dose of the administered[4]
  • Intrinsic biological factors of the patient (age, gender, ethnicity, genetics) that influence the metabolism and clearance of opioids[5]
  • Patient comorbidities (sleep apnea, obesity) that increase risk for respiratory depression[3]
  • Co-administration of sedating medications that may potentiate opioid-induced respiratory depression[5],[6]

Lee et al [6] performed an analysis of the factors associated with respiratory depression closed claims. The table below summarizes their findings:

Table 2. Postoperative characteristics of respiratory depression claims.[6]
Factor % of Respiratory Depression Claims
Primary mode of pain therapy  
Neuraxial 42%
PCA 42%
Other* 15%
Multimodal pain therapy 51%

 

See more results

 

 

Timeline of postoperative respiratory failure

Patients are at the greatest risk for respiratory failure in the first 24 hours postoperatively

  • 75% of deaths related to critical respiratory events occur in the first 24 hours postoperatively[7]
  • 81% of critical respiratory events occur in the first 24 hours postoperatively[7]
  • 77% of naloxone reversal of postoperative narcotics for pain management occur in the first 24 hours postoperatively[8]

 

Risk factors for postoperative respiratory compromise

The pathogenesis of respiratory compromise is dynamic. Consequently, it is affected by numerous preoperative, intraoperative and postoperative risk factors often acting synergistically.

Multiple perioperative interventions and preoperative comorbidities negatively influence the upper airway muscles and respiratory pump muscles, predisposing patients for to airway obstruction and respiratory pump muscle fatigue.[2]

Preoperative   Intraoperative   Postoperative  
Risk Factor Odds Ratio Risk factor Odds Ratio Risk factor Odds Ratio
35-49 vs. < 35[9] 2.57 Crystalloid Adminstration in liters[13] 1.43 Higher Dose Opioids[15] 1.3
50-64 vs. <35[9] 3.95 Neuromuscular Blockade Administration[14] 1.4 Prolonged Hospitalization[10] 1.3
65-79 vs. <35 7.06 Median Drive Pressure[13] 1.17    
80+ vs <35[9] 9.76 Median FiO2[13] 1.02    

 

See more results

 

 

Environmental risk factors for respiratory compromise

Failure to prevent respiratory compromise events may be because of a detection error, which is a failure of early detection of an abnormality in the patient’s clinical condition. This may be especially prevalent in lower acuity settings where patients are only periodically assessed.[16]

  • A significant proportion of respiratory arrests happen in lower acuity settings, despite having lower risk patients.
Table 4. Location of acute respiratory compromise events. [17]
Location % of Total
Intensive care unit 35.1
General inpatient unit 26.8
Step-down unit 17.4
Emergency department 11.9
Other 9.1
  • Delayed interventions occur in 50% of patients with respiratory distress, with a median duration of delay of 12 hours.[18]
  • A delay in making an intervention is associated with an increase in mortality in patients with respiratory distress.[18]
  • In units where intermittent physiological monitoring is standard of care and nursing ratios vary from day to night, diurnal variation in interventions is much greater (63% greater during daytime) than in critical care units like the ICU where nurse ratios is maintained 24 hours a day (11% greater during nighttime)[16]

 

Poor respiration rate compliance

Multiple clinical trials have revealed that despite the potential for respiratory rate to be an early indicator of declining clinical state[20] [21] [22] [23], respiratory rate is the least commonly documented vital sign.[19]

Table 5. Studies investigating the proportion of missing respiratory rate recordings in medical records.
Citation Criteria Baseline Proportion of Missing Respiratory Rate Recordings
Butler-Williams 2005[25] Audit the recording of respiratory rate on patient observation charts throughout the hospital 92.97%
Chen 2009[19] Proportion of missing RR recordings in the 24 hours before an emergency team call 42%
Hodgetts 2002[20] Proportion of missing RR recording in 24 hours preceding cardiac arrest 73%
McBride 2005[26] Percentage of occupied ward beds where no respiratory rate recording had been made in a single 24-hour period 70.50%
McGain 2008[27] Proportion of missing RR recordings in retrospective audit of patient records 15.40%

References:

1. Raju P, Manthous CA. The pathogenesis of respiratory failure: an overview. Respir Care Clin N Am. 2000;6(2):195-212. [ View Abstract ]

2. Sasaki N, Meyer MJ, Eikermann M. Postoperative respiratory muscle dysfunction: pathophysiology and preventive strategies. Anesthesiology. 2013;118(4):961-978. [ View Abstract ]

3. Jarzyna D, Jungquist CR, Pasero C, et al. American Society for Pain Management Nursing guidelines on monitoring for opioid-induced sedation and respiratory depression. Pain Manag Nurs. 2011;12(3):118-145 [ View Abstract ]

4. Dahan A, Aarts L, Smith TW. Incidence, reversal, and prevention of opioid-induced respiratory depression. Anesthesiology. 2010;112(1):226-238. [ View Abstract ]

5. Koo C, Eikermann M. Respiratory effects of opioids in perioperative medicine. Open Anesthesia Journal. 2011;5(suppl 1-M6):23-34. [ View Abstract ]

6. Lee LA, Domino KB. Factors associated with postoperative respiratory depression: from the ASA closed claims analysis. ASA Newsletter. 2013;77(5):34-36. [ View Abstract ]

7. Ramachandran SK, Haider N, Saran KA, et al. Life-threatening critical respiratory events: a retrospective study of postoperative patients found unresponsive during analgesic therapy. Jf Clin Anesth. 2011;23(3):207-213. [ View Abstract ]

8. Taylor S, Kirton OC, Staff I, Kozol RA. Postoperative day one: a high risk period for respiratory events. Am J Surg. 2005;190(5):752-756. [ View Abstract ]

9. Kelley SD, Agarwal SJ, Erslon MG, Seda J, Lautz DB. Risk factors for respiratory insufficiency, arrest and failure among selected open and laparoscopic procedures - analysis of 90,000+ procedures. Surg Endosc. 2012;26(Suppl 1):P565. [ View Abstract ]

10. Ramachandran SK, Nafiu OO, Ghaferi A, Tremper KK, Shanks A, Kheterpal S. Independent predictors and outcomes of unanticipated early postoperative tracheal intubation after nonemergent, noncardiac surgery. Anesthesiology. 2011;115(1):44-53. [ View Abstract ]

11. Fischer JP, Shang EK, Butler CE, et al. Validated model for predicting postoperative respiratory failure: analysis of 1706 abdominal wall reconstructions. Plast Reconstr Surg. 2013;132(5):826e-835e. [ View Abstract ]

12. Agarwal S, Erslon M, Seda J, Kelley S. Large national database highlights significant risk factors for respiratory complications and mortality after abdominal surgery. Crit Care Med. 2011;39(Suppl 12):588. [ View Abstract ]

13. Blum JM, Stentz MJ, Dechert R, et al. Preoperative and intraoperative predictors of postoperative acute respiratory distress syndrome in a general surgical population. Anesthesiology. 2013;118(1):19-29. [ View Abstract ]

14. Grosse-Sundrup M, Henneman JP, Sandberg WS, et al. Intermediate acting non-depolarizing neuromuscular blocking agents and risk of postoperative respiratory complications: prospective propensity score matched cohort study. BMJ. 2012;345:e6329. [ View Abstract ]

15. Oderda GM, Said Q, Evans RS, et al. Opioid-related adverse drug events in surgical hospitalizations: impact on costs and length of stay. Ann Pharmacother. 2007;41(3):400-406. [ View Abstract ]

16. Galhotra S, DeVita MA, Simmons RL, Schmid A. Impact of patient monitoring on the diurnal pattern of medical emergency team activation. Crit Care Med. 2006;34(6):1700-1706. [ View Abstract ]

17. Wang HE, Abella BS, Callaway CW. Risk of cardiopulmonary arrest after acute respiratory compromise in hospitalized patients. Resuscitation. 2008;79(2):234-240. [ View Abstract ]

18. Quach JL, Downey AW, Haase M, Haase-Fielitz A, Jones D, Bellomo R. Characteristics and outcomes of patients receiving a medical emergency team review for respiratory distress or hypotension. J Crit Care. 2008;23(3):325-331. [ View Abstract ]

19. Chen J, Hillman K, Bellomo R, Flabouris A, Finfer S, Cretikos M. The impact of introducing medical emergency team system on the documentations of vital signs. Resuscitation. 2009;80(1):35-43.
[ View Abstract ]

20. Hodgetts TJ, Kenward G, Vlackonikolis I, et al. Incidence, location and reasons for avoidable in-hospital cardiac arrest in a district general hospital. Resuscitation. 2002;54(2):115-123.
[ View Abstract ]

21. Buist M, Bernard S, Nguyen TV, Moore G, Anderson J. Association between clinically abnormal observations and subsequent in-hospital mortality: a prospective study. Resuscitation. 2004;62(2):137-141. [ View Abstract ]

22. Cretikos M, Chen J, Hillman K, Bellomo R, Finfer S, Flabouris A. The objective medical emergency team activation criteria: a case-control study. Resuscitation. 2007;73(1):62-72. [ View Abstract ]

23. Cretikos MA, Bellomo R, Hillman K, Chen J, Finfer S, Flabouris A. Respiratory rate: the neglected vital sign. Med J Aust. 2008;188(11):657-659. [ View Abstract ]

24. Hogan J. Why don't nurses monitor the respiratory rates of patients? Br J Nurs. 2006;15(9):489-492. [ View Abstract ]

25. Butler-Williams C, Cantrill N, Maton S. Increasing staff awareness of respiratory rate significance. Nurs Times. 2005;101(27):35-37. [ View Abstract ]

26. McBride J, Knight D, Piper J, Smith GB. Long-term effect of introducing an early warning score on respiratory rate charting on general wards. Resuscitation. 2005;65(1):41-44. [ View Abstract ]

27. McGain F, Cretikos MA, Jones D, et al. Documentation of clinical review and vital signs after major surgery. Med J Aust. 2008;189(7):380-383. [ View Abstract ]

Early Intervention is Key

In-hospital adverse events are frequently preceded by deterioration of respiratory function. Given this context, vigilant and continuous monitoring of respiratory function (etCO2, respiratory rate, and SpO2) may provide clinicians with advanced notice of pending adverse events.

Deterioration of patient condition prior to adverse events has led several investigators to conclude that many in-hospital adverse events may be preventable.

  • Hodgetts et al reported that among the 118 in-hospital cardiac cases, 61.9% of arrests were potentially avoidable.[1]
  • Rates of survival to discharge, survival at 24 hours and favorable neurological outcomes were substantially lower during the night compared with day/evening.[2]

Consequently, many institutions have implemented medical emergency teams or rapid response teams (MET/RRT) to improve patient safety through early intervention.

  • MET/RRT research has demonstrated the potential of continuous monitoring to trigger early intervention to improve patient safety through the reduction of preventable adverse events.[3]

The precipitating causes for preventable in-hospital adverse events are often respiratory in nature.

  • Wang et al5 found that 65% of respiratory arrests progressed to cardiopulmonary arrest within 10 minutes.
  • In a series of 2,121 in-hospital cardiopulmonary arrests, Cooper et al6 found that 20% of events originated as primary RAs.

Table 2. Precipitating cause of in-hospital cardiac arrest.[2]

Precipitating cause% of Total
Respiratory depression61
Hypotension19.5
RD and hypotension19.5

 

In environments where intermittent physiological monitoring is standard of care, clinical instability proceeding respiratory arrest often goes unnoticed, resulting in poor outcomes.

  • Respiratory rate is the least commonly documented vital sign.[7]
  • Preceding clinical instability is evident in 39% of respiratory arrests, most commonly elevated respiratory rate or progressive hypoxia.[8]
  • Delayed interventions occur in 50% of patients with respiratory distress, with a median duration of delay of 12 hours.[9]
  • Delayed MET interventions are associated with an increase in mortality in patients with respiratory distress.[9]
  • 38% of respiratory distress MET calls result in hospital mortality.[9]
  • The principal reason for ICU recidivism is respiratory failure requiring reintubation and ventilation in 54.9% of patients.[10]

Given this context, vigilant and continuous monitoring of respiratory function (etCO2, respiratory rate, and SpO2) may provide clinicians with advance notice of pending adverse events in high risk patients.

  • Extremes of respiratory rate are symptoms indicative of the common precipitating causes of RIAF.
Table 3. Precipitating causes of respiratory compromise
Associated with bradypnea Associated with tachypnea
Anesthesia/sedation related Aspiration
Impaired brain function Atelectasis
CNS Depressant induced respiratory compromise Heart Failure
Obstructive sleep apnea Pneumonia
  Pneumo/hemothorax
  Pulmonary edema
  Pulmonary embolism

Several MET/RRT studies have demonstrated that respiratory rate is one of the most accurate independent predictor of adverse events.

Table 4. Independent predictor of adverse events
Citation Adverse event Event Odds Ratio
Buist 2004[11] Mortality RR < 6 14.4
Buist 2004[11] Mortality RR > 30 7.2
Buist 2004[11] Mortality Decrease of consciousness 6.4
Buist 2004[11] Mortality Loss of consciousness 6.4
Buist 2004[11] Mortality Hypotension 2.5
Buist 2004[11] Mortality SpO2 < 90 2.4
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) RR < 10 or > 25 3.22
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) Pulse rate > 110/min 2.03
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) High level of nursing care required 1.96
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 24 12
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 25 43.1
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 26 55.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 28 72.2
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 30 56.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 36 67.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR < 10 13.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 110 8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 120 11.5
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 130 9.6
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 140 10.4
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 40 1.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 45 1.9
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 50 0.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 90 6.4
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 85 11
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 80 20.6
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths Decrease in GCS 21

In environments where intermittent physiological monitoring is standard of care, clinical instability proceeding respiratory arrest often goes unnoticed, resulting in poor outcomes.

  • Respiratory rate is the least commonly documented vital sign.[7]
  • Preceding clinical instability is evident in 39% of respiratory arrests, most commonly elevated respiratory rate or progressive hypoxia.[8]
  • Delayed interventions occur in 50% of patients with respiratory distress, with a median duration of delay of 12 hours.[9]
  • Delayed MET interventions are associated with an increase in mortality in patients with respiratory distress.[9]
  • 38% of respiratory distress MET calls result in hospital mortality.[9]
  • The principal reason for ICU recidivism is respiratory failure requiring reintubation and ventilation in 54.9% of patients.[10]

Given this context, vigilant and continuous monitoring of respiratory function (etCO2, respiratory rate, and SpO2) may provide clinicians with advance notice of pending adverse events in high risk patients.

  • Extremes of respiratory rate are symptoms indicative of the common precipitating causes of RIAF.
Table 3. Precipitating causes of respiratory compromise
Associated with bradypnea Associated with tachypnea
Anesthesia/sedation related Aspiration
Impaired brain function Atelectasis
CNS Depressant induced respiratory compromise Heart Failure
Obstructive sleep apnea Pneumonia
  Pneumo/hemothorax
  Pulmonary edema
  Pulmonary embolism

Several MET/RRT studies have demonstrated that respiratory rate is one of the most accurate independent predictor of adverse events.

Table 4. Independent predictor of adverse events
Citation Adverse event Event Odds Ratio
Buist 2004[11] Mortality RR < 6 14.4
Buist 2004[11] Mortality RR > 30 7.2
Buist 2004[11] Mortality Decrease of consciousness 6.4
Buist 2004[11] Mortality Loss of consciousness 6.4
Buist 2004[11] Mortality Hypotension 2.5
Buist 2004[11] Mortality SpO2 < 90 2.4
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) RR < 10 or > 25 3.22
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) Pulse rate > 110/min 2.03
Chaboyer 2008[12] AEs (HI infection, sepsis, deep vein thrombosis, PE, MI) High level of nursing care required 1.96
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 24 12
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 25 43.1
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 26 55.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 28 72.2
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 30 56.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR > 36 67.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths RR < 10 13.7
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 110 8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 120 11.5
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 130 9.6
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR > 140 10.4
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 40 1.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 45 1.9
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths HR < 50 0.8
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 90 6.4
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 85 11
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths BP < 80 20.6
Creitikos 2007[13] Unexpected CA, unplanned ICU admission or unexpected Deaths Decrease in GCS 21

References:

1. Hodgetts TJ, Kenward G, Vlackonikolis I, et al. Incidence, location and reasons for avoidable in-hospital cardiac arrest in a district general hospital. Resuscitation. 2002;54(2):115-123.
[ View Abstract ]

2. Peberdy MA, Ornato JP, Larkin GL, et al. Survival from in-hospital cardiac arrest during nights and weekends. JAMA. 2008;299(7):785-792. [ View Abstract ]

3. Aneman A, Parr M. Medical emergency teams: a role for expanding intensive care? Acta Anaesthesiol Scand. 2006;50(10):1255-1265. [ View Abstract ]

4. Fecho K, Jackson F, Smith F, Overdyk FJ. In-hospital resuscitation: opioids and other factors influencing survival. Ther Clin Risk Manag. 2009;5:961-968. [ View Abstract ]

5. Wang HE, Abella BS, Callaway CW. Risk of cardiopulmonary arrest after acute respiratory compromise in hospitalized patients. Resuscitation. 2008;79(2):234-240. [ View Abstract ]

6. Cooper S, Janghorbani M, Cooper G. A decade of in-hospital resuscitation: outcomes and prediction of survival? Resuscitation. 2006;68(2):231-237. [ View Abstract ]

7. Chen J, Hillman K, Bellomo R, Flabouris A, Finfer S, Cretikos M. The impact of introducing medical emergency team system on the documentations of vital signs. Resuscitation. 2009;80(1):35-43.
[ View Abstract ]

8. Husband A, Mercer I, Detering KM, Eastwood GM, Jones DA. The epidemiology of respiratory arrests in a teaching hospital. Resuscitation. 2014;85(3):364-368. [ View Abstract ]

9. Quach JL, Downey AW, Haase M, Haase-Fielitz A, Jones D, Bellomo R. Characteristics and outcomes of patients receiving a medical emergency team review for respiratory distress or hypotension. J Crit Care. 2008;23(3):325-331. [ View Abstract ]

10. Vohra HA, Goldsmith IR, Rosin MD, Briffa NP, Patel RL. The predictors and outcome of recidivism in cardiac ICUs. Eur J Cardiothorac Surg. 2005;27(3):508-511. [ View Abstract ]

11. Buist M, Bernard S, Nguyen TV, Moore G, Anderson J. Association between clinically abnormal observations and subsequent in-hospital mortality: a prospective study. Resuscitation. 2004;62(2):137-141. [ View Abstract ]

12. Chaboyer W, Thalib L, Foster M, Ball C, Richards B. Predictors of adverse events in patients after discharge from the intensive care unit. Am J Crit Care. 2008;17(3):255-263. [ View Abstract ]

13. Cretikos M, Chen J, Hillman K, Bellomo R, Finfer S, Flabouris A. The objective medical emergency team activation criteria: a case-control study. Resuscitation. 2007;73(1):62-72. [ View Abstract ]

Guidelines

Several societies have recommended the use of continuous monitoring of respiratory function to detection or prevention of respiratory compromise.

Summary of patient monitoring recommendations in the published guidelines for the detection or prevention of respiratory compromise.

Recommendation ASA [1],[2] APSF[3] ASPMN[4] Joint Commission[5]
Continuous pulse oximetry for patients at risk for respiratory compromise x x x x
Continuous capnography for patients at risk for respiratory compromise   x x x
Continuous monitoring by telemetry may be utilized x x    

Comparison of available monitoring modalities for detection of opioid-induced respiratory depression in the postoperative period.

Monitoring Modality Sensitivity Specificity Reliability Response Time
PetCO2 (intubated) High High High Fast
SpO2 (no O2 supplement) High Moderate-high High Fast
PetCO2 (unintubated) High Moderate-high Moderate Fast
PaCO2 High High High Slow
PvCO2 High High High Slow
PtcCO2 High Moderate High Slow
SpO2 (with O2 supplement) Moderate Moderate High Slow
Clinical assessment (skilled clinician) Moderate Moderate-high Moderate Slow
Respiratory rate (newer technology Moderate Moderate Moderate Medium
Tidal volume (unintubated) Moderate Moderate Low Medium
Chest wall impedance via ECG (for respiratory. rate) Low-moderate Low Low Medium
Clinical assessment (less skilled clinician) Low-moderate Low-moderate Low-moderate Slow

ASA members survey results for postoperative management of patients with obstructive sleep apnea and neuraxial opioid administration.

Practice guidelines for the perioperative management of patients with obstructive sleep apnea [1]          
  Strongly agree Agree Equivocal Disagree Strongly disagree
Hospitalized patients who are at increased risk of respiratory compromise from OSA should have continuous pulse oximetry monitoring after discharge from the recovery room 56.9 33.7 10.5 2.2 0
Continuous monitoring should be maintained as long as patients remain at increased risk 64 29.2 4.5 1.9 0.4
Patients at increased perioperative risk from OSA should not be discharged from the recovery area to an unmonitored setting (i.e., home or unmonitored hospital bed) until they are no longer at risk of postoperative respiratory depression 51.7 33.3 10.9 3.7 0.4
To establish that patients are able to maintain adequate oxygen saturation levels while breathing room air, respiratory function may be determined by observing patients in an unstimulated environment, preferably while asleep 40.8 44.6 11.6 3

References:

1. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: an updated report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology. 2014;120(2):268-286. [ View Abstract ]

2. Horlocker TT, Burton AW, Connis RT, et al. Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration. Anesthesiology. 2009;110(2):218-230. [ View Abstract ]

3. APSF. Essential Monitoring Strategies to Detect Clinically Significant Drug-Induced Respiratory Depression in the Postoperative Period. Conclusions and Recommendations. http://www.apsf.org/announcements.php?id=7.;Accessed September 28, 2011. [ View Abstract ]

4. Jarzyna D, Jungquist CR, Pasero C, et al. American Society for Pain Management Nursing guidelines on monitoring for opioid-induced sedation and respiratory depression. Pain Manag Nurs. 2011;12(3):118-145 e110. [ View Abstract ]

5. Commission TJ. Safe use of opioids in hospitals. Sentinel Event Alert. 2012;849(8):1-5. [ View Abstract ]

6. Weinger M, Lee L. No Patient Shall Be Harmed By Opioid-Induced Respiratory Depression. APSF Newsletter. 2011;26(2):21-40. [ View Abstract ]

Continuous Monitoring Solutions

Respiratory Compromise Definitions

Respiratory compromise is an umbrella term for respiratory failure, respiratory arrest and respiratory insufficiency or depression.

Respiratory failure

Occurs when the exchange of oxygen does not meet metabolic needs, leading to hypoxemia with or without hypercapnia.[1]

Common precipitating causes of respiratory failure.[4]
Precipitating cause* % of precipitating cause
Pulmonary edema 51
Atelectasis 46
Pneumonia 28
Impaired brain function 24
Aspiration 22
Airway obstruction 14
Other 9
Anesthesia related 7
Hypotension 6
Prophylactic preventive measure 6
Myocardial infarction 5
Pulmonary embolism 5
Agitation 4
Pneumo/hemothorax 3
Cardiac Arrest 2

 

*On an average 2.3 reasons for respiratory failure were reported per patient.

Clinical definitions of respiratory failure in the literature
Definition Source
PaO2/FiO2 <= 300 mmHg Canet 2014[1]
Unplanned intubation during surgery or postoperatively, reintubation once extubated or mechanical ventilation for more than 48 hours postoperatively American College of Surgeons National Surgical Quality Improvement Program[2]

 

Most common procedures for patients who develop post-operative respiratory failure.[3]
Procedure % of PRF Cases
Upper abdominal 31
Thoracic 19
Peripheral vascular 14
Extremity 9
AAA repair 8
Lower abdominal 6
Neurosurgery 4
Back and spine 3
Neck 3
Dermatologic 2
Eye, nose, mouth, other 1

Respiratory arrest

Is defined by sudden complete cessation of respiratory movement.[5]

Clinical definitions of respiratory arrest in the literature.
Definition Source
Event in which a patient became apneic or developed profound hypoventilation requiring manual ventilation with a non re-breathing ventilator bag or immediate endotracheal intubation and in which cardiac output was maintained. Husband 2013[6]
Patients experiencing acute respiratory compromise, requiring emergency-assisted ventilation and triggering either a hospital-wide or unit-based emergency response by acute care facility personnel Wang 2008[7]

 

Most common admission diagnostic groups for patients who develop respiratory arrest.[6]
Procedure % of RA Cases
Elective surgery 12.7
Malignancy 12.7
Lower respiratory tract infection 11.4
Stroke 10.1
Cardiac 8.9
Neuromuscular 5.1
Spinal injury/trauma 5.1
Asthma/COPD 3.8
Nonmalignant large airway compromise 3.8
Other 26.6

 

Common precipitating causes of respiratory arrest. [6]
Precipitating cause* % of precipitating cause
Pulmonary edema 25.6
Aspiration 18.3
Uncertain 17.1
Intracranial 14.6
Medication side-effect 14.6
Tracheostomy complication 12.2
Seizure 8.5
Shock 8.5
Sputum plugging 8.5
Bronchospasm 7.3
Bronchospasm 7.3
Airway obstruction 4.9
Neuromuscular 3.7
Pulmonary embolism 3.7

 

*Multiple causes attribute to some respiratory arrests.

Respiratory insufficiency or depression

Is a condition in which respiratory function is inadequate to meet the body’s needs. If the condition is not successfully managed it may progress to respiratory failure.[5]

Clinical definitions of respiratory insufficiency or depression in the literature.
Definition Source
RR < 8 Filsberg 2003[8]
PCO2 > 50 mmHg or RR <8 Gwirtz 1999[9]
RR < 10 or SpO2 < 90 or PC O2 > 7 kPa Tsui 1997[10]

References:

1. Canet J, Gallart L. Postoperative respiratory failure: pathogenesis, prediction, and prevention. Curr Opin Anaesthesiol. 2014;20(1):56-62. [ View Abstract ]

2. Gupta PK, Gupta H, Natarajan B, et al. Postoperative respiratory failure after thyroid and parathyroid surgery: analysis of national surgical quality improvement program. Head Neck. 2012;34(3):321-327. [ View Abstract ]

3. Arozullah AM, Daley J, Henderson WG, Khuri SF. Multifactorial risk index for predicting postoperative respiratory failure in men after major noncardiac surgery. The National Veterans Administration Surgical Quality Improvement Program. Ann Surg. 2000;232(2):242-253. [ View Abstract ]

4. Brueckmann B, Villa-Uribe JL, Bateman BT, et al. Development and validation of a score for prediction of postoperative respiratory complications. Anesthesiology. 2013;118(6):1276-1285.
[ View Abstract ]

5. Farlex. www.medical-dictionary.thefreedictionary.com. 2001. Medical Dictionary.

6. Husband A, Mercer I, Detering KM, Eastwood GM, Jones DA. The epidemiology of respiratory arrests in a teaching hospital. Resuscitation. 2014;85(3):364-368. [ View Abstract ]

7. Wang HE, Abella BS, Callaway CW. Risk of cardiopulmonary arrest after acute respiratory compromise in hospitalized patients. Resuscitation. 2008;79(2):234-240. [ View Abstract ]

8. Flisberg P, Rudin A, Linner R, Lundberg CJ. Pain relief and safety after major surgery. A prospective study of epidural and intravenous analgesia in 2696 patients. Acta Anaesthesiol Scand. 2003;47(4):457-465. [ View Abstract ]

9. Gwirtz KH, Young JV, Byers RS, et al. The safety and efficacy of intrathecal opioid analgesia for acute postoperative pain: seven years' experience with 5969 surgical patients at Indiana University Hospital. Anesth Analg. 1999;88(3):599-604. [ View Abstract ]

10. Tsui SL, Irwin MG, Wong CM, et al. An audit of the safety of an acute pain service. Anaesthesia. 1997;52(11):1042-1047. [ View Abstract ]