Respiratory muscle activity and respiratory obstruction after abdominal surgery

EVALUATION OF FUNCTIONAL CONDITION OF RESPIRATORY MUSCLES OF PATIENTS WITH A COMPLICATED BRONCHIAL ASTHMA PATHOLOGY AND CHRONIC OBSTRUCTIVE PULMONARY DISEASES

The aim of the research was to study the functional state of respiratory muscles and neuro-respiratory drive in patients with a combined pathology of bronchial asthma and chronic obstructive pulmonary disease. The functional condition of the respiratory muscles and the tone of the respiratory centre were determined with the help of a device for occlusion spirometry. Also, the patient was observed with a spirometry, a general plethysmography of the body. Materials and methods. 140 patients with combined broncho-obstructive pathology, 34 patients with asthma and 17 patients with COPD were examined. Spirometry, general plethysmography of the body and occlusion spirometry were provided for all patients. Results show a decrease in muscle strength of breath in all categories of patients with broncho-obstructive diseases, especially expressed in patients with bronchial asthma and asthma-COPD intersection. The muscle strength of breath was maintained with a significant increase in COPD patients compared with those with bronchial asthma. With increasing broncho-obstruction in patients with asthma-COPD intersection, there was a progressive and reliable decrease in muscle strength for breath and expiration, as well as a tendency to increase neuron respiratory drive. In patients with asthma-COPD intersection with more expressed symptoms revealed a significant and reliable weakening of muscle strength for breath and increased neuro-respiratory drive. During the work were obtained reliable links of the parameters of respiratory muscle strength not only with the parameters of pulmonary volume and bronchial patency, but also with the degree of neutrophilic inflammation in this category of patients. Conclusions The obtained data on failure of the functional state of the respiratory muscles and the neuro-respiratory drive can be used in the development of rehabilitation programs for the management of patients with combined broncho-obstructive pathology.

Correlation between intra-abdominal pressure and pulmonary volumes after superior and inferior abdominal surgery

OBJECTIVE

Patients undergoing abdominal surgery are at risk for pulmonary complications. The principal cause of postoperative pulmonary complications is a significant reduction in pulmonary volumes (FEV1 and FVC) to approximately 65-70% of the predicted value. Another frequent occurrence after abdominal surgery is increased intra-abdominal pressure. The aim of this study was to correlate changes in pulmonary volumes with the values of intra-abdominal pressure after abdominal surgery, according to the surgical incision in the abdomen (superior or inferior).

METHODS

We prospectively evaluated 60 patients who underwent elective open abdominal surgery with a surgical time greater than 240 minutes. Patients were evaluated before surgery and on the 3rd postoperative day. Spirometry was assessed by maximal respiratory maneuvers and flow-volume curves. Intra-abdominal pressure was measured in the postoperative period using the bladder technique.

RESULTS

The mean age of the patients was 56 ± 13 years, and 41.6% 25 were female; 50 patients (83.3%) had malignant disease. The patients were divided into two groups according to the surgical incision (superior or inferior). The lung volumes in the preoperative period showed no abnormalities. After surgery, there was a significant reduction in both FEV1 (1.6 ± 0.6 L) and FVC (2.0 ± 0.7 L) with maintenance of FEV1/FVC of 0.8 ± 0.2 in both groups. The maximum intra-abdominal pressure values were similar (p=0.59) for the two groups. There was no association between pulmonary volumes and intra-abdominal pressure measured in any of the groups analyzed.

CONCLUSIONS

Our results show that superior and inferior abdominal surgery determines hypoventilation, unrelated to increased intra-abdominal pressure. Patients at high risk of pulmonary complications should receive respiratory care even if undergoing inferior abdominal surgery.

Postoperative Respiratory Muscle Dysfunction

Postoperative pulmonary complications are responsible for significant increases in hospital cost as well as patient morbidity and mortality; respiratory muscle dysfunction represents a contributing factor. Upper airway dilator muscles functionally resist the upper airway collapsing forces created by the respiratory pump muscles. Standard perioperative medications (anesthetics, sedatives, opioids, and neuromuscular blocking agents), interventions (patient positioning, mechanical ventilation, and surgical trauma), and diseases (lung hyperinflation, obesity, and obstructive sleep apnea) have differential effects on the respiratory muscle subgroups. These effects on the upper airway dilators and respiratory pump muscles impair their coordination and function and can result in respiratory failure. Perioperative management strategies can help decrease the incidence of postoperative respiratory muscle dysfunction. Such strategies include minimally invasive procedures rather than open surgery, early and optimal mobilizing of respiratory muscles while on mechanical ventilation, judicious use of respiratory depressant anesthetics and neuromuscular blocking agents, and noninvasive ventilation when possible.

Pulmonary function and physical performance outcomes with preoperative physical therapy in upper abdominal surgery: a randomized controlled trial

OBJECTIVE

Investigation of the effects of preoperative physical therapy on pulmonary function and physical performance before and after upper abdominal surgery.

DESIGN

Non-blind randomized controlled trial.

SETTING

Tertiary public hospital and private university, São Paulo state, Brazil.

SUBJECTS

Thirty-two patients undergoing abdominal surgery.

INTERVENTIONS

Patients were randomly assigned to receive physical therapy, with respiratory and global exercises, 2-3 weeks before surgery (treatment group; n = 16) or await operation without engaging in practicing (control group; n = 16). After surgery, a physical therapy protocol was administered to all subjects until the seventh postoperative day.

MAIN MEASURES

Pulmonary function outcome variables were inspiratory and expiratory strength, respiratory muscle endurance and spirometry, and physical performance outcome variables were the functional independence measure and 6-minute walk test distance. Any postoperative pulmonary complications were recorded.

RESULTS

There were no between-group differences at randomization. In the preoperative period, patients in the intervention group had higher inspiratory strength and respiratory muscle endurance than controls (88 cmH(2)O versus 64 cmH(2)O and 28 cmH(2)O versus 23 cmH(2)O, respectively; P <0 0.05). On the seventh postoperative day, in addition to inspiratory force and respiratory muscle endurance, the intervention group showed better results than controls in the functional independence measure score (118 versus 95) and 6-minute walk test distance (368.5 m versus 223 m), all P <0 0.05. Postoperative pulmonary complications occurred in 11 patients in the control group and five in the intervention group (P = 0.03).

CONCLUSION

Preoperative physical therapy improved pulmonary function and physical performance in the pre- and postoperative periods among patients undergoing upper abdominal surgery.

Assessment of physical fitness for esophageal surgery, and targeting interventions to optimize outcomes

This review examines how higher levels of physiological reserve and fitness can help the patient endure the demands of esophageal surgery. Lung function, body composition, cardiac function, inflammatory mediators and exercise performance are all determinants of fitness. Physical fitness, both as an independent risk factor and through its effect on other risk factors, has been found to be significantly associated with the risk of developing postoperative pulmonary complications (PPCs) in patients following esophagectomy. Respiratory dysfunction preoperatively poses the dominant risk of developing complications, and PPCs are the most common causes of morbidity and mortality. The incidence of PPCs is between 15 and 40% with an associated 4.5-fold increase in operative mortality leading to approximately 45% of all deaths post-esophagectomy. Cardiac complications are the other principal postoperative complications, and pulmonary and cardiac complications are reported to account for up to 70% of postoperative deaths after esophagectomy. Risk reduction in patients planned for surgery is key in attaining optimal outcomes. The goal of this review was to discuss the risk factors associated with the development of postoperative pulmonary complications and how these may be modified prior to surgery with a specific focus on the pulmonary complications associated with esophageal resection. There are few studies that have examined the effect of modifying physical fitness pre-esophageal surgery. The data to date would indicate a need to develop targeted interventions preoperatively to increase physical function with the aim of decreasing postoperative complications.

Low-frequency changes in finger volume in patients after surgery, related to respiration and venous pressure

BACKGROUND AND OBJECTIVE

In patients after surgery, we observed large-amplitude low-frequency changes in digital plethysmograph measurements when DC coupling of the signal was used. We set out to assess factors that might contribute to these events and in particular to test the possibility that low-frequency signals could be used to assess respiratory disturbances.

METHODS

We recorded values in 23 patients who had undergone gynaecological surgery. We measured nasal flow, abdominal pressure (by urinary catheter), venous pressure in the hand, and DC-coupled optical transmission plethysmography. Signals were replayed and analysed to assess the incidence of specific patterns of events.

RESULTS

Most patients received morphine for postoperative analgesia. Respiratory irregularity and expiratory muscle action were very frequent. Increases in abdominal pressure during expiration caused increases in venous pressure and pulsation. In 12 out of 23 patients, a characteristic response consistent with vasoconstriction was noted after increases in breath size, and, in seven patients, very-low-frequency (0.2-0.7 Hz) oscillations of finger volume were present that appeared unrelated to respiratory events. Patients who did not receive morphine had very different plethysmograph patterns, with significantly smaller pulse amplitude.

CONCLUSION

Low-frequency changes in finger volume can be simply obtained and provide considerable information about peripheral circulatory dynamics. Diverse patterns can be recognized, but the range of responses suggests that current techniques cannot be used alone to assess cardiorespiratory status. However, a combination of plethysmography with respiratory measurements shows characteristic events.

Preoperative Assessment for Obstructive Sleep Apnoea and the Prediction of Postoperative Respiratory Obstruction and Hypoxaemia

Patients scheduled for elective surgery requiring general anaesthesia and hospital admission were assessed for risk of obstructive sleep apnoea (OSA) using history, body mass index and upper airway examination to determine any relation between OSA risk and the rate of respiratory events after surgery. Anaesthesia and postoperative analgesia were at the discretion of the treating anaesthetist, who was made aware of any suspicion of OSA. Respiratory monitoring for apnoeas (central or obstructive), hypopnoeas and oxygen desaturations was continuous for a 12-hour period on the first postoperative night. We used automated analysis and visual scanning of respiratory recordings, but sleep stages were not assessed. Patients classified as OSA risk had more respiratory obstructive events per hour than controls (38±22 vs. 14±10) and an increased proportion of the 12-hour monitored period with oxygen saturation <90% (7±12% vs. 2±5% of the 12-hour period). Perioperative morphine dose was predictive of central apnoeas for both OSA risk and control patients (P=0.002). This study suggests that preoperative suspicion of OSA should lead to increased postoperative monitoring and efforts to minimise sedation and opioid dose. It also supports the routine use of supplemental oxygen with patient-controlled opioid analgesia.

Differential activation among five human inspiratory motoneuron pools during tidal breathing

Neural drive to inspiratory pump muscles is increased under many pathological conditions. This study determined for the first time how neural drive is distributed to five different human inspiratory pump muscles during tidal breathing. The discharge of single motor units (n = 280) from five healthy subjects in the diaphragm, scalene, second parasternal intercostal, third dorsal external intercostal, and fifth dorsal external intercostal was recorded with needle electrodes. All units increased their discharge during inspiration, but 41 (15%) discharged tonically throughout expiration. Motor unit populations from each muscle differed in the timing of their activation and in the discharge rates of their motor units. Relative to the onset of inspiratory flow, the earliest recruited muscles were the diaphragm and third dorsal external intercostal (mean onset for the population after 26 and 29% of inspiratory time). The fifth dorsal external intercostal muscle was recruited later (43% of inspiratory time; P < 0.05). Compared with the other inspiratory muscles, units in the diaphragm and third dorsal external intercostal had the highest onset (7.7 and 7.1 Hz, respectively) and peak firing frequencies (12.6 and 11.9 Hz, respectively; both P < 0.05). There was a unimodal distribution of recruitment times of motor units in all muscles. Neural drive to human inspiratory pump muscles differs in timing, strength, and distribution, presumably to achieve efficient ventilation.