Impaired pulmonary function is common in cardiac patients (Shnkman et al., 1997Shnkman et al., 1997). Respiratory muscle wasting has been well documented in mitral stenosis (Saxena et al., 2007Saxena et al., 2007). Furthermore, it was found that pulmonary impairment is more frequent after cardiac surgery than after other major surgical procedures (Bund et al., 1998Bund et al., 1998). Deterioration in pulmonary function is a common complication following CABG surgery and there is still speculation to the precise causative factors thereof (Kleinloog and McFarlane, 2007Kleinloog and McFarlane, 2007).

The current study aimed to assess the PFTs of cardiac patient; with ischemic or rheumatic heart diseases as well as patients who underwent CABG or valvular procedures. The main objective of this study is to describe the pattern of pulmonary function complications and to critically appraise the possible causative factors.

This study was conducted at the Cardiothoracic Surgery Department of the educational hospital of Cairo University. Forty volunteer patients participated in this study; 18 females (45%) and 22 males (55%) with mean age of (44.0 ± 15.8 years). Patients with rheumatic heart disease (RHD) were 21 (52.5%) while patients with ischemic heart disease (IHD) were 19 (47.5%). They were scheduled for cardiac surgery, valvular and CABG, respectively.

Volunteer patients, who met the inclusion criteria, signed a consent form after they got a clear explanation of the spirometry evaluation procedures. Inclusion criteria included; adult cardiac patient with valvular or ischemic heart disease scheduled for primary cardiac surgery, long life non-smokers or those who quit smoking, had no learning barriers to follow the instructions required to carry out the spirometry test, and were free from diabetes mellitus or neurological disorders and were not diagnosed as respiratory diseased patients. Data collection sheet was used to gather personal, medical and surgical information.

Table 1Table 1 presented characteristics of the 40 participated patients. It showed that RHD patients are mostly young females (mean age of 32.2 ± 11.2 years) who lived in rural areas and were long life non-smokers. While patients with IHD were older males (mean age of 57.0 ± 8.1 years) who lived in urban areas and quitted smoking before hospital admission by 1 month to 2 years.

Even before surgery, rheumatic and ischemic cardiac patients had below normal values of PFTs of restrictive pattern and it was noticeable that patients with RHD had lower values than patients with IHD (Table 2Table 2).

Results also showed that cardiac surgery was followed by pulmonary complications in the form of further deterioration on PFTs. This negative impact on pulmonary function was true for both valvular and CABG surgeries. Regardless of the surgery type, patients had lower values of PFTs after the surgery than before it. Those lower values were of statistical significance for all PFTs for both valvular and CABG surgeries. The only exception was FEV1/FVC test, which increased after valvular surgery and lowered after CABG surgery without statistical significance (Fig. 1Fig. 1a and b).

Figure 1

Before and after valvular and CABG surgeries mean values of pulmonary function tests.

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In addition, results showed that patients who underwent valvular surgery had significant lower values of PFTs than patients who underwent CABG surgery. This was applied for the following tests, VC, FVC, FEV1, and MVV (P values were 0.043, 0.011, 0.040, and 0.020, respectively). FEV1/FVC parameter was lower in patients who underwent valvular surgery than those who underwent CABG but without statistical significance (Fig. 2Fig. 2).

Figure 2

After valvular and CABG surgeries mean values of pulmonary function tests.

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Analysis of the intra-operative data (Table 1Table 1) showed that in valvular surgery, the cardiac ischemic time and cardiopulmonary bypass time were longer than those of the CABG surgery but without significance difference. On the other hand, patient’s core body temperature in valvular surgery was significantly lower than that in patients with CABG surgery (29.2 ± 2.8 and 33.8 ± 1.1, respectively, P < 0.0001). Cold cardioplegia was used in most of the valvular surgeries (66.7%) while in the majority of the CABG surgeries (94.7%) warm cardioplegia was used. In valvular surgery, ice slush was usually used as a topical cooling (38.1%) but in the CABG surgery, it was common not to use any topical cooling modality (94.7%). Although there were different intra-operative situations among the valvular and CABG surgeries, there was no correlative relation between any of the studied intra-operative factors and PFTs values after the surgery. The only exception for that is the negative significant correlation between cardiac ischemic time and FEV1/FVC test (Table 3Table 3).

The correlations between patients’ age and their PFTs after cardiac surgery were significantly positive. The older the patient, the better the values of all PFTs except for FEV1/FVC test. The other demographic characters showed no correlation (Table 4Table 4).

This study was accomplished to describe the PFTs complications accompanying cardiac disease and cardiac surgery and to detect the underlying causative factors. Spirometry test had been used as it is an objective, valid and reliable method to measure the PFTs. In addition, it is a non-invasive method that can be handled without any inconvenience to the patient especially after surgery. Chandra et al., 1998, Blonshine and Fink, 2000, Handojo et al., 2006) agreed with that.

The below normal PFTs values shown before cardiac surgery were similar to Saxena et al. (2007))Saxena et al. (2007) study’s results. They found that FVC, FEV1, and peak expiratory flow rates were universally decreased before surgery in patients with mitral valve disease. Weissman (1999))Weissman (1999) also had similar results. It was noticeable that patients with RHD showed lower values than patients with IHD. This could be explained pathologically by the fact that patients with RHD are more common to develop left ventricular dysfunction with consequent pulmonary oedema in which the lung compliance is reduced and the resistance to air flow is increased with the resultant decreased gas exchange and decreased pulmonary function. The decreased pulmonary function was obviously represented with the spirometry test. The restrictive pattern of this decreased pulmonary function predominates this explanation. Saxena et al. (2007))Saxena et al. (2007) had a close explanation as they reported that mitral valve disease has important effects on the pulmonary vasculature. Pulmonary hypertension in these patients usually results from a combination of transmission of raised left atrial pressure, pulmonary arteriolar constriction and organic obliterate changes in the pulmonary vasculature. Pulmonary dysfunction is attributed to interstitial and alveolar oedema, reactive fibrosis, previous pulmonary infarctions, pleural effusion and decreased lung volumes with compressive atelectasis. These changes cause a marked reduction in lung compliance, an increase in the work of breathing and a redistribution of pulmonary blood flow from the bases to apices.

Cardiac surgeries are proved to have a negative impact on pulmonary function. All studied tests; VC, FVC, FEV1, FEV1/FVC, and MVV had lower values after the surgery than before it. This was true for both valvular and CABG procedures. Again, the pattern was a restrictive one. These results are supported by other studies’ results (Shnkman et al., 1997, Saxena et al., 2007, Weissman, 1999, Stenseth et al., 1996, Vaidya et al., 1996). The case of lower PFTs values of the RHD patients than the IHD remained the same after the surgery. Patients who underwent valvular surgery had lower PFTs values than patients who underwent CABG. This seemed logic; as long the earlier values (before surgery) were lower, the later ones (after surgery) would be also lowered. Further, it could be important to mention that most of the valvular surgery patients were females while most of the CABG patients were males. If it is remembered that females have lower PFTs values than males and they may react to pain worse than males it could be a way to understand why patients in the current study who underwent valvular surgery had lower pulmonary function than patients who underwent CABG. Nevertheless, were there any other factors that make valvular surgery more susceptible to lower PFTs values rather than the lower before surgery values? This question had been approached by comparing the intra-operative factors of valvular and CABG surgeries. As showed in Table 1Table 1, the cardiac ischemic time and cardiopulmonary bypass time were longer in patients who underwent valvular surgery than that of patients who underwent CABG but without a significant difference. However, let us not forget that literature demonstrated the cardiopulmonary bypass as one of the most accused factor. This is partly because of the inflammatory response (Mahmoud et al., 2005Mahmoud et al., 2005) it produces in the pulmonary system and consequent pulmonary dysfunction and partly because it causes changes in the mechanical behaviour of the lung that are generally consistent with those caused by pulmonary oedema (Barnas et al., 1994Barnas et al., 1994). In addition to the poor pulmonary gas exchange it produces after surgery (Kochamba et al., 2000Kochamba et al., 2000). Chandra et al. (1998))Chandra et al. (1998) found a significant deterioration in the pre discharge spirometric values of FVC, FEV1, peak expiratory flow rate, flow rate at 25–75% of expired vital capacity, and MVV, which was greater in those who had prolonged cardiopulmonary bypass time (more than 80 min). That is why although the current study showed no significant difference in cardiopulmonary bypass time between the valvular and CABG surgeries and no correlation between cardiopulmonary bypass time and the PFTs, this factor should not be completely acquitted and more studies are needed to give a final decision.

Current study showed that in most of the valvular surgeries (66.7%) cold cardioplegia had been used with ice slush as a topical cooling. On the other side, patients who underwent CABG had mostly used warm cardioplegia (94.7%) without the use of any topical cooling. This may be claimed to be the cause of lower PFTs with valvular surgery and specially mentioned by Saxena et al. (2007))Saxena et al. (2007) that cardioplegia is a factor that may contribute to the deteriorated pulmonary function after cardiac surgery as it may passively enter the pulmonary circulation and damage the endothelial cells in the lungs due to high potassium concentration and result in atelectasis. But the correlative analysis to the PFTs and the above mentioned intra-operative factors; cardioplegia, topical cooling and core body temperature were not significant. Kleinloog and McFarlane (2007))Kleinloog and McFarlane (2007)) supported these results as they found that cold blood cardioplegia solution, which circulates in the lungs during cardiopulmonary bypass does not have any (beneficial or detrimental) effect on clinical pulmonary function after surgery. One of the current study limitations is lack in investigating the correlation between atelectasis and PFTs, which would give clearer picture of pulmonary complications after cardiac surgery.

Patients who underwent valvular surgery had significant lower core body temperature than patients who underwent CABG. The effect of this factor on the lower PFTs values after cardiac surgery can be explained by the fact that low body temperature decreases the metabolism and functions of different body organs and systems so it could also be applied on the pulmonary system.

Studying the patient’s demographic characteristics was another trial to explain why cardiac surgeries had a deteriorating effect on pulmonary function. There was only positive correlation between the patient’s age and PFTs. The younger the patient was, the lower the PFTs values. The strangeness of this result would disappear when it is remembered that the pulmonary function of patients who underwent valvular surgeries, who were younger than patients who underwent CABG, were of lower values.

Arabaci et al. (2003))Arabaci et al. (2003) found that after surgery PFTs values decreased significantly in smokers and non-smokers patients but the deterioration in the smoker group was highly significant. In their study, patients in both groups developed a severe restrictive pulmonary defect after coronary artery surgery (P < 0.0001 for both), but this restriction was also statistically significant in the smoking group compared to non-smokers after surgery. They applied comparison t-test between the smokers and non-smokers but did not correlate the factor of smoking habit with the pulmonary function as had been done in the current study.

Since the examined intra-operative factors were not strong enough to establish a direct correlative association with the pulmonary function after cardiac surgery, and studying patient’s demographic characteristics did not add any further clarity of the case, the only remaining factor is the mechanical theory. Just approach the thoracic cage with the median sternotomy, the mechanics of respiration will definitely be altered and the pulmonary function of the lungs will be negatively affected. A proof of this theory is the restrictive pattern of pulmonary function after surgery. Another proof is the fact that most of cardiac surgery patients had atelectasis in the chest radiographs after the surgery and this is applied to both CABG and valvular surgeries. That is why Weissman (2004))Weissman (2004) stated that the high incidence of pulmonary complications is partly due to the disruption of normal pulmonary function that is inherent to surgery in the thoracic region. Adaptation of mechanical theory could be succeeded to rationale the decreased PFTs after cardiac surgery, but it could not justify why valvular surgery was complicated with lower PFTs than CABG surgery especially as median sternotomy was practiced in both surgeries?

In addition, it is well known that patients after surgery are common to have incisional chest pain that will interfere with the ability of the chest to expand and automatically result in low pulmonary function of restrictive pattern. That is why when Tenenbein et al. (2008))Tenenbein et al. (2008) compared between two groups of patients who had underwent CABG, they recorded that the group that used high epidural anaesthesia had lower pain and higher pulmonary function than the controlled group with the traditional analgesia morphine in the first few days after surgery. Not rating chest pain after the surgery was one of the limitations of the present study. It would be helpful to study the relation between pain after surgery, by using the visual analogue scale and the pulmonary function. The authors also believe that another limitation is the neglection of patients’ anaesthesia data, which could be precious information to give an explanation to the results of the study. This is especially because the effect of anaesthesia is well documented in many other studies and it could be the guilty reason of decreased pulmonary function after cardiac surgery or at least an adjunct factor with the mechanical one. It could be said that pulmonary complication after cardiac surgery is a multifactorial phenomenon and that statistical treatment of those suspicious factors with multivariate approach would be more practicable and would provide a rational valid explanation to that phenomenon.

It was concluded that rheumatic and ischemic cardiac diseases as well as valvular and CABG cardiac surgeries result in low PFTs values of restrictive pattern. It was documented that valvular surgery patients had lower PFTs values than CABG surgery patients. No definite causative factor appeared to be responsible for those results although mechanical deficiency and incisional chest pain caused by cardiac surgery are doubtful. More comprehensive investigation is required to resolve the case.